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HCV Polymerase Inhibitor INX-189 Gets FDA Fast-Track Status, TMC649128 Enters Phase 1a Trial

The development of direct-acting antiviral agents active against hepatitis C virus (HCV) continues at a rapid pace. Two pharmaceutical companies this month announced progress in the development of investigational HCV polymerase inhibitors. Inhibitex said that it's candidate INX-189 has received "Fast Track" designation from the U.S. Food and Drug Administration (FDA), which allows for accelerated review and approval. Sweden's Medivir announced the start of the first human trial of its drug, TMC649128, in healthy volunteers.

INX-08189, or INX-189 for short, is a potent guanosine nucleotide polymerase inhibitor for the treatment of chronic hepatitis C, according to a press release issued by Inhibitex.

Under the FDA Modernization Act of 1997, the "Fast Track" program is designed to facilitate the development and expedite the review of new drugs that are intended to treat serious or life-threatening conditions, and that demonstrate the potential to address unmet medical needs.

The characteristics of INX-189 that contributed to its Fast Track status include a high genetic barrier to resistance, activity against multiple HCV genotypes, and once-daily oral dosing, the company said.

"The FDA’s Fast Track designation for INX-189 is reflective of its unique features and the need for novel antiviral drugs that demonstrate the potential to provide better clinical outcomes and improved tolerability for the millions of individuals suffering from chronic hepatitis C infection," said Joseph Patti, Chief Scientific Officer and Senior Vice President of Research and Development at Inhibitex.

The company has reported interim data from the first 2 cohorts of an ongoing Phase 1b clinical trial of INX-189, and expects to complete this trial by the end of March.

The full Inhibitex press release is available online. For additional information about the company, visit


Medivir AB announced earlier this months that it has started a Phase 1a clinical trial of TMC649128 for the treatment of chronic hepatitis C.

TMC649128, which is being developed in collaboration with Tibotec Pharmaceuticals, is a nucleoside NS5B polymerase inhibitor that has already demonstrated an attractive pre-clinical profile, according to a Medivir press release. In laboratory studies TMC649128 demonstrated activity against multiple HCV genotypes and had a high genetic barrier to resistance.

The new Phase 1a study is a double-blind, randomized, placebo-controlled single-ascending dose trial to assess the safety, tolerability, and pharmacokinetics of TMC649128 in healthy HCV-uninfected volunteers.

"We are extremely excited to see TMC649128, our first HCV nucleoside inhibitor, move into clinical development," said Bertil Samuelsson, CSO of Medivir. "We view nucleoside inhibitors as cornerstone components of future HCV treatment paradigms in combination with directly acting antiviral agents and a TMC649128 component could set them apart from other HCV drug classes."

The full press release is available online. For more information about Medivir, visit the company’s website at



Inhibitex, Inc. Inhibitex Receives Fast Track Designation for INX-189 for the Treatment of Chronic Hepatitis C Infections. Press release. February 11, 2011.

Medivir Announces Start of Phase 1a Trial of the Hepatitis C Polymerase Inhibitor TMC649128. Press release. February 10, 2011.