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Background: Mcl-1 is an anti-apoptotic protein in the Bcl-2 family that contributes to the pathophysiology of certain B-cell malignancies and AML. Dependence on Mcl-1 is associated with poor prognosis, and increased Mcl-1 levels is a common mechanism of resistance to venetoclax. Voruciclib (VORU), a potent oral CDK9 inhibitor (Ki Methods: Pts with relapsed B-cell lymphoma, chronic lymphocytic leukemia (CLL), or AML were eligible if age ≥18 years, ECOG performance status ≤1, disease progression after failure of standard therapies, adequate hepatic and renal function, and no prior CDK9 therapy. Dose escalation started at 50 mg, followed a 3+3 design, and DLTs were assessed in Cycle 1. Initially VORU was administered once daily continuously in a 28-day cycle (Group I). After 2 DLTs were observed at 100 mg, administration was changed to once daily on days 1 to 14 in a 28-day cycle (Group II), patients with prior allogeneic transplant were excluded, and dose escalation (100, 150, 200 mg) proceeded in separate cohorts for AML and B-cell malignancies. Disease response was assessed by the Lugano, iwCLL, and 2017 ELN criteria. Results: To date 28 pts have been enrolled: 14 AML, 7 diffuse large B-cell lymphoma (DLBCL), 3 follicular lymphoma (FL), 2 CLL and 2 mantle cell lymphoma. Group I enrolled 16 pts, 8 each at 50 mg and 100 mg. Group II enrolled 12 pts, 10 with AML administered VORU at 100, 150 or 200 mg and 2 pts with B-cell malignancies administered VORU at 100 mg. Dose escalation in AML is completed. Median age was 71 years (range 40-90) and 54% of pts were male. Pts were generally heavily pretreated, with a median of 3 prior therapies (range 1-8). Median number of VORU cycles administered was 2 (range 1-4). Drug-related serious adverse events (SAEs) were reported in Group I only and consisted of 2 DLT of Gr 3 pneumonitis at 100 mg, both in AML pts treated with allogeneic transplant followed by GVHD in the preceding 12 months, one of whom also had a concurrent Gr 3 differentiation syndrome (DS), and 1 SAE not meeting DLT criteria, a Gr 3 hypoxemic respiratory failure in Cycle 4 in a pt with DLBCL at 50 mg. One AML pt developed ischemic bowel thought to be due to disease progression. Symptoms consistent with DS were observed in 4 AML pts. In Group II, no DLTs have been observed to date and there were no Gr 3-5 drug-related adverse events reported. There is no evidence of significant drug-related neutropenia in pts with B-cell malignancies. To date, in Groups I and II combined, 1 AML pt achieved a morphologic leukemia-free state, 2 AML pts achieved stable disease (SD), and 3 pts with B-cell malignancies had a best response of SD, including 1 FL pt who achieved a 42% reduction in SPD, and 1 CLL pt with relapsed disease after chemoimmunotherapy, venetoclax, and ibrutinib who had stable blood counts. Conclusions: VORU at doses up to 200 mg administered on 14 consecutive days in a 28-day cycle was well tolerated with no DLTs observed. Consistent with the phase 1 studies in solid tumors, no significant myelosuppression was seen in pts with B-cell malignancies. The safety profile does not indicate overlapping toxicities with venetoclax. Disease stabilization was observed in heavily pretreated pts and differentiation syndrome was observed in AML indicating biologic activity. Enrollment at 200 mg will continue in an expansion cohort in AML. A forthcoming protocol amendment will evaluate VORU in combination with venetoclax in pts with relapsed AML to exploit the dual inhibition of Bcl-2 and Mcl-1. Disclosures Konopleva: Sanofi: Other: grant support, Research Funding; Ablynx: Other: grant support, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support; KisoJi: Research Funding; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; Stemline Therapeutics: Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; AstraZeneca: Other: grant support, Research Funding; Rafael Pharmaceuticals: Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; Ascentage: Other: grant support, Research Funding; Calithera: Other: grant support, Research Funding; Cellectis: Other: grant support; Forty Seven: Other: grant support, Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding. Brander: Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; BeiGene: Research Funding; DTRM: Research Funding; Genentech: Consultancy, Research Funding; Juno Therapeutics/Celgene/Bristol Myers Squibb: Research Funding; Pfizer: Consultancy, Other: Biosimilars outcomes research panel; TG Therapeutics: Consultancy, Research Funding; Ascentage: Research Funding; LOXO: Research Funding; AstraZeneca: Research Funding; MEI Pharma: Research Funding; ArQule: Research Funding; AbbVie: Consultancy, Other: informCLL registry steering committee, Research Funding; Verastem: Consultancy; Novartis: Research Funding; NCCN: Other: panel member; ArQule/Merck: Consultancy. Patel: TG Therapeutics: Consultancy, Speakers Bureau; Curis, Inc: Research Funding; Xencor: Research Funding; Kite: Consultancy, Research Funding, Speakers Bureau; Genentech/Roche: Consultancy, Research Funding, Speakers Bureau; Juno Pharmaceuticals: Consultancy; Fate Therapeutics: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding, Speakers Bureau; MEI Pharma: Consultancy, Research Funding; Trillium Therapeutics: Research Funding; BeiGene: Consultancy; Celgene: Consultancy, Research Funding, Speakers Bureau; Morphosys: Consultancy; Abbvie: Consultancy; Aptevo Therapeutics: Research Funding; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; Sunesis Pharmaceuticals: Research Funding; Pharmacyclics/Janssen: Consultancy, Research Funding, Speakers Bureau; Velos Bio: Research Funding; Millenium/Takeda: Research Funding. Diefenbach: Celgene: Research Funding; Trillium: Research Funding; IMab: Research Funding; Merck Sharp & Dohme: Consultancy, Honoraria, Research Funding; Morphosys: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Incyte: Research Funding; Gilead: Current equity holder in publicly-traded