Discovery of Novel Inhibitors of Ornithine Decarboxylase in Trypanosoma brucei: Development and Application of a Targeted High-Throughput Screening Program
Human African Trypanosomiasis (HAT), caused by the eukaryotic parasite Trypanosoma brucei, is a serious health problem in much of central Africa. The only validated molecular target for treatment of HAT is ornithine decarboxylase (ODC), which catalyzes the first step in polyamine metabolism. Herein, we describe the optimization of high throughput screening protocols at St. Jude Children's Research Hospital as well as the development of a high-throughput compatible assay for ODC. We have used this assay to screen 316,114 unique molecules to identify potent and selective inhibitors of ODC. This effort identified four novel families of ODC inhibitors, including the first inhibitors selective for the parasitic enzyme. These compounds display unique binding modes, suggesting the presence of allosteric regulatory sites on the enzyme. Docking of a subset of these inhibitors, coupled with mutagenesis, also supports the existence of these allosteric sites.