Encysive Pharmaceuticals has relied on existing data to address lingering FDA concerns regarding the pulmonary arterial hypertension drug Thelin (sitaxsentan), the company said May 25, following discussions with the agency.

FDA had requested additional clinical trial results in a March 24 "approvable" letter (¹ Also see "FDA Requests Additional Thelin Study In “Approvable” Letter" - Pink Sheet, 27 March, 2006.).

"Encysive and the FDA have come to the mutual agreement that the company's approach to responding to the items outlined in the approvable letter with our existing data set is reasonable, making possible the submission of a complete response," Encysive said in a statement.

The company said it expects to hear back from the agency within 30 days.

As part of its May 2005 NDA submission, Encysive provided data from its STRIDE-2 pivotal trial. Conducted under a special protocol assessment, the trial compared Thelin with Actelion's Tracleer (bosentan), also an endothelin receptor agonist.

Results of the 226-patient trial showed that Thelin increased a six-minute walk test by 31.4 m over placebo; in comparison, Tracleer performance was measured as a 29.5 m improvement.

Despite the modest efficacy difference, Encysive hopes to differentiate Thelin from Tracleer in safety; sitaxsentan was shown to have a lower rate of liver abnormalities compared to bosentan, the firm said. The company is in the midst of conducting a long-term safety study, STRIDE 3.

Encysive is also working on a follow-on to sitaxsentan. TBC3711 is in Phase I, though the program has been on clinical hold since March due to unanticipated pre-clinical findings (² Also see "Encysive TBC3711 On Clinical Hold" - Pink Sheet, 24 March, 2006.).

- Jonathan Block

Encysive Avoids Additional Trials For Thelin NDA

More from Archive

More from Pink Sheet