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Purpose Intolerance is the most common reason for kinase inhibitor (KI) discontinuation in CLL. Umbralisib a novel, highly selective PI3Kδ/CK1e inhibitor, is active and well tolerated in CLL patients. This phase 2 trial evaluated umbralisib in CLL patients who are intolerant to prior BTK or PI3K inhibitor therapy. Patients and methods In this phase 2 trial (NCT02742090), umbralisib was initiated at 800 mg oral daily in CLL patients requiring therapy per investigator discretion who were intolerant to prior BTK or PI3K inhibitor therapy, until progression or toxicity. Primary endpoint was progression-free survival (PFS). Secondary endpoints included time to treatment failure and umbralisib safety profile. DNA isolated from buccal swabs was genotyped for polymorphisms in CYP3A4, CYP3A5 and CYP2D6. Results Fifty-one patients were enrolled (44 BTKi and 7 PI3Kδi intolerant). Median age was 70 years (range 48-96), median of 2 prior lines of therapy (1-7), 24% had del17p and/or TP53 mutation, and 65% were IGHV unmutated. Most common AEs leading to prior KI discontinuation were rash (27%), arthralgia (18%), and atrial fibrillation (16%). Median progression free survival (PFS) was 23.5 months (95% CI 13.1-not estimable). 58% of patients were on umbralisib for a longer duration than prior KI. Most common (≥5%) grade ≥3 AEs on umbralisib (all causality) were neutropenia (18%), leukocytosis (14%), thrombocytopenia (12%), pneumonia (12%), and diarrhea (8%). Six patients (12%) discontinued umbralisib due to an AE. Eight patients (16%) had dose reductions and were successfully re-challenged. Conclusions Umbralisib is safe and effective in this BTK and alternate PI3K inhibitor intolerant CLL population. These are the first prospective data to confirm that switching from a BTK or alternate PI3K inhibitor to umbralisib can result in durable, well tolerated responses.

von Willebrand factor (VWF) is an essential hemostatic protein that is synthesized in endothelial cells and stored in Weibel-Palade bodies (WPBs). Understanding the mechanisms underlying WPB biogenesis and exocytosis could enable therapeutic modulation of endogenous VWF, yet optimal targets for modulating VWF release have not been established. Because biogenesis of lysosomal related organelle-2 (BLOC-2) functions in the biogenesis of platelet dense granules and melanosomes, which like WPBs are lysosome-related organelles, we hypothesized that BLOC-2–dependent endolysosomal trafficking is essential for WPB biogenesis and sought to identify BLOC-2–interacting proteins. Depletion of BLOC-2 caused misdirection of cargo-carrying transport tubules from endosomes, resulting in immature WPBs that lack endosomal input. Immunoprecipitation of BLOC-2 identified the exocyst complex as a binding partner. Depletion of the exocyst complex phenocopied BLOC-2 depletion, resulting in immature WPBs. Furthermore, releasates of immature WPBs from either BLOC-2 or exocyst-depleted endothelial cells lacked high-molecular weight (HMW) forms of VWF, demonstrating the importance of BLOC-2/exocyst-mediated endosomal input during VWF maturation. However, BLOC-2 and exocyst showed very different effects on VWF release. Although BLOC-2 depletion impaired exocytosis, exocyst depletion augmented WPB exocytosis, indicating that it acts as a clamp. Exposure of endothelial cells to a small molecule inhibitor of exocyst, Endosidin2, reversibly augmented secretion of mature WPBs containing HMW forms of VWF. These studies show that, although BLOC-2 and exocyst cooperate in WPB formation, only exocyst serves to clamp WPB release. Exocyst function in VWF maturation and release are separable, a feature that can be exploited to enhance VWF release.

Introduction: Patients (pts) with CLL may be at particular risk of severe COVID-19 given advanced age and immune dysregulation. Two large series with limited follow-up have reported outcomes for pts with CLL and COVID-19 (Scarfò, et al. Leukemia 2020; Mato, et al. Blood 2020). To provide maximal clarity on outcomes for pts with CLL and COVID-19, we partnered in a worldwide effort to describe the clinical experience and validate predictors of survival, including potential treatment effects. Methods: This international collaboration represents a partnership between investigators at 141 centers. Data are presented in two cohorts. Cohort 1 (Co1) includes pts captured through efforts by European Research Initiative on CLL (ERIC), Italian CAMPUS CLL Program, and Grupo Español de Leucemia Linfática Crónica. The validation cohort, Cohort 2 (Co2), includes pts from US (66%), UK (23%), EU (7%), and other countries (4%). There is no overlap in cases between cohorts. CLL pts were included if COVID-19 was diagnosed by PCR detection of SARS-CoV-2 and they required inpatient hospitalization. Data were collected retrospectively 2/2020 - 5/2020 using standardized case report forms. Baseline characteristics, preexisting comorbidities (including cumulative illness rating scale (CIRS) score ≥6 vs. The primary endpoint of this study was to estimate the case fatality rate (CFR), defined as the proportion of pts who died among all pts hospitalized with COVID-19. Chi-squared test was used to compare frequencies; univariable and multivariable analyses utilized Cox regression. Predictors of inferior OS in both Co1 and Co2 were included in multivariable analyses. Kaplan-Meier method was used to estimate overall survival (OS) from time of COVID-19 diagnosis (dx). Results: 411 hospitalized, COVID-19 positive CLL pts were analyzed (Co1 n=281, Co2 n=130). Table 1 describes baseline characteristics. At COVID-19 dx, median age was 72 in Co1 (range 37-94) and 68 in Co2 (range 41-98); 31% (Co1) and 45% (Co2) had CIRS ≥6. In Co1, 48% were treatment-naïve and 26% were receiving CLL-directed therapy at COVID-19 dx (66% BTKi ± anti-CD20, 19% Venetoclax ± anti-CD20, 9.6% chemo/chemoimmunotherapy (CIT), 1.4% PI3Ki, 4% other). In Co2, 36% were never treated and 49% were receiving CLL-directed therapy (65% BTKi ± anti-CD20, 19% Venetoclax ± anti-CD20, 9.4% multi-novel agent combinations, 1.6% CIT, 1.6% PI3Ki, 1.6% anti-CD20 monotherapy, 1.6% other). Most pts receiving CLL-directed therapy had it held at COVID-19 diagnosis (93% in Co1 and 81% in Co2). Frequency of most COVID-19 symptoms/laboratory abnormalities were similar in the two cohorts including fever (88% in both), lymphocytosis (ALC ≥30 x 109/L; 27% vs. 21%), and lymphocytopenia (ALC < 1.0 x 109/L; 18% vs. 28%), while others varied between Co1 and Co2 (p Median follow-up was 24 days (range 2-86) in Co1 and 17 days (1-43) in Co2. CFRs were similar in Co1 and Co2, 30% and 34% (p=0.45). 54% and 43% were discharged while 16% and 23% remained admitted at last follow-up in Co1 and Co2, respectively. The proportion of pts requiring supplemental oxygen was similar (89% vs. 92%) while rate of ICU admission was higher in Co2 (20% vs. 48%, p Conclusions : In the largest cancer dx-specific cohort reported, pts with CLL hospitalized for COVID-19 had a CFR of 30-34%. Advanced patient age at COVID-19 diagnosis was an independent predictor of OS in two large cohorts. This CFR will serve as a benchmark for mortality for future outcomes studies, including therapeutic interventions for COVID-19 in this population. The effect of CLL treatment on OS was inconsistent across cohorts; COVID-19 may be severe regardless of treatment status. While there were no significant differences in distribution of current lines of therapy between cohorts, prior chemo exposure was more common in Co1 vs. Co2, which may account for difference in OS. Extended follow-up will be presented. Disclosures Roeker: American Society of Hematology: Research Funding; Abbott Laboratories: Other: spouse with minority ownership interest ; AbbVie: Other: spouse with minority ownership interest . Scarfo:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees. Abrisqueta:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau; AbbVie: Consultancy, Honoraria, Speakers Bureau. Eyre:AbbVie: Consultancy, Honoraria, Other: travel support; Gilead: Consultancy, Honoraria, Other: travel support; Janssen: Consultancy, Honoraria, Other: travel support; KITE, AZ, Loxo Oncology at Lilly: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Muntañola Prat:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards. Villacampa:AstraZeneca: Other: advisory role; Merck Sharp & Dohme: Honoraria. Leslie:AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Speakers Bureau; KitePharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene/BMS: Speakers Bureau; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics/Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Speakers Bureau; Karyopharm: Speakers Bureau; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Allan:Acerta, Genentech, Abbvie, Sunesis, Ascentage, Pharmacyclics, Janssen, AstraZeneca, BeiGene: Consultancy; Celgene, Genentech, Janssen, TG Therapeutics: Research Funding; Abbvie, Janssen, AstraZeneca, Pharmacyclics: Honoraria. Furman:Incyte: Consultancy; Genentech: Consultancy; Sunesis: Consultancy; Pharmacyclics: Consultancy; Loxo Oncology: Consultancy; Oncotarget: Consultancy; Janssen: Consultancy, Speakers Bureau; TG Therapeutics: Consultancy, Research Funding; Abbvie: Consultancy; Beigene: Consultancy; AstraZeneca: Consultancy, Research Funding; Acerta: Consultancy; Verastem: Consultancy. Pagel:BeiGene, Astrazeneca, Loxo Oncology, Gilead: Consultancy. Hernandez-Rivas:Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Rovi: Membership on an entity's Board of Directors or advisory committees. Patel:Genentech: Consultancy, Speakers Bureau; Adaptive Biotechnologies: Consultancy; Janssen: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy; Kite: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau. Motta:Roche: Honoraria; Janssen: Honoraria. Lamanna:AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Verastem: Research Funding; Bei-Gene: Research Funding; TG Therapeutics: Research Funding; Acerta: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche-Genentech: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Vitale:Janssen: Honoraria. Kamdar:Roche: Research Funding. Österborg:BeiGene: Research Funding; Kancera: Current equity holder in publicly-traded company, Research Funding; Sanofi: Consultancy; Karolinska Univeristy Hospital, Stockholm, Sweden: Current Employment. Hanson:Janssen-Cilag: Research Funding; Gilead: Research Funding; AbbVie: Honoraria. Eichhorst:ArQule: Consultancy, Honoraria, Other: travel support, Research Funding; BeiGene: Consultancy, Honoraria, Other: travel support, Research Funding; Gilead: Consultancy, Honoraria, Other: travel support, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: travel support, Research Funding; Oxford Biomedica: Consultancy, Honoraria, Other: travel support, Research Funding; AbbVie: Consultancy, Honoraria, Other: travel support, Research Funding; F. Hoffmann-LaRoche: Consultancy, Honoraria, Other: travel support, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Other: travel support, Research Funding; Celgene: Consultancy, Honoraria, Other: travel support, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding. Reda:Gilead: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees. Varettoni:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel/accommodations/expenses; AbbVie: Other: Travel/accommodations/expenses; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees. Marchetti:Gilead: Consultancy; Novartis: Speakers Bureau; Amgen: Speakers Bureau; AbbVie: Other: Sponsored meetings; Takeda: Other: Sponsored meetings; Pfeizer: Other: Sponsored meetings. Munir:F. Hoffmann-La Roche: Consultancy, Other: Medical writing support, furnished by Scott Battle, PhD, of Health Interactions, was funded by F. Hoffmann-La Roche Ltd, Basel, Switzerland; Alexion: Honoraria. Zabalza:Janssen: Honoraria, Other: travel grants; Roche: Other: travel grants; Novartis: Other: travel grants. Janssens:Amgen: Consultancy, Other: travel grants; speaker fees; Abbvie: Consultancy, Other: travel grants; speaker fees; Celgene: Consultancy, Other: travel grants; speaker fees; Janssen: Consultancy, Other: travel grants; speaker fees; Gilead: Consultancy, Other: travel grants; speaker fees; Novartis: Consultancy, Other: travel grants; speaker fees; Sanofi-Genzyme: Consultancy, Other: travel grants; speaker fees; Roche: Consultancy, Other: travel grants; speaker fees. Niemann:AstraZeneca: Honoraria, Research Funding; CSL Behring: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Sunesis: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Danish Cancer Society: Honoraria, Research Funding; Novo Nordisk Foundation: Honoraria, Research Funding. Perini:Takeda: Honoraria; Janssen: Honoraria, Speakers Bureau; Abbvie: Speakers Bureau. Patten:AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra Zeneca: Honoraria. Marasca:Roche: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Honoraria. Iyengar:Janssen: Honoraria; Gilead: Honoraria. Ferrari:Abbvie: Honoraria. El-Sharkawi:Roche: Other: Conference fees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Itchaki:Abbvie Inc: Consultancy, Research Funding. Ma:Novartis: Research Funding; Juno: Research Funding; Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kite: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; Bioverativ: Consultancy, Honoraria; BeiGene: Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding; TG Therapeutics: Research Funding. Van Der Spek:AMGEN: Other: Teaching activities. Seymour:Seattle Genetics: Research Funding; Merck: Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen/Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Genentech: Research Funding; Bristol-Myers Squibb: Research Funding. Rigolin:Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Mauro:Roche: Other; Octopharma: Other; Takeda-Shire: Other; Gilead: Other; Janssen: Other; Abbvie: Other. Laurenti:Janssen: Honoraria; Gilead: Honoraria; AbbVie: Honoraria; Roche: Honoraria. Levin:Janssen: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation; Abbvie: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation; Roche: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation. Špaček:Gilead: Honoraria; Abbvie: Honoraria; Janssen: Honoraria. Walewska:AbbVie: Other: sponsored for educational meetings, Speakers Bureau; Janssen: Other: sponsored for educational meetings, Speakers Bureau; Gilead: Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees. Wiestner:Pharmacyclics LLC, an AbbVie Company; Acerta, Merck, Nurix, Verastem, and Genmab: Research Funding; National Institutes of Health: Patents & Royalties: and other intellectual property. Broom:Gilead: Other: Travel support, Speakers Bureau. Kater:Abbvie: Research Funding; Roche: Research Funding; Janssen: Research Funding; Celgene: Research Funding; Genentech: Research Funding. Ujjani:AstraZeneca: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Verastem Oncology: Consultancy, Honoraria; Gilead/Kite: Consultancy, Research Funding; Atara: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; MorphoSys: Consultancy. Vandenberghe:Celgene: Other: sponsorship to attend Lugano lymphoma meeting in 2019; Gilead: Other: travel grants, Research Funding; Abbvie: Other: travel grants, Research Funding; Janssen: Other: travel grants; Roche: Other: travel grants, Research Funding. Chong:Novartis: Membership on an entity's Board of Directors or advisory committees; Tessa: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; KITE Pharma: Membership on an entity's Board of Directors or advisory committees. Pu:Takeda Pharmaceuticals: Consultancy. Brown:Janssen, Teva: Speakers Bureau; Gilead, Loxo, Sun, Verastem: Research Funding; Abbvie, Acerta, AstraZeneca, Beigene, Invectys, Juno/Celgene, Kite, Morphosys, Novartis, Octapharma, Pharmacyclics, Sunesis, TG Therapeutics, Verastem: Consultancy. Trentin:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Octapharma: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria. Farina:Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Sanchez:Abbvie: Other: travel grants; Amgem: Other: travel grants; Janssen: Other: travel grants; Celgene: Other: travel grants; Roche: Other: travel grants. Shadman:Abbvie, Genentech, Astra Zeneca, Sound Biologics , Pharmacyclics, Verastem, ADC therapeutics, Beigene, Cellectar, BMS, Morphosys and Atara Biotherapeutics: Consultancy; Mustang Bio, Celgene, Pharmacyclics, Gilead, Genentech, Abbvie, TG therapeutics, Beigene, Astra Zeneca, Sunesis, Beigene: Research Funding. Foglietta:Janssen: Honoraria; Gilead: Honoraria. Jaksic:Roche: Honoraria; Janssen: Honoraria; Abbvie: Honoraria. Sportoletti:AbbVie: Honoraria; Janssen: Honoraria. Barr:Morphosys: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy, Research Funding; Verastem: Consultancy; Seattle Genetics: Consultancy; TG therapeutics: Consultancy, Research Funding; Abbvie/Pharmacyclics: Consultancy, Research Funding; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy; Janssen: Consultancy. Ruchlemer:Abbvie Inc: Consultancy, Research Funding. Kersting:Celgene: Other: travel grant; Janssen: Research Funding; Abbvie: Research Funding. Huntington:Pharmacyclics: Honoraria; AbbVie: Consultancy; Novartis: Consultancy; Genentech: Consultancy; DTRM: Research Funding; Celgene: Consultancy, Research Funding; Bayer: Consultancy, Honoraria; Astrazeneca: Honoraria; TG Therapeutics: Research Funding. Herishanu:Roche: Honoraria; Sanofi: Honoraria; Medison: Honoraria; Janssen: Honoraria; Abbvie: Honoraria; AstraZeneca: Honoraria. Jacobs:TG Therapeutics, Inc.: Research Funding; Astra Zeneca: Consultancy, Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Pharmacyclics: Research Funding, Speakers Bureau; Seattle Genetics: Consultancy; Verastem: Consultancy; Janssen: Consultancy, Speakers Bureau; Genentech: Speakers Bureau; Sanofi Genzyme: Speakers Bureau. Portell:BeiGene: Consultancy, Research Funding; Pharmacyclics: Consultancy; TG Therapeutics: Research Funding; Infinity: Research Funding; Roche/Genentech: Consultancy, Research Funding; Xencor: Research Funding; Bayer: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding; AbbVie: Research Funding. Rambaldi:Sanofi: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Astellas: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); BMS/Celgene: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); University of Milan: Current Employment; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support of parent study and funding of editorial support. Received travel support., Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support from Gilead.; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Research grant from Amgen Inc.; Omeros: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Advisory board and speaker fees from Pfizer.. Brander:Verastem: Consultancy, Honoraria, Other, Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; ArQule: Consultancy, Other, Research Funding; Ascentage: Other, Research Funding; AstraZeneca: Consultancy, Honoraria, Other, Research Funding; BeiGene: Other, Research Funding; DTRM: Other, Research Funding; Genentech: Consultancy, Honoraria, Other, Research Funding; Juno/Celgene/BMS: Other, Research Funding; MEI Pharma: Other, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Other, Research Funding; Pfizer: Consultancy, Other; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding. Rossi:Abbvie: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Advisory board; Astellas: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Coscia:Karyopharm Therapeutics: Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Coombs:Abbvie: Consultancy, Honoraria; Genentech: Honoraria; AstraZeneca: Honoraria; MEI Pharma: Honoraria; LOXO Oncology: Honoraria; Octapharma: Honoraria; Novartis: Honoraria. Schuster:Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding; AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria. Foà:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Cuneo:Astra Zeneca: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bosch:Jansen: Honoraria; Abbvie: Honoraria; Novartis: Honoraria; Astra Zeneca: Honoraria; Takeda: Honoraria; Celgene: Honoraria; Roche: Honoraria. Stamatopoulos:AstraZeneca: Honoraria; Janssen, Gilead, Abbvie: Honoraria, Research Funding. Ghia:Adaptive, Dynamo: Consultancy, Honoraria; Novartis: Research Funding; BeiGene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Celgene/Juno: Consultancy, Honoraria; Lilly: Consultancy, Honoraria; MEI: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Gilead: Consultancy, Honoraria, Research Funding; ArQule: Consultancy, Honoraria; Acerta/AstraZeneca: Consultancy, Honoraria. Mato:Adaptive: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; BeiGene: Consultancy; LOXO: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding.

Introduction: Venetoclax has demonstrated deep responses and sustained progression-free survival and is well tolerated in patients (pts) with previously untreated or relapsed/refractory (R/R) chronic lymphocytic leukemia/small lymphocytic leukemia (CLL/SLL) in clinical trials. Some early studies provided initial insight of venetoclax utilization in the real-world (RW), but RW evidence focusing on venetoclax effectiveness and safety is still limited. This study assessed venetoclax effectiveness, safety, and treatment patterns in CLL pts treated in clinical practice. Methods: The CLL Collaborative Study of Real-World Evidence (CORE), a large multicenter chart review across 21 institutions in 4 countries, enrolled adult pts who initiated a first line (1L) therapy on/after 01/01/2012 or a new line of therapy (LOT) for R/R CLL/SLL on/after 02/12/2014 (current data cut through 06/08/2020). Clinical responses were abstracted from the medical records as assessed by treating physicians or investigators (iwCLL criteria were provided as reference). Overall response rate (ORR) was calculated as the proportion of pts with complete response (CR) or partial response (PR) out of pts with documented response assessments. Treatment patterns included choice of regimens and sequences, dose interruption, dose reduction, and discontinuation. Treatment discontinuation was defined as ending therapy for any reason(s) other than the completion of planned duration of therapy. Interruption was defined as a gap in the same LOT. All analyses were descriptive. Results: Of the 1231 CLL pts in the CORE data, 155 received venetoclax (21 in 1L and 134 in R/R) and were included in this study. Most of the sample were male (65%) and the median age at venetoclax initiation was 67.5 (range 37-91). For high-risk features among pts with available data, 33% (43/132 pts) had del(17p) or TP53 mutation, 24% (31/131 pts) had complex karyotype (≥ 3 abnormalities), and 77% (61/79 pts) had unmutated IGHV. At venetoclax initiation, 46%, 40%, and 14% of 151 pts with available data had low, medium, and high tumor burden, respectively. Median follow-up time from venetoclax initiation across all lines was 7.0 (0.1-43.1) months. Median number of prior LOT for R/R pts was 2 (1-5); the largest proportion of pts (36%) received venetoclax in 2L followed by 3L (26%). In 1L, venetoclax was most frequently used (62%) in combination (Figure 1), while in R/R setting venetoclax monotherapy was more commonly used (61%) followed by venetoclax + rituximab (25%; Figure 2). Majority of R/R pts (63%) received Bruton's tyrosine kinase inhibitors (BTKi) prior to venetoclax (Figure 2). Response was assessed and documented for 114 pts (74%). Among these, ORR was 75% (CR=40%, PR=35%) overall. Pts ≥65 years old had an ORR of 79% (CR=41%, PR=38%, n=74), and pts Overall, 48% of pts had adverse events (AEs) recorded. Five R/R pts (3.2%) had TLS events (defined by Howard or Cairo-Bishop criteria), of which 3 (1.9%) were clinical. Of the 5 pts, 2 had high tumor burden, and 3 had medium burden. Other AEs of interest include neutropenia (17%), thrombocytopenia (9%), and diarrhea/colitis (5%). Overall, 32% of pts discontinued venetoclax; 13% of all pts discontinued venetoclax due to AEs (primarily neutropenia [n=2] and thrombocytopenia [n=2]), followed by disease progression (8%). Venetoclax interruption rate was 14%, and dose reduction rate was 22% overall. Conclusions: Consistent with trial experiences, venetoclax demonstrates high response rates, including high-risk groups, and a manageable safety profile with low rates of TLS in clinical practice. Despite limitations of RW research, this study provides useful insights into treatment practices with venetoclax. Future research with longer follow-up is warranted to better understand the long-term clinical outcomes associated with venetoclax regimens. Disclosures Zheng: AbbVie: Current Employment. Sail:AbbVie Inc.: Current Employment, Current equity holder in publicly-traded company. Roeker:Abbott Laboratories: Other: spouse with minority ownership interest ; American Society of Hematology: Research Funding; AbbVie: Other: spouse with minority ownership interest . Manzoor:AbbVie: Current equity holder in publicly-traded company. Tuncer:AbbVie: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees. Allan:Abbvie, Janssen, AstraZeneca, Pharmacyclics: Honoraria; Celgene, Genentech, Janssen, TG Therapeutics: Research Funding; Acerta, Genentech, Abbvie, Sunesis, Ascentage, Pharmacyclics, Janssen, AstraZeneca, BeiGene: Consultancy. Ujjani:Gilead/Kite: Consultancy, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding; Genentech: Consultancy, Honoraria; MorphoSys: Consultancy; Atara: Consultancy, Honoraria; Verastem Oncology: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Research Funding. Barr:Genentech: Consultancy; Merck: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Janssen: Consultancy; Celgene: Consultancy; Seattle Genetics: Consultancy; Verastem: Consultancy; TG therapeutics: Consultancy, Research Funding; Morphosys: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy, Research Funding. Brown:Novartis: Consultancy; Nextcea: Consultancy; Octapharma: Consultancy; MEI Pharma: Consultancy; Eli Lilly and Company: Consultancy; Astra-Zeneca: Consultancy; TG Therapeutics: Consultancy; Sunesis: Consultancy; Loxo: Consultancy, Research Funding; Sun: Research Funding; Rigel Pharmaceuticals: Consultancy; Pfizer: Consultancy; Catapult: Consultancy; Dynamo Therapeutics: Consultancy; Pharmacyclics: Consultancy; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other; Gilead: Consultancy, Research Funding; Genentech: Consultancy; BeiGene: Consultancy; Invectys: Membership on an entity's Board of Directors or advisory committees, Other: DSMC; Janssen: Honoraria; AbbVie: Consultancy; Kite: Consultancy; Juno/Celgene: Consultancy; Verastem: Consultancy, Research Funding; Acerta: Consultancy. Eyre:AbbVie: Consultancy, Honoraria, Other: travel support; KITE, AZ, Loxo Oncology at Lilly: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Other: travel support; Gilead: Consultancy, Honoraria, Other: travel support. Skarbnik:Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CLL Society: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion: Consultancy; Beigene: Speakers Bureau; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Speakers Bureau; Verastem: Speakers Bureau; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bannerji:Regeneron Pharmaceuticals: Research Funding; F. Hoffmann-La Roche Ltd/Genentech, Inc and Pharmacyclics LLC, an AbbVie Company: Research Funding; Sanofi-Pasteur: Other: Spouse is employee; AbbVie: Research Funding. Eichhorst:BeiGene: Consultancy, Honoraria, Other: travel support, Research Funding; AbbVie: Consultancy, Honoraria, Other: travel support, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Other: travel support, Research Funding; F. Hoffmann-LaRoche: Consultancy, Honoraria, Other: travel support, Research Funding; ArQule: Consultancy, Honoraria, Other: travel support, Research Funding; Gilead: Consultancy, Honoraria, Other: travel support, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: travel support, Research Funding; Oxford Biomedica: Consultancy, Honoraria, Other: travel support, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding; Celgene: Consultancy, Honoraria, Other: travel support, Research Funding. Brander:Verastem: Consultancy, Honoraria, Other, Research Funding; NCCN: Other; Genentech: Consultancy, Honoraria, Other, Research Funding; Juno/Celgene/BMS: Other, Research Funding; MEI Pharma: Other, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Other, Research Funding; Pfizer: Consultancy, Other; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; Ascentage: Other, Research Funding; ArQule: Consultancy, Other, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Tolero: Research Funding; Teva: Consultancy, Honoraria; Novartis: Consultancy, Other; DTRM: Other, Research Funding; AstraZeneca: Consultancy, Honoraria, Other, Research Funding; BeiGene: Other, Research Funding. Sharmokh:AbbVie: Current Employment, Current equity holder in publicly-traded company. Jiang:AbbVie: Current Employment, Other: may hold stock or options. Pena:AbbVie: Current Employment, Current equity holder in publicly-traded company. Kamalakar:AbbVie: Current Employment, Other: may hold stock or other options. Emechebe:AbbVie: Current Employment, Current equity holder in publicly-traded company. Pivneva:Novartis: Consultancy, Other: Irina Pivneva is an employee of Analysis Group, Inc which received consultancy fees from Novartis.. Burne:Analysis Group, Inc., which has received consultancy fees from AbbVie: Current Employment. Guerin:Abbvie: Consultancy, Other; Novartis Pharmaceuticals Corporation: Consultancy, Other: Annie Guerin is an employee of Analysis Group, Inc. which received consultancy fees from Novartis.; Sanofi Genzyme: Consultancy, Other: Annie Guerin is an employee of Analysis Group, Inc. which received consultancy fees from Sanofi Genzyme.. Davids:Celgene: Consultancy; Research to Practice: Honoraria; AbbVie: Consultancy; Sunesis: Consultancy; Genentech: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; MEI Pharma: Consultancy, Research Funding; Surface Oncology: Research Funding; BeiGene: Consultancy; Novartis: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Bristol Myers Squibb: Research Funding; Janssen: Consultancy; Adaptive Biotechnologies: Consultancy; Ascentage Pharma: Consultancy, Research Funding; Gilead Sciences: Consultancy; Eli Lilly: Consultancy; Syros Pharmaceuticals: Consultancy; Zentalis: Consultancy; Merck: Consultancy; TG Therapeutics: Consultancy, Research Funding; Verastem: Consultancy, Research Funding. Mato:AbbVie: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Loxo: Consultancy, Research Funding; Janssen: Consultancy, Research Funding.

Herein, we present the long-term follow-up of the randomized E1912 trial comparing the long-term efficacy of ibrutinib–rituximab (IR) therapy to fludarabine, cyclophosphamide, and rituximab (FCR) and describe the tolerability of continuous ibrutinib. The E1912 trial enrolled 529 treatment-naïve patients aged ≤70 years with chronic lymphocytic leukemia (CLL). Patients were randomly assigned (2:1 ratio) to receive IR or 6 cycles of FCR. With a median follow-up of 5.8 years, median progression-free survival (PFS) is superior for IR (hazard ratio [HR], 0.37; P < .001). IR improved PFS relative to FCR in patients with both immunoglobulin heavy chain variable region (IGHV) gene mutated CLL (HR: 0.27; P < .001) and IGHV unmutated CLL (HR: 0.27; P < .001). Among the 354 patients randomized to IR, 214 (60.5%) currently remain on ibrutinib. Among the 138 IR-treated patients who discontinued treatment, 37 (10.5% of patients who started IR) discontinued therapy due to disease progression or death, 77 (21.9% of patients who started IR) discontinued therapy for adverse events (AEs)/complications, and 24 (6.8% of patients who started IR) withdrew for other reasons. Progression was uncommon among patients able to remain on ibrutinib. The median time from ibrutinib discontinuation to disease progression or death among those who discontinued treatment for a reason other than progression was 25 months. Sustained improvement in overall survival (OS) was observed for patients in the IR arm (HR, 0.47; P = .018). In conclusion, IR therapy offers superior PFS relative to FCR in patients with IGHV mutated or unmutated CLL, as well as superior OS. Continuous ibrutinib therapy is tolerated beyond 5 years in the majority of CLL patients. This trial was registered at www.clinicaltrials.gov as #NCT02048813.

