SAN DIEGO--- Optimer Pharmaceuticals Announces Change to Board of Directors

Optimer Pharmaceuticals, Inc. (Nasdaq: OPTR) today announced that Martin C. Muenchbach, Ph.D., an Investment Manager at Bellevue Asset Management AG, has notified the Company that he will be stepping down from his position as a member of the Board of Directors as of August 1, 2008. Dr. Muenchbach joined the Board in December 2005, advising Optimer as a private company and then working with the Company in its transition to a public company. Dr. Muenchbach’s departure is not related to relations with the board members or with the company. Dr. Muenchbach will continue to follow his pursuits in venture capital, serving on the Board of many privately held companies. Optimer is currently in the process of identifying candidates to serve on its Board of Directors.

“We would like to thank Martin for his many contributions and dedicated service to the Company. His board experience and leadership have been invaluable as the company has grown from a private company through its maturation as a public company," said Michael N. Chang, Ph.D., CEO and President of Optimer. “We wish him great success in his future endeavors.”

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative anti-infective products for the treatment of serious infections. Optimer 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 infection, the most common hospital-acquired diarrhea. Prulifloxacin, also 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 can be found at http://www.optimerpharma.com.