According to the top-line results from the phase III study announced Monday night, 88% of patients treated with OPT-80 achieved a clinical cure compared to 86% of patients treated with Vancocin.

Patients were treated with OPT-80 twice daily for 10 days. Vancocin was dosed four times daily, also for 10 days. A clinical cure was defined as patients requiring no further therapy for C. diff two days after completing treatment.

A key secondary endpoint of the study measured the recurrence, or relapse rate. Here, too, OPT-80 excelled, with just 15% of patients reporting a recurrence of the C. diff infection four weeks after treatment compared to a 25% recurrence rate reported for patients treated with Vancocin.

Optimer's phase III study was designed to show statistically non-inferior efficacy of OPT-80 compared to Vancocin on both the primary endpoint (cure rate) and the secondary endpoint of recurrence rate. The fact that OPT-80 was numerically superior on both endpoints is a big win for the drug.

Recurrence of C. diff infection in treated patients is a growing problem, so the lower recurrence rate for OPT-80 makes a strong case for using the drug as a first-line treatment.

A second phase III study of OPT-80 in C. diff patients is ongoing with data expected in the second half of 2009. Optimer also said it plans to resurrect partnering discussions for OPT-80. In 2007, an experimental antibiotic from Genzyme ( GENZ) failed a closely watched phase III study.

Optimer shares closed Monday at $4.60 prior to the release of the OPT-80 study results. That news sent the stock up 90% to $8.75 in the after-hours session.

Know What You Own: In Tuesday's early trading, other top biotech performers include Genetic Technologies ( GENE), Targacept ( TRGT), Cytokinetics ( CYTK) and BioDelivery Sciences ( BDSI).
At the time of publication, Feuerstein's Biotech Select model portfolio was long Optimer Pharmaceuticals.

Adam Feuerstein writes regularly for In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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