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Treatment for Pulmonary Arterial Hypertension (PAH)

Encysive Pharmaceuticals Files Request for Formal Dispute Resolution With U.S. FDA to Contest Third Approvable Letter for Thelin

Company Seeks Re-evaluation of Its Application for Thelin (Sitaxsentan Sodium)

HOUSTON, Aug 6, 2007 (PrimeNewswire via COMTEX News Network) -- Encysive Pharmaceuticals Inc. today announced that it has filed with the U.S. Food and Drug Administration (FDA) a request for formal dispute resolution to contest the third approvable letter that the Company received for its New Drug Application (NDA) for Thelin. The Company originally submitted an NDA for Thelin to treat pulmonary arterial hypertension (PAH) in 2005. On June 15, 2007, the Company received a third approvable letter from the FDA stating that Encysive's clinical development program for Thelin did not demonstrate the evidence of efficacy needed for approval. Formal dispute resolution is an FDA process where sponsors can challenge regulatory decisions by bringing the dispute to the attention of FDA supervisors.

In preparing the formal dispute resolution submission, the Company assembled a team of outside and internal professionals to review the FDA's rationale for withholding approval and to review the Company's statistical analysis plan for STRIDE-2.

In general, the disagreement between the Company and the FDA involves the imputation of values for STRIDE-2 patients with clinical worsening and patients who left the trial for various reasons, some of whom had 6-minute walk tests performed after discontinuing Thelin treatment. Encysive's analytical approach was to include a walk value if one existed, but to exclude values that were obtained beyond a reasonable amount of time after discontinuation from the trial and therapy. The Company believes that this approach was reasonable, as it was established prior to unblinding and treats active drug and placebo patients exactly the same. The FDA's analytical approach was to assign, in the Company's view, an overly conservative walk value in these situations, which in some cases appeared to treat active drug and placebo patients differently.

"We continue to believe that we have fully complied with the design of our study as submitted and amended within the terms of FDA's guidelines," said George Cole, President and CEO of Encysive Pharmaceuticals. "In addition, we believe our statistical approach was reasonable and fair, and this position has been supported by the outside statistical expert we consulted."

If formal dispute resolution is unsuccessful, the Company will be required to conduct an additional pivotal trial to obtain additional clinical data. Such a trial would be costly and could take two years to complete.

About Formal Dispute Resolution

Formal dispute resolution is a mechanism included in FDA guidance documents enabling reviews of any Agency decision by raising the matter with supervisors of the employee making the decision. This process can continue through the chain of command at the Center for Drug Evaluation and Research, and sets the stage for appealing to the Commissioner. FDA guidance stipulates that they respond within 30 days. A copy of the guidance is available at

About Encysive Pharmaceuticals

Encysive Pharmaceuticals Inc. is a global biopharmaceutical company engaged in the discovery, development and commercialization of novel, synthetic, small molecule compounds to address unmet medical needs. Our research and development programs are predominantly focused on the treatment and prevention of interrelated diseases of the vascular endothelium and exploit our expertise in the area of the intravascular inflammatory process, referred to as the inflammatory cascade, and vascular diseases.

This press release contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These forward-looking statements are subject to certain risks, trends and uncertainties that could cause actual results to differ materially from those projected. Among those risks, trends and uncertainties are: the unpredictability of the FDA formal dispute resolution process; unexpected delays in regulatory review and approval of Thelin by the FDA in the U.S. and our other products under development; our estimate of the sufficiency of our existing capital resources; our ability to raise additional capital to fund cash requirements for future clinical trials; our ability to successfully conduct a Thelin pivotal trial; the availability of sufficient funds to commercialize Thelin in the U.S. should it be approved by the FDA, as well as more specific risks, trends and uncertainties facing Encysive such as those set forth in its reports on Forms 8-K, 10-Q and 10-K filed with the U.S. Securities and Exchange Commission. Given these risks, trends and uncertainties, any or all of these forward-looking statements may prove to be incorrect. Therefore you should not rely on any such forward-looking statements. Furthermore, Encysive undertakes no duty to update or revise these forward-looking statements. The Private Securities Litigation Reform Act of 1995 permits this discussion.

This news release was distributed by PrimeNewswire,

SOURCE: Encysive Pharmaceuticals Inc.

Encysive Pharmaceuticals Inc.
Ann Tanabe, VP, Investor Relations and
Corporate Communications
(713) 796-8822

The Trout Group
Marcy Strickler
(646) 378-2927

BMC Communications
Dan Budwick
(212) 477-9007 ext. 14

Posted: August 2007

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