A phase 2 study of ibrutinib with venetoclax in Japanese patients with untreated CLL and SLL

The development of effective and safe therapies for chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) in Japan remains a key focus of research. We conducted a phase 2, open-label, multicenter, non-comparative study to evaluate the safety and efficacy of fixed-duration venetoclax plus ibrutinib in 10 patients with previously untreated CLL/SLL (7 CLL/3 SLL). The primary endpoint was the rate of complete remission (CR)/CR with incomplete marrow recovery (CRi) assessed by the independent review committee (IRC). The median age was 72.5 (range 61-77) years. The IRC-assessed CR/CRi rate was 60.0% (95% confidence interval: 26.2-87.8%), exceeding the pre-specified efficacy threshold of 10% and meeting the primary endpoint. The median venetoclax treatment duration was 11.0 (range 2.1-17.7) months. At a median follow-up of 20.6 months, the secondary endpoints of median progression-free and overall survival were not estimated. The overall undetectable measurable residual disease rate was 60.0%. All patients experienced treatment-emergent adverse events (TEAEs), including 7 (70.0%) with grade 3/4 and 2 (20.0%) with serious TEAEs, respectively, and 1 discontinued venetoclax because of a TEAE (increased blood creatine phosphokinase). These findings suggest that venetoclax plus ibrutinib has a favorable benefit-risk profile with high efficacy and manageable safety.