Multiparatopic antibodies overcome tyrosine kinase inhibitor resistance by inducing lysosomal degradation of EGFR mutants.

Acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) remains a major challenge in the treatment of non-small cell lung cancer (NSCLC). To address this issue, we developed a novel therapeutic strategy based on multiparatopic antibodies that induce targeted degradation of EGFR, independent of driver mutations typically residing in the cytosolic domain. We engineered nanobodies (Nbs) recognizing four distinct epitopes within the EGFR extracellular domain into biparatopic and triparatopic antibody formats. These antibodies effectively promoted EGFR clustering, endocytosis, and lysosomal degradation, resulting in potent suppression of downstream signaling and cell proliferation in NSCLC cell lines carrying diverse EGFR mutations, including those resistant to osimertinib. The degradation process was epitope-dependent and mediated through a dynamin-dependent endocytic pathway. Triparatopic antibodies exhibited superior antitumor efficacy compared to both biparatopic antibodies and osimertinib in xenograft models of TKI-sensitive and TKI-resistant NSCLC cells. Moreover, these antibodies displayed additive effects when combined with osimertinib. We further demonstrated that this degradation mechanism extends beyond EGFR, as antibody-mediated crosslinking similarly triggered PD-L1 degradation. Collectively, this study indicates multiparatopic antibodies as a potent and mechanistically distinct strategy to overcome TKI resistance by directly degrading the target oncoprotein, with broad applicability to other pathogenic cell surface proteins.