Substrate Peptidomimetic Inhibitors of P. falciparum Plasmepsin X with Potent Antimalarial Activity.

Plasmepsin X (PMX) is an aspartyl protease that processes proteins essential for Plasmodium parasites to invade and egress from host erythrocytes during the symptomatic asexual stage of malaria. PMX substrates possess a conserved cleavage region denoted by the consensus motif, SFhE (h=hydrophobic amino acid). Peptidomimetics reflecting the P3 -P1 positions of the consensus motif were designed and showed potent and selective inhibition of PMX. It was established that PMX prefers Phe in the P1 position, di-substitution at the β-carbon of the P2 moiety and a hydrophobic P3 group which was supported by modelling of the peptidomimetics in complex with PMX. The peptidomimetics were shown to arrest asexual P. falciparum parasites at the schizont stage by impairing PMX substrate processing. Overall, the peptidomimetics described will assist in further understanding PMX substrate specificity and have the potential to act as a template for future antimalarial design.