Abstract 5195: BNDG B2m KO plus mouse model is a powerful tool for immunotherapy
Authors: Jiang Hongmei , Xiao Jianqiu , Rothrock Travis 
Published: April 2023

Abstract
The B-NDG (Biocyotgen; NOD; DNAPK null; IL2rg knockout) mouse model was developed to be an ideal testing platform for anti-tumor therapies in Cell-Line and Patient Derived Xenograft Models (CDX and PDX respectively). B-NDG mice exhibit several notable advantages over classical NOD-scid mice, including increased life span, NK cell deletion, and significantly improved xenograft efficiency. However, like the NOD-scid mice, the utility of B-NDG mice in long-term studies is severely limited by a high incidence of severe and early-onset GvHD (Graft versus Host Disease) - limiting experimental durations to as little as 30 days. To reduce the incidence and severity of GvHD in B-NDG mice, Biocytogen developed the B-NDG B2m KO plus mice. B-NDG B2m KO plus mice was generated using Cas9 approach. Specifically, endogenous mouse B2m was deleted, while B2m cDNA was fused with Fcgrt. MHC Class I and Class II expressions, and immune markers were verified by flow cytometry. Concentration of i.v. administered human IgG was quantified by ELISA. CDX models were generated, and antitumor therapies were administered using established protocols described below. Compared with NOD-scid and B-NDG mice, B-NDG B2m KO plus mice showed undetectable MHC Class I expression in all tested tissues, without compromising MHC Class II expression. Moreover, no significant change in immune profiles or IgG turnover was detected, demonstrating highly targeted disruption of MHC Class I expression in B-NDG B2m KO plus mice. In the human PBMC-induced GvHD model, B-NDG B2m KO plus mice showed significantly improved survival, delayed onset and reduced clinical severity throughout the course of the model. Compared with B-NDG mice, B-NDG B2m KO plus mice exhibits significantly prolonged usefulness, demonstrating utility for up to 50 days after engraftment. To demonstrate the advantages of our B-NDG B2m KO plus mouse model, we conducted two proof-of concept studies that are often limited by GvHD. In the first study, B-NDG B2m KO plus mice were engrafted with human PBMCs and tumorigenic RKO cells on Day 0 and 14 respectively, treated with either vehicle or pembrolizumab and ipilimumab on Day 20, and observed until Day 48. Pembro/ipi treatment significantly inhibited tumor growth. In the second study, B-NDG B2m KO plus mice were engrafted with tumorigenic human NCI-H226 cells on Day 0, treated with either vehicle or CAR-T cells (5E5) once tumor size reached ~150 mm3 (around Day 20), and observed until Day 56. CAR-T treatment significantly suppressed tumor growth. Together, these studies demonstrated that the B-NDG B2m KO plus mouse model is a powerful tool for extended term anti-tumor studies, especially for studies involving immuno- and CAR-T therapies.
Citation Format: Hongmei Jiang, Jianqiu Xiao, Travis Rothrock. BNDG B2m KO plus mouse model is a powerful tool for 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 5195.