Sustained-release Formulation of Mitomycin C to the Upper Urinary Tract Using a Thermosensitive Polymer: A Preclinical Study

Objective To evaluate the safety and feasibility of single and serial instillations of MitoGel into the upper urinary tract using a preclinical swine animal model. MitoGel is a novel sustained release formulation of mitomycin C (MMC) based on RTGel, a proprietary thermosensitive hydrogel technology. MitoGel is liquid at cold temperatures and solidifies to gel state at body temperature. It is intended as a treatment for upper tract urothelial carcinoma, given its ability to provide sustained release of MMC in the upper urinary tract. Materials and Methods We utilized 23 pigs in a 3-phase design. All animals underwent bilateral nephrostomy tube placement. During phase 1, 3 animals underwent antegrade RTGel instillation, imaging, and euthanasia within 12 hours. In phase 2, 10 pigs underwent single antegrade instillation, unilateral nephrectomy 3 days following instillation, and contralateral nephrectomy and euthanasia 30 days following instillation. During phase 3, 10 animals underwent 6 instillations over 3 weeks, followed by bilateral nephrectomy and necropsy 30 days postinstillation. MitoGel (2 mg/mL and 4 mg/mL), aqueous MMC (2 mg/mL and 4 mg/mL), and RTGel alone were evaluated. Results MitoGel remained visible within the pelvicalyceal system on fluoroscopic and computed tomography imaging for 4-6 hours. MMC plasma levels were well within acceptable safety thresholds. There was no evidence of urinary obstruction, acute kidney injury, sepsis, or myelosuppression. Histologic changes in the urinary system were mild and transient. Conclusion Antegrade MitoGel delivery to the pelvicalyceal system of Yorkshire swine is feasible and safe. Further evaluation of MitoGel in human clinical trials is warranted.