Abstract 2228: PD1/CTLA4 humanized mice - A great model for pre-clinical toxicology and efficacy evaluation of macromolecular drugs

Abstract Immune checkpoint antibodies have conferred huge cancer immunotherapeutic effect (CITE). Besides, severe immunotherapy related adverse events (irAE) occurred in combination therapy such as anti-PD1 combines with anti-CTLA4 antibodies greatly limit the development of cancer therapy. Animal models which can recapitulate both clinical irAE and CITE will be benefit for developing safer immune-checkpoint-targeting reagents. However, no animal models were found can be used for preclinical safety evaluation of drugs up to now. Given this fact, PD1/CTLA4 double-humanized mice models were established in both BALB/c (BALB/c-hPD1/hCTLA4) and C57BL/6 (B6-hPD1/hCTLA4) background, which by replacing the mouse extracellular domain of CTLA4 and PD1 with human segments while retaining mouse intact intracellular part, respectively. Our data showed that strong CITE against anti-hCTLA4 treatment observed in models from both BALB/c and B6 background. Apparent inhibition of tumor growth also emerged on subcutaneously engrafted CT26 tumor in BALB/c-hPD1/hCTLA4 mice by anti-PD1/CTLA4 bispecific antibody treatment. Meanwhile, severe irAEs which have been observed in clinical patients, such as joint swelling, skin inflammation, heart damage and infiltration of inflammatory cells in different tissues and organs could be reproduced in BALB/c-hPD1/hCTLA4 mice. Consistent with previous reports, we could not observe similar irAEs under drugs treatment at the same dose in C57BL/6-hPD1/hCTLA4 mice. Our data indicated that adult BALB/c-hPD1/hCTLA4 mice, but not C57BL/6-hPD1/hCTLA4 mice, were more sensitive to irAEs. Taken together, adult PD1/CTLA4 humanized mice in BALB/c background can not only be used to screen humanized antibodies, but also have tremendous values for preclinical safety evaluation. Citation Format: Cunxiang Ju, Mingkun Zhang, Rui Mao, Ma Xiuying, Jin Tang, Shuai Li, Jingjing Wang, Hongyan Sun, Jing Zhao, Xiang Gao. PD1/CTLA4 humanized mice - A great model for pre-clinical toxicology and efficacy evaluation of macromolecular drugs [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 2228.