TY - JOUR T1 - A specific non-bisphosphonate inhibitor of the bifunctional farnesyl/geranylgeranyl diphosphate synthase in malaria parasites JF - bioRxiv DO - 10.1101/134338 SP - 134338 AU - Jolyn E. Gisselberg AU - Zachary Herrera AU - Lindsey Orchard AU - Manuel Llinás AU - Ellen Yeh Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/05/04/134338.abstract N2 - There are multiple validated antimalarial drug targets in isoprenoid biosynthetic pathways. Using a growth rescue screen, we identified MMV019313 as an inhibitor of isoprenoid biosynthesis in Plasmodium falciparum parasites that cause malaria. We demonstrate that the molecular target of MMV019313 is the P. falciparum bifunctional farnesyl and geranylgeranyl diphosphate synthase (FPPS/GGPPS): Both an S228T variant and overexpression of wildtype PfFPPS/GGPPS conferred resistance to MMV019313. MMV019313 also inhibited the activity of purified PfFPPS/GGPPS. PfFPPS/GGPPS has already been validated as an antimalarial drug target since its inhibition by bisphosphonates, a class of drugs that inhibits human FPPS, was shown to clear parasitemia in a mouse malaria model. Though bisphosphonates are clinically used for treating osteoporosis, MMV019313 has significant advantages over bisphosphonates for antimalarial drug development. MMV019313 has superior physicochemical properties compared to charged bisphosphonates that have poor bioavailability and strong bone affinity. We also show that it is highly selective for PfFPPS/GGPPS and showed no activity against human FPPS or GGPPS. Inhibition of PfFPPS/GGPPS by MMV019313, but not bisphosphonates, was disrupted in the S228T variant, demonstrating that MMV019313 and bisphosphonates have distinct modes-of-inhibition against PfFPPS/GGPPS. In addition, we describe two methodological improvements: a more sensitive chemical rescue screen for identifying isoprenoid inhibitors and the first report using chemical mutagenesis for drug resistance selection in Plasmodium. Altogether MMV019313 is the first specific, non-bisphosphonate inhibitor of PfFPPS/GGPPS. Our findings uncover a new small molecule binding site in this important antimalarial drug target and provide a promising starting point for development of Plasmodium-specific FPPS/GGPPS inhibitors.Significance Statement There is an urgent need for antimalarials with novel mechanisms-of-action to circumvent resistance to frontline drugs. Isoprenoid biosynthetic pathways are essential for Plasmodium (malaria) parasites and contain multiple validated drug targets. We identify a new antimalarial compound that inhibits a key branchpoint enzyme in isoprenoid biosynthesis. Our compound has significant advantages over bisphosphonate inhibitors that inhibit the same drug target with improved drug properties and specificity for the Plasmodium enzyme over human homologs. Our findings uncover a new “druggable” site in this important antimalarial drug target and provide a chemical starting point for development of Plasmodium-specific FPPS/GGPPS inhibitors. ER -