Related: GS-7977-formally PSI-7977 Viral Relapse Seen Post Treatment In ELECTRON Study
Hard-to-Treat Group Trips Up HCV Drug
A promising hepatitis C medication has run into a roadblock in a small group of hard-to-treat patients, according to the drug's maker.
The drug, dubbed GS-7977, was being used with a standard drug, ribavirin, but without the other standby, pegylated interferon, to treat 10 patients with genotype one virus, according to Gilead Sciences.
But after a good early response in eight patients, six of them relapsed within a month of finishing the 12-week therapy. The remaining two have not relapsed but have just finished treatment, the company said.
In a conference call, company officials said the results were unexpected but will not derail the drug, which has been shown to be safe and effective in some groups of hepatitis C patients.
The patients who relapsed were so-called "null responders" who had previously been treated with the standard ribavirin and interferon, but who had not cleared the virus.
They are a "challenging patient population to cure," said Norbert Bischofberger, PhD, Gilead's chief scientific officer.
The drug is also being tested, using the same approach, in patients who have not previously been treated and in patients with genotypes two and three of the virus, who are easier to treat.
Preliminary data in the genotype two and three patients, presented last year, showed that 10 of 10 had been cured. Data on the treatment-naive patients is to be presented next month.
The finding in the null responders has "answered an important question," according to Gilead CEO John Milligan, PhD, and hints that in some patient groups more than one direct-acting agent may be needed for a cure.
Bischofberger told those on the conference call that it's also possible, in his opinion, that the 12-week duration of treatment was simply not long enough to knock the virus down.
The direct-acting agents, which target elements of the virus itself, are a new departure in hepatitis C therapy, which for years has relied on boosting the immune system overall using ribavirin and interferon.
GS-7977 is a nucleotide analog polymerase inhibitor; other drugs, both approved and under development, attack the viral protease enzyme or other targets.
But the advent of the direct-acting agents has sparked a push to stop using interferon, which is difficult for many patients to tolerate, and some studies have suggested that a combination of the new agents would work well without the older drug.
In this case, exactly why such a high percentage of the patients relapsed remains unclear, Milligan said, reminding those on the call that the data are "preliminary results" in only eight patients.