BTK and mantle cell lymphoma: The first-generation BTK inhibitor, ibrutinib (PCI-32765), has produced significant clinical response in patients with chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), diffuse large B cell lymphoma (DLBCL) [activated B cell (ABC)-like subtype] as well as in patients with Waldenstrom's macroglobulinemia (WM) [44–46].