Two new GlaxoSmithKline (GSK) drugs, Tafinlar (dabrafenib) and Mekinist (trametinib), have been approved for the treatment of patients with advanced melanoma by the U.S. Food and Drug Administration (FDA).

Melanoma is the most dangerous form of skin cancer and the number one cause of death from skin disease. According to the National Cancer Institute, about 76,690 people will be diagnosed with melanoma in the U.S. in 2013, and about 9,480 will die from the disease.

Patients with melanoma whose tumors express the BRAF V600E gene mutation can now take the approved drug Tafinlar, a BRAF inhibitor, while patients whose tumors express the BRAF V600E or V600K gene mutations can take Mekinist, a MEK inhibitor.

Experts estimate that 50% of melanomas appearing in the skin have a BRAF gene mutation. The FDA approved these two drugs as single agents, not as a combination treatment.

A genetic test, known as he THxID BRAF test, was also approved by the Agency. The test is a companion diagnostic that will determine whether a person’s melanoma cells have the V600E or V600K mutation in the BRAF gene.

Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research, said:

“Advancements in our understanding of the biological pathways of a disease have allowed for the development of Tafinlar and Mekinist, the third and fourth drugs the FDA has approved for treating metastatic melanoma in the past two years.”

In 2011, Zelboraf (vemurafenib) and Yervoy (ipilimumab) were approved by the FDA to treat metastatic or unresectable melanoma – a tumor that is unable to be removed by surgery.

Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostic Devices and Radiological Health in the FDA’s Center for Devices and Radiological Health, said:

“The co-approval of Tafinlar and Mekinist and the second companion diagnostic for BRAF mutation detection demonstrates the commitment of pharmaceutical and diagnostic partners to develop products that detect and target the molecular drivers of cancer.”

The approval of the THxID BRAF test is based on data from clinical trials that support the approval of Tafinlar and Mekinist, the experts said. In order to test for the mutation, samples of patients’ melanoma tissue were taken.

Tafinlar was analyzed in 250 patients with BRAF V600E gene mutation-positive metastatic or unresectable melanoma. Participants were randomly assigned to two groups: one group received Tafinlar and the other received dacarbazine, a chemotherapy drug.

Results showed that patients who received Tafinlar had a delay in tumor growth that was 2.4 months later than those taking dacarbazine.

The most severe side effects reported in patients taking Tafinlar included a raised risk of skin cancer (cutaneous squamous cell carcinoma), fevers that may be complicated by low blood pressure, dehydration, kidney failure, severe rigors (shaking chills), and elevated blood sugar levels that call for changes in diabetes medication or the need to begin taking drugs to control diabetes.

The most common side effects in patients taking Tafinlar included:

  • headache
  • joint pain
  • hyperkeratosis (thickening of the skin)
  • ferver
  • hand-foot syndrome
  • hair lossnon-cancerous skin tumors

Mekinist was examined in 322 individuals with metastatic or unresectable melanoma with the BRAF V600E or V600K gene mutation. The participants were randomly assigned to receive either Mekinist or chemotherapy.

The scientists found that patients taking Mekinist had a delay in tumor growth that was 3.3 months later than those undergoing chemotherapy.

However, people who took Tafinlar or other inhibitors of BRAF in the past did not seem to benefit from Mekinist.

The most severe side effects reported in patients taking Mekinist included skin infections, loss of vision, lung inflammation, and heart failure.

The most ommon side effects in patients receiving Mekinist included:

The experts noted that women of child bearing age should be warned that Tafinlar and Mekinist have the potential to cause fetal harm. Men and women should also be aware that these drugs could cause infertility.

A recent report described simple steps people can take this summer that can help them prevent skin cancer, the most common cancer in the U.S.

Written by Sarah Glynn