Ibrutinib improves outcomes in continuously-treated TCL1 mice. (A) Continuous administration of ibrutinib inhibits the development of CLL in TCL1 mice. TCL1 mice were randomized at 1 month of age to treatment with vehicle drinking water (n = 24) or ibrutinib drinking water (n = 24), and monitored for leukemia development by monthly peripheral blood flow cytometry. Ibrutinib significantly impairs leukemia development (P < .0001). (B) Continuous administration of ibrutinib improves survival in TCL1 mice. TCL1 mice were randomized at 1 month of age to treatment with vehicle drinking water (n = 24) or ibrutinib drinking water (n = 24) and followed for survival. Survival was significantly improved by ibrutinib administration compared with vehicle (P < .0001).