Phosphonoformic acid is phosphoric acid with one hydroxy group replaced by a carboxylic acid group. It is used as the trisodium salt as an antiviral agent for the treatment of cytomegalovirus retinitis and as an alternative to ganciclovir for AIDS patients undergoing antiretroviral therapy who cannot tolerate ganciclovir due to haematological toxicity. It functions as an antiviral drug, a sodium-dependent Pi-transporter inhibitor, a HIV-1 reverse transcriptase inhibitor, and a geroprotector. It is a one-carbon compound, a member of phosphonic acids and carboxylic acids, and is functionally related to phosphonic acids and formic acid. It is the conjugate acid of phosphonatoformate and phosphonoformate(2-).
