WebGilead Sciences, Inc. (/ ˈ ɡ ɪ l i ə d /) is an American biopharmaceutical company headquartered in Foster City, California that focuses on researching and developing antiviral drugs used in the treatment of HIV/AIDS, hepatitis B, hepatitis C, influenza, and COVID-19, including ledipasvir/sofosbuvir and sofosbuvir.