Idenix Pharmaceuticals and GSK sign agreement for novel NNRTI for treatment of HIV

Idenix Pharmaceuticals, Inc. and GlaxoSmithKline (GSK) today announced the execution of a license agreement granting GSK exclusive worldwide rights to IDX899.

IDX899 is a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) in Phase II clinical development being developed by Idenix for the treatment of HIV/AIDS. New NNRTIs are needed to address the increasing prevalence of viral resistance and side effects associated with this drug class. To date, IDX899 has demonstrated high potency with low milligram doses, a high barrier to drug resistance, favorable risk/benefit profile, and the convenience of once-a-day administration.

Under the terms of the agreement, GSK will assume all development responsibility and associated costs for IDX899, and Idenix will receive an upfront payment of $34 million and will be eligible to receive up to $416 million in development, regulatory and sales milestones. Furthermore, if IDX899 is successfully developed and commercialized, Idenix will receive double-digit, tiered worldwide royalties.

"GSK, with a well-established HIV franchise and substantial drug development experience, is the ideal collaborator to help maximize the potential of IDX899," said Jean-Pierre Sommadossi, Chief Executive Officer of Idenix. "For Idenix, the significant value created through the license of IDX899 enables us to focus all of our resources on advancing our core strategic HCV assets, which include drug candidates from the three major classes of direct-acting HCV antivirals."

"IDX899 may play a significant role in improving treatment options for people with HIV/AIDS," commented Zhi Hong, Senior Vice President of the Infectious Diseases Centre of Excellence for Drug Discovery (ID CEDD) at GSK. "A once-daily, lower-dose NNRTI that offers an improved drug resistance and pharmacokinetic profile would be valuable to HIV-treating physicians and patients. The preliminary clinical evidence of IDX899 supports this and warrants continued clinical study as part of GSK's growing drug pipeline in HIV."

The $34 million upfront payment by GSK to Idenix was split evenly between cash and the purchase of Idenix common stock at $6.87 per share. The effectiveness of these transactions is subject to approval under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended and other customary closing conditions.

About IDX899

IDX899 is a potent non-nucleoside reverse transcriptase inhibitor (NNRTI) being developed for the treatment of HIV-1. Idenix has advanced IDX899 through a Phase II proof-of-concept study in HIV-1 infected treatment-naive patients that was completed in 2008. In the proof-of-concept study, patients (n=32) receiving once-daily oral administration of IDX899 achieved mean viral load reductions of 1.8 log(10), after seven days of treatment as tested with the Roche Amplicor(R) 1.5 assay. In this study, no treatment-related serious adverse events were reported and no patients discontinued. The most common adverse events observed were dyspepsia, headache and nausea; the rate of these events was similar between IDX899-treated patients and those receiving placebo. Additionally, no patterns in laboratory abnormalities between treatment groups were observed during the treatment period.