CAPTIVATE (NCT02910583) is an international phase 2 study in patients aged ≤70 years with previously untreated chronic lymphocytic leukemia (CLL). Results from the cohort investigating fixed-duration (FD) treatment with ibrutinib plus venetoclax are reported. Patients received 3 cycles of ibrutinib lead-in then 12 cycles of ibrutinib plus venetoclax (oral ibrutinib [420 mg/d]; oral venetoclax [5-week ramp-up to 400 mg/d]). The primary endpoint was complete response (CR) rate. Hypothesis testing was performed for patients without del(17p) with prespecified analyses in all treated patients. Secondary endpoints included undetectable minimal residual disease (uMRD) rates, progression-free survival (PFS), overall survival (OS), and safety. Of the 159 patients enrolled and treated, 136 were without del(17p). The median time on study was 27.9 months, and 92% of patients completed all planned treatment. The primary endpoint was met, with a CR rate of 56% (95% confidence interval [CI], 48-64) in patients without del(17p), significantly higher than the prespecified 37% minimum rate (P < .0001). In the all-treated population, CR rate was 55% (95% CI, 48-63); best uMRD rates were 77% (peripheral blood [PB]) and 60% (bone marrow [BM]); 24-month PFS and OS rates were 95% and 98%, respectively. At baseline, 21% of patients were in the high tumor burden category for tumor lysis syndrome (TLS) risk; after ibrutinib lead-in, only 1% remained in this category. The most common grade ≥3 adverse events (AEs) were neutropenia (33%) and hypertension (6%). First-line ibrutinib plus venetoclax represents the first all-oral, once-daily, chemotherapy-free FD regimen for patients with CLL. FD ibrutinib plus venetoclax achieved deep, durable responses and promising PFS, including in patients with high-risk features.

BACKGROUND: Treatment of chronic lymphocytic leukemia (CLL) with a fixed-duration venetoclax (Ven)-based regimen is now a standard of care (SOC) option for both frontline and relapsed refractory (R/R) disease based on results of the CLL14 and MURANO trials (Fischer et al NEJM 2019, Seymour et al NEJM 2018). As fixed-duration Ven regimens are now a SOC, it is expected that an increasing number of patients (pts) will ultimately progress after Ven exposure and require additional CLL-directed therapy. While many discuss re-treatment with Ven as a subsequent treatment option, the current literature contains response data on an extremely limited number of evaluable pts (11 pts MURANO, overall response rate (ORR) 55%; 3 pts VEN 365, ORR 100%). Whether re-treatment with Ven is an acceptable option remains an important unanswered clinical question. METHODS: We conducted a multicenter, retrospective study of CLL pts treated with a Ven-based regimen (Ven1) and then re-treated with a second Ven-based regimen (Ven2) in a later line of therapy (LOT). Data were collected from 13 centers and the CLL Collaborative Study of Real-World Evidence database. CLL pts were eligible for inclusion if they were treated with a Ven-based regimen in any LOT and then re-treated with a Ven-based regimen as a later LOT. Collected data included demographics, prognostic disease characteristics, tumor lysis syndrome (TLS) risk and incidence, clinical response and reasons for treatment discontinuation (dc). The primary study endpoint was investigator-assessed ORR (CR: complete response, PR: partial response, SD: stable disease, PD: progression of disease, iwCLL 2018). Kaplan-Meier method was used to estimate progression free survival (PFS). All other analyses were descriptive. RESULTS: We identified 25 pts who were re-treated with Ven. Pt characteristics prior to treatment with Ven1 are summarized in Table 1. In 24% of pts (n=6), Ven1 was administered as part of a clinical trial. Median prior LOT was 2 (range 0-10) with 12.0% treatment naïve and 60% with prior BTKi exposure. The majority of pts had ≥1 high-risk prognostic marker: del17p (39%), TP53 mut (27%), complex karyotype ≥5 abnormalities (30%) and unmutated IGHV (84%). For Ven1, treatment regimens, TLS risk, and dose are summarized in Table 2. With a median duration of exposure of 15 months (mos) (64% pts > 12 mos) for Ven1, the ORR was 88% (CR: 48%, PR: 40%, Figure 1A). Ten pts had minimal residual disease (MRD) assessments by flow cytometry; 8 pts (80%) achieved undetectable MRD (10^-4). Most common reasons for Ven1 dc included: toxicity (28%), completion of planned therapy (24%), MD/pt preference (24%), other (12%), alloHSCT (4%) and cost (4%). There was a median of 8.7 mos (36% > 12 mos) between Ven1 and the initiation of Ven2, and 88% did not receive another LOT between Ven1 and Ven2. Reasons for Ven2 initiation were either CLL progression (87.5%) or MRD-positive relapse (12.5%). For Ven2, TLS risk, TLS incidence and dose information are outlined in Table 2. TLS was a rare event during Ven re-treatment (4.5%, lab only). For Ven2, Ven monotherapy was the most common regimen (52%). Standard Ven dose-escalation was used for re-initiation in 17 of 19 pts with available data, however 1 pt started Ven2 at 400 mg daily (no TLS) and another underwent a prolonged ramp-up period. At the time of this analysis, 18 pts had available response assessments for Ven2: ORR is 72.2% (CR: 4, PR: 9, SD: 4 and PD: 1, Figure 1B). Median time from Ven2 to progression or last follow up is 8 mos (0.2-29 mos). Median PFS has not been reached. Estimated 12-month PFS is 69.1%. For pts with a CR to Ven2, median follow up time is 14.5 mos vs 7 mos for pts with PR or SD. Of 25 pts re-treated with Ven, 68% remain on Ven2 presently and 32% have discontinued Ven2, including due to CLL progression (n=4), completion of planned therapy (n=1), unrelated death (n=1), MD/pt preference (n=1). CONCLUSIONS: To our knowledge, this is the largest reported cohort of CLL pts re-treated with Ven after a prior Ven-based regimen. The high ORR in this pt population (median 2 prior therapies) suggests that re-treatment is a promising strategy and should be considered in treatment sequencing algorithms. Notably, pts with a CR to Ven2 had a longer median follow up than those with a PR or SD, suggesting a likelihood of deeper responses with time. Given the promising ORR, further research to prospectively validate Ven re-treatment is warranted. Updated data will be presented. Disclosures Allan: Celgene, Genentech, Janssen, TG Therapeutics: Research Funding; Abbvie, Janssen, AstraZeneca, Pharmacyclics: Honoraria; Acerta, Genentech, Abbvie, Sunesis, Ascentage, Pharmacyclics, Janssen, AstraZeneca, BeiGene: Consultancy. Sail:AbbVie Inc.: Current Employment, Current equity holder in publicly-traded company. Manzoor:Abbvie: Current Employment, Other: may hold stock or stock options. Pu:Takeda Pharmaceuticals: Consultancy. Barr:Gilead: Consultancy; Janssen: Consultancy; AstraZeneca: Consultancy, Research Funding; Abbvie/Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy; Morphosys: Consultancy; TG therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy. Coombs:LOXO Oncology: Honoraria; MEI Pharma: Honoraria; Abbvie: Consultancy, Honoraria; Genentech: Honoraria; AstraZeneca: Honoraria; Octapharma: Honoraria; Novartis: Honoraria. Schuster:AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria; Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding. Skarbnik:Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion: Consultancy; Beigene: Speakers Bureau; Verastem: Speakers Bureau; Novartis: Speakers Bureau; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CLL Society: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rhodes:Verastem: Consultancy; Abbvie/Genentech: Consultancy; Pharmacyclics: Consultancy; AstraZeneca: Consultancy. Barrientos:Janssen: Honoraria; Sandoz: Consultancy; Oncternal Therapeutics: Research Funding; Bayer: Consultancy; Genentech: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy. Roeker:American Society of Hematology: Research Funding; Abbott Laboratories: Other: spouse with minority ownership interest ; AbbVie: Other: spouse with minority ownership interest . Leslie:Celgene: Speakers Bureau; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Speakers Bureau; KitePharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BeiGene: Honoraria, Speakers Bureau; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Honoraria, Speakers Bureau; Karyopharm: Honoraria, Speakers Bureau; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Kamdar:Roche: Research Funding. Choi:Pharmacyclics/Abbvie: Research Funding; Genentech: Consultancy. Simkovic:Abbvie: Consultancy, Other: travel expenses. Lansigan:Seattle Genetics: Consultancy; BMS: Consultancy; BMS Steering Committee for MAGNIFY Program: Membership on an entity's Board of Directors or advisory committees; Spectrum Pharma: Consultancy, Research Funding. Zelenetz:Novartis: Consultancy; Gilead: Research Funding; Janssen: Consultancy; Celgene: Consultancy; Gilead: Consultancy; Genentech/Roche: Consultancy; Roche: Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnology: Consultancy; MorphoSys: Research Funding; Amgen: Consultancy; Sandoz: Research Funding; Celgene: Research Funding; MEI Pharma: Research Funding. Moskowitz:Merck: Research Funding; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Miragen Therapeutics: Consultancy; Incyte: Research Funding; Merck: Consultancy; Imbrium Therapeutics, L.P.: Consultancy; Seattle Genetics: Consultancy. Goy:Morphosys: Research Funding; AbbVie: Research Funding; MD Anderson: Research Funding; Regional Cancer Care Associates/OMI: Current Employment; Infinity Verastem: Research Funding; Infinity: Research Funding; Karyopharm: Research Funding; Genentech/Roche: Research Funding; CALBG: Research Funding; Constellation: Research Funding; Bayer: Research Funding; PracticeUpdate Oncology: Consultancy; RCCA/OMI: Current Employment; Acerta: Consultancy, Honoraria, Other: leadership role, Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: leadership role, Research Funding; Celgene: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: leadership role, Research Funding; COTA: Consultancy, Current equity holder in publicly-traded company, Other: leadership role; Kite, a Gilead Company: Consultancy, Current equity holder in publicly-traded company, Honoraria, Other: leadership role, Research Funding; Xcenda: Consultancy; Hackensack UMC and University of Nebraska: Research Funding. Feldman:Pfizer: Research Funding; Kyowa Kirin: Consultancy, Research Funding; Eisai: Research Funding; Cell Medica: Research Funding; Amgen: Research Funding; Pharmacyclics: Honoraria, Other, Speakers Bureau; Abbvie: Honoraria; Bayer: Consultancy, Honoraria; Trillium: Research Funding; Portola: Research Funding; Janssen: Speakers Bureau; AstraZeneca: Consultancy; Viracta: Research Funding; Rhizen: Research Funding; Corvus: Research Funding; BMS: Consultancy, Honoraria, Research Funding; Kite: Honoraria, Other: Travel expenses, Speakers Bureau; Celgene: Honoraria, Research Funding; Takeda: Honoraria, Other: Travel expenses; Seattle Genetics, Inc.: Consultancy, Honoraria, Other: Travel expenses, Research Funding, Speakers Bureau. Furman:Verastem: Consultancy; Genentech: Consultancy; Beigene: Consultancy; AstraZeneca: Consultancy, Research Funding; Acerta: Consultancy; Abbvie: Consultancy; TG Therapeutics: Consultancy, Research Funding; Sunesis: Consultancy; Pharmacyclics: Consultancy; Oncotarget: Consultancy; Loxo Oncology: Consultancy; Janssen: Consultancy, Speakers Bureau; Incyte: Consultancy. Mato:Genentech: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; BeiGene: Consultancy; LOXO: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; Adaptive: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding.

Patients with advanced-stage Hodgkin lymphoma (HL) demonstrated excellent 2-year progression-free survival (PFS) after receiving positron emission tomography (PET)-adapted therapy on S0816 (NCT00822120). Patients received 2 cycles of doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD). Patients achieving complete remission (CR) on PET2 (Deauville Score{less than or equal to}3) continued 4 additional cycles of ABVD. Patients not achieving CR on PET2 (Deauville Scoreg3) were switched to escalated bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (eBEACOPP) for 6 cycles. We report the 5-year follow-up of S0816. A subset of 336 eligible patients were analyzed (331 had central review of PET2). PET2 was negative in 82% and positive in 18%. For all patients, the estimated 5-year PFS was 74% (95%CI:69%-79%). For patients with PET2-, the 5-year PFS was 76% (95%CI:70-81%). For patients with PET2+, the 5-year PFS was 66% (95% CI:52-76%). For all patients, the estimated 5-year overall survival (OS) was 94% (95%CI:91%-96%). There were 7 (14%) reported cases of second cancers in patients treated with eBEACOPP and 6 (2%) in patients treated with ABVD (P=0.001). The long-term OS of HL patients treated on S0816 remains high. However, nearly 25% of patients with PET2- experienced relapse events, demonstrating limitations of frontline ABVD therapy and in the negative predictive value of PET2. In PET2+ patients who received eBEACOPP, PFS was favorable, but was associated with a high rate of second malignancies compared with historical controls. Our results emphasize the importance of long-term follow-up, and the need for more efficacious and less toxic therapeutic approaches for advanced-stage HL patients

Ibrutinib, a once-daily oral inhibitor of Bruton tyrosine kinase, has greatly improved outcomes for patients with chronic lymphocytic leukemia (CLL). The phase 3 RESONATE trial, which compared single-agent ibrutinib to ofatumumab in high-risk, relapsed patients with CLL, provided support for approval of ibrutinib in the United States and Europe. We describe long-term follow-up of patients treated in RESONATE, where continued superiority of progression-free survival (PFS) (hazard ratio [HR], 0.133; 95% confidence interval [CI], 0.099-0.178) was observed. Overall survival benefit continues (HR, 0.591; 95% CI, 0.378-0.926), although with decreased magnitude relative to that seen before crossover to ibrutinib was implemented for patients on ofatumumab (HR, 0.426; 95% CI, 0.220-0.823). Notably, overall response to ibrutinib increased over time, with 91% of patients attaining a response. The PFS benefit with ibrutinib was independent of baseline risk factors, although patients with ≥2 prior therapies had shorter PFS than those with

E1912 was a randomized phase 3 trial comparing indefinite ibrutinib plus 6 cycles of rituximab (IR) to 6 cycles of fludarabine, cyclophosphamide, and rituximab (FCR) in untreated younger patients with CLL. We describe measurable residual disease (MRD) levels in E1912 over time and correlate them with clinical outcome. Undetectable MRD rates (

There is a Blood Commentary on this article in this issue., Key Points Both watch-and-wait and treated CLL patients have high mortality rates when admitted for COVID-19. Receiving a BTKi for CLL at COVID-19 diagnosis severe enough to require hospitalization did not influence case fatality rate in this study., Given advanced age, comorbidities, and immune dysfunction, chronic lymphocytic leukemia (CLL) patients may be at particularly high risk of infection and poor outcomes related to coronavirus disease 2019 (COVID-19). Robust analysis of outcomes for CLL patients, particularly examining effects of baseline characteristics and CLL-directed therapy, is critical to optimally manage CLL patients through this evolving pandemic. CLL patients diagnosed with symptomatic COVID-19 across 43 international centers (n = 198) were included. Hospital admission occurred in 90%. Median age at COVID-19 diagnosis was 70.5 years. Median Cumulative Illness Rating Scale score was 8 (range, 4-32). Thirty-nine percent were treatment naive (“watch and wait”), while 61% had received ≥1 CLL-directed therapy (median, 2; range, 1-8). Ninety patients (45%) were receiving active CLL therapy at COVID-19 diagnosis, most commonly Bruton tyrosine kinase inhibitors (BTKi’s; n = 68/90 [76%]). At a median follow-up of 16 days, the overall case fatality rate was 33%, though 25% remain admitted. Watch-and-wait and treated cohorts had similar rates of admission (89% vs 90%), intensive care unit admission (35% vs 36%), intubation (33% vs 25%), and mortality (37% vs 32%). CLL-directed treatment with BTKi’s at COVID-19 diagnosis did not impact survival (case fatality rate, 34% vs 35%), though the BTKi was held during the COVID-19 course for most patients. These data suggest that the subgroup of CLL patients admitted with COVID-19, regardless of disease phase or treatment status, are at high risk of death. Future epidemiologic studies are needed to assess severe acute respiratory syndrome coronavirus 2 infection risk, these data should be validated independently, and randomized studies of BTKi’s in COVID-19 are needed to provide definitive evidence of benefit., Visual Abstract

Background: The ECOG-ACRIN randomized phase 3 clinical trial E1912 established ibrutinib-rituximab (IR) as the standard of care for CLL patients Methods: Patients enrolled on E1912 completed the Functional Assessment of Cancer Therapy-General (FACT-G) and Leukemia subscale at randomization (baseline), 3, 6, and 12 months post-randomization, and every 6 months for 2 years regardless of disease status. The primary outcome was the 31-item FACT-Leukemia Trial Outcome Index (FACT-Leu TOI), calculated by summing items from the FACT-G physical wellbeing (PWB), functional well-being (FWB), and leukemia subscales (score range: 0-124). The primary endpoint was defined as the difference in FACT-Leu TOI change scores from randomization to 12 months (at response evaluation) between patients treated with continuous therapy Arm A (IR) vs time-limited therapy Arm B (FCR). Mean change scores from baseline to each time point were calculated using all cases with data at baseline and the corresponding time point. Comparisons between treatment arms were performed using two-sample t tests. Linear mixed effects models were used to estimate the trajectories of PRO scores. Results: PRO data was extracted on 3/8/2021. PRO data was provided at baseline and 12 months for 233/354 (65.8%) patients on the IR arm and 118/175 (67.4%) patients on the FCR arm. At enrollment, there were no significant differences in the baseline FACT-Leu TOI scores (mean ± SE) between the two arms: IR (93.27 ± 1.03) vs FCR (92.68 ± 1.38; p=0.73). The FACT-Leu TOI score improved from baseline to 12 months in both arms (Table 1 and Figure 1). The change scores from baseline to 12 months, the primary outcome, were not significantly different between IR (7.59 ± 1.09) vs FCR (8.22 ± 1.44; p=0.73). Change in FACT-Leu TOI from baseline to 3 months was 5.77 ± 0.77 and 4.06 ± 1.18 (p=0.22); and from baseline to 6 months was 6.87 ± 0.87 and 8.01 ± 1.44 (p=0.50) in the IR and FCR arms, respectively. After the first 6 months of treatment, the improvement in FACT-Leu TOI scores was maintained in both treatment arms. There was no significant difference in total FACT-Leu TOI score in the continuous therapy (IR) vs time-limited therapy (FCR) arms over the first 36 months post registration. Analysis of FACT subscales showed PWB improved in the IR arm (0.37 ± 0.22) and declined in the FCR arm (-0.92 ± 0.39) from baseline to 3 months (p=0.004 for difference in PWB change between arms) but there was no significant difference between the two arms for change in PWB scores from baseline to 6 and 12 months. There were no significant differences between the two arms for change in FWB and FACT-Leu subscales from baseline to 3, 6 and 12 months. Conclusions: QOL improves in CLL patients age 70 and younger when treated in the frontline setting with IR or FCR. The improvement in QOL is maintained during continuous therapy with ibrutinib and there is no significant decline in QOL over time. Given the improvement in PFS and OS with IR over FCR seen in E1912, the results of this QOL analysis support the use of frontline ibrutinib in previously untreated younger CLL patients. Acknowledgement: This study was conducted by the ECOG-ACRIN Cancer Research Group (Peter J. O'Dwyer, MD and Mitchell D. Schnall, MD, PhD, Group Co-Chairs) and supported by the National Cancer Institute of the National Institutes of Health under award numbers: U10CA180794, U10CA180820, UG1CA189863, UG1CA190140, UG1CA232760, UG1CA233180, UG1CA233230, UG1CA233253, UG1CA233277, UG1CA233290, UG1CA233339, UG1CA189859, UG1CA233332. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Figure 1 Figure 1. Disclosures Kay: Oncotracker: Membership on an entity's Board of Directors or advisory committees; CytomX Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero Pharmaceuticals: Research Funding; Acerta Pharma: Research Funding; Behring: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees; Dava Oncology: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Targeted Oncology: Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Research Funding; Sunesis: Research Funding; Genentech: Research Funding; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding. O'Brien: Amgen, Astellas, Celgene, GlaxoSmithKline, Janssen Oncology, Aptose Biosciences Inc., Vaniam Group LLC, AbbVie, Alexion, Verastem, Juno Therapeutics, Vida Ventures, Autolus, Johnson and Johnson, Merck, Bristol Myers Squibb, NOVA Research Company, Eli Lill: Consultancy; Kite, Regeneron, Acerta, Caribou, Gilead, Pharmacyclics, TG Therapeutics, Pfizer, Sunesis: Research Funding. Coutre: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Data Safety Monitoring Committee, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta: Other: Data Safety Monitoring Committee, Research Funding. Barr: AstraZeneca: Consultancy; Gilead: Consultancy; Janssen: Consultancy; Genentech: Consultancy; Beigene: Consultancy; Bristol Meyers Squibb: Consultancy; Seattle Genetics: Consultancy; TG Therapeutics: Consultancy; Morphosys: Consultancy; Abbvie/Pharmacyclics: Consultancy. Cashen: Secura Bio, ADC Therapeutics: Consultancy. Mato: Adaptive Biotechnologies: Consultancy, Research Funding; DTRM BioPharma: Consultancy, Research Funding; Johnson and Johnson: Consultancy, Research Funding; Acerta/AstraZeneca: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; AstraZeneca: Consultancy; BeiGene: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; LOXO: Consultancy, Research Funding; MSKCC: Current Employment; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; Nurix: Research Funding; Janssen: Consultancy, Research Funding; Genmab: Research Funding. Erba: AbbVie Inc; Agios Pharmaceuticals Inc; Astellas; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Daiichi Sankyo Inc; Genentech, a member of the Roche Group; GlycoMimetics Inc; Incyte Corporation; Jazz Pharmaceuticals Inc; Kura Oncology; Nov: Other: Advisory Committee; AbbVie Inc: Other: Independent review committee; AbbVie Inc; Agios Pharmaceuticals Inc; ALX Oncology; Amgen Inc; Daiichi Sankyo Inc; FORMA Therapeutics; Forty Seven Inc; Gilead Sciences Inc; GlycoMimetics Inc; ImmunoGen Inc; Jazz Pharmaceuticals Inc; MacroGenics Inc; Novartis; PTC Therapeutics: Research Funding; AbbVie Inc; Agios Pharmaceuticals Inc; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Incyte Corporation; Jazz Pharmaceuticals Inc; Novartis: Speakers Bureau. Stone: Onconova: Consultancy; AbbVie: Consultancy; Boston Pharmaceuticals: Consultancy; Bristol Myers Squibb: Consultancy; Gemoab: Membership on an entity's Board of Directors or advisory committees; Elevate Bio: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Research Funding; Jazz: Consultancy; Syros: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Research Funding; Takeda: Consultancy; BerGen Bio: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Foghorn Therapeutics: Consultancy; Innate: Consultancy; Janssen: Consultancy; GlaxoSmithKline: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy, Research Funding; Actinium: Membership on an entity's Board of Directors or advisory committees; Syntrix/ACI: Membership on an entity's Board of Directors or advisory committees; Aprea: Consultancy; Celgene: Consultancy; Macrogenics: Consultancy. Litzow: Actinium: Research Funding; Amgen: Research Funding; AbbVie: Research Funding; Pluristem: Research Funding; Jazz: Other: Advisory Board; Omeros: Other: Advisory Board; Astellas: Research Funding; Biosight: Other: Data monitoring committee. Tallman: NYU Grand Rounds: Honoraria; Kura: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Biosight: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Orsenix: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Rafael Pharmaceuticals: Research Funding; Glycomimetics: Research Funding; Biosight: Research Funding; Orsenix: Research Funding; Abbvie: Research Funding; Mayo Clinic: Honoraria; UC DAVIS: Honoraria; Northwell Grand Rounds: Honoraria; NYU Grand Rounds: Honoraria; Danbury Hospital Tumor Board: Honoraria; Acute Leukemia Forum: Honoraria; Miami Leukemia Symposium: Honoraria; New Orleans Cancer Symposium: Honoraria; ASH: Honoraria; NCCN: Honoraria. Shanafelt: Genentech, Pharmacyclics: Research Funding. Wagner: Eli Lilly, Johnson & Johnson: Other: Spouse, previously held individual stocks;; Celgene-BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Athenex Inc: Consultancy.

While the majority of follicular lymphoma (FL) patients have an overall survival of nearly 2 decades, a subset of patients has a markedly inferior survival. Across randomized studies, 20% of patients will respond poorly to first-line chemoimmunotherapy and account largely for the early deaths in the larger FL population. This group represents the largest unmet need in FL, for which a precision approach to therapy must be developed. With the development of newer monoclonal antibodies, immunomodulatory agents, therapies targeting molecules downstream of the B-cell receptor and novel cellular strategies, non-cytotoxic treatment has the potential to improve outcomes for patients with early progressing FL. There are several validated clinical factors known to correlate with disease outcome in newly diagnosed FL including age, lactate dehydrogenase, β2-microglobulin and disease extent that have been incorporated in prognostic systems such as FLIPI and FLIPI2. More recently, genetic biomarkers have been identified, including MLL2, EZH2, IRF4, CREPPB, and EPHA7 which reflect the disease biology as well as the impact of the lymphoma microenvironment. The addition of these molecular aberrations to clinical factors has led to the development of the M7-FLIPI as well as a 23-gene score, improving risk prognostication for newly diagnosed FL patients. However, such systems have shown a limited ability to predict progression or relapse within 2 years of chemotherapy. As such, identification of these patients at diagnosis or prior to therapy is currently not possible. S1608 was developed to 1) enable identification of high-risk patients using clinical and molecular markers by validating the m7-FLIPI prognostic system and to 2) identify the novel therapeutic approaches most active in this population. This study is enrolling high-risk patients, refractory to chemoimmunotherapy, and in randomized fashion, comparing novel regimens against additional chemotherapy to identify the most active non-chemotherapeutic strategies for this population. Eligible patients must be 18 years or older with grade 1, 2 or 3a FL and have relapsed or progressed with 2 years of finishing their first course of chemoimmunotherapy. Previous chemotherapy must have been CHOP or bendamustine based. Patients are eligible regardless of anti-CD20 therapy used, whether radiation therapy had been administered and whether or not maintenance therapy was utilized. Note that patients are required to have evidence of progressive disease within 2 years but do not have to be registered within 2 years. These high-risk patients are randomized to 12 months of lenalidomide, umbralisib or additional chemotherapy (for 6 months), all combined with 12 months of obinutuzumab. The primary clinical endpoint is CR rate after 6 cycles, allowing responding patient to proceed with consolidative cellular therapies if desired by the treating physician. Biopsies from diagnosis and at the time of relapse as well as circulating tumor DNA are being collected to prospectively evaluate the m7-FLIPI and to identify additional predictive markers. S1608 is a collaborative effort amongst the SWOG, Alliance and ECOG-ACRIN cooperative groups. The study represents one of the only prospective efforts to characterize early progressing FL and the only randomized trial comparing treatment strategies for this group of follicular lymphoma patients most in need of alternative therapies. Funding: NIH/NCI/NCTN grants U10CA180888, U10CA180819, U10CA180820, U10CA180821; and TG Therapeutics, Inc. Figure 1 Figure 1. Disclosures Barr: Genentech: Consultancy; AstraZeneca: Consultancy; Morphosys: Consultancy; TG Therapeutics: Consultancy; Beigene: Consultancy; Abbvie/Pharmacyclics: Consultancy; Bristol Meyers Squibb: Consultancy; Seattle Genetics: Consultancy; Janssen: Consultancy; Gilead: Consultancy. Link: Novartis, Jannsen: Research Funding; MEI: Consultancy; Genentech/Roche: Consultancy, Research Funding. Flowers: Cellectis: Research Funding; Nektar: Research Funding; Takeda: Research Funding; TG Therapeutics: Research Funding; BeiGene: Consultancy; 4D: Research Funding; Karyopharm: Consultancy; Morphosys: Research Funding; Guardant: Research Funding; Bayer: Consultancy, Research Funding; Genmab: Consultancy; Eastern Cooperative Oncology Group: Research Funding; SeaGen: Consultancy; Genentech/Roche: Consultancy, Research Funding; Pharmacyclics/Janssen: Consultancy; Burroughs Wellcome Fund: Research Funding; AbbVie: Consultancy, Research Funding; Adaptimmune: Research Funding; Janssen: Research Funding; Iovance: Research Funding; Acerta: Research Funding; Kite: Research Funding; Allogene: Research Funding; EMD: Research Funding; Amgen: Research Funding; Celgene: Consultancy, Research Funding; Ziopharm: Research Funding; Novartis: Research Funding; Pfizer: Research Funding; Sanofi: Research Funding; National Cancer Institute: Research Funding; Xencor: Research Funding; Spectrum: Consultancy; Gilead: Consultancy, Research Funding; Epizyme, Inc.: Consultancy; Biopharma: Consultancy; Denovo: Consultancy; Cancer Prevention and Research Institute of Texas: CPRIT Scholar in Cancer Research: Research Funding; Pharmacyclics: Research Funding. Weigert: Janssen: Speakers Bureau; Epizyme: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding. Herrera: ADC Therapeutics: Consultancy, Research Funding; Tubulis: Consultancy; Karyopharm: Consultancy; Kite, a Gilead Company: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Gilead Sciences: Research Funding; Merck: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Takeda: Consultancy; Seagen: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding. Weinstock: SecuraBio: Consultancy; ASELL: Consultancy; Bantam: Consultancy; Abcuro: Research Funding; Verastem: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; AstraZeneca: Consultancy; Travera: Other: Founder/Equity; Ajax: Other: Founder/Equity. Leonard: ADC Therapeutics, AstraZeneca, Bayer, BMS/Celgene, Epizyme, Inc., Genmab, Gilead/Kite, Karyopharm, BMS/Celgene, Regeneron, MEI Pharma, Miltenyi, Roche/Genentech, Sutro: Consultancy; Roche/Genentech: Consultancy. Kahl: Abbvie, BeiGene, AstraZeneca, Acerta: Research Funding; Research to Practice: Speakers Bureau; Abbvie, ADCT, AstraZeneca, Beigene, Celgene, Teva, Janssen, MTEM, Bayer, InCyte, Adaptive, Genentech, Roche, MEI, KITE, TG Therapeutics, Epizyme, Takeda: Consultancy. Smith: Celgene, Genetech, AbbVie: Consultancy; Alexion, AstraZeneca Rare Disease: Other: Study investigator. Friedberg: Novartis: Other: DSMC ; Acerta: Other: DSMC ; Bayer: Other: DSMC .

