The team found that adding the treatment to standard therapy with pegylated interpheron alpha plus ribavirin produces a synergistic antiviral effect.
In the study involving 104 patients with HCV genotype 1, 21 patients were given 1500 mg of R1626 twice a day along with peginterferon alpha-2a, commonly known as Pegasys.
Thirty-two patients were given 3000 mg of R1626 twice a day along with peginterferon alpha-2a and the other thirty-one received 1500 mg of R1626 twice a day along with peginterferon alpha-2a and ribavirin.
The rest 20 were given the standard of care treatment of peginterferon alpha-2a with ribavirin.
The research team found that after four weeks, HCV RNA was barely visible in 29 percent of the patients treated with the first treatment, 69 percent in the group receiving second treatment and 74 percent of patients receiving the third treatment.
"The results of the present study show a marked increase in antiviral effect in patients when ribavirin is added to the combination of R1626 and peginterferon alfa-2a," said the authors.
"This phase 2a study has demonstrated a potent reduction in HCV RNA by R1626 and high viral responses with up to 74 percent rapid viral response after 4 weeks of treatment.
"The strong antiviral effect between R1626, peginterferon alfa-2a and ribavirin, suggests that the dose of one or both of these agents could be lowered to improve tolerability without significantly compromising efficacy," the authors added.
Another study shows that, in patients with chronic hepatitis C, the antiviral activity increased with the dosage.
For 14 days, the patients were treated with R1626 orally at twice-daily doses of either 500 mg, 1500 mg, 3000 mg, 4500 mg, or placebo.
"The decreases in HCV RNA from baseline observed with R1626 indicates potent antiviral activity and lack of viral load rebound in the significant majority of patients following 14 days of monotherapy," the authors report.
The reports appear in the August issue of Hepatology, a journal published by John Wiley and Sons on behalf of the American Association for the Study of Liver Diseases.