Abstract LB270: TCE-A: An “OR-gate” CD19×CD20×CD3 trispecific T-cell engager for B-cell malignancies and autoimmune diseases

Abstract CD19 and CD20 exhibit complementary expression patterns across B-cell non-Hodgkin lymphoma (B-NHL) subtypes. However, singletarget therapies are often compromised by two key limitations: acquired antigen loss after frontline treatment, and intrinsic tumor heterogeneity leading to variable antigen expression. To overcome these challenges, we developed TCE-A, an Fc-silenced, IgG1-based tri-specific T-cell engager (TCE) simultaneously targeting CD19 andCD20. TCE-A incorporates an affinity-tuned CD3 binder and a unique CD20 binder with epitope distinct from rituximab, enabling potential combination therapy. Beyond oncology, this tri-specific TCE also enables depletion of pathogenic B cells in autoimmune disorders. TCE-A binds CD19 and CD20 with nanomolar affinity. In Tcell/BNHL coculture assays, it mediated potent “OR-gate” concentration-dependent tumor cell killing activity, with minimal EC50 shift under competition of rituximab at saturating concentration. In Raji and JeKo-1 xenograft models, TCE-A achieved complete tumor suppression at low dose below 1 mg/kg, exhibiting a 10-fold dose window. Furthermore, in a patient-derived PBMC-induced SLE mouse model, TCE-A significantly reduced human IgG and anti-dsDNA IgG in serum and prevented renal IgG deposition and associated pathology. Pharmacokinetic and pharmacodynamic evaluation in cynomolgus monkeys showed favorable profile with a half-life of ∼4-5 days, accompanied by rapid and sustained peripheral B-cell depletion for at least 14 days and parallel reductions in serum IgG/IgM. TCE-A also exhibits excellent stability and developability, suitable for subcutaneous administration, which may potentially mitigate treatment-related toxicities, particularly cytokine release syndrome in the clinical setting. In summary, TCE-A demonstrates potent dual-target activity against B-cell malignancies and autoimmune disease models. Its rituximab-compatible epitope, high efficacy and differentiated pharmacokinetic/developability, warrant further clinical development for B-NHL and autoimmune indications. Citation Format: Hanxiao Ying, Emily Wu, Sizhu Duan, Dongmei Bai, Jing Wang, Pu Pu, Limin Zhang, Chunyue Wang, Min Hu, Feng He. TCE-A: An “OR-gate” CD19×CD20×CD3 trispecific T-cell engager for B-cell malignancies and autoimmune diseases abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86 (8Suppl): Abstract nr LB270.