Background: Continuous Bruton's tyrosine kinase (BTK) inhibition represents an effective and easily administered oral therapy for patients with CLL; however, it is not curative, can have serious side effects, and is expensive. Novel combinations may provide deep remissions allowing fixed duration therapy. The second generation BTK inhibitor acalabrutinib (ACALA) has demonstrated an improved safety profile compared to ibrutinib. Importantly, unlike ibrutinib, ACALA does not inhibit anti-CD20 monoclonal antibody dependent cellular phagocytosis (VanDerMeid et al, Cancer Immuno Res 2018). Using standard doses, rituximab (RTX) rapidly exhausts the finite innate immune system cytotoxic capacity (Pinney, et al Blood 2020) and also causes loss of cell membrane CD20 from CLL cells by trogocytosis. Previous studies have shown that high frequency low dose (HFLD) IV RTX (20mg/m 2 three times per week) was effective and limited loss of CD20 (Zent, et al Am J Hematol, 2014). Subcutaneous (SQ) RTX is FDA approved in CLL, has similar efficacy and pharmacokinetics, and can be self-administered. This phase II study tested the efficacy and tolerability of the combination of ACALA and HFLD RTX as initial treatment for patients with treatment-naïve CLL. Methods: Eligible patients were treated with 50mg RTX on day 1 and 3 of each week for six 28-day cycles. The first dose was administered IV over 2 hours. If tolerated, subsequent doses were SQ and could be self-administered at home by trained patients. ACALA 100mg BID therapy was initiated on cycle 1 day 8 for a minimum of 12 cycles. Treatment response was assessed during cycles 12 and 24. Patients achieving an iwCLL complete response (CR) with undetectable minimal residual disease (uMRD) by 6-color flow cytometry (£ 1:10 -4)at either time point could stop therapy. The primary objective was to determine the rate of iwCLL CR with a secondary endpoint of rate of uMRD. Results: 37 patients have been treated with a median follow-up of 14 months. Baseline demographics were male/female (22/15) and median age 67 years (range 40-78). High-risk genetic features included TP53 mutation (21.6%), del17p (13.5%), del 11q (16.2%), unmutated IGHV (62.2%), NOTCH1 mutation (21.6%) and SF3B1 mutation (10.8%). Grade 3/4 AEs occurring in ≥5% of patients were infections (13.5%), neutropenia (8.1%) and anemia (8.1%). No patients discontinued therapy due to AEs and there were no deaths on treatment. The most common (≥20%) AEs (all grades and all causality) were infusion-related reactions (62.1%), infections (56.8%) (upper respiratory infections in 29.7% of patients, urinary tract infections in 18.9%, COVID-19 pneumonia in 8.1%), fatigue (51.3%), anemia (51.3%), headache (43.2%), rash or other skin changes (32.4%), thrombocytopenia (29.7%), bruising (27.0%), and diarrhea (21.6%). Injection site reactions (8.1%) from SQ RTX were grade 1. Three patients contracted COVID-19 while on study during times of high community transmission prior to the availability of vaccines. Two required hospitalization, one contracted the virus following cycle 1 requiring a delay in RTX, and all patients remained on ACALA while COVID-19 positive. 27 patients have completed 12 cycles and been evaluated for response. All patients responded with 1 MRD+ CR, 20 partial responses (PR), and 6 PR with sustained lymphocytosis. 10 of these patients have completed 24 cycles and had a sustained PR. One patient with del17p and TP53 mutation had progressive disease after 25 cycles of therapy. All other patients remain on treatment per protocol. Conclusion: HFLD RTX and ACALA is a tolerable, effective and convenient therapy that could be the basis for regimens incorporating other novel agents. It is notable that three patients have contracted COVID-19 during the trial; however, none required intubation, and all remained on ACALA during their infection. This at-home combination markedly decreased patient infection risk during the COVID-19 pandemic. This regimen has the potential to enable RTX to be administered at facilities with limited medical IV infusion capacity which could be very useful in rural and economically disadvantaged areas. While all patients have responded to therapy, no patients to date have achieved an uMRD CR, suggesting that additional agents are required to allow for time-limited treatment. Disclosures Baran: AstraZeneca/Acerta: Research Funding. Friedberg: Novartis: Other: DSMC ; Acerta: Other: DSMC ; Bayer: Other: DSMC . Reagan: Kite, a Gilead Company: Consultancy; Genentech: Research Funding; Seagen: Research Funding; Curis: Consultancy. Casulo: Verastem: Research Funding; Genentech: Research Funding; BMS: Research Funding; Gilead: Research Funding. Zent: TG Therapeutics: Research Funding; Acerta/AstraZeneca: Research Funding. Barr: Morphosys: Consultancy; Janssen: Consultancy; Bristol Meyers Squibb: Consultancy; AstraZeneca: Consultancy; Genentech: Consultancy; TG Therapeutics: Consultancy; Beigene: Consultancy; Seattle Genetics: Consultancy; Abbvie/Pharmacyclics: Consultancy; Gilead: Consultancy.

Introduction: Alliance for Clinical Trials in Oncology A041202 is a NCI National Clinical Trials Network phase 3 study (NCT01886872) comparing BR (Arm 1) with ibrutinib (Arm 2) and the combination of ibrutinib plus rituximab (Arm 3) to determine whether ibrutinib-containing regimens are superior to chemoimmunotherapy (CIT) in terms of progression-free survival (PFS), and whether rituximab adds benefit to ibrutinib therapy. Initial results showed that ibrutinib-containing regimens had superior PFS to CIT, and that rituximab added to ibrutinib did not improve PFS over ibrutinib alone. Pts and Methods: Eligible pts on A041202 were those age ≥ 65 years with previously untreated, symptomatic CLL. Pts had a CrCl > 40 mL/min, bilirubin < 1.5 x ULN, and no significant life-limiting intercurrent illness or need for warfarin treatment. Pts were stratified on Rai stage, Zap-70 methylation performed centrally, and del(17)(p13.1) or del(11)(q22.3) by local interphase cytogenetics and were randomized 1:1:1 to each arm. Pts on Arm 1 who progressed could cross over to Arm 2. Here we present an updated analysis after the third planned interim analysis of Arms 2 and 3 versus Arm 1, and at the second planned interim analysis for Arms 3 vs 2. PFS and OS were estimated using the Kaplan-Meier method and corresponding hazard ratios with p-values were estimated using Cox proportional hazards models. These data encompass patient visits through April 2020 and were locked 15 February 2021. Results: Between 12/9/2013 and 5/16/2016, 547 pts were randomized (Arms 1: 183, 2: 182, and 3: 182). Baseline characteristics have previously been reported; briefly, median age was 71 years, 53% had unmethylated Zap-70, 61% were IGHV unmutated (performed in 66% of patients), 6% had del(17p) and 20% del(11q) by central FISH. Stimulated karyotype was performed centrally and revealed ≥ 3 abnormalities in 27%, and ≥ 5 in 11% of patients. With median follow-up of 55 months (mo), median PFS was 44 mo (95% CI 38-54) in Arm 1 and has not been reached in Arms 2 or 3 [Arm 2 vs 1 hazard ratio (HR): 0.36, 95% CI 0.26-0.52, p The benefit of ibrutinib regimens over CIT, with no additional benefit of rituximab when combined with ibrutinib, was consistent for all subgroups of patients defined by TP53 abnormalities, del(11q), complex karyotype, and IGHV (Figure 3). No significant interaction effects were observed between treatment arm and del(11q), complex karyotype, or IGHV. However, greater benefit of ibrutinib regimens over CIT was observed among patients with TP53 abnormalities than without (p Notable adverse events with ibrutinib include atrial fibrillation or flutter (afib) and hypertension (HTN). All grade afib was seen in 11 pts on BR (6%) and 67 pts on ibrutinib (19%). All grade HTN was seen in 95 pts on BR (54%) and 263 pts on ibrutinib (73%). Conclusions: This update of the A041202 trial continues to show that ibrutinib regimens prolong PFS over BR for older patients with treatment-naïve CLL. With longer follow-up, these benefits continue to be seen across subgroups, including those associated with higher risk disease. Strikingly, within the ibrutinib arms, there does not appear to be inferior PFS for patients with abnormalities in TP53, the highest risk feature seen in CLL, and a predictor of inferior PFS with ibrutinib in relapsed CLL. This differentiates ibrutinib (and perhaps BTKi in general) from other targeted therapy paradigms for treatment-naïve CLL. Similar to prior studies, rates of afib and HTN continue to increase with time on therapy. These data support the use of ibrutinib as initial therapy in CLL, and strengthen the rationale for use of ibrutinib for high risk disease. Support: U10CA180821, U10CA180882, U24CA196171, https://acknowledgments.alliancefound.org, Pharmacyclics, Inc Figure 1 Figure 1. Disclosures Woyach: Gilead Sciences Inc: Other: Data & Safety; AbbVie Inc, ArQule Inc, Janssen Biotech Inc, AstraZeneca, Beigene: Other: Advisory Committee; AbbVie Inc, Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Research Funding; AbbVie Inc, ArQule Inc, AstraZeneca Pharmaceuticals LP, Janssen Biotech Inc, Pharmacyclics LLC, an AbbVie Company,: Consultancy. Ruppert: Telios Pharma: Consultancy. Ding: Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; DTRM: Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees. Bartlett: ADC Therapeutics: Consultancy, Research Funding; Roche/Genentech: Consultancy; Seagen: Consultancy, Research Funding; Autolus: Research Funding; Bristol Myers Squibb: Research Funding; Celgene: Research Funding; Forty Seven: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Kite, a Gilead Company: Research Funding; Merck: Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding. Brander: Pfizer: Consultancy, Other: Biosimilars outcomes research panel; Genentech: Consultancy, Research Funding; Verastem: Consultancy; Juno Therapeutics/Celgene/Bristol Myers Squibb: Research Funding; LOXO: Research Funding; TG Therapeutics: Consultancy, Research Funding; MEI Pharma: Research Funding; NCCN: Other: panel member; ArQule/Merck: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; DTRM: Research Funding; BeiGene: Research Funding; AstraZeneca: Research Funding; Ascentage: Research Funding; ArQule: Research Funding; AbbVie: Consultancy, Other: informCLL registry steering committee, Research Funding; Novartis: Research Funding. Barr: Seattle Genetics: Consultancy; Bristol Meyers Squibb: Consultancy; AstraZeneca: Consultancy; Beigene: Consultancy; Genentech: Consultancy; Abbvie/Pharmacyclics: Consultancy; Gilead: Consultancy; Morphosys: Consultancy; TG Therapeutics: Consultancy; Janssen: Consultancy. Rogers: Pharmacyclics LLC: Consultancy; Innate Pharma: Consultancy; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy; Acerta Pharma: Consultancy; AbbVie Inc.: Consultancy, Research Funding; Janssen Pharmaceuticals, Inc: Research Funding; ovartis Pharmaceuticals Corporation: Research Funding. Parikh: Pharmacyclics, MorphoSys, Janssen, AstraZeneca, TG Therapeutics, Bristol Myers Squibb, Merck, AbbVie, and Ascentage Pharma: Research Funding; Pharmacyclics, AstraZeneca, Genentech, Gilead, GlaxoSmithKline, Verastem Oncology, and AbbVie: Membership on an entity's Board of Directors or advisory committees. Coutre: Acerta: Other: Data Safety Monitoring Committee, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Data Safety Monitoring Committee, Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Larson: Epizyme: Consultancy; Astellas: Consultancy, Research Funding; Gilead: Research Funding; CVS/Caremark: Consultancy; Takeda: Research Funding; Novartis: Research Funding; Rafael Pharmaceuticals: Research Funding; Cellectis: Research Funding. Erba: AbbVie Inc: Other: Independent review committee; AbbVie Inc; Agios Pharmaceuticals Inc; ALX Oncology; Amgen Inc; Daiichi Sankyo Inc; FORMA Therapeutics; Forty Seven Inc; Gilead Sciences Inc; GlycoMimetics Inc; ImmunoGen Inc; Jazz Pharmaceuticals Inc; MacroGenics Inc; Novartis; PTC Therapeutics: Research Funding; AbbVie Inc; Agios Pharmaceuticals Inc; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Incyte Corporation; Jazz Pharmaceuticals Inc; Novartis: Speakers Bureau; AbbVie Inc; Agios Pharmaceuticals Inc; Astellas; Bristol Myers Squibb; Celgene, a Bristol Myers Squibb company; Daiichi Sankyo Inc; Genentech, a member of the Roche Group; GlycoMimetics Inc; Incyte Corporation; Jazz Pharmaceuticals Inc; Kura Oncology; Nov: Other: Advisory Committee. Litzow: Jazz: Other: Advisory Board; Pluristem: Research Funding; Actinium: Research Funding; Amgen: Research Funding; Astellas: Research Funding; AbbVie: Research Funding; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee. Blachly: INNATE: Consultancy, Honoraria; KITE: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria. Owen: Genentech: Research Funding; Gilead: Honoraria; Janssen: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Roche: Honoraria, Research Funding; Merck: Honoraria; Servier: Honoraria; Incyte: Honoraria; Pharmacyclics: Research Funding. Abramson: Bristol-Myers Squibb Company: Consultancy, Research Funding; C4 Therapeutics: Consultancy; Morphosys: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; EMD Serono: Consultancy; Genmab: Consultancy; Bluebird Bio: Consultancy; Kymera: Consultancy; BeiGene: Consultancy; Incyte Corporation: Consultancy; Astra-Zeneca: Consultancy; Allogene Therapeutics: Consultancy; Seagen Inc.: Research Funding; AbbVie: Consultancy; Karyopharm: Consultancy; Genentech: Consultancy. Brown: Abbvie, Acerta/Astra-Zeneca, Beigene, Bristol-Myers Squibb/Juno/Celgene, Catapult, Eli Lilly, Genentech/Roche, Janssen, MEI Pharma, Morphosys AG, Nextcea, Novartis, Pfizer, Rigel: Consultancy; Invectys: Other: Data Safety Monitoring Committee Service; Gilead, Loxo/Lilly, SecuraBio, Sun, TG Therapeutics: Research Funding. Stone: Onconova: Consultancy; Syntrix/ACI: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Research Funding; Elevate Bio: Membership on an entity's Board of Directors or advisory committees; Boston Pharmaceuticals: Consultancy; Bristol Myers Squibb: Consultancy; Jazz: Consultancy; Arog: Consultancy, Research Funding; Gemoab: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy; Janssen: Consultancy; Innate: Consultancy; BerGen Bio: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Foghorn Therapeutics: Consultancy; AbbVie: Consultancy; Actinium: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Aprea: Consultancy; Syros: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; Agios: Consultancy, Research Funding; Celgene: Consultancy; Macrogenics: Consultancy. Byrd: Novartis, Trillium, Astellas, AstraZeneca, Pharmacyclics, Syndax: Consultancy, Honoraria; Vincerx Pharmaceuticals: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Newave: Membership on an entity's Board of Directors or advisory committees.

Background: Targeted therapies including ibrutinib, acalabrutinib and venetoclax (ven) have fundamentally changed the treatment of patients (pts) with chronic lymphocytic leukemia (CLL) leading to improved outcomes and durable remissions for many pts. However, CLL remains an incurable disease and a subset of pts will ultimately have progressive CLL following treatment with a covalent Bruton's Tyrosine Kinase inhibitor (cBTKi, e.g., ibrutinib, acalabrutinib) and ven. Data on efficacy of therapies for "double exposed" pts (i.e., pts exposed to both a cBTKi and ven) are extremely limited. Available approved options include chemoimmunotherapy (CIT) and phosphatidylinositol 3-kinase inhibitors (PI3Ki). However, the landmark clinical trials leading to the approvals of CIT and PI3Kis did not include pts treated with either cBTKi or ven (Furman et al. NEJM 2014, Flinn et al. Blood 2018). Non-covalent BTKis (ncBTKi) and chimeric antigen receptor (CAR) T-cell therapy have demonstrated promising clinical activity in double exposed CLL pts in clinical trials (Mato et al. Lancet 2021, Siddiqi et al. ASH 2020), but have not yet been compared to other novel agents or CIT in clinical trials or real-world analyses. We sought to describe outcomes of therapies for "double exposed" CLL pts. Methods: A retrospective, international, multicenter study was conducted. CLL pts were included if they received a cBTKi and ven and then a subsequent CLL-directed therapy. Therapies for Richter Transformation were excluded. Investigators identified pts at each site and collected data on demographics, disease characteristics, prior therapies, subsequent therapies and response assessments. Information was collected on up to three subsequent lines of therapy (LOT 1-3) per patient. The primary study endpoint was investigator-assessed overall response rate (ORR) per iwCLL 2018 criteria to therapies (LOT 1-3) following both cBTKi and ven. Kaplan-Meier method was used to estimate progression free survival (PFS). All other analyses were descriptive. Analyses were performed using STATA 17.0. Results: We report outcomes on 125 CLL pts who had prior cBTKi and ven and received a subsequent LOT. Baseline characteristics are presented in Table 1. ORR to prior cBTKi was 84.7% and 69.6% to prior ven. The most common reason for discontinuation of prior cBTKi and ven was CLL progression (71.1% cBTKi, 68.8% ven) followed by toxicity (25.6% cBTKi, 16.8% ven). Most common treatment strategies included ncBTKi (n=45), cBTKi (n=43), CIT (n=23), PI3Ki (n=24), alloSCT (n=17), CAR T-cell therapy (n=9), ven re-treatment (n=6), and other (n=44). ORR for selected agents following cBTKi and ven are presented in Table 2. ORR and PFS estimates were as follows: CAR T-cell therapy (85.7%, median PFS 4 months), alloSCT (76.5%, median PFS 11 months), ncBTKi (75.0%, median PFS not reached), PI3Ki (40.9%, median PFS 5 months), CIT (31.8%, median PFS 3 months) and ven re-treatment (ORR 40%, median PFS 14 months). ORR to cBTKi was 53.7%; however, median PFS for pts who discontinued a previous cBTKi for PD was 1 month versus 7 months for pts who discontinued due to AE. Figure 1 shows Kaplan-Meier estimated PFS for ncBTKi, PI3Ki, alloSCT, and CIT. Conclusions: In the largest series of "double exposed" CLL pts, several key findings warrant further investigation and discussion. Practice patterns are variable and no standard of care exists for CLL pts previously treated with a cBTKi and ven. Additionally, approved standard therapies including CIT combinations and PI3Kis yield poor outcomes with responses which are not durable. The low response rates and short PFS for PI3Ki and CIT call into question the use of these therapies as standard comparator arms in planned randomized trials. At this time, ncBTKi has a high ORR with durable responses (median PFS not reached). There appears to be a promising role for alloSCT in select, fit patients (ORR 76.5%, median PFS 11 months), and CAR T-cell therapy should be further explored in this population (ORR 85.7%, median PFS 4 months). Overall, this study highlights a continued unmet need for therapies for "double exposed" CLL pts. Figure 1 Figure 1. Disclosures Thompson: MJH Life Sciences: Honoraria; VJHemOnc: Honoraria; Curio Science: Honoraria. Roeker: Abbot Laboratories: Current equity holder in publicly-traded company; Pharmacyclics: Consultancy; Loxo Oncology: Consultancy; TG Therapeutics: Consultancy; AbbVie, AstraZeneca, Janssen, LOXO, Pharmacyclics, TG Therapeutics, Vaniam Group, Verastem: Consultancy; Pfizer: Consultancy, Research Funding. Coombs: LOXO: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; AstraZeneca: Honoraria; AbbVie: Honoraria; Genentech: Honoraria; MEI Pharma: Honoraria. Kamdar: AbbVie: Consultancy; TG Therapeutics: Research Funding; SeaGen: Speakers Bureau; ADC Therapeutics: Consultancy; Adaptive Biotechnologies: Consultancy; AstraZeneca: Consultancy; Celgene: Other; Celgene (BMS): Consultancy; Kite: Consultancy; KaryoPharm: Consultancy; Genentech: Research Funding; Genetech: Other. Pagel: Epizyme: Consultancy; Incyte/MorphoSys: Consultancy; BeiGene: Consultancy; Pharmacyclics/AbbVie: Consultancy; Actinium Pharmaceuticals: Consultancy; AstraZeneca: Consultancy; Gilead: Consultancy; Kite, a Gilead Company: Consultancy; MEI Pharma: Consultancy. Jacobs: MEI Pharma: Research Funding; Adaptive Biotechnologies: Consultancy; Genentech: Consultancy; TG Therapeutics: Research Funding, Speakers Bureau; Verastem: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; ADC Therapeutics: Consultancy; TeneoBio: Research Funding; AbbVie: Consultancy, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding, Speakers Bureau; Jannsen: Speakers Bureau; SecuraBio: Consultancy, Speakers Bureau. Hill: Gentenech: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Incyte/Morphysis: Consultancy, Honoraria, Research Funding; Celgene (BMS): Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Beigene: Consultancy, Honoraria, Research Funding; AstraZenica: Consultancy, Honoraria; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel Support, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding. Brander: AbbVie: Consultancy, Other: informCLL registry steering committee, Research Funding; AstraZeneca: Research Funding; BeiGene: Research Funding; ArQule: Research Funding; DTRM: Research Funding; LOXO: Research Funding; Verastem: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Juno Therapeutics/Celgene/Bristol Myers Squibb: Research Funding; Novartis: Research Funding; Ascentage: Research Funding; MEI Pharma: Research Funding; Genentech: Consultancy, Research Funding; NCCN: Other: panel member; Pfizer: Consultancy, Other: Biosimilars outcomes research panel; ArQule/Merck: Consultancy. Shadman: Mustang Bio, Celgene, Bristol Myers Squibb, Pharmacyclics, Gilead, Genentech, Abbvie, TG Therapeutics, Beigene, AstraZeneca, Sunesis, Atara Biotherapeutics, GenMab: Research Funding; Abbvie, Genentech, AstraZeneca, Sound Biologics, Pharmacyclics, Beigene, Bristol Myers Squibb, Morphosys, TG Therapeutics, Innate Pharma, Kite Pharma, Adaptive Biotechnologies, Epizyme, Eli Lilly, Adaptimmune , Mustang Bio and Atara Biotherapeutics: Consultancy. Ujjani: AbbVie: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Loxo: Research Funding; Adaptive Biotechnologies: Research Funding; Atara Bio: Consultancy; Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; TG Therapeutics: Honoraria; Gilead: Honoraria; ACDT: Honoraria; Kite, a Gilead Company: Honoraria. Battiato: Abbvie: Honoraria; Janssen: Honoraria. Rhodes: AbbVie, Genentech, Pharmacyclics, TG Therapeutics: Other: Consultant; Conquer Cancer Foundation Young Investigator Award: Other: Grant/Research Support. Fakhri: Loxo/Lilly: Research Funding. Barr: Morphosys: Consultancy; Gilead: Consultancy; Seattle Genetics: Consultancy; TG Therapeutics: Consultancy; Janssen: Consultancy; AstraZeneca: Consultancy; Beigene: Consultancy; Bristol Meyers Squibb: Consultancy; Abbvie/Pharmacyclics: Consultancy; Genentech: Consultancy. Portell: TG Therapeutics: Honoraria, Research Funding; SeaGen: Research Funding; Kite: Honoraria, Research Funding; Xencor: Research Funding; Abbvie: Research Funding; Pharmacyclics: Honoraria; Merck: Honoraria, Research Funding; BeiGene: Honoraria, Research Funding; Acerta/AstraZeneca: Research Funding; Aptitude Health: Honoraria; Targeted Oncology: Honoraria; Morphosys: Honoraria; Genentech: Research Funding; VelosBio: Research Funding. Lamanna: AbbVie: Consultancy, Research Funding; Verastem Oncology: Research Funding; BeiGene: Consultancy; Pharmacyclics: Consultancy; Celgene Corporation: Consultancy; Oncternal Therapeutics: Research Funding; Janssen Pharmaceuticals, Inc.: Consultancy; Gilead Sciences, Inc.: Consultancy; MingSight Pharmaceuticals, Inc.: Research Funding; Genentech, Inc.: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; TG Therapeutics, Inc: Research Funding; Juno Therapeutics, Inc.: Research Funding. Zelenetz: MorphoSys: Honoraria; Verastem: Honoraria; LFR: Other; Gilead: Honoraria, Research Funding; NCCN: Other; AstraZeneca: Honoraria; MEI Pharma: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Janssen: Honoraria; Gilead: Honoraria; Pharmacyclics: Honoraria; BMS/Celgene/JUNO: Honoraria, Other; Novartis: Honoraria; SecuraBio: Honoraria; Genentech/Roche: Honoraria, Research Funding; MethylGene: Research Funding; Amgen: Honoraria; Beigene: Honoraria, Other, Research Funding. Schuster: Abbvie: Consultancy, Research Funding; Acerta Pharma: Consultancy; AstraZeneca: Consultancy; Adaptive Biotechnologies: Research Funding; BeiGene: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; DTRM: Research Funding; Genetech: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Incyte: Research Funding; Juno Theraputics: Consultancy, Research Funding; Loxo Oncology: Consultancy; Merck: Research Funding; Nordic Nanovector: Consultancy; Novartis: Consultancy, Honoraria, Patents & Royalties, Research Funding; Pharmaclcyclics: Research Funding; Tessa Theraputics: Consultancy; TG Theraputics: Research Funding. Eyre: Secura Bio: Consultancy, Honoraria; Loxo Oncology: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Honoraria, Research Funding; Incyte: Consultancy; Beigene: Honoraria, Research Funding; Roche: Consultancy, Honoraria; Gilead/KITE: Honoraria, Other: Travel support for conferences, Research Funding, Speakers Bureau; Janssen: Honoraria; Abbvie: Consultancy, Honoraria, Other: Travel to conferences. Mato: MSKCC: Current Employment; AstraZeneca: Consultancy; Genmab: Research Funding; LOXO: Consultancy, Research Funding; Adaptive Biotechnologies: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Johnson and Johnson: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; BeiGene: Consultancy, Research Funding; DTRM BioPharma: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Acerta/AstraZeneca: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Nurix: Research Funding.

