Identification of a-azacyclic acetamide-based inhibitors of P. falciparum Na+ pump (PfATP4) with fast-killing asexual blood-stage antimalarial activity by phenotypic screening
Malaria treatments are compromised by drug resistance, creating an urgent need to discover new drugs. Herein, we used a phenotypic high-throughput screening (HTS) platform to identify new antimalarials, uncovering three related pyrrole-, indole-, and indoline-based chemical series with a shared a-azacyclic acetamide core. These compounds showed fast-killing activity on asexual blood-stage Plasmodium falciparum parasites. Biochemical studies revealed that they disrupt parasite pH and Na+ regulation in a manner similar to cipargamin (KAE609), a clinically advanced inhibitor of the P. falciparum Na+ pump (PfATP4). PfATP4, localized to the parasite plasma membrane, is essential for maintaining a low cytosolic Na+ concentration. Resistance selection to the a-azacyclic acetamide analogs SW491 and SW968 resulted in P. falciparum parasites with mutations in PfATP4, and cross-resistance was observed across the a-azacyclic acetamides and KAE609, confirming PfATP4 as the target. PfATP4 is a well-established antimalarial target, and identification of additional PfATP4 inhibitors provides alternative avenues to disrupt its function.