Among novel compounds under recent investigation as potential new antimalarial drugs are three independently developed inhibitors of the
Plasmodium falciparum
P-type ATPase (PfATP4): KAE609 (cipargamin), PA92, and SJ733. We assessed
ex vivo
susceptibilities to these compounds of 374 fresh
P. falciparum
isolates collected in Tororo and Busia districts, Uganda from 2016-2019. Median IC
50
s were 65 nM for SJ733, 9.1 nM for PA92, and 0.5 nM for KAE609. Sequencing of
pfatp4
for 218 of these isolates demonstrated many non-synonymous single nucleotide polymorphisms; the most frequent mutations were G1128R (69% of isolates mixed or mutant), Q1081K/R (68%), G223S (25%), N1045K (16%) and D1116G/N/Y (16%). The G223S mutation was associated with decreased susceptibility to SJ733, PA92 and KAE609. The D1116G/N/Y mutations were associated with decreased susceptibility to SJ733, and the presence of mutations at both codons 223 and 1116 was associated with decreased susceptibility to PA92 and SJ733. In all of these cases, absolute differences in susceptibilities of wild type (WT) and mutant parasites were modest. Analysis of clones separated from mixed field isolates consistently identified mutant clones as less susceptible than WT. Analysis of isolates from other sites demonstrated presence of the G223S and D1116G/N/Y mutations across Uganda. Our results indicate that malaria parasites circulating in Uganda have a number of polymorphisms in PfATP4 and that modestly decreased susceptibility to PfATP4 inhibitors is associated with some mutations now present in Ugandan parasites.
Single nucleotide polymorphisms in Plasmodium falciparum V type H+ pyrophosphatase gene (pfvp2) and their associations with pfcrt and pfmdr1 polymorphisms