Loriot Y, et al. - In view of the observed antitumor activity of erdafitinib, a tyrosine kinase inhibitor of fibroblast growth factor receptor (FGFR)1–4, in preclinical models and in a phase 1 study including patients with FGFR alterations, researchers conducted this open-label, phase 2 study to assess the safety and efficacy in patients with locally advanced and unresectable or metastatic urothelial carcinoma with prespecified FGFR alterations. Patients were randomly allocated to receive erdafitinib in either an intermittent or a continuous regimen in the dose-selection phase of the study. They set the starting dose at 8 mg per day in a continuous regimen (selected-regimen group) on the basis of an interim analysis, with provision for a pharmacodynamically guided dose escalation to 9 mg. A median of five cycles of erdafitinib was administered to a total of 99 patients in the selected-regimen group. Outcomes revealed an objective tumor response of 40% in correlation with the use of erdafitinib among these patients. The confirmed response rate was 59% in the 22 patients who had undergone previous immunotherapy. Nearly half the patients experienced treatment-related grade 3 or higher adverse events.