RMAD1, a novel cell-penetrating peptide, enhances cancer vaccine efficacy by boosting T cell activation and reducing tumor burden

Effective cancer vaccines face significant hurdles, primarily due to limited antigen delivery to immune cells and suboptimal T cell priming. Current approaches often struggle to elicit robust and durable anti-tumor immunity while maintaining a favorable safety profile. This gap necessitates the development of advanced delivery platforms that can efficiently transport antigens to antigen-presenting cells (APCs) and enhance subsequent T cell activation, particularly through the MHC class I pathway, to overcome tumor immune evasion.

Researchers identified RMAD1, a novel human-derived cell-penetrating peptide (CPP) from the ADARB2 protein, using an intra-dermal delivery technology (IDDT) platform. They evaluated its potential as a vaccine delivery enhancer in murine E.G7-OVA and TC-1 tumor models. RMAD1 conjugated vaccines were compared against conventional CPPs and cisplatin treatment. Key endpoints included intracellular delivery efficiency, preferential uptake by APCs, accumulation in draining lymph nodes, antigen cross-presentation, antigen-specific CD8+ T cell responses in peripheral blood, lymphoid organs, and tumor tissues, IFN-γ and TNF-α production, Foxp3+CD25+ regulatory T cell reduction, epitope spreading, immunological memory, protection against tumor rechallenge, and metastatic burden reduction in a TC-1 lung metastasis model. Safety was also assessed.

RMAD1 demonstrated superior intracellular delivery compared to conventional CPPs and exhibited preferential uptake by antigen-presenting cells (APCs), including dendritic cells and macrophages. RMAD1 conjugated vaccines showed enhanced accumulation in draining lymph nodes and facilitated efficient antigen cross-presentation via the MHC class I pathway. In murine E.G7-OVA and TC-1 tumor models, RMAD1 conjugated vaccines induced robust antigen-specific CD8+ T cell responses across peripheral blood, lymphoid organs, and tumor tissues. Functional analyses revealed increased IFN-γ and TNF-α production by both CD8+ and CD4+ T cells, accompanied by a reduction in Foxp3+CD25+ regulatory T cells. Additionally, RMAD1 conjugation promoted epitope spreading and established durable immunological memory, leading to protection against tumor rechallenge. Therapeutic efficacy was further demonstrated: > RMAD1-based vaccination significantly reduced metastatic burden in a TC-1 lung metastasis model, exhibiting therapeutic efficacy comparable to cisplatin treatment while maintaining a favorable safety profile.