Checkpoint Inhibitor Induced Colitis and Arthritis -Immunomodulation With IL-6 Blockade and Exploration of Disease Mechanisms

Overview

Immune checkpoint inhibitors (ICI) might induce inflammatory potentially serious and even lethal immune related Adverse Events (irAEs). Diarrhea and/or colitis are ones of the most frequently reported irAEs in patients taking ICI. Although the immune mechanisms underlying irAEs have not been fully elucidated, studies suggest that Th17 and Tregs cells, increases in expression of immunologically-related genes, eosinophilia, microbiome among others and cytokines may be involved in the pathophysiology of immune-related complications in some diseases that resemble irAEs, such as colitis and rheumatic manifestations. Importantly, interleukin-6 (IL-6) promotes the differentiation of naïve CD4+ T cells into Th17 cells (17), and IL-6 inhibition may rebalance the altered Th17-Treg axis without inhibiting the Th1-CD8+ T-cell subsets that govern antitumor immunity. These findings raise the possibility of using IL-6 blockade as a strategy for treating colitis and arthritis induced by immune checkpoint blockade.

Immune checkpoint inhibitors (ICI) targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and the programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) pathway might induce inflammatory potentially serious and even lethal immune related Adverse Events (irAEs). Diarrhea and/or colitis are ones of the most frequently reported irAEs in patients taking ICI, occurring after an average of three infusions. The incidence is higher among patients taking combination anti-CTLA-4/ anti-PD-1 therapy (44%) than those receiving anti-CTLA-4 (23-33%) or anti-PD-1 (≤19%) monotherapy. The most common autoimmune and musculoskeletal irAEs reported in clinical trials are represented by arthralgia and arthritis. The incidence of arthralgia and/or inflammatory arthritis secondary to nivolumab therapy ranges from 5% to 16% and 5%, respectively. Although the immune mechanisms underlying irAEs have not been fully elucidated, studies suggest that Th17 and Tregs cells, increases in expression of immunologically-related genes, eosinophilia, microbiome among others and cytokines may be involved in the pathophysiology of immune-related complications in some diseases that resemble irAEs, such as colitis and rheumatic manifestations. Previous studies report Th-17, that drives interleukin-17 (IL-17) production, as a key mediator of many immune diseases, including inflammatory bowel disease and ICI-induced colitis, and IL-17 elevations have been observed in experimental colitis. Importantly, interleukin-6 (IL-6) promotes the differentiation of naïve CD4+ T cells into Th17 cells (17), and IL-6 inhibition may rebalance the altered Th17-Treg axis without inhibiting the Th1-CD8+ T-cell subsets that govern antitumor immunity. An imbalance of Th17/Treg may cause the onset and progression of immune-mediated side effects. Thus, a 3-fold increase of IL-17 and IL-6 by week 12, concomitant with the development of fulminant colitis has been reported in a patient who developed presumed ipilimumab-induced colitis. These findings raise the possibility of using IL-6 blockade as a strategy for treating colitis and arthritis induced by immune checkpoint blockade.