The present invention relates to compounds capable of inhibiting and/or decreasing the activity of one or more cathepsins, thereby treating and/or preventing various disease states associated with one or more cysteine proteases including, but not limited to, cathepsins and papain-like cysteine proteases. Disease states treated and/or prevented by the compounds of the invention include, but are not limited to, mammalian parasitic diseases in which the parasite utilizes a critical cysteine protease from the papain family. Examples of parasitic diseases to be treated or prevented by the compounds of the invention include, but are not limited to, toxoplasmosis, malaria, African trypanosomiasis, Chagas disease, leishmaniasis, coccidiosis, giardiosis, cryptosporidiosis or schistosomiasis.
