BACKGROUND: Alterations in the gene encoding fibroblast growth factor receptor 
(FGFR) are common in urothelial carcinoma and may be associated with lower 
sensitivity to immune interventions. Erdafitinib, a tyrosine kinase inhibitor of 
FGFR1-4, has shown antitumor activity in preclinical models and in a phase 1 
study involving patients with FGFR alterations.
METHODS: In this open-label, phase 2 study, we enrolled patients who had locally 
advanced and unresectable or metastatic urothelial carcinoma with prespecified 
FGFR alterations. All the patients had a history of disease progression during 
or after at least one course of chemotherapy or within 12 months after 
neoadjuvant or adjuvant chemotherapy. Prior immunotherapy was allowed. We 
initially randomly assigned the patients to receive erdafitinib in either an 
intermittent or a continuous regimen in the dose-selection phase of the study. 
On the basis of an interim analysis, the starting dose was set at 8 mg per day 
in a continuous regimen (selected-regimen group), with provision for a 
pharmacodynamically guided dose escalation to 9 mg. The primary end point was 
the objective response rate. Key secondary end points included progression-free 
survival, duration of response, and overall survival.
RESULTS: A total of 99 patients in the selected-regimen group received a median 
of five cycles of erdafitinib. Of these patients, 43% had received at least two 
previous courses of treatment, 79% had visceral metastases, and 53% had a 
creatinine clearance of less than 60 ml per minute. The rate of confirmed 
response to erdafitinib therapy was 40% (3% with a complete response and 37% 
with a partial response). Among the 22 patients who had undergone previous 
immunotherapy, the confirmed response rate was 59%. The median duration of 
progression-free survival was 5.5 months, and the median duration of overall 
survival was 13.8 months. Treatment-related adverse events of grade 3 or higher, 
which were managed mainly by dose adjustments, were reported in 46% of the 
patients; 13% of the patients discontinued treatment because of adverse events. 
There were no treatment-related deaths.
CONCLUSIONS: The use of erdafitinib was associated with an objective tumor 
response in 40% of previously treated patients who had locally advanced and 
unresectable or metastatic urothelial carcinoma with FGFR alterations. 
Treatment-related grade 3 or higher adverse events were reported in nearly half 
the patients. (Funded by Janssen Research and Development; BLC2001 
ClinicalTrials.gov number, NCT02365597.).