Associations between Varied Susceptibilities to PfATP4 Inhibitors and Genotypes in Ugandan Plasmodium falciparum Isolates

Abstract

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.

Antimalarial drug discovery: progress and approaches

“…Cipargamin was discovered by scientists within the global NGBS consortium (Novartis Institute for Tropical Disease, Genomics Institute of the Novartis Research Foundation, Biomedical Primate Research Centre, and Swiss Tropical and Public Health Institute). Resistance is mediated by mutations in the gene encoding PfATP4 (a protein on the parasite membrane that modulates sodium-proton exchange), suggesting that this is the target of the small molecule 144 – 147 , 62 , 63 . Treatment with cipargamin results in asexual blood-stage parasite rigidification and rapid clearance in vivo.…”

Susceptibility of Ugandan Plasmodium falciparum Isolates to the Antimalarial Drug Pipeline

“…Thus, it is important to determine the drug susceptibilities and genotypic profiles of malaria parasites freshly isolated in malaria-endemic regions where malaria is endemic ( 10 , 11 ). We previously evaluated the ex vivo activities of inhibitors of P. falciparum Na + ATPase 4 (PfATP4) ( 12 ), dihydrofolate reductase (PfDHFR) ( 13 ), and proteasome components ( 14 ) against cultured Ugandan P. falciparum isolates and determined the genetic diversity of the targets of these inhibitors. Ugandan isolates were universally highly sensitive to these lead inhibitors, but modest changes in compound susceptibility were associated with genetic polymorphisms in genes encoding PfATP4, PfDHFR, and the proteasome β2 subunit ( 12 – 14 ).…”