Dissecting the Mechanisms Underlying the Cytokine Release Syndrome (CRS) Mediated by T-Cell Bispecific Antibodies

Purpose: Target-dependent TCB activity can result in the strong and systemic release of cytokines that may develop into cytokine release syndrome (CRS), highlighting the need to understand and prevent this complex clinical syndrome.Experimental Design: We explored the cellular and molecular players involved in TCB-mediated cytokine release by single-cell RNA-sequencing of whole blood treated with CD20-TCB together with bulk RNA-sequencing of endothelial cells exposed to TCB-induced cytokine release. We used the in vitro whole blood assay and an in vivo DLBCL model in immunocompetent humanized mice to assess the effects of dexamethasone, anti-TNF alpha, anti-IL6R, anti-IL1R, and inflammasome inhibition, on TCB-mediated cytokine release and antitumor activity.Results: Activated T cells release TNF alpha, IFN gamma, IL2, IL8, and MIP-1 beta, which rapidly activate monocytes, neutrophils, DCs, and NKs along with surrounding T cells to amplify the cascade further, leading to TNF alpha, IL8, IL6, IL1 beta, MCP-1, MIP-1 alpha, MIP-1 beta, and IP-10 release. Endothelial cells contribute to IL6 and IL1 beta release and at the same time release several chemokines (MCP-1, IP-10, MIP-1 alpha, and MIP-1 beta). Dexamethasone and TNF alpha blockade efficiently reduced CD20-TCB-mediated cytokine release whereas IL6R blockade, inflammasome inhibition, and IL1R blockade induced a less pronounced effect. Dexamethasone, IL6R blockade, IL1R blockade, and the inflammasome inhibitor did not interfere with CD20-TCB activity, in contrast to TNF alpha blockade, which partially inhibited antitumor activity.Conclusions: Our work sheds new light on the cellular and molecular players involved in cytokine release driven by TCBs and provides a rationale for the prevention of CRS in patients treated with TCBs. See related commentary by Luri-Rey et al., p. 4320Conclusions: Our work sheds new light on the cellular and molecular players involved in cytokine release driven by TCBs and provides a rationale for the prevention of CRS in patients treated with TCBs. See related commentary by Luri-Rey et al., p. 4320