Abstract 1645: Advancing the development of CD16A-based bispecific antibodies in humanized CD16A mouse models

Abstract Antibody-dependent cell cytotoxicity (ADCC) is an important mechanism in immunotherapy. CD16A (FcγRIIIA), a low-affinity receptor for the IgG Fc domain, facilitates ADCC and is responsible for triggering the lysis of target cells by natural killer (NK) cells. Human CD16A is closely related to mouse Fcgr4 and is expressed in NK cells and macrophages, but is absent in granulocytes. Alternatively, mouse Fcgr4 is expressed in granulocytes and macrophages and is absent in NK cells. CD16A-based bispecific antibodies targeting NK cells have been studied for cancer therapy. To evaluate the anti-tumor efficacy of CD16A-based bispecific antibody in mouse tumor models, we have successfully generated a novel humanized CD16A knock-in mouse strain (B-hCD16A Mice). Considering the differential expression patterns between human CD16A and mouse Fcgr4, the regulatory region and whole genome sequence of mouse Fcgr4 were replaced by the human CD16A gene. Human CD16A and mouse Fcgr4 protein expression was confirmed in heterozygous B-hCD16A mice by FACS and RT-PCR. Human CD16A protein was detected in NK cells and macrophages of B-hCD16A mice, but not granulocytes. When compared with wild type mice, there were no abnormalities in the populations of immune cells in B-hCD16A mice. CD16A-based bispecific antibody usually binds to CD16A on NK cells, whereas the other arm of the antibody binds to tumor antigen on cancer cells. Initial assessment of the tumorigenicity of MC38 cells were evaluated in B-hCD16A mice, and results indicated that these cancer cells were able to establish tumors in vivo. These data suggest that the B-hCD16A mouse model is an effective tool for future in vivo efficacy evaluation of therapeutic CD16A-based bispecific antibodies prior to clinical development. Citation Format: Jiahui Chang, Tao Li, Limei Ma, Xiaoxia Sun, Yuelei Shen. Advancing the development of CD16A-based bispecific antibodies in humanized CD16A mouse 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 1645.