Research ArticleCancer

CD3 bispecific antibody–induced cytokine release is dispensable for cytotoxic T cell activity

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Science Translational Medicine  04 Sep 2019:
Vol. 11, Issue 508, eaax8861
DOI: 10.1126/scitranslmed.aax8861

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Taming the cytokine beast

Bispecific antibodies, which are engineered to engage a cancer cell antigen and activate T cells to kill the cancer cell, are showing clinical promise. Unfortunately, they can also cause major side effects as a result of uncontrolled immune activation and cytokine release. Li et al. found a way to separate the beneficial effects from the harmful ones by showing that activation of tumor necrosis factor–α signaling is necessary for the toxic systemic cytokine release but not for successful cancer treatment. The authors identified several ways to inhibit the dangerous signaling pathway and demonstrated them in mouse models, with no loss of anticancer efficacy.


T cell–retargeting therapies have transformed the therapeutic landscape of oncology. Regardless of the modality, T cell activating therapies are commonly accompanied by systemic cytokine release, which can progress to deadly cytokine release syndrome (CRS). Because of incomplete mechanistic understanding of the relationship between T cell activation and systemic cytokine release, optimal toxicity management that retains full therapeutic potential remains unclear. Here, we report the cell type–specific cellular mechanisms that link CD3 bispecific antibody–mediated killing to toxic cytokine release. The immunologic cascade is initiated by T cell triggering, whereas monocytes and macrophages are the primary source of systemic toxic cytokine release. We demonstrate that T cell–generated tumor necrosis factor–α (TNF-α) is the primary mechanism mediating monocyte activation and systemic cytokine release after CD3 bispecific treatment. Prevention of TNF-α release is sufficient to impair systemic release of monocyte cytokines without affecting antitumor efficacy. Systemic cytokine release is only observed upon initial exposure to CD3 bispecific antibody not subsequent doses, indicating a biological distinction between doses. Despite impaired cytokine release after second exposure, T cell cytotoxicity remained unaffected, demonstrating that cytolytic activity of T cells can be achieved in the absence of cytokine release. The mechanistic uncoupling of toxic cytokines and T cell cytolytic activity in the context of CD3 bispecifics provides a biological rationale to clinically explore preventative treatment approaches to mitigate toxicity.

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