Abstract 621: ZL-1211 exhibits robust anti-tumor activity by enhancing ADCC and activating innate and adaptive immunity in CLDN18.2-high and -low expressing gastric cancer models

Abstract

Abstract CLDN18.2 (Claudin18.2)-targeting therapeutic antibodies have shown promising clinical efficacy in ~30% of gastric cancers expressing high levels of CLDN18.2 and less pronounced activity in the majority of low expressing malignancies. ZL-1211 is a monoclonal antibody targeting CLDN18.2 engineered to promote enhanced ADCC with the goal of achieving more potent activity in a wider spectrum of high- and low-CLDN18.2 expressing tumors than the leading clinical benchmark. To further assess the potency of ZL-1211, we utilized a panel of gastric tumor cell lines that endogenously express CLDN18.2 and more accurately reflect target levels in human gastric tumors than engineered overexpressing models. ZL-1211 demonstrated more robust in vitro ADCC activity than clinical benchmark not only in CLDN18.2-high but also -low expressing gastric cell lines. Greater anti-tumor efficacy was also observed in mouse xenograft models with CLDN18.2-high, -medium, and low-expressing gastric cell lines in response to treatment with ZL-1211 compared to the clinical benchmark. NK cell depletion abrogated ZL-1211-mediated ADCC activity in vitro. ZL-1211 efficacy in vivo was also dependent on the presence of an NK compartment, as CLDN18.2-expressing gastric tumors grown in Balb/c nude with an intact NK function were sensitive to ZL-1211 treatment, while NOD-SCID with partially competent NK activity exhibited minimal response, and NCG without NK cells did not display any evidence of in vivo efficacy. Strikingly, NK cells strongly induced an inflammatory response in response to ZL-1211 treatment, including increased IFNγ, TNFα, and IL-6 production. Interestingly, ZL-1211 treatment led to NK cell and monocyte stimulation and enhanced CD8+ T cell activation, suggesting a mechanism of action that not only involves innate but also adaptive immunity. Taken together, our data suggest that ZL-1211 more effectively targets CLDN18.2-high gastric cancers as well as -low expressing malignancies that are not eligible for treatment with the leading clinical benchmark by inducing a robust ADCC response and activating innate and adaptive immunity to enhance anti-tumor efficacy. Clinical activity of ZL-1211 is currently under evaluation in a Phase I clinical trial (NCT05065710). Citation Format: Hiroyasu Konno, Tracey Lin, Bee-Chun Sun, Renyi Wu, Christopher Szeto, David Bellovin, Karl Hsu, Omar Kabbarah. ZL-1211 exhibits robust anti-tumor activity by enhancing ADCC and activating innate and adaptive immunity in CLDN18.2-high and -low expressing gastric cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 621.