Background Primary bone diffuse large B cell lymphoma (DLBCL) is a variant of extranodal non-Hodgkin lymphoma (NHL) that is relatively rare, accounting for 3-15% of extranodal NHL and less than 1% of all NHL. Patients often present with pain and swelling or pathologic fracture of the affected area of the skeleton, and B symptoms are often less prevalent. Many cases are limited stage at presentation. Patients are usually treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) or similar induction therapy. Based on older studies showing improved outcomes associated with the addition of radiation (many completed prior to the rituximab era), patients often still receive combined-modality therapy today. However, it remains unknown whether consolidative radiation therapy (RT) confers additional benefit following rituximab-based chemoimmunotherapy (CIT) induction. We sought to address this question in a multicenter retrospective study. Methods We conducted a retrospective analysis of outcomes in a modern cohort of patients who underwent treatment for primary bone DLBCL using chemotherapy regimens in the rituximab era either with or without consolidative RT. Data was collected from 13 academic medical centers in the U.S., with patients treated between 2005 and 2019. Patients were identified using each institution's hematologic malignancy registries. Analysis was limited to patients with primary bone DLBCL, with stage I-II disease (primary site +/- locoregional lymph nodes) that could be encompassed in a radiation field. Patients who received CIT alone or CIT followed by RT were included. Treatment selection was at the treating physician's discretion. Electronic medical records were reviewed for: demographics, chemotherapy regimens, radiation treatments, and PET scan data. Local IRB approval was obtained at sites. All data was distributed in a de-identified fashion. The primary outcomes were overall survival (OS), and relapse-free survival (RFS). Secondary outcomes included: response after induction CIT induction and the need for additional therapies. Chi-square test analysis was used to compare categorical variables and the Wilcoxon rank-sum test was used for continuous and ordinal measures. Survival curves were estimated using the Kaplan-Meier method and compared between groups via the log-rank test. Multi-variable analysis (MVA) for OS and RFS was performed using RT vs no RT, PET status post CIT (negative vs positive) and rituximab in induction (Y/N) as variables. Results A total of 127 patients were included: 91 who received CIT and radiation (RT group), and 36 who received CIT alone (no RT group). The median age of patients at diagnosis in the RT group and no RT group was 58.5 and 57.0, respectively. For CIT, the majority of patients received R-CHOP (84%). Despite focusing on 2005-2019, a small percentage of patients (5 - 14%) in each group (RT and no RT) did not receive rituximab with their induction therapy. The OS at 10 years was 74.5% in the RT group and 86.5% in the no RT group (p = 0.29). The RFS at 10 years was 70.9% in the RT group and 78.2% in the no RT group (p = 0.85). Among the 91 patients who received RT, 67 (77.0%) received a dose of 36 Gy or higher. There was no difference in OS (p = 0.63) or RFS (p = 0.90) in patients who received > 36 Gy vs < 36 Gy of radiation. On MVA for OS, RT was not associated with improved OS, although rituximab as part of induction was (p = 0.048). On MVA for RFS, neither RT nor rituximab were associated with improved RFS. For rituximab the trend was in the direction of rituximab benefit (p = 0.11). Conclusion Our results demonstrate that, in the rituximab era, patients with limited stage primary bone DLBCL have excellent outcomes overall. In this study, neither RFS or OS appeared to be improved with the addition of consolidative RT. Rituximab, however, was associated with improved OS on MVA. Outcomes do not appear to differ based on the dose of RT (> 36 Gy vs < 36 Gy). Our data suggests that RT may have less benefit for primary bone DLBCL in the rituximab era, although it is possible that a subset of patients may benefit from consolidative radiation therapy. A larger data set would likely be needed to evaluate this. We plan to present data regarding PET responses at the meeting. Figure 1 Figure 1. Disclosures Lunning: Acrotech: Consultancy; AstraZeneca: Consultancy; Myeloid Therapeutics: Consultancy; Janssen: Consultancy; Morphosys: Consultancy; Novartis: Consultancy; Karyopharm: Consultancy; Kyowa Kirin: Consultancy; Verastem: Consultancy; Kite, a Gilead Company: Consultancy; Celgene, a Bristol Myers Squibb Co.: Consultancy; Spectrum: Consultancy; Daiichi-Sankyo: Consultancy; Beigene: Consultancy; Legend: Consultancy; ADC Therapeutics: Consultancy; TG Therapeutics: Consultancy; AbbVie: Consultancy. Cashen: Secura Bio, ADC Therapeutics: Consultancy. Bartlett: Autolus: Research Funding; Bristol Myers Squibb: Research Funding; Celgene: Research Funding; Forty Seven: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Kite, a Gilead Company: Research Funding; Merck: Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding; Seagen: Consultancy, Research Funding; Roche/Genentech: Consultancy; ADC Therapeutics: Consultancy, Research Funding. Caimi: XaTek: Patents & Royalties: Royalties from patents (wife); Amgen Therapeutics.: Consultancy; ADC Theraputics: Consultancy, Research Funding; Genentech: Research Funding; TG Therapeutics: Honoraria; Seattle Genetics: Consultancy; Verastem: Consultancy; Kite Pharmaceuticals: Consultancy. Rodgers: MJH Lifesciences: Consultancy. Barr: Morphosys: Consultancy; Gilead: Consultancy; Genentech: Consultancy; TG Therapeutics: Consultancy; Janssen: Consultancy; Beigene: Consultancy; Bristol Meyers Squibb: Consultancy; Seattle Genetics: Consultancy; AstraZeneca: Consultancy; Abbvie/Pharmacyclics: Consultancy. Epperla: Verastem: Speakers Bureau; Beigene: Speakers Bureau; Karyopharm: Other: Ad Board; Genzyme: Honoraria. Hill: AstraZenica: Consultancy, Honoraria; Celgene (BMS): Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel Support, Research Funding; Pfizer: Consultancy, Honoraria; Gentenech: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy, Honoraria; Incyte/Morphysis: Consultancy, Honoraria, Research Funding; Beigene: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding. Karmali: BMS/Celgene/Juno: Consultancy, Research Funding; Epizyme: Consultancy; Karyopharm: Consultancy; Janssen/Pharmacyclics: Consultancy; Morphosys: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; BeiGene: Consultancy, Speakers Bureau; EUSA: Consultancy; Takeda: Research Funding; Genentech: Consultancy; Roche: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding, Speakers Bureau. Portell: Acerta/AstraZeneca: Research Funding; Xencor: Research Funding; Abbvie: Research Funding; Aptitude Health: Honoraria; Morphosys: Honoraria; Targeted Oncology: Honoraria; SeaGen: Research Funding; BeiGene: Honoraria, Research Funding; Merck: Honoraria, Research Funding; Pharmacyclics: Honoraria; Kite: Honoraria, Research Funding; TG Therapeutics: Honoraria, Research Funding; Genentech: Research Funding; VelosBio: Research Funding. Fenske: Pharmacyclics: Consultancy; AstraZeneca: Speakers Bureau; Servier Pharmaceuticals: Consultancy; MorphoSys: Consultancy; Adaptive Biotechnologies: Consultancy; KaryoPharm: Consultancy; CSL Therapeutics: Consultancy; TG Therapeutics: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Sanofi: Speakers Bureau; Seattle Genetics: Speakers Bureau; Biogen: Consultancy; ADC Therapeutics: Consultancy; Kite (Gilead): Speakers Bureau; Beigene: Consultancy; AbbVie: Consultancy.

Introduction: The receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a transmembrane protein that is overexpressed in multiple cancers, including hematological malignancies. Zilovertamab vedotin (MK-2140) is an antibody -drug conjugate comprising a humanized IgG1 monoclonal antibody, a proteolytically cleavable linker, and the antimicrotubule cytotoxic agent monomethyl auristatin E (MMAE). Preclinical evidence demonstrated the cytotoxicity of zilovertamab vedotin in hematologic cell lines. This first human phase 1 dose escalation study (NCT03833180) evaluated the safety and efficacy of zilovertamab vedotin at various doses in patients with relapsed/refractory hematologic malignancies. Methods: Eligible patients aged ≥18 years with an Eastern Cooperative Oncology Group Performance Status of 0-2 and histological diagnosis of chronic lymphocytic leukemia/small lymphocytic leukemia, lymphoplasmacytic lymphoma/Waldenström macroglobulinemia, acute lymphoid leukemia, acute myeloid leukemia, or non-Hodgkin lymphoma (NHL; mantle cell lymphoma [MCL], follicular lymphoma, marginal zone lymphoma, diffuse large B-cell lymphoma [DLBCL], Richter transformation, Burkitt lymphoma, and T-cell-NHL) were enrolled. Participants received zilovertamab vedotin intravenously at starting doses of 0.50 mg/kg (up to 2.5 mg/kg) on day 1 every 3 weeks (Q3W) (Schedule 1), 1.0 mg/kg (planned up to 2.25 mg/kg) on day 1 and 8 Q3W (Schedule 2), or 1.0 mg/kg (planned up to 2.25 mg/kg) on days 1, 8, and 15 Q4W (Schedule 3) using an accelerated plus 3+3 dose escalation design. The primary end point was determination of the maximum tolerated dose (MTD). Secondary end points included safety, objective response rate (ORR), and duration of response (DOR). We present data for participants with NHL enrolled in Schedule 1. Results: A total of 51 patients were enrolled in Schedule 1 (starting dose 0.5 [n=1], 1.00 [n=3], 1.50 [n=3], 2.00 [n=3], 2.25 [n=11], or 2.50 [n=30] mg/kg) as of the data cutoff of May 18, 2021. Median (range) age of patients was 70 (44-91) years, 54.9% of patients were male, 49.0% had an ECOG PS of 0, and 41/51 (80%) were diagnosed with NHL; 13/51 (25.5%) were diagnosed with DLBCL and 17/51 (33.3%) were diagnosed with MCL. Enrollment in Schedules 2 and 3 is currently ongoing. The MTD for Schedule 1 was determined to be 2.5 mg/kg. Any-cause adverse events (AEs) occurred in 48 patients (94.1%), most commonly (≥30%) nausea (45.1%), fatigue (45.1%), peripheral neuropathy (41.2%), diarrhea (37.3%), dizziness (35.3%), and neutrophil count decrease (33.3%). Grade ≥3 AEs occurred in 33 (64.7%) patients, most commonly (≥5%) neutrophil count decrease (29.4%), hemoglobin decrease (15.7%), febrile neutropenia (7.8%), peripheral neuropathy (7.8%), platelet count decrease (7.8%), diarrhea (5.9%), lipase increase (5.9%), and pneumonia (5.9%). One patient died due to acute respiratory failure; however, it was not considered treatment-related by the investigator. A total of 7 (13.7%) patients permanently discontinued due to an AE and 18 (35.3%) had treatment interrupted or reduced due to an AE. Treatment-related AEs occurred in 36 patients (70.6%), most commonly (≥20%) peripheral neuropathy (41.2%), fatigue (37.3%), neutrophil count decrease (29.4%), nausea (27.5%), and diarrhea (21.6%); 24 patients (47.1%) experienced a grade ≥3 treatment-related AE. For Schedule 1, ORR was 36.6% (15/41 [95% CI: 22.1%-53.1%]) among all participants with NHL, with 5 having a complete response (CR) and 10 having a partial response (PR). ORR was 38.5% (95% CI: 13.9%-68.4%) for the 13 patients in the NHL group who had DLBCL; 3 patients had a CR and 2 patients had a PR. ORR was 52.9% (95% CI: 27.8%-77.0%) for the 17 patients in the NHL group who had MCL; 2 patients had a CR and 7 patients had a PR. Median (range) DOR was 7.8 months (2.1-17.6+ months) among all participants in Schedule 1 with NHL who achieved a response. Conclusion: These data suggest that targeting the ROR1 pathway with zilovertamab vedotin is associated with a tolerable safety profile and promising antitumor activity in patients with relapsed/refractory NHL. Disclosures Wang: Anticancer Association: Honoraria; Dava Oncology: Honoraria; BioInvent: Research Funding; Bayer Healthcare: Consultancy; Hebei Cancer Prevention Federation: Honoraria; Lilly: Research Funding; Scripps: Honoraria; Kite Pharma: Consultancy, Honoraria, Research Funding; Juno: Consultancy, Research Funding; CAHON: Honoraria; InnoCare: Consultancy, Research Funding; Molecular Templates: Research Funding; Pharmacyclics: Consultancy, Research Funding; Oncternal: Consultancy, Research Funding; Miltenyi Biomedicine GmbH: Consultancy, Honoraria; Genentech: Consultancy; Newbridge Pharmaceuticals: Honoraria; VelosBio: Consultancy, Research Funding; Celgene: Research Funding; Physicians Education Resources (PER): Honoraria; The First Afflicted Hospital of Zhejiang University: Honoraria; OMI: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Loxo Oncology: Consultancy, Research Funding; BeiGene: Consultancy, Honoraria, Research Funding; DTRM Biopharma (Cayman) Limited: Consultancy; Chinese Medical Association: Honoraria; AstraZeneca: Consultancy, Honoraria, Research Funding; Clinical Care Options: Honoraria; Mumbai Hematology Group: Honoraria; Moffit Cancer Center: Honoraria; BGICS: Honoraria; CStone: Consultancy; Imedex: Honoraria; Epizyme: Consultancy, Honoraria; Acerta Pharma: Consultancy, Honoraria, Research Funding. Mei: Janssen: Honoraria; EUSA: Honoraria; Sanofi-Genzyme: Honoraria; Morphosys: Honoraria; TG Therapeutics: Other: Institution: Research Grant/Funding; Epizyme: Other: Institution: Research Grant/Funding; BMS: Other: Institution: Research Grant/Funding; Beigene: Other: Institution: Research Grant/Funding; Incyte: Other: Institution: Research Grant/Funding. Barr: Beigene: Consultancy; Gilead: Consultancy; Morphosys: Consultancy; TG Therapeutics: Consultancy; AstraZeneca: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Abbvie/Pharmacyclics: Consultancy; Bristol Meyers Squibb: Consultancy; Seattle Genetics: Consultancy. Furman: Acerta/AstraZeneca: Consultancy; Janssen: Consultancy, Honoraria; Beigene: Consultancy; Genentech: Consultancy; Incyte: Consultancy; Loxo Oncology: Consultancy; Abbvie: Consultancy, Honoraria, Other: Expert testimony; AstraZeneca: Honoraria; Sunesis: Consultancy; Oncotracker: Consultancy; Pharmacyclics: Consultancy; TG Therapeutics: Consultancy; Verastem: Consultancy; Morphosys: Consultancy; Sanofi: Consultancy; X4 Pharmaceuticals: Consultancy. Patel: TG Therapeutics: Consultancy, Speakers Bureau; Abbvie: Consultancy; Sunesis Pharmaceuticals: Research Funding; Juno Pharmaceuticals: Consultancy; MEI Pharma: Consultancy, Research Funding; Kite: Consultancy, Research Funding, Speakers Bureau; Millenium/Takeda: Research Funding; Pharmacyclics/Janssen: Consultancy, Research Funding, Speakers Bureau; Morphosys: Consultancy; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; Genentech/Roche: Consultancy, Research Funding, Speakers Bureau; Trillium Therapeutics: Research Funding; BeiGene: Consultancy; Aptevo Therapeutics: Research Funding; Fate Therapeutics: Research Funding; Xencor: Research Funding; Velos Bio: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding, Speakers Bureau; Curis, Inc: Research Funding; Celgene: Consultancy, Research Funding, Speakers Bureau. Thompson: AbbVie: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding; Genentech: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding; Adaptive Biotechnologies: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding, Expert Testimony; Pharmacyclics: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding; Janssen: Consultancy, Honoraria; Gilead: Other: Institution: Advisory/Consultancy, Honoraria; Amgen: Other: Institution: Honoraria, Research Grant/Funding. Choi: Abbvie: Other: Institution: Research Grant/Funding; Pharmacyclics: Other: Institution: Research Grant/Funding; Oncternal: Other: Institution: Research Grant/Funding; Velosbio: Other: Institution: Research Grant/Funding; Merck: Other: Institution: Research Grant/Funding; Geron: Other: Institution: Research Grant/Funding. Zhu: Merck & Co., Inc.: Current Employment. Chakraborty: Merck & Co., Inc.: Current Employment, Other: Current Stockholder. Marinello: Merck & Co., Inc.: Current Employment, Other: Current Stockholder. Spurgeon: Ionis: Other: Institution: Research Grant/Funding; Gilead Sciences: Other: Institution: Research Grant/Funding; Bristol Myers Squibb: Other: Institution: Research Grant/Funding; BeiGene: Other: Institution: Research Grant/Funding; AstraZeneca: Other: Institution: Research Grant/Funding; Acerta Pharma: Other: Institution: Research Grant/Funding; Pharmacyclics: Consultancy; Janssen: Consultancy, Other: Institution: Research Grant/Funding; Genentech: Consultancy, Other: Institution: Research Grant/Funding; Karyopharm: Consultancy; Velos Bio: Consultancy, Other: Institution: Research Grant/Funding; Merck & Co., Inc.: Other: Institution: Research Grant/Funding; Fred Hutchinson Cancer Research Center: Other: Data Safety Monitoring Board.

Ibrutinib, an oral inhibitor of Bruton's tyrosine kinase (BTK), at a once-daily dose of 420 mg achieved BTK active-site occupancy in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) that was maintained at 24 hours. It is unknown if intermittent interruption of ibrutinib therapy contributes to altered clinical outcomes. We therefore evaluated the effect of ibrutinib dose adherence on patient outcomes in the phase 3 RESONATE trial. The overall mean dose intensity (DI) was 95% with median treatment duration of similar to 9 months. Pharmacokinetic assessment of ibrutinib exposure at 420-mg dose suggested similar exposure regardless of patient weight or age. As assessed by independent review committee, patients with higher DI experienced longer median progression-free survival (PFS) compared with those with lower DI regardless of del17p and/or TP53 status. Of 79 patients requiring a drug hold, treatment was restarted at the original dose in 73 (92%) patients. Mean duration of a missed-dose event was 18.7 days (range, 8-56). Patients missing >= 8 consecutive days of ibrutinib had a shorter median PFS vs those missing

Older patients with hematologic malignancies are underrepresented on prospective clinical trials relative to the incidence of disease in this group (Kanapuru et al, 2020). There are few studies in diffuse large B-cell lymphoma (DLBCL) focused specifically on older patients. Rituximab and dose attenuated cyclophosphamide, doxorubicin, vincristine, and prednisone (R-miniCHOP) has been studied on a prospective trial in fit patients aged 80 years and older. Seventy-two percent of patients on this study completed 6 cycles of R-miniCHOP. The overall response rate (ORR) was 73%, and the 2-year progression free survival (PFS) was 47% (Peyrade et al, 2011). Novel regimens are needed to improve upon the efficacy of therapy while preserving tolerability. Brentuximab vedotin (BV) has demonstrated activity in relapsed and refractory DLBCL (Jacobsen et al, 2015) as well as in combination with chemoimmunotherapy (Svoboda, 2020). This study evaluates the feasibility of BV with dose attenuated chemoimmunotherapy. Methods: Patients with both CD30 positive (cut off 1%) and CD30 negative DLBCL aged 75 years and older were enrolled on the study. Patients received six, 3-week cycles of BV 1.8 mg/kg, cyclophosphamide 400 mg/m2, doxorubicin 25 mg/m2, vincristine 1 mg and prednisone 40 mg/m2 days 1-5 (BV R-miniCHP). For the first cycle patients received BV and prednisone as a prephase starting one week prior to cycle 1. All patients received pegfilgrastim. All patients underwent geriatric assessments at screening, following prephase and at the end of treatment. The primary endpoint was feasibility of this regimen in older patients. The regimen was considered feasible if 71% of patients completed 6 cycles of treatment with a 90% confidence interval (CI)=(58.0, 90.6%). Secondary endpoints included toxicity, ORR and complete response (CR) evaluated by positron emission tomography, PFS and overall survival (OS). Response assessments used the Lugano Criteria (Cheson et al, 2014). PFS and OS were estimated using the Kaplan-Meier method. Results: Twenty-two patients were enrolled and started prephase with BV and prednisone. Their baseline characteristics are summarized in the table. Seventy-seven percent (17/22) of patients completed 6 cycles of BV R-miniCHP. Reasons for not completing treatment included progressive disease in 2 patients, myocardial infarction, fatigue, and an unrelated injury in 1 patient each. Twenty-one patients were evaluable for response. ORR was 86% (18/21) in all patients, with 67% (14/21) achieving CR. In CD30 positive patients the ORR was 80% (8/10) and the CR rate was 70% (7/10). In CD30 negative patients the ORR was 91% (10/11) and the CR rate was 64% (7/11). With a median follow up of 23 months, median OS and PFS (figure) were not reached. The 2-year PFS was 60.6%, 90% CI=(40.0%, 76.1%), and the 2-year OS was 73.9%, 90% CI=(52.4%, 86.8%). The most common adverse events (AEs) were fatigue (82%), anemia (50%), diarrhea (50%), dysgeusia (45%) and peripheral sensory neuropathy (45%). Grade ≥3 AEs seen in more than 2 patients included neutropenia (23%), fatigue (18%), pneumonia (18%), hypoxia (14%), thrombocytopenia (9%) and thromboembolism (9%). Grade ≥3 peripheral sensory neuropathy was seen in 9% of patients. There were two deaths in patients receiving study treatment. These included a myocardial infarction related to treatment, and a bowel obstruction secondary to disease progression. Three other patients have died in follow up with 2 secondary to disease progression and 1 due to an unrelated event. Conclusions: The study met its primary feasibility endpoint with 77% of patients completing 6 cycles of therapy. This regimen was delivered safely in this population and toxicities were consistent with those reported in larger prospective studies with R-miniCHOP or ofatumumab and miniCHOP (Peyrade et al, 2011; Peyrade et al 2017). Peripheral neuropathy is a key AE of interest given the inclusion of BV and while nearly half of patients experienced some peripheral neuropathy, it was severe in only 9% of pts. The ORR and CR rate, as well as the 2-year PFS compare favorably to other prospective studies in a population that included patients with high clinical risk, histologic transformation, and double hit lymphoma. BV and R-miniCHP may be a feasible regimen in older patients, and warrants further study based on these preliminary data demonstrating clinical activity and tolerability. Figure 1 Disclosures Reagan: Seattle Genetics: Research Funding; Curis: Consultancy; Kite, a Gilead Company: Consultancy. Portell:Xencor: Research Funding; Roche/Genentech: Consultancy, Research Funding; Infinity: Research Funding; TG Therapeutics: Research Funding; AbbVie: Research Funding; Pharmacyclics: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Bayer: Consultancy; BeiGene: Consultancy, Research Funding; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding. Barr:Gilead: Consultancy; Verastem: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Genentech: Consultancy; AstraZeneca: Consultancy, Research Funding; Janssen: Consultancy; Seattle Genetics: Consultancy; Celgene: Consultancy; Morphosys: Consultancy; TG therapeutics: Consultancy, Research Funding; Merck: Consultancy. Friedberg:Acerta Pharma - A member of the AstraZeneca Group, Bayer HealthCare Pharmaceuticals.: Other; Roche: Other: Travel expenses; Kite Pharmaceuticals: Research Funding; Seattle Genetics: Research Funding; Portola Pharmaceuticals: Consultancy; Astellas: Consultancy; Bayer: Consultancy.

Introduction Indolent Non-Hodgkin lymphomas (NHL) comprise a heterogeneous group of diseases including marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma (LPL), small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL), and follicular lymphoma (FL). These compose a heterogenous group of disorders that frequently measures survival in years due to the long natural history of these diseases. Frequency and morbidity of cardiac arrhythmias in patients with indolent lymphoma is unknown, but recent observations note that arrhythmias are an increasing problem. Due to advances in treatment for indolent NHL with emergence of novel therapeutics, combined with an aging population and a long natural history, understanding of arrhythmia burden in indolent lymphoma is an area of research with important implications for patients undergoing active treatment as well as for long term lymphoma survivors. Methods Adult patients 18 years or older with indolent NHL treated at the University of Rochester Wilmot Cancer Institute between 2013-2019 were included in the Cardio-Oncology Lymphoid Malignancies Database and analyzed. The primary objective of this study was to define the rate of arrhythmic events and sudden cardiac death in patients with indolent lymphoma during treatment. Cardiac arrhythmias including ventricular arrhythmias (VT/VF), atrial arrhythmias (atrial fibrillation (afib), flutter, SVT and atrial tachycardia), and bradyarrhythmias were identified using ICD-10 codes. Kaplan-Meier survival analysis was used to assess cumulative probability of arrhythmia. Results There were nine hundred and eighteen patients who were diagnosed with indolent lymphoma. Diagnoses included: CLL, N=414; FL, N=284; MZL, N=144; LPL, N=76. Median age was 64, and 43% were female. There were 383 (42%) patients who received treatment. Treatments were classified as chemotherapy, targeted therapy, monoclonal antibodies/immunotherapy, and combination therapy. There were no significant differences in baseline characteristics between treated and never treated patients. At the time of diagnosis, 277 patients (30%) had hypertension, 101 (11%) had prior history of arrhythmia. During median follow up of 24 months, 168 patients (18%) developed a new or recurrent arrhythmia based on ICD-10 codes documented in the electronic medical record. Sixty-three out of one hundred sixty-eight patients had both prior history of and recurrence of arrhythmia, while one hundred five had a new diagnosis of arrhythmia. Afib was the most common arrhythmia, noted in 81 patients (9%). At 6 months from diagnosis, cumulative probability of developing any arrhythmia was 8% (Figure 1). Of all arrhythmias, 89/168 (53%) occurred in SLL/CLL, 35/168 (21%) in FL, 17/168 (10%) in LPL, 27/168 (16%) in MZL. Arrhythmias on treatment occurred in 4/95 patients receiving chemotherapy alone (4.2%), 12/95 patients receiving monoclonal antibodies/immunotherapy (12.6%), and 28/95 patients receiving targeted therapy (29.4%). Most arrhythmias (51/95; 53.6%) occurred in patients receiving combination therapy (chemoimmunotherapy or targeted/immunotherapy). Overall, there were 80 (9%) deaths. Ten deaths were related to cardiovascular diseases; of which 8/10 (80%) were from sudden cardiac death. Conclusions This real-world cohort demonstrates that patients with indolent lymphoma could have an increased risk of cardiac arrhythmias that is increased by treatment. Afib was the most common arrhythmia identified in this study and appears increased compared to the incidence in the general age matched population (1-1.8 per 100 person-years). Surprisingly, of 80 deaths, 8 (10%) were attributed to sudden cardiac death. This data set contributes important information that can help identify patients at increased risk of cardiovascular morbidity and mortality that can impact treatment. Prospective monitoring in these patients may better define the incidence and associated risks of arrhythmias. Future directions will focus on risk factors for arrhythmias and developing an approach to prevent and treat arrhythmias in this patient population. Updated results will be presented at the meeting. Disclosures Zent: Acerta / Astra Zeneca: Research Funding; TG Therapeutics, Inc: Research Funding; Mentrik Biotech: Research Funding. Barr:Janssen: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy; Celgene: Consultancy; Seattle Genetics: Consultancy; TG therapeutics: Consultancy, Research Funding; Morphosys: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy, Research Funding; Merck: Consultancy; Genentech: Consultancy. Reagan:Kite, a Gilead Company: Consultancy; Seattle Genetics: Research Funding; Curis: Consultancy. Friedberg:Seattle Genetics: Research Funding; Roche: Other: Travel expenses; Bayer: Consultancy; Astellas: Consultancy; Acerta Pharma - A member of the AstraZeneca Group, Bayer HealthCare Pharmaceuticals.: Other; Kite Pharmaceuticals: Research Funding; Portola Pharmaceuticals: Consultancy.

Background: Despite the effectiveness of novel agents in treating CLL, prolonged single agent use can lead to drug resistance, toxicity, challenges with adherence, and considerable financial burden. Combinations may provide deeper prolonged remissions using defined treatment durations. Umbralisib (Umbra) is a novel and highly specific PI3Kδ/CK1ε dual inhibitor, while ublituximab (Ubli) is a glycoengineered monoclonal antibody targeting a unique epitope on CD20. A randomized Phase 3 study of the Umbra + Ubli (U2) combination in patients (pts) with treatment naïve and previously treated CLL, UNITY-CLL, was recently determined to have met its primary endpoint at a pre-planned interim analysis. Integrating the BCL2 inhibitor venetoclax (Ven) into the U2 backbone is hypothesized to reduce the risk of acquired drug resistance (Choudhary, Cell Death Dis 2015), achieve higher levels of undetectable minimal residual disease (MRD), and reduce the risk of tumor lysis syndrome (TLS). Phase 1 results established the recommended Phase 2 doses to be: Umbra 800 mg QD; Ubli 900 mg and Ven 400 mg QD (Barr et al., ASH 2019). The Phase 2 component evaluated the safety, efficacy and MRD negativity rates in relapsed or refractory CLL pts. Methods: In Phase 2, pts received three cycles of Umbra 800 mg QD along with Ubli 900 mg, administered weekly during cycle 1 (Day 1/2 split 150/750), then on Day 1 in cycles 2 through 6. Ven is initiated in cycle 4 and increased in standard fashion to 400 mg and continues with umbralisib once-daily through cycle 12. The primary endpoint for Phase 2 was complete remission (CR) rate by iwCLL criteria. Undetectable MRD ( Results: 40 pts have been treated to date. Baseline demographics were as follows: male/female (26/14), median age 65 yrs (range 43-83), median # prior therapies 2 (range 1-5). 20 pts (50%) had prior ibrutinib of which 11 (55%) were BTK refractory with BTK resistance mutations found in 8 cases. High-risk genetic features included unmutated IGHV genes (n=20), del17p (n=8), del11q (n=11), TP53 mut (n=4), NOTCH1 mut (n=5) and SF3B1 mut (n=2). Baseline (screening) TLS risk amongst efficacy evaluable pts (n=34) was high (H), medium (M) and low (L) risk in 5, 19 and 10 pts respectively. For all pts treated to date, the most common AEs were (all causality and all grade; >25% of pts) infusion related reactions [IRR] (63%), anemia (55%), thrombocytopenia (53%), neutropenia (53%), leukopenia (50%), creatinine increase, (50%), fatigue (45%), diarrhea (43%), nausea (38%), AST increase (30%). The only grade 3/4 AEs occurring in ≥ 5% of pts were neutropenia (23%) leukopenia (13%) and IRR (8%). Grade ≥ 3 PI3Kδ-associated toxicities of interest occurred in 2 pts (1 G3 colitis, and 1 G3 diarrhea). No TLS events were observed during Ven administration. Discontinuations of any study drug due to AE occurred in 3 pts, of which 1 pt discontinued all 3 agents (G3 diarrhea). Of 34 pts who completed 3 cycles of U2 debulking, TLS risk was substantially reduced: of 5 H-risk pts only 1 remained H-risk; of 19 M-risk pts, only 4 remained M-risk with the remainder at L-risk (79% reduction in H- and M-risk TLS). Among evaluable pts, the overall response rate was 76% (26/34) after cycle 3 (U2 debulking only), 100% (26/26) after cycle 7 and 100% (19/19) after cycle 12. Among the 19 pts who finished 12 cycles of therapy, 8 (42%) achieved CR by iwCLL criteria. Undetectable MRD ( Conclusion: U2-Ven is safe and highly effective in patients with relapsed/refractory CLL. Results suggest that this chemotherapy-free regimen can provide undetectable MRD after only 12 cycles of treatment, representing an effective 12-month treatment option for this population. These data have given rise to the multicenter ULTRA-V study, which is studying the U2-Ven triplet in patients with treatment naïve and relapsed/refractory CLL. Figure Disclosures Barr: Seattle Genetics: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; TG therapeutics: Consultancy, Research Funding; Verastem: Consultancy; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Morphosys: Consultancy; AstraZeneca: Consultancy, Research Funding; Gilead: Consultancy. Ma:Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kite: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; Bioverativ: Consultancy, Honoraria; BeiGene: Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding; TG Therapeutics: Research Funding; Juno: Research Funding; Novartis: Research Funding. Zent:TG Therapeutics, Inc: Research Funding; Acerta / Astra Zeneca: Research Funding; Mentrik Biotech: Research Funding. Liesveld:Abbvie: Honoraria; Onconova: Other: data safety monitoring board. Sportelli:TG Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Miskin:TG Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Weiss:TG Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Friedberg:Acerta Pharma - A member of the AstraZeneca Group, Bayer HealthCare Pharmaceuticals.: Other; Roche: Other: Travel expenses; Seattle Genetics: Research Funding; Astellas: Consultancy; Bayer: Consultancy; Kite Pharmaceuticals: Research Funding; Portola Pharmaceuticals: Consultancy. Hill:Pharmacyclics: Consultancy, Honoraria, Research Funding; Beigene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; AstraZenica: Consultancy, Honoraria, Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria; Genentech: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding.

