Abstract 1600: Improved humanization of peripheral blood mononuclear cells in NSG-SGM3xIl15xDKO (SDKO) over that of NSG-MHC I/II DKO mice for immuno-oncology modeling

Abstract Introduction Immunotherapies are the largest growing therapeutics applied to cancer and autoimmune disorders, rapidly transforming the drug development landscape. Despite significant improvements in immunotherapy research and available treatments, ample variation in clinical outcomes exposes gaps in our understanding of their mechanisms of action and specific response biomarkers. The development of the NSG-MHC I/II double-knockout (DKO) mice improved significantly the availability of models that can delay graft-versus-host disease (GvHD) while still achieving strong T cells engraftment. Nonetheless, DKO mice perform better with irradiation and engraftment with high doses of PBMCs to achieve these results and there is a challenge on producing multilineage human immune subsets such as natural killer (NK) cells and myeloid populations. Here, we characterize a next-generation DKO strain, SDKO (NSG-SGM3xIL15xDKO) designed for enhanced humanization with lower PBMC doses and improved immune diversity without the need for irradiation. Methods Nonirradiated SDKO (Jax #037320, n=20) and DKO (Jax #025216, n=20) mice between 7-10 weeks of age were intravenously (IV) injected with 10 million PBMC using a total of five different donors. Mice were bled weekly via retro-orbital bleeds to assess engraftment status up for 12 weeks. Half the mice per strain were euthanized at SD21 for spleen engraftment checks. Survival was assessed up to 84 days. Conclusions Survival between the two strains was comparable throughout the entire length of the studies. The newly developed mouse strain, NSG-SGM3xIL15xDKO (SDKO) offers improved overall humanized engraftment over the industry standard NSG-MHC I/II double-knockout (DKO), with higher hCD45+ numbers than DKO strain without the need for irradiation. Also, the SDKO strain present a higher T cell subpopulation (CD4+ and CD8+), higher number of Natural Killer (CD56+) cells and B (CD19+) cells. Noteworthy, SDKO presents high number of differentiated Plasma Cells (CD138+) in the spleen, a population that is not usually observed in engrafted DKO strain. Based on these results, we conclude that the novel SDKO mice better recapitulates the development of human innate and adaptive immunity than its counterpart DKO model. Citation Format: Leandro Salati D'Abronzo, Xiaoqing (Nancy) Zheng, Beau Parry, Guoxiang Yang, Destanie Rose, Li-Chin Yao, James Keck, Jiwon Yang, . Improved humanization of peripheral blood mononuclear cells in NSG-SGM3xIl15xDKO (SDKO) over that of NSG-MHC I/II DKO mice for immuno-oncology modeling abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1600.