Chemical genetics of Plasmodium falciparum

Malaria caused by Plasmodium falciparum is a disease that is responsible for 880,000 deaths per year worldwide. Vaccine development has proved difficult and resistance has emerged for most antimalarial drugs. To discover new antimalarial chemotypes, we have used a phenotypic forward chemical genetic approach to assay 309,474 chemicals. Here we disclose structures and biological activity of the entire library—many of which showed potent in vitro activity against drug-resistant P. falciparum strains—and detailed profiling of 172 representative candidates. A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins. Phylochemogenetic profiling in several organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans. One exemplar compound displayed efficacy in a murine model. Our findings provide the scientific community with new starting points for malaria drug discovery. Antimalarial arsenal There are still nearly 250 million malaria cases reported annually, over 800,000 fatal, with most deaths being children under 5. The malaria parasite Plasmodium falciparum is notoriously adept at developing drug resistance, and new drugs are urgently needed. Two reports raise hopes that alternatives to artemisinins might be found, by identifying thousands of compounds inhibiting the growth of P. falciparum asexual-stage parasites in red blood cells, many distinct in structure and mechanism from current drugs. Guiguemde et al . present a chemical genomics screen of over 300,000 compounds: the 1,300 'hits' include 561 with good potency and broad therapeutic windows. Gamo et al . screened nearly 2 million compounds from GlaxoSmithKline's chemicals library, finding over 13,500 hits, many active against multidrug-resistant isolates. These studies provide a rich source of potential leads, freely available to academic and industry labs looking for new antimalarials. Here, a library of more than 300,000 chemicals was screened for activity against Plasmodium falciparum growing in red blood cells. Of these chemicals, 172 representative candidates were profiled in detail; one exemplar compound showed efficacy in a mouse model of malaria. The findings provide the scientific community with new starting points for drug discovery.