Design and synthesis of mechanism-based cysteine protease inhibitors and pro-apoptotic 1,4-benzodiazepines

Chagas' disease is an incapacitating illness that afflicts 16–18 million people, killing 21,000 each year in the Americas. Patients infected with Trypanosoma cruzi who develop the chronic phase of the disease become progressively sick and ultimately die, typically from cardiac failure. Currently there is no satisfactory treatment for Chagas' disease. Malaria is also one of the most important infectious diseases worldwide, as over one million people die each year from infections caused by Plasmodium falciparum. Further complicating the treatment of malaria is the increasing resistance to available drugs. There is a great need to develop new chemotherapy for these diseases, and the targeting of essential cysteine proteases of T. cruzi and P. falciparum has shown to be a promising approach.; This work describes the design, synthesis, and evaluation of small molecule inhibitors of parasitic cysteine proteases. A focused library of peptidomimetic vinyl sulfonyl inhibitors was synthesized and shown to contain potent irreversible inhibitors of cruzain, the major cysteine protease of T. cruzi. Structure-activity relationships with cruzain were determined. Many compounds displayed increased activity against T. cruzi in whole-cell assays, and several were completely trypanocidal in nature. A general relationship between inhibitor hydrophobicity (as measured by clogP) and trypanocidal activity was also uncovered and shown to be independent of structure. Similar compounds were tested against falcipain-2, the best characterized and most important of the three major cysteine proteases of P. falciparum. Several inhibitors of falcipain-2 and P. falciparum were shown to have IC₅₀ values in the low-nanomolar range. Structure-activity relationships with both the enzyme and the parasite were identified.; Cytotoxicity is an important mechanism for the management of autoimmune diseases, such as systemic lupus erythematosus (SLE), and is important in virtually all cancer treatments. The novel benzodiazepine Bz-423 has been identified by Prof. G. D. Glick as a pro-apoptotic agent with great potential in the treatment of such diseases. This work describes the design, synthesis and evaluation of a series of analogs of Bz-423. These benzodiazepines were useful in determining structural correlates of pro-apoptotic activity, and are currently being used to facilitate target identification studies.