A Phase 1 Dose-escalation Study of UGN-301 in Patients With Recurrent Non-muscle Invasive Bladder Cancer (NMIBC)

Inclusion Criteria: 1. Able to give informed consent. 2. Arm A: Have confirmed recurrent NMIBC with HG Ta and/or T1 disease and/or CIS or recurrent IR LG Ta and/or T1 disease. Arm B: Have confirmed recurrent NMIBC with HG Ta and/or T1 disease and/or CIS. Arm C: Have confirmed recurrent NMIBC with HG Ta and/or T1 disease and/or CIS. 3. Patients with HG Ta and/or T1 disease and/or CIS must meet one of the following criteria: • Have Bacillus Calmette-Guérin (BCG)-unresponsive disease, defined as 1) persistent or recurrent CIS alone or with recurrent Ta/T1 disease within 12 months of completion of adequate BCG therapy, or 2) recurrent HG Ta/T1 disease within 6 months of completion of adequate BCG therapy, or 3) HG T1 disease at the first evaluation following a BCG induction course. Notes: Adequate BCG therapy is defined as at least 5 of 6 doses of an initial induction course plus 1) at least 2 of 3 doses of maintenance therapy or 2) at least 2 of 6 doses of a second induction course. Patients with BCG-unresponsive disease also must be unwilling or unfit to undergo radical cystectomy. * Have otherwise failed adequate BCG therapy (eg, recurrence \> 6 months \[papillary\] or \> 12 months \[CIS\] after last BCG exposure). * Are BCG intolerant, defined as the inability to tolerate at least one full induction course of BCG. * Have HG Ta disease with tumors ≤ 3 cm and failed at least one previous course of therapy (eg, adjuvant intravesical chemotherapy). 4. Have all papillary tumors visible by white light resected, and obvious areas of CIS fulgurated during Screening or within 6 weeks before Screening. Note: Blue light cystoscopy is not permitted. 5. Eastern Cooperative Oncology Group (ECOG) status ≤ 2. 6. Absence of concomitant upper tract urothelial carcinoma (UTUC) or urothelial carcinoma (UC) within the prostatic urethra. Freedom from upper tract disease (if clinically indicated) as indicated by no evidence of upper tract tumor by either intravenous pyelogram, retrograde pyelogram, computerized tomography (CT) urogram with or without contrast, or magnetic resonance imaging (MRI) urogram with or without contrast performed within 6 months of enrollment. 7. Patients with prostate cancer on active surveillance at very low, low, or intermediate risk for progression, defined as Gleason Grade Group 1 or 2, Gleason score ≤ 7, with prostate-specific antigen \< 20 ng/dL, and cT1-cT2b (NCCN, 2023) are permitted to be in the study at the discretion of the investigator (see exclusion criterion 8). 8. Female patients of childbearing potential must use maximally effective birth control during the period of therapy, must be willing to use contraception for 1 month following the last administration of study drug and must have a negative urine or serum pregnancy test upon entry into this study. Otherwise, female patients must be postmenopausal (no menstrual period for a minimum of 12 months) or surgically sterile. "Maximally effective birth control" means that the patient, if sexually active, should be using a combination of 2 methods of birth control that are approved and recognized to be effective by health authorities. 9. Male patients must be surgically sterile or willing to use 2 highly effective forms of birth control upon enrollment, during the course of the study, and for 1 month following the last study drug instillation. 10. Has adequate organ and bone marrow function within 14 days of treatment initiation as determined by routine laboratory tests outlined below: * Leukocytes ≥ 3,000/μL; * Absolute neutrophil count (ANC) ≥ 1,500/μL; * Platelets ≥ 100,000/μL; * Hemoglobin ≥ 9.0 g/dL; * Total bilirubin ≤ 1.5 × upper limit of normal (ULN); * Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ≤ 2.5 × ULN; * Alkaline phosphatase (ALP) ≤ 2.5 × ULN; * Estimated creatinine clearance ≥ 30 mL/min calculated using the Cockcroft-Gault equation. 11. Has a life expectancy \> 12 months. Exclusion Criteria: 1. Current or previous evidence of muscle invasive, locally advanced nonresectable, or metastatic urothelial carcinoma (ie, T2, T3, T4 and/or stage IV). 2. Current systemic therapy for bladder cancer. 3. Prior therapy with an anti-cytotoxic T lymphocyte antigen 4 (CTLA-4), anti-programmed cell death 1 (PD-1), anti-PD-ligand 1 (L1) agent, or with an agent directed to another co-inhibitory T-cell receptor. 4. Active infection requiring systemic therapy including urinary tract infection (once satisfactorily treated, patients can enter the study). 5. Active systemic autoimmune disease that required systemic treatment in the past 2 years. Short courses of steroids (≤ 14 days) for medical reasons without anticancer intent (eg, atopic dermatitis, psoriasis, infection, allergic reaction) are permitted if the last dose was ≥ 4 weeks before the first dose of study treatment. 6. Women who are pregnant or nursing. 7. Any medical psychological, familial, sociological, or geographical condition that, in the opinion of the Investigator, would preclude participation in the study. 8. History of malignancy of other organ system within the past 5 years, except previously treated UTUC, basal cell carcinoma or squamous cell carcinoma of the skin, and/or prostate cancer under active surveillance (see inclusion criterion 8). 9. Patients who cannot tolerate intravesical dosing or intravesical surgical manipulation. 10. Intravesical therapy within 4 weeks before starting study treatment. 11. Has participated in a study of an investigational agent and received study therapy or received investigational device within 4 weeks before the first dose of study treatment. 12. Has received an immune modulator therapy within 5 half-lives of starting study treatment. 13. Has received a vaccine within 2 weeks before starting study treatment. 14. Has a known allergy or hypersensitivity to any of the study drugs or any of the study drug excipients.