This is a multicenter, randomized, Double-blind phase III study to determine the efficacy and safety of intravesical SHR-1501 combined with Bacillus Calmette Guerin (BCG) versus Placebo Combined with BCG in patients with high-risk BCG-naive Papillary-Only non-muscle-invasive bladder cancer (NMIBC)
Aged at least 18 years, gender is not limited;
Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 2;
Histologic confirmation of high-riskpapillary-only non-muscle invasive bladder cancer (high-grade Ta and/or any T1, no carcinoma in situ);
No previous BCG therapy;
Previous histopathological diagnosis was muscle-invasive, locally advanced or metastatic urothelial carcinoma (T2 or T3 or T4 or N+ or M+).
Received surgery such as TURBT or radiotherapy for bladder lesions within 2 weeks before the randomization; Major surgery was performed within 28 days before randomization;
Those who have previously received immunostimulant therapy or immune checkpoint inhibitors;
Those who have previously received intravesical instillation of cytotoxic chemotherapy and have not experienced disease recurrence or progression before enrolment as assessed by investigator;