Abstract 3242: Efficacy evaluation by novel humanized mouse models for preclinical study of ADCs combined with immunotherapy

Antibody-drug conjugates (ADCs) are effective anti-tumor therapies with high specificity, with little toxicity and side effects. Xenograft tumor models based on immunodeficient mice have been used for evaluating the human anti-tumor efficacy of ADCs. However, the antibody-mediated immune response of ADCs is not well evaluated in immunodeficient mice. To this end, we have developed BALB/c-hPD1 humanized mouse model to evaluate the efficacy of ADCs in combination with immunotherapy. Trastuzumab deruxtecan (T-DXd, DS-8201a) is a HER2-targeting ADC. In vitro efficacy studies showed that T-DXd effectively bound to the HER2-positive cell line SK-BR-3, resulting in strong endocytosis and induction of apoptosis. It has also been shown to kill HER2-negative MDA-MB-468 cells through a bystander effect both in vitro and in vivo. In vivo efficacy studies have demonstrated that ADCs can effectively inhibit human tumor cell growth in immunodeficient mice. In addition to human tumor cell lines, the efficacy of ADCs was also studied in BALB/c-hPD1mice engrafted with murine colon cancer cells model, and the results showed that T-DXd and Keytruda could significantly inhibit CT26-hHER2 tumor growth, with the tumor growth inhibition rates being 57% and 66%, respectively, Tumor growth inhibition rate of the combined treatment group was about 91%, which was superior compared to the efficacy of single drug treatment. The evaluation of Fc segment-mediated effect (such as ADCC, CDC and ADCP) of ADCs antibodies was carried out in humanized immune system mouse models, such as NCG-hIL15 and NCG-hSGM3. In summary, we have established a drug evaluation platform using various humanized mouse models to study the synergistic anti-tumor effects of ADCs combined with immune checkpoint blockade antibodies. Citation Format: Fang Zhu, Hongyan Sun, Qian Lu, Yuan Fang, Jianming Xu, Cunxiang Ju, Hongyu Wang, Santi Suryani Chen, Zhiying Li, Mark Wade Moore, Jing Zhao, Xiang Gao. Efficacy evaluation by novel humanized mouse models for preclinical study of ADCs combined with immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3242.