This study is testing a new treatment called cretostimogene grenadenorepvec for a type of bladder cancer called Intermediate Risk Non-Muscle Invasive Bladder Cancer (IR-NMIBC) after a surgery called Transurethral Resection of Bladder Tumor (TURBT). IR-NMIBC is bladder cancer that hasn't spread into the muscle layer. In this study, participants will either receive the new treatment after surgery or just be observed. The study checks if adding the treatment helps prevent the cancer from coming back. The treatment involves an initial course and then maintenance doses if the cancer doesn’t return, up to 13 months. Participants will have their bladder checked every 3 months for 2 years, then every 6 months for another year. If cancer returns, the participants can switch to the treatment group. To join, participants must have certain types of bladder cancer and have had all visible cancer removed with surgery.

• The study lasts up to 3 years with frequent check-ups.
• Participants may receive initial and maintenance treatment if no recurrence.
• Possible switch to treatment group if cancer returns.