Expanding the potential of CAR-based therapies: the need for predictive humanized models in preclinical studies

Chimeric antigen receptor (CAR)-engineered cell therapies have transformed the treatment landscape for hematological malignancies and are rapidly expanding into solid oncology, autoimmunity, and inflammatory diseases. The remarkable clinical success of CD19- and BCMA-targeted CAR-T cells has demonstrated the power of redirecting immune effector cells against disease-driving targets, leading to durable remissions in patients with otherwise refractory disease (Brudno and Kochenderfer, 2024; Alsaieedi and Zaher, 2025). Beyond conventional CAR-T cells, next-generation approaches now include CAR-natural killer (CAR-NK) cells, CAR-macrophages (CAR-M), CAR-regulatory T cells (CAR-Tregs), and engineered dendritic cell-targeting strategies, broadening the therapeutic scope of cellular immunotherapy (Abd El-Fattah et al., 2026).

Key challenges in the development of CAR-based therapies

Despite these advances, significant challenges continue to limit the development and translation of CAR-based therapies. One of the foremost obstacles is the complexity of the disease microenvironment, which can suppress effector cell function, promote exhaustion, and limit persistence after administration (Alsaieedi and Zaher, 2025). Antigen heterogeneity and antigen loss can lead to treatment resistance and relapse, particularly in solid tumors where target expression is often variable. Manufacturing challenges, high costs, variability between patient-derived products, and difficulties in generating consistent autologous cell products further complicate clinical implementation (Li et al., 2026; Alsaieedi and Zaher, 2025).

Safety remains another major concern. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are among the most common and clinically significant toxicities associated with CAR therapies (Brudno and Kochenderfer, 2024). These adverse events result from complex interactions between therapeutic cells and the host immune system, highlighting the need for preclinical models capable of reproducing human immune responses and predicting toxicity before clinical testing.

The need for predictive preclinical models

As CAR therapies become increasingly sophisticated and are extended beyond oncology into autoimmune and inflammatory disorders, robust preclinical testing platforms are essential. However, currently available mouse models exhibit important limitations. Conventional xenograft models in highly immunodeficient mice enable assessment of antitumor activity but fail to reproduce the complexity of human immune responses. Similarly, peripheral blood mononuclear cell (PBMC)-humanized models often develop rapid xenogeneic graft-versus-host disease (GvHD), limiting study duration and impairing evaluation of long-term efficacy and safety (Firoz et al., 2026). Many traditional humanized mouse models also display incomplete myeloid cell development and inadequate representation of clinically relevant immune-cell interactions, all of which are critical determinants of CAR-cell function.

The genO-BRGSF-HIS humanized mouse model addresses several of these limitations and provides a more translationally relevant platform for evaluating next-generation cellular immunotherapies. Developed through engraftment of human hematopoietic stem cells into immunocompromised genO-BRGSF mice, the model supports long-term reconstitution of a functional human immune system comprising cells from both lymphoid and myeloid compartments. Key features include robust and sustained human immune-cell engraftment, multilineage hematopoiesis and innate immune responses, reduced incidence of premature GvHD compared with PBMC-based models, and the ability to perform longitudinal efficacy, mechanism-of-action, and safety studies. The model also allows evaluation of therapies in the context of complex human immune-cell interactions that are not adequately represented in most conventional immunodeficient strains.

Importantly, recent studies have demonstrated the utility of genO-BRGSF-HIS mice for evaluating CAR-T therapies using autologous immune cells. Because CAR products are generated from the same donor used for humanization, investigators can assess therapeutic activity in an autologous setting that more closely mimics the clinical situation. This approach enables evaluation of CAR-cell expansion, persistence, trafficking, efficacy, and safety while reducing confounding alloreactive responses that frequently occur in xenogeneic systems. Such capabilities are particularly valuable for the development of novel CAR designs and alternative effector-cell platforms beyond conventional T cells.

The versatility of the model extends beyond oncology. In a recent publication, our collaborators from Université Marie et Louis Pasteur reported the investigation of the development of autologous CAR T therapies for immune-mediated inflammatory diseases (Caël et al., 2026). Since murine pDCs do not express CD123, a marker of plasmacytoid dendritic cells (pDCs) which are a key pathogenic population in several immune-mediated inflammatory diseases, the authors used the genO-BRGSF-HIS mouse model containing a human immune system. They isolated human T cells from genO-BRGSF-HIS mice that had been reconstituted with human CD34⁺ hematopoietic stem cells (HSCs) from different donors and used them to generate CD123-targeting CAR-T cells. Using genO-BRGSF-HIS mice supplemented with human Flt3 ligand and subjected to an imiquimod-induced inflammatory challenge, the investigators then showed efficient depletion of pDCs and modulation of disease-associated immune responses.