company; AbbVie: Research Funding; Perlmutter Cancer Center at NYU Langone Health: Current Employment; IGM Biosciences: Research Funding; MEI: Consultancy, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding; Genentech, Inc./ F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding. Alvarado: BerGenBio: Research Funding; MEI Pharma: Research Funding; CytomX Therapeutics: Consultancy; Astex Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Research Funding; Daiichi-Sankyo: Research Funding; FibroGen: Research Funding; Sun Pharma: Consultancy, Research Funding. Al Malki: Rigel Pharma: Consultancy; Neximmune: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy; Hansa Biopharma: Consultancy; CareDx: Consultancy. Danilov: Bayer Oncology: Consultancy, Honoraria, Research Funding; Genentech: Consultancy, Honoraria, Research Funding; Takeda Oncology: Research Funding; TG Therapeutics: Consultancy, Research Funding; Abbvie: Consultancy, Honoraria; SecuraBio: Research Funding; Astra Zeneca: Consultancy, Honoraria, Research Funding; Rigel Pharm: Honoraria; Bristol-Meyers-Squibb: Honoraria, Research Funding; Gilead Sciences: Research Funding; Pharmacyclics: Consultancy, Honoraria; Beigene: Consultancy, Honoraria. Abedin: Pfizer: Research Funding; Amgen: Honoraria; Helsinn: Research Funding; Astellas Pharma Inc.: Research Funding; Agios: Honoraria; Actinium: Research Funding; AltruBio: Research Funding. Ghalie: MEI Pharma: Current Employment, Current equity holder in publicly-traded company. Davids: Genentech: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Astra-Zeneca: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; MEI Pharma: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Ascentage Pharma: Consultancy, Research Funding; TG Therapeutics: Consultancy, Research Funding; Verastem: Consultancy, Research Funding; Surface Oncology: Research Funding; AbbVie: Consultancy; Adaptive Biotechnologies: Consultancy; BeiGene: Consultancy; Celgene: Consultancy; Eli Lilly and Company: Consultancy; Janssen: Consultancy; MEI Pharma: Consultancy; Merck: Consultancy; Research to Practice: Consultancy; Takeda: Consultancy. OffLabel Disclosure: Vorucicilb is an investigational CDK inhibitor being evaluated in patients with hematologic malignancies, specifically relapsed AML and B-cell malignancies. The abstract submitted to ASH 2021 reports the results of the completed dose escalation portion of a phase 1 study.

Introduction : Chronic Lymphocytic Leukemia (CLL) is characterized by the clonal expansion of mature CD19+/CD5+ lymphocytes in the peripheral blood and secondary lymphoid organs. The accumulation of B-CLL cells yields profound immune defects in the CLL tumor microenvironment (TME), promoting evasion of immune surveillance that contributes to tumor persistence and thus relapsed/refractory disease. The bromodomain and extra-terminal domain (BET) family of proteins are epigenetic readers that bind acetylated histone residues to regulate transcription of numerous genes involved in critical CLL protumor pathways. Of the BET family proteins, BRD4 is overexpressed in CLL and highly enriched at super-enhancers of genes that regulate CLL-TME interactions such as B cell receptor pathway components, chemokine/cytokine receptors, and immune checkpoint molecules. Pan BET inhibitors (BET-i), such as PLX51107 (Plexxikon Inc.) significantly improve survival in aggressive CLL murine models. Here we demonstrate that blocking BRD4 function with PLX51107 (PLX5) can alleviate the inherent immune defects observed in CLL, hence reducing B-CLL induced T cell dysfunction and allowing for robust B-CLL cell elimination. This therapeutic strategy may be vital in overcoming frequent drug resistance and/or bolstering the anti-tumor effect of current CLL therapies. Methods : Primary leukemic B cells were isolated from the peripheral blood of CLL patients and co-cultured with healthy donor T cells to evaluate the effect of PLX5 (0.1-0.5μM) on CLL-induced T cell immunosuppression ex vivo via an array of flow cytometry assays. T cell proliferation was assessed using CFSE after 96 h co-culture with α-CD3/α-CD28 stimulation. Effector cytokine production was evaluated after 48 h co-culture in the presence of PMA/ionomycin (final 6 h) and brefeldin A (final 5 h). Immune inhibitory molecule surface expression was measured following 48 h co-culture with α-CD3/α-CD28 stimulation. To further validate our ex vivo findings, the E μ-TCL1 adoptive transfer model was used. Once disease onset was confirmed in recipient WT B6 mice (>10% CD45+/CD19+/CD5+ peripheral blood lymphocytes), mice were randomized to receive either PLX5 (20 mg/kg) or vehicle (VEH) equivalent daily by oral gavage for 4 weeks. Following treatment, mouse spleens were processed to evaluate exhaustion marker expression, T cell proliferation (CellTrace™ Violet, 72 h a-CD3/α-CD28 stimulation ex-vivo), and T-cell effector function (ex-vivo mitogenic stimulation, 6 h). Results : T cell proliferation indices were reduced following ex vivo co-culture with primary B-CLL cells (mean ± SEM for T cells vs. co-culture, 2.0 ± 0.13 vs. 1.57 ± 0.05; P Conclusion : Epigenetic-targeted therapies such as BET-i have the potential to alleviate CLL-induced T cell dysfunction while eliminating B-CLL cells and preventing tumor expansion. Future profiling studies are pending to further illuminate how BET proteins regulate immune function in CLL. Figure 1 Figure 1. Disclosures Lunning: AstraZeneca: Consultancy; Legend: Consultancy; Acrotech: Consultancy; ADC Therapeutics: Consultancy; Kyowa Kirin: Consultancy; Myeloid Therapeutics: Consultancy; Beigene: Consultancy; Celgene, a Bristol Myers Squibb Co.: Consultancy; Verastem: Consultancy; Janssen: Consultancy; Daiichi-Sankyo: Consultancy; Morphosys: Consultancy; TG Therapeutics: Consultancy; Novartis: Consultancy; Karyopharm: Consultancy; AbbVie: Consultancy; Spectrum: Consultancy; Kite, a Gilead Company: Consultancy. Vose: Kite, a Gilead Company: Honoraria, Research Funding. Powell: Plexxikon Inc.: Current Employment.

