RSV604 is used as an investigational antiviral agent targeting respiratory syncytial virus (RSV) infections. It functions as a fusion inhibitor, preventing the virus from entering host cells by blocking the fusion of the viral envelope with the cell membrane. This mechanism makes it particularly effective in reducing viral spread, especially in early stages of infection. RSV604 has been explored for use in high-risk populations such as infants, elderly individuals, and immunocompromised patients who are more susceptible to severe RSV disease. It has shown potential in clinical settings for both treatment and prophylaxis, particularly in hospitalized patients with lower respiratory tract infections caused by RSV. Its development supports efforts to address the lack of effective antiviral therapies for RSV, which remains a major cause of pediatric and geriatric respiratory illness.