The recent emergence of multi-drug-resistant (MDR) strains of Mycobacterium tuberculosis (M.TB), the bacterium which causes tuberculosis, has prompted serious efforts in tuberculosis research. MDR-TB has rendered the standard drugs ineffective, thus the current research focuses on the discovery of new and efficacious drugs to treat MDR strains of M. tuberculosis. Unfortunately, current drugs are powerless against MDR-TB strains. Novel compounds with unique mechanisms of action are necessary to develop effective drugs. An aim of this project is to synthesize a compound which has the capability of determining the target protein of a specific lead compound whose effectiveness as a novel anti-TB agent is promising. The first compound to be synthesized is a photoaffinity analogue of SB-RA-2001, a taxane lead which shows efficacy against MDR strains of M. tuberculosis. Some types of taxanes such as the anticancer drug, Taxol®, are known to stabilize tubulin polymerization. Many taxanes with a low or negligible cytotoxicity were tested for their efficacy as novel anti-TB agents because there is a homology between tubulin, the target of cancer drugs, and FtsZ, a protein which plays an essential role in bacterial cell division. SB-RA-2001 was discovered to be a highly promising lead compound. In order to test the hypothesis that the unique mechanism of action of SB-RA-2001 is, in fact, interference with FtsZ polymerization, photoaffinity labeling method will be used to identify the target protein. A photoaffinity analogue will be synthesized by attaching a benzophenone group to the "C-2" position of SB-RA-2001.
The other aim is to design and synthesize a mimic of SRI-3072, a lead compound developed by the Southern Research Institute, which is claimed to be a potential anti-TB agent by acting as an FtsZ inhibitor. We have designed a novel SRI-3072 mimic bearing a trisubstituted benzimidazole template taken from two known tubulin polymerization inhibitors, albendazole and thiabendazole. GTPase assay will be performed on the novel SRI-3072 mimic to test its ability to inhibit FtsZ GTPase activity. Synthesis of these compounds involves general organic synthetic chemistry procedures: reactions are monitored by layer chromatography and quenched after completion. Extractions are performed with the separatory funnel and the crude product is dried and purified by silica gel column chromatography. Solvents are removed by rotary-evaporator and under vacuum. Characterization of the products includes measurements of 1H NMR and 13C NMR, mass spectrometry, melting point, and optical rotation.
This study was supported in part by the Simons Foundation and the Institute of Chemical Biology and Drug Discovery at Stony Brook University.