Introduction: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein that is physiologically expressed during embryogenesis, largely disappears by birth, but can be reexpressed pathologically in transformed tissues of many hematological and solid cancers. VLS-101 is an antibody-drug conjugate (ADC) comprising a rapidly internalizing, humanized monoclonal antibody (UC-961) that recognizes extracellular ROR1, a cleavable linker, and the anti-microtubule cytotoxin, monomethyl auristatin E (MMAE). Methods: This first-in-human, Phase 1 study evaluated the safety, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and efficacy of VLS-101 in patients unselected for tumor ROR1 expression who had previously treated chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), or Richter transformation lymphoma (RTL). VLS-101 was infused over 30 min every 3 wk until cancer progression or intolerable toxicity. After accrual of 1 patient at the first dose level, cohorts were enrolled by 3+3 dose escalation with additional patients accrued and intrapatient dose escalation permitted to refine estimates of maximum tolerated dose and recommended dosing regimen (RDR). Results: 32 patients were enrolled, including 19 males and 13 females with median (range) ages of 70 (54-84) ys; ECOG performance status (n) of 0 (18), 1 (10), or 2 (4); and tumor types (n) of MCL (15), CLL (7), DLBCL (5), FL (3), MZL (1), and RTL (1). Patients had received a median (range) of 4 (1-24) prior systemic therapies including hematopoietic stem cell transplantation (5) and/or chimeric antigen receptor (CAR)-T or -natural killer (NK) cells (6). Among patients with MCL, 15/15 (100%) had received a Bruton tyrosine kinase inhibitor (BTKi), 13/15 (87%) discontinued the BTKi due to progressive disease, and 2/15 (13%) discontinued for atrial fibrillation after 15.6 or 68.5 months of BTKi therapy. Patients (n) by VLS-101 starting dose were 0.5 (1), 1.0 (3), 1.5 (3), 2.25 (11), and 2.5 (14) mg/kg. With intrapatient dose escalation, many patients (n) received a maximum of 2.25 mg/kg (12) or 2.5 mg/kg (17) during VLS-101 therapy (range: 1 to 13 cycles). Cycle 1 DLTs (n/N) by mg/kg dose level were 0.5 (0/1), 1.0 (0/3), 1.5 (0/3), 2.25 (1/11 [9%] Gr 4 neutropenia), and 2.5 (2/14 [14%]; one Gr 4 neutropenia; one Gr 3 diarrhea of uncertain cause). Gr 4 neutropenia occurred in 9/32 (28%) patients; 1/32 (3%) had neutropenic fever. Granulocyte colony-stimulating factor successfully ameliorated neutropenia. Baseline Gr 1 neuropathy was present in 10/32 (31%) patients. On-study reversible Gr 3 neuropathy occurred in 3/32 (9%) patients; no Gr 4 neuropathy occurred. Except for Gr ≤2 alopecia in 3/32 (9%) patients, other adverse events were not obviously drug-related. Considering all 175 infusions administered, drug-related infusion reactions, vomiting, tumor lysis syndrome, rash, hepatic or renal abnormalities, or QT prolongation were not observed. PK showed changes in ADC and MMAE exposures proportional with VLS-101 dose and a mean ADC half-life of ~2.5 d. PD indicated exposure-dependent ROR1 occupancy on circulating CLL cells. No neutralizing anti-drug antibodies were detected. Objective tumor responses were not seen in patients with other tumor types but were observed in 7/15 (47%) of patients with MCL (4 partial; 3 complete) and in 4/5 (80%) of patients with DLBCL (2 partial; 2 complete). From start of therapy, 6/7 patients with responding MCL have responses ongoing at 35, 38, 45, 47, 50, and 58 wk and 2/4 patients with responding DLBCL have responses ongoing at 23 and 47 wk of follow-up. Conclusions: In heavily pretreated patients, VLS-101 infusions were well tolerated and demonstrated a predictable safety profile consistent with an MMAE-containing ADC. Tumor selectivity was confirmed, with no evidence of ROR1-mediated toxicities or non-MMAE toxicities that would suggest normal tissue binding. Considering all data, the VLS-101 RDR was 2.5 mg/kg every 3 wk. Efficacy results provide clinical proof of concept for targeting ROR1 with VLS-101 and demonstrate durable objective responses in patients with advanced MCL or DLBCL, including those with prior BTKi or cellular therapies. Phase 1-2 studies of VLS-101 monotherapy and combination therapy in patients with hematological cancers and solid tumors are planned. Figure Disclosures Wang: Nobel Insights: Consultancy; Lu Daopei Medical Group: Honoraria; Oncternal: Consultancy, Research Funding; MoreHealth: Consultancy; Juno: Consultancy, Research Funding; Loxo Oncology: Consultancy, Research Funding; Acerta Pharma: Research Funding; InnoCare: Consultancy; OncLive: Honoraria; Guidepoint Global: Consultancy; VelosBio: Research Funding; Pulse Biosciences: Consultancy; Kite Pharma: Consultancy, Other: Travel, accommodation, expenses, Research Funding; Beijing Medical Award Foundation: Honoraria; Pharmacyclics: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; OMI: Honoraria, Other: Travel, accommodation, expenses; Celgene: Consultancy, Other: Travel, accommodation, expenses, Research Funding; BioInvent: Research Funding; Molecular Templates: Research Funding; Verastem: Research Funding; Dava Oncology: Honoraria; AstraZeneca: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Targeted Oncology: Honoraria. Barrientos:Gilead: Consultancy; Genentech: Consultancy; Bayer: Consultancy; Oncternal Therapeutics: Research Funding; Sandoz: Consultancy; Janssen: Honoraria; AstraZeneca: Consultancy. Furman:Verastem: Consultancy; Incyte: Consultancy; Janssen: Consultancy, Speakers Bureau; Loxo Oncology: Consultancy; Oncotarget: Consultancy; Pharmacyclics: Consultancy; Sunesis: Consultancy; TG Therapeutics: Consultancy, Research Funding; Acerta: Consultancy; Abbvie: Consultancy; AstraZeneca: Consultancy, Research Funding; Beigene: Consultancy; Genentech: Consultancy. Mei:Sanofi: Consultancy; Morphosys: Membership on an entity's Board of Directors or advisory committees. Barr:AstraZeneca: Consultancy, Research Funding; Verastem: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Merck: Consultancy; Morphosys: Consultancy; Gilead: Consultancy; Seattle Genetics: Consultancy; TG therapeutics: Consultancy, Research Funding; Celgene: Consultancy; Janssen: Consultancy; Genentech: Consultancy. Choi:Genentech: Consultancy; Pharmacyclics/Abbvie: Research Funding. de Vos:Bayer: Consultancy; Verastem: Consultancy. Patel:Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy; Kite: Consultancy; Janssen: Consultancy, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Adaptive Biotechnologies: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau. Rule:Janssen: Consultancy; Kite: Consultancy; Pharmacyclics: Consultancy. Flanders:VelosBio: Current Employment, Current equity holder in private company. Jessen:VelosBio: Current Employment, Current equity holder in private company; eFFECTOR: Current equity holder in private company. Riebling:VelosBio: Current Employment, Current equity holder in private company. Graham:Ce3: Current Employment. King:Ce3: Current Employment; VelosBio: Consultancy; AI Therapeutics: Consultancy. Schmidt:VelosBio: Current Employment, Current equity holder in private company; Gilead Sciences: Current equity holder in publicly-traded company. Lannutti:VelosBio: Current Employment, Current equity holder in private company; Gilead Sciences: Current equity holder in publicly-traded company. Johnson:Zentalis: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Current equity holder in publicly-traded company; Neoleukin: Current equity holder in publicly-traded company; Oncternal: Divested equity in a private or publicly-traded company in the past 24 months; Appelis: Divested equity in a private or publicly-traded company in the past 24 months; Acerta: Patents & Royalties; VelosBio: Current Employment, Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Miller:Cleveland BioLabs: Consultancy, Current equity holder in publicly-traded company; Gilead Sciences: Current equity holder in publicly-traded company; Cancer Genetics: Current equity holder in publicly-traded company; Incuron: Consultancy; Zentalis: Consultancy, Current equity holder in publicly-traded company; AbbVie: Current equity holder in publicly-traded company; EpiThany: Current equity holder in private company; AstraZeneca: Current equity holder in publicly-traded company; VelosBio: Consultancy, Current Employment, Current equity holder in private company; AI Therapeutics: Consultancy, Current equity holder in private company; Catalys Pacific: Consultancy. Spurgeon:Cardinal Health: Honoraria; VelosBio: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Pharmacyclics: Consultancy; Bristol-Myers Squibb: Research Funding; Genentech: Research Funding; Gilead: Research Funding; Acerta: Research Funding; AstraZeneca: Research Funding; Genmab: Research Funding; Beigene: Research Funding; Verastem: Research Funding.

B-cell receptor kinase inhibitor (KI) therapy represents a paradigm shift in chronic lymphocytic leukemia (CLL) management, but data on practice patterns after KI discontinuation and optimal sequencing are limited. We conducted a multicenter, retrospective, comprehensive analysis on 178 patients with CLL (ibrutinib = 143; idelalisib = 35) who discontinued KI therapy. We examined responses, toxicity, post-KI therapies, and overall survival (OS). Patients had a median of 3 prior therapies (range 0-11); del17p (34%), p53 mutation (27%), del11q (33%), and complex karyotype (29%). Overall response rate (ORR) to first KI was 62% (complete response 14%). The most common reasons for KI discontinuation were toxicity (51%), CLL progression (29%), and Richter transformation (RT) (8%). Median progression-free survival (PFS) and OS from KI initiation were 10.5 and 29 months, respectively. Notably, initial KI choice did not impact PFS or OS; however, RT portended significantly inferior OS (P = .0007). One hundred fourteen patients received subsequent salvage therapy following KI discontinuation with an ORR to subsequent KI at 50% and a median PFS of 11.9 months. Median PFS in KI-intolerant patients treated with an alternate KI was not reached vs 7 months for patients with CLL progression. In summary, these data demonstrate that toxicity was the most common reason for KI discontinuation, that patients who discontinue KI due to toxicity can respond to an alternate KI, and that these responses may be durable. This trial was registered at www.clinicaltrials.gov as #NCT02717611 and #NCT02742090.

To the editor: Follicular lymphoma (FL) is the most common type of indolent non-Hodgkin lymphoma (NHL), accounting for ∼22% of all patients with NHL.[1][1] Several studies identified a high-risk population of patients, comprising ∼20% of all patients with NHL, who had FL that progressed within

Background Combinations of different targeted therapies, including Bruton tyrosine kinase (BTK) inhibitors and anti-CD20 monoclonal antibodies (mAbs) could improve treatment for CLL. Unexpectedly, the combination of ibrutinib (IBR) with rituximab did not show additional clinical benefit. However, IBR inhibits many off-target molecules that may limit therapeutic mAb clinical effectiveness and a more selective BTK inhibitor, such as acalabrutinib (ACALA), could be more effective in combination with mAb therapy. Initial data from the ELEVATE TN trial support this possibility. IBR off-target effects on antibody-dependent cellular phagocytosis (ADCP), the major mechanism of therapeutic mAb activity could explain this difference. Additionally, IBR induces a higher and longer duration increase in circulating lymphocytes than ACALA. IBR off-target effects on efferocytosis, another phagocytic process involved in apoptotic cell removal, might explain this difference. Methods Using state-of-the-art direct kinetic measurements of phagocytosis by time-lapse video, (Chu et al. J Cell Sci 2020;133:jcs237883) we investigated the effects of IBR and ACALA on phagocytosis (ADCP or efferocytosis) by human monocyte-derived macrophages (hMDM) in vitro. Live cell time-lapse video of 10 μg/ml rituximab (Genentech) mediated ADCP of CLL cells by CellTracker Deep Red (CTDR, Thermofisher) labeled hMDM (20:1 CLL:hMDM cell ratio) either untreated or treated with IBR or ACALA (3-fold serial dilutions from 100 to 0.41 μM) was imaged in a stage-top environmental chamber (37°C and 5% CO2) mounted onto a Nikon Ti-Eclipse inverted microscope with an ELWD 20x/0.45NA S Plan Fluor Ph1 objective and an Andor Zyla 5.5 sCMOS camera. Images were captured sequentially every 4 min over 2.8 h. For each experiment (n = 18), duplicate or triplicate wells for each drug concentration were imaged. For efferocytosis, live cell time-lapse video imaging of phagocytosis of pHrodo iFL Red STP ester (pHrodo Red, Thermo Fisher Scientific) labeled apoptotic CLL cells by CTDR-labeled hMDM (20:1 CLL:hMDM cell ratio) either untreated or treated with IBR or ACALA (2-fold serial dilutions from 10 to 1.25 μM) was collected every 4 min over 2.8 h. For each experiment (n = 7), duplicate or triplicate wells for each drug concentration was imaged and analyzed. Finally, for efferocytosis, the intensity of pHrodo Red dye, a pH-sensitive dye that increases in intensity with acidic pH, as found in the endolysosomes, was measured in the pHrodo Red color channel and analyzed. Results IBR significantly inhibited ADCP at all measured drug concentrations (0.41 μM, p < 0.05; 1.2 μM, p < 0.01; 3.7 - 100 μM, p < 0.001). The mean peak free drug concentration (Cmax) achieved clinically by standard doses for IBR is ~0.5 μM. ACALA only significantly inhibited ADCP at the highest concentration (100 μM, p < 0.001). The Cmax achieved clinically by standard doses for ACALA is ~1.2 μM. ACALA did not inhibit efferocytosis or subsequent transition to endolysosomal compartment at all tested concentrations (p > 0.05). IBR did not inhibit efferocytosis (p > 0.05) and only inhibited transition to endolysosomal compartment at highest concentration tested (10 μM, p < 0.01) Conclusion Our study shows that BTK inhibition does not block ADCP and a more selective BTK inhibitor may prove effective in combination with therapeutic anti-CD20 mAbs. IBR off-target inhibition specifically blocks ADCP and not efferocytosis. Thus, IBR off-target inhibition of ADCP should be via proximal signaling by antibody Fc receptors and not subsequent downstream phagocytic mechanisms in common with efferocytosis. These results also imply the lack of BTK and IBR off-target molecules involvement in efferocytosis. Finally, the increased lymphocytosis seen with IBR compared to ACALA treatment in CLL cannot be explained by IBR off-target effects on efferocytosis. These findings provide a critical understanding of macrophage phagocytosis reduction by BTK inhibitor selectivity that will have important consequences for the development of combination targeted therapies with mAbs. Disclosures Chu: Acerta Pharma/AstraZeneca: Research Funding; Pfizer: Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months; TG Therapeutics: Research Funding. Izumi:AstraZeneca: Current equity holder in publicly-traded company; Acerta Pharma: Current equity holder in private company, Ended employment in the past 24 months, Patents & Royalties: Acalabrutinib patents (no royalties). Munugalavadla:Gilead Sciences: Current equity holder in publicly-traded company; AstraZeneca: Current equity holder in publicly-traded company; Acerta Pharma: Current Employment. Barr:Gilead: Consultancy; Morphosys: Consultancy; TG therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; Celgene: Consultancy; AstraZeneca: Consultancy, Research Funding; Janssen: Consultancy; Merck: Consultancy; Genentech: Consultancy; Abbvie/Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy. VanDerMeid:Acerta Pharma / AstraZeneca: Research Funding. Elliott:Acerta Pharma / AstraZeneca: Research Funding. Zent:Mentrik Biotech: Research Funding; TG Therapeutics, Inc: Research Funding; Acerta / Astra Zeneca: Research Funding.

Follicular lymphoma (FL) is the most frequently occurring indolent non-Hodgkin lymphoma, with generally favorable outcomes but a variable clinical course. Recent studies have elucidated the consistent and reproducible frequency of early disease progression in FL, occurring in ∼20% of patients. Relapse of FL within 24 months of chemoimmunotherapy (POD24) is now established as a robust marker of poor survival, leading to increased risk of death. Currently, there is no established method of identifying patients at risk for early disease progression at the time of their FL diagnosis. However, numerous studies worldwide are investigating clinical, pathologic, and radiographic biomarkers to help predict POD24, thereby improving subsequent outcomes and adapting therapy based on individual risk. There is also a paucity of standardized treatments for patients with POD24, but investigations are ongoing testing novel targeted therapies and autologous stem cell transplantation strategies. This review provides an overview of early-relapsing FL and our approach to patient management based on recent available data.

Because both phosphatidylinositol 3-kinase δ (PI3Kδ) and Janus kinase (JAK)-signal transducer and activator of transcription pathways contribute to tumor cell proliferation and survival in B-cell malignancies, their simultaneous inhibition may provide synergistic treatment efficacy. This phase 1 dose-escalation/expansion study assessed the safety, efficacy, pharmacokinetics, and pharmacodynamics of INCB040093, a selective PI3Kδ inhibitor, as monotherapy or combined with itacitinib (formerly INCB039110), a selective JAK1 inhibitor, in adult patients with relapsed or refractory (R/R) B-cell lymphomas. Final results are reported. Overall, 114 patients were treated (monotherapy, n = 49; combination therapy, n = 72 [7 patients crossed over from monotherapy to combination]). INCB040093 100 mg twice daily (monotherapy) and INCB040093 100 mg twice daily + itacitinib 300 mg once daily (combination) were the recommended phase 2 doses. One dose-limiting toxicity (gastrointestinal bleed secondary to gastric diffuse large B-cell lymphoma [DLBCL] regression) occurred with monotherapy. The most common serious adverse events with monotherapy were pneumonia (n = 5) and pyrexia (n = 4), and with combination Pneumocystis jiroveci pneumonia (n = 5), pneumonia (unrelated to P jiroveci; n = 5), and pyrexia (n = 4). Grade 3 or higher transaminase elevations were less common with combination. INCB040093 was active across the B-cell lymphomas; 63% of patients (5/8) with follicular lymphoma responded to monotherapy. Adding itacitinib provided promising activity in select subtypes, with responses of 67% (14/21) in classic Hodgkin lymphoma (vs 29% [5/17] with monotherapy) and 31% (4/13) in nongerminal center B-cell-like DLBCL. INCB040093 with/without itacitinib was tolerated and active in this study, and is a promising treatment strategy for patients with select R/R B-cell lymphomas. This trial was registered at www.clinicaltrials.gov as #NCT01905813.

BACKGROUND: Chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab (FCR) has been the standard therapy for younger patients with CLL. FCR therapy is particularly effective in patients with immunoglobulin heavy chain variable region (IGHV) mutated CLL. Approximately half of IGHV mutated patients are progression free 8 years after FCR therapy. At the ASH 2018 meeting, we reported the initial results of the ECOG 1912 (E1912) trial, a phase 3 trial comparing the FCR regimen to the combination of ibrutinib and rituximab (IR) for previously untreated CLL patients age 70 or younger who required therapy. With median follow-up of approximately 34 months, the trial demonstrated both a progression-free survival (PFS) and an overall survival (OS) benefit relative to FCR. On sub-set analysis by IGHV mutation status, the difference in PFS was statistically significant for IGHV unmutated patients but, with current follow-up, not IGHV mutated patients. Here, we present updated results for PFS in the E1912 trial. METHODS: As previously reported, eligible patients were treatment-naive individuals with CLL age 70 or younger. Patients with deletion 17p- were excluded from participating in the E1912 trial given their known poor response to FCR therapy. Patients were randomly assigned in a two-to-one ratio to receive ibrutinib (420 mg/day until disease progression or unacceptable toxicity) and rituximab (50 mg/m2 on day 1 of cycle 2, 325 mg/m2 on day 2 of cycle 2, and then 500 mg/m2 on day 1 of cycles 3-7) or six courses of intravenous fludarabine (25 mg/m2 days 1-3), cyclophosphamide (250 mg/m2 days 1-3) and rituximab (50 mg/m2 on day 1 of cycle 1, 325 mg/m2 on day 2 of cycle 1, and then 500 mg/m2 on day 1 of cycles 2-6) every 28-days. Adverse events (AEs) were graded according to the NCI Common Toxicity Criteria (version 4). Dose adjustments for cytopenias were based on the IWCLL CLL Working Group grading scale. The primary endpoint of the trial was PFS with OS a secondary endpoint. Analysis was by intention to treat. RESULTS: With median follow-up of 45 months, 257 (73%) of 354 patients randomized to IR remain on ibrutinib. With extended follow-up, grade 3 and above treatment-related AEs were observed in 70% of IR and 80% of FCR treated patients (OR=0.56; 95% CI 0.34 - 0.90; p=0.013). Among IR-treated patients, the median time on treatment is currently 43 months (range=0.2-61). Among the 95 patients who have discontinued ibrutinib, the reason for discontinuation was progression or death in 23 (7% of patients who started IR; 24% of those who discontinued treatment), AE or complication in 48 (14% of patients who started IR; 51% of those who discontinued treatment), and withdrawal of consent or other reasons in 24 (7% of patients who started IR; 25% of those who discontinued treatment). On multivariable Cox regression adjusting for Timed Up and Go test score, Cumulative Illness Rating Scale (CIRS) score, age, gender, ECOG performance status, creatinine clearance, and baseline anemia/thrombocytopenia, only CIRS score (range 0 - 14) predicted discontinuation of ibrutinib for a reason other than progression or death (HR=1.13 per unit increase; 95% CI 1.03 - 1.23; p=0.009). Among the 72 patients who discontinued ibrutinib for a reason other than progression or death, the median time on ibrutinib was 15.1 months (range 0.2-58.2 months). The median time from ibrutinib discontinuation to disease progression or death was 23 months. With current follow-up, we observed 110 PFS events. The hazard ratio (HR) for PFS favored IR over FCR (HR=0.39; 95% CI 0.26-0.57; p CONCLUSIONS: Although less than 7% of ibrutinib treated patients progressed while on therapy, roughly 1 in 5 patients have discontinued ibrutinib for a reason other than progression or death. The only parameter significantly associated with discontinuation for a reason other than progression was increased baseline CIRS score. With extended follow-up, the combination of ibrutinib and rituximab continues to provide superior PFS compared to FCR for younger patients with previously untreated CLL. Disclosures Shanafelt: Pharmacyclics: Research Funding; Patent: Patents & Royalties: US14/292,075 on green tea extract epigallocatechin gallate in combination with chemotherapy for chronic lymphocytic leukemia; Polyphenon E International: Research Funding; Merck: Research Funding; Abbvie: Research Funding; Genentech: Research Funding; Celgene: Research Funding; Glaxo-SmithKline: Research Funding; Hospira: Research Funding; Cephalon: Research Funding. Kay:MorphoSys: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Agios: Other: DSMB. O'Brien:Janssen: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Astellas: Consultancy; Aptose Biosciences, Inc: Consultancy; Amgen: Consultancy; Alexion: Consultancy; Acerta: Research Funding; Eisai: Consultancy; Gilead: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Verastem: Consultancy; Celgene: Consultancy; Sunesis: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Vaniam Group LLC: Consultancy; Regeneron: Research Funding; Kite: Research Funding. Barrientos:AbbVie: Consultancy, Research Funding; AstraZeneca: Consultancy; Genentech: Consultancy; Bayer: Consultancy; Gilead: Consultancy; Janssen: Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Sandoz: Consultancy; Oncternal Therapeutics: Research Funding. Coutre:Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Astra Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta: Research Funding; Gilead: Research Funding; BeiGene: Other: Travel, Accommodations, Expenses & Data Safety Monitoring Committee; Genentech: Consultancy. Barr:Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; Gilead: Consultancy; Verastem: Consultancy; Genentech: Consultancy; Seattle Genetics: Consultancy; Merck: Consultancy; Celgene: Consultancy; Janssen: Consultancy; AbbVie: Consultancy; Astra Zeneca: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding. Cashen:Celgene: Other: Speaker's Bureau; Seattle Genetics: Other: Speaker's Bureau; Novartis: Other: Speaker's Bureau. Mato:AstraZeneca: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Celgene: Consultancy; Johnson & Johnson: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member , Research Funding; LOXO: Consultancy, Research Funding; DTRM Biopharma: Research Funding; Genentech: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Gilead: Research Funding; Acerta: Consultancy; Janssen: Consultancy. Erba:Amgen: Consultancy; MacroGenics: Consultancy, Other: Lecture fees, Research Funding; MacroGenics: Consultancy, Other: Lecture fees, Research Funding; Novartis: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Agios: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; ImmunoGen: Consultancy, Research Funding; Astellas Pharma: Consultancy; Astellas Pharma: Consultancy; Amgen: Consultancy; GlycoMimetics: Consultancy, Other: Chair, data and safety monitoring board, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Celgene: Consultancy, Other: chair, AML Registry Scientific Steering Committee, Speakers Bureau; ImmunoGen: Consultancy, Research Funding; AbbVie: Consultancy, Other: Chair, IRC for phase III studies, Research Funding; GlycoMimetics: Consultancy, Other: Chair, data and safety monitoring board, Research Funding; Covance: Other: Fees for serving as chair on an independent review board for AbbVie Phase III studies; Covance: Other: Fees for serving as chair on an independent review board for AbbVie Phase III studies; AbbVie: Consultancy, Other: Chair, IRC for phase III studies, Research Funding; Celgene: Consultancy, Other: chair, AML Registry Scientific Steering Committee, Speakers Bureau; Pfizer: Consultancy; Pfizer: Consultancy; Seattle Genetics: Consultancy; Seattle Genetics: Consultancy; Daiichi Sankyo: Consultancy, Research Funding. Stone:Arog Pharmaceuticals: Consultancy, Honoraria, Research Funding; Otsuka-Astex Pharmaceuticals: Consultancy; Fujifilm: Consultancy; AstraZeneca: Consultancy; Celator Pharmaceuticals: Consultancy; Abbvie: Consultancy, Research Funding; Ono Pharmaceutical-Theradex Oncology: Consultancy; Cornerstone Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Takeda: Other: Fees for serving on a data and safety monitoring board ; Orsenix: Consultancy; MacroGenics: Consultancy; Jazz Pharmaceuticals: Consultancy; Agios: Consultancy, Research Funding; Stemline Therapeutics: Consultancy; Pfizer: Consultancy; Celgene: Consultancy, Other: Fees for serving on a steering committee, and fees for serving on a data and safety monitoring board; Novartis: Consultancy, Research Funding; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Astellas Pharma: Membership on an entity's Board of Directors or advisory committees; Argenx: Other: Fees for serving on a data and safety monitoring board ; Roche: Consultancy. Tallman:Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Oncolyze: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Introduction: Ibrutinib, an orally and continuously administered Bruton tyrosine kinase inhibitor, allows for targeted, non-chemotherapy based treatment for chronic lymphocytic leukemia (CLL). While the initial US marketing approval for ibrutinib in CLL was for relapsed disease (February 2014), several trials have since shown favorable efficacy in the first-line setting. Ibrutinib was well tolerated in these pivotal studies, with discontinuation occurring in less than 9% at 12 months (O'Brien et al., Am J Hemato. 2019). Most early ibrutinib discontinuations in the first-line setting are due to adverse events (Tedeschi et al., EHA 2019), and optimal strategies to manage ibrutinib-related toxicities are not well defined. We hypothesized that ibrutinib is increasingly utilized for first-line treatment of CLL during routine management in the US, but that ibrutinib discontinuation rates for the real-world population are greater than those reported in clinical trials. Further, we expected to find greater odds of discontinuation in older adults and those with poor performance status, two groups underrepresented in clinical trials. Methods: We conducted a retrospective cohort study of CLL patients treated at community oncology practices using the nationwide Flatiron Health database. The Flatiron Health database is a longitudinal, demographically and geographically diverse database derived from de-identified electronic health record data from over 280 cancer clinics in the US. All patients initiated CLL therapy in the first-line setting between March 1, 2014 and February 28, 2019. We first assessed trends in the use of first-line ibrutinib (i.e., ibrutinib with/without an anti-CD20 antibody). We then focused on patients who received ibrutinib and had at least 180 days of available follow up or had died within this period. We used multivariable logistic regression to assess the association of patient characteristics with early discontinuation (defined as stopping within 180 days of initiation). Covariates included in our model were patient age, sex, race, insurance type, ECOG performance status, year of treatment, time from CLL diagnosis to ibrutinib initiation, chromosome 17p status, and geographical region. Results: We identified 5,634 individuals initiating first-line treatment for CLL, of whom 1,639 (29.1%) received an ibrutinib-based regimen. Use of ibrutinib in the first-line setting increased over time (Cochrane-Armitage test for trend, p Conclusion: While ibrutinib was increasingly utilized in the first-line setting for CLL within our large representative US community patient cohort, early discontinuation was more common than reported in pivotal trials. Given the complexity of the rapidly changing CLL treatment landscape, clinical decision support tools and other modern cancer care delivery approaches should be explored to improve administration of novel CLL therapies in the real-world setting. Disclosures Huntington: Genentech: Consultancy; Bayer: Consultancy, Honoraria; AbbVie: Consultancy; Celgene: Consultancy, Research Funding; DTRM Biopharm: Research Funding; Pharmacyclics: Honoraria. Barr:Merck: Consultancy; Janssen: Consultancy; AbbVie: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; Celgene: Consultancy; Genentech: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Astra Zeneca: Consultancy, Research Funding. Jacobs:Genentech: Speakers Bureau; AstraZeneca: Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Research Funding, Speakers Bureau; TG Therapeutics: Honoraria, Research Funding; AbbVie: Consultancy, Speakers Bureau; JUNO: Consultancy; Gilead: Consultancy. Davidoff:PhRMA: Research Funding; Celgene: Research Funding. Gross:Johnson and Johnson: Research Funding; 21st Century Cancer: Research Funding; Pfizer: Research Funding.

