The U.S. Food and Drug Administration (FDA) expanded the approval of the Roche drug vemurafenib (Zelboraf) to include the treatment of certain adult patients with Erdheim-Chester Disease (ECD), a rare cancer of the blood.

This is the first FDA-approved treatment for the disease.

Zelboraf is indicated to treat patients whose cancer cells have a specific genetic mutation known as BRAF V600. An estimated 600 to 700 patients worldwide have ECD and among them, a little more than half have the BRAF V600 mutation.

A rare cancer of the blood that originates in the bone marrow, ECD causes an increased production of histiocytes, a type of white blood cell. That results in tumors infiltrating many organs and tissues throughout the body, including the heart, lungs, brain and others.

Zelboraf is a kinase inhibitor that works by blocking certain enzymes that promote cell growth. It is currently approved to treat melanoma patients with the BRAF V600 mutation.

The approval was based on findings from the phase 2 VE-BASKET study, which included 22 patients with BRAF-V600-mutation positive ECD. The trial measured the percent of patients who experienced a complete or partial reduction in tumor size. In the trial, half of the patients experienced a partial response and one patient experienced a complete response.

Common side effects of the treatment include joint pain, small, raised bumps, hair loss, fatigue, change in the heart’s electrical activity, and skin growths.

Severe side effects include the development of new cancers (skin cancer, squamous cell carcinoma or other cancers), growth of tumors in patients with BRAF wild-type melanoma, hypersensitivity reactions, severe skin reactions (such as Stevens-Johnson Syndrome and toxic epidermal necrolysis), heart abnormalities, liver damage, photosensitivity, uveitis, kidney failure, immune reactions after receiving radiation treatment, and thickening of tissue in the hands and feet.  

Zelboraf can cause harm to a developing fetus; women should be advised of the potential risk to the fetus and to use effective contraception.

“Today’s approval of Zelboraf for patients with ECD demonstrates how we can apply knowledge of the underlying genetic characteristics of certain malignancies to other cancers,” said Richard Pazdur, M.D., director of the FDA’s Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research. “This product was first approved in 2011 to treat certain patients with melanoma that harbor the BRAF V600E mutation, and we are now bringing the therapy to patients with a rare cancer with no approved therapies.”