Targeted Therapies in Chronic Lymphocytic Leukemia: Is 2 (or 3) Better Than 1?

Small molecule inhibitors, including B-cell receptor antagonists and B-cell lymphoma - 2 inhibitors, have revolutionized the treatment of chronic lymphocytic leukemia (CLL). These agents have improved outcomes for patients of all prognostic backgrounds, thus securing their role in the frontline setting. Impressive activity has been demonstrated both with monotherapy and in combination with other targeted therapeutics. The most important remaining question is whether to administer small molecule inhibitors in a sequential fashion or in combination with each other and/or anti-CD20-directed therapy. Together, a number of retrospective and prospective clinical trials have provided insight into patient outcomes with different sequencing and combination strategies. While rituximab does not appear to provide significant additional benefit to ibrutinib, the incorporation of venetoclax appears to enable a deeper response and allow for a shorter duration of therapy. How durable of a response this produces and whether patients can be effectively retreated with venetoclax remain unclear. As various targeted therapy doublets and triplets are explored, it is important to investigate whether they produce significant long-term benefits over monotherapy and whether these approaches are appropriate for all patients.