Discovery of 6‑Formylpyridyl Urea Derivatives as Potent Reversible-Covalent Fibroblast Growth Factor Receptor 4 Inhibitors with Improved Anti-Hepatocellular Carcinoma Activity

Fibroblast growth factor receptor 4 (FGFR4) has been considered as a potential anticancer target due to FGF19/FGFR4 mediated aberrant signaling in hepatocellular carcinoma (HCC). Several FGFR4 inhibitors have been reported, but none have gained approval. Herein, a series of 5-formyl-pyrrolo[3,2-b]pyridine-3-carboxamides and a series of 6-formylpyridyl ureas were characterized as selective reversible-covalent FGFR4 inhibitors. The representative 6-formylpyridyl urea 8z exhibited excellent potency against FGFR4^WT, FGFR4^V550L, and FGFR4^V550M with IC₅₀ values of 16.3, 12.6, and 57.3 nM, respectively. It also potently suppressed proliferation of Ba/F3 cells driven by FGFR4^WT, FGFR4^V550L, and FGFR4^V550M, and FGFR4-dependent Hep3B and Huh7 HCC cells, with IC₅₀ values of 1.2, 13.5, 64.5, 15.0, and 20.4 nM, respectively. Furthermore, 8z displayed desirable microsomal stability and significant in vivo efficacy in the Huh7 HCC cancer xenograft model in nude mice. The study provides a promising new lead for anticancer drug discovery directed toward overcoming FGFR4 gatekeeper mutation mediated resistance in HCC patients.