An immune stimulator-antibody conjugate (ISAC) composed of a monoclonal antibody targeting human epidermal growth factor receptor 2 (EGFR2; HER2; ErbB2) conjugated to a not yet disclosed immune stimulator, with potential antineoplastic and immunostimulating activities. Upon administration of the anti-HER2 immune stimulator-antibody conjugate NJH395, the antibody moiety targets and binds to HER2 expressed on tumor cells. Upon antibody/antigen binding, the immune-stimulating moiety may, through an as of yet undisclosed mechanism, enhance the immune-mediated killing of HER2-expressing tumor cells. HER2, a tyrosine kinase receptor, is overexpressed in many cancer types and plays a key role in tumor cell proliferation and tumor vascularization.