FDA team applauds telaprevir's efficacy, raises safety concerns

Vertex ($VRTX) has taken one more step forward in its long journey to an expected approval for its hep C blockbuster telaprevir. In an FDA staff review of the drug--slated to run the gauntlet of an FDA expert panel on Thursday--regulators confirmed the impressive efficacy data Vertex collected in Phase III, but raised a red flag on two well-known safety issues: the skin reactions and anemia triggered in patients.

"Overall, the FDA review team's independent analyses confirmed the Applicant's primary efficacy findings and many secondary endpoint analyses for all pivotal clinical trials," stated the agency's briefing documents, released late this morning.

Among the agency's key findings, the FDA review confirmed overall cure rates of 73 percent and 79 percent at weeks eight and twelve in one of its clinical trials, compared to 46 percent in the control arm. That's even better than the 75 percent cure rate that the company had reported. Vertex also scored points with its plans to provide a shortened treatment period to help ameliorate side effects when appropriate, a development the FDA calls "an evolution in HCV treatment."

"However," staff also noted, "between Weeks 8 and 12 additional events of anemia and rash occurred in the (second telaprevir study) group."

"Specifically, the risks of telaprevir use are associated with two key toxicities: skin reactions (rash and pruritus) and anemia, events that were common, sometimes severe, and in some cases treatment-limiting. Other events of interest include ano-rectal disorders and hyperuricemia."

The FDA panel is almost certain to steer their questions along these lines, with a clear case on efficacy to consider as they balance out concerns on the cases of rash and anemia. Their review will come a day after Merck makes its case for boceprevir to the same group. In most cases, analysts have given Vertex the edge on impact. But hep C specialists appear eager to have both treatments to consider for patients, each of which appears to represent a major improvement over the standards now in use.

Shares of Vertex surged soon after the FDA documents hit, indicating some significant relief over the agency's handling of the safety data along with an appreciation of the drug's efficacy data.

- here is the FDA review