Abstract 6366: Novel imidazolium compounds as intravesical therapeutic agents for non-muscle invasive bladder cancer
Authors: Satyal Uttam , Srivastava Abhishek , Weader David J. , Stromyer Michael L. , Southerland Marie R. , Youngs Wiley J. , Abbosh Philip H. 
Published: September 2020

Introduction: Intravesical therapy has critical role in the treatment of high-risk non-muscle invasive bladder cancer. Due to ongoing shortage of BCG and lack of effective alternatives, there is an urgent need for novel intravesical chemotherapeutic agents. In this study, we investigated novel imidazolium compounds on bladder cancer cell lines to characterize activity and mechanism of action and in a mouse model to assess their efficacy and toxicity as intravesical agents.

Methods: Three different imidazolium compounds (IS23, TPP1 and TCK1) were screened for their activity against six bladder cancer cell lines at various concentrations and different exposure time. The GI50s for each compound were then used to assess induction of apoptosis in vitro and to study mechanism of action. In vivo efficacy and toxicity of these compounds was studied in normal mice. The BBN mouse model was used to assess in vivo efficacy of these compounds, as it recapitulates the histological and genetic characteristics of human bladder tumors. The drinking water of 6 to 8 weeks old mice was supplemented with 0.05% BBN for 12 weeks, then switched to regular drinking water. Mice were randomly assigned into 5 intravesical treatment groups with 50:50 male:female make up in each group: 1) IS23; 2) TPP1; 3) TCK1; 4) Gemcitabine; 5) vehicle. Drugs and vehicle were instilled for four weeks. Each mouse was subjected to excretory computed tomography urogram to assess the filling defects in the bladder before treatment and every two weeks following the treatment. Mice were euthanized if size of filling defect in urograms exceeded 1/3 of the bladder, developed hydronephrosis, or 4 weeks after completion of intravesical treatment, whichever came first.

Results: All imidazolium compounds showed toxicity to bladder cancer cells, TCK1 and TPP1 being the most and least potent respectively. They were also highly effective in killing bladder cancer cells with a 15-min GI90-dose. They briskly induced apoptosis by directly causing Cytochrome C expulsion from isolated mitochondria. Intravesical imidazolium compounds did not cause significant histopathological changes in normal bladder compared to vehicle group, but TPP1 was found to be tumor specific in vivo. TPP1 induced apoptosis in tumor without affecting normal bladder urothelium. In BBN-induced mice, 4/4 IS23-treated mice had filling defects while 8/15, 5/6, 10/11, and 7/8 TPP1-, TCK1-, vehicle-, and gemcitabine-treated mice had filling defects on urograms consistent with tumor. TPP1- and TCK1-treated mice had smaller filling defects compared to vehicle group mice, which was also confirmed histopathologically.

Conclusions: TPP1 has a novel and potent mechanism and is worthy of further study as an intravesical agent for the treatment of high-grade superficial bladder cancer. It appears to work through a mitochondrial-centric mechanism and have cancer-specificity.

Citation Format: Uttam Satyal, Abhishek Srivastava, David J. Weader, Michael L. Stromyer, Marie R. Southerland, Wiley J. Youngs, Philip H. Abbosh. Novel imidazolium compounds as intravesical therapeutic agents for non-muscle invasive bladder cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6366.