Mekinist: Glaxo's drug is half of a hopeful melanoma combo

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Mekinist
Project name: trametinib
Disease: Melanoma
Peak sales estimate: $350 million
Approved: May 23
Company: GlaxoSmithKline

The Scoop: 
Mekinist was approved in May alongside GlaxoSmithKline's ($GSK) other melanoma therapy Tafinlar, but the two are for now intended as separate products. London-based Glaxo has high hopes for Mekinist and has already launched its own in-house trials with its BRAF blocker Tafinlar to test a combination approach. The drug giant has shown that attaching an MEK blocker could improve treatment for melanoma patients. Together, Mekinist and Tafinlar are expected to pack a better punch by providing a more effective and sustained effect against melanoma, which is the leading cause of death from skin disease. The NIH's National Cancer Institute estimated that 76,690 Americans would be diagnosed with melanoma and 9,480 would die from the disease in 2013.

Mekinist, a MEK inhibitor, was approved to treat patients whose tumors express the BRAF V600E or V600K gene mutations. About half of all melanoma patients have a BRAF mutation. In metastatic melanoma, BRAF V600E mutations make up about 85% of all BRAF V600 mutations while V600K mutations account for about 10%.

"MEK has been pursued as a therapeutic target in cancer for more than a decade," said Dr. Keith Flaherty, director of developmental therapeutics at Massachusetts General Hospital Cancer Center and a principal investigator of Glaxo's Phase III METRIC trial, in a statement. "Based on the clear improvement versus chemotherapy in progression-free survival, trametinib represents the first validated MEK inhibitor. We welcome it as a new treatment option for patients with this disease."

In the Phase II METRIC trial, 322 patients with metastatic or unresectable melanoma with the BRAF V600E or V600K gene mutation were randomly assigned to receive either Mekinist or a standard chemotherapy drug. Unresectable melanomas are those that cannot be removed by surgery. Tumor growth in patients receiving Mekinist was delayed by 3.3 months compared to those on chemotherapy. Mekinist did not seem to have a beneficial effect on patients who had previously used Tafinlar or other BRAF inhibitors.

In November, Glaxo and Pfizer ($PFE) struck a deal to combine their cancer drugs and assess their impact in patients with BRAFV600 wild-type melanoma, including NRAS mutations. In an early-stage dose-escalation study, patients will be given a combo therapy of Pfizer's blockbuster candidate palbociclib and Glaxo's Mekinist. GlaxoSmithKline is heading up the upcoming Phase I/II study, but the companies have yet to release any financial details of their joint venture.

In the U.S., Mekinist will cost $8,700 for a 30-day supply, and some investors project that both Mekinist and Tafinlar could bring in $350 million each in potential peak sales. That revenue could help boost Glaxo's newer oncology portfolio, not to mention help Glaxo deliver on its growth promises as the company anticipates new generic rivals for its blockbuster respiratory treatment Advair. -- Emily Mullin (email | Twitter)

For more:
Pfizer, GlaxoSmithKline forge cancer alliance in combo melanoma trial pact
GlaxoSmithKline gains FDA OK on two genetically targeted melanoma drugs
GlaxoSmithKline shoots for combo attack against melanoma in surgery patients

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