Gilead Sciences is a biopharmaceutical company specializing in the research and development of antiviral drugs for treating HIV/AIDS, hepatitis B, hepatitis C, influenza, and COVID-19. Key products include ledipasvir/sofosbuvir, sofosbuvir, Tamiflu, Vistide, Viread, Hepsera, Sovaldi, and Truvada, addressing critical global health challenges.