Abstract 2394: A novel 2+2 IgG-like bispecific antibody-drug conjugate targeting EBV GP220/350 and EGFR for selective treatment of nasopharyngeal carcinoma.

Abstract Nasopharyngeal carcinoma (NPC) is endemic in East and Southeast Asia, with Epstein-Barr virus (EBV) infection as a primary etiological factor. The EBV envelope glycoprotein GP220/350 is highly expressed on EBV-positive NPC cells, serving as a tumor-specific antigen. Epidermal growth factor receptor (EGFR) is also overexpressed in 80% of NPC cases and is a validated therapeutic target (e.g., cetuximab). Bispecific antibodies (bsAbs) offer unique advantages by co-targeting two antigens, enhancing tumor selectivity and internalization efficiency. Here, we report the development of a 2+2 IgG-like bispecific antibody-drug conjugate (ADC) co-targeting GP220/350 and EGFR for precise NPC therapy. The bsAb was engineered as a 2+2 IgG-like molecule. The GP220/350-binding arm was derived from a fully humanized synthetic VHH (single-domain antibody) library and a high affinity binder C2 was selected via phage display. The EGFR-binding arm was based on nimotuzumab, a low-affinity EGFR antibody chosen to minimize on-target/off-tumor toxicity. The bsAb designated as DXA038 was conjugated to a topoisomerase I inhibitor payload CPT113 via a cleavable linker, with an average drug-to-antibody ratio (DAR) of 4. Binding affinity, in vitro cytotoxicity and in vivo efficacy were assessed. DXA038-CPT113 showed superior activity both in vitro and in vivo compared to nimotuzumab-CPT113. This bispecific ADC represents a promising therapeutic strategy for EBV-positive NPC, addressing unmet needs in precision oncology. Citation Format: Saihong Yu, Yunxia Zheng, Junxiang Jia, Xiangfei Kong, Juan Wang, Yi Luo, Hangbo Ye, Xueqing Ma, Qingliang Yang, Robert Y. Zhao. A novel 2+2 IgG-like bispecific antibody-drug conjugate targeting EBV GP220/350 and EGFR for selective treatment of nasopharyngeal carcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2394.