Refractory colitis following anti-CTLA4 antibody therapy: analysis of mucosal FOXP3+ T cells

Corticosteroid-resistant immune-related adverse events: a systematic review

Immune checkpoint inhibitor (ICI) treatment has become an important therapeutic option for various cancer types. Although the treatment is effective, ICI can overstimulate the patient's immune system, leading to potentially severe immune-related adverse events (irAEs), including hepatitis, colitis, pneumonitis and myocarditis. The initial mainstay of treatments includes the administration of corticosteroids. There is little evidence how to treat steroid-resistant (sr) irAEs. It is mainly based on small case series or single case reports. This systematic review summarizes available evidence about sr-irAEs. We conducted a systematic literature search in PubMed. Additionally, we included European Society for Medical Oncology, Society for Immunotherapy of Cancer, National Comprehensive Cancer Network and American Society of Clinical Oncology Guidelines for irAEs in our assessment. The study population of all selected publications had to include patients with cancer who developed hepatitis, colitis, pneumonitis or myocarditis during or after an immunotherapy treatment and for whom corticosteroid therapy was not sufficient. Our literature search was not restricted to any specific cancer diagnosis. Case reports were also included. There is limited data regarding life-threatening sr-irAEs of colon/liver/lung/heart and the majority of publications are single case reports. Most publications investigated sr colitis (n=26), followed by hepatitis (n=21), pneumonitis (n=17) and myocarditis (n=15). There is most data for mycophenolate mofetil (MMF) to treat sr hepatitis and for infliximab, followed by vedolizumab, to treat sr colitis. Regarding sr pneumonitis there is most data for MMF and intravenous immunoglobulins (IVIG) while data regarding infliximab are conflicting. In sr myocarditis, most evidence is available for the use of abatacept or anti-thymocyte globulin (ATG) (both with or without MMF) or ruxolitinib with abatacept. This review highlights the need for prompt recognition and treatment of sr hepatitis, colitis, pneumonitis and myocarditis. Guideline recommendations for sr situations are not defined precisely. Based on our search, we recommend-as first line treatment-(1) MMF for sr hepatitis, (2) infliximab for sr colitis, followed by vedolizumab, (3) MMF and IVIG for sr pneumonitis and (4) abatacept or ATG (both with or without MMF) or ruxolitinib with abatacept for sr myocarditis. These additional immunosuppressive agents should be initiated promptly if there is no sufficient response to corticosteroids within 3 days.

The interplay between the microbiota, diet and T regulatory cells in the preservation of the gut barrier in inflammatory bowel disease

Inflammatory bowel disease (IBD) is becoming more common in the Western world due to changes in diet-related microbial dysbiosis, genetics and lifestyle. Incidences of gut permeability can predate IBD and continued gut barrier disruptions increase the exposure of bacterial antigens to the immune system thereby perpetuating chronic inflammation. Currently, most of the approved IBD therapies target individual pro-inflammatory cytokines and pathways. However, they fail in approximately 50% of patients due to their inability to overcome the redundant pro inflammatory immune responses. There is increasing interest in the therapeutic potential of T regulatory cells (Tregs) in inflammatory conditions due to their widespread capability to dampen inflammation, promote tolerance of intestinal bacteria, facilitate healing of the mucosal barrier and ability to be engineered for more targeted therapy. Intestinal Treg populations are inherently shaped by dietary molecules and gut microbiota-derived metabolites. Thus, understanding how these molecules influence Treg-mediated preservation of the intestinal barrier will provide insights into immune tolerance-mediated mucosal homeostasis. This review comprehensively explores the interplay between diet, gut microbiota, and immune system in influencing the intestinal barrier function to attenuate the progression of colitis.

Immune-related adverse events in checkpoint blockade: Observations from human tissue and therapeutic considerations

Checkpoint inhibitors (CPIs) are monoclonal antibodies which, by disrupting interactions of immune checkpoint molecules with their ligands, block regulatory immune signals otherwise exploited by cancers. Despite revolutionary clinical benefits, CPI use is associated with an array of immune-related adverse events (irAEs) that mirror spontaneous autoreactivity. Severe irAEs necessitate pausing or stopping of CPI therapy and use of corticosteroids and/or other immunomodulatory interventions. Despite increasingly widespread CPI use, irAE pathobiology remains poorly understood; its elucidation may point to targeted mitigation strategies and uncover predictive biomarkers for irAE onset in patients, whilst casting new light on mechanisms of spontaneous immune-mediated disease. This review focuses on common CPI-induced irAEs of the gut, skin and synovial joints, and how these compare to immune-mediated diseases such as ulcerative colitis, vitiligo and inflammatory arthritis. We review current understanding of the immunological changes reported following CPI therapy at the level of peripheral blood and tissue. Many studies highlight dysregulation of cytokines in irAE-affected tissue, particularly IFNγ and TNF. IrAE-affected tissues are also predominantly infiltrated by T-cells, with low B-cell infiltration. Whilst there is variability between studies, patients treated with anti-programmed cell death-1 (PD-1)/PDL-1 therapies seem to exhibit CD8+ T-cell dominance, with CD4+ T-cells dominating in those treated with anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) monotherapy. Interestingly, CD8+CXCR3+ T-cells have been reported to be elevated in gastrointestinal, dermatological and musculoskeletal -irAE affected tissues. These findings may highlight potential opportunities for therapeutic development or re-deployment of existing therapies to prevent and/or improve the outcome of irAEs.

