Anti-tumor efficacy and Vδ2 T-cell activation via EGFR antibody-drug conjugates featuring novel aminobisphosphonates

Antibody-drug conjugates (ADCs) represent a promising strategy in cancer therapy, enabling the targeted delivery of cytotoxic agents to tumor cells. In this study, we developed and characterized novel ADCs combining the anti-EGFR monoclonal therapeutic antibody Cetuximab (Cet) with two aminobisphosphonates (N-BPs) analogues of zoledronic acid (ZA): DC310 and the aminothiazole DC315. These conjugates aim to enhance antitumor efficacy of Cet in colorectal cancer (CRC) by both directly inhibiting tumor cell growth and activating Vδ2 T lymphocytes. We optimized the drug-antibody ratio (DAR), achieving significantly higher DARs compared to previously reported Cet-ZA conjugate, particularly with Cet-DC315 (DAR ≈ 23). Both ADCs retained selective EGFR binding in CRC cell lines and patient-derived organoids (PDO). Functionally, Cet-DC315 markedly inhibited proliferation of EGFR⁺ CRC cell lines in conventional cultures and 3D spheroids. Furthermore, Cet-DC-315 uniquely induced expansion and cytotoxic activation of Vδ2 T cells in co-cultures with CRC cell lines, PDO, and primary tumor samples. These findings suggest that ADCs incorporating novel N-BPs such as DC315 represent a potent approach for dual antitumor targeting through direct cytostatic effects and immune activation, offering a potential therapeutic advantage in the treatment of EGFR⁺ colorectal cancer.