Abstract 6964: A novel NSG-SGM3xIL15xDKO-based PBMC humanized mouse model to evaluate efficacy and cytokine release of immunotherapies

Abstract We have observed better engraftment of human peripheral blood mononuclear cells (PBMCs) in NSG-SGM3xIL15xDKO (SDKO) mice compared to NSG-MHC I/II DKO (DKO) mice without irradiation. Irradiation is a way to stimulate immune responses. We examined how irradiation affects human PBMC engraftment in SDKO mice and compared engraftment in irradiated SDKO and DKO mice with and without cancer cells. Efficacy and toxicity of anti-CD3xCD19 BiTE were also tested in Raji model of irradiated SDKO and DKO. Methods SDKO and DKO mice were intravenously injected with PBMCs with/without irradiation. Retro-orbital (RO) bleeding was performed to check engraftment with flow cytometry. SDKO and DKO mice were also injected with cancer cells prior to intravenous injection of PBMCs after irradiation. RO blood and spleen were collected to check engraftment of various cell types. Raji-luc-bearing SKO and DKO mice with irradiation were treated with PBS or anti-CD3xCD19 BiTE. Xenogen was performed to measure tumor burdens, and plasma was collected to measure cytokine levels with Luminex assay. Results Irradiation accelerated human CD45 (hCD45) cells engraftment in SDKO mice. On day 10 or 14, SDKO mice after irradiation showed 3 folds of hCD45 engraftment compared to SDKO mice that didn’t receive irradiation. CD3+ T cells, CD19+ B cells and CD56+ nature killer (NK) cells were engrafted at 2-6 fold higher in irradiated SDKO mice at early timepoints compared to non-irradiated mice. Irradiation significantly improved B cells and NK cells in SDKO mice compared to no irradiation. PBMCs were engrafted at higher levels in SDKO compared to DKO after irradiation. It included CD4+T cells, CD8+T cells, B cells and NK cells in the blood and spleen. On day 9, T cells, B cells, NK cells, dendritic cells (DC) and macrophages in the spleen were 2-10 fold higher in irradiated SDKO compared to DKO. B cell lymphoma Raji cells stimulated PBMCs to engraft after irradiation, including T cells, NKs and macrophages in the spleen. More importantly, SDKO was engrafted at significantly higher cell counts compared to DKO with Raji cells stimulation, including DCs and macrophages. Lastly, we found SDKO supported Raji growth with higher tumor burden on three days after implantation compared to DKO. At the same time, Raji-bearing SDKO responded to anti-CD3xCD19 BiTE faster than DKO, making SDKO a more sensitive model to test BiTE efficacy than DKO. In addition, cytokines production after anti-CD3xCD19 BiTE was much higher in SDKO than DKO in the Raji model. Conclusion Irradiation not only expediates engraftment of human PBMCs in SDKO mice. Various cell types, including B cells, NK cells, DCs and macrophages, plus T cells are engrafted at higher cell counts in SDKO than DKO with/without cancer cells stimulation with irradiation. In addition, SDKO implanted with cancer cells is a more sensitive platform than DKO to test drug efficacy and toxicity. Citation Format: Xiaoqing (Nancy) Zheng, Guoxiang Yang, Beau Parry, James G. Keck, Li-Chin Yao, . A novel NSG-SGM3xIL15xDKO-based PBMC humanized mouse model to evaluate efficacy and cytokine release of immunotherapies [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 6964.