CAR T-cell

What is CAR-T?

CAR-T (chimeric antigen receptor T-cell) therapy is a cellular therapy designed to genetically modify T cells, either from the patient or a donor, so they can recognize and attack cancer cells.Introducing an artificial receptor (CAR), which combines an antigen-binding site (such as scFv) and co-stimulatory domains such as CD3ζ and 4-1BB/CD28, into T cellsis characterized by. Starting with its demonstration of groundbreaking clinical efficacy in hematological malignancies, the development area is expanding to BCMA-targeted CAR-T and allogeneic "off-the-shelf" CAR-T therapies. Furthermore, drug discovery research aimed at expanding indications to solid tumors through next-generation designs such as ARMOR and logic-gated CARs is currently underway.

Representative examples of CAR-T

Tisagenlecleucel (Kymriah)

Tisagenlecleucel (Kymriah) is the world's first approved CAR-T product,targeting CD19 on the surface of B cells to attack cancer cellsAs a second-generation CAR, it is equipped with a 4-1BB co-stimulatory domain and CD3ζ in addition to the antigen-binding site. Designed to promote T-cell in vivo persistence and the maintenance of a memory T-cell phenotype through 4-1BB, it is used for ALL and DLBCL.

Axicabtagene Ciloleucel (Yescarta)

Axicabutagen Shiroru-Yuseru (Yescarta) is a second-generation CAR-T cell therapy that targets CD19 on the surface of B cells. It is equipped with a CD28 costimulatory domain, andRapid and Potent T-Cell Activation and an Explosive Proliferation Responseis characterized by causing. On the other hand, while proliferation and activation are faster compared to the 4-1BB type, there are differences in the risk of CRS (cytokine release syndrome) and the persistence in vivo.

Ciltacabtagene Autoleucel (Carvykti)

Silta Kabutagen Auto-Ucell (Carvykti) is a BCMA-targeted CAR-T cell therapy for relapsed or refractory multiple myeloma.A unique CAR design featuring two BCMA-binding domains (VHH single-domain antibodies)As a result, it exhibits high target-binding affinity and potent antitumor effects. It is considered a prime example of a highly functional CAR.

Key challenges in CAR-T development

On-target, Off-tumor Toxicity and the Difficulty in Predicting Fatal Cytokine Release Syndrome (CRS)/ICANS

If the target antigen is also expressed in normal tissue, “on-target, off-tumor” toxicity—in which CAR-T cells attack normal cells—may lead to severe organ damage. Furthermore,CRS and ICANS caused by monocyte/macrophage activation associated with the rapid proliferation of CAR-T cells are difficult to reproduce or predict using conventional toxicity tests.Therefore, risk assessment at the non-clinical stage becomes a major challenge.

Immunosuppression in the Tumor Microenvironment (TME) of Solid Tumors and CAR-T Cell Exhaustion

In solid tumors, in addition to the difficulty CAR-T cells have in infiltrating tumor tissue, factors such as TGF-β, PD-L1, Tregs, and MDSCs create an immunosuppressive tumor microenvironment (TME). In such an environment,CAR-T cells easily and rapidly fall into exhaustion...Immune evasion and treatment resistance resulting from antigenic heterogeneity and antigen shedding also pose challenges.

Complexity of In Vivo Proliferation, Distribution, and Engraftment (Cellular Kinetics / Persistence) as a Living Drug

CAR-T is a "living drug" and cannot be explained by simple clearance like conventional drugs. It exhibits complex kinetics, such as explosive proliferation upon antigen stimulation, reduction with target disappearance, and long-term engraftment (persistence) of memory T cells.Differences in T cell fractions based on patient background and product characteristics affect pharmacokinetics.This makes it difficult to extrapolate findings from animal models to humans.

Nonclinical Evaluations Required for CAR-T Therapy

Rating 1: Advanced "Humanized Mouse / Syngeneic Disease Models" that Replicate the Human Immune System and TME

In standard immunodeficient mice, it is not possible to adequately replicate the interactions between CAR-T cells and immune cells or the immunosuppressive TME.Evaluation of tumor accumulation/infiltration capacity and CRS/neurotoxicity risk using humanized mice reconstituted with human PBMCs/CD34+ hematopoietic stem cells, or organoid/tumor spheroid co-culture systemsWe will do so. In addition, we will monitor blood levels of IL-6, IFN-γ, TNF-α, and other markers over time to verify efficacy and safety margins.

Evaluation 2: “Cross-Reactivity Assessment Using Normal Tissue Panels and 3D Tissue Models” to Early Avoid On-Target, Off-Tumor Toxicity

To identify on-target, off-tumor toxicity prior to clinical trials, we evaluate the cross-reactivity of CAR-T cells with normal human tissues.High-sensitivity detection of toxicity in normal tissues using 3D organoids and iPS cell-derived cardiomyocytes, neural cells, and hepatocytes.We will do this. Furthermore, we will adjust the affinity of the CAR to search for a safe threshold that recognizes only tumors.

Evaluation 3: "Single-Cell Multi-Omics & Cellular Kinetics Analysis" to track CAR-T phenotype, exhaustion, and in vivo kinetics

To evaluate the sustained therapeutic efficacy of CAR-T cells, it is important to understand their post-administration phenotype and in vivo kinetics at the single-cell level.Analyze changes in Tscm, Tcm, Tem, and Teff, as well as depletion markers such as PD-1 and TIM-3, using scRNA-seq and multicolor flow cytometryand quantify the CAR gene copy number by ddPCR. This enables the integrated evaluation of proliferation, engraftment, and functional status.

Evaluation 4: “GvHD and Off-Target Genetic Modification Assessment” to Identify Safety and Immunogenicity Risks of Next-Generation CAR-T (ARMOR/Allogeneic)

In next-generation CAR-T therapy, GvHD caused by allogeneic T cells and off-target cuts associated with genome editing techniques such as CRISPR-Cas9 are major safety concerns.Evaluating allogeneic reactivity and off-target effects using the Mixed Lymphocyte Assay (MLR) and GUIDE-seq/CIRCLE-seqWe will use karyotyping and long-read sequencing to identify genomic abnormalities and assess cancer risk. Furthermore, we will integrate these findings with a GvHD model to verify clinical safety.

Key points when choosing a contract research organization (CRO) for non-clinical studies

CAR-T is a “living drug,” and unlike conventional small-molecule and antibody therapeutics, its efficacy and safety cannot be fully assessed through pharmacokinetic (PK) evaluation alone. A CRO capable of conducting comprehensive evaluations—ranging from PK and cellular kinetics to efficacy, disease, and resistance models—is a critical partner in supporting the complex development of CAR-T therapies.