Abstract 6317: Developing a fully human heavy chain only Claudin-18.2-specific CAR-T cell therapy

Abstract

Abstract Camelid VHH/nanobodies have been widely applied as the antigen binding domain of CAR-T cell therapies due to a smaller size and simpler structure compared to the traditionally used single chain variable fragment (scFv). Additionally, camelid VHH/nanobodies provide greater flexibility for dual-targeting CAR-T cell therapies. However, camelid VHH/nanobodies require laborious and costly humanization and still have a significant risk of inducing anti-drug antibodies when administered to patients. Transgenic mice exclusively harboring the most stable human VH genes (HCAb Harbour Mice®) provide one of the best solutions to get fully human heavy chain only antibodies (HCAbs). To efficiently identify lead HCAb VHs for Claudin-18.2-targeting CAR-T cells, we developed an innovative direct CAR-function based HCAb library screening platform. From Claudin-18.2-immunized HCAb Harbour Mice®, we constructed a total VH library in a CAR lentiviral vector that we developed in-house. After producing the lentiviral particle library, we transduced a Jurkat-NFAT-GFP reporter cell line and stimulated with Claudin-18.2 overexpression cell line. Subsequently, GFP positive reporter cells, representing Claudin-18.2-specific CARs, were isolated through FACS sorting, expanded, and further stimulated with Claudin-18.2-positive NUGC-4 tumor cells. Then, Next Generation Sequencing and abundance ranking was performed on VHs recovered from sorted CAR-reporter cells. Lead VH candidates were cloned into the CAR-P2A-RFP lentiviral vector, and many of these VH clones exhibited superior Claudin-18.2-specific functionality compared to a clinically-validated reference scFv in both reporter and primary CAR-T cells. Many lead VH clones also exhibited excellent developability as soluble HCAbs. These data suggest that this innovative method of combining our fully human HCAb and CAR-based library screening platform will provide new avenues for CAR-T cell therapies. Citation Format: Jason Noon, Yao Lu, Itishree Kaushik, Oyku Ay, Adam Luk, Bradley Delaney, David DeMeritt, Musheng Bao. Developing a fully human heavy chain only Claudin-18.2-specific CAR-T cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6317.