BCG024:一种新型DLL3×CD3×4-1BB三特异性T细胞衔接器,在临床前模型中增强T细胞持久性和功能

Background: CD3-based T cell engagers (TCEs) as powerful therapeutic agents have demonstrated clinical success in both hematologic malignancies and solid tumor indications. One major obstacle to TCE therapies in treating solid tumors is T-cell exhaustion due to conventional TCEs lacking co-stimulatory signaling, limiting their therapeutic durability. To address this challenge, integrating a co-stimulatory signal such as 4-1BB into TCEs could be an attractive approach to enhance T cell function and durability. Methods: We developed a trispecific antibody (TriAb) targeting DLL3, CD3, and 4-1BB using a VHH 4-1BB agonist derived from RenNano ® mice to achieve tumor antigen-dependent co-stimulation. In vitro assays included repeated stimulation assay and cytotoxicity against DLL3-positive small cell lung cancer (SCLC) cell line. In vivo efficacy and T cell proliferation were evaluated in xenograft mouse models bearing established SCLC tumors. The toxicity study was evaluated in CD3ε×4-1BB humanized mice. Results: The DLL3 TriAb demonstrated significantly enhanced T cell proliferation while maintaining high cell viability and cytotoxicity following repeated stimulation. However, the benchmark and bsAb counterparts showed marked reductions in cell viability and activity. In vivo , mice treated with benchmark caused dose-dependent reductions in serum T cell number, whereas those treated with DLL3 TriAb maintained stable T cell populations. That indicated TCE integrated 4-1BB nanobody co-stimulation indeed enhances T cell durability and functionality. In SCLC xenograft models, DLL3 TriAb exhibited robust antitumor efficacy in a monovalent antigen-binding format rather than a bivalent antigen-binding format. Notably, contrasting with non-specific TriAb controls, DLL3 TriAb displayed favorable safety profiles in CD3ε×4-1BB humanized mice even at high doses, with no significant body weight loss or systemic cytokine elevation observed. Conclusions: Our DLL3×CD3×4-1BB TriAb demonstrates tumor-dependent co-stimulation, enhanced T cell persistence and functionality, further exhibiting superior anti-tumor efficacy in preclinical SCLC model and good safety profiles at high dose. These findings highlight the DLL3 TriAb as a next-generation immunotherapy, offering enhanced T cell functionality and clinical translatability.