BLU-554 is a potent, orally bioavailable inhibitor of human fibroblast growth factor receptor 4 (FGFR4), with potential antineoplastic activity. Upon oral administration, BLU-554 specifically binds to and blocks the binding of the ligand FGF19 to FGFR4. This prevents the activation of FGFR4, inhibits FGFR4-mediated signaling and leads to an inhibition of tumor cell proliferation in FGFR4-overexpressing cells. FGFR4 is a receptor tyrosine kinase and is involved in tumor cell proliferation, differentiation, angiogenesis, and survival. FGF19 is overexpressed by certain tumor cell types.