Optimer Pharmaceuticals Reports Positive Data from its North American Phase 3 CDI Study of OPT-80

OPT-80 Achieves its Primary Endpoint of Clinical Cure with a Lower Recurrence Rate vs. Vancocin(R)

Optimer Pharmaceuticals, Inc. (Nasdaq: OPTR) today released positive top-line results from a pivotal Phase 3 clinical study of the Company’s lead anti-infective drug candidate, OPT-80, in patients with Clostridium difficile Infection (CDI).

92.1% of patients treated with OPT-80 (per protocol population) achieved clinical cure vs. 89.8% for Vancocin. In addition, only 13.3% of patients treated with OPT-80 experienced a recurrence vs. 24.0% for Vancocin (p = 0.004). Patients treated with OPT-80 had a global cure (cure with no recurrence within four weeks) of 77.7%, which was greater than Vancocin at 67.1% (p = 0.006). OPT-80 was well-tolerated.

"We are very pleased with the results of this study, the first of our two pivotal Phase 3 trials. This study highlights the important differentiating features of OPT-80, including lower recurrence and higher global cure rate than Vancocin, the only FDA approved antibiotic for the treatment of CDI,” commented, Michael N. Chang, Optimer’s Chief Executive Officer. “I believe OPT-80 will be an important therapeutic option for CDI, an infection that currently has limited treatment options and affects more than 500,000 patients in the United States annually with growing incidence worldwide. Our next step is to complete the on-going second Phase 3 study at clinical sites in Europe and North America to support an NDA filing."

The OPT-80 clinical trial (Protocol 101.1.C.003) is the largest single comparative study ever conducted against Vancocin. The detailed data from the study will be presented at a medical conference in the near future. Top-line trial results are summarized in the table below.

OPT-80 Clinical Study Design

In this multi-center, randomized, double-blind Phase 3 clinical trial, 629 adult subjects were enrolled. Subjects with confirmed CDI received either 200 mg OPT-80 dosed orally twice daily or 125 mg Vancocin dosed orally four times daily. This study was conducted in more than 100 clinical sites throughout North America. The objective of the study was to show that a 10-day course of OPT-80 was at least as efficacious (non-inferior) and safe as a 10-day course of Vancocin (vancomycin hydrochloride capsules, USP) for the treatment of CDI.

The primary endpoint of the study was clinical cure defined as patients requiring no further CDI therapy two days after completion of study medication, as determined by the investigator. The secondary endpoint evaluated CDI recurrence up to four weeks post therapy with recurrence defined as the return of diarrhea associated with CDI confirmed by a positive toxin test. Global cure, an exploratory endpoint, was defined as patients who were cured and did not have a recurrence.

About Clostridium Difficile Infection

CDI has become a growing problem in hospitals, long-term care facilities and in the community. It is a serious illness caused by infection of the inner lining of the colon by C. difficile bacteria, which produce toxins that cause inflammation of the colon, severe diarrhea and, in the most serious cases, death. CDI typically develops from the use of broad-spectrum antibiotics that disrupt normal gastrointestinal (gut) flora, allowing C. difficile bacteria to flourish.

Current therapeutic options for CDI include metronidazole and oral vancomycin. However, approximately 20% to 30% of CDI patients who initially respond to these treatments experience a clinical recurrence following cessation of antibiotic administration.

Higher incidence and severity of CDI, increased treatment failures with standard therapies and the emergence of the hypervirulent BI (NAP1/027) strain of C. difficile have combined to result in greater awareness of CDI and growing concern among medical professionals and public health officials.

About OPT-80

OPT-80 is the first in a new class of antibiotics called macrocyclics, which inhibit the bacterial enzyme RNA polymerase, resulting in the death of Clostridium difficile. The narrow spectrum profile of OPT-80 may eradicate Clostridium difficile selectively with minimal disruption to the normal intestinal flora. This may facilitate the return of the normal physiological conditions in the colon and reduce the probability of CDI recurrence.

Conference Call Information

The Company will host a conference call for the investment community today beginning at 2:00 p.m. Pacific time (5:00 p.m. Eastern time) to discuss the results of the OPT-80 Phase 3 trial and answer questions.

To participate in the live call by telephone, please dial (877) 627-6580 from the U.S., or (719) 325-4864 from outside the U.S. The conference call will be webcast live under the Investors section of Optimer’s website at www.optimerpharma.com.

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative anti-infective products to treat serious infections and address unmet medical needs. Optimer has two late-stage anti-infective product candidates under development. OPT-80 is the only antibiotic therapy currently in Phase 3 worldwide clinical development for Clostridium difficile infection. Prulifloxacin is an antibiotic being developed for the treatment of travelers’ diarrhea, a form of 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 OPT-80, the incidence and anticipated effects of CDI, the efficacy of current CDI treatments and OPT-80 and the timing of clinical trials and anticipated results thereof. Words such as "believes", "anticipates", "plans", "expects", “may”, "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. 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 relating to: the timing, progress and likelihood of success of its research and development and clinical trial programs, the timing and status of its preclinical and clinical development of potential drugs, the development of alternative treatments for CDI, and other risks detailed in Optimer's filings with the Securities and Exchange Commission.

Contact:

Optimer Pharmaceuticals, Inc.
Christina Donaghy, Corporate Communications Manager
John D. Prunty, Chief Financial Officer & VP Finance
858-909-0736
or
Porter Novelli Life Sciences
Jason I. Spark, Vice President
619-849-6005

Source: Optimer Pharmaceuticals, Inc.