Dual-antigen Doggybone ^TM DNA vaccine induces potent anti-tumor immunity against immunosuppressive oral cancer

Abstract Anti-PD1 blockade benefits only a subset of patients with head and neck squamous cell carcinoma (HNSCC), highlighting the need for approaches that overcome tumor immune resistance. Here, using the doggybone DNA (dbDNA TM ) platform, we developed CaVac OPT, an optimized dual-antigen DNA vaccine targeting MAGED4B and FJX1, which are overexpressed in most HPV-negative HNSCC and multiple solid tumors. In the MOC-2 oral cancer model, CaVac OPT significantly reduced tumor growth and when combined with anti-PD1 therapy, further delayed progression and improved survival. Immune profiling showed increased infiltration of CD4 + and CD8 + T cells, expansion of stem-like Tcf1 + populations, without increase in regulatory T cells, a reduced M2/M1 macrophage ratio and activation of interferon gamma associated pathways with suppression of tumor-promoting signals. These findings demonstrate that CaVac OPT reprograms the tumor microenvironment, converting cold HNSCC into T cell-inflamed responsive tumors. CaVac OPT represents a promising strategy for achieving durable control of aggressive, immunotherapy-resistant head and neck cancer.