A Study to Evaluate Eciskafusp Alfa in Combination With Bacillus Calmette-guerin (BCG) in Participants With BCG-unresponsive High-risk Non-muscle Invasive Bladder Cancer (NMIBC)

Inclusion Criteria: * Pathologically confirmed high risk non muscle invasive transitional cell carcinoma classified according to World Health Organization (WHO) grading system * Absence of resectable disease after transurethral resection of bladder tumor (TURBT) procedures * The most recent cystoscopy/TURBT must have been performed within 12 weeks and up to 14 days of the first dose of study treatment * Presence of BCG-unresponsive disease defined as persistent or recurrent carcinoma in situ \[CIS\] (± recurrent Ta/T1 disease) within 12 months of receiving adequate BCG therapy * The participant is considered ineligible for radical cystectomy or has elected not to undergo the procedure. * Negative hepatitis B surface antigen (HBsAg) test at screening * Positive hepatitis B surface antibody (HBsAb) test at screening * Negative hepatitis C virus (HCV) antibody test at screening Exclusion Criteria: * Significant history of or current cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, or neurological disorders * Active infections (both systemic and local urinary) * Congenital or acquired immune deficiencies resulting in immunosuppression * Known human immunodeficiency virus (HIV) infection * History of radiotherapy of the bladder * History of perforation of the bladder * Major surgery or significant traumatic injury within 28 days prior to first administration of study treatment or anticipation of the need for major surgery during treatment * Participants currently receiving investigational or commercial anti-cancer agents or anti-cancer therapies other than BCG, and supportive care therapies for active disease * Any intervening intravesical immunotherapy or chemotherapy from the time of the most recent cytoscopy/TURBT to the start of study treatment * Systemic immune-modulating and systemic immunosuppressive agents/medication * Administration of a live, attenuated vaccine within 28 days prior to first administration of study treatment * Recurrence of BCG unresponsive CIS \> 12 months after last BCG instillation * Concurrent second malignancy