N-substituted peptidyl nitriles as cysteine cathepsin inhibitors

A compound of the formula

• wherein R1 is aryl or biaryl;
• R2 is aryl-lower alkyl, biaryl-lower alkyl, benzo-fused cycloakyl, cycloalkyl-lower alkyl, bicycloalkyl-lower alkyl, aryloxy-lower alkyl, or aryl-C2-C7-alkyl in which C2-C7-alkyl is interrupted by Y;
• Y is O, S, SO, SO2, CO or NR6;
• R3 is hydrogen or lower alkyl;
• or
• R2 and R3 combined are C2-C7-alkylene or C2-C7-alkylene interrupted by Y;
• R4 is hydrogen or lower alkyl;
• R5 represents the grouping
• —X—Ar—Q—Z
• in which X is lower alkylene, lower alkyleneoxy or C2-C1-alkylene interrupted by Y;
• Ar is monocyclic carbocyclic or monocyclic heterocyclic arylene;
• Q is a direct bond, lower alkylene, or thio- or oxy-lower alkylene:
• Z is hydroxy, acyloxy, carboxyl, or carboxyl derivatized as a pharmaceutically acceptable ester or amide;
• or Z is 5-tetrazolyl;
• Y is O, S, SO, SO2 or NR6;
• and R6 is hydrogen, lower alkyl or aryl-lower alkyl;
• or a pharmaceutically acceptable salt thereof.