Patients who achieved PR harbored the following aberrations: FGFR2 Y376C (n = 1), FGFR3 A393E (n = 1), and FGFR3-TACC3 fusions (n = 2)...Urothelial carcinomas (n = 6) harbored FGFR3 aberrations exclusively (point mutations and fusions)...Confirmed partial responses were seen in 8% (90% CI, 3% to 18%) and were observed only in patients whose tumors harbored FGFR1-3 point mutations or fusions. All objective responses and PR or SD for > 6 months were seen in patients with FGFR mutations or fusions.