Repositioning and Characterization of 1-(Pyridin-4-yl)pyrrolidin-2-one Derivatives as Plasmodium Cytoplasmic Prolyl-tRNA Synthetase Inhibitors

11 Jun 2021

Okaniwa M, Shibata A, Ochida A, Akao Y, White KL, Shackleford DM, Duffy S, Lucantoni L, Dey S, Striepen J, Yeo T, Mok S, Aguiar ACC, Sturm A, Crespo B, Sanz LM, Churchyard A, Baum J, Pereira DB, Guido RVC, Dechering KJ, Wittlin S, Uhlemann AC, Fidock DA, Niles JC, Avery VM, Charman SA, Laleu B

ACS Infectious Diseases
PMID: 33929818

Doi: 10.1021/acsinfecdis.1c00020

Photo: Freedom Studio/Shutterstock.com

Prolyl-tRNA synthetase (PRS) is a clinically validated antimalarial target. Screening of a set of PRS ATP-site binders, initially designed for human indications, led to identification of 1-(pyridin-4-yl)pyrrolidin-2-one derivatives representing a novel antimalarial scaffold. Evidence designates cytoplasmic PRS as the drug target. The frontrunner and its active enantiomer exhibited low-double-digit nanomolar activity against resistant () laboratory strains and development of liver schizonts. No cross-resistance with strains resistant to other known antimalarials was noted. In addition, a similar level of growth inhibition was observed against clinical field isolates of and . The slow killing profile and the relative high propensity to develop resistance (minimum inoculum resistance of 8 × 10 parasites at a selection pressure of 3 × IC) constitute unfavorable features for treatment of malaria. However, potent blood stage and antischizontal activity are compelling for causal prophylaxis which does not require fast onset of action. Achieving sufficient on-target selectivity appears to be particularly challenging and should be the primary focus during the next steps of optimization of this chemical series. Encouraging preliminary off-target profile and oral efficacy in a humanized murine model of malaria allowed us to conclude that 1-(pyridin-4-yl)pyrrolidin-2-one derivatives represent a promising starting point for the identification of novel antimalarial prophylactic agents that selectively target PRS.

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