Redox-active benzylmenadiones against malaria and Schistosoma parasites – ROSaction

Malaria (MAL) and schistosomiasis (SCH) are infectious diseases of poverty of global importance. No vaccines are available and new chemotypes are urgently needed for the development of drugs to fight those two diseases. For MAL, caused by Plasmodium spp. parasites and transmitted by Anopheles spp. mosquitoes, the problem is the spread of resistance to the currently available drugs, including artemisinin-based therapies. Female genital SCH caused by Schistosoma spp, is one of the most common gynecologic conditions of women who live in poverty in Africa and has emerged as one of Africa's most important cofactors in its AIDS epidemic. For SCH, only one drug, praziquantel, is available; but resistant parasites jeopardize the efficacy of cure rates at high infection intensities. To overcome these gaps, we have established a French-Swiss academic consortium, ROSaction with complementary expertise, which includes chemistry, parasitology and yeast genetics, with the aim of developing preclinical candidates of the 3-benzylmenadione (bMD) series: plasmodione (against MAL) and schistodiones (against SCH).
Depending on their chemical substitution pattern, bMDs have highly specific and potent antiparasitic activities on Plasmodium spp., or Schistosoma mansoni worms, both in vitro and in vivo, with no obvious signs of toxicity in mice and in G6PD-deficient red blood cells. The goal of this application is to optimize the discovered early bMD-based leads for each disease model, to improve their pharmacokinetic properties, to validate the respective antiparasitic properties of the optimized compounds in vivo, and to identify the sensitive parasite stages, the drug modes of action and their protein targets.
Mode of action studies conducted by the French teams with P. falciparum and Saccharomyces cerevisiae have indicated that the bMD derivatives are substrates of mitochondrial NADH-dehydrogenases, and that the chemical reduction of the bMD derivatives initiates a redox cycling process that results in the production of reactive oxygen species (ROS). The Swiss applicants of the project have established a strong expertise in antiparasitic drug efficacy testing. They have developed various in vitro and in vivo models for Plasmodium and S. mansoni, which are being used in hit discovery and hit-to-lead development of new antiparasitic agents.
The proposed research program is divided into three work packages (WP).
In WP1, we will synthesize novel 3-benzylmenadione analogues of plasmodione and schistodiones with improved antiparasitic activitiy, selectivity, and pharmacokinetics, and a second generation of activity-based protein profiling (ABPP) probes based on the 3-bMD scaffold. In WP2, the antiparasitic properties and selectivity profile of the molecules synthesized in WP1 will be assessed on P. falciparum and S. mansoni. The results will guide further optimization of the compounds (WP1) and enable mechanistic studies that will be performed in WP3. In WP3, we will investigate the mode of action of the antimalarial plasmodione and search for drug targets and possible mechanism of resistance. Using high throughput approaches in the yeast model, we will identify new targets by extending our screens for PD-resistant and hypersensitive yeast mutants. In parallel, activity-based protein profiling (ABPP) probes (synthesized in WP1) will enable us to capture and identify plasmodione targets in P. falciparum. Candidate drug targets and resistance genes/mutations will be validated in the parasite by genetic constructions. We will study the mode of action of schistodiones using yeast as a model and on the basis of the knowledge acquired in Plasmodium. We aim at providing a molecular understanding on how bMDs kill parasites and what is the basis of their selectivity.