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Tracking Bispecific Antibody-Induced T Cell Trafficking Using Luciferase-Transduced Human T Cells
Published on: May 12, 2023
Binding domain on CD22 molecules contributing to the biological activity of T cell-engaging bispecific antibodies
Jie Chen1, Zhidi Pan1, Lei Han2
1Engineering Research Center of Cell and Therapeutic Antibody, Ministry of Education, School of Pharmacy, Shanghai Jiao Tong University, Shanghai, 200240, China.
Abstract:
CD22, as the B-cell malignancies antigen, has been targeted for immunotherapies through CAR-T cells, antibody-drug conjugates (ADCs) and immunotoxins via interaction of antibodies with binding domains on the receptor. We hypothesized that avidity and binding domain of antibody to target cells may have significant impact on the biological function in tumor immunotherapy, and T cell-engaging bispecific antibody (TCB) targeting CD22 could be used in the therapy of hematologic malignancies. So, to address the question, we utilized the information of six previously reported CD22 mAbs to generate CD22-TCBs with different avidity to different domains on CD22 protein. We found that the avidity of CD22-TCBs to protein was not consistent with the avidity to target cells, indicating that TCBs had different binding mode to the protein and cells. In vitro results indicated that CD22-TCBs mediated cytotoxicity depended on the avidity of antibodies to target cells rather than to protein. Moreover, distal binding domain of the antigen contributed to the avidity and biological activity of IgG-[L]-scfv-like CD22-TCBs. The T cells' proliferation, activation, cytotoxicity as well as cytokine release were compared, and G5/44 BsAb was selected for further in vivo assessment in anti-tumor activity. In vivo results demonstrated that CD22-TCB (G5/44 BsAb) significantly inhibited the tumors growth in mice. All these data suggested that CD22-TCBs could be developed as a promising candidate for B-cell malignancies therapy through optimizing the design with avidity and binding domain to CD22 target in consideration.
Insights
Optimizing T cell-engaging bispecific antibodies (TCBs) targeting CD22 by considering antibody avidity and binding domain significantly enhances their efficacy in treating B-cell malignancies. This approach improves anti-tumor activity, offering a promising therapeutic strategy.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- CD22 is a key antigen in B-cell malignancies, making it a target for immunotherapies like CAR-T cells, ADCs, and immunotoxins.
- The avidity and binding domain of antibodies targeting CD22 are hypothesized to significantly impact immunotherapy effectiveness.
- T cell-engaging bispecific antibodies (TCBs) offer a potential therapeutic approach for hematologic malignancies by engaging T cells to target cancer cells.
Purpose of the Study:
- To investigate the impact of antibody avidity and binding domain on the biological function of CD22-targeting TCBs in cancer immunotherapy.
- To generate and evaluate CD22-TCBs with varying avidities and binding specificities to assess their therapeutic potential.
- To determine the optimal design parameters for CD22-TCBs to maximize anti-tumor activity in B-cell malignancies.
Main Methods:
- Generated CD22-TCBs using six previously reported CD22 monoclonal antibodies (mAbs), varying avidity and targeting different domains of the CD22 protein.
- Assessed the avidity of CD22-TCBs to both the CD22 protein and target cells, comparing protein-binding avidity with cell-binding avidity.
- Evaluated TCB-mediated cytotoxicity, T cell proliferation, activation, cytotoxicity, and cytokine release *in vitro*. Selected lead candidate (G5/44 BsAb) for *in vivo* studies.
- Assessed the anti-tumor activity of the selected CD22-TCB (G5/44 BsAb) *in vivo* in a mouse model.
Main Results:
- Avidity of CD22-TCBs to the CD22 protein did not consistently correlate with avidity to target cells, suggesting different binding modes.
- TCB-mediated cytotoxicity *in vitro* was dependent on the avidity of antibodies to target cells, not to the protein.
- The distal binding domain of CD22 was found to contribute to the avidity and biological activity of IgG-[L]-scfv-like CD22-TCBs.
- CD22-TCB (G5/44 BsAb) demonstrated significant inhibition of tumor growth *in vivo*.
Conclusions:
- The avidity and binding domain of antibodies are critical factors in the design of effective CD22-targeting TCBs for B-cell malignancies.
- Optimizing CD22-TCB design by considering target cell avidity and distal binding domain interactions can enhance therapeutic efficacy.
- CD22-TCBs, particularly G5/44 BsAb, represent a promising therapeutic strategy for hematologic malignancies, warranting further clinical development.
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