Compounds of the formula II: wherein R 1 forms an ethynyl bond and R 2 is H or C 3 -C 6 cycloalkyl which is optionally substituted with one or two substituents independently selected from methyl, CF 3 , OMe or halo; R 3 is C 1 -C 3 alkyl or C 3 -C 6 cycloalkyl, either of which is optionally substituted with one or two methyl and/or a fluoro, trifluoromethyl or methoxy, when R 3 is C 3 -C 6 cycloalkyl it may alternatively be gem subsituted with fluoro; R 4 is methyl or fluoro; m is 0, 1 or 2; E is a bond, A 1 is CH or N, A 2 is CR 6 R 7 or NR 6 , provided at least one of A 1 and A 2 comprises N; n is 0 or 1 such that the ring containing A 1 and A 2 is a saturated, nitrogen-containing ring of 5 or 6 ring atoms; R 6 is H, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 1 -C 3 alkyl-O-C 1 -C 3 alkyl, or when A 2 is C, R 6 can also be C 1 -C 4 alkoxy or F; R 7 is H, C 1 -C 4 alkyl or F or a pharmaceutically acceptable salt, N-oxide or hydrate thereof, have utility in the treatment of disorders characterized by inappropriate expression or activation of cathepsin K, such as osteoporosis, osteoarthritis, rheumatoid arthritis or bone metastases.