458 Background: There are currently limited options for patients with locally advanced or metastatic urothelial carcinoma (la/mUC) following progression on platinum chemotherapy and anti-programmed death 1/death-ligand 1 (PD-1/L1) therapy. Further, limited data are available from clinical trials or real-world studies on outcomes in this population. This retrospective analysis investigated clinical outcomes in patients treated with taxane monotherapy, a commonly used and NCCN guideline-recommended option in this setting. Methods: Patients aged ≥18 years with histologically-confirmed diagnosis of la/mUC on or after 2011, ≥2 clinical visits, and sufficient relevant unstructured data were included from the de-identified nationwide Flatiron Health electronic health record-derived database. The study cohort included patients treated with taxane monotherapy (docetaxel, paclitaxel, or nab-paclitaxel) following anti-PD-1/L1 therapy and who have received prior platinum containing chemotherapy. Baseline characteristics, overall survival (OS), real-world progression-free survival (rwPFS) based on clinician documentation of disease status, and real-world response (rwR) based on clinician-confirmed radiologic assessments were reported. Patients were followed until death, data cutoff, or loss to follow up. Results: Among 276 patients treated following anti-PD-1/L1 therapy and who met all of the inclusion/exclusion criteria, 72 were treated with taxanes and also had documented prior platinum chemotherapy. Patients were mostly male (75%) and Caucasian (74%), with a mean age of 73 years. 65% had > 2 sites of metastasis at index (start date of taxane). Post index, median OS = 7.6 months (95% CI 5.2, 14.4) and median rwPFS = 2.9 months (95% CI, 2.4, 4.0). Among the 50 patients with ≥1 rwR assessment, confirmed rwR = 18% (95% CI: 9%, 32%). Conclusions: In the real-world setting, limited responses to taxanes and short duration of PFS and OS were observed in patients with la/mUC previously treated with a platinum and anti-PD-1/L1 therapy. There is a need for more effective therapies to improve clinical outcomes for this patient population.