SILVER SPRING, Md., Oct. 23, 2012 /PRNewswire/ -- United Therapeutics Corporation (NASDAQ: UTHR) announced today that it received a complete response letter from the United States Food and Drug Administration (FDA) declining to approve its new drug application (NDA) for treprostinil diethanolamine extended release tablets (oral treprostinil) for the treatment of pulmonary arterial hypertension (PAH). The FDA letter questioned the clinical importance of the 6 Minute Walk Distance (6MWD) effect size shown in the FREEDOM-M study, the inability to demonstrate an improvement in time to clinical worsening in all three Phase III studies of oral treprostinil, and the inability to demonstrate a statistically significant effect on 6MWD in the two FREEDOM-C studies as reasons for being unable to approve the NDA in its current form. The FDA noted that it was unsure whether an additional clinical study could alter these impressions, but if United Therapeutics did undertake an additional study it should consider, among other things, a fixed dose design and more frequent dosing. "We will continue using our best efforts to gain approval of oral treprostinil, and we will focus on doing so within the next four years," said Martine Rothblatt, Ph.D., Chairman and Chief Executive Officer of United Therapeutics. "We will convene with our experts over the next several weeks to decide which of several paths forward to pursue." Conference Call Today On Tuesday, October 23, 2012 at 4:45 p.m. Eastern Time, United Therapeutics will host a conference call to answer questions related to the FDA's complete response letter. The conference call is accessible by dialing 1-877-351-5881, with international callers dialing 1-970-315-0533. A rebroadcast of the conference call will be available for two weeks and can be accessed by dialing 1-855-859-2056, with international callers dialing 1-404-537-3406, and using conference code: 56801607.