Chemical-Assembled Macrophage-Engaging Glypican-3 × Signal Regulatory Protein-α (SIRP-α) Bispecific Antibody for Immunotherapy Against Liver Cancer

Abstract

Bispecific antibodies (BsAbs) represent a growing class of cancer immunotherapeutics, yet their wider adoption remains limited by complex recombinant production and limited manufacturing efficiency. Here, we report a chemically assembled macrophage-engaging glypican-3 × signal regulatory protein-α (SIRP-α) bispecific antibody for the treatment of liver cancer. Using our bifunctional linker, glypican-3-binding peptide dimers were conjugated to a native anti-SIRP-α IgG via a rapid one-pot, two-step process, yielding a novel dendritic bispecific antibody (dBsAb). Such a construct simultaneously targets glypican-3-positive hepatocellular carcinoma cells and blocks the CD47–SIRP-α axis, thereby promoting macrophage engagement and phagocytosis. In vitro studies showed substantially enhanced macrophage adhesion and tumor cell clearance compared with the monoclonal antibody. In an in vivo experiment, dBsAb demonstrated a 68% reduction in tumor growth, with increased macrophage infiltration, M1 polarization, and elevated antigen presentation without observable systemic toxicity. This chemical assembly approach offers a practical alternative to recombinant methods for constructing bispecific antibodies and may facilitate the development of macrophage-directed immunotherapies.

Keywords

bioconjugation / bispecific antibody / immunotherapy / macrophage-engager

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