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Published on: January 22, 2019
Development of a 1:1-binding biparatopic anti-TNFR2 antagonist by reducing signaling activity through epitope
Hiroki Akiba1,2, Junso Fujita3,4,5, Tomoko Ise6
1Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan. hakiba@pharm.kyoto-u.ac.jp.
Abstract:
Conventional bivalent antibodies against cell surface receptors often initiate unwanted signal transduction by crosslinking two antigen molecules. Biparatopic antibodies (BpAbs) bind to two different epitopes on the same antigen, thus altering crosslinking ability. In this study, we develop BpAbs against tumor necrosis factor receptor 2 (TNFR2), which is an attractive immune checkpoint target. Using different pairs of antibody variable regions specific to topographically distinct TNFR2 epitopes, we successfully regulate the size of BpAb-TNFR2 immunocomplexes to result in controlled agonistic activities. Our series of results indicate that the relative positions of the two epitopes recognized by the BpAb are critical for controlling its signaling activity. One particular antagonist, Bp109-92, binds TNFR2 in a 1:1 manner without unwanted signal transduction, and its structural basis is determined using cryo-electron microscopy. This antagonist suppresses the proliferation of regulatory T cells expressing TNFR2. Therefore, the BpAb format would be useful in designing specific and distinct antibody functions.
Insights
Biparatopic antibodies (BpAbs) offer precise control over immune checkpoint target signaling by binding two epitopes on tumor necrosis factor receptor 2 (TNFR2). This approach enables the development of targeted therapies with distinct antibody functions.
Area of Science:
- Immunology
- Structural Biology
- Biochemistry
Background:
- Conventional antibodies can trigger unintended signaling by crosslinking cell surface receptors.
- Tumor necrosis factor receptor 2 (TNFR2) is a key target in immune checkpoint modulation.
- Biparatopic antibodies (BpAbs) offer an alternative binding strategy to modulate receptor activity.
Purpose of the Study:
- To develop BpAbs targeting TNFR2 for controlled immune modulation.
- To investigate the impact of epitope positioning on BpAb activity.
- To characterize a novel TNFR2 antagonist BpAb.
Main Methods:
- Engineering of BpAbs with variable regions targeting distinct TNFR2 epitopes.
- Analysis of immunocomplex size and its correlation with signaling.
- Cryo-electron microscopy for structural determination of BpAb-TNFR2 interactions.
- Assessment of BpAb antagonist activity on regulatory T cell proliferation.
Main Results:
- BpAbs successfully regulated agonistic activities by controlling immunocomplex size.
- The relative positions of targeted epitopes critically influenced BpAb signaling.
- A specific antagonist BpAb (Bp109-92) demonstrated 1:1 binding to TNFR2 without inducing signal transduction.
- Bp109-92 effectively suppressed TNFR2-expressing regulatory T cell proliferation.
Conclusions:
- The BpAb format allows for fine-tuning of antibody functions against TNFR2.
- Epitope selection and relative positioning are crucial for designing specific BpAb therapeutics.
- BpAbs represent a promising platform for developing targeted immunotherapies with distinct functional outcomes.
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