Abstract 6968: Preclinical assessment of cell, gene, and antibody therapies using humanized mice

Abstract The preclinical assessment of cell, gene, and antibody therapies is substantially more predictive when performed in humanized immune system (HIS) mice engrafted with human tumors than in immunodeficient or syngeneic models. Here, we present a series of studies illustrating how HIS mice enable evaluation of efficacy, persistence, biodistribution, and safety for diverse therapeutic modalities in ways not achievable in other mouse systems.In the therapeutic antibody category, we first show that HIS mice reconstituted with hematopoietic stem cells from different donors recapitulate the inter-patient heterogeneity observed in responses to immune checkpoint inhibitors (ICIs), and that combining ICIs with macrophage-targeting antibodies markedly enhances antitumor efficacy. In complementary studies, we used HIS mice to rank three engineered variants of T-cell engagers (TCEs) and, separately, three variants of antibody-drug conjugates (ADCs) on the basis of both efficacy (tumor growth inhibition) and safety (systemic IFN-γ, body-weight loss, and survival), identifying the top-performing lead in each class. We also compared the activity of a TCE as a single agent versus a tumor-targeting antibody (TTA) and their combination. Finally, we conducted dose-response efficacy studies of a natural killer cell engager (NKCE). None of these investigations would be feasible in models lacking sufficient reconstitution of human T lymphocytes, macrophages, and NK cells. In the cell therapy category, we evaluated CAR-T, CAR-NK, and TCR-T cells across multiple tumor types. We show that HIS mice enable de-risking of immunogenicity by revealing rapid clearance of allogeneic CAR-T cells that are insufficiently stealthy, yet would otherwise persist for days-to-weeks in immunodeficient mice. Through adoptive cell-transfer experiments, we further demonstrate that CAR-NK cells can be durably supported in HIS mice and exhibit potent antitumor activity, and that iterative optimization of TCR-T constructs can fully suppress growth of an aggressive tumor model. Across these studies, HIS mice reproduced clinical, cellular, and molecular features of immune-related adverse events (irAEs) and cytokine release syndrome (CRS), while concurrently enabling assessment of biodistribution, target engagement, long-term persistence, and therapeutic efficacy. In conclusion, HIS mice constitute a powerful platform for reducing false-positive and false-negative outcomes in the preclinical evaluation of novel therapeutics, thereby improving predictivity and supporting more informed clinical-trial decision-making. Citation Format: Audrey Wetzel, Emilie Bayon, Sebastien Tabruyn, Dan Georgess, . Preclinical assessment of cell, gene, and antibody therapies using humanized mice 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 6968.