OPTIMER REPORTS RESULTS OF CDAD STUDIES

Phase IIa clinical studies have indicated that Optimer's lead antibiotic candidate, OPT-80/PAR-101, appears to be efficacious in the treatment of Clostridium difficile-associated diarrhea (CDAD). The company has recently received FDA approval of its Phase IIb/III clinical trial protocols and plans to begin these trials in April 2006.

In the Phase IIa dose ranging study, OPT-80/PAR-101 was evaluated in 45 CDAD patients. The evaluation included cure rates, relief of symptoms of CDAD, time to resolution of diarrhea, and clinical recurrence. OPT-80/PAR-101 was well-tolerated by all subjects, and the clinical response was very promising with a 91 percent cure rate overall. Of the subjects that completed therapy, less than 5 percent of patients had recurrence of symptoms.