Mechanism and Clinical Applications of CD19- and BCMA-Targeting TCEs

Gene Information:

• CD3: Encoded by CD3E, D, G; part of the Ig superfamily. It forms the essential signaling backbone of the T-cell receptor (TCR) complex. 
• CD19: is a transmembrane glycoprotein. It belongs to the immunoglobulin superfamily and plays a critical role in B-cell development, activation, and maintenance throughout the immune system.
• BCMA: Encoded by the TNFRSF17 gene, a critical member of the tumor necrosis factor receptor (TNFR) superfamily.

Protein Expression:

• CD3: Constitutive and universal marker for all mature T cells (CD4+, CD8+).  Always present on the cell surface. 
• CD19: is expressed almost exclusively on B-lineage cells, beginning at the early B-cell stage and persisting through mature B cells. Its expression is typically absent or markedly reduced in plasma cells. 
• BCMA:  It is a B-cell maturation antigen, whose expression is highly in mature plasma cells and nearly all multiple myeloma cells.

Key Advantages

• Accurate Modeling of Human Biology Expresses and Function：This effectively overcomes the significant species-specific differences inherent to traditional mouse models.
• An intact immune system：The model provides stable and repeatable data, making it ideal model for large-scale, high-throughput molecular screening.
• Enhanced R&D Efficiency：It enables effective preclinical evaluation of antibodies, thereby improving candidate screening accuracy, reducing failure costs, and shortening the R&D cycle.

Key Applications

• Efficacy Evaluation：To evaluate the efficacy of  T cell engagers co-activating CD3, CD19，and BCMA, disease models were established by engrafting gene-humanized cell lines.
• Safety and CRS Research：Provide a clinically relevant platform to study major risks associated with CD3-targeting therapies, such as Cytokine Release Syndrome (CRS).
• Novel Therapeutic Screening：Support the discovery, screening, and optimization of new treatment strategies,  leveraging a relevant humanized models  for translational research.

Mouse and human CD3E expression analysis in splenocytes. Splenocytes were collected from wild-type C57BL/6 mice and homozygous B-hCD3EDG/hCD19ad/hBCMA mice (male, 6-week-old, n = 3). CD3E  expression on T cells was analyzed by flow cytometry using species-specific anti-CD3E  antibodies (anti-human CD3E antibody, Biolegend, 317344; anti-mouse CD3E antibody, Biolegend, 100210).

Mouse and human CD19 expression analysis in splenocytes. Splenocytes were collected from wild-type C57BL/6 mice and homozygous B-hCD3EDG/hCD19ad/hBCMA mice (male, 6-week-old, n = 3). CD19 expression on B cells was analyzed by flow cytometry using species-specific anti-CD19 antibodies (anti-human CD19 antibody, Biolegend, 302234; anti-mouse CD19 antibody, Biolegend, 115507).

Human BCMA expression analysis in splenocytes. Spleen cells were collected from wild-type C57BL/6 mice  (male, 6-week-old)  and homozygous B-hCD3EDG/hCD19 ad/hBCMA mice (male, 6-week-old).  Human BCMA expression on plasma cells was analyzed by flow cytometry using anti-human BCMA antibody (Biolegend, 357504). Mice were stimulated with LPS and treated with γ-secretase inhibitor to enhance membrane BCMA expression.

In vivo B-cell depletion by anti-human CD3/BCMA or anti-human CD3/CD19 bispecific antibodies (BsAbs) in B-hCD3EDG/hCD19 ad/hBCMA mice. Bispecific antibodies (Teclistamab: targeting BCMA/CD3; Surovatamig: targeting CD19/CD3) or PBS control were administered as a single dose to B-hCD3EDG/hCD19 ad/hBCMA mice (n=3 per group). Blood cells were harvested on day 1 and day 7 post-treatment. The frequency and absolute numbers of mCD45⁺ cells, B cells, and T cells were quantified by flow cytometry. Data was shown as Mean ± SEM, and analyzed using One way ANOVA followed Dunnett's multiple comparisons test compared with G1(Control group). (*p<0.05, ***p<0.001, ****p<0.0001)

In vivo depletion of B cells and plasma cells by anti-CD19/CD3 and anti-BCMA/CD3 bispecific antibodies (BsAbs) in B-hCD3EDG/hCD19 ad/hBCMA mice. Bispecific antibodies (Teclistamab: targeting BCMA/CD3; Surovatamig: targeting CD19/CD3) or PBS control were administered as a single dose to B-hCD3EDG/hCD19 ad/hBCMA mice (n=3 per group). Spleen cells were harvested on day 7 post-treatment. The frequency and absolute numbers of mCD45⁺ cells, B cells, T cells, plasma cells, and plasmablasts were quantified by flow cytometry. Data was shown as Mean ± SEM, and analyzed using One way ANOVA followed Dunnett's multiple comparisons test compared with G1 (Control group). (*p<0.05, ***p<0.001, ****p<0.0001)

In vivo depletion of B cells and plasma cells by anti-CD19/CD3 and anti-BCMA/CD3 bispecific antibodies (BsAbs) in B-hCD3EDG/hCD19 ad/hBCMA mice. Bispecific antibodies (Teclistamab: targeting BCMA/CD3; Surovatamig: targeting CD19/CD3) or PBS control were administered as a single dose to B-hCD3EDG/hCD19 ad/hBCMA mice (n=3 per group). Bone marrow were harvested on day 7 post-treatment. The frequency and absolute numbers of mCD45⁺ cells, B cells, T cells, plasma cells, and plasmablasts were quantified by flow cytometry. Data was shown as Mean ± SEM, and analyzed using One way ANOVA followed Dunnett's multiple comparisons test compared with G1 (Control group). (*p<0.05, ***p<0.001, ****p<0.0001)