Leading Medical Experts Call for More Effective Strategies to Address Clostridium difficile-Associated Disease.

SAN DIEGO -- Leading medical experts in the field of Clostridium difficile-Associated Disease or (CDAD), called for more effective strategies to prevent, rapidly diagnose and treat CDAD, according to presentations made during a symposium entitled "Clostridium Difficile-Associated Disease: Underdiagnosed, Underreported, Undertreated; How to Overcome the Challenges" at the Infectious Diseases Society of America (IDSA) Annual Meeting in San Diego, California.

CDAD is a severe form of infectious diarrhea, which in some cases can cause death. It is estimated that this disease affected more than 500,000 people in the United States in 2005. The U.S. hospital discharge data from the Centers for Disease Control and Prevention indicate there were approximately 253,000 hospitalizations affected by CDAD in 2005, resulting in a rate that has more than doubled since 2000.

"The goal of this symposium was to further the education of physicians on the importance of properly diagnosing and treating CDAD, as well as preventing its spread," said Mark A. Miller, M.D., Chief of the Division of Clinical Microbiology, Head of the Division of Infectious Diseases, Chair of the Infection Prevention and Control Unit at the Jewish General Hospital, and Associate Professor of Medicine and Microbiology/Immunology at McGill University in Montreal, Quebec, Canada, who served as chairperson of the symposium sponsored by Optimer Pharmaceuticals (Nasdaq:OPTR). "Important and highly lethal epidemics of CDAD have been documented in Canada, the United States, the United Kingdom, France, and the Netherlands, and may soon be moving into other geographic areas. Current treatment options are limited, and there is an urgent need for better therapies with the ability to act rapidly to control symptoms and also prevent relapses."

According to a presentation by L. Clifford McDonald, M.D., Medical Epidemiologist at the U.S. Centers for Disease Control and Prevention, much of the recent increases in rates and disease severity may be attributed to a recently recognized epidemic strain known as type BI, North American Pulsed-Field Type 1 (NAP1), and PCR-ribotype 027 or BI/NAP1/027. This hypervirulent strain exhibits increased resistance to fluroquinolones and cephalosporins, and carries an extra toxin, called binary toxin, in addition to toxins A and B. His surveillance data showed a continued increase in the rate of CDAD across the United States and the presence of the new epidemic strain in up to 38 states now.

At the symposium, Dr. Miller presented a review of the studies which have evaluated the currently-accepted CDAD antibiotic therapies: metronidazole and vancomycin. "The most-commonly used treatment, metronidazole, is now recognized to be inadequate for patients with severe CDAD, leaving us with only one other option. Newer therapies are desperately needed for this life-threatening illness." Dr. Miller summarized the potential treatments on the horizon which are currently being studied for the treatment and prevention of CDAD. These include newer antibiotics which target the offending bacteria without harming the patient's normal microbial balance, immune-enhancing products and vaccines.

Ellie Goldstein, M.D., clinical professor of medicine, at The David Geffen School of Medicine at UCLA and director, at R.M. Alden Research Laboratory in Santa Monica, California spoke about risk factors that place patients at greater risk for CDAD and CDAD-related death. The most important risk factors are advanced age of the patient, a low blood albumin level, and a longer stay in the healthcare environment. He also discussed the importance of relapses with this disease, and the complications due to these recurrences.

At the symposium, Thomas J. Louie, M.D., Medical Director, Infection Prevention and Control and Professor of Microbiology-Infectious Diseases at University of Calgary in Calgary, Alberta, Canada suggested that disruption of the gastrointestinal microflora may be the underlying process leading to CDAD as well as the relapses or recurrences following treatment with standard therapies. Dr. Louie is examining potential new treatments, such as OPT-80, which may have less of an impact on the indigenous microflora of the large intestine.

Ferric Fang, M.D., Professor of Laboratory Medicine and Microbiology, Division of Allergy and Infectious Diseases at the University of Washington, School of Medicine in Seattle, WA, demonstrated at the symposium that conventional diagnostic methods used to detect C. difficile in stool specimens are slow, non-specific and insensitive. Dr. Fang presented a two-step screening approach for the detection of C. difficile (CD) toxin in CD-antigen-positive specimens. This approach is more sensitive and specific, and can provide same-day results for patients suspected of having CDAD.

About The Sponsor

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative anti-infective products for the treatment of serious infections. Optimer currently has two late-stage anti-infective product candidates. OPT-80, currently in two pivotal Phase 3 clinical trials, is being developed for the treatment of Clostridium difficile-associated diarrhea, the most common hospital-acquired diarrhea. Prulifloxacin, also currently in two pivotal Phase 3 clinical trials, is an antibiotic being developed for the treatment of travelers' diarrhea, a form of infectious diarrhea. Additional information regarding Optimer and its products can be found at www.optimerpharma.com.

Forward-looking Statements

Statements included in this press release that are not a description of historical facts are forward-looking statements, including without limitation all statements related to CDAD and C. difficile, their expected rate of occurrence, the future effectiveness of existing therapies, the need for new therapies and the effectiveness of potential new therapies, including OPT-80. Words such as "believes," "anticipates," "plans," "expects," "intend," "will," "goal" and similar expressions are intended to identify forward-looking statements. The inclusion of forward-looking statements should not be regarded as a representation by Optimer that any future events will occur.