Safety and Efficacy of Venetoclax (ABT-199/GDC-0199) in Combination with Bortezomib and Dexamethasone in Relapsed/Refractory Multiple Myeloma: Phase 1b Results

Abstract

Abstract Background: The anti-apoptotic proteins BCL-2 and MCL-1 promote multiple myeloma (MM) cell survival. Bortezomib (BTZ) can inhibit MCL-1 activity by stabilizing the MCL-1 antagonist, NOXA. Venetoclax is an orally bioavailable, highly selective BCL-2 inhibitor, which enhances BTZ efficacy in MM xenograft models. This Phase 1 study evaluates venetoclax with BTZ and dexamethasone (Dex) in patients (pts) with relapsed/refractory MM. Methods: Objectives include safety, pharmacokinetics, preliminary efficacy and maximum therapeutic dose of venetoclax with BTZ and Dex. A fixed dose of venetoclax ranging from 50 to 800 mg PO daily, according to dose cohort assignment, was given in combination in cycles (C) 1-11 and alone in C12 and beyond. Dose escalation decisions were made using the continual reassessment method. Pts received BTZ (1.3 mg/m2 SC, days [D] 1, 4, 8, 11) and Dex (20 mg PO, D1, 2, 4, 5, 8, 9, 11, 12) in cycles (C)1-8 (21D), then BTZ + Dex (D1, 8, 15, 22) in C9-11 (35D). Results: Forty-one pts were enrolled as of June 15, 2015 (pts in each cohort: 50 mg, n=3; 100 mg, n=5; 200 mg, n=6; 300 mg, n=7; 400 mg, n=6; 500 mg, n=7; 600 mg, n=5; 800 mg, n=2). Median age was 65 (38-79); 15/26 F/M. 14 were ISS stage I, 11 stage II, 11 stage III, 5 missing. Median (range) number of prior lines of therapy was 5 (1-15). Thirty-five pts had received prior BTZ (10 refractory), 34 prior lenalidomide (22 refractory); 29 had undergone stem cell transplantation. Based on FISH analysis, 5 pts had MM with t(11;14); 3 with t(4;14), 20 with del 17p, and 10 with del 13q. Treatment-emergent AEs occurring in ≥20% of pts were constipation (37%), diarrhea (37%), thrombocytopenia (32%), asthenia (29%), insomnia (29%), anemia (27%), peripheral neuropathy (27%), dyspnea (24%), peripheral edema (22%), and nausea (20%). Grade 3/4 AEs in ≥10% of pts were thrombocytopenia (20%), and anemia (17%). SAEs occurred in 18 pts; SAEs in ≥2 pts were cardiac failure, embolism, pyrexia, respiratory failure, sepsis, thrombocytopenia (n=2 each, no SAEs were venetoclax-related). Twenty-nine pts have discontinued treatment: 23 due to PD, 2 due to AEs [adenocarcinoma; cardiac and respiratory decompensation attributed to Dex (DLT at 300 mg)], and 4 withdrew consent. Three deaths occurred (all due to PD). No TLS occurred. In preliminary PK analyses (n=41), dose-normalized venetoclax exposure when given with BTZ+Dex was similar when compared to venetoclax monotherapy in MM as well as CLL and NHL pts. Forty of 41 pts were evaluable for efficacy. All responses occurred in BTZ sensitive or naïve pts. Median (range) duration or response was 5.9 (0-14.1) months in all pts, 8.5 (2.3-11.4) months in BTZ naïve pts, and 4.7 (0-14.1) months in BTZ-sensitive pts. Conclusions: Venetoclax with BTZ and Dex has an acceptable safety profile in heavily pretreated MM pts; no new safety signals were identified compared to other venetoclax studies. These early data suggest the combination of proteasome and BCL-2 inhibition resulted in anti-tumor activity. Responses were observed only in pts naïve or sensitive to prior BTZ (ORR = 100% and 58%, respectively) and occurred in all dose cohorts. The study is currently enrolling pts in the 1000 mg dose escalation cohort. Figure 1. Figure 1. Disclosures Moreau: Celgene, Janssen, Takeda, Novartis, Amgen: Membership on an entity's Board of Directors or advisory committees. Off Label Use: Venetoclax is an investigational drug that is not yet approved in this indication. Roberts:AbbVie and Genentech: Research Funding; Walter and Eliza Hall Institute of Medical Research: Employment. Agarwal:Amgen, Millennium: Consultancy; Celgene, Onyx: Speakers Bureau; AbbVie: Research Funding. Facon:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millenium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Pierre Fabre: Membership on an entity's Board of Directors or advisory committees. Kumar:Skyline, Noxxon: Honoraria; Celgene, Millennium, Onyx, Janssen, Noxxon, Sanofi, BMS, Skyline: Consultancy; Celgene, Millennium, Onyx, Novartis, Janssen, Sanofi: Research Funding. Touzeau:AbbVie: Research Funding. Darden:AbbVie: Employment, Equity Ownership. Morris:AbbVie: Employment, Equity Ownership. Ross:AbbVie: Employment, Equity Ownership. Salem:AbbVie: Employment, Equity Ownership. Munasinghe:AbbVie: Employment, Equity Ownership. Zhu:AbbVie: Employment, Equity Ownership. Leverson:AbbVie: Employment, Equity Ownership. Maciag:AbbVie: Employment, Equity Ownership. Enschede:AbbVie: Employment, Equity Ownership. Verdugo:AbbVie: Employment, Equity Ownership. Humerickhouse:AbbVie: Employment, Equity Ownership. Harrison:Celgene: Honoraria, Research Funding; Janssen: Research Funding, Speakers Bureau; AbbVie: Research Funding.