Inclusion Criteria:
1. Histologically confirmed muscle-invasive urothelial carcinoma of the bladder, with clinical stage cT2-4aN0M0.
2. Medically suitable for radical cystectomy as assessed by the multidisciplinary team.
3. Expected survival of at least 18 months.
4. Estimated glomerular filtration rate (eGFR) ≥60 mL/min.
5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
6. No prior systemic chemotherapy, immunotherapy, targeted therapy, or antibody-drug conjugate therapy for bladder cancer.
7. Adequate organ and marrow function, including hemoglobin ≥90 g/L, absolute neutrophil count ≥1.5 × 10\^9/L, platelet count ≥100 × 10\^9/L, potassium 3.5-5.5 mmol/L, ALT and AST ≤1.5 × upper limit of normal, total bilirubin ≤1.5 × upper limit of normal, and left ventricular ejection fraction ≥50%.
8. Ability to understand and willingness to sign written informed consent.
9. Willingness and ability to comply with study procedures and follow-up.
10. Willingness to provide tumor tissue, urine samples, and peripheral blood samples when required for Patient-derived Tumor-like Cell Clusters (PTC) generation, urinary tumor DNA testing, and biomarker analyses.
11. Female participants of childbearing potential and male participants with partners of childbearing potential must agree to use medically accepted contraception during study treatment and for 6 months after completion of study treatment. Female participants must not be pregnant or breastfeeding.
Exclusion Criteria:
1. Non-urothelial carcinoma histology, or mixed histology with a predominant non-urothelial component, such as small cell carcinoma or adenocarcinoma.
2. Evidence of distant metastatic disease on imaging.
3. Uncontrolled or clinically significant comorbid illness, including but not limited to uncontrolled infection, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina, clinically significant arrhythmia, interstitial lung disease, severe chronic gastrointestinal disease associated with diarrhea, or psychiatric/social conditions that may limit compliance or increase study risk.
4. Known hypersensitivity or allergy to any study treatment, or history of autoimmune disease.
5. Prior exposure to systemic immunotherapy or antibody-drug conjugate therapy, including but not limited to anti-CTLA-4, anti-PD-1, anti-PD-L1, or anti-PD-L2 antibodies.
6. Receipt of a live attenuated vaccine or occurrence of severe infection within 1 month before enrollment.
7. Use of systemic corticosteroids or other systemic immunosuppressive therapy within 2 weeks before enrollment, or expected need for systemic immunosuppressive therapy during the study.
8. Active or symptomatic viral hepatitis or other chronic liver disease, or known human immunodeficiency virus infection.
9. Active tuberculosis.
10. Any other condition that, in the opinion of the investigator, makes the participant unsuitable for this study.
