CD40 agonistic-monovalent streptavidin fusion antibody for targeted neoantigen peptide delivery and potent cancer vaccination.

Cancer vaccines targeting patient-derived neoantigens offer great promise for personalized cancer therapy but face challenges in achieving targeted delivery to antigen-presenting cells (APCs) to elicit robust and durable cancer-specific immune responses. To address this, we developed an anti-mouse CD40 agonistic-monovalent streptavidin fusion antibody (αCD40-mSAs) that targets CD40, a key stimulatory receptor on APCs, to deliver biotinylated neoantigen peptides directly to APCs in draining lymph nodes (dLNs). We confirmed mSA expression on the engineered antibody and its strong binding affinities to mouse CD40 and biotin. Advanced microscopy demonstrated that αCD40-mSAs enhance homing to dLNs and the intracellular delivery of neoantigen peptides to critical APC subsets, such as conventional type 1 dendritic cells (cDC1s). Effective intracellular co-delivery of αCD40-mSAs and neoantigen peptides primarily drove enhanced dendritic cell (DC) activation and antigen presentation. In vivo vaccination with peptide-loaded αCD40-mSAs elicited robust cancer-specific CD8+ T cell responses, leading to significant tumor regression and prevention in mouse tumor models. These results support αCD40-mSAs as a multifunctional vaccine delivery platform with immunopharmacological advantages by combining targeted delivery and immune stimulation in a single engineered antibody system. Our approach addresses major limitations of current cancer vaccine strategies and provides a modular platform with strong translational potential for personalized cancer immunotherapy.