Tumor Immunotherapy Mediated By Bispecific Antibodies Targeting B7-H3

B7-H3 plays an important role in tumor adhesion,invasion,migration,angiogenesis,and evasion of immune surveillance.High B7-H3 expression has been detected in multiple human solid tumor tissues.In patients,B7-H3 overexpression correlates with decreased T cell infiltration,increased metastasis,poor prognosis,advanced clinical stage,and resistance to therapy.Furthermore,B7-H3 expression is limited at low levels in healthy tissues.Collectively,B7-H3 is a potential target for solid tumors treatment.The dual-targeting strategy of bispecific antibodies(bs Abs)have great cancer therapeutic prospects.Currently,various bs Abs for cancer therapy are under clinical development,and bispecific T cell engager(bs TCEs)represent the largest group.The strategy involving redirection of effector T cells to kill target cells demonstrate significant potential in cancer immunotherapy.In this study,we generated a novel antihuman B7-H3 monoclonal antibody and demonstrated its binding activity via proteinbased and cell-based assays.We then developed a novel format anti-B7-H3×anti-CD3 bispecific antibody(B7-H3×CD3),which has an asymmetric structure that binds to both CD3 and B7-H3 monovalently,in which the anti-CD3 single-chain variable region(sc Fv)is linked at the C-terminus of the light chain of the monovalent anti-B7-H3 antibody.We evaluated the antitumor effect of B7-H3×CD3 bispecific antibody using in vitro and in vivo experiments,and explored its mechanisms.The results suggest that B7-H3×CD3 can promote the infiltration of T cells in tumor tissue,and improve the activation and proliferation of T cells,thereby enhancing the killing effect of T cells on tumor cells and inhibiting tumor growth.FcαRI(CD89)is an Ig A Fc receptor,which is expressed on the surface of myeloid cells such as monocytes,neutrophils,macrophages,eosinophils and some dendritic cells(DC)subgroups,and its binding to Ig A immune complexes can induce antibodydependent cell-mediated cytotoxicity(ADCC)and antibody dependent cell induced phagocytosis(ADCP)effects of immune cells to promote inflammation.Tumor associated macrophages(TAMs)are important component of tumor microenvironment.TAMs are involved in tumor invasion,metastasis process and suppress immune response by secreting growth factors and matrix proteases into tumor microenvironment.The number of TAMs in tumor tissues is positively correlated with the poor prognosis of patients.Therefore,the recruitment of TAMs via anti-CD89 antibody to exert ADCC and ADCP effects and participate in anti-tumor immunity is expected to improve the effect of anti-solid tumor treatment.In this study,we developed a novel B7-H3×CD89 bispecific antibody based on the structure of the B7-H3×CD3bispecific antibody.In vitro and in vivo experiments have shown that B7-H3×CD89bispecific antibody can promote the infiltration of macrophages into tumor tissues and decrease the proportion of M2 macrophages,thereby promoting the phagocytosis of tumor cells by macrophages and inhibiting tumor growth.In summary,a new anti-B7-H3 monoclonal antibody was developed and two novel bispecific antibodies,B7-H3×CD3 and B7-H3×CD89,were successfully constructed based on this new antibody in the present study.Furthermore,in vitro and in vivo studies have showed that these bispecific antibodies have the potential to treat B7-H3-positive solid tumors,laying the foundation for their application in targeted solid tumor treatment research.In summary,an anti-B7-H3 monoclonal antibody with good performance was developed,and two novel bispecific antibodies,B7-H3×CD3 and B7-H3×CD89,were successfully constructed based on this new antibody.The two antibodies can mediate high-efficiency anti-tumor activity and have the potential to treat B7-H3 positive solid tumors.At the same time,in addition to targeting the B7-H3 target,the antibodies structure designed in this study can also be used for other tumor antigen targets,and it is expected to develop a series of bispecific antibody drugs.