32 (PB022) - Humanized mouse models for preclinical evaluation of novel immune therapies, checkpoint inhibitors and immune cell engagers

Abstract

Background: The preclinical evaluation of novel immune therapies demands humanized mouse models with functional human immune cells. In previous studies we have established a humanized immune system with functional T- B- and NK cells, as well as monocytes in immunodeficient mice by transfer of hematopoietic stem cells (HSCs) or peripheral blood mononuclear cells (PBMC). By transplantation of cell-line-derived (CDX) or patient-derived (PDX) tumor xenografts on humanized mice, we successfully generated a full human tumor-immune-cell model for different tumor entities. Finally, we validated the functionality of these models using checkpoint inhibitors or immune cell engagers. Methods: HSC-humanized mice were generated by single i.v. transplantation of CD34+ stem cells to immunodeficient NOG mice. Engraftment of immune cells was monitored by FACS analysis of blood samples. CDX and PDX from different entities were transplanted on the humanized mice. PBMC or isolated T- or NK-cell preparations were used to humanize mice by single or multiple i.v. injections into tumor-bearing mice or with simultaneous tumor cell transplantation. These models were used to evaluate immune checkpoint inhibitors. Blood and tumor samples were analysed by FACS and immunohistochemistry for immune cell infiltration and activation. Results: The transplanted HSCs engrafted in mice and established a functional human differentiated immune system with proliferating immune cells. Up to 20% of the human immune cells in the blood were functional T cells, characterized by a high PD-1 expression 14 weeks after HSC inoculation. Selected CDX and PDX tumors successfully engrafted on humanized mice without significant differences in tumor growth compared to non-humanized mice. Checkpoint inhibitor treatments induced tumor growth delay in selected models. FACS analysis of xenograft tumors revealed an increased percentage of tumor-infiltrating T cells. In addition, we identified a set of CDX and PDX models without interference with parallel injection of PBMC, T- or NK-cell preparations for the evaluation of immune cell engagers and other immune therapeutics. Conclusions: We established human tumor-immune-cell models of different entities using CDX or PDX in combination with different donor derived immune cell subsets as effector cells. We demonstrated successful engraftment of HSCs on immunodeficient mouse strains generating mice with a functional human hematopoiesis. These models have been employed for preclinical evaluation of novel checkpoint inhibitors and immune cell engagers. Our human tumor-immune-cell models allow preclinical, translational studies on tumor immune biology as well as evaluation of new therapies, drug combinations and biomarker identification and validation. No conflict of interest.