Background Increasingly complex molecules developed to treat cancer; i.e. immuno-oncology bispecifics, antibody-drug-conjugates, cell therapy, various cell checkpoint inhibitors, demands mouse model systems able to handle complex biological hypotheses. Evolution of the immune-humanized mouse has allowed scientists to directly test human tumors and molecules in these mice without the need for surrogate molecules. First generations of immunocompromised mice used for human immune cell engraftment, support only human T cell populations. With the generation of more complex biological molecules, there is demand for a mouse model system representing broader human immune cell repertoire.

Methods The NSG™ and NSG-SGM3 mice developed by The Jackson Laboratory are extremely immunodeficient mice carrying mutations rendering deficiencies in murine B cell, T cell and in the case of the NSG-SGM3, dysfunctional NK and myeloid cells. The NSG-SGM3 strains are further genetically modified to express human IL3, GM-CSF and KITLG, which allows for enhanced engraftment of diverse human hematopoietic lineages. Here we showcase data from a collaboration between AstraZeneca and The Jackson Laboratory in which we compare five mouse strains engrafted with the same CD34 cord blood hematopoietic stem cell donors; NSG, NSG-Tg(Hu-IL15), NSG-FLT3, NSG-SGM3 and NSG-SGM3-IL15 strains, all having modifications which promote enhanced T cell, myeloid or NK cell engraftment. This is the first direct comparison of human immune cell engraftment across these immunocompromised mouse strains. Mice were engrafted with the two CD34+ HSC donors at The Jackson Laboratory and then transferred to AstraZeneca at 4 weeks post engraftment for bi-weekly assessment of CBC differentials, body condition and phenotyping of human immune cells in blood. Half the mice from each strain were implanted with a NSCL tumor line NCI-H460. When tumors reached ~1500mm³, tissues were taken for phenotypic and functional assessment by flow cytometry and testing of cytokine levels by ELISA. The non-tumor bearing mice were allowed to progress out to 22 weeks post engraftment and then similar tissue testing was completed.

Results We show all strains have similar kinetics for engraftment of immune cells, however each strain has varying levels of immune cell populations in periphery and lymphoid tissues.

Conclusions This comprehensive engraftment data not only shows that these mouse strains engraft a broader range of human immune cells but allows for researchers to choose the appropriate immune-humanized mouse strain best suited to their molecule and specific biological questions.

Ethics Approval The animals run in these in vivo studies were humanely treated and housed according to Institutional Animal Care and Use Committee approved protocols in the Laboratory Animal Resources facility at AstraZeneca, an Association for Animal Accreditation of Laboratory Animal Care and United States Department of Agriculture-licensed facility.

Consent Written informed consent was obtained from the patient for publication of this abstract and any accompanying images.