Its approval in patients with CLL and MCL1,2 marked the advent of a new era in the treatment of B-cell malignancies, based on clinical efficacy in previously difficult to treat lymphomas, such as treatment-resistant/refractory chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), and Waldenström’s macroglobulinemia3–6. The gene discussed is MCL1; the disease is mantle cell lymphoma.