A Study of TAR-200 in Combination With Cetrelimab or TAR-200 Alone Versus Intravesical Bacillus Calmette-Guérin (BCG) in Participants With BCG-naïve High-risk Non-muscle Invasive Bladder Cancer (HR-NMIBC)

Prior treatment

• Must not have had urothelial carcinoma or histological variant at any site outside of the urinary bladder (that is, urethra, ureter, or renal pelvis). Ta/any T1/CIS of the upper urinary tract (including renal pelvis and ureter) is allowable if treated with complete nephroureterectomy more than 24 months prior to randomization

Other illness

• Presence or history of histologically confirmed, muscle invasive, locally advanced, nonresectable, or metastatic urothelial carcinoma (that is, greater than and equal to \[\>=\] T2)
• A history of clinically significant polyuria with recorded 24-hour urine volumes greater than 4000 milliliters (mL)

Other

• Presence of any bladder or urethral anatomic feature (example, urethral stricture) that, in the opinion of the investigator, may prevent the safe insertion, indwelling use, removal of TAR-200 or administration of intravesical BCG. Participants with tumors involving the prostatic urethra in men will be excluded
• Indwelling catheters are not permitted; however, intermittent catheterization is acceptable

• Histologically confirmed initial diagnosis by local pathology (within 90 days of the most recent signed informed consent) of high grade non-muscle invasive bladder cancer (HR-NMIBC) (high-grade Ta, any T1 or carcinoma in-situ \[CIS\]), in participants who are Bacillus Calmette Guérin (BCG)-naïve
• BCG-naïve (participants who have not received prior intravesical BCG or who previously received but stopped BCG more than 3 years before date of randomization are eligible)
• All visible papillary disease must be fully resected (absent) prior to date of randomization and documented at baseline cystoscopy. Local urine cytology at screening must be negative or atypical (for high-grade urothelial carcinoma \[HGUC\]) for patients with papillary only disease (without CIS)
• Eastern Cooperative Oncology Group (ECOG) performance status Grade 0, 1, or 2
• All adverse events associated with any prior surgery and/or intravesical therapy must have resolved to common terminology criteria for adverse events (CTCAE) version 5.0 Grade less than (\<) 2 prior to date of randomization
• Participants must be willing to undergo all study procedures