e16552 Background: Recent drug approvals in the 1L treatment (tx) setting have expanded options for pts with la/mUC. It is important to understand the economic burden of these novel therapies within the current tx landscape. This study estimated first-year cost of care in the US from a Medicare and commercial payer perspective for pts with la/mUC treated with the following 1L tx: enfortumab vedotin (EV) + pembrolizumab (PEM) in platinum-eligible pts, nivolumab (NIV) + platinum-based chemotherapy (PBC) in cisplatin-eligible pts, and 1L PBC with or without avelumab (AVE) 1L maintenance (1LM). Methods: A cost of care model was developed to estimate direct medical care costs in the first year of tx with EV + PEM, NIV + PBC, and PBC with and without AVE 1LM in pts with la/mUC who are eligible for 1L PBC; pts treated with NIV + PBC were eligible for cisplatin. The latest available costs (2023 USD)—including drug acquisition and administration, disease management, adverse event (AE) management, and subsequent therapy (second-line or later line) costs—were calculated based on tx duration, progression-free survival, overall survival, and AE incidence with various therapies. Efficacy and safety data were sourced from key published trials (EV-302, CheckMate-901, JAVELIN Bladder 100) and product prescribing information. Results: Estimated first-year costs per treated pt are shown in the Table. Cost per treated pt was estimated to range between $56,952 to $438,660 and $90,918 to $457,390 for Medicare and commercial payers, respectively, with the highest cost for EV+PEM and the lowest for PBC only. Drug acquisition costs in the 1L represented the majority of the costs except PBC, for which subsequent tx and administration costs represented the largest cost component. Conclusions: Costs per treated pt were lower for PBC with AVE 1LM than for EV+PEM and NIV+PBC. As value-based oncology care is becoming increasingly important in the US, comprehensive understanding of costs across different tx options and sequences can facilitate informed tx choice. [Table: see text]