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.

Background: Acute Lymphoblastic Leukemia (ALL) outcomes have significantly improved over time with multi-agent chemotherapy, and the addition of asparaginase (ASP) has demonstrated the ability to prolong overall survival. ASP has multiple toxicities, and it remains a challenge to manage them safely, particularly coagulopathy and thrombosis (30-40% based on historical studies). The best prophylactic anticoagulation strategy in patients with acute leukemias, particularly ALL with asparaginase use, remains unclear due to severe coexisting thrombocytopenia and coagulopathy. Though the current guidelines recommend using Antithrombin (AT) replacement or low molecular weight heparin (LMWH) for thrombosis prophylaxis, the evidence is weak with concerns of thrombosis (Blood (2020) 136 (3): 328-338) with the use of fibrinogen concentrates(cryoprecipitate) and limited efficacy data with AT replacement and unfractionated heparin (UFH) for thrombosis prophylaxis. Due to potential "resistance" to LMWH and UFH from acquired AT deficiency with ASP use, our institution in 2017 has adopted the use of the direct Xa inhibitor, Apixaban for thrombosis prophyalxis. We report the safety and effectiveness of Apixaban for thrombosis prophylaxis with ASP. Methods: In this retrospective study, we reviewed the data on 20 patients treated with ASP between 2017-2020. Thrombosis prophylaxis was instituted with Apixaban 2.5 mg PO Q 12 hourly for three weeks along with cryoprecipitate as needed for bleeding or fibrinogen levels Results: Among the 20 patients treated during this period, 18 (90%) had ALL, and 2(10%) had NK/T cell lymphoma. Of the patients with ALL, 67% had high risk and 33% with standard-risk ALL. The median age of this cohort was 29.5 years (range: 19-63 years), 80% were males, 70% white, 30% were Latino or Hispanic, median body mass index-BMI of 30.2 kg/m 2(19.4-40.7 kg/m 2) and 65% were non-smokers. The median baseline AT activity was 107% (79-221%), 95% used concurrent corticosteroids (65%- Prednisone, and 30% used Dexamethasone). The most common induction treatment was CALGB 10403 (55%). Of the total, 95% received pegylated ASP, and only one patient received Erwinia ASP due to prior history of anaphylaxis. The major toxicities attributed to ASP included 5% grade II and 15% grade III-IV aspartate aminotransferase (AST) or alanine aminotransferase (ALT) elevation, 20% had bilirubin elevation, 10% developed grade III-IV acute pancreatitis, and 5% developed severe hypertriglyceridemia needing aphaeresis. Two patients (10%) developed thrombosis [catheter associated deep venous thrombosis (DVT) and one patient with lower extremity proximal DVT] within 4 weeks of use of ASP, with one of the two patients (5%) developing (lower extremity proximal DVT) while on being off anticoagulation due to bleeding. Major bleeding or CRNMB developed in 5% (spontaneous splenic rupture from ALL leading to hemorrhagic shock). The median number of cryoprecipitate units used per patient during weeks 1,2,3, and 4 was 5(0-35), 5(0-40), 5(0-15), 7.5(0-15), respectively; No patients received fresh frozen plasma or AT concentrates. Conclusions: With the use of Apixaban prophylaxis, the incidence of thrombosis was 10% within four weeks from ASP and 5% while on anticoagulation. The incidence of major bleeding or CRNMB was 5%. Hypofibrinogenemia, acquired AT deficiency due to ASP, was seen between days 7-21 after using ASP (figure 1 & 2) and recovered subsequently. This study demonstrates initial evidence of the safety and efficacy of Apixaban for thrombosis prophylaxis and cryoprecipitate infusions in patients treated with ASP. Figure 1 Figure 1. Disclosures Gundabolu: Samus Therapeutics: Research Funding; Pfizer: Research Funding; BioMarin Pharmaceuticals: Consultancy; Bristol-Myers Squibb Company: Consultancy; Blueprint Medicines: Consultancy. Bhatt: Jazz: Research Funding; Incyte: Consultancy, Research Funding; Pfizer: Research Funding; Tolero Pharmaceuticals, Inc: Research Funding; National Marrow Donor Program: Research Funding; Abbvie: Consultancy, Research Funding; Genentech: Consultancy; Abbvie: Consultancy, Research Funding; Partnership for health analytic research, LLC: Consultancy; Servier Pharmaceuticals LLC: Consultancy; Rigel: Consultancy. Vose: Kite, a Gilead Company: Honoraria, Research Funding. Lunning: Myeloid Therapeutics: Consultancy; Janssen: Consultancy; Kyowa Kirin: Consultancy; AstraZeneca: Consultancy; ADC Therapeutics: Consultancy; Novartis: Consultancy; Celgene, a Bristol Myers Squibb Co.: Consultancy; AbbVie: Consultancy; TG Therapeutics: Consultancy; Daiichi-Sankyo: Consultancy; Legend: Consultancy; Kite, a Gilead Company: Consultancy; Verastem: Consultancy; Acrotech: Consultancy; Karyopharm: Consultancy; Spectrum: Consultancy; Beigene: Consultancy; Morphosys: Consultancy. Baljevic: BMS/Celgene: Consultancy; Oncopeptides: Other: Advisory Board; Janssen Research: Other: Advisory Board; Karyopharm: Other: Advisory Board; BMS/Celgene: Other: Advisory Board; Amgen: Research Funding; Exelixis: Research Funding. Ganti: Merck: Research Funding; Apexigen: Research Funding; Nektar: Research Funding; Top Alliance Biosceinces: Research Funding; Lovance: Research Funding; Novartis: Research Funding; WindMil Therapeitucs: Research Funding; Takeda: Research Funding; Flagship Biosciences: Consultancy; AstraZeneca: Consultancy, Other: Advisory Board; Mirati Therapeutics: Consultancy, Other: Advisory Board; G1 Therapeutics: Consultancy, Other: Advisory Board; Blueprint Medicines: Consultancy, Other: Advisory Board; Cardinal Health: Consultancy, Other: Advisory Board; Roche: Consultancy, Other: Advisory Board; YMabS Therapeutics: Other: DSMC Chair.

