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FDA Approves Two Drugs, Companion Diagnostic Test for Advanced Skin Cancer

Dabrafenib and trametinib target tumors with BRAF gene mutations (May 29)

The FDA has approved two new drugs, Tafinlar (dabrafenib) and Mekinist (trametinib), for patients with metastatic or unresectable melanoma, the most dangerous type of skin cancer. Both agents are marketed by GlaxoSmithKline.

Tafinlar, a BRAF inhibitor, is approved to treat patients with melanoma whose tumors express the BRAF V600E gene mutation. Mekinist, a MEK inhibitor, is approved to treat patients whose tumors express the BRAF V600E or V600K gene mutations. Approximately half of melanomas arising in the skin have a BRAF gene mutation. Tafinlar and Mekinist were approved as single agents, not as a combination treatment.

The FDA approved Tafinlar and Mekinist with a genetic test called the THxID BRAF test, a companion diagnostic that will help determine whether a patient’s melanoma cells have the V600E or V600K mutation in the BRAF gene. The test is manufactured by bioMérieux of Grenoble, France.

Zelboraf (vemurafenib; Genentech) and Yervoy (ipilimumab; Bristol Myers-Squibb) were approved in 2011 for the treatment of metastatic or unresectable melanoma.

The FDA’s approval of the THxID BRAF test is based on data from clinical studies that support the Tafinlar and Mekinist approvals. Samples of patients’ melanoma tissue were collected to test for the mutation.

Tafinlar was studied in 250 patients with BRAF V600E gene mutation-positive metastatic or unresectable melanoma. Patients were randomly assigned to receive Tafinlar or the chemotherapy drug dacarbazine. Patients who took Tafinlar had a delay in tumor growth that was 2.4 months later than those receiving dacarbazine.

The most serious side effects reported in patients receiving Tafinlar included an increased risk of cutaneous squamous-cell carcinoma, fevers that may be complicated by hypotension, severe rigors, dehydration, kidney failure, and increased blood sugar levels requiring changes in diabetes medication or the need to start medicines to control diabetes.

The most common side effects reported in patients receiving Tafinlar included hyperkeratosis, headache, fever, joint pain, noncancerous skin tumors, hair loss, and hand–foot syndrome.

Mekinist was studied in 322 patients with metastatic or unresectable melanoma with the BRAF V600E or V600K gene mutation. Patients were randomly assigned to receive either Mekinist or chemotherapy. Patients receiving Mekinist had a delay in tumor growth that was 3.3 months later than that of patients receiving chemotherapy. Patients who previously used Tafinlar or other inhibitors of BRAF did not appear to benefit from Mekinist.

The most serious side effects reported in patients receiving Mekinist included heart failure, lung inflammation, skin infections, and loss of vision. Common side effects included rash, diarrhea, peripheral edema, and skin breakouts that resembled acne.

Source: FDA; May 29, 2013.

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