A potent covalent type II inhibitor against FGFR with in vitro and in vivo anti-breast cancer efficacy.

FIIN-4 is a potent, irreversible, type II inhibitor against FGFR (IC50 = 2.6, 2.6, 5.6, 9.2 nM, respectively, against FGFR1-4) whose 4-acrylamidebenzyl moiety covalently modifies FGFR P-loop cysteine in its DFG-out conformation with good target selectivity based on a 456-kinase panel (354 non-mutants kinases) kinome profiling. FIIN-4 effectively inhibits FGF2-induced Erk1/2 phosphorylation in serum-starved D2.A1 murine mammary carcinoma cells (by 100% wtih 18-hr 250 nM pretreatment) and D2.A1 growth in 3D cultures (by 54% at 100 nM) without affecting EGF-dependent Erk phosphorylation or 3D growth of NMuMG murine mammary epithelial cells. Oral administration (25 mg/kg q.o.d.) is efficacious in suppressing the growths of tumors-derived from murine mammary carcinoma 4T1 lung metastases and patient TNBC brain metastases xenografts in mice in vivo with good pharmacokinetics (Tmax = 0.5 hr, T1/2 = 2.4 hr, AUC = 935 h·ng/mL; 10 mg/kg p.o.) and without overt toxicity to the animals.