PURPOSE: Here, we report results of the first phase I study of erdafitinib, a 
potent, oral pan-FGFR inhibitor.
PATIENTS AND METHODS: Patients age ≥18 years with advanced solid tumors for 
which standard antineoplastic therapy was no longer effective were enrolled 
(NCT01703481). Parts 2 to 4 employed molecular screening for activating FGFR 
genomic alterations. In patients with such alterations, two selected 
doses/schedules identified during part 1 dose-escalation [9 mg once daily and 10 
mg intermittently (7 days on/7 days off), as previously published (Tabernero JCO 
2015;33:3401-8)] were tested.
RESULTS: The study included 187 patients. The most common treatment-related 
adverse events were hyperphosphatemia (64%), dry mouth (42%), and asthenia 
(28%), generally grade 1/2 severity. All cases of hyperphosphatemia were grade 
1/2 except for 1 grade 3 event. Skin, nail, and eye changes were observed in 
43%, 33%, and 28% of patients, respectively (mostly grade 1/2 and reversible 
after temporary dosing interruption). Urothelial carcinoma and 
cholangiocarcinoma were most responsive to erdafitinib, with objective response 
rates (ORR) of 46.2% (12/26) and 27.3% (3/11), respectively, in 
response-evaluable patients with FGFR mutations or fusions. All patients with 
urothelial carcinoma and cholangiocarcinoma who responded to erdafitinib carried 
FGFR mutations or fusions. Median response duration was 5.6 months for 
urothelial carcinoma and 11.4 months for cholangiocarcinoma. ORRs in other tumor 
types were <10%.
CONCLUSIONS: Erdafitinib shows tolerability and preliminary clinical activity in 
advanced solid tumors with genomic changes in the FGFR pathway, at two different 
dosing schedules and with particularly encouraging responses in urothelial 
carcinoma and cholangiocarcinoma.