ViiV, formed by GSK and Pfizer as an independent firm, progressed ’761 into Phase IIb.

Idenix Pharmaceuticals will receive $20 million from ViiV Healthcare for the achievement of a clinical milestone relating to GSK2248761 (known as ‘761). ViiV is testing the compound in a Phase IIb trial as a treatment of HIV/AIDS.

In February 2009, GlaxoSmithKline (GSK) paid Idenix $34 million for a worldwide license to ‘761, a non-nucleoside reverse transcriptase inhibitor (NNRTI) for HIV/AIDS. In November 2009, GSK and Pfizer created ViiV Healthcare, an independent company focused solely on research, development, and commercialization of HIV medicines.

Idenix says that it has received approximately $60 million in total collaboration-related payments. The firm could earn another $390 million in milestone fees as well as double-digit tiered royalties on worldwide product sales.

ViiV was seeded with 10 approved products from GSK and Pfizer and has five developmental candidates. 1349572 and S/GSK 1265744 are integrase inhibitors in Phase III, UK-453061 is an NNRTI in Phase IIb, and PF-232798 is a CCR5 antagonist in Phase II.

S/GSK 1265744, a once-daily, unboosted treatment, is being developed in partnership with Shionogi. In October the companies reported the start of a Phase III program that includes two studies (SPRING-2 and SAILING) evaluating the drug in treatment-naïve patients and treatment-experienced but integrase-naïve patients.

Idenix is now focused on drug development for hepatitis. On September 3, the FDA placed a clinical hold on the firm’s two lead candidates, IDX184 and IDX320. The decision was made after Idenix notified the FDA that three healthy volunteers in a drug-drug interaction study of IDX184 in combination with IDX320 showed elevated liver function. During follow-up, the liver function tests had reportedly returned to nearly normal levels in all three subjects.

IDX184 is a nucleotide inhibitor, and IDX320 is a protease inhibitor. Idenix expects to submit full data to the FDA from recently completed preclinical and clinical studies including three-month chronic toxicology studies of IDX184, a 14-day study of IDX184 in combination with pegylated interferon/ribavirin, a three-day proof-of-concept study of IDX320 in HCV, and the IDX184 and IDX320 drug-drug interaction study in healthy volunteers to assess next steps in the development of both compounds.

The company has a non-nucleoside inhibitor IDX375 in Phase I development and a discovery-stage program to find an NS5A inhibitor. It has one product on the market: Tyzeka/Sebivo for hepatitis B was co-developed with Novartis, which has worldwide, exclusive commercialization rights.

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