Safety and Efficacy of BCG Combined With Tislelizumab for BCG-untreated Patients With High-risk Non-muscle Invasive Bladder Cancer

Inclusion Criteria:

* ≥ 18 and ≤75 years old on day of signing informed consent
* Signing informed consent
* Patients with histologically confirmed high-risk NMIBC after TURBT (Patients with mixed histology, predominantly transitional cells, could be enrolled.) High grade pathology (any of the following conditions)

  * CIS
  * T1
  * \>3cm
  * Multifocal
* Patients must be willing to provide a blood sample and a TURBT specimen must be taken at baseline.
* For patients with T1 or suspected incomplete tumor resection after first TURBT, incomplete initial resection or no muscle in original specimen, they should undergo TURBT again within 2-6 weeks.
* No distant metastasis confirmed by CT or MRI in the chest, abdomen, or pelvic cavity within 42 days before treatment.
* ECOG performance status of ≤2
* Life expectancy ≥12 weeks
* Well-controlled blood pressure and within 7 days before treatment \<160/95mmHg
* Normal organ function within 7 days before treatment

  * HB≥90 g/L
  * ANC≥1.5×109 /L
  * PLT≥100×109 /L
  * T-BIL≤1.5×ULN
  * ALT, AST≤2.5×ULN
  * eGFR≥ 20ml/min
  * INR, APTT≤1.5× ULN.

Exclusion Criteria:

* Received prior therapies targeting PD-1 or PD-L1.
* Received prior intravesical therapy of BCG.
* Receive any approved anticancer therapy, including systemic and intravesical chemotherapy within 21 days before enrollment.
* Receive any other trial drug or participate in another therapeutic clinical study within 28 days before enrollment.
* History of severe hypersensitivity reactions to other monoclonal antibodies.
* History of other malignancy.
* Active tuberculosis.
* Severe infections occur within 4 weeks prior to enrollment, including but not limited to infectious complications leading to hospitalization, bacteremia, or severe pneumonia.
* A known history of HIV infection.
* Untreated chronic hepatitis B patients or hepatitis B virus carriers whose HBV DNA≥500 IU/mL
* Patients with active hepatitis C
* Participants with active autoimmune diseases or history of autoimmune diseases that may relapse
* Clinically significant cardiovascular disease, including heart disease (NYHA ≥Ⅲ), myocardial infarction, unstable arrhythmia or unstable angina within 3 months before enrollment.
* A known history of LVEF\<40%
* Prior allogeneic stem cell transplantation or organ transplantation
* History of interstitial lung disease, noninfectious pneumonitis, or uncontrolled diseases.
* Underlying diseases that the investigator believes are not conducive to study treatment or difficult to explain by drug toxicity or adverse events.
* Receive hormone therapy or other immunosuppressive therapy within 14 days before enrollment.