Abstract 1650: Humanized mouse models for preclinical evaluation of novel immune cell therapies, checkpoint inhibitors, and immune cell engagers
Authors: Stecklum Maria , Wulf-Goldenberg Annika , Brzezicha Bernadette , Walther Wolfgang , Hoffmann Jens 
Published: June 2022

Abstract
Background The preclinical evaluation of novel immune therapies demands humanized mouse models with functional human immune cells. In previous studies we have demonstrated, that either peripheral blood mononuclear cells (PBMC), subsets of PBMCs like T- and NK-cells or hematopoietic stem cells (HSC) can be used to establish a humanized immune system with functional T-, B-, and NK cells, as well as monocytes and dendritic cells in immunodeficient mice. 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 like Ipilimumab (Ipi), Nivolumab (Nivo), Pembrolizumab (Pembro), cell therapies and immune cell engagers.
Methods HSC-humanized mice were generated by i.v. transplantation of CD34+stem cells to immunodeficient NOG mice. PBMC or isolated T- or NK-cell preparations were used to humanize mice by single or multiple i.v. injections. CDX and PDX from different entities (i.e. lymphoma, neuroblastoma, and breast cancer) were transplanted on those humanized mice. These models were used to evaluate novel immune therapies. Blood and tumor samples were analysed by FACS for immune cell infiltration and activation.
Results The transplanted HSCs engrafted in mice and established a functional human immune system with proliferation and differentiation. 14 weeks after HSC inoculation up to 20% of the human immune cells in the blood were functional T-cells, characterized by a high PD-1 expression. The 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 tumors revealed an increased percentage of tumor infiltrating T-cells. 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 cell therapies.
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 HSC on immunodeficient mouse strains, generating mice with a functional human hematopoiesis. These models have been employed for preclinical evaluation of novel checkpoint inhibitors, cell therapies and immune cell engagers. Our models allow preclinical, translational studies on tumor immune biology as well as evaluation of new therapies, drug combinations and biomarker identification and validation.
Citation Format: Maria Stecklum, Annika Wulf-Goldenberg, Bernadette Brzezicha, Wolfgang Walther, Jens Hoffmann. Humanized mouse models for preclinical evaluation of novel immune cell therapies, checkpoint inhibitors, and immune cell engagers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1650.