Rib-X Pharmaceuticals initiates two separate Phase II clinical trials for antibiotic compound

Rib-X Pharmaceuticals, Inc. has announced the enrolment of the first patients in two separate Phase 2 clinical trials.

The studies will evaluate the safety and efficacy of RX-1741 in the treatment of Community-Acquired Pneumonia (CAP), and separately in the outpatient treatment of Uncomplicated Skin and Skin Structure Infections (uSSSI). RX-1741 is the Company's first antibiotic program developed using its proprietary technology platform.

RX-1741 is an oxazolidinone antibiotic that exhibits activity against methicillin-resistant Staphylococcus aureus (MRSA) and other Gram-positive organisms, and has demonstrated both greater spectrum and potency of activity than the currently marketed product of the same class, Zyvox(R) (linezolid). Discovered using proprietary knowledge of the three dimensional structure of a key area of the ribosome, the 50S subunit, Rib-X believes that RX-1741 will demonstrate a high level of effectiveness against resistant microbes.

"These two studies represent important milestones for Rib-X," said Dr. Susan Froshauer, President and CEO of Rib-X Pharmaceuticals. "RX-1741 is the first of many compounds that Rib-X intends to design and develop in response to the alarming growth of drug resistant microbial pathogens found both in the hospital and in the community. This MRSA-active agent will satisfy a critical need for physicians and their patients because current treatment options are very limited, particularly for orally active agents," said Dr. Froshauer.

CAP Study Design

The CAP study is a Phase 2, multicenter, randomized, double-blind study designed to evaluate the safety and efficacy of RX-1741 in the treatment of adult patients with mild to moderate severity of Community-Acquired Pneumonia (CAP). The study will assess the efficacy of three doses of RX-1741, either once or twice a day, for seven to 10 days in the treatment of adult patients with mild to moderate CAP. It will also evaluate the safety and tolerability profile of the three doses.

The CAP study will enroll approximately 160 patients in 40 study centers across the US, Canada, and Russia, and the Company expects to have preliminary data available when approximately 80 patients (50% of the planned patients) have completed the study. The Company intends to release data from all patients during the first half of 2008.

uSSSI Study Design

The uSSSI study is a Phase 2, multicenter, randomized, open-label, comparative study to evaluate the safety and efficacy of RX-1741 versus linezolid in the outpatient treatment of adult patients with Uncomplicated Skin and Skin Structure Infections (uSSSI). The study will assess the efficacy of a single dose of RX-1741 given either once daily or twice daily compared to linezolid given twice daily for five to ten days in the treatment of ambulatory patients with uSSSI. It will also evaluate the safety and tolerability profile of these two doses compared to linezolid.

The uSSSI study will enroll approximately 150 patients in 25 study centers across the US and the Company expects an interim analysis of the data to be performed when approximately 75 patients (50% of the planned patients) have completed the study. The Company intends to release data from all patients during the first half of 2008.