What is CAR T-cell therapy?

CAR T-cell therapy is a type of cellular immunotherapy which targets a patient’s own immune cells to use directly against their cancer cells. Unlike traditional drugs, CAR T-cells are a “living drug”, where a single infusion can produce deep and durable remissions.

CAR is mainly composed of a cell membrane extracellular antigen binding region and an intracellular signal transduction region through a hinge region and a transmembrane region. The extracellular antigen binding domain can specifically recognize and bind to a target cell surface antigen. It is derived from a single-chain variable region(scFv) of a monoclonal antibody. The intracellular signal transduction domain is mainly composed of a costimulatory signal and a CD3zetachain of T cell receptor (TCR). After CAR-T cells binding to the target cell antigen through the scFv, the intracellular signal transduction region transmits signals to the T cell, thereby activates T cell, which in turn results secretion of perforin, granzymes and interferons.

There are so far two FDA and EMA approved CAR T-cell therapies for adult patients with lymphoma, Yescarta and Kymriah. Both of them are directed against CD19-positive B-cell tumors, using the same antigen-binding region, the scFv derived from the mouse monoclonal antibody FMC63.

FMC63 is an IgG2a mouse monoclonal antibody specific for CD19, which is a target for the immunotherapy of B lineage leukaemias and lymphomas. FMC63 scFv is the most commonly used ectodomain component of CD19-specific CARs. So far, most of reported CART19 trials contain the anti-CD19 scFv derived from FMC63, including the two FDA and EMA-approved CARs Kymriah and Yescarta.

Detection of CAR-T cells

Generation of CAR-T cell requires transfection of the CAR gene intoT cell via a viral or non-viral system. When the CAR is expressed on the membrane of T cell, CAR T-cell then has the activity of recognizing and killing the target cells. Therefore, accurate detection of CAR-positive T cells is a key step in the quality control of CAR T-cell therapy, and an important criterial in clinical dose control, process monitoring and assistant diagnosis. There are two common types of detection methods: detection of CAR gene-positive T cells and detection of CAR protein-positive T cells.

CustoScan provides products accurately detecting CAR protein-positive T cells. One of these products is called "R19M”, which is a rabbit monoclonal antibody specifically binding to the scFv region of a mouse monoclonal antibody clone FMC63. R19M has high specificity and sensitivity. It enables a detection of 1 CD19 CAR T cell in 10,000 PBMCs from a patient sample in a flow cytometric assay (i.e. 0.01% of limit detection).

R19M has been used by our clients in CD19 CAR T-Cell product quality control and clinical sampling testing, including PK, ADA, Nab assays, and CITE-seq, successfully in many clinical settings.