A polymeric paste-drug formulation for local treatment of upper tract urothelial carcinoma

Background: Intravesical instillation of chemo- or immunotherapy is commonly used in bladder Cancer. Upper tract urothelial carcinoma (UTUC) shares similar pathological features, but current formulations are not suitable for direct instillation to the upper urinary tract.

Objective: To evaluate in vivo applicability, characteristics and toxicity of ST-UC, a mucoadhesive polymeric paste formulation of gemcitabine, for upper urinary tract instillation.

Material and methods: Three pigs received 10 ml of ST-UC (100 mg/ml gemcitabine) retrogradely into 1 renal pelvis for pharmacokinetic studies. Four days later, a second injection into the contralateral renal pelvis was followed by serial euthanasia of the pigs and nephroureterectomy after 1, 3, and 6 hours. Adverse effects were monitored. Urine, serum, and tissue gemcitabine concentrations were measured, along with histologic examination of the upper urinary tract.

Results: Retrograde instillation of ST-UC was well tolerated with mild, completely receding hydronephrosis. Urine gemcitabine concentrations were highest in the first 3-hour collection interval. Hundred percent of gemcitabine was recovered in the urine within 24 hours. Serum peak concentrations (c_max) of gemcitabine were low at 5.5 µg/ml compared to the 10 to 30 µg/ml levels observed after a single intravenous dose of 1,000 mg/m² gemcitabine. The formulation was still traceable after one hour and gemcitabine tissue concentrations are supportive of this extended drug exposure. No major histopathological changes were observed. The main limitation of this study is the lack of antitumor activity data.

Conclusion: This preclinical evaluation of ST-UC demonstrated feasible instillation in the renal pelvis, no significant safety concerns, and sustained release of gemcitabine.