Low doses of the BRAF inhibitor vemurafenib are highly effective in patients with refractory hairy cell leukemia, a study published in the journal Blood has shown.1

The activating mutation BRAF V600E, which is often found in melanomas, is the key driver mutation in hairy cell leukemia, a rare type of leukemia that is typically classified as a subtype of chronic lymphocytic leukemia (CLL). Therefore, researchers sought to analyze the course of 21 patients with hairy cell leukemia who were treated with the BRAF inhibitor.

Patients were treated with vemurafenib at doses ranging from 240 mg/day to 1920 mg/day for a median duration of 90 days. These patients were not participants of a clinical trial.

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Results showed that vemurafenib treatment improved blood counts in all patients. Platelets, neutrophils, and hemoglobin recovered within a median of 28, 43, and 55 days, respectively.

Researchers found that 40% of the 15 evaluable patients achieved complete remission and the median event-free survival was 17 months.

The study also demonstrated that abrogation of BRAF V600E by vemurafenib-induced ERK phosphorylation was consistently observed with 240 mg of vemurafenib twice daily.

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In terms of safety, typical adverse events associated with vemurafenib treatment were reported with low-dose regimens as well.

“We provide evidence that anti-tumor and side effects are observed with 480 mg vemurafenib, suggesting that dosing regimens in BRAF driven cancers could warrant reassessment in trials with implications for cost of cancer care,” the authors concluded.


  1. Dietrich S, Pircher A, Endris V, et al. BRAF inhibition in hairy cell leukemia with low dose vemurafenib [published online ahead of print March 3, 2016]. Blood. doi: 10.1182/blood-2015-11-680074.