The FDA has expanded the approval of vemurafenib to include the treatment of certain adult patients with Erdheim-Chester disease (ECD), a rare cancer of the blood. Vemurafenib is indicated to treat patients with the BRAF V600 mutation. This is the first FDA-approved treatment for ECD.
"Today's approval of [vemurafenib] for patients with ECD demonstrates how we can apply knowledge of the underlying genetic characteristics of certain malignancies to other cancers," said Richard Pazdur, MD, 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."
ECD is a slow-growing blood cancer that originates in the bone marrow and causes an increased production of histiocytes. Excess histiocytes can result in tumors infiltrating many organs and tissues throughout the body, including the heart, lungs, brain, and others. ECD is estimated to affect 600-700 patients worldwide. Approximately 54 percent of patients with ECD have the BRAF V600 mutation. Patients with ECD have very limited life expectancies.
Vemurafenib is a kinase inhibitor that works by blocking certain enzymes that promote cell growth. The efficacy of vemurafenib for the treatment of ECD was studied in 22 ECD patients who were positive for the BRAF V600 mutation. The trial measured the percent of patients who experienced a complete or partial reduction in tumor size. In the trial, 11 patients (50%) experienced a partial response and one patient (4.5%) experienced a complete response.
Common side effects of vemurafenib in patients with ECD include arthralgia; small, maculopapular rash; alopecia; fatigue; prolonged QT interval; and papilloma. 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 (anaphylaxis and DRESS syndrome), severe skin reactions (Stevens-Johnson syndrome and toxic epidermal necrolysis), QT prolongation, hepatotoxicity, photosensitivity, uveitis, radiation sensitization and radiation recall, kidney failure, Dupuytren's contracture, and plantar fascial fibromatosis.
The FDA granted this application Priority Review and Breakthrough Therapy designations for this indication. Vemurafenib also received Orphan Drug designation for this indication, which provides incentives to assist and encourage the development of drugs for rare diseases.