Structure-Based Design and Optimization of Novel, Potent and Selective Covalent FGFR2/3 Inhibitors with a Tricyclic Core.

Fibroblast growth factor receptors 2 and 3 (FGFR2/3) are attractive therapeutic targets in multiple human cancers. Here, we report the discovery of a series of tricyclic 1-(4-amino-5-ethynyl-8,9-dihydropyrazino[1',2':1,5]pyrrolo[2,3-d]pyrimidin-7(6H)-yl)prop-2-en-1-one derivatives as novel covalent FGFR2/3 inhibitors through structure-based design and optimization. The lead compound, KNT-0919, potently suppressed FGFR2- or FGFR3-driven Ba/F3 cells (IC50 = 1.1 nM and 0.20 nM), with reduced activity against Ba/F3-FGFR1 cells (IC50 = 17.1 nM) and parental Ba/F3 cells (IC50 > 1000 nM). In a panel of 416 kinases, KNT-0919 selectively inhibited FGFR2/3 kinases, including clinically relevant mutants. Covalent modification of FGFR2/3 was confirmed by mass spectrometry and X-ray crystallography. Functionally, KNT-0919 selectively suppressed the proliferation of FGFR2-dependent cancer cell lines, dose-dependently inhibited FGFR2 downstream signaling, and induced apoptosis in an FGFR2-dependent manner. Moreover, KNT-0919 demonstrated favorable oral bioavailability (56%) in rats and achieved significant tumor growth inhibition in an SNU-16 gastric cancer xenograft model.