Gilead Sciences Inc. said Japan's Ministry of Health, Labour and Welfare approved Epclusa to treat chronic hepatitis C virus infection.

The drug was approved as a once-daily treatment for adults with chronic hepatitis C virus, or HCV, infection, with or without cirrhosis.

Liver inflammation due to HCV leads to damage and scarring, called cirrhosis. Cirrhosis can be compensated or decompensated, the former meaning the liver remains sufficiently functional despite heavy scarring.

Patients without cirrhosis or with compensated cirrhosis must have undergone direct-acting antiviral therapy for them to take Epclusa. In these patients, Epclusa must be taken for 24 weeks instead of 12, and in combination with antiviral agent ribavirin, which Merck & Co. Inc. markets as Rebetol.

The approval was supported by late-stage trial data in Japanese patients with HCV infection with decompensated cirrhosis. The 51-patient study, called GS-US-342-4019, showed that 92% of participants had no detectable HCV RNA 12 weeks after completing therapy — a measure called SVR12.

Another phase 3 trial, labelled GS-US-342-3921, enrolled 60 patients who have failed direct-acting antiviral therapy. Gilead said 97% of the participants achieved a level of sustained viral response called SVR12 after 24 weeks on Epclusa.

The drug was also well tolerated in both studies.

Epclusa comprises 400 milligrams of sofosbuvir, which Gilead markets in Japan as Sovaldi, and 100 milligrams of velpatasvir, which inhibits a key HCV protein.

Foster City, Calif.-based Gilead is leaning on generics to stem market share erosion for its flagship HCV portfolio, which includes Sovaldi, Harvoni and Epclusa.