Rib-X Pharmaceuticals and Sanofi Sign a Research Collaboration Agreement on Novel Classes of Antibiotics

Rib-X Pharmaceuticals, Inc. announced today the signature of an exclusive worldwide research collaboration agreement and option for license with Sanofi (EURONEXT: SAN and NYSE: SNY) for novel classes of antibiotics resulting from Rib-X’s RX-04 program for the treatment of resistant Gram-positive and resistant Gram-negative pathogens.

Rib-X’s RX-04 program employs a proprietary approach for rational drug design resulting in entirely new families of compounds that have demonstrated efficacy at low, single doses in murine infection models. The RX-04 development program has shown antibacterial activity against a number of the most difficult to treat, clinically important, multi-drug resistant Gram-negative and Gram-positive pathogens. The Rib-X RX-04 program targets bacterial ribosomes, an internal cell component, where proteins are synthesized from amino acids and RNA. Recently presented data confirms the novel classes directly impact ribosome function and exert their anti-bacterial activity by interfering with protein synthesis.

Under the terms of the agreement, Rib-X will receive $10 million in an upfront payment. Rib-X is also eligible to receive up to an additional $9 million in near-term research-based milestones and will be eligible to receive further payments for the achievement of research, preclinical, regulatory and commercial milestones. Sanofi has the right to develop multiple products under this agreement. Except for those assets licensed to Sanofi through the agreement, Rib-X retains its rights to the discovery platform and its future programs. The agreement could result in up to $86 million in development and regulatory milestones on a per product basis. Commercial milestones could exceed $100 million on a per product basis. Rib-X retains a co-promotion option in the United States on one of the molecules coming from the collaboration. Royalty rates on net sales could reach low double digit figures.

"We could not be more excited about partnering with a preeminent global pharmaceutical company such as Sanofi. This partnership reflects our shared commitment to staying ahead of the growing problem of antibiotic resistance by delivering new standards of care for patients in need,” said Mark Leuchtenberger, President and Chief Executive Officer at Rib-X Pharmaceuticals. "The RX-04 program’s completely novel classes of antibiotics should lead to true breakthrough therapies and we look forward to working in partnership with Sanofi to advance these treatments into the clinic and eventually bring them to the global market. Importantly, this agreement will enable Rib-X to aggressively advance our clinical stage candidates, delafloxacin and radezolid, towards pivotal trials and support additional discovery-stage programs like RX-05 and RX-06.”

"We are very enthusiastic about entering into this collaboration with Rib-X,” said Elias Zerhouni, M.D., President, Global Research & Development, Sanofi. "The clinical need for new antibiotics is reaching crisis level, yet the antibiotic pipeline is running dry and fewer and fewer companies are working to develop drugs in this space. This partnership exemplifies Sanofi’s commitment to translate novel approaches for treatment into patient solutions addressing the global critical need to combat the rising threat of antibiotic drug resistance.”

About Multi-drug Resistant Bacteria

Multi-drug resistant bacteria are an increasing public health crisis. Infections caused by such bacteria result in longer hospital stays and may lead to death. According to the WHO, every year at least 25,000 patients in the European Union alone die from an infection caused by multi-drug resistant bacteria and estimated additional health-care costs and productivity losses are at least 1.5 billion Euros. Bacteria come in two major classes, defined by their appearance when stained to make them visible under a microscope: Gram-positive, which appear as violet blue typically lack the outer membrane found in Gram-negative bacteria, which appear pink after staining.

About Sanofi

Sanofi, a global and diversified healthcare leader, discovers, develops and distributes therapeutic solutions focused on patients’ needs. Sanofi has core strengths in the field of healthcare with seven growth platforms: diabetes solutions, human vaccines, innovative drugs, rare diseases, consumer healthcare, emerging markets and animal health. Sanofi is listed in Paris (EURONEXT: SAN) and in New York (NYSE: SNY). www.sanofi.com

About Rib-X Pharmaceuticals, Inc.

Rib-X Pharmaceuticals is developing broad spectrum antibiotics with superior coverage, safety and convenience to deliver new standards of care for patients with serious infections. The Company’s Nobel Prize winning platform enables a unique understanding of how antibiotics combat infection and has generated an industry leading pipeline spanning all phases of research and clinical development. www.rib-x.com