Encysive Thelin Approval Could Come Days Ahead Of Gilead’s Ambrisentan
This article was originally published in The Pink Sheet Daily
Executive Summary
FDA’s regulatory timeline for reviewing the two pulmonary arterial hypertension medications may fall neck and neck.
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Encysive Pharmaceuticals announced Dec. 28 that FDA has accepted the company's response to a July 24 "approvable" letter for the pulmonary arterial hypertension treatment Thelin (sitaxsentan) as a complete response, setting a June 15 user fee date for reviewing the application. Though the news is positive for Encysive, which has faced several regulatory set backs with Thelin, FDA designated the application a Class 2 resubmission rather than Class 1, giving the application a longer action timeline and potentially putting an approval decision just days ahead of an action date for Gilead's competitive PAH candidate ambrisentan. "A Class 2 designation obviously for some folks will feel like we're not moving forward, but I don't think that's really the case," Encysive CEO Bruce Given maintained during a same-day conference call. "We don't know why it was a Class 2 versus Class 1, but what we do know is that the response is now considered complete, so now it can be formally reviewed and acted upon, and that is important." FDA reviews Class 2 resubmissions within six months, while Class 1 resubmissions are granted a faster review, within two months. According to Given, Encysive has requested a pre-review meeting with FDA to better understand the rationale behind the Class 2 designation. The announcement is one of several set backs in Encysive's bid to win regulatory approval for Thelin in the U.S. The Houston company had the opportunity to gain regulatory clearance well ahead of Gilead's ambrisentan, but has been consistently thwarted by lingering regulatory issues. The company received a second "approvable" letter for the endothelin receptor antagonist July 24 after submitting an existing data set to FDA in May in response to an initial March approvable letter (1 (Also see "Encysive Holds Hope For Thelin Despite Receiving Second “Approvable” Letter" - Pink Sheet, 25 Jul, 2006.)). More recently, Encysive announced Dec. 14 that FDA did not consider its response to the second approvable letter to be complete due to formatting issues, further delaying, though briefly, the regulatory timeline (2 (Also see "Encysive Hits Another Snag With Thelin" - Pink Sheet, 14 Dec, 2006.)). In the meantime, Gilead submitted an NDA Dec. 18 for its endothelin receptor antagonist ambrisentan. The company said it is seeking a six-month priority review, which would give the application a June 18 user fee date. However, if a standard review is granted, the action date would be Oct. 18 (3 (Also see "Gilead Submits NDA For Ambrisentan For PAH" - Pink Sheet, 19 Dec, 2006.)). Encysive had recruited and trained 52 sales reps in preparation for the launch of Thelin in April and maintained the commercial organization despite the delays. The company continues to employ roughly 50 reps, Given said. Of the sales force, he added, "Our goal, as always, is to be prudent in how we manage our resources. We've done our best to do that up until now. We'll continue to do that." Thelin was approved for marketing authorization in the European Union in August (4 (Also see "Encysive’s Thelin Gets EU Nod Ahead Of U.S." - Pink Sheet, 11 Aug, 2006.)). - Jessica Merrill ([email protected]) |