Safety and Efficacy of 9MW2821 in the Treatment of High-risk Non-muscle-invasive Bladder Cancer (NMIBC)

Inclusion Criteria: * Age≥18 years old before signing the informed consent. * Subjects must have previously failed to at least one kind of intravesical therapy, including but not limited to BCG, gemcitabine, etc. * Subjects refuse or are intolerant to BCG therapy. * Subjects must have completed a standard TURBT surgery within 6 weeks before the first dose of the study drug and have no evidence of residual tumors in the surgical field. * Tumor tissue samples from TURBT must be provided (≥5 slides), along with relevant pathological reports. * Histological and pathological diagnosis of urothelial carcinoma (with a major component \>50%) , with the confirmation of no-muscle invasion. * Subjects must be categorized as high-risk NMIBC * Subjects refuse or are intolerant to radical cystectomy. * Clinical non-metastatic bladder cancer (N0, M0) determined by CT scan. * Adequate function of heart, bone marrow, liver, and kidney. * ECOG 0-1 * Subjects must be willing to take highly effective contraception during the study and 180 days after the last dose of 9MW2821 (a negative serum pregnancy test result within ≤7 days before enrollment for the female). Exclusion Criteria: * History of muscle invasive or metastatic bladder cancer. * History of other malignancies within 3 years. * Other systemic anti-cancer therapies within 3 weeks before the first dose of the study drug. * Surgery (such as TURBT) or radiotherapy for bladder lesions within 2 weeks before the first dose. * Hypersensitivity reactions to certain components of 9MW2821 or similar drugs. * Persistence of adverse reactions caused by prior anti-tumor therapy before the first dose, does not recover to grade 1 and below, according to NCI-CTCAE v5.0. * Active systemic infections that require treatments within 7 days before the first dose. * Severe cardiovascular diseases within 6 months before the first dose. * History of allogeneic hematopoietic stem cell transplantation or organ transplantation. * History of autoimmune diseases. * Serum virology tests: positive results for HBsAg or HBcAb, with positive HBV-DNA copies (≥500IU/mL); positive HCV-Ab results, with positive HCV-RNA results; positive HIV-Ab results. * Prior treatment with drugs targeted Nectin-4 or MMAE-conjugated ADC.