Tumor-antigen-specific polyclonal antibodies suppress tumor growth and metastasis in heterogeneous solid tumors

Introduction Tumor heterogeneity and signaling redundancy limit the efficacy of monospecific antibody therapies in solid malignancies. Here we used our platform of glyco-humanized polyclonal antibodies (GH-pAb), to investigate whether targeting multiple tumor-associated antigens provides integrated anti-tumor activity. Methods GH-pAb (hereinafter XON7) were generated by immunization of double-knockout pigs with human tumor cells. Antigen specificity of XON7 was assessed using a human proteome array and validated by ELISA. Anti-tumor mechanisms were evaluated in vitro on 2D or 3D-cultures. Efficacy was tested in vivo in cell or patient-derived xenograft (CDX, PDX), in chicken chorioallantoic membrane (CAM) model, and in orthotopic/metastatic triple negative breast cancer (TNBC) models. Results XON7 demonstrated tumor-restricted binding across tissue microarrays without detectable staining in matched normal tissues. Mechanistically, XON7 induced potent cytotoxicity across a wide tumor panel through complement activation, apoptosis, and antibody-dependent cellular phagocytosis. Proteome profiling identified predominant reactivities against solute carrier family 3 member 2 (SLC3A2), annexin A2 (ANXA2), and cytoskeleton-associated protein 4 (CKAP4), all broadly expressed tumor-associated surface proteins. Immunodepletion experiments revealed that concurrent targeting of these three targets was required to maintain the full anti-proliferative activity of XON7, supporting a multitarget-dependent mechanism. XON7 also induced released of high-mobility group protein box 1 (HMGB1), a hallmark of immunogenic cell death. In vivo , XON7 inhibited tumor growth in CDX and PDX models, and markedly reduced metastatic dissemination in orthotopic and intravenous TNBC models. In a CAM model, XON7 synergized with PD-1 blockade, enhancing tumor control and promoting macrophage polarization toward a M1 phenotype. Conclusion By simultaneously engaging non-redundant tumor pathways and reshaping the tumor microenvironment, XON7 may overcome key resistance mechanisms of solid tumors.