Immunotherapy and Gastrointestinal Toxicities

Gastrointestinal toxicities secondary to immune checkpoint inhibitors are very frequent. Because in some instances this can be severe or fatal, it is essential to be able to identify immune-related adverse events rapidly. Prompt initiation of systemic immunosuppression can improve outcomes. A biopsy is often necessary to confirm the diagnosis of immune-related adverse events. Moderate or severe irAEs need an interruption of ICI. After the resolution of the toxicities, the rechallenge of immune checkpoint inhibitors must be discussed case by case.

Role of Abdominal and Pelvic CT Scans in Diagnosis of Patients with Immunotherapy-Induced Colitis

Introduction:

Colitis is one of the most common immune-related adverse events in patients receiving immune checkpoint inhibitors. Although radiographic changes on computed tomography (CT), such as mild diffuse bowel thickening, mesenteric fat stranding, and mucosal enhancement, have been reported, the utility of CT in diagnosis of patients with suspected immune-related colitis is not well documented. The aim of this retrospective study was to determine the value of CT scans in diagnosis of immunotherapy-induced colitis.

Methods:

CT scans of the abdomen and pelvis of 34 patients receiving immunotherapy who had a clinical diagnosis of immunotherapy-induced colitis and 19 patients receiving immunotherapy without clinical symptoms of colitis (controls) were evaluated. Segments of the colon (rectum, sigmoid, descending, transverse, ascending, and cecum) were assessed independently by two abdominal imaging specialists, blinded to the clinical diagnosis. Each segment was assessed for radiographic signs such as mucosal enhancement, wall thickening, distension, and periserosal fat stranding. The presence of any of the signs was considered radiographic evidence of colitis.

Results:

CT findings suggestive of colitis was seen in 20 of 34 patients with symptoms of colitis and in 5 of 19 patients without symptoms of colitis. The sensitivity, specificity, positive predictive value, and negative predictive value for colitis on CT were 58.8%, 73.7%, 80%, and 50%, respectively.

Conclusions:

We found that CT had a low sensitivity, specificity, and negative predictive value for the diagnosis of immunotherapy-induced colitis. We therefore conclude that CT has a limited role in the diagnosis of patients with suspected uncomplicated immune-related colitis.

Pharmacological Interventions for the Prevention and Treatment of Immune Checkpoint Inhibitor-Associated Enterocolitis: A Systematic Review

BACKGROUND

Patients treated with immune checkpoint inhibitors (ICIs) may develop ICI-associated enterocolitis, for which there is no approved treatment.

AIMS

We aimed to systematically review the efficacy and safety of medical interventions for the prevention and treatment of ICI-associated enterocolitis.

METHODS

MEDLINE, EMBASE, and the Cochrane Library were searched to identify randomized controlled trials (RCTs), cohort and case-control studies, and case series/reports, evaluating interventions (including corticosteroids, biologics, aminosalicylates, immunosuppressants, and fecal transplantation) for ICI-associated enterocolitis. Clinical, endoscopic, and histologic efficacy endpoints were evaluated. The Grading of Recommendations, Assessment, Development, and Evaluation criteria were used to assess overall quality of evidence.

RESULTS

A total of 160 studies (n = 1514) were included (one RCT, 3 retrospective cohort studies, 156 case reports/case series). Very low quality evidence from one RCT suggests budesonide is not effective for prevention of ICI-associated enterocolitis in ipilimumab-treated patients (relative risk 0.93 [95% confidence interval 0.56, 1.56]). Very low quality evidence suggests that corticosteroids, infliximab, and vedolizumab may be effective for treatment of ICI-associated enterocolitis by inducing clinical response and remission. No validated indices for measuring disease activity were used. Biologic treatment was used in 42% (641/1528) of patients, as reported in 97 studies. ICIs were discontinued in 65% (457/702) of patients, as reported in 63 studies.

CONCLUSIONS

Current treatment recommendations for ICI-associated enterocolitis are based on very low quality evidence, primarily from case reports and case series. Large-scale prospective cohort studies and RCTs are needed to develop prophylactic and therapeutic treatments to minimize interruption or discontinuation of oncological therapies.

Vedolizumab Attenuates Immune-Checkpoint-Therapy-Induced Infliximab-Refractory Colitis

Immune checkpoint inhibitors (ICIs), such as nivolumab and ipilimumab, have drastically changed treatments of advanced melanoma. However, ICI-related enterocolitis is often the most common adverse event, and represents the main reason for ICI discontinuation and mortalities. Here, we report the case of a metastatic melanoma treated with vedolizumab for ICI-induced colitis. A 67-year-old man treated with ipilimumab and nivolumab developed ICI-induced colitis and grade 3 diarrhea refractory to methylprednisolone and infliximab. After his third dose of vedolizumab, oral prednisolone ceased, and the colitis had completely resolved with no recurrence. This case report supports vedolizumab use in treating severe colitis which failed to resolve with first- and second-line immunosuppressive therapy.