Introduction Relapses involving the central nervous system (CNSrel) occur in ~5% of patients (pts) with aggressive non-Hodgkin lymphoma (NHL) in the rituximab era (Ghose et al, Clin LML 2015) with rates exceeding 10% in high risk groups (Villa et al, Ann Onc 2010; Schmitz et al, JCO 2016). CNSrel are generally thought to occur in the first 4-6 months from diagnosis. Prophylaxis (PPx) administration, route, and frequency are not standardized, and the impact of PPx on CNSrel risk is incompletely understood. Methods We performed a multicenter retrospective analysis of pts with aggressive NHL (excluding Burkitt's) without known CNS involvement (inv) who received single-route CNS PPx with during front-line (FL) anthracycline-based therapy (tx) from 2013-2019 across 19 US academic institutions. Recipients of chemotherapy for prior CLL or indolent NHL were ineligible. Method, frequency, and outcomes of CNS PPx administration were evaluated, with significance assessed by various statistical methods via two-tailed P Results 1030 patients were identified who met eligibility criteria. Clinical features included median age 61 years (yrs; range 16-86), 40.9% female, ECOG PS 0-1 82.8%, elevated LDH 65.3%, >1 extranodal (EN) site 42.3%, stage 3/4 disease 79.2%. NHL histologies included diffuse large B cell (DLBCL; 75.2%), high grade B cell (16.3%), transformed follicular lymphoma (5.6%) and 3% other; among pts with DLBCL, 46.4% had germinal center (GCB) subtype and 40.5% had non-GCB. 26.2% (n=210) of evaluable pts had double-hit lymphoma (DHL). Among pts with known HIV status, 7.2% (n=65) were HIV-positive. 85.7% had EN inv; common sites included bone (35.4%), liver (13.7%), gastrointestinal (12.7%), lung (11.8%), and marrow (11.5%). FL regimens included RCHOP (45.9%), REPOCH (46.5% total; 79.1% with dose-adjustment), 7.6% other. PPx was given intravenously (IV) in 20% of pts vs 77% intrathecally (IT), over a median 2.9 vs 4.1 doses respectively; see Table 1 for factors associated with PPx route. PPx was generally well-tolerated, with 10.7% PPx-related toxicity reported; see Table 2. CNSrel after FL tx was 5.3% overall without significant difference by PPx route (7% IV vs 5% IT, p=0.178). This lack of difference between PPx routes was observed in all subgroup analyses performed, including by: age, stage, histology, number of EN sites, individual EN site inv, elevated LDH, CNS-IPI, DHL status, HIV status, FL regimen, number of PPx doses. There was no significant difference in anatomic site(s) of CNSrel by PPx route. CNSrel occurred bimodally: 24% by end of FL tx vs 76% delayed (average 2.3 yrs, range 0.4-5.2 yrs). Rates of CNSrel were significantly higher with CNS-IPI high vs moderate risk (8.3 vs 4.1%, p=0.03; Figure 1), elevated LDH (6.9 vs 2.6%, p=0.007) and multiple inv EN sites (7.5% for 2+ vs 4% for 0-1, p=0.01); each additional EN site further increased risk (p=0.03 for trend; Figure 2). Increased CNSrel was noted in pts with testis (13.7 vs 5%, p=0.004) and liver inv (11.1 vs 4.6%, p=0.002) vs those without inv at respective sites. No significant difference was noted at other EN sites, including renal/adrenal (4.8 vs 5.6%, p=0.71), marrow (8.9 vs 5.1%, p=0.09), or lung (8.6 vs 5.1%, p=0.12). All EN site-CNSrel correlations were unchanged when accounting for PPx route. With median follow-up of 2.3 yrs, median PFS and OS for the overall group have not been reached; 2-yr PFS and OS were 70 and 85% respectively. PFS and OS were each predicted by CNS-IPI (p Conclusion Use of single-route ppx demonstrated similar CNSrel vs established outcomes for this population in the rituximab era, with no difference by PPx route. CNSrel remains a rare but devastating complication, with greater risk even after single-route PPx in those with higher EN burden and inv of key EN sites. Disclosures Kahl: Acerta: Consultancy, Research Funding; Janssen: 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, Research Funding; BeiGene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche Laboratories Inc: Consultancy; Pharmacyclics LLC: Consultancy; Genentech: Consultancy; Celgene Corporation: Consultancy; AstraZeneca Pharmaceuticals LP: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy. Spinner:Notable Labs: Honoraria. Advani:Celgene, Forty Seven, Inc., Genentech/Roche, Janssen Pharmaceutical, Kura, Merck, Millenium, Pharmacyclics, Regeneron, Seattle Genetics: Research Funding; Astra Zeneca, Bayer Healthcare Pharmaceuticals, Cell Medica, Celgene, Genentech/Roche, Gilead, KitePharma, Kyowa, Portola Pharmaceuticals, Sanofi, Seattle Genetics, Takeda: Consultancy. Voorhees:AstraZeneca: Research Funding. Grover:Genentech: Research Funding; Tessa: Consultancy. Huntington:Genentech: Consultancy; Novartis: Consultancy; Celgene: Consultancy, Research Funding; TG Therapeutics: Research Funding; Pharmacyclics: Honoraria; Bayer: Consultancy, Honoraria; DTRM: Research Funding; Astrazeneca: Honoraria; AbbVie: Consultancy. Spurgeon:Beigene: Research Funding; Gilead: Research Funding; Genentech: Research Funding; Bristol-Myers Squibb: Research Funding; Pharmacyclics: Consultancy; Janssen: Consultancy, Research Funding; VelosBio: Consultancy, Research Funding; Cardinal Health: Honoraria; Verastem: Research Funding; Genmab: Research Funding; AstraZeneca: Research Funding; Acerta: Research Funding. Olszewski:Spectrum Pharmaceuticals: Research Funding; Genentech, Inc.: Research Funding; Adaptive Biotechnologies: Research Funding; TG Therapeutics: Research Funding. Landsburg:Seattle Genetics: Speakers Bureau; Morphosys: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Curis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Triphase: Research Funding. Kamdar:Roche: Research Funding. Caimi:Kite Pharma: Other: Advisory Board; ADC Therapeutics: Other: Advisory Board, Research Funding; Verastem: Other: Advisory Board; Amgen: Other: Advisory Board; Bayer: Other: Advisory Board; Celgene: Speakers Bureau. Karmali:Takeda: Research Funding; BeiGene: Speakers Bureau; AstraZeneca: Speakers Bureau; Karyopharm: Honoraria; Gilead/Kite: