Gilead said Thursday that in a clinical trial, two groups of patients who were treated with
GS-7977 had undetectable levels of the hepatitis C virus after four weeks. The patients took GSI-7977 and ribavirin, an older treatment for the virus, and they had either failed to respond to previous therapies or had not been treated before. In November, Pharmasset Inc. — which developed the drug and was acquired by Gilead in January — said 100 percent of patients in a study responded to the drug.