Immune Checkpoint Inhibitor-Associated Colitis: From Mechanism to Management

Immune checkpoint inhibitors (ICIs), as one of the innovative types of immunotherapies, including programmed cell death-1 (PD-1), programmed cell death-ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors, have obtained unprecedented benefit in multiple malignancies. However, the immune response activation in the body organs could arise immune-related adverse events (irAEs). Checkpoint inhibitor colitis (CIC) is the most widely reported irAEs. However, some obscure problems, such as the mechanism concerning gut microbiota, the confusing differential diagnosis with inflammatory bowel disease (IBD), the optimal steroid schedule, the reintroduction of ICIs, and the controversial prognosis features, influence the deep understanding and precise diagnosis and management of CIC. Herein, we based on these problems and comprehensively summarized the relevant studies of CIC in patients with NSCLC, further discussing the future research direction of this specific pattern of irAEs.

Immune Checkpoint Blockade and Skin Toxicity Pathogenesis

Immune checkpoint blockade has revolutionized the treatment of multiple tumor types, including melanoma and nonmelanoma skin cancers. The use of immune checkpoint blockade is curtailed by tissue toxicities termed immune-related adverse events (irAEs), which occur most quickly and most often in the skin. We review the rationale for immune checkpoint blockade use, current agents, use in skin cancers, autoimmune manifestations in the skin, and considerations for predictive biomarkers and treatment options on the basis of skin pathogenesis. We also highlight major gaps in the field and the lack of preclinical modeling in the skin. A deeper understanding of irAE pathophysiology may help to uncouple toxicity and efficacy but mandates an interdisciplinary approach, including foundational skin immunology and autoimmune pathogenesis.

Mechanisms of Immune Checkpoint Inhibitor-Mediated Colitis

Immune checkpoint inhibitors (ICIs) have provided tremendous clinical benefit in several cancer types. However, systemic activation of the immune system also leads to several immune-related adverse events. Of these, ICI-mediated colitis (IMC) occurs frequently and is the one with the highest absolute fatality. To improve current treatment strategies, it is important to understand the cellular mechanisms that induce this form of colitis. In this review, we discuss important pathways that are altered in IMC in mouse models and in human colon biopsy samples. This reveals a complex interplay between several types of immune cells and the gut microbiome. In addition to a mechanistic understanding, patients at risk should be identifiable before ICI therapy. Here we propose to focus on T-cell subsets that interact with bacteria after inducing epithelial damage. Especially, intestinal resident immune cells are of interest. This may lead to a better understanding of IMC and provides opportunities for prevention and management.

Infections due to dysregulated immunity: an emerging complication of cancer immunotherapy

Immune checkpoint inhibitors (ICIs) have revolutionised cancer treatment. However, immune-related adverse events (irAEs) are a common side effect which can mimic infection. Additionally, treatment of irAEs with corticosteroids and other immunosuppressant agents can lead to opportunistic infection, which we have classed as immunotherapy infections due to immunosuppression. However, emerging reports demonstrate that some infections can be precipitated by ICIs in the absence of immunosuppressive treatment, in contrast to the majority of reported cases. These infections are characterised by a dysregulated inflammatory immune response, and so we propose they are described as immunotherapy infections due to dysregulated immunity. This review summarises the rapidly emerging evidence of these phenomena and proposes a new framework for considering infection in the context of cancer immunotherapy.

Immunopathological basis of immune-related adverse events induced by immune checkpoint blockade therapy

Despite the considerable success of cancer immunotherapy with immune checkpoint inhibitors, their nonspecific release of the immunosuppressive mechanism is often associated with immune-related adverse events (irAEs). irAEs significantly disturb patients' quality of life and can even be life-threatening. Therefore, the appropriate management of irAEs is crucial for the development of further reliable cancer immunotherapies. irAEs have the appearance of ordinary autoimmune diseases in one aspect but often have distinct features. Although the detailed pathogenesis of irAEs remains unclear, increasing numbers of studies have provided numerous clues. Here, we review the current knowledge on irAEs, particularly from an immunopathological basis.

Inhibitors of immune checkpoints-PD-1, PD-L1, CTLA-4-new opportunities for cancer patients and a new challenge for internists and general practitioners

The treatment of cancer patients with immune checkpoint inhibitors (ICI) (anti-CTLA-4, anti-PD-1, anti-PD-L1, combined therapy anti-PD-1/PD-L1 with anti-CTLA-4) has without doubt been a significant breakthrough in the field of oncology in recent years and constitutes a major step forward as a novel type of immunotherapy in the treatment of cancer. ICIs have contributed to a significant improvement in the outcome of treatment and prognosis of patients with different types of malignancy. With the expansion of the use of ICIs, it is expected that caregivers will face new challenges, namely, they will have to manage the adverse side effects associated with the use of these drugs. New treatment options pose new challenges not only for oncologists but also for specialists in other clinical fields, including general practitioners (GPs). They also endorse the need for taking a holistic approach to the patient, which is a principle widely recognized in oncology and especially relevant in the case of the expanding use of ICIs, which may give rise to a wide variety of organ complications resulting from treatment. Knowledge and awareness of the spectrum of immune-related adverse events (irAEs) will allow doctors to qualify patients for treatment more appropriately, prevent complications, correctly recognize, and ultimately treat them. Additionally, patients with more non-specific symptoms would be expected, in the first instance, to consult their general practitioners, as complications may appear even after the termination of treatment and do not always proceed in line with disease progression. Dealing with any iatrogenic complications, will not only be the remit of oncologists but because of the likelihood that specific organs may be affected, is likely to extend also to specialists in various fields of internal medicine. These specialists, e.g., endocrinologists, dermatologists, pulmonologists, and gastroenterologists, are likely to receive referrals for patients suffering from specific types of adverse events or will be asked to provide care in cases requiring hospitalization of patients with complications in their field of expertise. In view of these considerations, we believe that there is an urgent need for multidisciplinary teamwork in the treatment of cancer patients undergoing immunotherapy and suffering the consequent adverse reactions to treatment.

