Optimer Pharmaceuticals, Inc. Announces Exercise in Full of Underwriters’ Option to Purchase Additional Shares and Closing of Public Offering of Common Stock

SAN DIEGO, Feb. 16, 2011 /PRNewswire/ -- Optimer Pharmaceuticals, Inc. (Nasdaq: OPTR) today announced the completion of a public offering of 6,900,000 shares of its common stock, including 900,000 shares sold pursuant to the full exercise of an overallotment option previously granted to the underwriters. The shares were sold at a public offering price of $11.25 per share, resulting in aggregate gross proceeds to Optimer of $77.6 million, before deducting underwriting discounts and commissions and other estimated offering expenses payable by Optimer.

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Jefferies & Company, Inc. acted as the sole book-running manager for the offering. Baird, Canaccord Genuity Inc., JMP Securities, Needham & Company, LLC, and ThinkEquity LLC acted as co-managers for the offering.

Optimer anticipates using the net proceeds from the offering to prepare for the potential commercial launch of fidaxomicin in the United States, if approved, as well as for research and development activities, potential in-licenses or acquisitions, working capital and other general corporate purposes.

A shelf registration statement relating to the shares was filed with the Securities and Exchange Commission (SEC) and is effective. A final prospectus supplement related to the offering has been filed with the SEC and is available on the SEC’s website located at www.sec.gov. Copies of the final prospectus supplement and the accompanying prospectus relating to the offering may be obtained from Equity Syndicate Prospectus Department, Jefferies & Company, Inc., 520 Madison Avenue, 12th Floor, New York, NY, 10022, at 877-547-6340 and at Prospectus_Department@Jefferies.com.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy these securities, nor shall there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or other jurisdiction.

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing hospital specialty products to treat serious infections and address unmet medical needs. Optimer has two anti-infective product candidates in development, fidaxomicin and Pruvel (prulifloxacin). Fidaxomicin is a narrow spectrum antibiotic being developed for the treatment of Clostridium difficile infection (CDI). The FDA granted the Company’s request for six-month Priority Review of fidaxomicin, and has assigned a Prescription Drug User Fee Act (PDUFA) goal date of May 30, 2011. The Company also filed a MAA with the European Medicines Agency (EMA) for fidaxomicin. Pruvel is a prodrug in the fluoroquinolone class of antibiotics being developed as a treatment for infectious diarrhea. Additional information can be found at http://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 Optimer’s anticipated use of the net proceeds from the offering as well as the potential commercial launch of fidaxomicin. 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 of its plans will be achieved. These forward-looking statements are based on current information that may change and you are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this press release. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Optimer’s business including, without limitation, risks detailed in Optimer’s filings with the SEC. All forward-looking statements are qualified in their entirety by this cautionary statement, and Optimer undertakes no obligation to revise or update any forward-looking statement to reflect events or circumstances after the issuance of this press release.

SOURCE Optimer Pharmaceuticals, Inc.