Salt Lake City -- December 1, 2009 -- Myriad Pharmaceuticals Inc. (Nasdaq:MYRX) today announced the initiation of a Phase 2b study of MPC-4326, a first-in-class, small molecule inhibitor of HIV-1 maturation.

This multicenter, randomized, open-label study is designed to determine MPC-4326 efficacy in an optimized background regime. The study participants will be experienced HIV-1 infected individuals who are failing current therapy and have documented resistance to at least one agent in each of the 'classic' three ARV [antiretroviral] classes (NRTI, NNRTI, PI). The study will utilize the new tablet formulation of MPC-4326 and will test two doses of the experimental therapy.

The primary objective of this study is to determine viral suppression in the drug treated cohorts at 24 weeks. In addition this trial will determine time to viral suppression and assess the safety and tolerability of MPC-4326 in combination with a two-to-three drug optimized ARV therapy.

This phase 2b trial will further assess and refine a potential companion diagnostic -- a simple, rapid and inexpensive assay to determine viral genotype in HIV-1 infected patients. The study protocol includes the use of a pre-specified model of HIV-1 Gag polymorphisms to predict MPC-4326 response. Viral genotype will be one of the inclusion criteria used in identifying study participants.

"We are pleased to announce the advancement of the clinical development of MPC-4326," said Dr. Adrian Hobden, President and CEO of Myriad Pharmaceuticals. "In addition, we look forward to further evaluation of a companion diagnostic that could be used to identify those individuals who would have the greatest benefit from MPC-4326. It is a distinct advantage to patients and physicians to have the ability to identify in advance those who will respond to a given drug."

About MPC-4326

MPC-4326 is being developed by Myriad Pharmaceuticals, Inc. for the oral treatment of HIV-1 infection. MPC-4326 is the first of a class of antiretroviral (ARV) drug candidates that inhibit HIV-1 replication by interfering with the maturation of the HIV-1 virus. Specifically, MPC-4326 interferes with the last step in the processing of the HIV-1 Gag protein. This inhibition leads to formation of noninfectious, immature virus particles, thus preventing subsequent rounds of HIV infection. As expected for a novel mechanism of action, MPC-4326 retains inhibitory activity against HIV-1 isolates resistant to the four classes of currently approved drugs commonly used by HIV infected patients: NRTIs, NNRTIs, protease inhibitors and fusion inhibitors. No cross-resistance has been observed.

Over 675 subjects, including over 180 HIV-infected individuals, have been studied in clinical trials of MPC-4326. Results from these trials have shown MPC-4326 to be well-tolerated and have demonstrated significant and clinically relevant reductions in viral load in a subset of HIV-infected patients representing approximately 60-70% of HIV-infected patients. This "responder" population can be identified by a simple, rapid and inexpensive assay of the HIV virus. In a Phase 2 clinical trial completed in 2008, MPC-4326 met its primary objective by demonstrating viral reduction in HIV-positive. In addition, the safety profile of MPC-4326 was comparable to earlier studies where that profile had been similar to placebo.

About Myriad Pharmaceuticals, Inc.

Myriad Pharmaceuticals, Inc. is a specialty pharmaceutical company focused on discovering, developing, and commercializing novel small molecule drugs that address severe medical conditions, including cancer and HIV infection. Our pipeline includes clinical and pre-clinical product candidates with distinct mechanisms of action and novel chemical structures that have the potential to be first-in-class and/or best-in-class therapeutics.

For more information visit www.myriadpharma.com.