Malaria is a devastating disease that kills nearly half a million people each year. Although a vaccine has recently been approved, its efficiency is limited and, together with increasing resistance to nearly all antimalarial drugs, the success of malaria elimination is threatened. New antimalarials with novel modes of action therefore urgently need to be developed. We aim to block the egress and invasion of Plasmodium falciparum parasites from human red blood cells (RBCs) thereby stopping parasite proliferation and symptomatic disease. A screen of the Medicines for Malaria Venture Pathogen Box identified several compounds that inhibited egress and invasion in vitro (Dans et al, IJP, 2020). From this screen, three compounds were selected for further characterisation: egress inhibitor MMV-A, and invasion inhibitors, MMV-B and MMV-C. To identify their targets, we attempted to select for parasites that were resistant to these compounds and to then find the genetic adaptations responsible for resistance. No resistance could be raised to MMV-A, however, as the compound resembles a cysteine inhibitor and blocks egress leaving parasites trapped within the old RBC, we reasoned MMV-A may inhibit SERA6, a key protease involved in egress. We have additionally shown the inhibitor also blocks the activity of falcipain-2A (a cysteine protease involved in both egress and haemoglobin digestion). Genome sequencing of parasites resistant to MMV-B revealed its target might be a serine protease involved in invasion. We are currently confirming this by introducing the resistance mutations into wild-type parasites with CRISPR-Cas9 to determine if the mutations confer resistance. We also aim to derive the molecular structure of MMV-B with the recombinant serine protease to design more potent inhibitors. Similarly, parasites resistant to MMV-C have been successfully selected and target identification is underway. Analogs of all compounds are currently being designed and tested to improve their potency and pharmacokinetic properties.