Viral relapse has been observed in the majority of hepatitis C genotype 1 patients with a prior "null" response to an interferon (IFN)-containing regimen in the ongoing ELECTRON study within four weeks of completing 12 weeks of treatment with GS-7977 plus ribavirin (RBV), according to Gilead Sciences.

GS-7977, a nucleotide analog polymerase inhibitor, is currently being studied for the treatment of chronic hepatitis C.

Six out of the ten patients randomised in the ELECTRON study have experienced viral relapse.

A further two patients, who have only reached the two week post-treatment point, have not relapsed.

Data is currently only available for eight of the ten patients.

Gilead Sciences executive vice president of research and development and chief scientific officer Norbert Bischofberger, PhD, said: "These data answer an important question about the use of GS-7977 and ribavirin for the treatment of genotype 1 null responder patients, suggesting that additional direct acting antivirals may be necessary to effectively treat this patient population.

"We will continue to explore a number of therapeutic approaches to address this significant unmet medical need, including combinations with other oral antivirals," Bischofberger added.

Currently, many ongoing Phase 2 and Phase 3 studies are investigating the safety and efficacy of the compound with and without RBV and/or pegylated interferon (Peg-IFN) in patients with genotypes 1-6 who are treatment naïve, treatment experienced, or have had a "null" response to Peg-IFN.

The data from the QUANTUM study with 25 patients assessing GS-7977 plus RBV for 12 weeks in genotype 1 naïve patients will be announced at the end of Q1, 2012.

The ELECTRON study findings will be reported in the second quarter of 2012, followed by data on GS-7977 and RBV treatment for 24 weeks from an arm of the QUANTUM study to be reported in Q3, 2012.

The genotype 2 and 3 data from the ELECTRON study were presented at the 62nd annual meeting of the American Association for the Study of Liver Diseases, the company said.

Headquartered in California, US, Gilead Sciences is a biopharmaceutical company that discovers, develops and commercialises innovative therapeutics to advance the care of patients suffering from life-threatening diseases worldwide.