Abstract 3361: Discovery and preclinical characterizations of a humanized anti-claudin 18.2 antibody SPX-101

Abstract Claudin 18.2 (CLDN 18.2) is a major component of the tight junctions and is highly expressed in several cancers including gastric (80%), esophageal (80%), pancreatic (60%) and lung cancers, but only expressed at very low levels in healthy tissues. The chimeric IgG1 CLDN 18.2 antibody zolbetuximab significantly improved PFS and OS in gastric cancer patients in a CLDN 18.2-dependent manner on the background of EOX. This research aimed to produce humanized anti-claudin18.2 antibodies with enhanced activities and improved pharmaceutical characteristics compared to known CLDN 18.2 antibodies. We used several immunization methods to produce mouse anti-CLDN18.2 antibodies with high affinity and excellent selectivity against CLDN 18.1. Humanization of a selected clone led to a humanized anti-CLDN18.2 antibody (h533o) with significantly improved binding affinity and cellular activity in ADCC and CDC assays compared to zolbetuximab. The binding affinity of h533o was relatively insensitive to elevated temperatures or acidity, suggesting the robustness of target engaging ability in tumor microenvironment. Maturation and selection by the off-rate approach, using phage libraries that systematically modified the CDR regions, identified multiple antibodies with comparable affinity and selectivity. Mutational scan of the Fc region in h533o identified SPX-101 with reduced ADA effect in mice while retaining other favorable properties. SPX-101 suppressed tumor growth in several xenograft mouse models including NUGC4 and HEK293 cells that stably expressed CLDN18.2. In summary, SPX-101 represents a humanized anti-CLDN18.2 antibody with high affinity and specificity, high effector cell-mediated cytotoxicity, low immunogenicity, and in vivo tumor control efficacy in xenograft rodent models. Citation Format: Guidong Zhu, Jichun Ma, Jingdong Ye, Jingdong Qin, Yi Cai. Discovery and preclinical characterizations of a humanized anti-claudin 18.2 antibody SPX-101 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3361.