These results establish the genO-BRGSF-HIS mouse model as a powerful platform for evaluating next-generation CAR therapies beyond oncology, particularly through the engineering of autologous T cells. By supporting human dendritic-cell development, enabling disease-relevant inflammatory challenges, and allowing functional assessment of immune-cell targeting in vivo, the model provides unique opportunities to investigate novel CAR applications in autoimmune and inflammatory disorders. The study by Caël et al. therefore not only validates CD123-targeted CAR-T therapy as a strategy for pDC depletion but also illustrates how advanced humanized mouse models can accelerate the translation of innovative cellular immunotherapies into other therapeutic areas.

Assessing CAR-induced Cytokine Release Syndrome (CRS) in preclinical models

Cytokine release syndrome remains a major dose-limiting complication of cellular immunotherapy, driven largely by interactions between CAR-engineered cells and myeloid populations (Brudno and Kochenderfer, 2024). Humanized mouse systems enriched for functional myeloid compartments have emerged as valuable platforms for reproducing CRS-like manifestations. Martin et al. (2024) demonstrated that the genO-BRGSF-HIS mouse model can recapitulate key features associated with CRS, supporting its use for safety assessment and mechanistic studies. The presence of a more complete human immune system in the genO-BRGSF-HIS model therefore creates opportunities to evaluate both efficacy and toxicity within the same experimental platform, which could be applied to the safety evaluation of CAR therapies. Furthermore, although a more extensive safety evaluation is needed, preliminary results from the use of CD123-targeted CAR T cells in the genO-BRGSF-HIS mouse model with imiquimod-induced psoriasis demonstrated a cytokine release peak upon CAR T treatment (Caël et al., 2026). These results suggest that this model could be useful for analyzing the safety profile of new CAR-T cell treatments.

Taken together, the continued evolution of CAR-based therapies demands preclinical models capable of faithfully reproducing human immune biology. While conventional xenograft systems remain useful for proof-of-concept studies, they are often insufficient for evaluating the complex efficacy and safety profiles of modern cellular immunotherapies. By providing durable human immune reconstitution, support for autologous CAR-cell testing, and the potential to study CRS-related mechanisms, the genO-BRGSF-HIS model represents a valuable translational bridge between in vitro discovery and clinical development. Find out more about the applications and advantages of this model here.

‍

‍

参考文献

• Abd El-Fattah EE, Hamdy R, Soliman SSM, Husseiny MI. 2026. The evolution of CAR therapies across oncology and autoimmunity: mechanistic insights and therapeutic innovations. International Immunopharmacology. doi:10.1016/j.intimp.2026.116867
• Alsaieedi AA, Zaher KA. 2025. Tracing the development of CAR-T cell design: from concept to next-generation platforms. Frontiers in Immunology. doi: 10.3389/fimmu.2025.1615212
• Brudno JN, Kochenderfer JN. 2024. Current understanding and management of CAR T cell-associated toxicities. Nature Reviews Clinical Oncology. doi:10.1038/s41571-024-00903-0
• Caël B, Bôle-Richard E, Belakri I, et al. 2026. Functional evaluation of CAR-T anti-CD123 from immune-mediated inflammatory diseases patients for novel pDC-targeted immunotherapy. Journal of Allergy and Clinical Immunology. doi:10.1016/j.jaci.2026.08.031
• Firoz WA, Sheng MK, Vick LV, et al. 2026. Chronic xenogeneic GVHD after CAR T cell therapy limits long-term safety assessment of CAR effects using NSG mouse model. Blood Advances. doi:10.1182/bloodadvances.2025019559
• Li C, Liu H, Liao S, et al. 2026. The Evolving Landscape of CAR T-Cell Therapy in Autoimmune Diseases: A State-of-the-Art Review. Clinical Reviews in Allergy & Immunology. doi:10.1007/s12016-026-09151-9
• Martin GH, Gonon A, Martin-Jeantet P, et al. 2024. Myeloid and dendritic cells enhance therapeutics-induced cytokine release syndrome features in humanized BRGSF-HIS preclinical model. Front Immunol. 2024;15:1357716. doi:10.3389/fimmu.2024.1357716