Introduction: Venetoclax (VEN) based therapy has become a standard of care in front line and relapsed-refractory (R/R) CLL based on favorable efficacy and toxicity. Whereas prospective data regarding activity of therapies following ibrutinib (IBR) or idelalisib (IDE) are available in the settings of progression (VEN, non-covalent BTKi) and intolerance (acalabrutinib), how best to manage patients (pts) who discontinue (dc) VEN remains a key unanswered question. With the increased use of VEN in early lines of therapy (LOT; CLL 14, MURANO), the activity of BTK inhibitors (BTKi) and cellular therapies following VEN becomes a critical issue. No prospective study has addressed this question, and currently reported VEN clinical trials have limited information about subsequent treatments. While recent data describe VEN resistance mechanisms (Guieze 2018, Blombery 2019), the impact of VEN resistance on efficacy of post VEN therapies is unknown. To address this gap, we conducted an international study to identify a large cohort of pts who dc VEN and have been subsequently treated. Methods: We conducted an IRB approved multicenter (31 US, EU, South American sites, in partnership with UK CLL Forum and CORE registry), retrospective cohort study of CLL pts who dc VEN for any reason. We examined demographics, dc reasons, responses, survival, adverse events (AEs) and activity of post VEN therapies. Primary endpoints were overall response rate (ORR) and progression free survival (PFS) for the post VEN treatments stratified by treatment type (BTKi, PI3Ki and cellular therapy: CAR-T or alloHSCT). ORR was defined by iwCLL criteria and PFS was defined from VEN dc to disease progression (PD), death, or last follow up for next treatment. Pts were further stratified by BTKi (resistant / intolerant) and PI3Ki exposure prior to VEN. PFS-2 was defined as time from VEN start to tumor progression on IBR or death from any cause. Results: 326 CLL pts who dc VEN in the front line (4%) and R/R settings (96%) were identified. The cohort was 69% male, 87% white, median (med) age 66 (38-91) at VEN start, 27% treated with VEN based combinations (n=88, med 6 cycles anti-CD20 abs). Pre VEN prognostic features: 82% IGHV unmutated (n tested=166), 47% del17p (n=306), 45% TP53 mut (n=217), 39% complex karyotype (n=273), 23% BTK mut (n=79), 18% NOTCH1 mut (n=103), 10% PLCγ2 mut (n=74). Pts received med 3 therapies (0-11) prior to VEN; 40% were BTKi naïve (n=130), 60% were BTKi exposed (196) and 81% were IDE naïve (n=263). Most common reasons for VEN dc were PD (38%), AE (20%), Richter's transformation (RT, 14%), 8% pt preference, and HSCT 5%. Of 326 pts who dc VEN, 188 (58%) were treated with a subsequent LOT, 61 are alive and untreated and 77 died prior to a subsequent LOT. Post VEN sequencing analyses focused on BTKi, PI3Ki and cellular therapy (CAR-T or alloHSCT) activities following VEN dc (Table1). ORR to BTKi was 84% (n=44) vs. 54% (n=30, p Conclusions: In the largest experience of therapies following VEN dc in CLL, we demonstrated that therapy selection following VEN requires consideration of prior novel agent exposure and reasons for discontinuation. For BTKi naïve pts, selection of a covalently binding BTKi results in high ORR and durable remissions. PFS-2 data provide reassurance for using VEN prior to IBR. For BTKi exposed pts, BTK inhibition is not effective in the setting of BTKi resistance but should be considered if prior BTKi intolerance. PI3K inhibition following VEN does not appear to result in durable remissions even in PI3Ki naïve pts, suggesting possible overlap in resistance mechanisms (BTK or VEN with PI3K). We conclude that BTKi in naïve or previously responsive pts and alloHSCT following VEN appear to be the most effective strategies with durable responses. These data suggest that a number of effective regimens exist for post VEN pts, providing support for VEN use earlier in the course of CLL. Disclosures Mato: Acerta: Consultancy; LOXO: Consultancy, Research Funding; DTRM Biopharma: Research Funding; Janssen: Consultancy; Gilead: Research Funding; Pharmacyclics: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Johnson & Johnson: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member , Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Celgene: Consultancy. Roeker:AbbVie: Equity Ownership; Abbott Laboratories: Equity Ownership. Eyre:Gilead: Consultancy, Other: Research support, Speakers Bureau; Roche: Honoraria; Abbvie: Honoraria, Other: Travel to Conferences; Janssen: Honoraria, Other: Travel to Conferences ; Takeda: Other: Travel to Conferences . Jacobs:Pharmacyclics LLC, an AbbVie Company: Research Funding, Speakers Bureau; AstraZeneca: Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Genentech: Speakers Bureau; JUNO: Consultancy; Gilead: Consultancy; TG Therapeutics: Honoraria, Research Funding. Hill:TG therapeutics: Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Research Funding; Kite: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Honoraria; Celegene: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Takeda: Research Funding; Amgen: Research Funding. Lamanna:Celgene: Consultancy; Infinity/ Verastem: Research Funding; Ming: Research Funding; TG Therapeutics: Research Funding; Oncternal: Research Funding. Brander:Tolero: Research Funding; MEI: Research Funding; BeiGene: Research Funding; DTRM Biopharma: Research Funding; Genentech: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria; TG Therapeutics: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Research Funding; Novartis: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy; AbbVie: Consultancy, Honoraria, Research Funding; Acerta: Research Funding. Shadman:AbbVie: Consultancy, Research Funding; Astra Zeneca: Consultancy; BeiGene: Research Funding; TG Therapeutic: Research Funding; ADC Therapeutics: Consultancy; Atara Biotherapeutics: Consultancy; Verastem: Consultancy; Acerta Pharma: Research Funding; Sunesis: Research Funding; Mustang Bio: Research Funding; Celgene: Research Funding; Pharmacyclics: Consultancy, Research Funding; Sound Biologics: Consultancy; Genentech: Consultancy, Research Funding; Gilead: Consultancy, Research Funding. Ujjani:AstraZeneca: Consultancy; Genentech: Consultancy; Rigel: Consultancy; Gilead: Consultancy; Abbvie: Research Funding; Pharmacyclics: Research Funding. Perini:Janssen: Other: Advisory Board; Abbvie: Other: Advisory Board; AstraZeneca: Other: Advisory Board. Pinilla Ibarz:Sanofi: Speakers Bureau; Bayer: Speakers Bureau; Novartis: Consultancy; Bristol-Myers Squibb: Consultancy; Takeda: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; Teva: Consultancy; TG Therapeutics: Consultancy. Barrientos:Pharmacyclics: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Janssen: Consultancy; Gilead: Consultancy; Genentech: Consultancy. Skarbnik:Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Honoraria, Speakers Bureau; CLL Society: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Speakers Bureau; Novartis: Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Verastem Oncology: Honoraria, Research Funding, Speakers Bureau; Kite Pharma: Honoraria, Speakers Bureau; Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Acerta: Research Funding. Pagel:AstraZeneca: Consultancy; Gilead Sciences: Consultancy; Pharmacyclics: Consultancy. Choi:Abbvie: Consultancy, Research Funding, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy, Research Funding, Speakers Bureau; Rigel: Consultancy, Research Funding; Gilead: Consultancy, Speakers Bureau; Oncternal: Research Funding. Coombs:H3 Biomedicine: Research Funding. Barr:Janssen: Consultancy; Astra Zeneca: Consultancy, Research Funding; Merck: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Genentech: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; Celgene: Consultancy; TG Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; AbbVie: Consultancy. Portell:Xencor: Research Funding; Roche/Genentech: Research Funding; Infinity: Research Funding; TG Therapeutics: Research Funding; AbbVie: Research Funding; Pharmacyclics: Consultancy; Janssen: Consultancy; Genentech: Consultancy, Research Funding; Amgen: Consultancy; Bayer: Consultancy; BeiGene: Consultancy, Research Funding; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding. Schuster:AstraZeneca: Honoraria; AbbVie: Honoraria, Research Funding; Acerta: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Loxo Oncology: Honoraria; Pfizer: Honoraria; Nordic Nanovector: Honoraria; Pharmacyclics: Honoraria, Research Funding; Novartis: Honoraria, Patents & Royalties: Combination Therapies of CAR and PD-1 Inhibitors with royalties paid to Novartis, Research Funding; Merck: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Gilead: Honoraria, Research Funding. Martinez-Calle:ABBVIE: Other: Travel support. Munir:AbbVie: Honoraria; Alexion: Honoraria; Gilead: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Roche: Honoraria; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sunesis: Consultancy; Pharmacyclics: Other: TBC; Acerta: Membership on an entity's Board of Directors or advisory committees. Nabhan:Aptitude Health: Employment. King:Astrazeneca: Other: Advisory board; Genentech: Other: Advisory Board ; Incyte: Other: Advisory Board. Zelenetz:Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees. Cheson:Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Symbios: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trillium: Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Portola: Research Funding; Kite: Research Funding; Gilead: Research Funding; Epizyme: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy, Research Funding. Fox:Gilead: Consultancy; Janssen: Consultancy; Celgene: Consultancy; AbbVie: Consultancy; Sunesis: Consultancy; Takeda Pharmaceuticals: Consultancy; Atara Biotherapeutics: Consultancy; Adienne: Other: Travel Support. Allan:Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Janssen: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie company: Consultancy; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Consultancy.

The efficacy of many therapeutic unconjugated monoclonal antibodies (mAbs), including those targeting CD20 in CLL, requires immune cell-mediated cytotoxicity. mAbs have often been optimized for natural killer (NK) cell antibody-dependent cellular cytotoxicity (ADCC) activity. However, in vivo mouse studies have shown that antibody-dependent cellular phagocytosis (ADCP) by macrophages is the major mechanism of clearance of circulating B cells by anti-CD20 mAbs. To directly compare ADCC versus ADCP, we previously used a panel of anti-CD20 mAbs (rituximab, ofatumumab, obinutuzimab, ocaratuzumab) to test cytotoxicity of paired human NK cells and monocyte-derived macrophages (hMDM) against CLL cells in vitro. All mAbs demonstrated ADCP activity at least 10-fold greater than ADCC as measured by CLL cell depletion per effector cell. Moreover, ADCC and ADCP activity levels did not correlate, meaning that ADCC cannot be used as a surrogate measure of ADCP for these mAb. This could explain why mAb optimization for ADCC activity has often failed to translate into more efficacious treatment. Thus, ADCP may be an effective translational measurement of anti-CD20 mAb performance. Because of the clinical interest in combining anti-CD20 mAb with targeted small molecule inhibitors, we began studying the effects of the Bruton tyrosine kinase (BTK) inhibitors on anti-CD20 mAb-mediated ADCP. Our initial studies showed that ibrutinib (IBR), but not acalabrutinib (Acala), significantly decreased anti-CD20 ADCP as measured by a flow cytometry-based assay that measures single timepoint cell collections. These types of assays cannot easily determine the kinetics and individual effector cell activity of ADCP. Thus, to more fully study the BTK inhibitor effects on ADCP, we developed a live cell time-lapse imaging method for measuring ADCP, utilizing recent advances in microscopy, cellular dye labeling, digital imaging, imaging software and computing. Whole-cell labeling of macrophages enabled visualization of internalized CLL cells as regions of dye exclusion or "voids". Because of the vast number of images acquired during live cell time-lapse imaging, we utilized computer software-aided image recognition and enumeration to measure the number of macrophages and voids inside each macrophage. As a measure of phagocytic engulfment, we developed a void index, which provides a relative measure of phagocytic engulfment per macrophage. Measuring ADCP in this manner replicates clinical observation of mAb therapeutic activity. Clinically, intravenous anti-CD20 mAb therapy typically induces a rapid decrease in circulating CLL cells (within hours), followed by a long period (days) of stable to increased levels of circulating cells. Similarly, our live cell time-lapse video assay shows initial rapid ADCP over the first 2 hours followed by a prolonged period of "hypophagia" with little ADCP for the remainder of the assay (imaged every 2 minutes for 8 hours). This "hypophagia" phenomenon may explain the resistance to therapeutic mAb observed clinically. With these new tools for quantitation of ADCP, we compared the effects of serial dilutions of IBR or Acala on ADCP. Overall, as measured by Area Under the Curve (AUC) analysis, IBR decreased phagocytic capacity of anti-CD20 mediated CLL cell ADCP at concentrations of 0.41 μM and above. By contrast, Acala did not begin to decrease AUC measurements until 3.7 μM, and subsequent AUC values were higher in Acala versus IBR-treated ADCP assays up to the highest tested drug concentration (100 μM). Similarly, the initial ADCP kinetics (void index / min over the first hour) reflected a decrease with IBR treatment at 0.41 μM that continued until a nadir was reached at 33 μM. In contrast, Acala did not induce a decrease in this kinetic measurement until 3.7 μM and a nadir was not reached (up to 100 μM). Thus, IBR significantly decreases ADCP by hMDM at concentrations much lower than a more specific BTK inhibitor, Acala. This result suggests that BTK inhibition has little to no effect on ADCP and furthermore suggests that IBR off-target effects decrease ADCP. IBR off-target candidates include other tyrosine kinases in the TEC (tyrosine kinase expressed in hepatocellular carcinoma) family. These data suggest that a a highly selective BTK inhibitor with little effect on ADCP could be a more suitable drug to combine with therapeutic mAb(s). Disclosures Chu: Pfizer: Equity Ownership; Acerta Pharma: Research Funding. VanDerMeid:AstraZeneca: Research Funding. Izumi:Acerta Pharma: Employment, Equity Ownership, Patents & Royalties: Acalabrutinib patents; AstraZeneca: Equity Ownership. Munugalavadla:Acerta Pharma: Employment; AstraZeneca, Gilead Sciences: Equity Ownership. Barr:TG Therapeutics: Consultancy, Research Funding; Celgene: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; Seattle Genetics: Consultancy; Merck: Consultancy; Genentech: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Astra Zeneca: Consultancy, Research Funding; Janssen: Consultancy; AbbVie: Consultancy. Elliott:Astra Zeneca: Research Funding. Zent:Mentrik Biotech: Research Funding; Astra Zeneca: Research Funding.

Introduction: The standard therapy for early stage, unfavorable risk Hodgkin lymphoma (HL) with disease bulk is combined modality therapy, typically 4-6 cycles of ABVD followed by 30Gy involved-site radiotherapy (ISRT) (Eich JCO 2010). In this pilot study with four sequential cohorts, we studied whether consolidative radiotherapy could be reduced or eliminated in early stage, unfavorable risk HL patients treated with brentuximab vedotin (BV) and AVD chemotherapy. In the first cohort, we demonstrated that BV+AVD and 30Gy ISRT had an acceptable safety profile without significant pulmonary toxicity and promising efficacy (Kumar Blood 2016). In subsequent cohorts, we tested whether the ISRT dose could be reduced to 20Gy (cohort 2), the RT field could be reduced with consolidation volume radiation (CVRT; cohort 3), and whether radiation therapy could be eliminated (cohort 4). Methods: Patients received 4 cycles of BV 1.2 mg/kg with AVD chemotherapy every 2 weeks, followed by 30 Gy ISRT in cohort 1, 20Gy ISRT in cohort 2, 30 Gy CVRT in cohort 3, and no radiotherapy in cohort 4. CVRT targets PET-negative residual masses greater than 1.5cm on post-chemotherapy CT imaging. Eligible patients in cohorts 1-2 included untreated stage I/II, classical HL with any one of the following unfavorable risk factors: bulky disease (MSK criteria: maximal transverse or coronal diameter >7 cm on CT), elevated ESR, extranodal involvement, >2 lymph node sites, or infradiaphragmatic disease. In cohort 3-4, early stage patients with bulky disease by MSK criteria were eligible. PET/CT after 2 and 4 cycles and after ISRT were interpreted with the 5-point Deauville scale (negative=1-3). The primary endpoint of cohort 1 was to evaluate safety and tolerability of the treatment combination, with special attention to pulmonary toxicity; the primary endpoint of cohorts 2-4 was to evaluate preliminary efficacy with the rate of complete responses (CRs) at end of treatment (EOT). Results: In June 2019, the study was fully accrued with 117 patients enrolled across four cohorts. Patients had a median age of 32 (range 18-59), 98% stage II, 86% with MSK-defined disease bulk (>7cm in transverse or coronal dimension), 27% with traditionally defined bulk (>10cm in transverse dimension), 50% elevated ESR, 38% B-symptoms, 21% extranodal involvement, 56% >2 involved lymph node sites, and 3.4% infradiaphragmatic disease. 26 patients (22%) had advanced stage disease by German Hodgkin Study Group criteria: IIBX (n=16), IIBE (n=5), and IIBXE (n=6). Of the patients enrolled in cohorts 1-3 with interim PET imaging, 85% and 91% achieved a negative PET scan after 2 and 4 cycles of therapy, respectively, and 95% achieved a CR at EOT. In cohort 4, 24 of the 29 enrolled patients have completed 4 cycles of therapy. Thus far, 93% of patients achieved a negative PET-2 scan (25 of 27 patients), 77% of patients achieved a negative PET-4 scan (17 of 22 patients), and 91% achieved a CR at EOT (20 of 22 patients). The remaining two patients with equivocal PET-4 results will have repeat short-interval scans to clarify EOT response. The overall median follow-up of survivors is 29 months: 56 months for cohort 1, 38 months for cohort 2, 24 months for cohort 3, and 5 months for cohort 4. Seven events have occurred in the study thus far. In cohort 1, two patients had primary refractory disease after chemotherapy and were treated off study. In cohort 2, one patient in remission died in a motor vehicle accident and one late relapse occurred at 34 months. In cohort 3, two patients had primary refractory HL after CVRT and one relapse occurred at 9 months. Overall, the 2-year PFS is 94% (95% CI 0.90, 0.99), see Figure. Across all 4 cohorts, the BV+AVD treatment was well-tolerated; the most common toxicities were peripheral neuropathy, abdominal pain, and neutropenia that were generally mild-moderate in severity, reversible, and manageable. Conclusion: BV+AVD x 4 cycles is an active treatment program for early stage, unfavorable risk HL, including patients with bulky disease. The efficacy of BV+AVD in this setting has facilitated a safe reduction in radiation dose and field evidenced by excellent and similar outcomes across the first 3 cohorts. With substantial follow-up, 20Gy ISRT appears equivalent to 30Gy ISRT following BV+AVD. The preliminary outcomes from the final cohort with chemotherapy alone are also promising, however, follow-up is short. Updated response data will be presented at the meeting. Disclosures Kumar: Seattle Genetics: Research Funding. Casulo:Gilead: Honoraria, Other: Travel, accommodation, expenses; Roche: Other: Travel, accommodation, expenses; Celgene: Research Funding. Advani:Kyowa Kirin Pharmaceutical Developments, Inc.: Consultancy; Cell Medica, Ltd: Consultancy; Kura: Research Funding; Merck: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Stanford University: Employment, Equity Ownership; Seattle Genetics: Consultancy, Research Funding; Agensys: Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Infinity Pharma: Research Funding; Forty-Seven: Research Funding; Gilead Sciences, Inc./Kite Pharma, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Regeneron: Research Funding; Janssen: Research Funding; Millennium: Research Funding; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celmed: Consultancy, Membership on an entity's Board of Directors or advisory committees. Budde:F. Hoffmann-La Roche Ltd: Consultancy. Barr:Janssen: Consultancy; Astra Zeneca: Consultancy, Research Funding; Verastem: Consultancy; Gilead: Consultancy; AbbVie: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Celgene: Consultancy; Merck: Consultancy; Seattle Genetics: Consultancy; Genentech: Consultancy. Batlevi:Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Friedberg:Acerta: Other: Data & Safety Monitoring Committee; Bayer: Honoraria, Other: Data & Safety Monitoring Committee. Horwitz:Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Consultancy; Mundipharma: Consultancy; Aileron: Research Funding; Infinity/Verastem: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Innate Pharma: Consultancy; Innate Pharma: Consultancy; Seattle Genetics: Consultancy, Research Funding; Millennium/Takeda: Consultancy, Research Funding; Astex: Consultancy; Infinity/Verastem: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Trillium: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy; Kyowa Hakko Kirin: Consultancy; Trillium: Research Funding; Affimed: Consultancy; Innate Pharma: Consultancy; Affimed: Consultancy; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Miragen: Consultancy; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astex: Consultancy; Celgene: Consultancy, Research Funding; Infinity/Verastem: Consultancy, Research Funding; Infinity/Verastem: Consultancy, Research Funding; Innate Pharma: Consultancy; Kura: Consultancy; Kyowa Hakko Kirin: Consultancy; Kyowa Hakko Kirin: Consultancy; Millennium/Takeda: Consultancy, Research Funding; Millennium/Takeda: Consultancy, Research Funding; Affimed: Consultancy; Miragen: Consultancy; Miragen: Consultancy; Portola: Consultancy; Trillium: Research Funding; Mundipharma: Consultancy; Portola: Consultancy; Astex: Consultancy; Aileron: Research Funding; Aileron: Research Funding; Celgene: Consultancy, Research Funding; Forty-Seven: Research Funding; Trillium: Research Funding; Forty-Seven: Research Funding; Forty-Seven: Research Funding; Aileron: Research Funding; Portola: Consultancy; ADCT Therapeutics: Research Funding; Affimed: Consultancy; Mundipharma: Consultancy; ADCT Therapeutics: Research Funding; ADCT Therapeutics: Research Funding; ADCT Therapeutics: Research Funding; Portola: Consultancy; Forty-Seven: Research Funding; Miragen: Consultancy; Kura: Consultancy; Kura: Consultancy; Kura: Consultancy; Kyowa Hakko Kirin: Consultancy; Millennium/Takeda: Consultancy, Research Funding; Corvus Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding. Matasar:Genentech, Inc.: Consultancy, Honoraria, Other: Travel, accommodation, expenses , Research Funding; Bayer: Consultancy, Honoraria, Other; Roche: Consultancy, Honoraria, Other: Travel, accommodation, expenses , Research Funding; Merck: Consultancy, Equity Ownership; Juno Therapeutics: Consultancy; Teva: Consultancy; Rocket Medical: Consultancy, Research Funding; Bayer: Other: Travel, accommodation, expenses; Janssen: Honoraria, Research Funding; Pharmacyclics: Consultancy, Honoraria, Research Funding; GlaxoSmithKline: Honoraria, Research Funding; Daiichi Sankyo: Consultancy; Seattle Genetics: Consultancy, Honoraria, Other: Travel, accomodation, expenses, Research Funding. Moskowitz:Erytech Pharma: Consultancy; Erytech Pharma: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Takeda Pharmaceuticals: Consultancy; ADC Therapeutics: Consultancy; ADC Therapeutics: Consultancy; Merck: Research Funding; Takeda Pharmaceuticals: Consultancy; Erytech Pharma: Consultancy; ADC Therapeutics: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Merck: Research Funding; ADC Therapeutics: Consultancy; ADC Therapeutics: Consultancy; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Merck: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Merck: Research Funding; Merck: Research Funding; Merck: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Merck: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Erytech Pharma: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Incyte: Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; Incyte: Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; Incyte: Research Funding; Incyte: Research Funding; Incyte: Research Funding; Incyte: Research Funding; Incyte: Research Funding; Incyte: Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Merck: Research Funding; Merck: Research Funding; Erytech Pharma: Consultancy; ADC Therapeutics: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Merck: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; ADC Therapeutics: Consultancy; Takeda Pharmaceuticals: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding; Incyte: Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; ADC Therapeutics: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Erytech Pharma: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Erytech Pharma: Consultancy; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Cell Medica: Consultancy; miRagen Therapeutics Inc: Consultancy, Research Funding; Cell Medica: Consultancy; Cell Medica: Consultancy; miRagen Therapeutics Inc: Consultancy, Research Funding; ADC Therapeutics: Consultancy; ADC Therapeutics: Consultancy; Cell Medica: Consultancy; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Takeda Pharmaceuticals: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; ADC Therapeutics: Consultancy; ADC Therapeutics: Consultancy; Merck: Research Funding; Erytech Pharma: Consultancy; Erytech Pharma: Consultancy; Erytech Pharma: Consultancy; Erytech Pharma: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; Cell Medica: Consultancy; Incyte: Research Funding; Incyte: Research Funding; Incyte: Research Funding; Incyte: Research Funding; Takeda Pharmaceuticals: Consultancy; Cell Medica: Consultancy; Merck: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Kyowa Hakko Kirin Pharma: Consultancy, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Takeda Pharmaceuticals: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Merck: Research Funding; Erytech Pharma: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; Incyte: Research Funding; Incyte: Research Funding; miRagen Therapeutics Inc: Consultancy, Research Funding; Erytech Pharma: Consultancy; ADC Therapeutics: Consultancy; Merck: Research Funding; Merck: Research Funding; Erytech Pharma: Consultancy; Erytech Pharma: Consultancy; ADC Therapeutics: Consultancy; Seattle Genetics: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; ADC Therapeutics: Consultancy. Noy:Prime Oncology: Honoraria; NIH: Research Funding; Medscape: Honoraria; Janssen: Consultancy; Pharamcyclics: Research Funding; Raphael Pharma: Research Funding. Palomba:Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; STRAXIMM: Membership on an entity's Board of Directors or advisory committees; Kite Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Evelo: Equity Ownership; MSK (IP for Juno and Seres): Patents & Royalties; Noble Insights: Consultancy; Merck & Co Inc.: Consultancy; Seres Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Hemedicus: Speakers Bureau. Straus:Elsevier (PracticeUpdate): Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Hope Funds for Cancer Research: Membership on an entity's Board of Directors or advisory committees. Younes:Roche: Consultancy, Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Curis: Honoraria, Research Funding; Merck: Honoraria, Research Funding; Abbvie: Honoraria; Takeda: Honoraria; Pharmacyclics: Research Funding; AstraZeneca: Research Funding; Genentech: Research Funding; Biopath: Consultancy; Xynomics: Consultancy; Epizyme: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; HCM: Consultancy; BMS: Research Funding; Syndax: Research Funding. Zelenetz:Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics/AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; DAVA Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees. Moskowitz:ADC Therapeutics: Research Funding; Merck: Consultancy, Research Funding; Seattle Genetics, Inc.: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Celgene: Consultancy; Pharmacyclics: Research Funding.

