(M0930-07-40) Light Activatable Prodrug Strategy to Treat Non-muscle Invasive Bladder Cancer

Purpose: Bladder cancer (BC) is the 4^th most common cancer in men in the United States and more than 70% of the patients are initially diagnosed with non-muscle invasive bladder cancer (NMIBC). Following surgery, patients can receive either Bacillus Calmette–Guérin (BCG) vaccine, chemotherapy, or PD-1 checkpoint inhibitors. Each of them has mild to severe side effects and cannot completely prevent recurrences which makes BC the costliest cancer to manage. Hexaminolevulinate (HAL) induces cancer cells to produce 9-16 times more protoporphyrin IX (PpIX, a powerful photosensitizer) than normal cells, the basis for the FDA-approved diagnosis of BC. We utilized photodynamic therapy (PDT) to selectively activate prodrugs in the tumor. Since PpIX can also be used to treat NMIBC but lacks efficacy, we used a light-activatable linker system to develop prodrugs to combine with PpIX-PDT.

Methods: To overcome the diffusion limitations in the bladder and to improve drug pharmacokinetics and efficacy, a wide range of prodrugs such as mitochondria-targeted (linked with rhodamine, a mitochondria targeting probe) and non-mitochondria-targeted (linked with methyl, morpholine, or piperidine) have been synthesized. In-vitro evaluations were conducted using AY-27 cell monolayers and 3D spheroids, where HAL-prodrug combination efficacy was compared to HAL-only efficacy with a 531nm green laser. Ex-vivo diffusion studies were conducted using porcine bladders. An orthotopic rat model of NMIBC has been developed to evaluate the prodrugs' in-vivo efficacy.

Results: Prodrugs were successfully synthesized with a high yield and more than 90% purity. All the prodrugs could generate more than 90% cell killing in-vitro. Studies with monolayers and 3D spheroids have shown that mitochondrial targeting could improve intracellular uptake and retention of prodrugs ( >80%) during the illumination (≤30 minutes) and thus enhance delivery efficiency. Formulation development further helped to overcome the diffusion limitation and helped to achieve drug penetration deep inside the bladder wall to cover the depth of NMIBC. A photodynamic diagnosis (PDD) procedure was developed using intravesical administration of HAL to detect tumors using PpIX-PDD. The primary in-vivo evaluation proved the initial hypothesis of achieving significantly greater efficacy from the HAL-prodrugs combination compared to the HAL-only group. Based on the histology study there was no significant toxicity to the normal bladder associated with the treatment. In-vivo antitumor efficacy study of selected prodrugs in an orthotopic rat model of bladder cancer is currently underway.

Conclusion: The combination of prodrugs with PpIX-PDT can be more effective than PpIX-PDT alone in treating NMIBC, without causing serious side effects in the normal bladder.

Acknowledgements: The authors thank Dr. Steven H. Selman at the University of Toledo for sharing AY-27 cells and Dr. Sanjay G. Patel for consultation for clinical translational potential of our approach. This project was supported by the DoD (Peer Reviewed Cancer Research Program, W81XWH-17-1-0226). Views and opinions of and endorsements by the author(s) do not reflect those of the US Army or the DoD.


Tumor volume was significantly reduced with combination therapy (PpIX-PDT + Prodrug) compared to the PpIX-PDT only.


The PDT treated normal region is similar to the normal epithelium of the untreated Bladder, hence very low toxicity was assumed.