Identification of Potent and Selective Mechanism-Based Inhibitors of the Cysteine Protease Cruzain Using Solid-Phase Parallel Synthesis

Targeted libraries of ketone-based cysteine protease inhibitors were synthesized and screened against cruzain, a cysteine protease implicated in Chagas' disease. A number of single digit nanomolar, low molecular weight inhibitors were identified and optimized for solubility and potency. Specifically, the best inhibitors identified have K(i) values of 0.9-10 nM and molecular weights between 499 and 609 Da. The most effective inhibitor was also found to be greater than 1000-fold selective for cruzain relative to cathepsin B and 100-fold selective for cruzain relative to cathepsin L.