FDA turbocharges GlaxoSmithKline's bids for new cancer drug uses

With two back-to-back decisions, the FDA is revving up GlaxoSmithKline's ($GSK) cancer prospects. Friday, the agency dubbed Arzerra a "breakthrough therapy," a coveted designation that puts the leukemia drug into the fast lane for first-line use. And today, the FDA put GSK's new melanoma duo, Tafinlar and Mekinist, on its priority review track as a combination cocktail. 

Developed with Genmab, Arzerra is not a big seller; it brought in less than $100 million last year. But the breakthrough designation gives it a chance to do much better. The drug is now approved for chronic lymphocytic leukemia patients whose disease has progressed despite previous therapy. As a second-line therapy, it hasn't gained much traction. The new indication would put Arzerra on the front line in certain cases--when patients aren't eligible for fludarabine-based treatment--giving it access to a broader market.

The breakthrough designation speeds up the approval process for drugs with potential for serious and life-threatening diseases. CLL is the most common form of leukemia in adults, and GSK estimates there will be more than 15,680 new cases and more than 4,580 deaths in the U.S. this year. Glaxo licensed the drug three years ago in a $2.1 billion deal.

Priority review isn't as dramatic as the FDA's breakthrough status, but it still will accelerate Tafinlar and Mekinist's trip through the process. Approved separately in May for melanoma patients with BRAF mutations, the drugs target the tumors in different ways: Tafinlar is a BRAF inhibitor designed to attack tumors with the V600E mutation; Mekinist is an MEK inhibitor aimed at V600E and V600K mutations. Glaxo wants approval to put the two together for a combination punch.

The idea is that the cocktail would fend off cancer longer and better than either drug alone. BRAF drugs--including a rival product from Roche, Zelboraf--work quite well, but tumors tend to grow resistant to them. With an MEK inhibitor in the mix, resistance might not develop as quickly.

The FDA will say yea or nay to the combinations in early January, in two separate decisions, one for adding Tafinlar to Mekinist and the other for Mekinist in addition to Tafinlar. Both apps are based on Phase I/II data comparing the two-drug combo with Tafinlar alone, GSK said.

Glaxo is counting on 6 new drugs--including Tafinlar and Mekinist--to help keep its growth promises. CEO Andrew Witty has been assuring investors that the company is on the verge of better days, even as it anticipates new generic rivals for its blockbuster respiratory treatment Advair. Besides the two skin cancer drugs, Glaxo has won FDA approval for the lung drug Breo Ellipta and an FDA advisory panel's backing for another Advair follow-up, Anoro. Its ViiV Healthcare joint venture nabbed approval for a potential blockbuster HIV drug, Tivicay.

- here's the Arzerra announcement
- and here's the Tafinlar/Mekinist press release

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