Antibiotic Drug Discovery Platform Discovers Novel Compounds

The Rx-04 discovery program is focused on the development of novel classes of antibiotics active against serious, rapidly emerging multi-drug resistant Gram-negative bacteria such as Pseudomonas aeruginosa and Acinetobacter baumannii. The company has built five chemical scaffolds, some of which have demonstrated activity against both Gram-negative and Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Data from an earlier, related program will be presented during a poster sessions at the 49th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in San Francisco.

"In less than one year, our structure and computationally driven research engine has engineered a variety of new lead scaffolds that appear to exhibit promising activity in mice, good drug-like properties and good safety in early tests, in addition to varied profiles against MDR gram-negative pathogens in vitro," said Susan Froshauer, PhD, President and CEO of Rib-X Pharmaceuticals. "The success we've seen to date with our later clinical stage antibiotic compounds, radezolid and delafloxacin, along with the immense progress made on the Rx-04 program, underscores the strength and diversity of the growing Rib-X pipeline."

About Rx-04

The Rx-04 program employs a de novo approach to develop novel antibiotics that are active against Gram-negative bacteria. This program exploits the peptidyl transferase region of the 50S subunit, which is the catalytic region of the ribosome and the binding site of many chemically distinct classes of antibiotics, including oxazolidinones (e.g., linezolid), lincosamides (e.g., clindamycin), phenyl propanoids (e.g., chloramphenicol), pleuromutilins (e.g., retapamulin), macrolides/ketolides (e.g., azithromycin) and sparsomycin. Rib-X has created five completely novel series of compounds targeting two novel sites that show good antibacterial activity against a number of clinically important multi drug resistant Gram-negative pathogens.

About Rib-X Pharmaceuticals, Inc.

Rib-X Pharmaceuticals, Inc. is a product-driven small molecule drug discovery and development company focused on the structure-based design of new classes of antibiotics. The Company's underlying drug discovery engine capitalizes on its proprietary high-resolution crystal structure of the ribosome, which performs an essential role in protein synthesis. Many known, commercially valuable antibiotics exert their effects by binding to the bacterial ribosome. The Company's integrated research strategy, which combines state-of-the-art, proprietary computational analysis, X-ray crystallography, medicinal chemistry, microbiology and biochemistry, allows it to rapidly synthesize new agents designed to avoid typical antibiotic resistance mechanisms.

Rib-X's iterative intelligent engine has yielded several distinctive new antibiotics that can be used for the treatment of either community- or hospital-acquired infections. In addition to Rx-04, Rib-X has successfully completed Phase 2 trials with delafloxacin (RX-3341), a broad spectrum fluoroquinolone with potent activity against quinolone resistant Gram-positive bacteria including MRSA. Radezolid (RX-1741), an oxazolidinone that was discovered at Rib-X, as an oral/IV agent for treatment of serious Gram-positive infections has completed two Phase 2 trials and the Rx-02 discovery program which is focused on developing an IV/oral macrolide active against methicillin-resistant S. aureus, multidrug-resistant Streptococcus pneumoniae and S. pyogenes. Both delafloxacin and radezolid are currently in late stage clinical trials.