Checkpoint Inhibitor Colitis Shows Drug-Specific Differences in Immune Cell Reaction That Overlap With Inflammatory Bowel Disease and Predict Response to Colitis Therapy

OBJECTIVES

Checkpoint inhibitor (CPI)-associated colitis can limit therapy and has resemblance to inflammatory bowel disease (IBD). Studies exploring mechanistic similarities between these colitides are limited, yet therapeutic targets for either disorder could emerge from shared pathophysiology.

METHODS

The morphology and inflammatory content of colonic biopsy specimens from anti-CTLA-4 and anti-PD-1/PD-L1 antibody-treated patients with CPI colitis were compared with initial biopsy specimens from patients with IBD. Predictors of the need for infliximab were sought in CPI patients.

RESULTS

Biopsy specimens from CPI patients showed significantly lower chronicity scores and similar activity scores compared with patients with IBD. Anti-CTLA-4 and IBD groups showed equivalent CD8, CD4, PD-1, and PD-L1 expression, while FoxP3 scores were lower and CD68 scores were higher in anti-CTLA-4 compared with IBD biopsy specimens. Anti-PD-1/PD-L1 group had lower scores for CD8, CD4, and PD-1 and equivalent scores for FoxP3, PD-L1, and CD68 compared with IBD. Anti-CTLA-4 biopsy specimens had higher scores for CD8, PD-1, PD-L1, and CD68 than anti-PD-1/PD-L1 biopsy specimens. CD8/FoxP3 ratios and CD68 scores were higher among CPI patients requiring infliximab therapy for colitis compared with those responding to steroids.

CONCLUSIONS

The proinflammatory immune phenotype of anti-CTLA-4-associated colitis has significant overlap with IBD. CD8/FoxP3 ratios may predict therapeutic response in CPI-associated colitis.

Distribution of mucosal PD-1 expressing T cells in patients with colitis of different etiologies

BACKGROUND

Immunotherapy, targeting programmed death-1 (PD-1) enhances antitumor T-cell activity in patients with malignancies. Blocking PD-1 or its ligand may lead to fulminant colitis as serious adverse event in these patients. Since little is known of the presence and role of PD-1⁺T cells in colitis of different etiologies, we determined PD-1⁺T cells in mucosal specimens of patients with inflammatory bowel disease, infectious colitis (InfC), immunotherapy-related colitis (ImC) and healthy controls (HC).

METHODS

Newly diagnosed patients with ulcerative colitis (UC, n = 73), Crohn's disease (CD, n = 50), InfC (n = 5), ImC (n = 8) and HC (n = 8) were included. Baseline inflamed colonic biopsies were studied with immunohistochemistry and flowcytometry.

RESULTS

Using immunohistochemistry, PD-1 was not present on lymphocytes in the epithelium of all patients, nor in HC. The percentage PD-1⁺ of all lymphocytes in the lamina propria was 40% in UC, 5% in InfC, 3% in ImC and 0% in HC. Flowcytometry showed significant higher percentages of PD-1⁺T cells in inflamed biopsy specimens of UC patients (22%) compared to all other groups: CD patients (13%), InfC (12%), ImC (5%) and HC (6%).

CONCLUSION

There are relevant differences in distribution and frequencies of mucosal PD-1⁺ T-cell subsets in patients with UC, CD, InfC and ImC, supporting the hypothesis that these types of colitis are driven by different immunological pathways. The increased numbers of PD-1⁺ and PD-L1⁺ lymphocytes in the colonic mucosa of UC patients suggest that the PD-1/PD-L1 pathway might be more activated in UC than in CD.

Long-term immune-related adverse events after discontinuation of immunotherapy

Immune checkpoint inhibitors have revolutionized the treatment of various cancers but are notorious for their potential to cause severe side effects. While most side effects occur during ongoing therapy, an increasing number of reports of late onset have emerged. It is also not yet clear how long side effects can last. Resolution is achieved under symptomatic therapy, but the side effects may persist latently. We present a patient case with recurrence of colitis after closure of an ileostomy over 1 year after discontinuation of immune checkpoint inhibitor therapy with nivolumab and ipilimumab. To the best of our knowledge, no other case with severe colitis still lasting after more than a year of suspension of therapy has yet been reported.

