June 20 , 2011 Lexington, MA –- Concert Pharmaceuticals, Inc. today announced that it has achieved a milestone in its strategic alliance with GlaxoSmithKline (GSK) for its HIV protease inhibitor (HIV-PI) development program, resulting in a $4 million milestone payment to Concert. The strategic alliance with GSK was formed in 2009. In the HIV development program a number of deuterium modified-versions of atazanavir were evaluated preclinically, and a subset was selected for further testing in early human clinical studies. Based on the human data, CTP-298 was selected as the lead compound for further development. Concert expects the program will advance into initial clinical efficacy trials in HIV-positive patients next year.

“We are very pleased by the continuing progress of our alliance with GSK and their support of CTP-298’s clinical development,” said Roger Tung, Ph.D., President and CEO of Concert Pharmaceuticals. “For this contractual milestone our lead candidate met certain clinical criteria that included improved pharmacokinetics, as compared to atazanavir in healthy human subjects. Achieving those criteria demonstrates the potential of selective deuterium substitution to clinically improve compound performance and represents a significant advancement in our program.”

The goal of the HIV-PI development program is to create a potent, once-daily protease inhibitor that does not require ritonavir as a pharmacokinetic boosting agent, and that can be dosed as part of a fixed dose combination with other HIV replication inhibitors. Eliminating the need for ritonavir, which is currently co-administered per label with all once-daily HIV protease inhibitors to increase their blood levels, could provide significant advantages over current standard-of-care. To this end, Concert prepared deuterium-modified versions of atazanavir utilizing its DCE Platform™ (deuterium chemical entity platform). Extensive preclinical testing and comparative human pharmacokinetic studies enabled the identification of CTP-298 as an agent that retains atazanavir’s antiviral potency but improves on its pharmacokinetic behavior, in particular raising C24 plasma concentrations.