Due to projected low enrollment, it has decided not to move forward with the study.

This trial is designed to evaluate the efficacy and safety of UGN-101 administered to the upper urinary tract (UUT) in patients who were treated in Trial TC-UT-03, found to be a complete response (CR) at the Primary Disease Evaluation (PDE) 1 Visit and are subsequently found to have a documented recurrence of low grade (LG) upper tract urothelial carcinoma (UTUC) at follow up (FU).

This is an open-label, single-arm, Phase 3b multicenter extension trial, designed to evaluate the efficacy and safety of UGN-101 administered to the UUT in patients who were treated in Trial TC-UT-03, found to be a CR at the PDE 1 Visit, and are subsequently found to have a documented recurrence of LG UTUC at FU.

Upon signing of informed consent, the patients will undergo their routine ureteroscopy to assess durability. A biopsy will be performed at Visit 0, if appropriate, to confirm evidence of tumor. If a high grade (HG) UTUC is confirmed by biopsy and/or cytology, the patient will be excluded from the retreatment trial. Eligible patients with confirmed LG non-invasive UTUC will be treated with 3 to 6 once-weekly instillations of UGN-101 in a retrograde fashion, per investigator's discretion.

Five weeks (± 1 week) following the last Investigational product (IP) treatment, the patient will be assessed for efficacy and safety at the PDE 2 Visit. At this visit, the patient will undergo ureteroscopy and any remaining lesions will be biopsied, and UUT urine wash will be collected for cytology.

Patients demonstrating CR at the PDE 2 Visit will undergo FU visits at 3, 6, 9, and 12 months (± 2 weeks) following the PDE 2 Visit.

The trial will be approximately 15 months, per patient: a 3- to 6-week treatment period, followed by 4 to 6 weeks post-treatment leading up to the PDE 2 Visit, and a 12-month FU post PDE 2 Visit. This trial will follow the Steering Committee, and a Data Monitoring Committee (DMC) has been assigned as established for the primary trial TC-UT-03.

Main Inclusion Criteria:

1. Patients with recurrent LG UTUC who were found to be CR at the PDE 1 Visit (in Trial TC-UT-03).
2. Biopsy taken from 1 or more tumors located in the UUT shows LG urothelial carcinoma (up to 2 months before Visit 0). If there are tumors in both the kidney and the ureter, at least 1 biopsy should be taken from each location.
3. Urine wash cytology sampled from the UUT documenting the absence of HG urothelial cancer.
4. Patients must have adequate organ and bone marrow function as determined by routine laboratory tests.
5. Patient has no active urinary tract infection (UTI) as confirmed by urine culture or urinalysis

Main Exclusion Criteria:

1. Patient intends to be treated with systemic chemotherapy during the duration of the trial.
2. Patient with urinary obstruction.
3. Inability to deliver the IP to the UUT.
4. Patient has any other medical or mental condition(s) that make(s) their participation in the trial unadvisable in the opinion of the treating investigator.
5. Patient has a contraindication to mitomycin treatment, or known sensitivity to mitomycin.