July 16, 2008

Rib-X Initiates Phase II Skin Infection Trial

Rib-X Pharmaceuticals has initiated a Phase II clinical trial for an intravenous form of antibiotic compound RX-3341 in the treatment of complicated skin and skin structure infections.

This Phase II double-blind study (study RX-3341-201) will evaluate the safety and efficacy of RX-3341 at two different doses administered intravenously to hospitalized complicated skin and skin structure infections (cSSSI) patients every 12 hours for five to 14 days, as compared to tigecycline (Tygacil).

The study's primary endpoint is the assessment of RX-3341 efficacy, safety and tolerability at the two different doses compared to that of tigecycline's standard dosing regimen. A secondary endpoint for the study is the assessment of clinical efficacy of RX-3341 compared to tigecycline in patients with cSSSIs caused by methicillin- resistant Staphylococcus aureus.

The safety and efficacy study will be conducted at 35 sites across the US. The company has also announced positive results of a two-part Phase I study with the same candidate.

The two-part Phase I study (RX-3341-103) compared the safety, tolerability and pharmacokinetics of two intravenous formulations of RX-3341. Part one of the study was designed to compare the safety and pharmacokinetics of the two IV formulations, with the purpose of optimizing the formulation of the IV dosage form.

Approximately 12 individuals received one dose of each of the formulations in a cross-over design. The two formulations were thus shown to be comparable in terms of exposure. The results showed that the chosen intravenous RX-3341 formulation was well tolerated using multiple doses for 14 days.