Honoraria, Other, Research Funding, Speakers Bureau; BMS/Celgene/Juno: Honoraria, Other, Research Funding, Speakers Bureau. Stephens:Pharmacyclics: Consultancy; Innate: Consultancy; Verastem: Research Funding; Karyopharm: Consultancy, Research Funding; Janssen: Consultancy; Gilead: Research Funding; Arqule: Research Funding; Juno: Research Funding; MingSight: Research Funding; Acerta: Research Funding; Beigene: Consultancy. Smith:Genentech/Roche: Consultancy, Other: Support of parent study and funding of editorial support, Research Funding; TG Therapeutics: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Janssen: Consultancy; BMS: Consultancy; Karyopharm: Consultancy, Research Funding; FortySeven: Research Funding; Pharmacyclics: Research Funding; Acerta: Research Funding. Khan:Celgene: Research Funding; Pharmacyclics: Honoraria; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Janssen: Honoraria. Cohen:Genentech, BMS, Novartis, LAM, BioInvent, LRF, ASH, Astra Zeneca, Seattle Genetics: Research Funding; Janssen, Adicet, Astra Zeneca, Genentech, Aptitude Health, Cellectar, Kite/Gilead, Loxo: Consultancy. Portell:Bayer: Consultancy; Xencor: Research Funding; BeiGene: Consultancy, Research Funding; Infinity: Research Funding; Roche/Genentech: Consultancy, Research Funding; Amgen: Consultancy; Janssen: Consultancy; Pharmacyclics: Consultancy; AbbVie: Research Funding; TG Therapeutics: Research Funding; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding.

Background Follicular lymphoma (FL) is the second most common type of non-Hodgkin lymphoma (NHL) and most common of the clinically indolent NHLs. Although often considered an incurable disease, overall survival has increased significantly with refinement in diagnostic techniques and the addition of rituximab. The course of FL is quite variable and presence of symptoms, organ dysfunction, cytopenias, aggressiveness of tumor are all taken into consideration when deciding individual treatment. In this study, we evaluated a large patient cohort with FL treated over a 35 year period for progression free survival (PFS), overall survival (OS) based on FLIPI score, tumor grade, and treatment regimen and also looked at causes of late failures. Methods We evaluated 1037 patients (pts) from the Nebraska Lymphoma Study Group that were diagnosed with FL between the years of 1983-2020. Descriptive statistics were stratified according to age, histological subtype, treatment regimen, FLIPI category, presence and type of secondary malignancy. PFS was calculated from the time of diagnosis to progression or death and OS was the time from diagnosis to death from any cause. PFS and OS were plotted as Kaplan-Meier curves with statistically significant p Results The median age at diagnosis and treatment was 61 years (yrs, range 17-91). A total of 9.1% were characterized as FLIPI high risk, 37.8% intermediate risk, and 33.6% low risk, 19.5% unavailable. Among the histological grade, 23.1% had FL- grade 1, 30.2% FL-2, 27.3% FL-3A, 2.5 % FL-3B and 16.9 % Composite Lymphoma. Anthracycline + rituximab was given in 24.5% of pts, whereas 43.8% of pts received an anthracycline based regimen without rituximab, 9.8% received rituximab without an anthracycline and 10.6% received neither of these agents. 6.75% (70 pts) were later found to have secondary malignancies of which 11 pts had myelodysplastic syndrome, 10 pts had acute leukemia and 9 pts had lung cancer. With a median follow up of 9.2 yrs and a maximum of 36 yrs, 29.7% (308 pts) had not relapsed. The median PFS across all groups was 4.6 yrs (Fig 1) and OS was 12.1 yrs. Median OS was significantly longer in patients that received rituximab at 16.1 yrs as compared to patients that did not receive rituximab at 9.89 yrs (Fig 2). PFS was 8.6 yrs, 3.6 yrs and 2.1 yrs and OS was 15.1 yrs, 11.7 yrs and 4.9 yrs in FLIPI low, intermediate and high risk groups respectively (p= When pts with FL-3A and FL-3B were grouped together and stratified according to treatment regimen, the group that received anthracycline and rituximab combination has highest PFS and OS at 13.3 yrs and 18.8 yrs (p Among the pts that relapsed/died after 10 years (n=190), the cause of death was relapsed lymphoma in 13.7%, unknown in 55.8%, secondary malignancies in 4.2%, treatment related in 2.6% and not related to disease in 23.7%. A total of 278 pts survived > 10 yrs, and of these pts, 119 (30%) had not relapsed at the last follow up. Conclusion The addition of rituximab to standard anthracycline based chemotherapy has resulted in significant improvements in the PFS and OS rates of FL. These results also support the prognostic value of the FLIPI in patients treated in the rituximab era. Late relapses after 10 yrs from disease can occur, but 11.5% of patients had not relapsed with long term follow up. Secondary malignancies are also an important consideration in the long term survivors. Disclosures Lunning: Acrotech: Consultancy; TG Therapeutics: Research Funding; Novartis: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Curis: Research Funding; Beigene: Consultancy, Honoraria; Aeratech: Consultancy, Honoraria; Bristol Meyers Squibb: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Legend: Consultancy; Verastem: Consultancy, Honoraria; ADC Therapeutics: Consultancy. Armitage:Trovagene/Cardiff Oncology: Membership on an entity's Board of Directors or advisory committees; Samus Therapeutics: Consultancy; Ascentage: Consultancy. Vose:Bristol-Myers Squibb: Research Funding; Karyopharm Therapeutics: Consultancy, Honoraria; Seattle Genetics: Research Funding; Allogene: Honoraria; AstraZeneca: Consultancy, Honoraria, Research Funding; Kite, a Gilead Company: Honoraria, Research Funding; Wugen: Honoraria; Novartis: Research Funding; Celgene: Honoraria; Incyte: Research Funding; Roche/Genetech: Consultancy, Honoraria, Other; Verastem: Consultancy, Honoraria; Miltenyi Biotec: Honoraria; Loxo: Consultancy, Honoraria, Research Funding; Janssen: Honoraria; Epizyme: Honoraria, Research Funding; AbbVie: Consultancy, Honoraria.

