Human Polo-like Kinase Inhibitors as Antiplasmodials

Protein kinases have proven to be a very productive class of therapeutic targets, and over 90 inhibitors are currently in clinical use primarily for the treatment of cancer. Repurposing these inhibitors as antimalarials could provide an accelerated path to drug development. In this study, we identified BI-2536, a known potent human polo-like kinase 1 inhibitor, with low nanomolar antiplasmodial activity. Screening of additional PLK1 inhibitors revealed further antiplasmodial candidates despite the lack of an obvious orthologue of PLKs in Plasmodium. A subset of these inhibitors was profiled for their in vitro killing profile, and commonalities between the killing rate and inhibition of nuclear replication were noted. A kinase panel screen identified PfNEK3 as a shared target of these PLK1 inhibitors; however, phosphoproteome analysis confirmed distinct signaling pathways were disrupted by two structurally distinct inhibitors, suggesting PfNEK3 may not be the sole target. Genomic analysis of BI-2536-resistant parasites revealed mutations in genes associated with the starvation-induced stress response, suggesting BI-2536 may also inhibit an aminoacyl-tRNA synthetase.

Automated summary

Protein kinases have been successful therapeutic targets, especially for cancer treatment, and there is potential to repurpose them as antimalarials. A study discovered BI-2536, a potent inhibitor of human polo-like kinase 1, showing nanomolar antiplasmodial activity. Screening of other PLK1 inhibitors identified more potential antimalarials, and a shared target, PfNEK3, was identified through kinase panel screening. However, there may be additional targets involved as distinct signaling pathways were disrupted by different inhibitors. Genomic analysis of BI-2536-resistant parasites suggested potential inhibition of an aminoacyl-tRNA synthetase.