E-64c is an active metabolite of the protease inhibitor E-64d . E-64c inhibits the cysteine proteases cathepsin B, cathepsin H, and papain but not the serine proteases trypsin, chymotrypsin, or elastase. It reduces the autocatalytic activity of the foot-and-mouth-disease virus (FMDV) leader protease when used at concentrations ranging from 0.1 to 1 mg/ml. E-64c reduces infection of HEK293T cells by an HIV-based virus system pseudotyped with severe acute respiratory syndrome coronavirus (SARS-CoV) surface glycoprotein, also known as the spike glycoprotein, in a concentration-dependent manner.
