Bispecific antibody-drug conjugates targeting EGFR and LGR5 exert potent antitumor activity in colorectal cancer models

Colorectal cancer (CRC) remains a significant contributor to cancer-associated deaths worldwide, indicating the need for new therapeutic targets and modalities. Antibody-drug conjugates (ADCs) have demonstrated remarkable potential for the treatment of various cancer types, although their efficacy as monotherapies is often limited by insufficient targeting of tumor heterogeneity, dose-limiting toxicities, and drug resistance. Accordingly, multi-targeting therapeutic strategies, such as bispecific ADCs (bsADCs), which simultaneously target two cancer-associated antigens or non-overlapping epitopes on the same antigen, may prove more effective at overcoming resistance and eliminating tumors compared to monospecific ADCs. In this work, we describe the development of EGFR:LGR5 bispecific antibodies (bsAbs) and bsADCs. EGFR:LGR5 bsAbs were shown to internalize to the lysosome to a greater extent than EGFR- and LGR5-targeting monoclonal antibodies (mAbs) and drive EGFR lysosomal degradation in an LGR5-mediated fashion. However, EGFR:LGR5 bsAbs exerted suboptimal cytotoxicity in CRC cell lines. We therefore engineered an EGFR:LGR5 bsADC that demonstrated 100- to 1000-fold enhanced efficacy over a previously developed LGR5-targeting monospecific ADC (8E11-CPT2) with an identical linker-payload in CRC cell lines of various genetic backgrounds and EGFR and LGR5 expression levels. EGFR:LGR5 bsADC potency was strongly correlated with cell line sensitivity to the CPT2 payload. EGFR:LGR5 bsADC induced tumor regression in select RAS ^MUT CRC xenograft models and demonstrated superior antitumor activity and prolonged survival benefit in all evaluated models versus EGFR mAb cetuximab (CTX), bsAb, and 8E11-CPT2. These findings strongly support the further development of EGFR and LGR5 dual-targeting approaches for CRC and other EGFR- and LGR5-expressing malignancies.