Thus, IgG1-DE/GM targeting two breast cancer–associated antigens, HER2 and FRα, delivered at suboptimal concentrations demonstrated superior tumor growth restriction, prolonged survival of mice, induced immune cell infiltration in tumors, and sustained circulating NK cell and activated monocyte levels compared with the IgG1-WT counterparts in vivo, despite faster clearance of IgG1-DE/GM. Here, ERBB2 is linked to breast cancer.