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.

Background: Dihydroorotate dehydrogenase (DHODH) is a mitochondrial enzyme involved in the de novo synthesis of pyrimidines, key building blocks for RNA and DNA biosynthesis. Inhibitors of DHODH are currently in clinical use for the treatment of rheumatoid arthritis (leflunomide) and multiple sclerosis (teriflunomide). Brequinar, a more specific and potent DHODH inhibitor, was evaluated in several phase 1 trials in patients with advanced solid tumors in the 1990s and demonstrated little evidence of antitumor activity; however, patients with hematologic malignancies were not evaluated in those studies. More recent preclinical studies show that cell lines and in vivo models derived from hematologic malignancies are highly sensitive to inhibition of DHODH. AG-636, a novel small molecule DHODH inhibitor, demonstrated strong in vitro and in vivo anti-tumor activity across diverse models of lymphoma and acute leukemia, supporting the evaluation of AG-636 as a treatment for patients with lymphoma and other hematologic malignancies. A phase 1, multicenter, open-label study investigating AG-636 for the treatment of patients with advanced lymphoma began enrollment on May 24, 2019 (NCT03834584). Methods: The primary objective of this study is to determine the maximum tolerated dose (MTD) of AG-636 and to characterize its dose-limiting toxicities (DLTs) when given to patients with advanced lymphoma. The study includes a dose escalation phase followed by an expansion phase. Approximately 54 adults (42 in the dose escalation phase and 12 in the expansion phase) with advanced lymphoma refractory to standard treatment, will be enrolled at up to 6 centers in the United States. Broad inclusion criteria enable patients with Hodgkin, Diffuse Large B-Cell (DLBCL), Follicular, Peripheral T-Cell, Cutaneous T-Cell, Mantle Cell, and less common subtypes of lymphoma as defined in 2017 by the World Health Organization to enroll. There are no limits on the number of prior lines of therapy and patients may have received prior stem cell transplant or chimeric antigen receptor T-cell therapy. Patients with active central nervous system disease are excluded. Patients must have an Eastern Cooperative Oncology Group performance status ≤2, an absolute neutrophil count ≥1.0×109/L, a platelet count ≥75×109/L, a serum total bilirubin level ≤1.5×upper limit of normal (ULN), alanine aminotransferase and aspartate aminotransferase levels ≤3.0×ULN, and a creatinine clearance ≥30 mL/min (Cockcroft-Gault formula). AG-636 is given as an oral capsule once daily for 2-5 days each week, with 1 cycle of therapy defined as 4 consecutive weeks of treatment. During the dose escalation phase of the study, successive cohorts of patients will be treated with increasing doses of AG-636 to estimate the MTD. The study employs a 2-parameter adaptive Bayesian logistic regression model using escalation with overdose control to guide dose escalation and to estimate the MTD. The MTD is the highest dose that is unlikely ( Disclosures Huntington: Celgene: Consultancy, Research Funding; Pharmacyclics: Honoraria; DTRM Biopharm: Research Funding; Genentech: Consultancy; Bayer: Consultancy, Honoraria; AbbVie: Consultancy. Basile:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Ulanet:Agios: Employment, Equity Ownership. Xu:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Yin:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Mobilia:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Cooper:Agios: Employment, Equity Ownership. Shah:AstraZeneca: Honoraria; Novartis: Honoraria; Spectrum/Astrotech: Honoraria; Celgene/Juno: Honoraria; Kite/Gilead: Honoraria; Incyte: Research Funding; Jazz Pharmaceuticals: Research Funding; Pharmacyclics: Honoraria; Adaptive Biotechnologies: Honoraria. Leonard:Merck: Consultancy; Miltenyi: Consultancy; Sandoz: Consultancy; ADC Therapeutics: Consultancy; Akcea Therapeutics: Consultancy; Karyopharm Therapeutics: Consultancy; Gilead: Consultancy; Akcea Therapeutics: Consultancy; Miltenyi: Consultancy; Sutro Biopharma: Consultancy; Celgene: Consultancy; Bayer Corporation: Consultancy; Bayer Corporation: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; Celgene: Consultancy; Epizyme, Inc: Consultancy; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy; MorphoSys: Consultancy; Karyopharm Therapeutics: Consultancy; Sutro Biopharma: Consultancy; BeiGene: Consultancy; Nordic Nanovector: Consultancy; ADC Therapeutics: Consultancy; MorphoSys: Consultancy; Sandoz: Consultancy; Gilead: Consultancy; BeiGene: Consultancy; Nordic Nanovector: Consultancy; Epizyme, Inc: Consultancy; AstraZeneca: Consultancy; Merck: Consultancy; AstraZeneca: Consultancy. von Keudell:Bayer: Consultancy; Genentech: Consultancy; Genentech: Consultancy; Pharmacyclics: Consultancy; Pharmacyclics: Consultancy; Bayer: Consultancy. Gopal:Seattle Genetics, Pfizer, Janssen, Gilead, Sanofi, Spectrum, Amgen, Aptevo, BRIM bio, Acerta, I-Mab-pharma, Takeda, Compliment, Asana Bio, and Incyte.: Consultancy; Teva, Bristol-Myers Squibb, Merck, Takeda, Seattle Genetics, Pfizer, Janssen, Takeda, and Effector: Research Funding; Seattle Genetics, Pfizer, Janssen, Gilead, Sanofi, Spectrum, Amgen, Aptevo, BRIM bio, Acerta, I-Mab-pharma, Takeda, Compliment, Asana Bio, and Incyte: Honoraria.

