February 22, 2012 — The majority of genotype 1 null responder patients with hepatitis C virus (HCV) infection have undergone relapse after treatment with the promising uridine nucleotide analog polymerase inhibitor GS-7977 (Gilead Sciences, Inc).
Six of 8 patients relapsed within 4 weeks of receiving a 3-month course of once-daily GS-7977 (previously known as PSI-7977, Pharmasset) in combination with ribavirin but without the other standby, pegylated interferon. All had previously failed standard therapy with interferon/ribavirin.
An additional 2 patients enrolled in this study group of the ongoing Electron study have not yet relapsed at 2 weeks posttherapy.
The findings represent a setback for GS-7977, which, as previously reported by Medscape Medical News, has been linked to a 100% cure rate in treatment-naive patients with HCV genotypes 2 and 3.
In a conference call, company officials said that the results were "unexpected," but will not derail the drug.
Null responders represent "a challenging patient population to cure," said Norbert Bischofberger, PhD, Gilead's chief scientific officer, noting that additional direct-acting antivirals or an extended duration of therapy may be needed to achieve better outcomes.
Mitchell L. Shiffman, MD, refused to speculate on the findings, telling Medscape Medical News that in his opinion, "there is not enough information to comment upon."
Dr. Shiffman is a leading hepatologist at the Liver Institute of Virginia, part of the Bon Secours Hampton Roads health system.
"We were looking forward to having an oral regimen and are very disappointed in the lack of response to GS-7977 among HCV genotype 1 null responders," Susan Simon, president and founder of the Hepatitis C Association, told Medscape Medical News, concurring that perhaps an extended duration of treatment or a combination of direct-acting antivirals may be key.
Simon is also a patient, having been with HCV in 1991, who believes she acquired HCV in 1966. She has genotype 1a HCV and has failed treatment repeatedly.
"There are many HCV drugs currently in phase 3 trials, and we hope that they will find a combination of drugs for those of us who are null responders, so that we can have a good chance of clearing the virus like everyone else," Simon added. "We hope that researchers will continue to strive for a cure for us hard-to-treat patients: there are many of us out there."
Data from HCV genotype 1 treatment-naive patients receiving GS-7977/ribavirin in the QUANTUM study will be presented next month.