Among patients with relapsed or refractory hairy cell leukemia (HCL), vemurafenib monotherapy retreatment appears to be both safe and effective, and may improve long-term clinical outcomes, according to research published in Blood.

Although purine nucleoside analog treatment can induce high response rates in patients with HCL, some patients relapse or have refractory disease, and in these cases — which may be as frequent as 40% — novel treatments are needed.

Given the importance of BRAFV600E mutations in HCL etiology, researchers previously evaluated whether vemurafenib, a BRAF inhibitor, is safe and effective among patients with relapsed or refractory HCL. For this study, researchers evaluated long-term clinical outcomes in this patient population.

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Overall, 36 patients were enrolled and treated on this trial. The median patient age was 59 years, 83% of patients were male gender, the median number of prior therapy lines was 3, and 17% of patients had had a prior splenectomy.

The median follow-up for the study was 40 months. At this point, the best overall response rate was 86%, with 33% of patients reaching a complete response and 53% of patients reaching a partial response. Of the 31 patients who responded, 68% had a relapse; the median relapse-free survival was 19 months.

Of the 21 patients who relapsed, 14 (67%) received vemurafenib retreatment; a complete hematologic response was noted in 86% of these patients. However, of the 12 patients who responded to vemurafenib retreatment, 50% had a second relapse. Additionally, 2 patients developed KRAS and CDKN2A mutations, which were linked with drug resistance.

At 4 years, the overall survival rate was 82%; patients who relapsed within the initial year of vemurafenib treatment had worse overall survival. There were 2 grade 3 events noted, rash and fever/pneumonia, each occurring in 1 patient.

“Remission durations are shorter with each subsequent relapse, and a combination with anti-CD20 antibodies may shorten the duration of vemurafenib treatment and prolong remission durations in [relapsed/refractory] HCL,” the authors wrote in their report.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 


Handa S, Lee JO, Derkach A, et al. Long-term outcomes in patients with relapsed or refractory hairy cell leukemia treated with vemurafenib monotherapy. Blood. 2022;140(25):2663-2671. doi:10.1182/blood.2022016183