Discovery of Naphthyridinone Derivatives as Selective and Potent PKMYT1 Inhibitors with Antitumor Efficacy

PKMYT1 is a crucial regulator of the cell cycle, particularly involved in the G2/M transition through the inhibitory phosphorylation of CDK1, and is a promising therapeutic target for cancer therapy. Data mining in the Roche kinome screen database identified a hit characterized by 100% PKMYT1 inhibitory activity at a 10 μM concentration, which was further validated with a PKMYT1 enzymatic assay showing double-digit nanomolar potency. The hit featured a quinolinone central core and a phenol headgroup. The replacement of the problematic phenol headgroup with an indazole moiety induced a flip in the kinase hinge cysteine and glycine residues, resulting in a series of derivatives with enhanced potency, superior kinome selectivity, and no GSH flag. Further structural fine-tuning led to the discovery of compound 36, a novel, selective, and potent PKMYT1 inhibitor with favorable oral pharmacokinetic profiles and promising in vivo antitumor efficacy.