Compounds of general formula (I) or general formula (II) ##STR00001## wherein R.sup.1, P.sub.1, P.sub.2, Q, Y, (X).sub.o, (W).sub.n, (V).sub.m, Z and U are as defined in the specification, are inhibitors of cruzipain and other cysteine protease inhibitors and are useful as therapeutic agents, for example in Chagas' disease, or for validating therapeutic target compounds.