LAUSR

494Background: Activation of FGFR signaling is involved in a variety of malignancies including advanced urothelial cancer (UC). Rogaratinib is an oral pan-FGFR kinase inhibitor. We report here the results from a phase I expansion cohort in UC patients prescreened for FGFR1-3 mRNA expression levels and activating mutations. (NCT01976741) Methods: Patients with advanced urothelial carcinomas were selected based on high FGFR1-3 mRNA expression in biopsy specimens. Selected patients were treated with rogaratinib 800mg twice daily until tumour progression, untolerable toxicity, or withdrawal. Tumor response was assessed by RECIST, v1.1. Adverse events were reported using CTCAE v4.03 criteria. Results: A total of 219 UC patients were prescreened for FGFR1-3 mRNA expression levels and FGFR3 activating mutations, with 99 samples (45%) found to be FGFR-positive. Of those, 87% of samples were positive for FGFR3 mRNA, 5% for FGFR1 mRNA and 8% were double FGFR mRNA-positive (FGFR1/2, 1/3 or 2/3). Frequency of FGFR3 a...