GlaxoSmithKline hit the proverbial trifecta yesterday, as FDA approved two of its melanoma drug candidates, Tafinlar (dabrafenib) and Mekinist (trametinib), as well as a companion diagnostic designed to detect the gene mutations expressed by the tumors each treatment is designed to fight.

Both drugs are oral therapies approved for one indication, metastatic or unresectable melanoma in adult patients with the BRAF V600E mutation, which accounts for about 85% of all BRAF V600 mutations in metastatic melanoma, according to a study published last year in Clinical Cancer Research. Mekinist, a MEK inhinitor, is additionally approved for adults with the BRAF V600K mutation, accounting for another 10% of BRAF V600 mutations.

However, Mekinist is not indicated for patients who have received a prior BRAF inhibitor therapy, while Tafinlar, a BRAF inhibitor, is not indicated for patients with wild-type BRAF melanoma.

“GSK can now offer two new single-agent therapies to selected patients who have metastatic melanoma, a devastating disease with very low survival rates and few treatment options,” Paolo Paoletti, M.D., president of GlaxoSmithKline Oncology, said in a statement.

GSK said Tafinlar and Mekinist will be available for prescription by early third quarter of this year.

Tafinlar and Mekinist are the third and fourth drugs approved in the past two years by FDA for metastatic or unresectable melanoma, with the earlier two treatments being Zelboraf (vemurafenib) and Yervoy (ipilimumab), both approved in 2011. Last year, Bristol-Myers Squibb generated $706 million in worldwide sales from Yervoy, compared with the CHF 234 million ($245.4 million) Roche racked up from Zelboraf.

The agency approved the drugs as well as the diagnostic THxID™-BRAF, developed by bioMérieux through a collaboration with GSK that began in 2010, based on data from clinical studies that supported the Tafinlar and Mekinist approvals.

Tafinlar was approved following Phase III clinical data showing a near doubling of the primary endpoint of progression-free survival—a median of 5.1 months compared to 2.7 months with dacarbazine—in the open-label BREAK-3 study. A total 250 previously untreated adult patients with BRAF V600E mutation-positive unresectable or metastatic melanoma were randomized to either drug.

Mekinist was approved after Phase III data showed a statistically significant increase in PFS, to a median 4.8 months compared with 1.5 months for chemotherapy. The open-label international METRIC study randomized to either treatment 322 unresectable or metastatic melanoma adult patients with a BRAF V600E or V600K mutation, who had no more than one prior chemotherapy regimen for advanced or metastatic disease and no prior BRAF or MEK inhibitor treatment.

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