Phase III Data Suggests IL28B Genotyping Helps Predict Response to Merck & Co.’s HCV Drug

New analyses of Phase III trial data suggests that identifying HCV patients’ IL28B status and evaluating their initial response to peginterferon alfa-2b and ribavirin (PR) therapy can help predict those who will achieve a sustained virologic response (SVR) when Merck & Co.’s oral protease inhibitor candidate Victrelis® (boceprivir) is subsequently added to the treatment mix.

The new analyses, presented at the International Liver Congress/46^th European Association for the Study of Liver (EASL) annual meeting, coincided with publication in The New England Journal of Medicine of data from the Phase III HCV Respond-2 and HCV Sprint-2 studies evaluating Vectrelis combined with PR in patients who had failed prior PR therapy and who were new to treatment, respectively.  Both trials formed part of the regulatory submissions for Victrelis, which were accepted for accelerated review by both FDA and the EMA in January.

The new data presented at EASL emerged from additional analyses of both the Respond-2 and Sprint-2 studies. In the Sprint-2 treatment-naïve study, patients receiving Victrelis who had good response to PR therapy after the four-week lead-in period achieved SVR rates of 79% over the 48-week treatment period. The SVR rate for patients in the PR therapy control arm who initially responded well to PR therapy was 51%. Among patients with poor response after the four-week lead-in, the SVR rate was 38% for Vicrelis-treated patients in the 48-week treatment arm compared with an SVR rate of 4% in the PR control arm.

In the Respond-2 treatment-failure study, Victrelis-treated patients who responded well after the lead-in PR therapy period achieved SVR rates of 79%. The SVR for patients treated using only PR was 25%. Among patients with poor response after the four-week lead-in, the SVR rate was 34% for those receiving PR plus Victrelis, and 0% for those continuing on just PR therapy.

A prespecified analysis of the Phase III trials in addition showed that IL28B status was also a strong baseline predictor of viral response among Victrelis-treated patients. The data, also presented at EASL, showed that among patients carrying the CC gene allele, 89% of treatment-naive patients and 82% of previously treatment-failure patients had an early response defined as undetectable virus at treatment week eight and were eligible for shorter duration of therapy. Among patients carrying the ‘less favorable’ CT or TT alleles, the early response rates were 52% for the treatment-naive cohort and 48% for the treatment-failure patients.

Primary results from the NEJM-published Respond-2 and Sprint-2 studies showed that among patients who had previously failed treatment, the 48-week SVR rate was 66% for those treated using Victrelis plus PR compared with 21% for patients treated using PR and placebo. Among treatment naive patients the SVR rate was 66% for patients receiving Victrelis plus PR and 38% for the PR therapy cohort.

“Based on new analyses of these studies, identification of a patient’s IL28B status prior to treatment, used in conjunction with a patient’s response after the four-week lead-in period, provided information on the likelihood of achieving SVR when Victrelis was added to standard therapy,” concludes Fred Poordad, M.D., chief of hepatology and liver transplantation at Cedars-Sinai Medical  Center in Los Angeles, and lead author of the HCV Sprint-2 study.