Abstract 1285: PBMC-humanized, MHC-deficient NCG mice support growth of human tumor xenografts, do not develop rapid onset GvHD, and provide enhanced performance in oncology studies

Abstract The application of new in vivo animal models with greater translational relevance is important for successful drug development. Severely immunodeficient mouse strains engineered for enhanced engraftment and persistence of diverse human immune cell types are now widely used in drug discovery across different therapeutic areas. These models allow for testing of immune modulating agents that target specific components of the human immune system, including both lymphoid and myeloid lineages. They have been particularly useful in drug development for oncology and for evaluating cell therapies such as TCR and CAR modified T cells. One approach commonly used to generate humanized mice involves engrafting peripheral blood mononuclear cells (PBMC) into immunodeficient mice. Since PBMC humanization results in efficient engraftment of hCD3+ T cells, xenogeneic GvHD (graft versus host disease) responses can occur with some donors. GvHD responses, which are characterized by progressive weight loss and a decline in animal well-being, can significantly compromise the results of studies in human tumor-bearing mice. In the studies reported here we compared outcomes in three NCG mouse strains. The parental NCG was modified to lack either B2-micoglobulin (NCG-B2m-KO mice deficient in the expression of mouse MHC class I molecules) or a double knock out of both mouse MHC class I and MHC class II molecules (NCG-MHC-dKO mice). RKO colorectal tumor cells were implanted subcutaneously in the three NCG mouse strains (parental NCG, NCG-B2m-KO and NCG-MHC-dKO) and 7 days later mice were engrafted with 10 million PBMCs obtained from two different donors, a Reference Donor and a Rapid Engrafter known to induce GVHD. The growth of RKO tumors and engraftment kinetics of donor PBMCs was evaluated. We observed consistent RKO tumor growth in non PBMC-treated NCG mice. HuPBMC NCG mice engrafted with the Rapid Engrafter showed clear signs of GvHD and reduced tumor growth. Importantly, there was a delay in the onset and significantly reduced severity of GvHD (by body weight loss or general clinical observations) in both MHC-modified strains. The engraftment rate of PBMCs was slightly delayed in both HuPBMC NCG-b2m-KO and NCG-MHC-dKO mice. The lack of GvHD provides a compelling rationale for the use of MHC deficient NCG strains in oncology tumor model studies and cell therapy studies. Citation Format: Steven Bronson, Kyle Draheim, Christopher Currie, Sydney Scatigno, Jenny Rowe, David P. Harris. PBMC-humanized, MHC-deficient NCG mice support growth of human tumor xenografts, do not develop rapid onset GvHD, and provide enhanced performance in oncology studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1285.