BackgroundIpilimumab, a cytotoxic T-lymphocyte antigen-4 (CTLA-4) blocking antibody, has been approved for the treatment of metastatic melanoma and induces adverse events (AE) in up to 64% of patients. Treatment algorithms for the management of common ipilimumab-induced AEs have lead to a reduction of morbidity, e.g. due to bowel perforations. However, the spectrum of less common AEs is expanding as ipilimumab is increasingly applied. Stringent recognition and management of AEs will reduce drug-induced morbidity and costs, and thus, positively impact the cost-benefit ratio of the drug. To facilitate timely identification and adequate management data on rare AEs were analyzed at 19 skin cancer centers.Methods and FindingsPatient files (n = 752) were screened for rare ipilimumab-associated AEs. A total of 120 AEs, some of which were life-threatening or even fatal, were reported and summarized by organ system describing the most instructive cases in detail. Previously unreported AEs like drug rash with eosinophilia and systemic symptoms (DRESS), granulomatous inflammation of the central nervous system, and aseptic meningitis, were documented. Obstacles included patientś delay in reporting symptoms and the differentiation of steroid-induced from ipilimumab-induced AEs under steroid treatment. Importantly, response rate was high in this patient population with tumor regression in 30.9% and a tumor control rate of 61.8% in stage IV melanoma patients despite the fact that some patients received only two of four recommended ipilimumab infusions. This suggests that ipilimumab-induced antitumor responses can have an early onset and that severe autoimmune reactions may reflect overtreatment.ConclusionThe wide spectrum of ipilimumab-induced AEs demands doctor and patient awareness to reduce morbidity and treatment costs and true ipilimumab success is dictated by both objective tumor responses and controlling severe side effects.

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mmune checkpoint inhibitors activate anti-tumor defenses either through the disruption of inhibitory interactions between antigen-presenting cells and T lymphocytes at so-called checkpoints (anti-PD-1/PD-L1, anti-CTLA-4, anti-TIM-3, anti-LAG-3) or else through the stimulation of activating checkpoints (CD27, CD40, GITR, CD137). They are now used to treat various types of cancer, including lung cancer, renal cell carcinoma, Merkel cell carcinoma, Hodgkin's lymphoma, and urothelial carcinoma (eTable) and special groups of patients, e.g., patients with microsatellite instability (1). In patients with metastatic melanoma, the anti-CTLA-4 antibody ipilimumab, the anti-PD-1 antibodies nivolumab and pembrolizumab, and combination therapy with ipilimumab and an anti-PD-1 antibody can prolong survival and induce response rates of 19% (2), 36-44% (2, 3), and 58-61% (2, 4), respectively. Severe and even life-threatening side effects (classified according to the Common Terminology Criteria for Adverse Events" [CTCAE]; grade 3/4) arise in 17-21% of patients receiving anti-PD-1 monotherapy (2, 3), 20-28% of those receiving ipilimumab (2, 3), 45% of those receiving ipilimumab (1 mg/kg) plus pembrolizumab (4), and 59% of those receiving approved combination therapy with ipilimumab (3 mg/kg) and nivolumab (2) (Table 1). Immune checkpoint inhibitors often induce autoimmune side effects, which can affect all organ systems. These differ from the corresponding spontaneously occurring autoimmune diseases in many ways, including phenotypically, histologically, and serologically. The mechanisms of autoimmune side effects include the activation of T lymphocytes with infiltration of the organ in question (5), direct binding of the checkpoint inhibitor with activation of complement (CTLA-4 expression in the pituitary gland) (6), and immune reactions due to soluble factors (autoantibodies, cytokines). Moreover, the intestinal microbiome seems to influence the development of side effects (7, 8). No predictive factors for the appearance of side effects have yet been identified. Common side effects include colitis, hepatitis, skin reactions, and endocrinopathies (thyroiditis or hypophysitis); rarer ones are myositis, cardiomyositis, and neurological side effects. The side effects are usually readily controllable. Checkpoint inhibitor treatment must be discontinued because of side effects in 7-12% of patients receiving anti-PD-1 therapy, 9-16% of those receiving ipilimumab therapy (2, 3), and 39% of those receiving combination therapy (2).

The recent discovery and characterization of T helper 17 cells (Th17) and their signature cytokines (IL-17) represents a hallmark in T-cell immunobiology by providing a new distinctive pathway for the communication between adaptive and innate immunity. From the six members of the IL-17 cytokine family presently known, at least two have evident proinflammatory qualities and are involved in several chronic inflammatory disorders, including inflammatory bowel disease (IBD). IL-17A and IL-17F are abundantly found in inflamed IBD mucosa, suggesting their pivotal role in IBD. However, the precise implication of IL-17 cytokine family members in IBD pathogenesis and the mechanisms regulating their secretion are incompletely understood. Importantly, recent findings suggest that beyond IL-17 production-Th17 cells may secret a plethora of other effector cytokines such as IL-21, IL-22, and IL-9- which is in part induced by its own IL-9 production. However, the use of anti-IL-17 therapeutic strategies in experimental models of chronic inflammation results in disease-ameliorating effects suggesting their potential use in IBD patients. In this review article we discuss the latest findings on the role of Th17 cells and IL-17 family members in IBD immunopathology, as well as research perspectives.

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