Introduction:

B-cell activating factor receptor (BAFF-R) enhances the survival and regulation of normal and malignant B cells. VAY736 is a human monoclonal antibody (mAb) targeting BAFF-R that targets BAFF-R+ B cells for elimination by antibody-dependent cell-mediated cytotoxicity (ADCC). VAY736 has anti-leukemia activity in preclinical CLL models that is superior to that of anti-CD20 mAbs (McWilliams EM, et al. Blood Adv 2019;3:447-460). Although Bruton's tyrosine kinase inhibitors (BTKis; acalabrutinib, ibrutinib) are the current standard of care for CLL, the indefinite length of monotherapy required may result in cumulative clinical or economic toxicity and/or acquired treatment resistance. In preclinical models, adding VAY736 to ibrutinib significantly improved survival and reduced disease burden, suggesting that this combination may augment the anti-leukemia response and allow patients (pts) to discontinue ibrutinib.

Methods:

This dose escalation/expansion trial (NCT03400176) enrolled pts with CLL undergoing either first- or second-line therapy with ibrutinib and whose disease failed to achieve a complete response (CR) after >1 year of therapy or who had CLL with a mutation associated with ibrutinib resistance. Pts received oral ibrutinib (420 mg) once daily and VAY736 IV at 0.3, 1, 3, or 9 mg/kg once every 2 weeks. In the expansion, pts were enrolled into 2 arms depending on whether ibrutinib resistance mutations were present at baseline. Pts received VAY736 + ibrutinib for up to 6 28-day cycles. After 6 cycles, pts with a CR discontinued VAY736 and received ibrutinib for an additional 2 cycles; all other pts continued VAY736 + ibrutinib for those 2 cycles. Pts achieving undetectable minimal residual disease (uMRD) at C9D1 could discontinue ibrutinib at the investigator's discretion. This study aimed to characterize the safety and tolerability of VAY736 + ibrutinib, determine the recommended dose for expansion (RDE), and explore the efficacy of this combination.

Results:

A total of 32 pts (median age 65 years; ECOG PS 0: 91%) were treated prior to data cutoff (May 10, 2021). Overall, 19 pts completed therapy and 4 discontinued VAY736 + ibrutinib (primarily due to disease progression); 4 pts remain on VAY736 + ibrutinib and 5 pts continue to receive ibrutinib. Of the enrolled pts, 44% had CLL cells with mutations associated with ibrutinib resistance (mainly [71%] BTKC481); the median number of prior regimens was 1 (range: 0.0-14.0); median duration of prior ibrutinib therapy was 3.5 years (range: 0.2-8.3). Baseline cytogenetics were (not mutually exclusive): 19% del(17)(p13.1), 75% unmutated IGHV, 59% stimulated complex karyotypes (≥3 abnormalities), 34% del(11)(q22.3), 44% del(13)(q14), and 6% +12.

No dose-limiting toxicities were observed and the RDE was 3 mg/kg, based on pharmacokinetics, exposure-to-response relationship, pharmacodynamics, safety, and in vitro ADCC. Twelve (38%) pts experienced AEs of Grade ≥3, most common (occurring in ≥2 pts) were neutrophil count decreased (n=5), lymphocyte count decreased (n=2), hypophosphatemia (n=2), and elevated lipase (n=2).

The overall response at C9D1 for evaluable pts (n=21) was 38% CR, 5% CRi, 14% PR, 24% SD, and 19% PD (Fig. 1A). Thirteen (41%) pts achieved uMRD in blood. Eight pts (42%, 8/19) and 8 pts (42%, 8/19) had uMRD in blood and bone marrow (BM) at end of treatment (EoT), respectively. Among those, 6 pts were elected to discontinue ibrutinib and remained off treatment for 0.2-26.2 months and were still off therapy at the data cutoff. The median percentage change from baseline in MRD was -99.0% (range: -100.0% to -16.7%) and -97.3% (range: -100.0% to 1346.3%) in blood and BM, respectively. None of the pts who enrolled with CLL cells lacking mutations associated with ibrutinib resistance (11/11) developed mutations by C9D1. Although 1 pt with PLCG2 mutation eradicated mutant clones at EoT with VAY736, the response may vary depending on the type of mutation (Fig. 1B).

