Immune Checkpoint Inhibitor-Induced Liver Injury.

In recent years cancer treatment has been revolutionized by the development and wide application of checkpoint inhibitor (CPI) drugs, which are a form of immunotherapy. CPI treatment is associated with immune-related adverse events, off-target tissue destructive inflammatory complications, which may affect a range of organs, with liver inflammation (hepatitis) being one of the more commonly noted events. This is a novel form of drug-induced liver injury and a rapidly evolving field, as our understanding of both the basic immunopathology of CPI hepatitis (CPI-H) and optimal clinical management, races to catch up with the increasing application of this form of immunotherapy in clinical practice. In this review, we summarize current evidence and understanding of CPI-H, from fundamental immunology to practical patient management.

Activation and transcriptional profile of monocytes and CD8+ T cells are altered in checkpoint inhibitor-related hepatitis.

BACKGROUND & AIMS: Checkpoint inhibitor-related hepatitis (CPI-Hep) is an emerging clinical challenge. We aimed to gain insights into the immunopathology of CPI-Hep by comprehensively characterising myeloid and lymphoid subsets. METHODS: CPI-treated patients with or without related hepatitis (CPI-Hep; n = 22 and CPI-noHep; n = 7) were recruited. Phenotypic and transcriptional profiling of peripheral immune subsets was performed and compared with 19 healthy controls (HCs). In vitro monocyte-derived macrophages (MoMFs) were assessed for activation and cytokine production. CD163, CCR2, CD68, CD3, CD8 and granzyme B expression was assessed using immunohistochemistry/immunofluorescence (n = 4). RESULTS: A significant total monocyte depletion was observed in CPI-Hep compared with HCs (p = 0.04), along with a proportionate increase in the classical monocyte population (p = 0.0002) and significant upregulation of CCR2, CD163 and downregulation of CCR7. Soluble CD163 levels were significantly elevated in CPI-Hep compared with HCs (p <0.0001). In vitro MoMFs from CPI-Hep showed enhanced production of pro-inflammatory cytokines. CD8+ T cells demonstrated increased perforin, granzyme B, ICOS and HLA-DR expression in CPI-Hep. Transcriptional profiling indicated the presence of activated monocyte and enhanced effector CD8+ T cell populations in CPI-Hep. Immunohistochemistry demonstrated co-localisation of CD8+/granzyme B+ T cells with CD68+CCR2+/CD68+CD163+ macrophages in CPI-Hep liver tissue. CONCLUSIONS: CPI-Hep is associated with activation of peripheral monocytes and an enhanced cytotoxic, effector CD8+ T cell phenotype. These changes were reflected by liver inflammation composed of CD163+/CCR2+ macrophages and CD8+ T cells. LAY SUMMARY: Some patients who receive immunotherapy for cancer develop liver inflammation, which requires cessation of cancer treatment. Herein, we describe ways in which the white blood cells of patients who develop liver inflammation differ from those of patients who receive the same immunotherapy but do not experience liver-related side effects. Targeting some of the pathways we identify may help to prevent or manage this side effect and facilitate cancer treatment.

Therapeutic inhibition of monocyte recruitment prevents checkpoint inhibitor-induced hepatitis.

BACKGROUND: Checkpoint inhibitor-induced hepatitis (CPI-hepatitis) is an emerging problem with the widening use of CPIs in cancer immunotherapy. Here, we developed a mouse model to characterize the mechanism of CPI-hepatitis and to therapeutically target key pathways driving this pathology. METHODS: C57BL/6 wild-type (WT) mice were dosed with toll-like receptor (TLR)9 agonist (TLR9-L) for hepatic priming combined with anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) plus anti-programmed cell death 1 (PD-1) ("CPI") or phosphate buffered saline (PBS) control for up to 7 days. Flow cytometry, histology/immunofluorescence and messenger RNA sequencing were used to characterize liver myeloid/lymphoid subsets and inflammation. Hepatocyte damage was assessed by plasma alanine transaminase (ALT) and cytokeratin-18 (CK-18) measurements. In vivo investigations of CPI-hepatitis were carried out in Rag2-/- and Ccr2rfp/rfp transgenic mice, as well as following anti-CD4, anti-CD8 or cenicriviroc (CVC; CCR2/CCR5 antagonist) treatment. RESULTS: Co-administration of combination CPIs with TLR9-L induced liver pathology closely resembling human disease, with increased infiltration and clustering of granzyme B+perforin+CD8+ T cells and CCR2+ monocytes, 7 days post treatment. This was accompanied by apoptotic hepatocytes surrounding these clusters and elevated ALT and CK-18 plasma levels. Liver RNA sequencing identified key signaling pathways (JAK-STAT, NF-ΚB) and cytokine/chemokine networks (Ifnγ, Cxcl9, Ccl2/Ccr2) as drivers of CPI-hepatitis. Using this model, we show that CD8+ T cells mediate hepatocyte damage in experimental CPI-hepatitis. However, their liver recruitment, clustering, and cytotoxic activity is dependent on the presence of CCR2+ monocytes. The absence of hepatic monocyte recruitment in Ccr2rfp/rfp mice and CCR2 inhibition by CVC treatment in WT mice was able to prevent the development and reverse established experimental CPI-hepatitis. CONCLUSION: This newly established mouse model provides a platform for in vivo mechanistic studies of CPI-hepatitis. Using this model, we demonstrate the central role of liver infiltrating CCR2+ monocyte interaction with tissue-destructive CD8+ T cells in the pathogenesis of CPI-hepatitis and highlight CCR2 inhibition as a novel therapeutic target.

The Role of Myeloid Cells in Hepatotoxicity Related to Cancer Immunotherapy.

Drug-related hepatotoxicity is an emerging clinical challenge with the widening use of immunotherapeutic agents in the field of oncology. This is an important complication to consider as more immune oncological targets are being identified to show promising results in clinical trials. The application of these therapeutics may be complicated by the development of immune-related adverse events (irAEs), a serious limitation often requiring high-dose immunosuppression and discontinuation of cancer therapy. Hepatoxicity presents one of the most frequently encountered irAEs and a better understanding of the underlying mechanism is crucial for the development of alternative therapeutic interventions. As a novel drug side effect, the immunopathogenesis of the condition is not completely understood. In the liver, myeloid cells play a central role in the maintenance of homeostasis and promotion of inflammation. Recent research has identified myeloid cells to be associated with hepatic adverse events of various immune modulatory monoclonal antibodies. In this review article, we provide an overview of the role of myeloid cells in the immune pathogenesis during hepatoxicity related to cancer immunotherapies and highlight potential treatment options.