A bispecific ADC against CCR8 and TNFR2 elicits potent antitumor efficacy

Tumor-infiltrating regulatory T (Ti-Treg) cells play a pivotal role in suppressing antitumor immune responses within tumor microenvironment. Targeted depletion of Treg cells has emerged as a promising strategy to enhance antitumor immunity. However, current approaches such as antibody-drug conjugates (ADCs) that target a single Treg-associated antigen often suffer from limited specificity and efficacy. Here, we developed four formats of bispecific antibodies (BsAbs) targeting mouse C–C motif chemokine receptor 8 (CCR8) and tumor necrosis factor receptor 2 (TNFR2), two surface markers predominantly expressed on Treg cells. These BsAbs were efficiently expressed with retained high-affinity binding to both antigens. By conjugation with pyrrolobenzodiazepine (PBD) dimer payload using a cleavable linker, the resulting bispecific ADCs (BsADCs) exhibited potent cytotoxic activity in vivo . In murine syngeneic tumor models, BsADCs significantly suppressed tumor growth and exhibited superior therapeutic efficacy over monospecific ADCs, achieving complete tumor regression in 4 out of 5 mice (80%). Collectively, our findings have established a BsADC-based strategy for selective Treg depletion, providing a novel immunotherapeutic approach for solid tumors.