The primary efficacy endpoint was the number of patients attaining complete response (CR) at the end of the treatment period (Primary Disease Evaluation (PDE) visit). The CR was defined dichotomously as "Success" if CR was confirmed at PDE visit (or relevant follow-up), and "Failure" otherwise.

Continuously: Duration of CR or time-to-recurrence since the Primary Disease Evaluation (PDE) Visit (i.e., time in days from the visit at which CR was determined until recurrence or censoring). This endpoint served as the main long-term durability endpoint. Dichotomously: "Success" if CR was still present at the 12 month post-PDE Visit (at Follow-Up Visit 4), and "Failure" otherwise. This endpoint served as a supportive long-term durability endpoint.

Durability of CR defined dichotomously as "Success" if CR was achieved at Primary Disease Evaluation (PDE) visit and remained at follow-up Visit 1, Visit 2 and Visit 3 (3, 6, 9 and 12 months post PDE visit), and "Failure" otherwise.

Clinical benefit for patients with partial response (PR) at the PDE visit. Clinical benefit endpoint was analyzed using the Intent-to-Treat (ITT) Analysis Set, including patients who achieved partial response at PDE Visit.Partial response at PDE visit will be defined dichotomously, similarly to the primary efficacy endpoint. For subjects with partial response at PDE visit, originally planned and actual treatments will be compared.

Cmax: maximum plasma concentration

Analysis of individual plasma concentration versus time profiles showed that at 6 hours post instillation, the plasma concentrations of all 6 patients were below 2 ng/mL, with the plasma concentration of one patient dropping below the LOQ (i.e., < 0.100 ng/mL). The mean Cmax was 6.24 ng/mL (range: 2.43 to 12.80 ng/mL). The highest individual observed Cmax value of 12.80 ng/mL was 187-fold and 40 fold lower than the observed Cmax level following an intravenous bolus dose of 30 mg or 10 mg mitomycin (2.4 μg/mL and 0.52 μg/mL, respectively) and is 31 fold lower than the threshold value of 400 ng/mL for myelosuppression observed with mitomycin.

PK Analysis Set: Consisted of patients who signed consent for PK and had sufficient PK data for the determination of PK parameters.

Treatment-emergent AEs were most frequently reported from the Renal and urinary disorders system organ class (SOC), 59 (83.1%) patients, as expected, given the underlying indication of low grade (LG) Upper tract urothelial carcinoma (UTUC) in the study population, chemotherapeutic drug in a gel matrix instilled in the upper urinary tract (UUT), and the study procedure of treatment instillation via a ureteral catheter. The toxicity within the upper urinary tract was considered consistent with the disease under study and the mode of administration of UGN-101. Most events in the Renal and urinary disorders SOC were mild to moderate in severity and resolved. No new risks were identified and the overall safety profile was consistent with the known safety profile of endoscopic administration of intravesical mitomycin and of mitomycin. Overall, based on the safety and efficacy results to date, the benefit-risk profile of UGN-101 is favorable for the treatment of LG-UTUC.

Safety: Consisted of all patients who enrolled in the study and received at least 1 instillation of UGN-101.

Tmax: time to maximum plasma concentration

Analysis of individual plasma concentration versus time profiles showed that at 6 hours post instillation, the plasma concentrations of all 6 patients were below 2 ng/mL, with the plasma concentration of one patient dropping below the LOQ (i.e., < 0.100 ng/mL).

The mean Cmax was 6.24 ng/mL (range: 2.43 to 12.80 ng/mL), and the Tmax was 1.79 hours (range: 0.50 to 5.17 hours) after instillation. The highest individual observed Cmax value of 12.80 ng/mL was 187-fold and 40 fold lower than the observed Cmax level following an intravenous bolus dose of 30 mg or 10 mg mitomycin (2.4 μg/mL and 0.52 μg/mL, respectively) and is 31 fold lower than the threshold value of 400 ng/mL for myelosuppression observed with mitomycin.

PK Analysis Set: Consisted of patients who signed consent for PK and had sufficient PK data for the determination of PK parameters.

Half-life (t½): terminal half-life

The mean apparent t½ following instillation of mitomycin into the upper urinary tract (UUT) was 1.27 hours (76 minutes), which was longer than the true t½ of mitomycin following a 30 mg bolus injection (mean t½ value of approximately 17 minutes). The apparent t½ demonstrates that UGN-101 dissolved gradually, resulting in prolonged exposure of mitomycin following local instillation into the UUT.

PK Analysis Set: Consisted of patients who signed consent for PK and had sufficient PK data for the determination of PK parameters.