Investigation of Covalent Warheads in the Design of 2-Aminopyrimidine-based FGFR4 Inhibitors.

Abstract

Covalent kinase inhibitors are rapidly emerging as a class of therapeutics with clinical benefits. Herein we report a series of selective 2-aminopyrimidine-based fibroblast growth factor receptor 4 (FGFR4) inhibitors exploring different types of cysteine-targeting warheads. The structure-activity relationship study revealed that the chemically tuned warheads α-fluoro acrylamide, vinylsulfonamide, and acetaldehyde amine were suitable as covalent warheads for the design of selective FGFR4 inhibitors. Compounds <b>6a</b>, <b>6h</b>, and <b>6i</b> selectively suppressed FGFR4 enzymatic activity with IC₅₀ values of 53 ± 18, 45 ± 11, and 16 ± 4 nM, respectively, while sparing FGFR1/2/3. X-ray crystal structure and MALDI-TOF studies demonstrated that compound <b>6h</b> bearing the α-fluoro acrylamide binds to FGFR4 with an irreversible binding mode, whereas compound <b>6i</b> with an acetaldehyde amine binds to FGFR4 with a reversible covalent mode. <b>6h</b> and <b>6i</b> might provide some fundamental structural information for the rational design of new selective FGFR4 inhibitors.