UK Center for Clinical and Translational Science

Parts 1-3: - Muscle-invasive or recurrent, non-muscle-invasive urothelial carcinoma of the bladder - For selected Cohorts: Activating tumor pan-fibroblast growth factor receptor (FGFR) mutation or fusion, as determined by local or central testing, approved by the sponsor prior to the start of study treatment. Local tissue-based results (if already existing) from next-generation sequencing (NGS) or polymerase chain reaction (PCR) tests performed in Clinical Laboratory Improvement Amendments (CLIA) -certified or equivalent laboratories, or results from commercially available PCR or NGS tests - Cohorts 1 and 2: Bacillus Calmette-Guérin (BCG) experienced, or participants with no BCG experience because BCG was not available as a treatment option in the participant's location within the previous 2 years and is currently unavailable. Participants who received an abbreviated course of BCG due to toxicity are still eligible - Cohort 1 only: Refuses or is not eligible for radical cystectomy (RC) - Cohorts 2 and 4: Willing and eligible for RC Part 4: - Have histologically confirmed diagnosis of recurrent Intermediate-risk-non-muscle invasive bladder cancer (IR-NMIBC) Ta LG tumors - Must not have undergone tumor debulking or selective ablation of visible lesions; partial tumor biopsy to confirm diagnosis and provide tissue for biomarker testing is permitted as long as remaining tumor is at least 5 millimeter (mm) in size - Must submit tissue and urine for FGFR testing - Can have a prior or concurrent second malignancy which natural history or treatment is unlikely to interfere with any study endpoints of safety or the efficacy of the study treatment

Parts 1-3: - Concurrent extra-vesical (that is, urethra, ureter, renal pelvis) transitional cell carcinoma of the urothelium - Prior treatment with an pan-fibroblast growth factor receptor (FGFR) inhibitor - Received pelvic radiotherapy <=6 months prior to the planned start of study treatment. If received pelvic radiotherapy greater than (>)6 months prior to the start of study treatment, there must be no cystoscopic evidence of radiation cystitis - Presence of any bladder or urethral anatomic feature that in the opinion of the investigator may prevent the safe use of Erdafitinib intravesical delivery system - Indwelling urinary catheter. Intermittent catheterization is acceptable Part 4: - Histologically confirmed diagnosis of T1 NMIBC, HR NMIBC (HG/G2 or HG/G3 or CIS) or MIBC, locally advanced, non-resectable, or metastatic urothelial carcinoma at any time prior to enrollment - Known allergies, hypersensitivity, or intolerance to any study component or its excipients - Has a current diagnosis of primary IR-NMIBC - Received an investigational treatment for bladder cancer after Transurethral Resection of the Bladder Tumor (TURBT) for the current NMIBC diagnosis or within 4 weeks or the agent/therapy washout period, whichever is longer, before the planned first dose of study treatment, or is currently enrolled in an investigational study - Evidence of current bladder perforation by cystoscopy or imaging