Rib-X Pharmaceuticals Receives $3 Million Milestone Payment from Sanofi

Rib-X Pharmaceuticals, Inc. announced the receipt of a $3 million milestone payment from Sanofi . The payment is the fourth received for milestones achieved following the signing in July 2011 of a worldwide research collaboration and option for license with Sanofi for novel classes of antibiotics resulting from Rib-X's RX-04 program for the treatment of drug resistant Gram-negative and Gram-positive pathogens. The payment, which was part of the pre-specified terms of the agreement, was for the achievement of research-based milestones.

"This milestone payment from Sanofi reflects the continued progress we have made in advancing the RX-04 program toward the clinic," said Mark Leuchtenberger, President and Chief Executive Officer at Rib-X Pharmaceuticals. "This is the fourth milestone we have reached since signing the partnership with Sanofi and we look forward to working hard toward our joint continued success."

Under the RX-04 agreement, Sanofi has the right to license an unlimited number of product candidates targeting a discrete binding site within the ribosome. Rib-X will retain all rights pertaining to their proprietary drug discovery platform, including all other binding sites within the ribosome and all future programs, as well as to any RX-04 compound that Sanofi does not exercise its option to develop during the three-year term of the collaboration. Rib-X has received $22.0 million to date in upfront and milestone payments under the collaboration. Rib-X may receive up to a total of $86.0 million per product for the achievement of research, development and regulatory milestones, up to a total of $100.0 million per product for the achievement of commercial milestones, and tiered percentage royalties up to the low double digits on commercial sales. Rib-X also has the right under the collaboration to co-commercialize one RX-04 product of the Company's choosing with Sanofi in the United States.

The RX-04 program is focused on using a discrete, novel binding site within the ribosome to design and develop new classes of antibiotics to treat some of the most deadly and difficult-to-treat, multi-drug resistant Gram-positive and Gram-negative infections. Using Rib-X's proprietary drug discovery platform, the Company has developed three novel classes of antibiotics in less than three years that bind to this ribosome site.