Discovery of 3-(5′-Substituted)-Benzimidazole-5-(1-(3,5-dichloropyridin-4-yl)ethoxy)-1H-indazoles as Potent Fibroblast Growth Factor Receptor Inhibitors: Design, Synthesis, and Biological Evaluation

Fibroblast growth factor receptor (FGFR) represents an attractive oncology target for cancer therapy in view of its critical role in promoting cancer formation and progression, as well as causing resistance to approved therapies. In this article, we describe the identification of the potent pan-FGFR inhibitor (R)-21c (FGFR1-4 IC₅₀ values of 0.9, 2.0, 2.0, and 6.1 nM, respectively). Compound (R)-21c exhibited excellent in vitro inhibitory activity against a panel of FGFR-amplified cell lines. Western blot analysis demonstrated that (R)-21c suppressed FGF/FGFR and downstream signaling pathways at nanomolar concentrations. Moreover, (R)-21c provided nearly complete inhibition of tumor growth (96.9% TGI) in NCI-H1581 (FGFR1-amplified) xenograft mice model at the dose of 10 mg/kg/qd via oral administration.