The BCL-2 antagonist venetoclax, specifically if combined with a CD20 antibody proved highly active in clearance of chronic lymphocytic leukemia (CLL) cells in peripheral blood (PB) and bone marrow (BM) but less so in lymph nodes (LN), probably due to the abundant expression of additional anti-apoptotic proteins within the LN compartment. The investigators hypothesize that due to the forced egress from the LN by ibrutinib, leukemic cells cannot escape from the apoptosis initiating effects of venetoclax, making combination of these drugs highly effective. Preliminary data from multiple ongoing trials on this combination are indeed promising, with not only superior rates of undetectable minimal residual disease (uMRD) than other ibrutinib combinations but perhaps more important, achievement of complete LN responses in the majority of patients. Yet, also with this combination, a significant subgroup of patients are expected to remain with detectable MRD. A recent study showed that 6 cycles of obinutuzumab when given after at least 1 year of ibrutinib did result in MRD conversion in a significant proportion of patients (50%). The precise influence, timing and interplay of venetoclax, ibrutinib and obinutuzumab on clearance of CLL cells in different compartments (PB, BM, LN), and achievement of uMRD and complete remission (CR) are not well known.~Therefore, the investigators set out a study to evaluate whether patients who are not in CR or who have detectable MRD after 12 months of combination treatment with ibrutinib and venetoclax (15 months total treatment including three months ibrutinib lead-in) could be converted into uMRD CR with an additional 6 cycles obinutuzumab in combination with ibrutinib. In addition to efficacy, as measured by undetectable MRD rate, emphasis of this trial will be on clearance of different compartments (PB, BM, LN) at different time points on protocol and in follow up. In addition, the toxicity profile is taken into consideration.
A recent study showed that 6 cycles of obinutuzumab when given after at least 1 year of ibrutinib did result in MRD conversion in a significant proportion of patients (50%). The precise influence, timing and interplay of venetoclax, ibrutinib and obinutuzumab on clearance of CLL cells in different compartments (PB, BM, LN), and achievement of uMRD and complete remission (CR) are not well known.~Therefore, the investigators set out a study to evaluate whether patients who are not in CR or who have detectable MRD after 12 months of combination treatment with ibrutinib and venetoclax (15 months total treatment including three months ibrutinib lead-in) could be converted into uMRD CR with an additional 6 cycles obinutuzumab in combination with ibrutinib.