FDA nod for melanoma combo cranks up GlaxoSmithKline's cancer franchise

GlaxoSmithKline ($GSK) wanted a dynamic-duo designation for its two new melanoma drugs, Tafinlar and Mekinist. And now, the FDA has come through. The agency approved the two targeted treatments for use in tandem, in patients with particular genetic mutations.

Both drugs are already approved to treat melanoma, but because the drugs work in different ways, the combination therapy could be more effective and long-lasting. Tafinlar works by inhibiting the action of a mutated BRAF gene, while Mekinist inhibits cancer cell growth by interfering with a key protein known as MEK.

GSK is counting on Tafinlar and Mekinist to help rev up sales after some disappointing patent-cliff years. The company has pegged its hopes to 9 new drugs and is promising that 2013 results would mark its return to growth. Analysts have predicted Tafinlar sales at $279 million by 2016 and Mekinist at $343 million.

BRAF drugs--including a rival product from Roche ($RHHBY), Zelboraf--work quite well, but tumors tend to grow resistant to them. With a MEK inhibitor in the mix, resistance might not develop as quickly. Both drugs are only approved to treat patients with BRAF gene mutations.

Approved under the FDA's priority review program, the Tafinlar-Mekinist combination delivered a 76% response rate in a Phase II study, compared with 54% of patients treated with Tafinlar alone. The median duration of response for the combination therapy was 10.5 months, compared with 5.6 months for Tafinlar solo. The approval is contingent on the results of a Phase III trial already in progress. And so far, the combination is only approved for patients with inoperable melanoma or those whose cancer has spread.

Suitable patients have to be identified with a BRAF diagnostic test. Glaxo teamed up with the French company bioMérieux to develop a test, which was approved by FDA along with the two drugs. Roche, which sells its own treatment for BRAF-positive melanoma, Zelboraf, also sells its own FDA-approved diagnostic test for the mutation.

- read the GSK release

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