Researchers are looking for new ways to treat high-risk non-muscle invasive bladder cancer (HR NMIBC). NMIBC is cancer in the tissue that lines the inside of the bladder and has not spread to the bladder muscle or outside of the bladder. In standard treatment for HR NMIBC, doctors first remove the tumor with a procedure called transurethral resection of the bladder tumor (TURBT). Researchers want to learn if using MK-3120, the study medicine, can treat HR NMIBC after TURBT. The goal of this study is to learn about the safety of MK-3120 and if people tolerate it.