Yearly, malaria kills 0.5 million people and infects over 300 million individuals. Few enzymes are unambiguous targets of approved antimalarials, so new high-value metabolic targets and their inhibitors are needed. Many clinically approved antibacterial and anticancer agents target DNA topoisomerases. While the community has lacked pure and stable malarial topoisomerases to work with, there are intriguing hints from preliminary data that clinically-approved antimalarials, such as pyronaridine, may inhibit malaria topoisomerases. A three-year NIH-funded research program has allowed our team to express large quantities of stable malaria topoisomerases, to setup robust assays for Plasmodium falciparum topoisomerase II and related enzymes, and to obtain the first x-ray crystal structure of a malarial topoisomerase II. With these resources, in Aim 1, we will start a thorough exploration of cell-active antimalarials to identify front-runner PfTopoII inhibitors for optimizaton.
In Aims 2 and 3, iterative medicinal chemistry will be guided by inhibition of enzyme and cell proliferation, target validation, PK-PD studies, safety evaluations, and activity against different stages of the parasite life-cycle, all to help deliver an antimalarial preclinical candidate. Based on our previous experiences, learnings, and success with malarial dihydroorotate dehydrogenase (DHODH) inhibitors, we are confident in our ability to develop antimalarials directed at P. falciparum and P. vivax topoisomerases that have clinical potential.
Widespread drug resistance in malaria parasites necessitates continuous discovery of high-value drug targets and their inhibitors. Previously, the investigator, in his own laboratory and as a part of larger drug discovery teams, has helped understand clinically useful antimalarial drugs, identified new drug targets, and synthesized nanomolar level inhibitors with appropriate pharmaceutical properties. One of these is currently a clinical candidate in human tests. The present proposal describes a new technical and operational approach to develop the first knowledge-based inhibitors against malaria parasite toposiomerase II.
