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Background: BCL2, a key regulator of apoptosis, is aberrantly expressed in many hematologic malignancies, which can lead to pathologic cancer cell survival. BCL2 inhibitors have been shown to be safe and effective, resulting in their approval for the treatment of pts with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and acute myeloid leukemia. Treatment with the currently approved BCL2 inhibitor, venetoclax, can be limited by common gastrointestinal toxicities, neutropenia, and the emergence of specific BCL2 mutations around the BH3-binding groove causing resistance. BGB-11417 was developed as a potent and highly selective inhibitor of BCL2. It has shown antitumor activity superior to venetoclax in human acute lymphoblastic leukemia, mantle cell lymphoma (MCL), and diffuse large B-cell lymphoma (DLBCL) xenograft models (Hu, AACR 3077). BGB-11417 also has a favorable pharmacokinetic profile with excellent bioavailability and selectivity for BCL2 at concentration The combination of a BCL2 inhibitor and a BTK inhibitor is tolerable with synergistic activity in CLL and MCL pts (Hillmen, J Clin Oncol 2019;37(30):2722-9; Jain, N Engl J Med 2019;30;380(22):2095-103; Siddiqi, ASH 2020 S158; Tam, N Engl J Med 2018; 378:1211-23). Zanubrutinib is a next-generation BTK inhibitor that has shown excellent activity and favorable toxicity in pts with CLL/SLL (Hillmen, EHA 2021 LB1900) and MCL (Tam, Blood Adv 2021;5(12):2577-85); with approval for treatment in MCL. Here we report preliminary results of the BGB-11417-101 trial (NCT04277637) in pts with non-Hodgkin lymphoma (NHL) or CLL/SLL treated with BGB-11417 monotherapy or in combination with zanubrutinib. Methods: BGB-11417-101 is a phase 1, open label, multicenter, dose-escalation and expansion study. Pts with NHL or CLL/SLL are treated with BGB-11417 as monotherapy or in combination with zanubrutinib. For dose escalation, pts with R/R B-cell malignancies are enrolled in 1 of 5 potential dose levels of BGB-11417 (40, 80, 160, 320, or 640 mg once daily). All pts utilize a ramp-up to intended target dose that varies by disease type. Pts in the combination therapy arm receive zanubrutinib 320 mg daily beginning 8-12 weeks before BGB-11417 is introduced. Adverse events (AEs) are reported per Common Terminology Criteria for AEs v5.0. Dose-limiting toxicity (DLT; assessed from ramp-up through day 21 at intended daily dose), evaluated by Bayesian logistic regression model, will be used to determine the maximum tolerated dose (MTD). Results: As of 24 May 2021 (data cutoff) 19 pts had been treated; 14 pts with monotherapy (NHL: n=11; CLL/SLL: n=3) and 5 pts with combination (all CLL; 3 pts were still on zanubrutinib pretreatment; 2 had started combination treatment). Median age was 72 y (range, 50-86); median follow-up was 1.9 mo (range, 0.7-12.4); all pts were R/R with a median of 2 prior regimens (range, 1-4). No DLTs were observed in pts with NHL receiving BGB-11417 monotherapy (n=11) up to the 160 mg dose level. AEs across all dose levels occurring in ≥2 pts (monotherapy) or ≥1 pt (combination) are listed in Table 1. A total of 5 pts discontinued treatment (all NHL) due to disease progression (n=4; 2 at 40 mg, 2 at 80 mg) or lack of efficacy (n=1 at 40 mg). No pt discontinued due to AEs. Laboratory tumor lysis syndrome was observed in 1 pt with CLL and high tumor burden (resolved with no sequelae). Initial efficacy after 3-month restaging in pts with CLL/SLL demonstrated 1 partial response (monotherapy arm) at the first dose level tested. All pts with CLL/SLL who have completed ramp-up (n=2, both monotherapy) normalized absolute lymphocyte count (ALC). Marked decreases in ALC were observed in pts with CLL at doses as low as 1 mg (Figure 1). Conclusion: Preliminary results suggest that BGB-11417 monotherapy is tolerable in pts with R/R NHL at the tested dose levels. Further assessment of safety and efficacy of BGB-11417 +/- zanubrutinib in CLL/SLL and NHL will be presented at the meeting, and evaluation in patients with treatment naïve CLL/SLL, R/R MCL, and R/R WM is planned. Figure 1 Figure 1. Disclosures Tam: AbbVie: Consultancy, Honoraria, Research Funding; BeiGene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Loxo: Consultancy; Novartis: Honoraria; Pharmacyclics: Honoraria. Verner: Janssen-Cilag Pty Ltd: Research Funding. Lasica: Celgene: Other: Travel, Accommodations, Expenses; Janssen: Other: Education. Arbelaez: Amgen: Other: Travel, Accommodations, Expenses. Browett: AbbVie: Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees; MSD: Membership on an entity's Board of Directors or advisory committees. Soumerai: BeiGene: Consultancy, Research