A Study to Evaluate TAR-210 Versus Intravesical Chemotherapy Treatment in Participants With High Risk Non-Muscle-Invasive Bladder Cancer

Inclusion criteria:

• Histologically confirmed diagnosis by local pathology of papillary-only HR-NMIBC (defined as high-grade Ta or any T1, no CIS). Mixed histology tumors are allowed ifurothelial differentiation is predominant. However, neuroendocrine, and small cellvariants will be excluded

• Have a susceptible fibroblast growth factor receptor (FGFR) mutation or fusioneither by urine testing or tumor tissue testing (from TURBT tissue) as determined bycentral or local testing

• All visible tumor completely resected prior to randomization. Urine cytology mustnot be positive or suspicious for high grade UC before randomization. Forparticipants with lamina propria invasion (T1) on the screening biopsy/TURBT,muscularis propria must be present to rule out MIBC

• Participants must have had either: a. Adequate Induction (5 of 6 doses) and either 2of 3 doses of Maintenance or 2 of 6 doses of second Induction of BCG with high-gradeT1 disease at first disease assessment after induction or high-grade Ta/any T1disease within 6 months after last BCG (BCG-unresponsive population); b. hadadequate induction (5 or 6 doses) with or without maintenance BCG with high-gradeTa/any T1 disease within 12 months after last BCG excluding BCG-unresponsive (BCG-experienced population); or c. been unable to complete an induction course ofBCG with at least 5 doses due to grade >= 2 toxicity requiring BCG discontinuation (BCG intolerant population)

• Have an Eastern Cooperative Oncology Group (ECOG) performance status Grade of 0, 1,or 2

• Must be ineligible for or refusing radical cystectomy (RC)

Exclusion criteria:

• Presence of CIS at any point from time of diagnosis of papillary-only HR-NMIBCrecurrence to randomization. Additionally, presence or history of histologicallyconfirmed, muscle-invasive, locally advanced, nonresectable, or metastaticurothelial carcinoma (that is [i.e.], T2, T3, T4, N+, and/or M+)

• Active malignancies (i.e., progressing or requiring treatment change in the last 24months) other than the disease being treated under study. Allowed recent second orprior malignancies: a. Any malignancy that was not progressing nor requiringtreatment change in the last 12 months; b. Malignancies treated within the last 12months and considered at very low risk for recurrence for example (e.g.):non-melanoma skin cancers (treated with curative therapy or localized melanomatreated with curative surgical resection alone), non-invasive cervical cancer,breast cancer (adequately treated lobular CIS or ductal CIS, localized breast cancerand receiving antihormonal agents), localized prostate cancer ([N0, M0] with aGleason score less than or equal to [<=] 7a, treated locally only [radicalprostatectomy/radiation therapy/focal treatment]) and other malignancy that isconsidered at minimal risk of recurrence

• Presence of any bladder or urethral anatomic feature that, in the opinion of theinvestigator, may prevent the safe placement, indwelling use, or removal of TAR 210

• A history of clinically significant polyuria with recorded 24 hour urine volumesgreater than (>) 4,000 milliliters (mL)

• Indwelling catheters are not permitted; however, intermittent catheterization isacceptable