Validation of the protein kinase Pf CLK3 as a multistage cross-species malarial drug target

Abstract

The requirement for next-generation antimalarials to be both curative and transmission-blocking necessitates the identification of previously undiscovered druggable molecular pathways. We identified a selective inhibitor of the Plasmodium falciparum protein kinase PfCLK3, which we used in combination with chemogenetics to validate PfCLK3 as a drug target acting at multiple parasite life stages. Consistent with a role for PfCLK3 in RNA splicing, inhibition resulted in the down-regulation of more than 400 essential parasite genes. Inhibition of PfCLK3 mediated rapid killing of asexual liver- and blood-stage P. falciparum and blockade of gametocyte development, thereby preventing transmission, and also showed parasiticidal activity against P. berghei and P. knowlesi. Hence, our data establish PfCLK3 as a target for drugs, with the potential to offer a cure—to be prophylactic and transmission blocking in malaria.

Cdc-Like Kinases (CLKs): Biology, Chemical Probes, and Therapeutic Potential

“…Finally, it has been reported that inhibition of CLK3 in Plasmodium falciparum ( Pf CLK3) represents a promising approach for the treatment of malaria via preventing the splicing of essential parasite genes. It has been demonstrated that CLK3 inhibition can kill multiple species of malaria parasites at the blood stage and at the liver-stage and block transmission of the parasite to mosquitoes [ 130 , 131 ]. Another indication where CLK inhibition could be therapeutically relevant is Legionellosis, where CLK inhibition (by TG003) was demonstrated to reduce Legionella growth within mouse macrophages [ 132 ].…”

“…The compound Lead-30 as well as its precursor, the screening hit TCMDC-135051 ( Figure 30 ), were published very recently [ 130 , 131 ]. Both TCMDC-135051 and Lead-30 inhibit Pf CLK3 in Plasmodium falciparum (IC 50 = 40 nM and 19 nM, respectively).…”

Development of Potent and Selective PfCLK3 Inhibitors Based on GSK-TCMDC151 as a New Class of Antimalarials

“…Antimalarial Set (TCAMS) resulted in the discovery of TCMDC-135051 (1, Figure 1), a compound with nM activity against PfCLK3 in in vitro kinase assays and sub µM parasiticidal activity in blood stage P. falciparum (Figure 1). 13 Subsequent studies revealed that TCMDC- 7-Azaindoles are a widely studied pharmacophore incorporated in several therapeutic agents. 14 Kinases are the predominate target with the 7-azaindole moiety generally interacting at the ATP binding site within the kinase hinge region.…”

Development of Potent and Selective PfCLK3 Inhibitors Based on GSK-TCMDC151 as a New Class of Antimalarials

“…Screening of ~25,000 compounds including all 13,533 compounds of the Tres Cantos Antimalarial Set (TCAMS) resulted in the discovery of TCMDC-135051 (1, Figure 1), a compound with nM activity against PfCLK3 in in vitro kinase assays and sub µM parasiticidal activity in blood stage P. falciparum (Figure 1). 13 Subsequent studies revealed that TCMDC-135051 rapidly killed P. falciparum at the trophozoite to schizont stages as well as preventing the development of stage V gametocytes and inhibition the development of liver stage parasites. Our recent studies have therefore validated PfCLK3 as a target with the potential to deliver a curative treatment, be transmission blocking and act as a prophylactic target.…”

“…SAR1 corresponding to analogues 8a-c,13 and 16 were designed to examine the effect of the N-diethyl group of ring-A on antimalarial activity. In analogue 8a, the N-diethyl group was replaced with N-dimethyl group to investigate the effect of alkyl group size and molecular lipophilicity.…”