• Immune checkpoint inhibitors targeting PD-1, PD-L1, and CTLA-4 have achieved remarkable clinical success, but preclinical validation using human immune system (HIS)–reconstituted mice remains challenging. Conventional immunodeficient models often fail to reproduce the efficacy observed in target humanized or immunocompetent mice. The poor antibody pharmacokinetics and suboptimal immune function in HIS models contribute to these discrepancies. In particular, murine innate immune cells expressing Fc gamma receptors (FcγRs) can bind therapeutic antibodies, accelerate their clearance, and induce nonspecific antibody-dependent cellular phagocytosis (ADCP), confounding efficacy assessment. Moreover, insufficient reconstitution and activation of human T cells limit immune response evaluation. Human IL15 is known to enhance T-cell survival and function following human PBMC engraftment in immunodeficient mice.
• Biocytogen developed B-NDG hIL15, FcγR KO mice by expressing human IL15 and knocking out the murine FcγR genes on the B-NDG background lacking mature T, B, and NK cells. After injection of human IgG1 antibody, binding of IgG1 to CD45+ cells was detected in B-NDG mice and B-NDG hIL15 mice, but not in B-NDG hIL15, FcγR KO mice, confirming successful gene deletion. Serum human IL15 concentration was approximately 112 pg/mL. The distribution and frequency of granulocytes, monocytes, macrophages, and dendritic cells was comparable between B-NDG hIL15 mice and B-NDG hIL15, FcγR KO mice.
• Pharmacokinetic analysis after intravenous injection of an anti–human CTLA-4 IgG1 antibody revealed that antibody clearance was fastest in B-NDG mice and slowest in B-NDG hIL15, FcγR KO mice, indicating significantly prolonged serum half-life. By engrafting human NK cells, CD34+HSCs or PBMCs into B-NDG hIL15, FcγR KO mice, it was possible to successfully establish tumor models and evaluate the in vivo efficacy of the antibody drugs.
• Application: B-NDG hIL15, FcγR KO mice can be used for engrafting human NK cells, human CD34+ HSCs and human PBMCs, and for reconstituting human NK cells, T cells and other immune cells. Various types of tumor models can be established and the in vivo efficacy and toxicity of drugs targeting NK cells and/or T cells can be evaluated.

Antitumor activity of anti-human PD-1 antibody pembrolizumab analog (in-house) in lung adenocarcinoma cell line HCC827 CDX model established with huPBMC-B-NDG hIL15, FcγR KO mice. HCC-827 cells (1.5×10⁷) were subcutaneously inoculated into B-NDG hIL15, FcγR KO mice. Mice were grouped when the tumor volume reached approximately 150 mm³, at which time they were intravenously engrafted human PBMCs (5×10⁶) and treated intraperitoneally with pembrolizumab analog with doses and schedule indicated in panel (female, 7-week-old, n=6). The results showed that pembrolizumab analog could effectively inhibit tumor growth in lung cancer CDX model established with huPBMC-B-NDG hIL15, FcγR KO mice. Values are expressed as mean ± SEM.

Antitumor activity of anti-human PD-1 antibody pembrolizumab analog (in-house) in non-small cell lung cancer cell line NCI-H1975 CDX model established with huPBMC-B-NDG hIL15, FcγR KO mice. NCI-H1975 cells (6×10⁶) were subcutaneously inoculated into B-NDG hIL15, FcγR KO mice. Mice were grouped when the tumor volume reached approximately 100-150 mm³, at which time they were intravenously engrafted human PBMCs (5×10⁶) and treated intraperitoneally with pembrolizumab analog with doses and schedule indicated in panel (female, 7-week-old, n=6). The results showed that pembrolizumab analog could effectively inhibit tumor growth in a dose-dependent manner in the lung cancer CDX model established with huPBMC-B-NDG hIL15, FcγR KO mice. Values are expressed as mean ± SEM.

Antitumor activity of anti-human PD-1 antibody pembrolizumab analog (in-house) in breast cancer cell line MDA-MB-231 CDX model established with huPBMC-B-NDG hIL15, FcγR KO mice. Human PBMCs (5×10⁶) were intravenously engrafted into B-NDG hIL15, FcγR KO mice. On the same day, MDA-MB-231 cells (1×10⁷) were subcutaneously inoculated into B-NDG hIL15, FcγR KO mice. Mice were grouped when the tumor volume reached approximately 100-150 mm³, at which time they were treated intraperitoneally with pembrolizumab analog with doses and schedule indicated in panel (female, 7-week-old, n=6). The results showed that pembrolizumab analog could effectively inhibit tumor growth in the breast cancer CDX model established with huPBMC-B-NDG hIL15, FcγR KO mice. Values are expressed as mean ± SEM.