Cysteine protease inhibitors effective for in vivo use

A method of treating medical conditions characterized by extralysosomal cathepsin B, cathepsin L or both comprising therapeutically administering to a medical patient a therapeutically effective amount of a compound of the formula:

• ##STR8## wherein B is H or an amino acid blocking group for the N-terminal amino acid nitrogen;
• R.sub.1 is a protected or unprotected .alpha.-amino acid side chain on the P.sub.2 amino acid radical and is selected such that the P.sub.2 amino acid radical is the radical of an .alpha.-amino acid selected from the group consisting of unsubstituted and substituted phenylalanine (Ph), leucine (Leu), tyrosine (Tyr) and valine (Val;
• R.sub.2 is a protected or unprotected .alpha.-amino acid side chain on the P.sub.1 amino acid radical, and is selected such that the P.sub.1 amino acid radical is the radical of an .alpha.-amino acid selected from the group consisting of substituted and unsubstituted alanine (Ala), arginine (Arg), aspartic acid (Asp), glutamic acid (Glu), histidine (His), homophenylalanine (HPhe), phenylalanine (Phe), ornithine (Orn), serine (Ser) and threonine (Thr);
• X is a fluorine-free leaving group selected from the group consisting of phenoxy, substituted phenoxy and heterophenoxy;
• E and G are atoms more electronegative than carbon and bonded to the peptide chain by a double bond when they are the same atom or bonded to the peptide chain by a single bond when each is a separate atom;
• and
• D is hydrogen, methyl or a substituted methyl;
• or a pharmaceutical salt thereof.