Monoclonal antibodies (mAbs) targeting the human epidermal growth factor receptor 2 (HER2) are widely used in the treatment of breast, gastric, and other solid tumors. However, rapid HER2 endocytosis and recycling contribute to low response rates and treatment resistance. Here, we introduce RhuA-P, a self-assembling protein that forms uniform, micron-sized 2D arrays (2.4 × 2.4 μm) featuring spatially addressable Protein G sites for mAb conjugation. This design allows control over antibody density (22-274 molecules per array) and intermolecular spacing (57-230 nm). We show that trastuzumab (TmAb) arrays templated on RhuA-P inhibit HER2 dimerization, cluster HER2 into micron-scale inactive domains dictated by the 2D TmAb geometry, and prolong receptor membrane retention by blocking endocytosis. This sustained blockade of HER2 signaling induces oxidative stress and triggers potent apoptosis. In a murine breast cancer model, TmAb arrays exhibited superior antitumor efficacy compared to free TmAb. Moreover, the modular design of RhuA-P makes it a versatile platform for assembling other clinically relevant mAbs─such as anti-PD-1 and anti-PD-L1 antibodies─offering a generalized strategy for enhancing antibody-based therapies.
Du et al. (Mon,) studied this question.