A G358S mutation in the Plasmodium falciparum Na+ pump PfATP4 confers clinically relevant levels of resistance to cipargamin

Diverse compounds target the Plasmodium falciparum Na+ pump PfATP4, with cipargamin and (+)-SJ733 the most clinically-advanced. In a recent clinical trial for cipargamin, recrudescent parasites emerged, with most having a G358S mutation in PfATP4. Here, we show that PfATP4G358S parasites can withstand micromolar concentrations of cipargamin and (+)-SJ733, while remaining susceptible to antimalarials that do not target PfATP4. The G358S mutation in PfATP4, and the equivalent mutation in Toxoplasma gondii ATP4, decreased the sensitivity of ATP4 to inhibition by cipargamin and (+)-SJ733, thereby protecting parasites from disruption of Na+ regulation. The G358S mutation reduced the affinity of PfATP4 for Na+ and was associated with an increase in the parasite's resting cytosolic [Na+]. However, no defect in parasite growth or transmissibility was observed. Our findings suggest that PfATP4 inhibitors in clinical development should be tested against PfATP4G358S parasites, and that a drug combination approach would be a suitable risk mitigation strategy.