FMC63 scFv: The Core Component of CD19-Targeted CAR-T Therapy and the Application Advances in Its Detection Tools

I. CAR-T Therapy and CD19 Target

Chimeric antigen receptor T-cell (CAR-T) therapy represents a major breakthrough in tumor immunotherapy, with CD19-targeted CAR-T products demonstrating remarkable efficacy in treating B-cell malignancies. CD19, a protein widely expressed on the surface of normal B cells and most B-lineage malignant cells, has become an ideal target for CAR-T therapy.

II. Structural and Functional Characteristics of FMC63 scFv

The FMC63 single-chain variable fragment is derived from the murine monoclonal antibody FMC63, consisting of its heavy and light chain variable regions connected by a flexible linker peptide. This structure retains full antigen-binding capability while offering the following advantages:

High affinity: Nanomolar-level binding affinity (KD value) for CD19

Strong specificity: Exclusive recognition of the CD19 extracellular domain

Excellent stability: Binding epitope is minimally affected by protein conformational changes

Optimal spatial accessibility: Facilitates effective binding between CAR molecules and cell surface CD19

These characteristics have established FMC63 scFv as the "gold standard" component for CD19-CAR construction, widely used in approved CAR-T products such as Kymriah and Yescarta.

III. Applications of FMC63 Antibody in CAR-T Development

1. CAR Expression Detection
During CAR-T cell preparation, FMC63-specific antibodies enable direct detection of CAR surface expression on T cells via flow cytometry. For example:
Staining FMC63-CAR transfected 293T cells with FMC63 antibody shows significant fluorescence signal shift
PE-labeled FMC63 antibody clearly distinguishes CAR-positive and negative cell populations

2. Functional Evaluation
FMC63 antibodies are also used for:
CAR molecule binding activity analysis
Internalization kinetics studies
Cell activation status assessment

3. Quality Control Applications
In CAR-T product quality control, FMC63 antibodies can be used for:
Quantification of CAR expression rate
Batch-to-batch consistency evaluation
Stability monitoring

IV. Extended Applications of FMC63 scFv

1. Bispecific Antibody Development
FMC63 scFv can serve as a functional module in CD19-targeting bispecific T-cell engagers (BiTEs).

2. Other Cell Therapies
The FMC63-CAR structure is equally applicable to immune effector cells such as natural killer cells and macrophages.

3. Diagnostics and Imaging
FMC63-based antibody probes can be used to develop:
Companion diagnostic reagents
In vivo imaging probes

V. Technological Advances and Prospects

With advancements in cell therapy technology, FMC63 scFv continues to play a vital role in next-generation immunotherapy strategies. It remains a core recognition element in novel treatment approaches such as universal CAR-T and controllable CAR-T systems. Meanwhile, high-quality detection antibodies targeting FMC63 will demonstrate increasing value in treatment monitoring and efficacy assessment.

VI. Starter FMC63 Antibody Products

Starter Biotechnology provides recombinant rabbit monoclonal antibodies against FMC63 with the following features:

High specificity for CAR structures containing FMC63 scFv

Available in both purified antibody and PE-labeled formats

Validated by flow cytometry with excellent signal-to-noise ratio

Suitable for multiple stages of CAR-T development and quality control

Product Details: