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Idenix Begins Proof-of-Concept Study of HCV Protease Inhibitor IDX320

SUMMARY: Idenix Pharmaceuticals announced last week that it has started a 3-day proof-of-concept study of its experimental hepatitis C virus (HCV) protease inhibitor IDX320. As previously reported, researchers presented data at the recent EASL conference showing that IDX320 showed good anti-HCV activity in laboratory studies and had good pharmacokinetic and safety profiles in animals and HCV negative volunteers. If the latest study produces favorable results, the company expects to test IDX320 and its investigational HCV polymerase inhibitor IDX184 as a combination regimen.

Below is an excerpt from a recent Idenix press release describing the drugs and the new study.

Idenix Pharmaceuticals Initiates Proof-of-Concept Study for Protease Inhibitor IDX320 in Hepatitis C Patients

Cambridge, Mass. -- June 10, 2010 -- Idenix Pharmaceuticals, Inc. (Nasdaq: IDIX), a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases, today announced that it has initiated a 3-day proof-of-concept study of IDX320, a protease inhibitor for the treatment of hepatitis C virus (HCV) infection, under a Clinical Trial Application (CTA). The study is evaluating IDX320 in treatment-naive hepatitis C genotype 1-infected patients.

"The potent and multi-genotypic activity demonstrated in vitro, as well as the favorable pharmacokinetics observed in healthy volunteers, suggests a promising profile for further development of IDX320," said Jean-Pierre Sommadossi, PhD, chief executive officer of Idenix. "The landscape for combination development in HCV is evolving quickly. Assuming favorable results from the IDX320 proof-of-concept study, we plan to discuss with regulatory agencies a direct-acting antiviral combination strategy with IDX320 and IDX184, our HCV nucleotide polymerase inhibitor."

Douglas Mayers, MD, Idenix's chief medical officer commented, "We are encouraged by the results seen to date with IDX320 and are hopeful that future clinical studies will allow us to continue advancing this program with the ultimate goal of treating a wide range of patients infected with HCV."

The proof-of-concept trial in HCV-infected patients is a Phase I/II randomized, parallel-arm, double-blind, placebo-controlled study evaluating the safety and antiviral activity of IDX320 in treatment-naive adult patients infected with chronic hepatitis C. The study will evaluate four doses of IDX320, ranging from 50 to 400 mg once-per-day, administered for three days. Each cohort of the study will evaluate eight patients randomized six to IDX320 and two to placebo.

About IDX320

IDX320, a macrocyclic HCV protease inhibitor, is an inhibitor of NS3/4A proteases from genotypes 1a, 1b, 2a and 4a (IC50 values from 0.8 to 1.9 nM), as well as from genotype 3a (IC50=23 nM). IDX320 did not inhibit nine tested cellular proteases (IC50 > 10 uM) in vitro, suggesting high selectivity. IDX320 bound tightly to the HCV protease enzyme with a long dissociation half-life (> 9 hours). After single 2 mg/kg oral doses of IDX320 in two animal species, favorable bioavailability and a long plasma half-life were observed, with substantial plasma concentrations 24 hours post dose. Comparable drug exposure was confirmed in healthy volunteers (n=6) receiving a single 200 mg oral dose. Further, no significant in vitro inhibition of human drug metabolizing enzymes, CYP450s and UGT1A1, by IDX320 suggests low potential for drug-drug interactions in patients.

About IDX184

IDX184 is a novel, liver-targeted nucleotide prodrug of 2'-methyl guanosine monophosphate, which includes Idenix's proprietary liver-targeting technology. This technology enables the delivery of nucleoside monophosphate to the liver, leading to the formation of high levels of nucleoside triphosphate, potentially maximizing drug efficacy and limiting systemic side effects with low, once-daily dosing. IDX184 in combination with pegylated interferon and ribavirin has demonstrated a generally favorable safety profile and potent antiviral activity in an ongoing Phase IIa study.

About Idenix

Idenix Pharmaceuticals, Inc., headquartered in Cambridge, Massachusetts, is a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases. Idenix's current focus is on the treatment of patients with chronic hepatitis C infection.

For further information about Idenix, please refer to


Idenix Pharmaceuticals. Idenix Pharmaceuticals Initiates Proof-of-Concept Study for Protease Inhibitor IDX320 in Hepatitis C Patients. Press release. June 10, 2010.






















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