Optimer Pharmaceuticals, Inc. (Nasdaq:OPTR) today announced that it completed a registered direct offering of 1,743,396 shares of common stock at a price of $8.48 per share, for total gross proceeds of $14.8 million. The closing involved the previously announced sale of 1,443,396 shares of Optimer’s common stock as well as an additional 300,000 shares of Optimer’s common stock which another institutional investor subsequently committed to purchase.

Optimer expects that the proceeds from the transaction will be used in the further development of its ongoing programs, as well as for other general corporate purposes.

All of the shares of Optimer common stock were issued pursuant to an effective registration statement previously filed with the U.S. Securities and Exchange Commission. The offering and sale of these securities were made only by means of a prospectus supplement and accompanying prospectus. This press release shall not constitute an offer to sell, or a solicitation of an offer to buy, nor shall there be any sale of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such jurisdiction.

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 is being developed for the treatment of Clostridium difficile infection, the most common hospital-acquired diarrhea. Prulifloxacin 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.