Apr 17, 2019 – NMR Topical Group Meeting

Trichomoniasis is the most prevalent, non-viral sexually transmitted disease in the world. It is caused by the parasitic protozoan, Trichomonas vaginalis, which is incapable of de novo synthesis of purine and pyrimidine rings. Since current 5-nitroimidazole drug treatments show common repeat infections due to increased resistance by the parasite, the development of a novel drug therapy is necessary. Two nucleoside salvage pathway enzymes, adenosine/guanosine nucleoside ribohydrolase and uridine nucleoside ribohydrolase, represent distinct, druggable targets. Inhibition would prevent the production of free nucleobases which the parasite requires. 1H and 19F NMR-based activity assays were used to screen the two enzymes against a 2,000-compound fragment diversity library, resulting in the identification of distinct inhibitor classes. Representative fragments from each structural class were then subjected to two independent counter screens in order to confirm reversible, target-specific inhibition. A ten-fold jump dilution assay proved that the inhibitors were reversible, while the addition of Triton X-100 detergent validated target-specific activity. The NMR-based activity assays were very useful for these counter screens since they provide direct observation of substrate, product, and inhibitor resonances simultaneously. Molecular modeling in combination with structure-activity relationships is being used to guide ongoing medicinal chemistry efforts to discover nM inhibitors of each enzyme for in vitro target validation.