Abstract 3497: A chimeric antibody-based gamma/delta TCR targeting GPC3 overcomes low antigen expression in liver cancer therapy

Chimeric antigen receptor (CAR) T cell therapy is a promising approach for cancer treatment; however, its effectiveness in solid tumors is hindered by challenges such as antigen escape due to mutations, heterogenous expression, and immunosuppressive tumor microenvironment. Previously, we developed CAR-T cells targeting glypican-3 (GPC3) for liver cancer using a humanized GPC3-specific monoclonal antibody (hYP7) and human single-domain antibody (HN3). The hYP7 CAR-T cells demonstrate tumor regression in preclinical mouse models and are being used to treat liver cancer patients in a clinical trial at the NIH. In this study, we analyzed clinically-relevant mutations in GPC3 transcripts observed in hepatocellular carcinoma (HCC) patients through RNAseq analysis. Produced the GPC3 variant proteins, and tested whether these mutations may functionally reduce the effectiveness of CAR-T therapies targeting GPC3. We also developed an engineered antibody-gamma/delta TCR (AbTCR) targeting GPC3, incorporating hYP7 and HN3 antibodies against two distinct epitopes on C and N lobes of GPC3, respectively. In an HCC mouse model with low GPC3 antigen density, the GPC3-targeting AbTCR demonstrated superior tumor control and improved overall survival compared to CAR-T cells, attributable to its robust antigen-binding capacity and enhanced tumor infiltrations. Our RNA sequencing analysis revealed a unique set of upregulated genes in tumor-infiltrating AbTCR-T cells compared to CAR-T cells. These genes were associated with T cell functionality and persistence, particularly pathways involving NF-κB and NFAT signaling. The functional analysis data highlight the GPC3-targeting AbTCR as a new potent therapeutic approach for HCC. Citation Format: Dan Li, Tianyuzhou Liang, Hsi-En Tsao, Laura Hutchins, Madilyn Gaydos, Chin-Hsien Tai, Jing Bian, Maggie Cam, Hongbing Zhang, Cheng Liu, Mitchell Ho. A chimeric antibody-based gamma/delta TCR targeting GPC3 overcomes low antigen expression in liver cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3497.