Fibroblast growth factor receptor (FGFR) belongs to receptor tyrosine kinase (RTK) superfamily. There are four family members of FGFR (FGFR1–4) and the proper regulation of FGFR signaling is essential for a number of cellular processes, such as cell proliferation, migration, and survival. FGFR3 alterations, including FGFR3 activating mutations, FGFR3 fusions, and FGFR3 overexpression, are especially common in bladder cancer. In particular, FGFR3 mutations and fusions have been detected in up to 80% of non-muscle invasive bladder cancer patients and ~10–20% of muscle invasive bladder cancer  patients. In 2019, FDA approved erdafitinib, a selective FGFR inhibitor (FGFRi), for the treatment of locally advanced or metastatic bladder cancer with FGFR2 or FGFR3 alterations