FGFR1 and cholangiocarcinoma: Consistent with laboratory characterization of acquired FGFR2 and FGFR3 resistance mutations in patients with cholangiocarcinoma and urothelial carcinoma, respectively21,24, our study also revealed that across FGFR1–FGFR3, the most common sites for progression-emergent kinase domain mutations are the gatekeeper residues and the molecular brake residues.