Abstract 2462: Live attenuated Salmonella ZH9 as novel microbial immunotherapy for the treatment of bladder cancer

Abstract

Abstract Microbial immunotherapy with Bacillus Calmette-Guérin (BCG) has been the standard-of-care for non-muscle invasive bladder cancer (NMIBC) for over 30 years. Today, global demand for BCG exceeds supply, leaving many patients untreated. BCG is associated with high disease recurrence and presents high treatment burden for patients. There remains therefore significant unmet need for novel therapeutic approaches for NMIBC and we sought to establish the utility of the live-attenuated Salmonella enterica Typhi ZH9 as a more effective microbial immunotherapy. Efficacy of ZH9 was established in orthotopic, syngeneic, mouse MB49 tumor models in which animals were treated in the bladder via catheterization, with or without prior subcutaneous immune priming. Immune responses were measured by flow cytometry and Nanostring transcriptomic analyses of bladder tissues. An intravesical dose of ZH9 after orthotopic MB49 tumour inoculation demonstrated significant survival benefit compared to both vehicle control and equivalent colony forming unit (CFU) BCG treatments. Repeat, weekly dosing studies showed a single administration of ZH9 was sufficient for maximum efficacy. To explore the durability of protection, surviving intravesical ZH9 treated animals were rechallenged, demonstrating protection from both bladder and subcutaneous MB49 tumors suggestive of lasting local and systemic anti-tumor immunity. Flow cytometry analysis of bladders showed that intravesical ZH9 treatment resulted in cellular immune response characterised by recruitment of NK cells, CD4+ and CD8+ T cells, and dendritic cells with an activated, cross-presenting phenotype, in all cases of greater magnitude than after treatment with an equivalent dose of BCG. Based on observations that pre-existing immunity to BCG has been associated with improved outcomes to intravesical BCG therapy in NMIBC, we explored whether systemic priming with ZH9 benefits local bladder therapy. Systemic prime with ZH9 followed by a single intravesical dose of ZH9 showed a trend for improved survival and will be explored in the clinical setting. This systemic immune priming effect was associated with enhanced local bladder immune cell infiltrates and the upregulation of more than 150 immune response genes in the bladder compared to intravesical therapy alone. These data form the basis of preclinical package accepted by the FDA for a Phase 1/1b study evaluating the safety, pharmacology, and clinical effect of ZH9 treatment in patients with NMIBC, currently recruiting patients. The investigation includes thorough translational and biomarker studies to delve into the mechanism of action of ZH9 and explore patient stratification approaches. By easing the treatment burden on patients, lowering healthcare costs, and featuring a scalable manufacturing process, ZH9 has the potential to revolutionize the treatment paradigm in NMIBC and reshape the patient journey. Citation Format: Nicholas Glanville, Oluwatobiloba Oke, Claudia Prevosto, Alexandra Sevko, Andrew Scott, Sonia Domingos-Pereira, Lenka Polak, Denise Nardelli-Haefliger, Livija Deban. Live attenuated Salmonella ZH9 as novel microbial immunotherapy for the treatment of bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2462.