About Bispecific Antibodies

Redirecting T cells to restore an immune response

Tumors can employ mechanisms that alter the immune response in their microenvironment.1 One approach to countering these immuno-evasive mechanisms is to redirect and expand populations of T cells.2,3 T cells can be physically recruited and linked to tumor surface antigens to elicit an antitumor immune response in patients with cancer.4 Bispecific antibodies are designed to simultaneously bind to T cells and tumor cell antigens, leading to T-cell activation, proliferation, and tumor cell death.4

Simultaneously binding to T cells and tumor cells

Bispecific antibodies targeting a variety of tumor types have become an important component of Genentech's investigational cancer immunotherapy research. In contrast to early-generation therapeutic antibodies, bispecific antibodies combine the binding specificity of two antibodies in one molecule.5 They are engineered to have two or more distinct Fab regions (antigen-binding sites) with a common Fc region. This structure allows simultaneous binding to CD3 on T cells and target antigens on tumor cells, which brings the T cells into close proximity with the target tumor cells, leading to T-cell–mediated killing of the tumor cells.3,4

Bispecific antibody structure

CEA=carcinoembryonic antigen; Fab=fragment of antigen binding; Fc=fragment, crystallizable.

Variety of molecular structures for robust T-cell anticancer strategies

We are exploring the potential of innovative bispecific antibody structures that activate T cells to induce an antitumor immune response across multiple tumor types.5,6

Simultaneous binding of a T-cell bispecific antibody to CD3 on T cells and a tumor cell surface antigen, such as CEA or CD20, may result in the formation of an immune synapse, a junction formation between the T cell and tumor cell, and subsequent downstream signaling that may lead to T-cell–mediated tumor killing through:3,4

  • T-cell activation and secretion of cytotoxic granules
  • Secretion of cytokines/chemokines that generate a pro-inflammatory tumor microenvironment and recruit additional T cells
  • T-cell proliferation and expansion at the tumor site

We are exploring the potential of combining T-cell bispecific antibodies with other anticancer therapies, including PD-L1 inhibition and antibody drug conjugates in the pursuit of enhancing T-cell–mediated cancer immunity.

T-cell bispecific antibodies in action

Watch a time-lapse microscope video of the T-cell bispecific antibody in activating cytotoxic T lymphocytes designed to kill tumor cells. As demonstrated in preclinical models, upon dispersion of T-cell bispecific antibodies, the cytotoxic T cells (seen in red) immediately recognize and begin to destroy the target cancer cells (seen in blue). Green flashes in the tumor cells indicate imminent T-cell–induced cell death.8

This compound and its use continue to be investigated in ongoing studies; efficacy and safety have not been established.

References

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