Conclusions:

VAY736 + ibrutinib was well tolerated with an acceptable safety profile enabling dose expansion. Clinical activity was observed including multiple pts attaining uMRD status in blood and BM, allowing 6 to discontinue ibrutinib therapy for an extended period. These data provide clinical evidence of the potent anti-leukemia activity of VAY736 and the potential to safely discontinue ibrutinib or other BTKi by VAY736 add-on therapy.

Figure 1
Figure 1.
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Disclosures

Rogers: AbbVie: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy; Pharmacyclics: Consultancy; Innate Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Janssen: Research Funding. Flinn: TG Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Gilead Sciences: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Yingli Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; MorphoSys: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; BeiGene: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Karyopharm Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Constellation Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; IGM Biosciences: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Forty Seven: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Agios: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Seagen: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Iksuda Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Juno Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Janssen: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Genentech: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Great Point Partners: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Verastem: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; AbbVie: Consultancy, Other: All Consultancy and Research Funding payments made to Sarah Cannon Research Institute, Research Funding; AstraZeneca: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Novartis: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Loxo: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Roche: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Kite, a Gilead Company: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Takeda: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Celgene: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Calithera Biosciences: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; ArQule: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Curis: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Unum Therapeutics: Consultancy, Other: All consultancy and research funding payments made to Sarah Cannon Research Institute, Research Funding; Forma Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Nurix Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Merck: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Teva: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Incyte: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Infinity Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Acerta Pharma: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Trillium Therapeutics: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Pfizer: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Portola Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Rhizen Pharmaceuticals: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Triphase Research & Development Corp.: Other: All research funding payments made to Sarah Cannon Research Institute, Research Funding; Century Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Hutchison MediPharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Vincerx Pharma: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Sarah Cannon Research Institute: Current Employment; Servier Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Yingli Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Seagen: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Servier Pharmaceuticals: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute; Unum Therapeutics: Consultancy, Other: All consultancy payments made to Sarah Cannon Research Institute, Research Funding; Johnson & Johnson: Current holder of individual stocks in a privately-held company; Seattle Genetics: Research Funding. Stephens: TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Adaptive: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Epizyme: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; JUNO: Research Funding; Arqule: Research Funding; AstraZeneca: Consultancy; Abbvie: Consultancy; Mingsight: Research Funding; CSL Behring: Consultancy; Celgene: Consultancy; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kipps: Oncternal Therapeutics, Inc.: Current equity holder in publicly-traded company, Patents & Royalties: Cirmtuzumab, Research Funding; Pharmacyclics/AbbiVie: Honoraria, Research Funding; Genentech/Roche: Honoraria; Celgene: Honoraria, Research Funding; VelosBio, Inc.: Research Funding; Janssen, Gilead, Dava Oncology,: Honoraria; Breast Cancer Research Foundation: Honoraria, Research Funding; Md Anderson Cancer Center: Research Funding; Gilead: Honoraria; National Cancer Institute/NIH: Honoraria, Research Funding; OncLive: Honoraria; Specialized Center of Research (SCOR) - The Leukemia and Lymphoma Society (LLS): Research Funding; California Institute for Regenerative Medicine (CIRM): Research Funding; European Research Initiative on CLL (ERIC): Honoraria; Dava Oncology: Honoraria; Patient Power, LLC: Honoraria; iwNHL: Honoraria; NCCN CLL/SLL Hairy Cell Leukemia Panel Meeting: Honoraria. Larson: TORL biotherapeutics: Current holder of individual stocks in a privately-held company; Abbvie: Research Funding; Bioline: Research Funding; BMS: Research Funding; Celgene: Research Funding; GSK: Research Funding; Janssen: Research Funding; Juno: Research Funding; Novartis: Research Funding; Pfizer: Research Funding; Takeda: Research Funding. McGarry: Novartis Institutes for Biomedical Research: Current Employment. Hassounah: Novartis Institutes for Biomedical Research: Current Employment, Patents & Royalties: unrelated . Gou: Novartis Pharma AG: Current Employment. Woo: Novartis: Current Employment, Current equity holder in publicly-traded company. Byrd: Novartis, Trillium, Astellas, AstraZeneca, Pharmacyclics, Syndax: Consultancy, Honoraria; Newave: Membership on an entity's Board of Directors or advisory committees; Vincerx Pharmaceuticals: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees.

© 2021 by The American Society of Hematology
2021
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