Checkpoint Inhibitor-Induced Colitis-A Clinical Overview of Incidence, Prognostic Implications and Extension of Current Treatment Options

In recent years, anti-tumor immunotherapies have witnessed a major breakthrough with the emergence of immune checkpoint inhibitors (ICIs). However, the use of ICIs has also brought an era of a certain class of adverse events that differ from those of classical chemotherapies and are more reminiscent of autoimmune diseases. This article focuses exclusively on colitis as an irAE with emphasis on vulnerable patient groups, the prognostic significance of colitis, treatment, and new therapeutic approaches that may be applicable. Colitis itself is associated with a favorable oncological outcome of the underlying disease but is as well the most common irAE leading to discontinuation of therapy. Especially in vulnerable patient groups such as IBD patients and elderly patients, colitis occurs more frequently as a side effect. It is precisely in these two patient groups that side effects more often lead to discontinuation of therapy. Therefore, in addition to the current therapy of colitis through immunosuppression, the focus should also be on new forms of therapy of severe colitis, such as fecal transplantation or ileostomy creation.

Antitumor efficacy of combined CTLA4/PD-1 blockade without intestinal inflammation is achieved by elimination of FcγR interactions

Background

Programmed cell death protein 1 (PD-1) and CTLA4 combination blockade enhances clinical efficacy in melanoma compared with targeting either checkpoint alone; however, clinical response improvement is coupled with increased risk of developing immune-related adverse events (irAE). Delineating the mechanisms of checkpoint blockade-mediated irAE has been hampered by the lack of animal models that replicate these clinical events.

Methods

We have developed a mouse model of checkpoint blockade-mediated enterocolitis via prolonged administration of an Fc-competent anti-CTLA4 antibody.

Results

Sustained treatment with Fc-effector, but not Fc-mutant or Fc-null, anti-CTLA4 antagonist for 7 weeks resulted in enterocolitis. Moreover, combining Fc-null or Fc-mutant CTLA4 antagonists with PD-1 blockade results in potent antitumor combination efficacy indicating that Fc-effector function is not required for combination benefit.

Conclusion

These data suggest that using CTLA4 antagonists with no Fc-effector function can mitigate gut inflammation associated with anti-CTLA4 antibody therapy yet retain potent antitumor activity in combination with PD-1 blockade.

Immunotherapy induced enterocolitis and gastritis - What to do and when?

Oncological treatment has been revolutionised by the advent of immune checkpoint inhibitors (ICPi), which block inhibitory immune pathways to enhance anti-tumour responses and improve survival. This mode of action is non-specific so can cause immune-related adverse events, of which diarrhoea and enterocolitis are amongst the most common. ICPi-enterocolitis frequently leads to cancer therapy interruption. ICPi-gastritis typically occurs at a later stage of ICPi therapy and can present more insidiously with nausea and vomiting. ICPi-enterocolitis and gastritis are treated with corticosteroids, with refractory cases typically requiring biologic therapy. This review will briefly consider the pathogenesis of ICPi-induced GI disease, before focussing on the practical management of these conditions. The anticipated global increase in ICPi use across cancer types highlights the importance of prospective research in order that we can understand the immuno-microbiology of ICPi-enterocolitis and gastritis. This will lead to predictive biomarkers and help to define optimal treatment regimens.

Campylobacteriosis following immunosuppression for immune checkpoint inhibitor-related toxicity

Five patients receiving checkpoint inhibitor immunotherapy (CPI) under our care across two cancer centers over a 12-month period have subsequently developed campylobacterosis. All had received immune-suppressive treatment for CPI-related colitis in the weeks or months preceding the detection of Campylobacter infection, with negative stool cultures at presentation of CPI-related colitis. The immune-suppression required to treat CPI-related toxicity may lead to an increased risk of enteric infection within the gut. While the underlying immune and biologic mechanisms are not well understood, perturbation of the gut microbiota is an increasingly recognized factor capable of influencing CPI-mediated immune reconstitution and response to therapy. Clinicians should be aware that worsening of colitic symptoms in patients with a history of treatment for CPI-related colitis may be due to enteric infection, and not simply a relapse/deterioration of a previously treated CPI-related colitis. Judicious infectious disease evaluation is necessary for patients receiving CPIs as symptoms can mimic immune-related adverse events (irAEs). Furthermore, the benefits of immune-suppressive therapy for the treatment of presumptive irAEs must be weighed against the possible increased risk for either enteric infection or opportunistic infection. Prospective studies are required to investigate microbiome perturbations, resulting from immune-suppression, and guide future treatment of this patient cohort.

Abdominal CT manifestations of adverse events to immunotherapy: a primer for radiologists

Immunotherapy is a rapidly growing field within oncology and is being increasingly used in the management of several malignancies. Due to their unique mechanism of action on the immune system and neoplastic cells, the response pattern and adverse events of this novel therapy are distinct from conventional systemic therapies. Accordingly, the imaging appearances following immunotherapy including adverse events are unique and at times perplexing. Imaging is integral to management of patients on immunotherapeutic agents and a thorough understanding of its mechanism, response patterns and adverse events is crucial for precise interpretation of imaging studies. This review provides a description of the mechanism of action of current immunotherapeutic agents and the organ-wise description of their side effects.

