EPIX Pharmaceuticals Initiates Phase 2a Clinical Trial in Patients with Mild Alzheimer's Disease.

Trial to Evaluate 5-HT4 Agonist Alone and in Combination with Aricept[R] (donepezil HCl)

LEXINGTON, Mass. -- EPIX Pharmaceuticals, Inc. (NASDAQ:EPIX) announced today the initiation of a Phase 2a clinical trial to further evaluate PRX-03140 as monotherapy and in combination with donepezil for the treatment of Alzheimer's disease. This Phase 2a trial is designed to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of PRX-03140 administered orally once-daily for 14 days in patients with mild Alzheimer's disease who are on a stable dose of donepezil (10 mg). Data from this trial are expected in the second half of 2007.

"This Phase 2a trial is designed to build on the promising results observed in our Phase 1b trial, in which treatment with PRX-03140 resulted in the desired changes in brain wave activity in patients suffering from Alzheimer's disease," said Michael G. Kauffman, M.D., Ph.D., chief executive officer of EPIX Pharmaceuticals. "To date, our data indicate that PRX-03140 stimulates acetylcholine production in the brain without the peripheral side effects commonly seen with currently approved drugs. There remains a significant unmet need for Alzheimer's disease drug therapies that will improve symptoms with minimal side effects. Because of its complementary mechanism of action with cholinesterase inhibitors, we believe that PRX-03140 may produce a synergistic effect when administered in combination with donepezil."

The primary endpoints of this randomized, double-blind, multiple ascending dose Phase 2a trial are to assess the safety and tolerability of PRX-03140 administered alone and in combination with donepezil, and to measure the effect of PRX-03140 on quantitative electroencephalograms (qEEGs), including the alpha/theta ratio (a biomarker which indicates an effect on the cholinergic system in the brain). Secondary endpoints of the trial include assessing the effects of repeat doses of PRX-03140 on a battery of standardized cognitive function tests, as well as evaluating the pharmacokinetic effect of PRX-03140 on donepezil concentrations in patients with mild Alzheimer's disease.

PRX-03140 was well tolerated in a Phase 1b trial in patients with Alzheimer's disease and in two additional Phase 1 clinical trials in healthy adult and elderly volunteers. In the 14-day Phase 1b clinical trial, treatment with PRX-03140 resulted in changes in brain wave activity in Alzheimer's patients that are consistent with those seen in clinical trials with currently approved drugs for Alzheimer's disease. The Phase 1b trial assessed the effects of PRX-03140 on quantitative electroencephalograms (qEEGs) and treatment with PRX-03140 resulted in a statistically significant improvement in the quantitative EEG slow wave pattern when compared with placebo. This trial demonstrated that PRX-03140 is active in the central nervous system.

About PRX-03140

PRX-03140 is EPIX's second of four clinical drug candidates discovered utilizing its proprietary computer-based G-Protein Coupled Receptors (GPCR) models and optimized with integrated computational-medicinal chemistry. PRX-03140 is selective for the 5-HT4 receptor in the brain, and preclinical studies have shown that it improves cognitive function, as well as increases levels of acetylcholine, soluble amyloid precursor protein (sAPP) and brain-derived neurotrophic factor (BDNF) in regions of the brain known to be important for memory.

About Alzheimer's Disease

Alzheimer's disease is a debilitating neurodegenerative disorder characterized by progressive loss of memory and cognitive function, affecting 4.5 million Americans according to the Alzheimer's Association, and over 9 million worldwide according to the Alzheimer's Disease International Association. The U.S. National Institute of Aging estimates that about 5% of the population aged 65-74 and as many as 50% of those over age 85 have the disease. The global market for Alzheimer's disease drugs is growing rapidly, from $3 billion in 2004 to nearly $7 billion expected in 2010, as estimated by Espicom.

Acetylcholinesterase (AChE) inhibitors, a class of drugs approved for the treatment of Alzheimer's disease that includes donepezil, are active in patients provided that endogenous production of ACh is sufficient to maintain local levels. As Alzheimer's disease progresses, ACh production declines, and brain levels of this critical neurotransmitter decline. In parallel with effective therapeutics in other neurodegenerative diseases (e.g., Parkinson's disease), replacement of the prominent neurotransmitter lost in Alzheimer's disease should provide significant clinical benefit. However, neither ACh nor its components can be given in sufficient quantities to increase brain ACh levels with tolerable side effects. The search for agents that increase the production and/or release of ACh, which can be used alone or in combination with AChE inhibitors, may therefore yield a drug candidate with significant clinical benefit. Early data suggest PRX-03140 may meet this need.

About EPIX

EPIX Pharmaceuticals is a biopharmaceutical company focused on discovering, developing and commercializing novel pharmaceutical products through the use of proprietary technology to better diagnose, treat and manage patients. The company has a blood-pool imaging agent (Vasovist[TM]) approved and marketed in Europe and approved in Canada, Australia and Switzerland, and five internally-discovered therapeutic and imaging drug candidates currently in clinical trials targeting conditions such as depression, Alzheimer's disease, cardiovascular disease and obesity. These drug candidates include EP-2104R, a novel thrombus imaging agent which has completed a Phase 2a trial, PRX-08066 in Phase 2 clinical development for pulmonary hypertension associated with chronic obstructive pulmonary disease, and PRX-03140 which is in a Phase 2a clinical trial in Alzheimer's disease. EPIX also has collaborations with leading organizations, including Amgen, Cystic Fibrosis Foundation Therapeutics, and Schering AG (Germany). For more information about EPIX, please visit the company's website at www.epixpharma.com.

This news release contains express or implied forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, that are based on current expectations of management. These statements relate to, among other things, our expectations regarding the progress and results of our clinical development program for PRX-03140 and other drug candidates. These statements are neither promises nor guarantees, but are subject to a variety of risks and uncertainties, many of which are beyond our control, and which could cause actual results to differ materially from those contemplated in these forward-looking statements. In particular, the risks and uncertainties include, among other things: risks that product candidates, including PRX-03140, may fail in the clinic or may not be successfully marketed or manufactured; risks relating to the our ability to advance the development of product candidates currently in the pipeline or in clinical trials, any failure to comply with regulations relating to our products and product candidates, including FDA requirements; failure to obtain the financial resources to complete development of product candidates; the risk that the FDA may interpret the results of our studies differently than we have; competing products may be more successful; our inability to interest potential partners in our technologies and products; our inability to achieve commercial success for our products and technologies; the possibility of delays in the research and development necessary to select drug development candidates; the risk that we may be unable to successfully secure regulatory approval of and market our drug candidates; and risks of new, changing and competitive technologies and regulations in the U.S. and internationally. Existing and prospective investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. We undertake no obligation to update or revise the information contained in this press release, whether as a result of new information, future events or circumstances or otherwise. For additional information regarding these and other risks that we face, see the disclosure contained in our filings with the Securities and Exchange Commission, including our most recent Quarterly Report on Form 10-Q.

ARICEPT([R]) (donepezil HCl tablets) is a registered trademark of Eisai Co., Ltd.

Copyright e 2006 Eisai Inc. and Pfizer Inc.