The aim of this study is to evaluate the feasibility, safety, and efficacy of MitoGel in the treatment of UTUC in a human subject with low-grade UTUC which is endoscopically unresectable or rapidly recurring, and in whom nephrectomy would likely result in the need for permanent hemodialysis. The study drug would be obtained under the single patient access program approved by the FDA. The patient would then undergo instillation of MitoGel into the affected kidney. The catheter would be left indwelling in the ureter and would be externalized through a urethral catheter. The ureteral and urethral catheters would remain indwelling for the duration of the 6 treatments, which would occur twice weekly for 3 weeks. Following the final instillation, the catheters would be removed. The patient would then undergo ureteroscopic evaluation at 3 months following the final instillation of MitoGel. The total duration of study would be 3 months. The total number of study patients is 1.