Mucosal-associated invariant T (MAIT) cells are activated in the gastrointestinal tissue of patients with combination ipilimumab and nivolumab therapy-related colitis in a pathology distinct from ulcerative colitis

The aim of this study was to investigate the pathogenesis of combination ipilimumab and nivolumab-associated colitis (IN-COL) by measuring gut-derived and peripheral blood mononuclear cell (GMNC; PBMC) profiles. We studied GMNC and PBMC from patients with IN-COL, IN-treated with no adverse-events (IN-NAE), ulcerative colitis (UC) and healthy volunteers using flow cytometry. In the gastrointestinal-derived cells we found high levels of activated CD8⁺ T cells and mucosal-associated invariant T (MAIT) cells in IN-COL, changes that were not evident in IN-NAE or UC. UC, but not IN-C, was associated with a high proportion of regulatory T cells (T_reg ). We sought to determine if local tissue responses could be measured in peripheral blood. Peripherally, checkpoint inhibition instigated a rise in activated memory CD4⁺ and CD8⁺ T cells, regardless of colitis. Low circulating MAIT cells at baseline was associated with IN-COL patients compared with IN-NAE in one of two cohorts. UC, but not IN-COL, was associated with high levels of circulating plasmablasts. In summary, the alterations in T cell subsets measured in IN-COL-affected tissue, characterized by high levels of activated CD8⁺ T cells and MAIT cells and a low proportion of T_reg , reflected a pathology distinct from UC. These tissue changes differed from the periphery, where T cell activation was a widespread on-treatment effect, and circulating MAIT cell count was low but not reliably predictive of colitis.

British Society of Gastroenterology endorsed guidance for the management of immune checkpoint inhibitor-induced enterocolitis

Immune checkpoint inhibitors are a novel class of cancer treatment that have improved outcomes for a subset of cancer patients. They work by antagonising inhibitory immune pathways, thereby augmenting immune-mediated antitumour responses. However, immune activation is not cancer-specific and often results in the activation of immune cells in non-cancer tissues, resulting in off-target immune-mediated injury and organ dysfunction. Diarrhoea and gastrointestinal tract inflammation are common and sometimes serious side-effects of this type of therapy. Prompt recognition of gastrointestinal toxicity and, in many cases, rapid institution of anti-inflammatory or biologic therapy (or both) is required to reverse these complications. Management of organ-specific complications benefits from multidisciplinary input, including engagement with gastroenterologists for optimal management of immune checkpoint inhibitor-induced enterocolitis. In this British Society of Gastroenterology endorsed guidance document, we have developed a consensus framework for the investigation and management of immune checkpoint inhibitor-induced enterocolitis.

Gastrointestinal Tract Adverse Events

Immune checkpoint inhibitors (ICIs) have shown significant benefit in cancer patients. Their success, however, is associated with immune-related adverse events (irAEs), which commonly affect the gastrointestinal tract, resulting in diarrhea and colitis. IrAEs range from mild self-limiting to severe life-threatening diseases and potentially limit the use of these medications. Diagnosis of ICI-induced enterocolitis is based on clinical symptoms, physical examination, stool tests, endoscopic and histologic evaluation, and/or imaging. Current management strategy is mainly anti-diarrheal agents for mild symptoms and immunosuppressants (e.g., corticosteroids, and infliximab or vedolizumab) for more severe diseases.

Molecular Pathways of Colon Inflammation Induced by Cancer Immunotherapy

Checkpoint blockade with antibodies specific for the PD-1 and CTLA-4 inhibitory receptors can induce durable responses in a wide range of human cancers. However, the immunological mechanisms responsible for severe inflammatory side effects remain poorly understood. Here we report a comprehensive single-cell analysis of immune cell populations in colitis, a common and severe side effect of checkpoint blockade. We observed a striking accumulation of CD8 T cells with highly cytotoxic and proliferative states and no evidence of regulatory T cell depletion. T cell receptor (TCR) sequence analysis demonstrated that a substantial fraction of colitis-associated CD8 T cells originated from tissue-resident populations, explaining the frequently early onset of colitis symptoms following treatment initiation. Our analysis also identified cytokines, chemokines, and surface receptors that could serve as therapeutic targets for colitis and potentially other inflammatory side effects of checkpoint blockade.

Pathology of immune-mediated tissue lesions following treatment with immune checkpoint inhibitors

Immune check point inhibitor (CPI) therapy has revolutionized treatment paradigms for several cancers, but at the cost of triggering a diverse spectrum of immune-mediated injury to non-cancer tissues. The complex biology of these toxicities remains incompletely understood, partly because tissue acquisition from affected areas can be challenging to retrieve, thus hindering development of targeted therapy. Here, we review the literature describing pathology of immune-mediated tissue lesions including gastrointestinal, skin, rheumatic, pulmonary, cardiac, renal and hepatic lesions and highlight key immunological insights.

Immune-Mediated Colitis

PURPOSE OF REVIEW

This review addresses our current knowledge of immune-mediated colitis (IMC) and offers a practical guide to its management.

