Encysive Pharmaceuticals has completed the submission of a New Drug Application (NDA) with the US FDA for Thelin (sitaxsentan) 100 mg as a once daily oral treatment for patients with pulmonary arterial hypertension (PAH).

According to the company release, the NDA contains the largest database ever assembled in a regulatory filing for PAH, with approximately 900 PAH patients receiving Thelin in clinical evaluations.

The Company conducted two randomized, placebo- controlled pivotal Phase III studies in support of worldwide product registrations. The second pivotal Phase III trial, STRIDE-2, was conducted under a Special Protocol Assessment with the FDA and met its primary objective of improved six-minute walk (6MW), with a statistically significant increase of 31.4 meters over placebo.

Also in STRIDE-2, Thelin demonstrated a potential advantage in safety. The 100 mg dose of Thelin was associated with a 3% rate of liver function abnormality (elevation in liver enzymes to levels >3 times the upper limit of normal) in the 18-week study, compared to 6% for placebo and 11% for bosentan (Tracleer), the only currently approved oral therapy for PAH.

Thelin is a small molecule that blocks the action of endothelin, a potent mediator of blood vessel constriction and growth of smooth muscle in vascular walls.

Pulmonary arterial hypertension (PAH) is a condition that involves high blood pressure and structural changes in the walls of the pulmonary arteries, which are the blood vessels that connect the right side of the heart to the lungs. PAH causes shortness of breath, limits activity, and is eventually fatal unless treated successfully with heart/lung or lung transplantation.