Idenix Announces Positive Clinical Data

Idenix Pharmaceuticals, Inc. recently announced results from an ongoing Phase IIb study of IDX184 in combination with pegylated interferon and ribavirin (PegIFN/RBV). Of the first cohort of 31 patients enrolled in the study, those who achieved an eRVR (n=18), defined as having undetectable levels of virus at 4 weeks and 12 weeks, were randomized to stop treatment after either an additional 12 weeks (n=9) or 36 weeks (n=9) of PegIFN/RBV. Of the 9 patients who completed their 12-week PegIFN/RBV extended treatment phase, 100% of patients (4/4) in the 100-mg arm and 80% of patients (4/5) in the 50-mg arm achieved a sustained virologic response 4 weeks after the completion of treatment (SVR4).

Patients who did not achieve an eRVR automatically entered the 36-week PegIFN/RBV extended treatment phase, which is ongoing. To date, the side effect profile of IDX184 combined with PegIFN/RBV is consistent with that of PegIFN/RBV alone.

“We are encouraged by the initial SVR results from the Phase IIb program, which have confirmed previous data showing that IDX184 is a potent nucleotide inhibitor with a profile supporting its potential role as a key component of all-oral direct-acting antiviral (DAA) combination regimens for HCV,” said Ron Renaud, President and Chief Executive Officer of Idenix. “We look forward to initiating interferon-free DAA combination studies in the near term.”

In July 2011, the company initiated enrollment of treatment-naive genotype 1 HCV-infected patients into a randomized, double-blind, parallel group Phase IIb clinical trial of IDX184. The study features two treatment arms, either 50 mg or 100 mg of IDX184 administered once-daily for 12 weeks, each arm in combination with PegIFN/RBV. Response-guided therapy was used to complete an additional 12 or 36 weeks of PegIFN/RBV treatment. Study objectives include safety and tolerability, and antiviral activity endpoints.

Idenix also announced positive data from a 3-day proof-of-concept study evaluating IDX719, an NS5A inhibitor, in 64 treatment-naïve, genotype 1, 2, 3, or 4 HCV-infected patients.

Genotype 1 patients were randomized to receive placebo, 25-mg QD (once-daily), 50-mg QD, 50-mg BID (twice-daily), or 100-mg QD for 3 days. Genotype 2, 3, or 4 patients were randomized to receive placebo, 50-mg BID or 100-mg QD for 3 days.

IDX719 was well tolerated with no serious adverse events reported. Treatment with IDX719 exhibited potent pan-genotypic activity across genotypes. More detailed findings are expected to be presented at a scientific meeting in the second half of 2012.

“We are pleased to demonstrate the first clinical validation of IDX719 in patients in a multiple-dose study with robust activity across multiple HCV genotypes,” said Douglas Mayers, MD, Chief Medical Officer of Idenix. “Given these promising findings, we look forward to initiating a Phase II combination study of IDX719 with IDX184 by the end of this year.”

IDX184 is an unpartnered, novel, liver-targeted nucleotide prodrug of 2′-methyl guanosine, 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. In the ongoing Phase IIb clinical trial, IDX184 has been well tolerated with a side effect profile similar to that of PegIFN/RBV. In the first cohort of 31 patients, at 12 weeks in an intent-to-treat analysis, the complete early virologic response (< 25 IU/mL at 12 weeks) was 93% for the 100-mg IDX184 arm (n=15) and 81% for the 50-mg IDX184 arm (n=16) of the study. The company completed enrollment of a second cohort of 36 additional patients this past May.

IDX719 is an NS5A inhibitor with low picomolar, pan-genotypic antiviral activity in vitro. In 36 healthy volunteers, IDX719 was safe and well tolerated at single doses of 5 to 100 mg as well as multiple doses of 100 mg for 7 days. Single doses of IDX719 demonstrated potent pan-genotypic antiviral activity in 18 genotype 1, 2, or 3 HCV-infected patients, with greater than 3 log10 viral load reductions achieved in the 100-mg dose arm.

Idenix Pharmaceuticals, Inc., headquartered in Cambridge, MA, 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 HCV. For more information, visit www.idenix.com.