Overview of scFv-CH-CL-scFv

What is scFv-CH-CL-scFv

scFv-CH-CL-scFv is a recombinant antibody composed of two single-chain antibodies (scFv) connected by a flexible linker peptide, each scFv contains a variable light chain (VL) and a variable heavy chain (VH) that can bind to antigen. scFv-CH-CL-scFv is a product of a novel antibody engineering technology that overcomes some limitations of traditional monoclonal antibodies (mAb) and single-chain antibodies (scFv), such as smaller molecular weight, better tissue penetration ability, faster blood clearance rate, lower immunogenicity, etc. scFv-CH-CL-scFv is mainly used for cancer immunotherapy, by constructing chimeric antigen receptor (CAR) to redirect T cells, enabling them to recognize and kill tumor cells.

Fig.1 Antibody model showing subunit composition and domain distribution along the polypeptide chains. (Ahmad ZA, 2012)

scFv-CH-CL-scFv has a broad application prospect in cancer immunotherapy, especially in the construction of chimeric antigen receptor (CAR). CAR is an artificially synthesized protein consisting of an exogenous antigen recognition structure (usually an scFv or scFv-CH-CL-scFv), a transmembrane structure and an endogenous signal transduction structure. CAR can be transduced to T cells, enabling them to directly recognize and kill tumor cells expressing specific antigens without the mediation of major histocompatibility complex (MHC). Currently, several CAR-T cell therapy products based on CD19-specific scFv or scFv-CH-CL-scFv have been approved by the US Food and Drug Administration (FDA) for the treatment of relapsed or refractory B-cell malignancies. In addition, there are many CAR-T cell therapy products based on other targets of scFv or scFv-CH-CL-scFv in different stages of clinical trials, showing good safety and efficacy.

Structural Features of scFv-CH-CL-scFv

The structure of scFv-CH-CL-scFv consists of two scFvs linked by a flexible peptide linker, each scFv contains a VL and a VH domain composed of a V and a J region. The linker length, sequence and solubility affect the stability, folding and aggregation tendency of scFv-CH-CL-scFv. The linker also keeps the VL and VH domains at an appropriate distance to facilitate proper folding and antigen-binding site formation, while preventing excessive oligomerization of scFv-CH-CL-scFv. The relative position of VL and VH domains is another factor that influences the structure of scFv-CH-CL-scFv. There are two possible configurations: VL-linker-VH or VH-linker-VL. Both configurations can generate functional scFv-CH-CL-scFv, but different scFvs may perform better in different configurations. Therefore, the effect of VL and VH domain orientation on the structure and function of scFv-CH-CL-scFv should be considered in the design process.

Generation Methods of scFv-CH-CL-scFv

The generation methods of scFv-CH-CL-scFv mainly include genetic engineering and in vitro display. Genetic engineering involves connecting two scFv genes with a linker sequence and expressing them in bacteria, using known or available scFv genes against a specific antigen. In vitro display involves screening and linking scFvs with high affinity and specificity from a large scFv library containing diverse variable region combinations, using display vectors such as phage or yeast.

Clinical Data of scFv-CH-CL-scFv

The clinical application of scFv-CH-CL-scFv is mainly reflected in the construction of chimeric antigen receptor (CAR), and currently there are several CAR-T cell therapy products based on scFv-CH-CL-scFv that have been approved by the US Food and Drug Administration (FDA) for the treatment of relapsed or refractory B-cell malignancies. In addition, there are many CAR-T cell therapy products based on scFv-CH-CL-scFv in different stages of clinical trials, targeting different tumor antigens, showing good safety and efficacy.

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