Transdermal bicarbonate buffer therapy increases intratumoral pH and elicits antitumor responses in bladder cancer.

INTRODUCTION: Tumor acidosis is a hallmark of cancer that leads to abrogation of T cell function and cancer progression. Oral sodium bicarbonate therapy for alkalization of the extracellular tumor pH has shown moderate positive effects in tumor models. However, its applicability in the clinic is very limited due to the unreasonably high dosage required and gastrointestinal disturbances that arise. In this study, we assessed the functional effects of acidity on T cells. METHODS: We show that acidity alters T cell proliferation, migration and effector functions as well as transcriptional programming using in vitro culture techniques and RNA sequencing. We then tested the potency of a proprietary transdermal formulation, DYV800, containing sodium bicarbonate to increase the extracellular tumor pH (pHe) and augment anti-tumor immune responses in a murine model of bladder cancer. The tumor pH was assessed using Chemical Exchange Saturation Transfer Magnetic Resonance Imaging (CEST-MRI) and antitumor immune responses via flow cytometry. RESULTS: We found that transdermal DYV800 significantly reduced tumor burden and improved antigen-specific CD8(+) T cell responses. Chemical Exchange Saturation Transfer Magnetic Resonance Imaging (CEST-MRI) of treated tumors showed an increase in intra-tumoral pH of bladder tumors, and this therapy also alkalizes the urine. DISCUSSION/CONCLUSION: The transdermal delivery of DYV800 led to durable anti-tumor immune responses and is more clinically applicable to combat acidity in bladder cancer than oral bicarbonate. Targeting acidosis in the bladder tumor microenvironment has the potential to enhance T cell responses and improve anti-tumor immunity.