LAUSR

4543 Background: The pan-FGFR inhibitor erdafitinib exhibited a robust objective response rate (ORR) and tolerability among pts with FGFR2/3-altered advanced UC in the BLC2001 (NCT02365597) phase 2 study (Siefker-Radtke ASCO 2018 #4503). Here we report a post hoc subgroup analysis to explore efficacy among high-risk pts. Methods: The analysis included 99 BLC2001 pts who received the optimized dose regimen of 8 mg/d continuous (pharmacodynamically guided uptitrated to 9 mg/d per serum phosphate). Results for ORR, duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were analyzed by select baseline variables, with high-risk defined as age >75 y, ECOG PS 2, hemoglobin <10 g/dL, visceral metastases, and 2 or 3 Bellmunt risk factors. Results: Efficacy results (Table) show investigator-assessed ORR >36% and median PFS >5 mo across all subgroups except ECOG PS 2. OS data are immature but generally follow the trend of PFS. With the exception of ECOG 2, there were no differences in G3/4 serious AE proportions by subgroup. Conclusions: The post hoc subgroup findings support that erdafitinib generally provides comparable efficacy in high-risk pts with FGFR-altered advanced UC as the overall population. Clinical trial information: NCT02365597. [Table: see text]