Abstract 5307: Preclinical evaluation of a potential FIC 4-1BB/CD24 bispecific antibody IBD0333
Authors: Jiang Xiaoling , Wu Chongbing , Chen Zi , Yin Liusong 
Published: March 2024

Abstract
Background: This study demonstrates the preclinical evaluation of a novel 4-1BB/CD24 bispecific antibody IBD0333. 4-1BB’s activation triggers a signaling cascade that activates both innate and adaptive immune systems. Due to the hepatotoxicity of current anti-4-1BB monoclonal antibodies, tumor-associated antigens (TAA) targeting to specifically activate immune cells in the tumor microenvironment (TME) is expected to enhance its safety profile. CD24 is highly expressed in many cancers, such as ovarian and breast cancer and its high expression is often related to poor prognosis. The signaling pathway of CD24/Siglec-10 triggers a “don’t eat me” signal that facilitates immune escape of tumor cells. Therefore, IBD0333 was designed to target CD24 overexpressed tumor cells and activate CD8+ T cells to induce T cell mediated antitumor immunity in TME of the targeted tumor tissue. To further reduce the toxicity risk, the anti-4-1BB moiety is designed to activate the signaling pathway only when IBD0333 binds to the tumor cells that overexpress CD24.
Methods: For CD24 terminus, we applied virus like particle (VLP) as antigen for immunization to obtain functional CD24 antibodies. For 4-1BB terminus, competitive ELISA/FACS analysis as well as amino acid point mutation binding ability analysis based on the receptor crystal structure were performed to characterize the binding epitope. The in vivo mice efficacy and toxicity study, as well as cynomolgus monkey toxicity study were also conducted to describe the anti-tumor activity and safety profile. For IBD0333, we verified binding affinity by FACS to cancer cells and the 4-1BB activity in reporter-gene assay. IL2 and INF-γ secretion assay were performed to evaluate the PBMC activation. C57BL/6J-h4-1BB humanized mice bearing MC38-hCD24 colon cancer cells were used to validate the anti-tumor efficacy of IBD0333. Preclinical PK and toxicity study was also performed in cynomolgus monkeys to describe the safety profile of IBD0333.
Results: IBD0333 showed excellent binding and PBMC stimulation activities. In toxicology studies of IBD0333, no obvious abnormality in mice or cynomolgus monkeys administered with IBD0333 was observed. The MTD was estimated to be greater than 200 mg/kg with no severe side effects observed in the study, showing that IBD0333 has great potential to achieve significantly improved safety profile. As to efficacy, IBD0333 showed excellent tumor inhibition activities in mice model with 99% tumor growth inhibition at 1 mg/kg and 100% at 3 mg/kg.
Conclusion: IBD0333 is a clinical stage, potential first-in-class, 4-1BB/CD24 bsAb that simultaneously stimulates both innate and adaptive immunity to achieve strong synergistic effects with reduced hepatotoxicity. The IND approvals from the FDA and the NMPA have been obtained and the Phase I clinical trial of IBD0333 in locally advanced/metastatic solid tumors or non-Hodgkin’s lymphoma is currently on-going.
Citation Format: Xiaoling Jiang, Chongbing Wu, Zi Chen, Liusong Yin. Preclinical evaluation of a potential FIC 4-1BB/CD24 bispecific antibody IBD0333 [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 5307.