Safety and Efficacy of a Combination of Venetoclax (GDC-0199/ABT-199) and Obinutuzumab in Patients with Relapsed/Refractory or Previously Untreated Chronic Lymphocytic Leukemia - Results from a Phase 1b Study (GP28331)

• Published in: Blood 2015-12, Vol.126 (23), p.494-494
• Main Authors: Flinn, Ian W., Brunvand, Mark, Choi, Michael Y., Dyer, Martin J.S., Gribben, John, Hillmen, Peter, Jones, Jeffrey, Li, Yan, Mobasher, Mehrdad, Vosganian, Gregory, Kipps, Thomas J.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V126.23.494.494

▪ Introduction Treatment of patients (pts) with relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL) with the combination of venetoclax (VEN), an oral, selective Bcl-2 inhibitor, and rituximab yielded an ORR of 84% (Roberts et al. Haematologica 2015). Treatment of such pts with VEN in combination with obinutuzumab (Gazyva®, Gazyvaro™, G), a Type II, glycoengineered anti-CD20 antibody, may yield even better treatment outcomes. We present preliminary efficacy and updated safety data from an ongoing phase 1b study (NCT01685892) evaluating this combination in R/R or treatment-naïve (TN) pts with CLL in alternate treatment schedules. Methods Pts with CLL with an ECOG PS ≤1 and adequate organ function are enrolled in a study with a 3+3 design and cohorts ranging from 100 to 600 mg/day of VEN. Pts are assigned to one of two dosing schedules, starting treatment with either VEN (Schedule A) or G (Schedule B). Both schedules include tumor lysis syndrome (TLS) risk mitigation based on disease burden at screening, which includes a gradual VEN ramp-up to the assigned cohort dose. Six cycles of combination therapy will be given and then pts with R/R disease continue single-agent VEN until disease progression; TN pts will receive single-agent VEN for an additional 6 months. Dose-limiting toxicities (DLTs) are identified during the first 21 days of combination therapy in Schedule A or the first 35 days of combination therapy in Schedule B, and focus on TLS, infusion related reactions, and cytopenias. Based on a safety review of data from this trial, the 600 mg cohort will not be explored. Response is first assessed before Cycle 4 according to 2008 International Workshop on CLL guidelines. Results As of April 20, 2015, 32 pts (26 R/R and 6 TN) have been enrolled. Four R/R pts were unenrolled after a sponsor-initiated clinical hold secondary to TLS events in other VEN studies. Patient characteristics include a median age 62.5 (range, 45-80) years, and 62.5% male pts. TLS risk was assessed in 28 pts following protocol modifications adopted after a Sponsor-initiated clinical hold; 96.4% were at medium or high risk for TLS. The highest VEN dose administered in this study was 400 mg/day (administered to 11 R/R and 6 TN pts). Median time on study was 5.5 (range, 0.1-19.6) mo. for all pts and 2.8 (range, 0.9-2.8) mo. for TN pts. Among pts exposed to VEN, dose interruptions were observed in 17/27 (63%) pts. A summary of AEs is presented in Figure 1. Laboratory TLS was obse