United Therapeutics Corp. said it will cease development of its OvaRex ovarian cancer candidate after two pivotal trials failed to meet their endpoints. UTC, and its wholly-owned subsidiary Unither Pharmaceuticals Inc., also said they will end their development agreement with ViRexx Medical Corp., from which UTC licensed the product in 2002.

The news barely budged United's stock, but sent ViRexx shares plummeting 79 percent.

The identical studies, known as IMPACT I and II (IMunotherapy Pivotal ovArian Cancer Trial), were randomized, double-blind, placebo-controlled trials involving 367 ovarian cancer patients at more than 60 U.S. centers.

The studies assessed the efficacy of OvaRex mono-immunotherapy during the so-called "watchful waiting" period following front-line carboplatin-paclitaxel-based chemotherapy. The goal was to confirm data from a subset analysis of a prior Phase II study, which suggested OvaRex had potential to extend the time to disease relapse among patients who had successfully completed front-line therapy.

However, both studies demonstrated no difference between active (standard of care followed by OvaRex) and control (standard of care followed by placebo) populations. UTC said the trials were well conducted, the results were consistent, and there were no statistically significant differences in safety profiles and the quality of life between the active and control groups.

OvaRex MAb-B43.13 (oregovomab) was among five investigational immunotherapeutic monoclonal antibodies Unither licensed in 2002 from AltaRex Medical Corp., a wholly-owned subsidiary of Edmonton, Alberta-based ViRexx. (See BioWorld Today, April 23, 2002.)

In announcing the trial failures, Silver Spring, Md.-based UTC also said Unither will terminate the license agreement and cease further development of the entire platform of antibodies. UTC said it still is determining the exit costs and noted it has approximately $7 million in assets related to the program that are subject to write-down during the fourth quarter.

"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," said Christopher Nicodemus, Unither' senior vice president of clinical research and development.

UTC shares (NASDAQ:UTHR) fell $1.55 Wednesday to close at $98.74, while shares of ViRex (AMEX:REX) lost 5 cents, or 79 percent, to close at 12 cents.