Dihydroorotate Dehydrogenase (DHODH) and Topoisomerase Inhibitors
While a number of drugs are available to treat and prevent malaria, the threat of resistance to our most efficacious antimalarials drives the search for novel drugs and drug targets. Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) is a high-value target for malaria parasites because humans have pyrimidine salvage pathways, but parasites do not. With a key partner, Meg Phillips at UTSWMC, our lab has focused on lead optimization of a diverse set of heterocycles using PfDHODH assays, parasite inhibitor responses, lack of toxicity to mammalian cells, and metabolic stability studies. Previous work identified the PfDHODH inhibitor DSM265, which is currently in Phase 2 human clinical trials. Our lab has also pioneered the use of in vitro resistance studies, combined with whole genome sequencing, to identify targets of promising new parasite-specific inhibitors.
Topoisomerases play a key role in transcription, replication, DNA repair, and cell division. The requirement of topoisomerases for normal cell function and growth has been exploited to treat bacterial infections and cancer. However, the corresponding malarial enzymes remain largely unexplored, largely due to challenges of heterologous expression of malarial enzymes in functional form and limited availability of genetic tools to understand the roles of topoisomerases in Plasmodium falciparum. Our lab has utilized a wheat germ cell-free protein expression system, CRISPR-Cas9, and small molecule screens to characterize malaria topoisomerase biochemistry.
White, J. & Rathod, P. K. Indispensable malaria genes. Science 360, 490–491 (2018).
Phillips, M. A. et al. A long-duration dihydroorotate dehydrogenase inhibitor (DSM265) for prevention and treatment of malaria. Science Translational Medicine 7, (2015).
Mudeppa, D. G., Kumar, S., Kokkonda, S., White, J. & Rathod, P. K. Topoisomerase II from human malaria parasites: Expression, purification, and selective inhibition. Journal of Biological Chemistry 290, 20313–20324 (2015).