Kalydeco in R117H patients? As AdComm nears, Vertex drug faces doubts

Vertex' ($VRTX) orphan drug Kalydeco boasts a comparatively small patient pool that the drugmaker is trying to swell, with an eye on adding cystic fibrosis patients with the R117H mutation. But first, it'll have to get the FDA's OK, and new briefing documents suggest the agency still has some doubts.

U.S. regulators Friday released the documents in preparation for an advisory committee meeting next week, and according to an investor note from ISI Group analyst Mark Schonebaum, they "question whether there is enough sufficient evidence for approval."

The issue: R117H mutation "results in a functionally different chloride channel than with the G551D mutation"--Kalydeco's original indication, Schoenebaum wrote. In a trial to examine R117H--requested by the FDA--Kalydeco missed its primary endpoint. But Vertex has said it believes there's hope for the drug in that population, potentially in a subpopulation of patients, like those over 18 years old.

For perspective, the R117H patient pool is small--there are only an estimated 1,110 patients worldwide with the mutation, compared with the G551D group of 2,700, Schoenebaum noted. But with about a third of those R117H patients living in the U.S., where Kalydeco's price tag sits at $300,000, sales can add up quickly.

Vertex CEO Jeffrey Leiden

Kalydeco could also use some more room to grow. In January,company CEO Jeffrey Leiden said Vertex was already reaching nearly all of the eligible G551D patients age 6 and older in the U.S. and Europe. It has gotten some of that since then, though, in February snagging an FDA thumbs-up for 8 additional mutations and in August adding the same nod in Europe. Combined, those moves gave the drug the green light to treat 400 more CF sufferers.

Special Reports: Top 15 Drug Launch Superstars - Kalydeco - Vertex Pharmaceuticals | Top 20 orphan drugs by 2018 - Kalydeco

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