To address this, we undertook this preclinical study to investigate potential resistance mechanisms to FGFR inhibitors in two previously uncharacterised bladder cancer cell lines harbouring FGFR3-fusions, RT4 (FGFR3-TACC3 fusion) and SW780 (FGFR3-BAIP2L1 fusion). The gene discussed is FGFR3; the disease is urinary bladder cancer.