TPS4623 Background: The standard treatment for nonmetastatic MIBC is neoadjuvant cisplatin-based therapy followed by radical cystectomy (RC). However, many patients are ineligible for cisplatin. Immune checkpoint inhibitors (ICIs) have changed the treatment landscape for metastatic urothelial cancer (mUC), including for cisplatin-ineligible patients. Based on these results, ICIs are being explored as neoadjuvant treatment in resectable UC with preliminary data suggesting antitumour activity. ERDA is a Fibroblast Growth Factor Receptor (FGFR) inhibitor, which has shown efficacy in advanced UC with select FGFR2/3 mutations/fusions. ERDA plus cetrelimab demonstrated clinically meaningful activity in patients with newly diagnosed FGFR-altered mUC in the phase 2 NORSE trial. We hypothesize that ERDA plus cetrelimab will improve the pathological complete response (pCR) rate in patients with FGFR+ MIBC who are candidates for RC and are ineligible for or refuse neoadjuvant cisplatin-based therapy. Methods: SOGUG-NEOWIN is a prospective, non-comparative, open label, multicentre, international trial to assess the efficacy of 9 or 12 weeks of neoadjuvant ERDA (cohort 1) or the combination of cetrelimab and ERDA (cohort 2) in patients with MIBC (cT2-Ta N0/1 M0) and FGFR alterations. Key eligibility criteria include ECOG PS 0-1; pure or predominant UC histology; decline or ineligible for cisplatin-based chemotherapy as defined by one of the following criteria: impaired renal function (GFR < 60 mL/min), ≥ grade 2 hearing loss, or ≥ grade 2 peripheral neuropathy; patients are considered fit for cystectomy; no prior FGFR-targeted or anti-PD-(L)1 therapy; no prior systemic therapy, radiation or surgery (except TURBT or biopsies) for bladder cancer; prior BCG was allowed if completed ≥ 6 weeks before initiation of study treatment; no current retinopathy. A total of 45 patients will be allocated to each cohort by a centralized system. Co-primary endpoints are pCR rate and percentage of pathological downstaging response (<ypT2). Secondary endpoints include event-free survival, overall survival, overall response rate, safety, tolerability, and delay to surgery. Biomarkers of response and resistance will be assessed using baseline archival tissues, blood and urine. Quality of life (QoL) will be assessed using FACT-Bl and EQ-5D-5L. Tumour response assessment via PET-MRI will be performed in a subset of patients. The trial is approved in 4 countries. The first patient was included on 31-Jan-2024. This trial would be the first to systematically address whether ERDA ± cetrelimab improves pCR in patients with FGFR-positive MIBC. (EudraCT 2022-002586-15). Clinical trial information: 2022-002586-15.