Obinutuzumab plus fludarabine/cyclophosphamide or bendamustine in the initial therapy of CLL patients: the phase 1b GALTON trial

Obinutuzumab is a type 2, glycoengineered, anti-CD20 antibody recently approved with chlorambucil for the initial therapy of chronic lymphocytic leukemia (CLL). In this nonrandomized, parallel-cohort, phase 1b, multicenter study, we explored the safety and preliminary efficacy of obinutuzumab-bendamustine (G-B) or obinutuzumab fludarabine cyclophosphamide (G-FC) for the therapy of previously untreated fit patients with CLL. Patients received up to 6 cycles of G-B (n = 20) or G-FC (n = 21). The primary end point was safety, with infusion-related reactions (88%, grade 3-4 20%) being the most common adverse event and grade 3-4 neutropenia in 55% on G-B and 48% on G-FC. Mean cycles completed were 5.7 for G-B and 5.1 for G-FC, with 2 and 7 early discontinuations, respectively. The objective response rate (ORR) for G-B was 90% (18/20) with 20% complete response (CR) and 25% CR with incomplete marrow recovery (CRi). The ORR for G-FC was 62% (13/21), with 10% CR and 14% CRi, including 4 patients not evaluable. With a median follow-up of 23.5 months in the G-B cohort and 20.7 months in the G-FC cohort, no patient has relapsed or died. We conclude that obinutuzumab with either B or FC shows manageable toxicity and has promising activity.