Background: Salvage therapy options for aUC following platinum-based chemotherapy and immune checkpoint inhibitors (ICIs) have modest activity. Regorafenib is a multitargeted TKI that targets VEGF and Tie2 receptors among others, which is approved for multiple malignancies. Both VEGF and Tie2 inhibitors have preliminarily exhibited activity in aUC. Hence, a rationale was made to evaluate regorafenib in aUC progressing following chemotherapy. Methods: We conducted a single arm, non-randomized Phase II study (NCT02459119) of regorafenib for aUC following chemotherapy. All patients (pts) started at 120 mg po qd for one cycle (28 days) before escalating to 160 mg po qd in the absence of intolerable regorafenib related toxicities. Pts who had progressed after 1-3 prior chemotherapy regimens and exhibited measurable disease by RECIST 1.1 were selected. The primary objectives was progression free survival at 6 months (PFS-6) and the secondary objectives were objective response rates (ORR), overall survival (OS) and toxicities. PFS6 of ≥20% was considered of interest and the target accrual was 32 evaluable pts. The treatment was continued until progression or intolerable adverse events. Results: We enrolled 17 pts across 3 institutions (UAB, Wayne State and Cleveland Clinic) between May 2015 and May 2019. Of these, 14 patients were male (82%) and the median age was 67 years. Pts received a median of 2 prior therapies including chemotherapy. 9 pts had received a prior ICI. 13 pts (76.5%) experienced treatment related adverse events (AE), and 7 pts (41.2%) had grade 3 toxicities including–anemia, thrombocytopenia, myalgia, hypophosphatemia, abdominal pain and fatigue. Treatment was discontinued for patients who suffered grade 3 myalgia and abdominal pain. There were no treatment related deaths. 3 patients attained PFS6 (18%) who also displayed minor regressions and 1 of them had received a prior ICI. Conclusions: Although the trial was halted for slow accrual, regorafenib appeared to demonstrate activity in heavily pretreated pts with aUC who had received chemotherapy or ICI. Further evaluation may be warranted in less heavily pretreated pts and in combination with rational agents with non-overlapping toxicities. Clinical trial information: NCT02459119