|Headquarters||New Haven, CT|
Rib-X Pharmaceuticals, founded in 2000, is an American privately held biopharmaceutical firm that focuses on the design and development of novel broad-spectrum antibiotics for the treatment of antibiotic-resistant infections in hospital and community settings. The company is located in New Haven, Connecticut. Rib-X seeks to exploit expertise in the structural biology (particularly ribosomal structure) and molecular modeling to design new antibiotics. With this technology they hope to design drug candidates with increased target affinity that overcome bacterial resistance, broadened antibacterial spectrum, and increased efficacy and safety.
Developmental candidates 
Pipeline in the clinical phase 
Rib-X's pipeline includes the following compounds in the clinical phase:
- Delafloxacin, a novel fluoroquinolone with activity against range of quinolone-resistant Gram-positive and Gram-negative bacteria, including MRSA, currently in a Phase 2b studys for hospital use. Delafloxacin was acquired from Wakunaga Pharmaceutical in 2006.
- Radezolid, a next-generation oxazolidinone designed for broader spectrum, enhanced potency and improved safety, has completed two Phase 2 studies. It has been shown to overcome linezolid resistance.
RX-04 Program 
The company has several compounds in a pre-clinical program designated RX-04: Three new classes of compounds have been identified that target a novel site on the bacterial 50S ribosomal subunit. These compounds were designed using the Rib-X proprietary approach to rational drug design based on structural analysis of the bacterial ribosome. Compounds have been identified with antibacterial activity against a number of the most difficult to treat, clinically important multi-drug resistant pathogens, including Methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. In mid-2011 Sanofi entered into a global research collaboration and licensing option with Rib-X Pharmaceuticals to develop and commercialize the novel classes of antibiotics resulting from RX-04.
- Rib-X Pharmaceuticals, Inc. Bloomberg Businessweek. Accessed 14 Oct 2011.
- Related Topics >> Rib-X Pharmaceuticals. Fierce Biotech. Accessed 14 Oct 2011.
- Rib-X Pharmaceuticals Signs Global Antibiotic Research Collaboration with Sanofi. PharmaDeals Review Vol 2011 Issue 7 | Page 70 12 Jul 2011. Accessed 14 Oct 2011.
- Rib-X Pharmaceuticals Presents Data for Radezolid Demonstrating Positive Antibacterial Activity and Ability to Overcome Common Bacterial Resistance Mechanism. Drugs.com News › Clinical Trials. 12 Sep 2010. Accessed 14 Oct 2011.
- IDSA hit list of dangerous microbes, 2006.
- Rib-X Pharmaceuticals Presents Comprehensive Overview of RX-04 Program in 14 Posters at ICAAC. Drugs.com News › Clinical Trials. 20 Sep 2011. Accessed 14 Oct 2011.