BACKGROUND Novel agents have changed the treatment landscape in chronic lymphocytic leukemia (CLL), however little has been reported about real-world treatment sequence patterns and associated outcomes post-introduction of novel agents. Studies have demonstrated that venetoclax is effective for patients (pts) who have discontinued ibrutinib, however treatments and outcomes post-venetoclax discontinuation remain unclear. The objective of this study was to examine real-world treatment sequence patterns post-introduction of novel agents and specifically understand treatment sequencing following venetoclax. METHODS The CLL Collaborative Study of Real-World Evidence (CORE) is a retrospective, multicenter, collaborative observational study of pts with CLL/small lymphocytic leukemia (SLL). For this analysis, adult pts were eligible for inclusion if they started therapy for CLL/SLL in the relapsed/refractory setting after February 12, 2014 (FDA approval date of first novel agent for CLL/SLL). Interim data are presented; data collection for this analysis is ongoing and is expected to be completed by October 31, 2019. Treatment sequences were characterized specifically focusing on treatment sequencing following venetoclax and other novel agents (i.e., BCRi: e.g., ibrutinib, idelalisib or acalabrutinib). Clinical response, as assessed by physician, was also reported from medical charts (iwCLL criteria were provided as a reference only). RESULTS Of the 267 pts available at the time of interim data analysis, 231 pts (87%) received a novel agent in at least one line of therapy (first-line: 35 pts [15%]; second-line: 133 pts [58%]; third-line or later: 63 pts [27%]). Among novel agents, ibrutinib was the most commonly used first novel agent for 198 pts (86%) followed by venetoclax for 18 pts (8%) and idelalisib for 12 pts (5%). Of those 267 pts, 143 pts (54%) received chemotherapy/chemoimmunotherapy (CT/CIT) followed by a novel agent; 63 pts (24%) received a novel agent followed by a novel agent; 17 (7%) received a novel agent followed by CT/CIT; and 47 (18%) received a CT/CIT followed by CT/CIT. At the time of this interim data cut there were 220 pts (82%) who received BCRi-based regimens (first-line: 33 pts [15%]; second-line: 123 pts [56%]; third-line or later: 64 pts [29%]) and 62 pts (23%) who received venetoclax-based regimens (first-line: 2 pts [3%]; second-line: 22 pts [36%]; third-line or later: 38 pts [61%]). Of the 220 pts who received BCRi-based regimens, 50 (23%) achieved complete remission (CR) and 83 (38%) achieved partial remission (PR) (responses based on physician assessment). Of the 220 pts, 88 (40%) went on to receive a subsequent line of therapy. The most common subsequent treatments administered were venetoclax containing regimens (n= 34, 39%). Of the 88 pts who received a subsequent line of therapy after BCRi-based regimens, 22 pts (25%) achieved CR and 24 pts (27%) achieved PR. Of the 62 pts who received venetoclax-based regimens, 20 pts (32%) achieved CR and 14 pts (23%) achieved PR. Of the 62 pts, 15 pts (24%) went on to receive a subsequent line of therapy. The most common subsequent treatment administered were BCRi containing regimens (n= 10, 67%) primarily ibrutinib-based. Of the 15 pts receiving a subsequent line of therapy after venetoclax-based regimens, 3 pts (20%) achieved CR and 4 pts (27%) achieved PR. While preliminary results are encouraging, further data collection efforts are ongoing and will be included for presentation to confirm the results and outcomes associated with different sequencing options. CONCLUSIONS The treatment paradigm is evolving with the introduction of novel agents. Results from this study will provide a baseline description of treatment sequence patterns enabling clinicians to benchmark the impact of the introduction of novel agents and associated outcomes. Early evidence from these results also suggests that novel agents are most commonly introduced during second line treatment and that other novel agents, including ibrutinib, following venetoclax treatment are being utilized in the real-world settings. Table. Disclosures Mato: Pharmacyclics: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; LOXO: Consultancy, Research Funding; DTRM Biopharma: Research Funding; Johnson & Johnson: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member , Research Funding; Acerta: Consultancy; Janssen: Consultancy; Gilead: Research Funding; AstraZeneca: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Celgene: Consultancy. Sail:AbbVie: Employment, Other: may hold stock or stock options. Yazdy:Genentech: Research Funding; Octapharma: Consultancy; Abbvie: Consultancy; Bayer: Honoraria, Speakers Bureau. Hill:Amgen: Research Funding; Seattle Genetics: Consultancy, Honoraria; Celegene: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Research Funding; Kite: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; TG therapeutics: Research Funding; Takeda: Research Funding; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Shadman:Bigene: Research Funding; TG Therapeutics: Research Funding; AbbVIe: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding; AstraZeneca: Consultancy; Sound Biologics: Consultancy; Pharmacyclics: Consultancy, Research Funding; ADC Therapeutics: Consultancy; Atara: Consultancy; Verastem: Consultancy; Mustang Biopharma: Research Funding; Gilead: Research Funding; Merck: Research Funding; Acerta: Research Funding; Emergent: Research Funding; Celgene: Research Funding; Sunesis: Research Funding. Manzoor:AbbVie: Employment, Other: and may hold stock or stock options. Tuncer:Abbvie: Membership on an entity's Board of Directors or advisory committees; 2018 Steering Committee: Other: reimbursement for travel to the steering committee at ASH. Allan:Janssen: Consultancy, Honoraria; Acerta Pharma: Consultancy; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie company: Consultancy; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Ujjani:PCYC: Research Funding; Pharmacyclics: Honoraria; AbbVie: Honoraria, Research Funding; Genentech: Honoraria; Atara: Consultancy; Astrazeneca: Consultancy; Gilead: Consultancy. Sharmokh:AbbVie: Employment, Other: may hold stock or stock options. Jiang:AbbVie: Employment, Other: and may hold stock or stock options. Pena:AbbVie: Employment, Other: and may hold stock or stock options. Marshall:AbbVie: Employment, Other: and may hold stock or stock options. Nielsen:AbbVie: Employment, Other: and may hold stock or stock options. Barr:Janssen: Consultancy; Astra Zeneca: Consultancy, Research Funding; Verastem: Consultancy; Genentech: Consultancy; Seattle Genetics: Consultancy; Merck: Consultancy; Celgene: Consultancy; TG Therapeutics: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; AbbVie: Consultancy; Gilead: Consultancy. Brown:Pfizer: Consultancy; Pharmacyclics: Consultancy; Sunesis: Consultancy; Teva: Honoraria; TG Therapeutics: Consultancy; Verastem: Consultancy, Research Funding; Sun: Research Funding; Sun Pharmaceuticals, Inc: Research Funding; Morphosys: Other: Data safety monitoring boards ; Acerta Pharma: Consultancy; AstraZeneca: Consultancy; BeiGene: Consultancy; Catapult Therapeutics: Consultancy; Dynamo Therapeutics: Consultancy; Genentech/Roche: Consultancy; Gilead: Consultancy, Research Funding; Invectys: Other: other; Janssen: Honoraria; Kite: Consultancy, Research Funding; Loxo: Consultancy, Research Funding; Novartis: Consultancy; Octapharma: Consultancy. Schuh:Pharmacyclics: Consultancy, Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Janssen: Speakers Bureau; Verastem: Speakers Bureau; Kite: Speakers Bureau; Gilead: Speakers Bureau; Seattle Genetics: Speakers Bureau; Jazz Pharmaceuticals: Speakers Bureau; Bristol-Myers Squibb: Research Funding. Eyre:Janssen: Honoraria, Other: travel support; Gilead: Honoraria, Other: travel support; AbbVie: Honoraria, Other: travel support. Wierda:Pharmacyclics LLC: Research Funding; Juno Therapeutics: Research Funding; Gilead Sciences: Research Funding; Miragen: Research Funding; Cyclcel: Research Funding; Oncternal Therapeutics Inc.: Research Funding; GSK/Novartis: Research Funding; Genentech: Research Funding; Xencor: Research Funding; Acerta Pharma Inc: Research Funding; KITE pharma: Research Funding; Sunesis: Research Funding; Loxo Oncology Inc.: Research Funding; Janssen: Research Funding; AbbVie: Research Funding. Skarbnik:Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Verastem Oncology: Honoraria, Research Funding, Speakers Bureau; Kite Pharma: Honoraria, Speakers Bureau; Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Acerta: Research Funding; Genentech: Honoraria, Speakers Bureau; CLL Society: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Speakers Bureau; Novartis: Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Roeker:Abbott Laboratories: Equity Ownership; AbbVie: Equity Ownership. Bannerji:Gilead: Other: travel support; Celgene: Consultancy; Celgene: Consultancy; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Merck: Other: travel support, Patents & Royalties: IP rights; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Pharmacyclics: Other: travel support; AbbVie, Inc: Consultancy; Pharmacyclics: Other: travel support; Gilead: Other: travel support; AbbVie, Inc: Consultancy, travel support; Merck: Other: travel support, Patents & Royalties: IP rights. Pauff:AbbVie Inc: Employment, Other: may own stock or stock options. Schuster:Novartis, Nordic Nanovector, and Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: a patent (with royalties paid to Novartis) on combination therapies of CAR and PD-1 inhibitors.; Novartis, Celgene, Genentech, Merck, Pharmacyclics, Acerta, and Gilead: Other: Grants, Research Funding; Nordic Nanovector, Pfizer, AstraZeneca, Loxo Oncology, Acerta, and Celgene: Honoraria. Follows:Roche: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Honoraria, Speakers Bureau. Cheson:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Symbios: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trillium: Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Portola: Research Funding; Gilead: Research Funding; Epizyme: Research Funding. Eichhorst:Gilead Sciences, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BeiGene: Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; ArQule: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Brander:Genentech: Consultancy, Honoraria, Research Funding; DTRM Biopharma: Research Funding; TG Therapeutics: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Research Funding; BeiGene: Research Funding; Novartis: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy; AbbVie: Consultancy, Honoraria, Research Funding; Acerta: Research Funding; Tolero: Research Funding; Teva: Consultancy, Honoraria; MEI: Research Funding. Pivneva:AbbVie: Other: employee of Analysis Group, Inc., which has received consultancy fees from AbbVie. Lamanna:AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Verastem: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Bei-Gene: Research Funding; TG Therapeutics: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Roche-Genentech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background:Despite the effectiveness of novel agents in treating CLL, single agent use requires prolonged administration which can lead to drug resistance, toxicity and considerable cost over time. Combinations may provide deeper prolonged remissions using defined treatment durations. Umbralisib (Umbra) is a novel, highly-specific PI3Kδ inhibitor and ublituximab (Ubli) is a chimeric monoclonal antibody targeting a unique epitope on CD20 and glycoengineered to enhance antibody dependent cellular toxicity. Combining these agents with the BCL2 inhibitor venetoclax (Ven) may prevent drug resistance (Choudhary, Cell Death Dis 2015), avoid tumor lysis syndrome (TLS) and achieve undetectable minimal residual disease (MRD). This phase 1/2 trial evaluates the safety and efficacy of Umbra + Ubli + Ven for 12 cycles followed by MRD evaluation in relapsed or refractory CLL patients (pts). Methods:Pts received three 28-day cycles of Umbra daily along with Ubli, administered weekly during cycle 1, then once during cycles 2 and 3, followed by Umbra + Ven for 9 additional cycles. During the phase 1 study, dose levels including Umbra 600mg and 800mg were tested with Ubli 900mg and Ven, increased in standard fashion to 400 mg during cycle 4. The primary endpoint for phase 1 was safety; the primary endpoint for phase 2 was complete remission (CR) rate by iwCLL criteria. MRD negativity ( Results: 21 pts have been treated to date: 9 in phase 1 and 12 in phase 2. Baseline demographics were as follows: male/female (12/9), median age 65 yrs (range 49-83), median prior therapies 2 (1-5). 9 pts had prior ibrutinib of which 4 were BTK inhibitor refractory. BTK resistance mutations were found in 2 pts. High risk genetic features included unmutated IGHV genes (11 pts), del17p or del11q (7 pts), TP53 mut (1 pt), NOTCH1 mut (4 pts) and SF3B1 mut (1 pt). Baseline TLS risk was high, medium and low risk in 2, 12 and 7 pts respectively. During dose escalation, 3 pts were treated using Umbra 600mg and subsequently 6 pts using Umbra 800mg. No DLTs occurred, and the MTD was not reached. As such, the phase 2 dose used was Ubli 900 mg + Umbra 800 mg with venetoclax, undergoing ramp up to 400 mg. For all pts treated to date, the most common AEs were (all causality and all grade; >20% of pts) infusion reactions (62%), thrombocytopenia (57%), neutropenia (52%), anemia (52%), fatigue (52%), ALT or AST increase (43%), nausea (33%), diarrhea (29%) and headache (24%). Grade 1 creatinine increase, hypocalcemia and hyperkalemia were observed in 12 (57%), 6 (29%) and 5 (24%) of pts respectively. These AEs predominately occurred outside of venetoclax ramp up. Grade 3/4 AE's occurring in ≥ 2 pts included neutropenia (n=4, 19%), infusion reaction (n=2, 10%) and thromboembolism (n=2, 10%). No grade ≥ 3 PI3Kδ-associated toxicities were noted (0 events of pneumonitis, colitis or grade 3/4 transaminitis). No events of TLS were observed. One pt discontinued study treatment due to grade 3 rash. All pts were converted to low TLS risk after 3 cycles of Umbra + Ubli, except for 1 pt who remained medium risk after discontinuing Ubli secondary to a grade 3 infusion reaction, allowing outpatient venetoclax initiation in all pts. In evaluable pts, the overall response rate was 85% (11/13) after cycle 3, 100% (9/9) after cycle 7 and 100% (5/5) after cycle 12. Of the 5 pts who finished 12 cycles of therapy, a median reduction in nodal disease of 87% occurred resulting in 2 CRs and 3 PRs by iwCLL criteria. 4 pts have undetectable MRD ( Conclusion: We established the phase 2 dose of Umbra + Ubli + Ven and demonstrated good tolerability in pts with relapsed or refractory CLL. Preliminary results suggest that this chemotherapy-free regimen can provide undetectable MRD after only 12 cycles, representing an effective treatment plan for this population. Ongoing enrollment is focused on pts who have relapsed after BTK inhibitors and a multi-center trial is planned to further develop the triplet regimen. Figure Disclosures Barr: Gilead: Consultancy; AbbVie: Consultancy; Janssen: Consultancy; Verastem: Consultancy; Seattle Genetics: Consultancy; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy; Astra Zeneca: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding. Hill:TG therapeutics: Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Research Funding; Kite: Consultancy, Honoraria; Amgen: Research Funding; Takeda: Research Funding; Seattle Genetics: Consultancy, Honoraria; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Honoraria; Celegene: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Ma:Janssen: Consultancy, Speakers Bureau; Beigene: Research Funding; Pharmacyclics: Consultancy, Research Funding, Speakers Bureau; Novartis: Research Funding; Xeme: Research Funding; Juno: Research Funding; Incyte: Research Funding; Kite: Consultancy; Genentech: Consultancy; Acerta: Research Funding; Bioverativ: Consultancy; Astra Zeneca: Consultancy, Research Funding, Speakers Bureau; Abbvie: Research Funding; Gilead: Research Funding. Liesveld:Abbvie: Membership on an entity's Board of Directors or advisory committees; Onconova: Other: Data safety monitoring board. Sportelli:TG Therapeutics: Employment. Miskin:TG therapeutics Inc.: Employment, Equity Ownership. Weiss:TG Therapeutics: Employment. Friedberg:Acerta: Other: Data & Safety Monitoring Committee; Bayer: Honoraria, Other: Data & Safety Monitoring Committee. Zent:Astra Zeneca: Research Funding; Mentrik Biotech: Research Funding. OffLabel Disclosure: umbralisib and ublituximab as treatment of CLL

Background : Ibrutinib is the only once-daily Bruton's tyrosine kinase inhibitor with significant progression-free survival (PFS) benefit demonstrated in 5 randomized phase 3 studies in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) compared with standard-of-care chemotherapy and/or immunotherapy (RESONATE, RESONATE-2, iLLUMINATE, Alliance 041202, and ECOG 1912), and significant overall survival (OS) benefit in 3 of these studies. To understand how treatment with single-agent ibrutinib in earlier lines impacts patient outcomes, we evaluated long-term follow-up data from RESONATE and RESONATE-2 to compare efficacy and safety by number of prior lines of therapy. Methods : This integrated analysis included patients treated with single-agent ibrutinib in the first-line (RESONATE-2, NCT01722487) and relapsed/refractory (R/R; RESONATE, NCT01578707) settings. R/R patients were grouped by number of prior lines of therapy (1-2 vs ≥3). Patients with del(17p) were excluded from this analysis given their exclusion from RESONATE-2. Patients with high-risk prognostic features were defined as having TP53 mutation, del(11q), and/or unmutated IGHV. Outcomes included investigator-assessed PFS and objective response rate (ORR), OS, and safety. Results : This analysis of 271 patients included 136 patients in the first-line and 135 patients in the R/R groups (1-2 prior: n=68; ≥3 prior: n=67). Patients in the first-line group were older (median age [range], 73 years [65-89]) than those with 1-2 prior lines (65 years [30-86]) and ≥3 prior lines (67 years [44-83]). The proportion of patients with high-risk prognostic features was lower in the first-line group (first-line: 54%; 1-2 prior: 81%; ≥3 prior: 76%). Median follow-up was 59.8 months for first-line, 66.2 months for 1-2 prior, and 65.1 for ≥3 prior. Median PFS was not reached (NR) for first-line or 1-2 prior lines and was 40.1 months for ≥3 prior lines (Figure 1A). A greater proportion of patients treated with ibrutinib in earlier lines remained progression-free or alive at 60 months (first-line: 70%; 1-2 prior: 60%; ≥3 prior: 33%). First-line treatment resulted in a 34% reduction in risk of disease progression or death compared to 1-2 prior lines (HR: 0.66 [95% CI, 0.40-1.09]). PFS was significantly prolonged for first-line vs ≥3 prior lines (HR: 0.32 [95% CI, 0.21-0.49]) and 1-2 prior vs ≥3 prior lines (HR: 0.48 [95% CI, 0.30-0.77]). For patients with high-risk prognostic features, median PFS was NR for first-line or 1-2 prior lines and was 42.5 months for ≥3 prior lines (Figure 1B); treatment in earlier lines resulted in better PFS for these patients (first-line vs 1-2 prior, HR: 0.64 [95% CI, 0.35-1.18]; first-line vs ≥3 prior, HR: 0.33 [95% CI, 0.19-0.57]; 1-2 prior vs ≥3 prior HR: 0.51 [95% CI, 0.30-0.87]). Median OS for the overall population was NR (range, 0.10+-66.04+) for first-line, NR (5.98-71.56+) for 1-2 prior, and 67.4 months (1.15-69.78+) for ≥3 prior lines. The ORR was 91%, 94%, and 82% for first-line, 1-2 prior, and ≥3 prior lines, respectively. The CR rate (CR+CR with incomplete marrow recovery) was highest for the first-line group (first-line: 30%; 1-2 prior: 12%; ≥3 prior: 10%). At the time of analysis, 58% of patients remain on ibrutinib treatment in the first-line group. Prior to study closure, 38% of patients with 1-2 prior and 18% of patients with ≥3 prior lines remained on ibrutinib treatment. In the overall population, 8 patients (6%) in the first-line group discontinued due to progressive disease while it was the most common reason for discontinuation for patients with 1-2 (n=15, 22%) and ≥3 prior lines (n=25, 37%). Across all three groups, 52 patients (19%) discontinued due to adverse events (AEs) (first-line: n=29, 21%; 1-2 prior: n=13, 19%; ≥3 prior: n=10, 15%). AEs leading to dose reduction occurred in 20% of first-line, 13% of 1-2 prior, and 22% of ≥3 prior lines. Conclusions : Overall, this integrated analysis of data with up to 6 years of long-term follow-up demonstrates that using single-agent ibrutinib in earlier lines of treatment results in better PFS, OS, and ORR with sustained efficacy for patients with CLL, including patients with high-risk prognostic features. During this extended follow-up, only 6% of patients treated in the first-line setting discontinued due to progressive disease. Ibrutinib was well tolerated with only 19% of patients across all lines of therapy discontinuing due to AEs. Disclosures Barr: Gilead: Consultancy; Verastem: Consultancy; Seattle Genetics: Consultancy; AbbVie: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Astra Zeneca: Consultancy, Research Funding. Tedeschi:Janssen spa: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Consultancy; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; SUNESIS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BeiGene: Honoraria; AstraZeneca: Membership on an entity's Board of Directors or advisory committees. Munir:AbbVie: Honoraria; Alexion: Honoraria; Gilead: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Roche: Honoraria; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sunesis: Consultancy; Pharmacyclics: Other: TBC; Acerta: Membership on an entity's Board of Directors or advisory committees. Hillmen:Acerta: Membership on an entity's Board of Directors or advisory committees; Apellis: Research Funding; Gilead: Research Funding; Roche: Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Expenses, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Expenses, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding. Woyach:Janssen: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; AbbVie: Research Funding; Karyopharm: Research Funding; Loxo: Research Funding; Morphosys: Research Funding; Verastem: Research Funding. Byrd:Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Acerta: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; Ohio State University: Patents & Royalties: OSU-2S; Genentech: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Genentech: Research Funding; BeiGene: Research Funding. Ghia:ArQule: Consultancy, Honoraria; BeiGene: Consultancy, Honoraria; Juno/Celgene: Consultancy, Honoraria; Dynamo: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Acerta/AstraZeneca: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Sunesis: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy. Mulligan:AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Clinical Trial Participant, Research Funding, Speakers Bureau; GSK: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Clinical Trial Participant, Research Funding, Speakers Bureau; Roche: Consultancy, Honoraria, Other: Clinical Trial participant, Research Funding, Speakers Bureau; Commonwealth Serum Laboratories (CSL): Other: Clinical Trial participant; Sanofi-Aventis: Other: Clinical Trial participant; Acerta: Other: Clinical Trial participant. Dai:AbbVie: Equity Ownership; Celgene: Equity Ownership; Exelixis: Equity Ownership; Gilead: Equity Ownership; GSK: Equity Ownership; Pharmacyclics LLC, an AbbVie Company: Employment. Amaya-Chanaga:AbbVie: Equity Ownership; Pharmacyclics LLC, an AbbVie Company: Employment. Dean:AbbVie: Equity Ownership; Pharmacyclics LLC, an AbbVie Company: Employment. o'Brien:Pfizer: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy; Acerta: Research Funding; Alexion: Consultancy; Amgen: Consultancy; Aptose Biosciences, Inc: Consultancy; Astellas: Consultancy; Celgene: Consultancy; Eisai: Consultancy; Gilead: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Kite: Research Funding; Janssen: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Regeneron: Research Funding; Sunesis: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Vaniam Group LLC: Consultancy; Verastem: Consultancy.

BACKGROUND The recent approval of novel agents (NAs) has changed the treatment landscape in chronic lymphocytic leukemia (CLL), however, there remains uncertainty regarding treatment discontinuation patterns in real-world (RW) settings. This study assessed patterns of and reasons for discontinuation for patients (pts) treated with chemotherapy/chemoimmunotherapy (CT/CIT) and NAs in first (1L) and second (2L) lines of therapy in CLL. METHODS The CLL Collaborative Study of Real-World Evidence (CORE) study is a retrospective, multicenter, observational study. Adult CLL patients (pts) were included if they were diagnosed with CLL, initiated 1L or 2L therapy for CLL on/after 01/01/2012 (excluding lines of therapy received as part of clinical trials). Discontinuation patterns were assessed among CT/CIT and NAs, more specifically in four treatment cohorts: fludarabine+cyclophosphamide+rituximab (FCR), bendamustine+rituximab (BR), B-cell receptor inhibitors (BCRi)-based (e.g., acalabrutinib, ibrutinib, or idelalisib) and venetoclax-based regimens. Treatment discontinuation was operationally defined as ending therapy for reason(s) other than completion of planned duration of therapy. RESULTS Of 671 pts receiving 1L therapy, 81 (12%) received FCR (median age=58, 70% males); 153 (23%) BR (median age=63, 61% males), 255 (38%) BCRi-based (median age=65, 65% males); and 13 (2%) venetoclax-based (median age=59, 54% males). The remaining 169 pts received other regimens (e.g., other CT/CIT). The most common BCRi-based therapy in 1L was ibrutinib-containing regimens (97%). Median duration of follow-up was 24, 27, 11 and 8 months for FCR, BR, BCRi-based and venetoclax-based regimens, respectively. Treatment discontinuation occurred in 18 (22%), 41 (27%), 51 (20%) and 4/13 pts receiving FCR, BR, BCRi-based and venetoclax-based regimens, respectively. The most common reason for discontinuation in FCR (11/18 pts; 61%), BR (15/41 pts; 37%) and BCRi-based (24/51 pts; 47%) cohorts was adverse events (AEs), with >70% being severe AEs in each cohort. Common AEs leading to discontinuations were hematological abnormalities (e.g., neutropenia, thrombocytopenia) in the FCR (6/18 pts; 33%) and BR (6/41 pts; 15%) cohorts. In the BCRi-based cohort the most common AEs leading to discontinuations were cardiac (4/51 pts; 8%), skin and subcutaneous tissue disorders (e.g., rash; 6/51 pts; 12%), hemorrhage/bleeding (3/51; 6%), and musculoskeletal and connective tissue disorders (3/51; pts; 6%). For the relatively small number of pts treated with venetoclax-based regimens and discontinued, disease progression was the common reason for discontinuations (3/4 pts); no pts discontinued venetoclax-based regimens due to adverse events. In the relapsed/refractory setting specifically in 2L, 15 (7%), 113 (56%) and 16 (8%) pts received BR, BCRi-based and venetoclax-based regimen respectively, of which the most common BCRi-based therapy regimen was ibrutinib-based (95%). Treatment discontinuation occurred in 5/15 pts (33%), 27/113 pts (24%) and 4/16 pts (25%) receiving BR, BCRi-based and venetoclax-based regimens, respectively. The most common reason for discontinuations were severe AEs for BR (3/5 pts) and BCRi-based (13/27 pts) cohorts and disease progression for venetoclax-based regimens (2/4). CONCLUSIONS Despite the relatively short follow-up, in both 1L and 2L, similar discontinuation patterns emerge. CT/CIT is often discontinued prior to completion of planned cycles of therapy, suggesting that these regimens are difficult to tolerate. Additionally, treat to progression BCRi-based regimens are also discontinued for severe AEs, discordant to results from clinical trials. With a small cohort and limited information collected, results on venetoclax discontinuation warrants additional studies. Well tolerated chemotherapy-free combinations with finite treatment duration in treatment naïve and relapsed/refractory settings may limit continuous exposure to treatment and prevent discontinuations due to AEs. Table Disclosures Shadman: Atara: Consultancy; Gilead: Research Funding; TG Therapeutics: Research Funding; Bigene: Research Funding; Celgene: Research Funding; Acerta: Research Funding; Emergent: Research Funding; Sunesis: Research Funding; Merck: Research Funding; AbbVIe: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding; AstraZeneca: Consultancy; Sound Biologics: Consultancy; Mustang Biopharma: Research Funding; Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy; ADC Therapeutics: Consultancy. Sail:AbbVie: Employment, Other: and may hold stock or stock options. Manzoor:AbbVie: Employment, Other: and may hold stock or stock options. Yazdy:Genentech: Research Funding; Octapharma: Consultancy; Abbvie: Consultancy; Bayer: Honoraria, Speakers Bureau. Hill:AstraZeneca: Consultancy, Honoraria; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG therapeutics: Research Funding; Celegene: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Kite: Consultancy, Honoraria; Genentech: Consultancy, Research Funding; Takeda: Research Funding; Amgen: Research Funding. Tuncer:Abbvie: Membership on an entity's Board of Directors or advisory committees; 2018 Steering Committee: Other: reimbursement for travel to the steering committee at ASH. Allan:Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie company: Consultancy; Janssen: Consultancy, Honoraria; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta Pharma: Consultancy; Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy. Ujjani:Atara: Consultancy; Gilead: Consultancy; Astrazeneca: Consultancy; Genentech: Honoraria; PCYC: Research Funding; Pharmacyclics: Honoraria; AbbVie: Honoraria, Research Funding. Emechebe:AbbVie: Employment, Other: and may hold stock or stock options. Kamalakar:AbbVie: Employment, Other: and may hold stock or stock options. Sharmokh:AbbVie: Employment, Other: may hold stock or stock options. Jiang:AbbVie: Employment, Other: and may hold stock or stock options. Pena:AbbVie: Employment, Other: and may hold stock or stock options. Marshall:AbbVie: Employment, Other: and may hold stock or stock options. Nielsen:AbbVie: Employment, Other: and may hold stock or stock options. Barr:Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; AbbVie: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Merck: Consultancy; Seattle Genetics: Consultancy; Genentech: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Astra Zeneca: Consultancy, Research Funding. Brown:Dynamo Therapeutics: Consultancy; Catapult Therapeutics: Consultancy; Invectys: Other: other; Janssen: Honoraria; Kite: Consultancy, Research Funding; Loxo: Consultancy, Research Funding; Novartis: Consultancy; Octapharma: Consultancy; Verastem: Consultancy, Research Funding; TG Therapeutics: Consultancy; Teva: Honoraria; Sunesis: Consultancy; Pfizer: Consultancy; Pharmacyclics: Consultancy; Gilead: Consultancy, Research Funding; Genentech/Roche: Consultancy; Sun: Research Funding; Sun Pharmaceuticals, Inc: Research Funding; Morphosys: Other: Data safety monitoring boards ; Acerta Pharma: Consultancy; AstraZeneca: Consultancy; BeiGene: Consultancy. Schuh:AbbVie: Consultancy, Speakers Bureau; Kite: Speakers Bureau; Gilead: Speakers Bureau; Seattle Genetics: Speakers Bureau; Jazz Pharmaceuticals: Speakers Bureau; Janssen: Speakers Bureau; Pharmacyclics: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Research Funding; Verastem: Speakers Bureau; Genentech: Consultancy, Speakers Bureau. Eyre:Janssen: Honoraria, Other: travel support; AbbVie: Honoraria, Other: travel support; Gilead: Honoraria, Other: travel support. Lamanna:Celgene: Membership on an entity's Board of Directors or advisory committees; Roche-Genentech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Verastem: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bei-Gene: Research Funding; TG Therapeutics: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees. Wierda:Gilead Sciences: Research Funding; Juno Therapeutics: Research Funding; Oncternal Therapeutics Inc.: Research Funding; Xencor: Research Funding; Janssen: Research Funding; Genentech: Research Funding; AbbVie: Research Funding; GSK/Novartis: Research Funding; Sunesis: Research Funding; Loxo Oncology Inc.: Research Funding; KITE pharma: Research Funding; Acerta Pharma Inc: Research Funding; Miragen: Research Funding; Pharmacyclics LLC: Research Funding; Cyclcel: Research Funding. Skarbnik:Jazz Pharmaceuticals: Speakers Bureau; Kite Pharma: Honoraria, Speakers Bureau; Novartis: Speakers Bureau; CLL Society: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Speakers Bureau; Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Acerta: Research Funding; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Verastem Oncology: Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Roeker:Abbott Laboratories: Equity Ownership; AbbVie: Equity Ownership. Bannerji:Celgene: Consultancy; Celgene: Consultancy; Pharmacyclics: Other: travel support; Merck: Other: travel support, Patents & Royalties: IP rights; AbbVie, Inc: Consultancy; Gilead: Other: travel support; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Merck: Other: travel support, Patents & Royalties: IP rights; Pharmacyclics: Other: travel support; AbbVie, Inc: Consultancy, travel support; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Gilead: Other: travel support. Pauff:AbbVie: Employment, Other: and may hold stock or stock options. Schuster:Novartis: Other: a patent (with royalties paid to Novartis) on combination therapies of CAR and PD-1 inhibitors.; Novartis, Celgene, Genentech, Merck, Pharmacyclics, Acerta, and Gilead: Other: Grants, Research Funding; Nordic Nanovector, Pfizer, AstraZeneca, Loxo Oncology, Acerta, and Celgene: Honoraria; Novartis, Nordic Nanovector, and Pfizer: Membership on an entity's Board of Directors or advisory committees. Follows:Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau. Cheson:Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Symbios: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trillium: Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Portola: Research Funding; Kite: Research Funding; Gilead: Research Funding; Epizyme: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Eichhorst:BeiGene: Research Funding; ArQule: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead Sciences, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Brander:DTRM Biopharma: Research Funding; BeiGene: Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy; Genentech: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria; TG Therapeutics: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Research Funding; Novartis: Consultancy; AbbVie: Consultancy, Honoraria, Research Funding; MEI: Research Funding; Tolero: Research Funding; Acerta: Research Funding. Pivneva:AbbVie: Other: employee of Analysis Group, Inc., which has received consultancy fees from AbbVie. Guerin:AbbVie: Other: employee of Analysis Group, Inc., which has received consultancy fees from AbbVie. Mato:AstraZeneca: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Celgene: Consultancy; Johnson & Johnson: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Gilead: Research Funding; Acerta: Consultancy; Janssen: Consultancy; LOXO: Consultancy, Research Funding; DTRM Biopharma: Research Funding; Genentech: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member, Research Funding.

