A short course of vemurafenib, an oral BRAF inhibitor, was highly effective in patients with relapsed or refractory hairy-cell leukemia, a rare form of lymphocytic leukemia that shares some features with chronic lymphocytic leukemia (CLL), a new study published in The New England Journal of Medicine has shown.1

Because BRAF V600E is the underlying genetic mutation that drives hairy-cell leukemia, researchers sought to evaluate the activity and safety of vemurafenib in patients with relapsed or refractory disease by conducting 2 phase 2 studies, one in the United States and another in Italy.

For the studies, researchers enrolled 28 patients with hairy-cell leukemia that had relapsed after treatment with a purine analogue or who had disease that was refractory to purine analogues in the Italian trial and 26 of 36 planned patients in the US trial.

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All patients received vemurafenib 960 mg orally twice daily for a median of 16 weeks in the Italian study and 18 weeks in the US trial.

Results showed that the overall response rates were 96% and 100% among evaluable patients after a median of 8 weeks and 12 weeks in the Italian trial and the US trial, respectively.

Researchers found that 35% and 42% of patients in the Italian trial and the US trial, respectively, achieved a complete response. One-year progression free survival rate was 73% and 1-year overall survival rate was 91% in the US study.

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In regard to safety, the most common vemurafenib-associated adverse events leading to dose reductions with rash and arthralgia, but most side effects were grade 1 or 2.

The study also demonstrated that bypass reactivation of MEK and ERK may be a resistance mechanism for vemurafenib in this patient population.


  1. Tiacci E, Park JH, De Carolis L, et al. Targeting mutant BRAF in relapsed or refractory hairy-cell leukemia. N Engl J Med. 2015; 373(18):1733-1747.