GS-4321 (Medivir)

GS-4321 is an investigational monoclonal antibody being developed by Gilead Sciences, in collaboration with Medivir, for the treatment of chronic hepatitis delta (CHD). It functions as a neutralizing antibody that specifically targets the pre-S1 domain of the hepatitis B virus (HBV) large surface protein. Because the hepatitis delta virus (HDV) is a satellite virus that utilizes the HBV envelope proteins to infect liver cells, blocking the pre-S1 domain prevents the virus from binding to the sodium taurocholate cotransporting polypeptide (NTCP) receptor on hepatocytes, thereby inhibiting viral entry. GS-4321 is currently being evaluated in Phase 1/2 clinical trials (e.g., NCT07096193) to assess its safety, tolerability, pharmacokinetics, and antiviral activity when administered via subcutaneous or intravenous routes.