Background: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma, and is characterized as a heterogenous disease associated with varying outcomes. The International Prognostic Index (IPI) has been the standard for baseline prognostic assessment in these patients. In this study we aimed to determine the impact of treatment facility (academic versus non-academic centers) on overall survival outcomes in DLBCL patients stratified by IPI score risk groups, with a focus on high risk disease as this is associated with poorer outcomes. Methods: The 2018 National Cancer Database (NCDB) was utilized for patients diagnosed with DLBCL between 2004-2015. Patients were then stratified based on IPI risk score from low to high risk. Four risk groups were formed: low (0-1), low-intermediate (2), high-intermediate (3), and high (4-5). Overall survival was calculated using Kaplan-Meyer analysis with bivariate cox proportional hazard ratios to compare survival by facility type (academic or community centers) within these risk groups. Results: A total of 160,137 patients were identified. Of these cases 31.8% were classified as low risk, 21.9% were low-intermediate risk, 22.2% were high-intermediate risk, and 24% were high risk. 59.3% of patients were treated at a community center and 40.7% were treated at academic centers. Treatment at academic centers was associated with a significantly improved overall survival (OS) for each risk category. Median survival (in months) for high risk IPI score DLBCL was 47.9 months in community and 61.1 months in academic centers (p Conclusions: Facility type is significantly associated with improved survival outcomes across all IPI based risk groups for DLBCL. This benefit is especially significant in higher risk disease where positive outcomes are less common, suggesting treatment at academic centers may be particularly beneficial in these patients. Some of the possible reasons for this difference may include provider experience, increased access to resources, and opportunity for clinical trials. Further investigations into the factors contributing to such disparities should be done to help standardize care and improve outcomes. Disclosures No relevant conflicts of interest to declare.

Introduction : DLBCL is a heterogeneous disease with increasingly complex treatment selection. Prior studies demonstrated improved outcomes of hematologic malignancies managed in academic centers and based on socioeconomic factors. We aimed to compare OS of patients with DLBCL based on the type of treatment facility and other factors. Methods: This retrospective study utilized the National Cancer Data Base (NCDB) to identify patients with DLBCL diagnosed between 1998 and 2012. Health care facilities were categorized as either academic (academic/research program) or non-academic (comprehensive community cancer program, community cancer program, and other programs). Patients with complete data for sex, age, race, education, income, distance traveled for health care, hospital type, facility location, urban/rural, insurance, Charlson co-morbidity score, chemotherapy use, time from diagnosis to treatment initiation, use of hematopoietic stem cell transplant, last contact, and vital status were included. OS of patients who received first course treatment at academic centers, was compared to those treated at non-academic centers. Kaplan Meier curves for OS were compared using log-rank test. Multivariate Cox proportional hazard model was performed to identify determinants of OS. Results: Of 264,697 patients with DLBCL, 33% were treated at academic centers. Patients treated at academic centers differed from non-academic centers in mean age (65 vs. 68 years; p $63,000, p Conclusion : Our study demonstrated differences in the characteristics of patients with DLBCL based on the facility type. Academic centers were more likely to treat patients who were younger, females, of ethnic minorities, with less education, higher income levels, private insurance, less comorbidities and higher stage disease. The receipt of frontline therapy at academic centers was associated with increased OS in patients with DLBCL. Some of the possible reasons for this difference may include provider experience, increased access to resources and clinical trials. Our study also demonstrated cancer health disparities based on other socioeconomic factors such as gender, race, income and insurance status. Further investigations into the factors contributing to such disparities should be a research priority to help standardize care and improve outcomes. Figure 1 Kaplan-Meier curves Figure 1. Kaplan-Meier curves Disclosures Armitage: Conatus - IDMC: Consultancy; Roche: Consultancy; Spectrum Pharmaceuticals: Consultancy; GlaxoSmithKline IDMC: Consultancy; ZiopharmOncology: Consultancy; Tesaro bio Inc: Membership on an entity's Board of Directors or advisory committees.

