Purpose: We previously reported a 44% overall response rate (ORR) with the oral BCL-2 inhibitor venetoclax in a phase I study of relapsed/refractory non-Hodgkin lymphoma (NHL). Complete response (CR) was observed in patients with mantle cell lymphoma [(MCL), 21%, n = 6/28] and follicular lymphoma [(FL), 17%, n = 5/29], and partial response (PR) noted in several patients with Waldenström macroglobulinemia (WM), and marginal zone lymphoma (MZL). Here, we report the long-term outcomes of these four cohorts.
Patients and methods: All patients (n = 106) received venetoclax monotherapy in dose cohorts of 200 to 1,200 mg daily until disease progression or unacceptable toxicity. ORR, progression-free survival (PFS), duration of response (DoR), and adverse events (AEs) were evaluated.
Results: At a median follow-up of 38.5 months (range, 30.0-46.5), the median PFS for all 106 patients was 5.4 [95% confidence interval (CI), 3.5-8.4] months (FL, 10.8; MCL, 11.3; MZL, 21.2; and WM, 30.4). The median DoR was 14.9 (95% CI, 9.7-27.6) months (FL, 26.6; MCL, 15.7; MZL, 20.1; and WM, 25.3). Achievement of CR versus PR predicted longer DoR in both MCL (31.5 vs. 10.1 months) and FL (37.6 vs. 9.7 months). All grade hematologic AEs were infrequent: neutropenia (19%), anemia (19%), and thrombocytopenia (17%), with no new cytopenias after 2 years on therapy. Nonhematologic AEs included nausea (49%), diarrhea (46%), fatigue (44%), with decreased incidence after 1 year.
Conclusions: Venetoclax monotherapy has a manageable safety profile and achieves durable responses in a subset of patients with FL, MCL, WM, and MZL, particularly in those who achieve CR. Further research is warranted on combination strategies to enhance the durability of response to venetoclax.
Trial registration: ClinicalTrials.gov NCT01328626.
©2021 The Authors; Published by the American Association for Cancer Research.