Abstract 4099: AMP-peptide vaccination against multiple p53 mutant epitopes promotes lymph node delivery to generate potent, functional T cell immunity

Abstract Background p53 is the most commonly mutated gene in human cancer, prevalent in nearly all tumor types. Despite its significant medical relevance and the knowledge that human T cells recognize these mutations1, 2, immunotherapies designed to promote responses against mutated p53 (mp53) have not had the hoped-for clinical impact3. The Amphiphile (AMP) platform improves the potency of vaccine immunotherapy by programming the delivery of vaccine components to the lymph nodes where efficient uptake by immune cells initiates tumor-targeted immune responses. AMP-modification of vaccine components (peptide antigens, molecular adjuvants) results in covalent conjugation to albumin-binding lipids. Upon injection, AMP-vaccines associate with tissue-resident albumin which efficiently distributes to draining lymph nodes. This approach was shown to promote activation of polyfunctional, cytotoxic T cells with promising safety and improved clinical outcomes in a Phase 1 trial of ELI-002, an mKRAS AMP therapeutic vaccine (AMPLIFY-201 NCT05726864). Application of this strategy to p53 mutations with ELI-008 offers the potential for improved immunotherapeutic activity in a setting of significant unmet need. Methods Following immunization of C57BL/6J mice with AMP-modified or soluble comparator vaccines consisting of mp53 peptides and CpG adjuvant, analyses were performed 7 days after the third bi-weekly dose. To assess antigen-specific T cell responses, ELISpot (IFNγ, GzmB), multiplexed proteomic, and flowcytometric analysis of effector cytokines (IFNγ, TNFα, IL-2) were performed following antigenic stimulation. Responses were determined in secondary lymphoid tissues and lung. Cytolytic capabilities of antigen-specific T cells were evaluated by monitoring specific killing of IV-transferred antigen-pulsed target cells. Results AMP-immunization generated robust immune responses yielding strong T cell activation against common p53 hot spot mutations (R248W, R248Q, R175H, G245S, R273H, Y220C, C135Y, R158H, H214R). Responses to AMP-vaccination were characterized by the generation of increased frequency of polyfunctional T cells (IFNγ, TNFα, IL2) specific to mp53 epitopes. Induced T cells demonstrated significant levels of cytolytic activity including GzmB production and elimination of target cells in vivo. Non-lymph targeted vaccines using soluble comparators were inactive. Conclusions AMP-conjugation permits efficient delivery directly to the lymph nodes and thus improves the immunogenicity of peptide vaccination. These substantially improved immune responses induced by ELI-008 represent a promising therapeutic opportunity for targeting cancer in a large fraction of human tumors. The AMP-platform technology is simple, rapid and scalable, promising broad clinical, off-the-shelf application for treating p53 mutated tumors. Citation Format: Martin P. Steinbuck, Xavier Cabana-Puig, Erica Palmer, Mimi M. Jung, Thomas Williams, Kristen Osaer, Jeff Zhang, Christopher M. Haqq, Peter C. DeMuth. AMP-peptide vaccination against multiple p53 mutant epitopes promotes lymph node delivery to generate potent, functional T cell immunity 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 (6Suppl): Abstract nr 4099.