Abstract 732: Enhanced antitumor efficacy of combination therapy via intravesical perfusion in an orthotopic muscle-invasive bladder cancer model.

Abstract Bladder cancer is a prevalent and aggressive disease with serious health risks if not properly treated. Muscle-invasive orthotopic animal models closely replicate the pathophysiology of human bladder cancer. Orthotopic muscle-invasive bladder cancer model is more technically demanding but essential for translational research. In these models, IVIS-based optical imaging provides a non-invasive and dynamic method to monitor tumor progression in real time. Given the disease’s heterogeneity and resistance to therapy, combination treatments are essential to enhance efficacy by targeting multiple oncogenic pathways. In this study, a muscle-invasive orthotopic bladder cancer model was developed in athymic nude rats by injecting T24-Luc cells directly into the bladder wall. A minor abdominal incision exposed the bladder for catheter placement, which was secured with a purse-string suture and tunnelled to the neck, connected to a harness. After recovery, T24-Luc cells were accurately delivered into the bladder wall without leakage. Tumor progression was monitored twice weekly using IVIS optical imaging. Rats were grouped by total flux intensity, then treated via bladder cannulation with Erdafitinib (5µg/mL), Doxorubicin (400µg/mL), Gemcitabine (90µg/mL) as standalone and combination with Erlotinib, delivered through continuous perfusion over a 7-day period. Total flux (photons/second), changes in body weight, clinicals signs, mortality were monitored twice weekly up to 2 weeks. At end of the study, bladder was excised for assessment of treatment efficacy through multiple parameters, including ex-vivo bioluminescence imaging, bladder weight measurement, photographed, and histopathological and IHC analysis. In the current orthotopic muscle-invasive bladder cancer (MIBC) model, treatment with standalone Erdafitinib, Doxorubicin, or Gemcitabine led to moderate tumor regression. Whereas combination of Doxorubicin and Gemcitabine with Erdafitinib demonstrated the highest anti-tumor efficacy, as evidenced by marked reductions in bioluminescence signal intensity, bladder weight. Histopathological analysis revealed no signs of tumor formation or invasion into deeper bladder layers, and the combination therapy significantly prolonged survival compared to individual treatments. Overall, the findings from this study indicate that combination therapy integrating conventional chemotherapeutic agents with targeted FGFR inhibitors significantly enhances anti-tumor efficacy than monotherapies. Continuous intravesical perfusion via bladder cannulation enables localized drug delivery, effectively minimizing systemic toxicity while maximizing tumor exposure and therapeutic impact Citation Format: Balaji Ramachandran, Satheeshkumar Rajendiran, Girish Joshi, Krishnappa Haladasappa. Enhanced antitumor efficacy of combination therapy via intravesical perfusion in an orthotopic muscle-invasive bladder cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 732.