Funding; AstraZeneca: Consultancy; Adaptive Biotechnologies: Consultancy, Research Funding; AbbVie: Consultancy; GlaxoSmithKline: Research Funding; BostonGene: Research Funding; BMS: Consultancy; Seattle Genetics: Consultancy; TG Therapeutics: Consultancy, Research Funding. Hilger: BeiGene: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Fang: BeiGene (Shanghai) Co, Ltd.: Current Employment, Current equity holder in publicly-traded company. Huang: BeiGene: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Divested equity in a private or publicly-traded company in the past 24 months, Other: Travel, Accommodations, Expenses; Protara Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Simpson: Janssen: Research Funding; GSK: Research Funding; Pharmacyclics: Research Funding; Acerta: Research Funding; MSD: Research Funding; Roche: Research Funding; Celgene: Research Funding; Amgen: Research Funding; AbbVie: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; BeiGene: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Opat: Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Janssen: 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; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GIlead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Monash Health: Current Employment; BeiGene: Research Funding; Sandoz: Research Funding. Cheah: Ascentage Pharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Lilly: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; TG therapeutics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Beigene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Zanubrutinib is an investigational agent and has not been approved for NHL or CLL/SLL in the US

Introduction: TG-1701 is an irreversible, selective, novel Bruton's tyrosine kinase inhibitor (BTKi) administered once daily (QD). BTK inhibitors, as well as the U2 combination (anti-CD20 mAb ublituximab + the PI3Kδ-CK1ε inhibitor umbralisib), are highly efficacious in chronic lymphocytic leukemia (CLL), each of which have been previously demonstrated to be superior over standard chemoimmunotherapy. Treatment with a more selective BTK inhibitor could result in improved efficacy and safety outcomes compared with ibrutinib (ALPINE study, EHA 2021), and we hypothesized that dual blockade of the B-cell receptor (BCR) pathway through combination of TG-1701 with U2 may confer greater depth of response compared to either regimen alone. Methods: Patients with CLL and non-Hodgkin lymphoma (NHL) were enrolled in an ongoing Phase 1 study. After characterizing the safety profile of TG-1701 monotherapy, a parallel dose escalation arm of TG-1701+U2 was implemented. Select dose levels of TG-1701 monotherapy and TG-1701+U2 were also expanded. All patients were treated until disease progression, unacceptable toxicity, or investigator/patient decision to withdraw. Safety was evaluated in all treated patients, and efficacy was evaluated in all treated patients who had at least 1 post-baseline assessment. TG-1701 monotherapy data were previously presented; herein we present data from the TG-1701+U2 dose escalation/expansion and the TG-1701 monotherapy CLL expansion cohorts Results: As of July 2021, 142 patients were treated with TG-1701, 36 of whom were enrolled in the TG-1701+U2 arm. The median # of prior therapies across all treated patients was 1 (range, 0-10) and all patients were BTKi-naïve. Among the 36 patients treated with U2+1701, 19 were evaluable for efficacy and safety (17 too early to evaluate). The median age was 69 years (range 47-81), and 56% were male. TG-1701+U2 was well tolerated at 4 different dose levels without dose-limiting toxicities. The most common (>30%) all-causality, all grade treatment-emergent adverse events (TEAEs) were diarrhea (53%) contusion (42%), nausea (37%), hypertension, ALT/AST increase, and fatigue (all 32% each) with TG-1701+U2. Grade 3/4 AEs >15% were limited to ALT/AST increase (21%). Dose reduction occurred in 1 patient due to an AE, and 4 patients discontinued at least 1 study drug due to an AE: 2 discontinued umbralisib, 1 discontinued umbralisib and TG-1701, and 1 discontinued all 3 agents. At the data cut-off, overall response rate (ORR) was 84% (4 CR and 12 PR) among 19 evaluable patients, with remaining patients awaiting post-baseline assessment. In the monotherapy CLL-specific cohorts (200 mg QD, n=20; and 300 mg QD, n=20), 40 pts were evaluable for safety, and 39 for efficacy (1 pt withdrew due to COVID prior to first response assessment). The median age was 71 (range 49-86), and 43% were male. The most common TEAEs were increased ALT/AST (all grades: 18%; grade ≥3: 3%), followed by diarrhea (all grades: 15%; grade ≥3: none), and neutropenia (all grades: 13%; grades ≥3: 13%). There were no cases of atrial fibrillation, major bleeding, or ventricular tachyarrhythmia in the CLL cohorts at a median follow-up of 12.8 months (range 2.5 - 20.8). TEAEs leading to TG-1701 dose reduction occurred in 1 (3%) patient. No patients in the 200 mg or 300 mg CLL cohorts have discontinued due to AEs. In patients with anemia and thrombocytopenia at baseline, sustained improvement in hematologic variables was observed. The ORR among 39 patients was 97% (all PR/PR-L). Lymphocytosis resolved to normal value or The median duration of response has not been reached in either cohort. Best change in tumor burden from baseline in patients with CLL is presented in Figure 1. Conclusions: TG-1701 exhibits an encouraging safety and efficacy profile as monotherapy in patients with CLL and additionally shows promising activity and a manageable tolerability profile in combination with U2. Future registration trials are being planned in CLL with TG-1701. Recruitment to this study (NCT03671590) continues. Figure 1 Figure 1. Disclosures Cheah: MSD: Consultancy, Honoraria, Other: advisory, Research Funding; TG Therapeutics: Consultancy, Honoraria, Other: advisory; Loxo/Lilly: Consultancy, Honoraria, Other: advisory; AstraZeneca: Consultancy, Honoraria, Other: advisory; Celgene: Research Funding; AbbVie: Research Funding; Ascentage pharma: Consultancy, Honoraria, Other: advisory; Beigene: Consultancy, Honoraria, Other: advisory; Roche: Consultancy, Honoraria, Other: advisory and travel expenses, Research Funding; Janssen: Consultancy, Honoraria, Other: advisory; Gilead: Consultancy, Honoraria, Other: advisory. Jurczak: Abbvie: Research Funding; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celtrion: Research Funding; Celgene: Research Funding; Debbiopharm: Research Funding; Epizyme: Research Funding; Incyte: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Loxo Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Mei Pharma: Research Funding; Morphosys: Research Funding; Novo Nordisk: Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sandoz: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Research Funding; TG Therapeutics: Research Funding. Lasica: Abbvie: Speakers Bureau; Celgene: Other: Ambassadorship. Wróbel: Janssen: Honoraria, Speakers Bureau; Roche: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; BeiGene: Honoraria, Speakers Bureau. Walewski: roche: Honoraria, Research Funding, Speakers Bureau; GSK: Research Funding; novartis: Honoraria, Research Funding; takeda: Consultancy, Honoraria; abbvie: Consultancy, Honoraria; gilead: Consultancy, Honoraria; amgen: Consultancy, Honoraria; seervier: Consultancy, Honoraria. Giannopoulos: Sanofi-Genzyme: Consultancy, Honoraria, Research Funding; GSK: Consultancy, Honoraria, Research Funding; Sandoz: Consultancy, Honoraria; TG Therapeutics: Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Astra-Zeneca: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria; Gilead: Honoraria, Research Funding; Bei-Gene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Teva: Honoraria; Roche: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Polish Myeloma Consortium, Next Generation Hematology Association: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Honoraria, Research Funding. Lewis: AstraZeneca: Consultancy, Honoraria; Janssen: Honoraria, Patents & Royalties; Novartis: Patents & Royalties; Roche: Consultancy, Honoraria. Dlugosz-Danecka: Janssen: Consultancy, Research Funding; Roche: Consultancy, Research Funding, Speakers Bureau; Servier: Consultancy, Speakers Bureau; Acerta Pharma: Research Funding; AbbVie: Research Funding; Macrogenics: Research Funding; Beigene: Research Funding; MEI Pharma: Research Funding; Incyte Corp.: Research Funding; Takeda: Research Funding. Miskin: TG Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Ricart: TG Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company; Pfizer: Current equity holder in publicly-traded company; Merck: Current equity holder in publicly-traded company; Seagen: Current equity holder in publicly-traded company; Gilead: Current equity holder in publicly-traded company. O'Connor: Mundipharma: Consultancy; Kymera: Consultancy, Current equity holder in publicly-traded company; TG Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company; Nomocan: Consultancy; Myeloid Therapeutics: Consultancy, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company; Dren: Consultancy, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Tam: BeiGene: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Loxo: Consultancy; Roche: Consultancy, Honoraria; Novartis: Honoraria; Pharmacyclics: Honoraria.