Synthesis and biological evaluation of new MET inhibitors with 1,6-naphthyridinone scaffold

A potent and novel Met Inhibitor, 5-((4-((2-amino-3-chloropyridin-4-yl)oxy)-3-fluorophenyl)amino)-3-(4-fluorophenyl)-1,6-naphthyridin-4(1H)-ones (8), was designed and synthesized via a scaffold-hopping strategy of a 2,7-naphthyridinone MET kinase inhibitor 7. Lead compound 8 had good potency (IC₅₀ of 9.8 nM), but unfavorable pharmacokinetic profiles (F = 12%, CL = 5.0 L/h/kg). Systematic structural optimization of compound 8 resulted in 9g (MET, IC₅₀ = of 9.8 nM) with a comparable MET potency to that of compound 2 and a favorable pharmacokinetic profile (F = 63%, CL = 0.12 L/h/kg). Further study of the derivatization of N(1) amine group of 9g led to the discovery of 23a with good MET potency (IC₅₀ of 7.1 nM), promising VEGFR-2 selectivity (3226-fold), and a markedly drug-likeness improvement (F = 57.7%, CL = 0.02 L/h/kg). The excellent VEGFR-2 selectivity and favorable drug-likeness of 23g suggest that the 1,6-naphthyridine moiety could be used as a new scaffold for kinase inhibitor discovery.