Elucidating the path to Plasmodium prolyl-tRNA synthetase inhibitors that overcome halofuginone resistance

The development of antimalarials against the human liver and asexual blood stages is one of the top public health challenges. Here, the authors report a single-step biochemical assay for the characterization of prolyl-tRNA synthetase inhibitors, and develop high-affinity inhibitors for the enzyme, including elusive triple-site ligands. The development of next-generation antimalarials that are efficacious against the human liver and asexual blood stages is recognized as one of the world's most pressing public health challenges. In recent years, aminoacyl-tRNA synthetases, including prolyl-tRNA synthetase, have emerged as attractive targets for malaria chemotherapy. We describe the development of a single-step biochemical assay for Plasmodium and human prolyl-tRNA synthetases that overcomes critical limitations of existing technologies and enables quantitative inhibitor profiling with high sensitivity and flexibility. Supported by this assay platform and co-crystal structures of representative inhibitor-target complexes, we develop a set of high-affinity prolyl-tRNA synthetase inhibitors, including previously elusive aminoacyl-tRNA synthetase triple-site ligands that simultaneously engage all three substrate-binding pockets. Several compounds exhibit potent dual-stage activity against Plasmodium parasites and display good cellular host selectivity. Our data inform the inhibitor requirements to overcome existing resistance mechanisms and establish a path for rational development of prolyl-tRNA synthetase-targeted anti-malarial therapies.

Automated summary

This article describes a biochemical assay for the development of antimalarials targeted at the prolyl-tRNA synthetase enzyme. High-affinity inhibitors, including triple-site ligands, were developed using this assay. These inhibitors exhibit potent dual-stage activity against Plasmodium parasites and show good cellular host selectivity. This research provides insights for the rational development of prolyl-tRNA synthetase-targeted anti-malarial therapies.