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Clinical Studies of OvaRex in Advanced Ovarian Cancer Fail to Meet Primary Endpoint

SILVER SPRING, Md. and WELLESLEY HILLS, Mass., Dec 05, 2007 /PRNewswire- FirstCall via COMTEX News Network/ -- United Therapeutics Corporation (Nasdaq: UTHR) and its wholly- owned subsidiary, Unither Pharmaceuticals, Inc., announced today the completion of their two pivotal trials of OvaRex(R) MAb for the treatment of advanced ovarian cancer. Preliminary analysis demonstrates that the studies failed to reach statistical significance.

The identical studies, known as IMPACT I and II (IMunotherapy Pivotal ovArian Cancer Trial), were randomized, double-blind, placebo-controlled trials conducted at over 60 centers across the United States. The studies enrolled 367 ovarian cancer patients and assessed the efficacy of OvaRex mono- immunotherapy during the so-called "watchful waiting" period following front- line carboplatin-paclitaxel based chemotherapy. The program sought to confirm data observed in a subset analysis of a prior randomized phase II study, which suggested the potential of OvaRex to extend the time to disease relapse among patients who had successfully completed front-line therapy. The studies were well balanced in terms of patient demographics and the safety profile was similar between active and control populations. The studies demonstrated no difference between active (standard of care followed by OvaRex) and control (standard of care followed by placebo) populations. The results of IMPACT I and II were consistent with each other. There were no statistically significant differences in safety profiles and the quality of life between the active and control groups.

Further review and analysis of the IMPACT I and II preliminary results is ongoing and full data from the IMPACT trials is expected to be presented at an upcoming medical meeting and published in a peer-reviewed journal.

OvaRex MAb-B43.13 (oregovomab) is one of five investigational immunotherapeutic monoclonal antibodies which Unither Pharmaceuticals licensed in April 2002 from AltaRex Medical Corp., a wholly-owned subsidiary of ViRexx Medical Corp. Based on the preliminary results from the IMPACT trials, Unither Pharmaceuticals intends to terminate the license agreement and intends to cease further development of the entire platform of antibodies. United Therapeutics is currently determining the amount of exit costs associated with termination of this program. While a precise estimate of write-down charges is not yet known, United Therapeutics has approximately $7 million in assets related to this program that are subject to write-down during the fourth quarter of 2007.

"Given what appeared to be the promising clinical activity observed in a subset of patients from an earlier phase II trial, we are very surprised by these findings. The IMPACT trials, which were well designed and rigorously conducted, indicate that the approach of triggering tumor-specific immunity using a murine monoclonal antibody has its challenges," said Christopher Nicodemus, MD, Unither Pharmaceuticals' Senior Vice President Clinical Research & Development.

"We are all disappointed that OvaRex did not make it to the finish line as a new therapeutic for ovarian cancer, and we owe a huge debt of gratitude to the women and physicians who participated in the studies," said Peter Gonze, Unither Pharmaceuticals' Chief Operating Officer.

About Ovarian Cancer
Ovarian cancer is the fifth leading cause of cancer deaths among women in the United States. The American Cancer Society estimates that in the United States this year, there will be over 20,000 new cases of ovarian cancer diagnosed and over 15,000 women will die from the disease. Overall, the five- year survival rate for women with distant disease is estimated to be 29%. Although most patients initially respond to surgery and chemotherapy, the relapse rate is high and once relapse occurs, there is no known curative therapy.

Source: United Therapeutics Corporation

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