A compound of the formula (II) wherein one of R.sup.1 and R.sup.2 is halo and the other is H or halo; R.sup.3 is --C.sub.1-C.sub.5 straight or branched chain, optionally fluorinated, alkyl or --CH.sub.2CR.sup.5C.sub.3-C.sub.4-Cycloalkyl; R.sup.4 is H; R.sup.5 is H, C.sub.1-C.sub.2 alkyl, C.sub.1-C.sub.2 haloalkyl, hydroxyl, OC.sub.1-C.sub.2alkyl, fluoro; R.sup.6 is a stable, optionally substituted, monocyclic or bicyclic, carbocycle or heterocycle wherein the or each ring has 4, 5 or 6 ring atoms and 0 to 3 hetero atoms selected from S, O and N; Rb is haloalkyl; Rc is H or C.sub.1-C.sub.4 alkyl; and pharmaceutically acceptable salts, hydrates or N-oxides thereof have utility in the treatment of disorders characterised by inappropriate expression or activation of cathepsin K, such as osteoporosis, osteoarthritis, rheumatoid arthritis or bone metastases. ##STR00001##