MAP2K7 and hairy cell leukemia: Based on encouraging preclinical data demonstrating decreased MEK-ERK signaling, inhibition of proliferation and reduced survival of HCL cells when exposed to ibrutinib [61], a single-arm phase II study was initiated investigating ibrutinib at a daily dose of either 420 mg (n = 24) or 840 mg (n = 13) in 37 patients with relapsed HCL or its variant (Table 4) [13].