Abstract 6701: Re-engineering cancer vaccines: Bria-OTS+ integrates innate and adaptive immunity for broad and persistent anti-tumor responses

Abstract Background: Despite major advances in immuno-oncology, achieving durable tumor control remains difficult because of tumor heterogeneity, immune evasion, and limited coordination between innate and adaptive immune responses. Whole-cell cancer vaccines offer broad antigenic coverage but have historically lacked potency and persistence. Bria-OTS+ is a next-generation, genetically engineered whole-cell cancer vaccine platform designed to overcome these limitations by integrating innate and adaptive immunity. Bria-OTS+ is composed of genetically reprogrammed tumor cells that naturally display a broad antigen repertoire, while being engineered to express immune-stimulatory cytokines (GM-CSF, IFN-α, IL-12, IL-7), co-stimulatory molecules (CD80, CD86, CD40, 4-1BBL), and diverse HLA-A and HLA-DR alleles, supporting potent immune activation and broad semi-allogeneic compatibility (99 % population coverage). Methods: Irradiated Bria-OTS+ cells representing breast, prostate, lung, and melanoma lineages were co-cultured with human PBMCs in a four-phase in vitro vaccination assay (priming, resting, boosting, effector) designed to model sequential immune activation, memory formation, and recall response. Immune activation, proliferation, and cytotoxicity were quantified by flow cytometry and ELISA. Mechanistic dissection employed blocking antibodies to CD86, IL-12, NKp46, and HLA-I/II molecules to define signaling dependencies. Results: Bria-OTS+ induced coordinated activation of CD4+/CD8+ T, NK, NKT, dendritic, and B cells, with strong IFN-γ/TNF-α release and up-regulation of CD69/CD25. CD80/CD86 increased on dendritic and B cells, indicating enhanced antigen-presenting potential. NK-cell cytotoxicity dominated early responses and was amplified by IL-12 and CD86 signaling. Upon recall, T and NK cells exhibited amplified cytokine release, proliferation, and tumor-cell killing together with a memory phenotype and controlled checkpoint profile (low PD-1/TIM-3, moderate LAG-3), indicating persistent effector competence without exhaustion. Bria-OTS+ activated PBMCs killed both homologous and heterologous tumor targets, supporting shared antigen recognition and/or NK activity and reduced Immuno-evasion risk. Conclusions: Bria-OTS+ functions as a modular, immune-educating platform that integrates trained innate and adaptive immunity within a scalable, semi-personalized framework. By coupling multi-cytokine signaling and co-stimulation with HLA-guided antigen presentation, Bria-OTS+ achieves persistent immune activation, broad tumor recognition, and is readily manufacturable for off-the-shelf clinical deployment. Citation Format: Miguel A. Lopez-Lago, Pravin Kesarwani, Vikas Bhardwaj, Xiaoyi Zheng, Ying Liu, Sagarika Pachhal, Patience cournoo, Renee Cortez, George Woodfield, Charles Wiseman, William V. Williams. Re-engineering cancer vaccines: Bria-OTS+ integrates innate and adaptive immunity for broad and persistent anti-tumor responses 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 6701.