Targeted therapy for treatment of patients with classical hairy cell leukemia.

Most patients with treatment naïve classical hairy cell leukemia (cHCL) have durable responses with purine nucleoside analogues. In contrast, options are limited for cHCL patients with co-morbidities, purine analogue intolerance, or resistant disease. We report the utility of targeted therapy for nine cHCL patients presenting with treatment naïve cHCL and severe neutropenia and infection (n = 3), purine analogue intolerance (n = 2), or purine analogue resistant disease (n = 4). BRAF inhibitor vemurafenib was started at 240-480 mg twice daily (planned 90-day treatment) and combined with rituximab in seven patients. Therapy was tolerable with no severe adverse events. All patients responded with rapid blood count recovery (median time 1.52 months, range 0.43-4.33). Median progression free and overall survival was not reached at a median follow up of 18.1 months (range 3.2-68.9). These data suggest targeted therapy could be an option for patients unable to be treated with purine analogues.