Single-domain antibodies that compete with the natural ligand fibroblast growth factor block the internalization of the fibroblast growth factor receptor 1

► Recombinant antibodies for FGFR1 were isolated from a llama naïve library in VHH format. ► These antibodies compete with the natural ligand FGF-2 for the same epitope on FGFR1. ► The antibody competition inhibits the FGF-2-dependent internalization of FGFR1.