Introduction : In curable malignancies, early mortality can significantly contribute to poor outcomes, particularly in older patients with comorbidities. Prior studies have demonstrated an association between survival, and health system and socioeconomic factors. The aim of this study was to analyze the association between such factors and 30-day mortality of patients diagnosed with DLBCL. Methods: This was a retrospective study that utilized the National Cancer Data Base (NCDB) to identify patients with DLBCL diagnosed between 1998 and 2012. Patients with complete data for sex, age, race, education, income, distance traveled for health care, hospital type, facility location, urban/rural, insurance, Charlson co-morbidity score, chemotherapy use, time from diagnosis to treatment initiation, use of hematopoietic stem cell transplant, 30 day mortality, last contact, and vital status were included. Chi-square test was used to examine the association between 30-day mortality and categorical variables. Multiple logistic regression model was used for multivariate analysis. Results: The study population included 51,119 individuals. Characteristics included a median age of 66 years, 92% whites and 47% females. The risk of 30-day mortality was 3.4% for the entire cohort. In a univariate analysis, female versus male sex (3.1% vs 3.4%, p=0.02), urban versus rural location (3.2% vs. 5.3%, p60 years (1.5% vs 4.4%, p In a multivariate analysis, females, compared to males, were more likely to be alive at 30 days (odds ratio, OR 1.16, 95% confidence interval, CI 1.04-1.29) (Table 1). Uninsured patients (OR 0.37, 95% CI 0.27-0.51) and patients with Medicare (OR 0.45, 95% CI 0.39-0.53), Medicaid (OR-0.40, 95% CI 0.30-0.54), and other government insurances (OR-0.28, 95% CI 0.17-0.47), compared to those with private insurance, had lower likelihood of surviving at 30 days. People from rural areas had a lower 30-day survival rates when compared to urban areas (OR-0.72, 95% CI 0.41- 0.80). Higher Charlson comorbidity, older age, higher AJCC stage were associated with lower 30-day survival rates. The 30-day survival did not differ with the race, annual income, level of education and type of treating facility. Conclusion: The 30-day mortality in patients with DLBCL depends not only on biologic factors such as age, comorbidities, and stage, but also on health system and socioeconomic factors such as gender, type of insurance, and location of the hospital. Further investigations into such factors contributing to the increased mortality may help reduce the gap in outcomes. Disclosures Armitage: ZiopharmOncology: Consultancy; GlaxoSmithKline IDMC: Consultancy; Spectrum Pharmaceuticals: Consultancy; Roche: Consultancy; Conatus - IDMC: Consultancy; Tesaro bio Inc: Membership on an entity's Board of Directors or advisory committees.

Background: Peg-asparaginasecan cause dysregulationof pro-coagulant and anti-coagulant proteins, resulting in a significant risk of venous thromboembolism(VTE) in ALL, particularly in adults undergoing induction chemotherapy. In late 2014, we adopted a policy at our institution to use prophylactic dose ofenoxaparin 40 mg daily for up to 3 weeks following the administration of peg-asparaginase. Patients are also to undergo monitoring of complete blood count, and coagulation parameters including fibrinogen and anti-thrombin. Enoxaparin may be held if patients develop severe thrombocytopenia (platelet count Methods: This is a single-center study of17 consecutive adult patients (>18 years old) treated for ALL with peg-asparaginasecontaining induction regimen before and after the establishment of institutional policy to useenoxaparinprophylaxis. Patients were identified from hospital research database. The diagnoses were verified. Medical records were reviewed for the occurrence of any clinically relevant bleeding and VTE within 3 months of receiving peg-asparaginase. Levels of coagulation parameters, whenever available, were collected at baseline and at weekly intervals for up to 4 weeks after receiving peg-asparaginase. The risk of bleeding and VTE among patients receivingenoxaparinwas compared to those who did not receiveenoxaparin. Fisher exact test was used for testing the association of categorical variable, and binomial exact test was used for computing confidence intervals. T-test or nonparametric test was used for comparing the continuous variables depending on whether or not the data were normally distributed. Results: The patient population consisted of 59% females. Mean age was 35 years. Histology consisted of Pre-B ALL in 76%, pre-T ALL in 18% and mixed lineage leukemia in 6%. 88% percent received pediatric-type chemoregimenand intramuscular peg-asparaginase; the most common doses of peg-asparaginaseincluded 2000 mg/m2 (41%) and 2500 mg/m2 (35%). Duration ofenoxaparin prophylaxis was 21 days in 66.7% and 7 days in 33.3%. Average changes in coagulation parameters at baseline and at weekly intervals following the use of peg-asparaginase therapy are highlighted in figures 1 and 2. The drop inantithrombin and fibrinogen levels was the highest during the first two weeks after the administration of peg-asparaginase. 41% of patients required cryoprecipitate (median 15 units, range 5-35 units over 4 weeks). No patients, including theenoxaparin group, had any clinically relevant bleeding event. The risk of VTE was 18% (95% confidence 4-43%); 2 out of 3 VTE events were cerebral venous thrombosis. No VTE occurred in theenoxaparin prophylaxis group (n=9), whereas 37% of patients (3 out of 8 patients), who did not receiveenoxaparin, developed VTE.Enoxaparin prophylaxis was associated with a trend towards a lower risk of VTE, however, the difference was not statistically significant (p=0.08). Conclusion: Within the limits of this study, in adult ALL patients receiving peg-asparaginase, the use of daily prophylactic dose ofenoxaparinmay not be associated with an increased risk of clinically relevant bleeding, and may have a potential to lower the risk of VTE. Patients receivingenoxaparin, however, should be carefully monitored for the need of platelet transfusion and cryoprecipitate supplementation. The difference in the risk of VTE was not statistically significant, which may be, in part, due to a small sample size.Antithrombindepletion may also contribute to a reduction in the efficacy ofenoxaparin. Larger prospective studies should be performed to validate the preliminary findings. Figure 1 Changes in prothrombin time and partial thromboplastin time Figure 1. Changes in prothrombin time and partial thromboplastin time Figure 2 Changes in antithrombin and fibrinogen levels Figure 2. Changes in antithrombin and fibrinogen levels Disclosures Armitage: Spectrum Pharmaceuticals: Consultancy; Roche: Consultancy; Conatus - IDMC: Consultancy; GlaxoSmithKline IDMC: Consultancy; ZiopharmOncology: Consultancy; Tesaro bio Inc: Membership on an entity's Board of Directors or advisory committees. Lunning:Genentech: Consultancy; AbbVie: Consultancy; Bristol-Myer-Squibb: Consultancy; Juno: Consultancy; Spectrum: Consultancy; Pharmacyclics: Consultancy; Celgene: Consultancy; Gilead: Consultancy; TG Therapeutics: Consultancy.