IL-6 Blockade in Cytokine Storm Syndromes.

Interleukin-6 (IL-6) is a pro-inflammatory cytokine elevated in cytokine storm syndromes, including hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS). It is also elevated in cytokine release syndrome (CRS) after immune activating cancer therapies such as chimeric antigen receptor (CAR) T-cells or bispecific T-cell engagers (BITEs) and in some patients after infection with SARS-CoV-2. The interaction of IL-6 with its receptor complex can happen in several forms, making effectively blocking this cytokine's effects clinically challenging. Fortunately, effective clinical agents targeting the IL-6 receptor (tocilizumab) and IL-6 directly (siltuximab) have been developed and are approved for use in humans. IL-6 blockade has now been used to safely and effectively treat several cytokine storm syndromes (CSS). Other methods of investigation in effective IL-6 blockade are underway.