RECENT FINDINGS

Due to the similarity in clinical, endoscopic, and histologic findings between IMC and inflammatory bowel disease (IBD), gastroenterologists have tailored their approach to IMC management to that of IBD. Immune checkpoint inhibitors (ICIs) are monoclonal antibodies that augment the T-cell anti-tumor response of the immune system and have demonstrated their importance in the treatment of a wide range of malignancies. With the growing benefits of ICIs, there are immune-related adverse events (irAEs) that mirror many known autoimmune diseases. Diarrhea and IMC are the most common and severe irAEs noted. No standardized guidelines exist in the management of these irAEs.

Severe colitis after PD-1 blockade with nivolumab in advanced melanoma patients: potential role of Th1-dominant immune response in immune-related adverse events: two case reports

BACKGROUND

Nivolumab is an immune checkpoint inhibitor specific to the programmed death 1 (PD-1) receptor. Nivolumab has shown clinical responses in many malignancies. Although immune-related adverse events (irAEs) associated with nivolumab are largely tolerable, severe irAEs have occurred in some patients. However, the mechanisms underlying the development of irAEs are not fully clarified.

CASE PRESENTATION

We report 2 patients with metastatic melanoma who developed colitis, an irAEs caused by nivolumab. Both patients experienced colitis after nivolumab administration. Pathological examination of the colon showed robust infiltration of CD8⁺ cells and T-bet expressing CD4⁺ cells in both cases, indicating helper T cells (Th) 1 to be responsible for the dominant response. Additionally, we observed the serum C-reactive protein level (CRP) as well as interleukin-6 (IL-6) reflected the clinical course of irAEs clearly in the two cases.

CONCLUSION

Our two cases suggested that the development of irAEs due to nivolumab is associated with Th1 dominant response. CRP as well as IL-6 was found to be a potential biomarker for irAEs. Our findings may help to understand the mechanisms underlying irAEs caused by nivolumab and manage irAEs in clinical practice.

Impact of the gut microbiota on immune checkpoint inhibitor-associated toxicities

Immune checkpoint inhibitors (ICIs) have transformed the treatment of patients with advanced cancers. However, the majority of patients do not respond or develop early progressive disease. A substantial number also develop immune-mediated toxicities that may lead to early treatment discontinuation. Gastrointestinal toxicities in the form of diarrhea and colitis are common and may resemble that observed in patients with inflammatory bowel disease (IBD). Alterations in the gut microbiota are thought to play an important role in mediating the intestinal inflammation that is associated with immune-mediated colitis. In this review, the authors' objective is to provide an overview of the gastrointestinal and hepatic toxicities that can be seen with ICIs and discuss the interactions between gut microbiota and the immune response. The authors also highlight the potential role for fecal microbial transfer (FMT) as an approach to improve therapeutic efficacy and decrease toxicity.

Immune checkpoint inhibitor-induced diarrhea/colitis: Endoscopic and pathologic findings

The indications of immune checkpoint inhibitors (ICPIs) for cancer treatment have rapidly expanded, and their use is increasing in clinical settings worldwide. Despite the considerable clinical benefits of ICPIs, frequent immune-related adverse events (irAEs) have become nonnegligible concerns. Among irAEs, ICPI-induced colitis/diarrhea is frequent and recognized not only by oncologists but also by gastroenterologists or endoscopists. The endoscopic findings show similarity to those of inflammatory bowel disease to a certain extent, particularly ulcerative colitis, but do not seem to be identical. The pathological findings of ICPI-induced colitis may vary among drug classes. They show acute or chronic inflammation, but it may depend on the time of colitis suggested by colonoscopy, including biopsy or treatment intervention. In the case of chronic inflammation determined by biopsy, the endoscopy findings may overlap with those of inflammatory bowel disease. Here, we provide a comprehensive review of ICPI-induced colitis based on clinical, endoscopic and pathologic findings.

Translating Immunology into Therapeutic Concepts for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) defines a spectrum of complex disorders. Understanding how environmental risk factors, alterations of the intestinal microbiota, and polygenetic and epigenetic susceptibility impact on immune pathways is key for developing targeted therapies. Mechanistic understanding of polygenic IBD is complemented by Mendelian disorders that present with IBD, pharmacological interventions that cause colitis, autoimmunity, and multiple animal models. Collectively, this multifactorial pathogenesis supports a concept of immune checkpoints that control microbial-host interactions in the gut by modulating innate and adaptive immunity, as well as epithelial and mesenchymal cell responses. In addition to classical immunosuppressive strategies, we discuss how resetting the microbiota and restoring innate immune responses, in particular autophagy and epithelial barrier function, might be key for maintaining remission or preventing IBD. Targeting checkpoints in genetically stratified subgroups of patients with Mendelian disorder-associated IBD increasingly directs treatment strategies as part of personalized medicine.

Systematic review and case series: flexible sigmoidoscopy identifies most cases of checkpoint inhibitor-induced colitis

BACKGROUND

Immune checkpoint inhibitors are used in the treatment of multiple advanced stage cancers but can induce immune-mediated colitis necessitating treatment with immunosuppressive medications. Diagnostic colonoscopy is often performed but requires bowel preparation and may delay diagnosis and treatment. Sigmoidoscopy can be performed rapidly without oral bowel preparation or sedation.

AIMS

Characterize the colonic distribution of immune-mediated colitis to determine the most efficient endoscopic approach.

