Idenix Pharmaceuticals, Inc, a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral and other infectious diseases, reported data for IDX899, a non-nucleoside reverse transcriptase inhibitor (NNRTI) being developed for the treatment of HIV.
In the first dosing cohort of an ongoing phase I/II study, eight HIV-1 infected treatment-naive patients receiving 800 mg of IDX899 once-daily achieved a mean reduction in virus level of 2.01 log (10), or 99 per cent, after seven days of treatment. Additionally, two posters detailing the in-vitro resistance and pharmacokinetic profile in man of IDX899 were presented at the 2008 Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.
"New once-a-day NNRTIs that offer improved resistance and safety profiles over what is currently available would be a valuable asset to HIV-treating physicians," said Dr. Douglas Richman, Professor of Pathology and Medicine, University of California San Diego, and Director of the UCSD Center for AIDS Research. "The early profile of IDX899 shows promise and warrants continued clinical evaluation as a potential HIV therapy."
An ongoing phase I/II clinical trial is evaluating the safety, tolerability and antiviral activity of IDX899. In the first cohort of the study, ten HIV-1-infected treatment-naive patients were randomized 8:2 to receive once-daily 800 mg IDX899 or matching placebo, respectively, for seven days.
Patients receiving once-daily 800 mg of IDX899 achieved a mean and median plasma viral load reduction of 2.01 and 2.11 log(10), respectively, after seven days of treatment. Six out of eight patients achieved a 2 log(10) or greater reduction in viral load with one patient achieving undetectable virus levels (< 50 copies/mL). No serious adverse events were reported in this cohort and no patients discontinued the study. Given the potent antiviral activity and favorable preliminary safety demonstrated at 800 mg once-daily, we will explore sequential cohorts of 400 mg once-daily followed by 200 mg once-daily.
"We are pleased with the safety profile and potency observed with the 800 mg dose of IDX899 in HIV-infected patients and based on these data we will continue to evaluate lower dosing regimens in order to optimise the role of IDX899 in HIV combination therapy," said Douglas Mayers, M.D., chief medical officer, Idenix.
In a preclinical resistance study, IDX899 and other marketed and investigational NNRTIs were compared to evaluate in-vitro genotypic resistance and phenotypic cross-resistance profiles. IDX899 demonstrated potent antiviral activity against established NNRTI-resistant clinical isolates. Compared to efavirenz (Sustiva), the emergence of IDX899-resistant HIV-1 isolates was slower and required several mutations suggesting a higher barrier to resistance for IDX899. The resistance mutations selected in-vitro with IDX899 were different from those selected with efavirenz. Efavirenz appeared to be active against IDX899 resistant viruses and IDX899 remained active against efavirenz-resistant virus containing as many as four NNRTI-resistance mutations.
A phase I study was conducted to evaluate the safety and pharmacokinetics of IDX899 following single escalating (n=65) and multiple (n=20) doses in healthy volunteers. In this study, following once-daily oral administration, IDX899 appeared to be well tolerated at single doses up to 1200 mg and multiple doses up to 800 mg over a seven-day period. No serious adverse events or pattern of laboratory abnormalities were observed. Food enhanced the absorption of IDX899. Additionally, in a single-dose drug-drug interaction study assessing the combination of either 100 or 800 mg IDX899 and 100 mg atazanavir (Reyataz), atazanavir plasma levels were not markedly altered by IDX899.
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 and other infectious diseases. Idenix's current focus is on the treatment of infections caused by hepatitis C virus and HIV.