Drug Repurposing Screen Reveals FDA-Approved Inhibitors of Human HMG-CoA Reductase and Isoprenoid Synthesis That Block Cryptosporidium parvum Growth

Abstract

ABSTRACTCryptosporidiosis, a diarrheal disease usually caused byCryptosporidium parvumorCryptosporidium hominisin humans, can result in fulminant diarrhea and death in AIDS patients and chronic infection and stunting in children. Nitazoxanide, the current standard of care, has limited efficacy in children and is no more effective than placebo in patients with advanced AIDS. Unfortunately, the lack of financial incentives and the technical difficulties associated with working withCryptosporidiumparasites have crippled efforts to develop effective treatments. In order to address these obstacles, we developed and validated (Z′ score = 0.21 to 0.47) a cell-based high-throughput assay and screened a library of drug repurposing candidates (the NIH Clinical Collections), with the hopes of identifying safe, FDA-approved drugs to treat cryptosporidiosis. Our screen yielded 21 compounds with confirmed activity againstC. parvumgrowth at concentrations of <10 μM, many of which had well-defined mechanisms of action, making them useful tools to study basic biology in addition to being potential therapeutics. Additional work, including structure-activity relationship studies, identified the human 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitor itavastatin as a potent inhibitor ofC. parvumgrowth (50% inhibitory concentration [IC50] = 0.62 μM). Bioinformatic analysis of theCryptosporidiumgenomes indicated that the parasites lack all known enzymes required for the synthesis of isoprenoid precursors. Additionally, itavastatin-induced growth inhibition ofC. parvumwas partially reversed by the addition of exogenous isopentenyl pyrophosphate, suggesting that itavastatin reducesCryptosporidiumgrowth via on-target inhibition of host HMG-CoA reductase and that the parasite is dependent on the host cell for synthesis of isoprenoid precursors.