Introduction Limited stage disease accounts for 30-40% of Diffuse Large B-cell Lymphoma (DLBCL), with better overall survival than advanced stage disease, but with increased late relapses regardless of treatment strategy (Stephens 2016). Preferred treatment for these patients (pts) per NCCN guidelines is abbreviated R-CHOP followed by radiotherapy. Based on promising results of radioimmunotherapy consolidation in SWOG S0313 (Persky 2015), and of PET-directed experience by the BC Cancer Agency (Sehn 2011), we designed a National Clinical Trials Network (NCTN) PET-directed study to tailor therapy after 3 cycles of R-CHOP, to improve outcomes and decrease toxicities. Methods Pts had non-bulky (< 10 cm) stage I/II untreated DLBCL. Mediastinal, HIV-associated, testicular, central nervous system, and indolent lymphoma were excluded. Pts received standard R-CHOP therapy and had an interim PET scan on day 15-18 of cycle 3, which was centrally reviewed in real time. Pts with negative PET scan (Deauville 1-3, iPET-neg) proceeded with 1 additional cycle of R-CHOP. Pts with positive PET scan (Deauville 4-5, iPET-pos) initiated 36 Gy of involved field radiation therapy (IFRT), plus additional boost to FDG-avid area up to 9 Gy, within 5 weeks of 3rd cycle of R-CHOP. This was followed by ibritumomab tiuxetan (IFRT-Zevalin) 3-6 weeks after completing IFRT. Final PET scan was performed 12 weeks after treatment completion. Results The study completed accrual in June 2016. Safety, response, interim PET, and immunohistochemistry-based cell of origin (COO) and MYC/BCL2 analyses were presented previously (Persky 2017, Stephens 2017). Of 159 pts enrolled, 1 was upstaged by PET, and 26 pts were ineligible - due to incorrect histology (mostly concurrent indolent or follicular lymphoma grade 3B) (21), lack of diagnostic tissue submission for central pathology review (3), and bulky disease (2). In 132 eligible pts, median age was 62 years, 62% had stage I, 17% had B symptoms, 14% had elevated LDH, 43% had extranodal involvement, and 66% had exclusive involvement of the head and neck region. Stage modified IPI (smIPI, Miller 1998) was 0 in 27%, 1 in 42%, 2 in 28%, and 3 in 4% of the pts. COO by Lymph2Cx was assessable in 87 pts - 68% were GCB, 23% were ABC, and 9% were unclassifiable. Double protein expressers (MYC and BCL2, DPE) were 16%, while 4 (3%) pts had "double hit" lymphoma (DHL) - 2 with MYC/BCL2 and 2 with MYC/BCL6 rearrangements - none of which were DPE. Of 132 eligible pts, 128 had an interim PET scan centrally reviewed, of which 110 were iPET-neg. Only 18 were iPET-pos, 4 of them due to infection (Deauville X) which were treated as iPET-neg. Of 14 truly iPET-pos pts (11%), 2 refused radiation, and 12 pts received IFRT-Zevalin. Eight pts (67%) converted from PR to CR after IFRT-Zevalin and 4 (33%) had PR, for an overall CR of 92% and PR of 4% (with 4% unevaluable). With median follow up of 4.5 yrs (range 1.1 - 7.5 yrs), only 5 pts progressed and 2 died from lymphoma. Of 5 progressors, 3 received R-CHOP x 4, 1 was iPET-pos but declined radiation, and 1 went off treatment after 1 cycle of R-CHOP. Eleven pts died from non-lymphoma causes, including 1 pt from secondary AML (iPET-neg arm), and 1 of lung adenocarcinoma diagnosed upon iPET. S1001 5-yr PFS estimate is 87% and OS estimate is 90% (figure 1), with iPET-pos and iPET-neg pts having similar outcomes - PFS 86% vs. 88%, OS 93% vs. 91%, respectively. Five-yr PFS by smIPI was 97% for smIPI of 0, 86% for 1-2, and 30% for 3. GCB had 5-yr PFS of 95%, vs. 70% for ABC and 47% for unclassifiable. DPE pts had 5-yr PFS of 70, vs. 89% for non-DPE pts. All 4 DHL pts maintain remission. Conclusions S1001 is the largest US study of limited stage DLBCL in the rituximab era, with best NCTN results in this disease subset. Only 5 patients progressed and 2 died from lymphoma. Our study confirms the distinct biology of limited stage DLBCL, with predominance of GCB origin (68%), and head and neck location (66%). Due to small number of lymphoma events, no strong conclusions about prognostic ability of smIPI, COO, DPE, or DHL, could be made. S1001 demonstrated that 89% of pts maintained excellent outcomes after R-CHOP x 4 with PET-directed therapy. Only 11% of pts were iPET-pos and required radiation, but they also had excellent outcomes. Together with the FLYER trial in younger pts (Poeschel 2018), this NCTN trial establishes R-CHOP x 4 alone as the new standard approach to limited stage disease for majority of the pts. Disclosures Persky: Sandoz: Consultancy; Morphosys: Other: Member, Independent Data Monitoring Committee; Debiopharm: Other: Member, Independent Data Monitoring Committee; Bayer: Consultancy. Stephens:Acerta: Research Funding; Karyopharm: Research Funding; Gilead: Research Funding. Park:BMS: Consultancy, Research Funding; Rafael Pharma: Membership on an entity's Board of Directors or advisory committees; G1 Therapeutics: Consultancy; Teva: Consultancy, Research Funding; Gilead: Speakers Bureau; Seattle Genetics: Research Funding, Speakers Bureau. Bartlett:Seattle Genetics: Research Funding; ADC Therapeutics: Consultancy, Research Funding; Pfizer: Research Funding; Millenium: Research Funding; Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Genenetech: Research Funding; Immune Design: Research Funding; Gilead: Research Funding; Forty Seven: Research Funding; Janssen: Research Funding; Affimed: Research Funding; Merck: Research Funding; Pharmacyclics: Research Funding. Swinnen:Pharmacyclics: Consultancy; AbbVie: Consultancy. Barr:Celgene: Consultancy; Merck: Consultancy; Seattle Genetics: Consultancy; Genentech: Consultancy; Verastem: Consultancy; Gilead: Consultancy; Astra Zeneca: Consultancy, Research Funding; Janssen: Consultancy; AbbVie: Consultancy; Pharmacyclics LLC, an AbbVie company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding. Leonard:Nordic Nanovector: Consultancy; Akcea Therapeutics: Consultancy; BeiGene: Consultancy; Gilead: Consultancy; Miltenyi: Consultancy; ADC Therapeutics: Consultancy; Nordic Nanovector: Consultancy; Akcea Therapeutics: Consultancy; Sandoz: Consultancy; ADC Therapeutics: Consultancy; Miltenyi: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Karyopharm Therapeutics: Consultancy; Epizyme, Inc: Consultancy; Sutro Biopharma: Consultancy; AstraZeneca: Consultancy; AstraZeneca: Consultancy; Bayer Corporation: Consultancy; Bayer Corporation: Consultancy; Celgene: Consultancy; Epizyme, Inc: Consultancy; Celgene: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Merck: Consultancy; MorphoSys: Consultancy; Karyopharm Therapeutics: Consultancy; Gilead: Consultancy; Sutro Biopharma: Consultancy; BeiGene: Consultancy; Merck: Consultancy; MorphoSys: Consultancy; Sandoz: Consultancy. Kahl:TG Therapeutics: Consultancy; ADC Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy; BeiGene: Consultancy. Fisher:Celgene: Consultancy; AstraZeneca: Consultancy; Barclays: Honoraria; prIME: Honoraria. Rimsza:NanoSting: Patents & Royalties: Named inventor on a patent licensed to NanoSting [Institution]. Smith:Portola Pharmaceuticals: Research Funding. Friedberg:Bayer: Honoraria, Other: Data & Safety Monitoring Committee; Acerta: Other: Data & Safety Monitoring Committee. OffLabel Disclosure: Ibritumomab tiuxetan in diffuse large B-cell lymphoma

In this issue of Blood, Mansouri et al1 report on the distribution of NFKBIE aberrations in lymphoid malignancies and suggest they play an important role in lymphomagenesis. They demonstrate a high frequency of NFKBIE deletions in primary mediastinal B-cell lymphoma (PMBL) and report that they predict for poor outcomes in this population.

This multicenter pilot study assessed the safety and efficacy of brentuximab vedotin (BV) and AVD (adriamycin, vinblastine, and dacarbazine) followed by 30 Gy involved site radiation therapy (ISRT). Patients with newly diagnosed, early stage classical Hodgkin lymphoma (HL) with unfavorable-risk features were treated with 4 cycles of BV and AVD. Patients who achieved a negative positron emission tomography (PET) scan (Deauville score of 1-3) received 30 Gy ISRT. Thirty patients received treatment and were assessable for toxicity. Twenty-nine patients completed 4 cycles of BV + AVD, and 25 patients BV + AVD + 30 Gy ISRT. No clinically significant noninfectious pneumonitis was observed. Serious adverse events (≥grade 3) were reported in 4 patients, including febrile neutropenia, peripheral neuropathy, and hypertension. After 2 and 4 cycles of BV + AVD, 90% (26 of 29) and 93% (27 or 29) of patients achieved a negative PET scan, respectively. Two patients with biopsy-proven primary refractory HL were treated off-study. All 25 patients who completed BV + AVD + ISRT achieved a complete response. With a median follow-up of 18.8 months, by intent to treat, the 1-year progression-free survival is 93.3% (95% confidence interval, 84-102). Overall, the treatment was well-tolerated with no evidence of significant pulmonary toxicity. The majority of patients (≥90%) achieved negative interim PET scans after 2 and 4 cycles of BV + AVD. Excluding the 2 primary refractory patients, all patients are disease free, suggesting that this is a highly active treatment program even in patients with substantial disease bulk. This trial was registered at www.clinicaltrials.gov as #NCT01868451.

In this issue of Blood, Noy et al report on the efficacy of single-agent ibrutinib in patients with relapsed or refractory marginal zone lymphoma (MZL). They demonstrate an overall response rate of 48% and a median progression-free survival of 14 months, establishing the Bruton tyrosine kinase (BTK) inhibitor ibrutinib as a therapeutic option for this population.1

Introduction: The most effective initial therapy for older adults with CLL has not yet been established due to the lack of comparison of chemoimmunotherapy (CIT) and targeted therapy with the Bruton's Tyrosine Kinase (BTK) inhibitor ibrutinib. CIT has been the gold standard since studies showing that addition of CD20 antibody to chemotherapy prolongs survival. Bendamustine plus rituximab (BR) is one standard, more aggressive CIT regimen for patients (pts) age 65 or older. While ibrutinib has been FDA approved for untreated CLL since 2016, it has only been compared to chlorambucil, which is relatively ineffective, and never before to aggressive CIT. Additionally, the benefit of the addition of rituximab to ibrutinib in this setting has not been prospectively studied in a phase 3 trial. As part of a randomized phase 3 trial, the Alliance sought to answer these important clinical questions. Pts and Methods: Alliance A041202 is a multicenter NCI National Clinical Trials Network phase 3 study comparing BR (Arm 1) with ibrutinib (Arm 2) and the combination of ibrutinib plus rituximab (Arm 3) to determine whether ibrutinib-containing regimens are superior to CIT in terms of PFS. Additionally, this study sought to determine if adding rituximab to ibrutinib would prolong PFS over ibrutinib alone. At time of progression, pts on Arm 1 could cross over to Arm 2. Eligible pts were those age ≥ 65 years with previously untreated, symptomatic CLL. Pts had a CrCl ≥ 40 mL/min, bilirubin ≤ 1.5 x ULN, and no significant life-limiting intercurrent illness or need for warfarin treatment. Pts were stratified based upon Rai stage, Zap-70 methylation performed centrally, and del(17)(p13.1) or del(11)(q22.3) by local interphase cytogenetics and were randomized 1:1:1 to each arm. With 166 pts per arm, the trial was powered to detect an improvement in 2-year PFS from 61% in Arm 1 to 75% in Arms 2 or 3 (HR=0.586) using two one-sided log-rank tests with type I error rate of 2.5% and 90% power. The Alliance Data and Safety Monitoring Board approved the data release after meeting the protocol-defined efficacy threshold at a planned interim analysis with a one-sided critical value of 0.001538. These data were locked July 2, 2018; updated results will be presented at the meeting. Results: Between 12/9/2013 and 5/16/2016, 547 pts were registered and randomized (Arms 1: 183, 2: 182, and 3: 182). Median age was 71 years and 67% of pts were men. High-risk Rai stage (stage III/IV) was seen in 54%, unmethylated Zap-70 in 53%, and del(17p) or del(11q) by local FISH in 28%. Local vs centralized FISH was performed for del(11q) and del(17p) with agreement between local and central results in 94% (Kappa=0.80) and 97% (Kappa=0.76) of pts, respectively. 525 (96%) pts were eligible and included in the primary PFS analysis (Arms 1: 176, 2: 178, and 3: 171). With median follow-up of 32 months (mo), median PFS was 41 mo in Arm 1 and has not been reached in Arms 2 or 3 (HR comparing Arm 2 to 1 is 0.40 with one-sided p Conclusions: This international phase 3 trial demonstrates that ibrutinib produces superior PFS to standard CIT in older pts with CLL and justifies it as a standard of care treatment for pts age 65 and older. The addition of rituximab does not prolong PFS with ibrutinib. While ibrutinib represents a major therapeutic advance, toxicities and also cost justify future efforts to reduce the need for long-term continuous treatment. Support: K23CA178183, R01CA183444, U10CA180821, U10CA180882, U24CA196171, Clinicaltrials.gov identifier: NCT01886872 Figure. Figure. Disclosures Ding: Merck: Research Funding. Bartlett:Astra Zeneca: Research Funding; ImaginAB: Research Funding; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Bristol-Meyers Squibb: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Research Funding; Pharmacyclics: Research Funding; Affimed: Research Funding; Janssen: Research Funding; Novartis: Research Funding; Merck & Co: Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Immune Design: Research Funding; Forty Seven: Research Funding; Novartis: Research Funding; Millennium: Research Funding. Brander:BeiGene: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; TG Therapeutics: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Genentech: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Novartis: Consultancy, Other: DSMB; AbbVie: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Pharmacyclics, an AbbVie Company: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria; Acerta: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; DTRM: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding. Barr:AbbVie, Gilead: Consultancy. Parikh:Gilead: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; Janssen: Research Funding; AstraZeneca: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Coutre:Celgene: Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Pharmacyclics LLC, an AbbVie Company: Honoraria, Research Funding; Gilead: Research Funding; Beigene: Consultancy; AbbVie: Consultancy, Research Funding. Lozanski:Novartis: Research Funding; BI: Research Funding; Genentech: Research Funding; Stem Line: Research Funding; Coulter: Research Funding; Beckman: Research Funding. Larson:Ariad/Takeda: Consultancy, Research Funding; BristolMyers Squibb: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Erba:Amgen: Research Funding; Juno: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; MacroGenics: Consultancy; Juno: Research Funding; Janssen: Research Funding; Seattle Genetics: Consultancy, Research Funding; Janssen: Research Funding; Juno: Research Funding; Agios: Consultancy, Speakers Bureau; MacroGenics: Consultancy; Incyte: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Research Funding; Takeda/Millenium: Research Funding; Novartis: Consultancy, Speakers Bureau; Takeda/Millenium: Research Funding; Incyte: Consultancy, Speakers Bureau; MacroGenics: Consultancy; Celgene: Consultancy, Speakers Bureau; Janssen: Research Funding; Novartis: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Astellas: Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; MacroGenics: Consultancy; Daiichi Sankyo: Consultancy, Research Funding; Pfizer: Consultancy, Other: grant; Astellas: Research Funding; Juno: Research Funding; Janssen: Research Funding; Novartis: Consultancy, Speakers Bureau; Amgen: Research Funding; Agios: Consultancy, Speakers Bureau; Astellas: Research Funding; Agios: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Amgen: Research Funding; Pfizer: Consultancy, Other: grant; Pfizer: Consultancy, Other: grant; Astellas: Research Funding; Amgen: Research Funding; Agios: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Pfizer: Consultancy, Other: grant; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Research Funding; Celgene: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Takeda/Millenium: Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Celgene: Consultancy, Speakers Bureau; Takeda/Millenium: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee. Owen:Janssen: Honoraria, Research Funding; Celgene: Research Funding; AstraZeneca: Honoraria, Research Funding; Pharmacyclics: Research Funding; F. Hoffmann-La Roche Ltd: Honoraria, Research Funding; AbbVie: Research Funding; Merck: Honoraria; Teva: Honoraria. Abramson:Bayer: Consultancy; Novartis: Consultancy; Merck: Consultancy; Karyopharm: Consultancy; Seattle Genetics: Consultancy; Verastem: Consultancy; Humanigen: Consultancy; Juno Therapeutics: Consultancy; Gilead: Consultancy; Celgene: Consultancy; Amgen: Consultancy.

Introduction: Venetoclax (Ven), an oral BCL2 inhibitor, is approved for the treatment (tx) of relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL). Ven is generally well tolerated, and side effects observed in clinical trials have been consistent with other CLL tx. Clinical trials using the approved dose escalation schedule report negligible rates of clinical tumor lysis syndrome (TLS). We aimed to understand rates of select adverse events (AEs) including cytopenias, infections, and TLS in CLL patients (pts) treated with Ven in community and academic settings. To do so, we examined 297 pts with CLL who received Ven, either alone or paired, in this multicenter, international study. Methods: We conducted a retrospective cohort study of Ven treated pts with CLL across at 15 academic (n=169) and 51 community (n=128) centers outside of the clinical trial setting. This study represents a collaboration between US centers, CLL Collaborative Study of Real World Evidence (CORE), and UK CLL Forum. Demographics, baseline disease characteristics, Ven dosing, TLS risk (per FDA Ven label) and prophylaxis, and AEs were collected. Lab vs. clinical TLS was defined by Howard criteria. PFS was estimated by Kaplan Meier methodology. All comparisons were descriptive. Results: Of the 297 pts examined, median age at Ven initiation was 67 (range 37-91). The group was 69% male, 96% had R/R CLL, and 45% had del17p. Baseline characteristics stratified by practice setting are included in Table 1. 80% received Ven as monotherapy while 20% received it paired with another agent (anti-CD20 mAb (75%), ibrutinib (8.5%), other (16.5%)). All pts were treated outside of clinical trials. During dose escalation, 81% achieved a 400 mg dose and 65% maintained 400 mg following escalation (cyp3A4 use unknown). TLS risk was low in 40%, intermediate (int) in 32%, and high risk in 28%. CT scan prior to Ven initiation was performed in 62%. At least one hospitalization occurred for 56% of low, 80% of int, and 88% of high risk pts (63% of the total cohort). Table 1 describes the distribution of TLS risk and frequency of hospitalizations in academic, community centers. TLS prophylactic measures were available for a subset of pts. Allopurinol was used for 91% (n=68/75) of low, 93% (n=52/56) of int, and 94% (n=29/31) of pts at high risk for TLS. Rasburicase was used for 27% (n=28/102) of low, 42% (n=34/81) of int, and 72% (n=57/79) of high risk pts. Normal saline was used in 85% (n=62/73) of low, 88% (n=49/56) of int, and 97% (n=30/31) of high risk pts. TLS occurred in 8.4% of pts (n=25/297). Three lab and 2 clinical events occurred in low risk pts, 7 lab and 3 clinical events in int risk pts, and 7 lab and 3 clinical events in high risk pts. Of pts with TLS, 1 has discontinued Ven. Of pts with clinical TLS, all were hospitalized, received allopurinol and normal saline, and 28% received rasburicase. 72% with TLS had creatinine clearance Select AEs were neutropenia (ANC7 stools/day) 6.9%. For the subset who received Ven paired, AEs were not increased: 35% neutropenia, 29% thrombocytopenia, 22% infection, 6.3% neutropenic fever, and 6.4% diarrhea. TLS was observed in 3.4% of pts who received Ven paired vs. 9.3% who received Ven monotherapy. 29% pts required ≥1 dose reduction and 32% had ≥1 dose interruption. Median length of dose interruption was 7 days (range 1 - 132). 22 pts (7.4%) discontinued Ven due to an AE. PFS was similar in pts with ≥1 dose interruption vs. 0, pts who required dose interruption ≥8 days vs. Conclusions: Ven was well tolerated in this cohort; AE rates were similar to those reported in clinical trials. Both academic and community sites employed TLS prophylaxis consistent with FDA/EMA recommendations resulting in a small proportion of clinical TLS events ( Disclosures Fox: Sunesis: Consultancy; Celgene: Consultancy, Other: Travel support, Speakers Bureau; Roche: Consultancy, Other: Travel support, Research Funding, Speakers Bureau; Gilead: Consultancy, Other: Travel support, Research Funding, Speakers Bureau; AbbVie: Consultancy, Other: Travel support, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Personal fees and non-financial support, Speakers Bureau. Eyre:Gilead: Consultancy, Other: travel support; Abbvie: Consultancy, Other: travel support; Roche: Consultancy; Janssen: Consultancy, Other: travel support; Celgene: Other: travel support. Allan:Verastem: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy; Genentech: Membership on an entity's Board of Directors or advisory committees; Sunesis: Membership on an entity's Board of Directors or advisory committees. Schuster:OncLive: Honoraria; Physician's Education Source, LLC: Honoraria; Dava Oncology: Consultancy, Honoraria; Genentech: Honoraria, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Nordic Nanovector: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Nabhan:Cardinal Health: Employment, Equity Ownership. Hill:Amgen: Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Shah:Lentigen Technology: Research Funding; Miltenyi: Other: Travel funding, Research Funding; Juno Pharmaceuticals: Honoraria; Exelexis: Equity Ownership; Oncosec: Equity Ownership; Geron: Equity Ownership. Lamanna:Jannsen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Verastem: Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Cheson:AbbVie, Roche/Genentech, Pharmacyclics, Acerta, TG Therapeutics: Consultancy. Coombs:AROG: Other: Travel fees; H3 Biomedicine: Honoraria; Abbvie: Consultancy; DAVA Oncology: Honoraria; Incyte: Other: Travel fees. Barr:AbbVie, Gilead: Consultancy. Skarbnik:Gilead Sciences: Honoraria, Speakers Bureau; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Honoraria, Speakers Bureau; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Jazz Pharmaceuticals: Honoraria, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Shadman:Pharmacyclics: Research Funding; Acerta Pharma: Research Funding; AstraZeneca: Consultancy; Genentech: Consultancy; Celgene: Research Funding; Verastem: Consultancy; Gilead Sciences: Research Funding; TG Therapeutics: Research Funding; AbbVie: Consultancy; Genentech: Research Funding; Mustang Biopharma: Research Funding; Beigene: Research Funding; Qilu Puget Sound Biotherapeutics: Consultancy. Ujjani:AbbVie: Consultancy, Speakers Bureau. Pagel:Pharmacyclics, an AbbVie Company: Consultancy; Gilead: Consultancy. Jacobs:Genentech: Honoraria. Schuh:Giles, Roche, Janssen, AbbVie: Honoraria. Brander:Genentech: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Novartis: Consultancy, Other: DSMB; BeiGene: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; DTRM: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; TG Therapeutics: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Acerta: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; AbbVie: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Pharmacyclics, an AbbVie Company: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria. Mato:Pharmacyclics: Consultancy, Honoraria, Research Funding; TG Therapeutics: Research Funding; Regeneron: Research Funding; Sunesis: Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Acerta: Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy; Celgene: Consultancy; Prime Oncology: Speakers Bureau.

Introduction: About 20% of patients (pts) with primary mediastinal B-cell lymphoma (PMBL) are not cured after first-line treatment; those with chemosensitive relapse may benefit from autologous hematopoietic cell transplantation (auto-HCT). However, outcomes remain poor for pts with chemorefractory disease and those who have relapsed after auto-HCT. In PMBL, there is increased expression of the programmed death-1 (PD-1) ligands and expression of CD30 on tumor cells. Evasion of host immune responses by tumor cells may lead to resistance to standard chemotherapy. Nivolumab is a fully human IgG4 monoclonal antibody that binds to immune checkpoint PD-1, abrogates tumor inhibitory signals, and augments host antitumor immune response. Brentuximab vedotin (BV) is an antibody-drug conjugate that binds to CD30-expressing cells and induces apoptosis and immunogenic cell death. Combination of nivolumab and BV may therefore have synergistic antitumor activity against relapsed/refractory PMBL (rrPMBL). This study evaluated the safety and efficacy of nivolumab + BV in this pt population. Methods: This expansion cohort of a phase 1/2 open-label, single-arm, international study (NCT02581631) enrolled pts with PMBL aged ≥15 years, an Eastern Cooperative Oncology Group (ECOG) performance status ≤1, confirmed CD30 expression in ≥1% of tumor cells, measurable disease per Lugano 2014 classification, and relapsed/refractory disease after either high-dose conditioning chemotherapy and auto-HCT, or ≥2 prior multi-agent chemotherapies if auto-HCT ineligible. Nivolumab (240 mg IV flat dose) and BV (1.8 mg/kg IV, prespecified dose modifications allowed) were received every 3 weeks until disease progression or unacceptable toxicity. Pts were evaluated for safety (primary objective) continuously during treatment and at scheduled intervals during follow-up. Descriptive statistics were used to present pt characteristics and adverse events (AEs). The primary efficacy endpoint was investigator-assessed objective response rate (ORR) according to Lugano 2014 classification. Results: At database lock, 30 pts were treated with nivolumab + BV and included in this interim analysis. At enrollment, median (range) age was 35.5 (19-83) years. Thirteen pts (43%) had stage III or IV disease at initial diagnosis. Pts had received a median of 2 prior systemic therapies before enrollment, and 4 (13%) received auto-HCT (Table). Treatment-related AEs (TRAEs) were reported in 25 pts (83%). The most frequently reported TRAEs were neutropenia (27%), peripheral neuropathy (20%), and hyperthyroidism (13%). Grade 3-4 TRAEs were reported in 10 pts (33%), including 8 pts (27%) with neutropenia, 2 pts (7%) each with thrombocytopenia or decreased neutrophil count, and 1 pt (3%) each with hypersensitivity, diarrhea, or maculopapular rash. Three pts (10%) had treatment-related serious AEs, including 1 pt with grade 3-4 diarrhea and maculopapular rash, and 1 pt with grade 5 acute kidney injury. At the time of the meeting, ORR and complete remission rate will be presented based on a planned interim analysis. Conclusions: These results demonstrate that in pts with CD30-expressing rrPMBL, the combination of nivolumab and BV has a manageable safety profile and may provide a potential treatment option for this patient population. Study support: BMS. Writing support: Janice Zhou, Caudex, funded by BMS. Table. Table. Disclosures Moskowitz: Bristol Myers-Squibb: Consultancy, Research Funding; Merck: Research Funding; Incyte: Research Funding; Takeda: Honoraria; ADC Therapeutics: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding. Cunningham:Roche pharmaceuticals: Research Funding. Barr:AbbVie, Gilead: Consultancy. Kline:iTeos: Research Funding; Merck: Honoraria, Research Funding. Kuruvilla:Gilead: Consultancy, Honoraria; Lundbeck: Honoraria; Celgene: Honoraria; BMS: Consultancy, Honoraria; Abbvie: Consultancy; Roche: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Merck: Consultancy, Honoraria; Karyopharm: Honoraria; Princess Margaret Cancer Foundation: Research Funding; Amgen: Honoraria; Leukemia and Lymphoma Society Canada: Research Funding; Seattle Genetics: Consultancy, Honoraria. Johnson:Lundbeck: Consultancy, Honoraria, Other: travel, Research Funding; Seattle Genetics: Honoraria; Merck: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; AbbVie Inc.: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Other: travel, Research Funding. Mehta-Shah:Spectrum: Consultancy; Bristol-Myers Squibb: Research Funding; Verastem: Research Funding; Genetech: Research Funding; Celgene: Research Funding. Manley:Seattle Genetics: Employment, Equity Ownership. Sharma:Bristol-Myers Squibb: Employment. Francis:Bristol-Myers Squibb: Employment, Other: company stock options. Cohen:Bristol-Myers Squibb: Employment, Other: company stock ownership. Zinzani:BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; PFIZER: Honoraria, Membership on an entity's Board of Directors or advisory committees; PFIZER: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celltrion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Speakers Bureau; TG Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; TG Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; SERVIER: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Honoraria, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees.