Intismeran and BCG for High-Risk Bladder Cancer

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: \- Is an individual whose most recent TURBT was performed within 12 weeks before randomization/allocation and showed BICR-confirmed high-risk NMIBC histology Cohort A: * Has high-risk non-muscle invasive (HG Ta, T1, and/or CIS) UC of the bladder * Is BCG-naïve defined as either having never received BCG or having received BCG more than 2 years before high-risk NMIBC recurrence. Recurrence must be at least 24 months from the last exposure to BCG with evidence of complete response during the 2-year period post BCG Cohort B: * Has CIS +/-papillary non-muscle invasive UC of the bladder * Is ineligible for, or refusing, any IVESIC therapy * Is either BCG-naïve (as defined above) or BCG-exposed but did not receive protocol-specified minimum dosing of BCG and experienced recurrence of high-risk NMIBC within 2 years of the last dose of BCG * Human immunodeficiency virus (HIV)-infected individuals must have well controlled HIV on antiretroviral therapy (ART) Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * Has a history of or concurrent locally-advanced (ie, T2, T3, T4) or metastatic UC * Has concurrent extravesical (ie, urethra, ureter, renal pelvis) non-muscle invasive UC or a history of extravesical non-muscle invasive UC that recurred within the last 2 years, with certain exceptions * Has a known additional malignancy that is progressing or has required active treatment within the last 3 years * Has had a myocardial infarction within 6 months of randomization/allocation * Has received any systemic anticancer therapy including investigational agents within 4 weeks before randomization/allocation * Has received prior treatment with a cancer vaccine * Has immunodeficiency or is receiving chronic systemic steroid therapy * Has active autoimmune disease that has required systemic treatment in the last 2 years * Has any contraindication to IV contrast and gadolinium or is otherwise unable to have imaging with either computerized tomography urogram (CTU) or Magnetic resonance urography (MRU) Cohort A: * Has current active tuberculosis * Has a known history of HIV infection Cohort B: \- HIV-infected individuals with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease