The medication Zelboraf® (vemurafenib) appears active in the treatment of hairy cell leukemia (HCL) that had progressed after previous therapy. These findings were published in New England Journal of Medicine.
Hairy cell leukemia is a rare type of leukemia, or cancer of the immune cells. In HCL, the bone marrow makes too many lymphocytes (a type of white blood cell). The disease is called hairy cell leukemia because the leukemia cells look “hairy” when viewed under a microscope. It tends to be a slow-growing type of leukemia and is generally treated with chemotherapy.
A mutation in a gene known as BRAF plays a role in the growth of some cancers, including HCL. Drugs that target BRAF mutations (BRAF inhibitors) can stop or control the growth of HCL.
Researchers recently conducted a study to evaluate the safety and efficacy of an oral BRAF inhibitor called Zelboraf® (vemurafenib). Specifically, they tested the drug in patients with HCL that had come back or not responded to treatment with drugs known as purine analogues, which interfere with the division and growth of cancer cells.
The trial consisted of two studies—one in Italy (28 patients) and one in the United States (26 patients). Both studies used a 960 mg dose of Zelboraf given twice daily. Patients in Italy received treatment for 18 weeks, and patients in the United States for 16 weeks.
In the Italian study, 96% of patients had a response to Zelboraf (this included partial and complete responses) after eight weeks of treatment. In the U.S. study, 100% of patients had a response after 12 weeks. Rates of complete response (the disappearance of all signs of cancer) were 35% among Italian patients and 42% among U.S. patients.
At a 23-month follow-up, the researchers found that patients in the Italian trial with a complete response had a median relapse-free survival of 19 months, and those with a partial response had a median relapse-free survival of six months. In the U.S. trial, patients with a complete response survived for a median of 25 months without additional treatment, and those with a partial response had a median treatment-free survival of 18 months.
One year after completing treatment, 73% of patients in the U.S. study were alive without disease progression. Overall survival for these patients was 91% at one year.
Side effects in both studies were, in general, not severe. Some patients had to receive a reduced dose of Zelboraf due to joint pain and arthritis. A portion of patients (7 out of 50) also developed tumors beneath their skin, which were removed with a simple procedure.
Based on the favorable survival outcomes in these studies, the researchers concluded that Zelboraf appears to be an effective treatment option for patients with HCL that has come back after or has not responded to previous treatment. In addition, the side effects appeared manageable.
Reference: Tiacci E, Park JH, De Carolis L, et al. Targeting Mutant BRAF in Relapsed or Refractory Hairy-Cell Leukemia. New England Journal of Medicine [early online publication]. September 9, 2015.
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