METHODS

A systematic review of checkpoint inhibitor-induced colitis case reports and series was conducted in both PubMed and Embase through 3 January 2017. A single centre retrospective chart review of patients who underwent endoscopic evaluation for diarrhoea after treatment with a checkpoint inhibitor (ipilimumab, nivolumab or pembrolizumab) between 1 January 2011 and 3 January 2017 was performed. Clinical, endoscopic and histologic data were collected.

RESULTS

A detailed systematic review resulted in 61 studies, in which 226 cases of colitis were diagnosed by lower endoscopy (125 colonoscopy, 101 sigmoidoscopy). Only four patients had isolated findings proximal to the left colon. In our centre, 31 patients had histologic features of checkpoint inhibitor-induced colitis, for which 29 patients had complete data. The left colon was involved in all cases. Sigmoidoscopy would be sufficient to diagnose >98% of reported cases of checkpoint inhibitor-mediated colitis diagnosed by lower endoscopy.

CONCLUSIONS

Moderate to severe checkpoint inhibitor-induced colitis involves the left colon in the majority of cases (>98%). Sigmoidoscopy should be the initial endoscopic procedure in the evaluation of this condition.

Review of Drug-induced Injury in Mucosal Biopsies From the Tubular Gastrointestinal Tract

The use of prescription and over-the-counter medications is on the rise in the US population, especially among those aged 65 and over, with over 46% of the population taking at least 1 prescription medication. Given the frequency of medication use, and that the majority of these medications are taken orally, it has become increasingly relevant for pathologist examining endoscopically obtained gastrointestinal tract mucosal biopsies to consider and recognize patterns of mucosal injury associated with various drugs. Reports on injuries associated with certain classes of drugs can be scattered among different sources, making a comprehensive view of various injury patterns and the drugs known to cause them difficult to obtain. Herein, we provide a comprehensive overview of the drugs known to cause mucosal injuries in the tubular gastrointestinal tract organized by the organ involved and the prominent pattern of injury.

[The pathology of adverse events with immune checkpoint inhibitors]

BACKGROUND

Immunotherapy has gained importance with the development of new effective cancer treatments. Immune checkpoint inhibitors (ICI) are monoclonal antibodies that promote T‑cell mediated tumor immune rejection. Checkpoint blockade also carries the risk of inducing autoimmune reactions ("immune related adverse events", irAEs). The diagnosis and classification of irAEs constitute a new and important field in pathology.

AIM

Practice-oriented review of the diagnosis and classification of irAEs.

MATERIALS AND METHODS

Structured, selective literature review based on PubMed und UpToDate ® online.

RESULTS

The most common irAEs affect the skin, the gastrointestinal tract, the liver, and the respiratory system. The correct diagnosis and classification of irAEs by an interdisciplinary care team is essential for appropriate therapy and the prevention of long-term sequelae. Other important irAEs affect the endocrine organs, the heart, the joints, the kidneys and the nervous system. Because of their rarity and/or limited options for bioptic diagnosis, only limited data on the morphology and pathophysiology of these irAEs are currently available. Autopsies carried out after ICI therapy constitute an important element of quality control and allow better documentation of the incidence and pathogenesis of irAEs.

DISCUSSION

Pathology plays a central role in the diagnosis and treatment of irAEs. Future studies may contribute to a better mechanistic understanding of irAEs for individualized knowledge-based risk assessment.

Acute liver injury in the context of immune checkpoint inhibitor-related colitis treated with infliximab

Background

Immune checkpoint inhibitors (ICPIs), used to treat different advanced malignancies, are associated with a wide range of immune-related adverse reactions (irAEs) that deserve close monitoring of patients. Gastrointestinal reactions and hepatotoxicity may occur, which warrant careful evaluation to confirm the etiology and attribution to ICPIs as these events could affect future management.

Case presentation

We describe a case of a patient with prostate adenocarcinoma, treated with dual ICPIs comprised of ipilimumab and nivolumab, who developed elevated liver enzymes in the context of infliximab therapy prescribed to treat gastrointestinal irAE from his ICPIs. The patient’s grade 3 colitis became steroid-refractory, requiring a one-time infusion of infliximab, a biologic agent used commonly in inflammatory bowel disease, as a rescue therapy, to which he responded. The patient subsequently developed liver injury. This presented a diagnostic dilemma involving differential diagnoses of hepatotoxicity due to ICPI or infliximab exposure. A careful review of the clinical history, evaluation of the chronology of events, and exclusion of other causes of acute hepatitis were employed to make the final diagnosis of this event as infliximab-associated hepatotoxicity.

Conclusion

ICPIs such as CTLA-4 and PD-1 inhibitors have the potential to cause both gastrointestinal reactions and hepatotoxicity. An additional confounding factor in our patient’s case was the exposure to infliximab used to manage an established irAE that developed after the last exposure to ICPIs. The clinical history and data supported infliximab-associated hepatotoxicity, rather than an irAE. With the increasing application of ICPIs for different cancers, in conjunction with potential risks for irAE, the liver profile should be closely monitored during treatment with ICPI as well as with anti-TNF-α agents in this patient population.

Severe toxicity from checkpoint protein inhibitors: What intensive care physicians need to know?

Checkpoint protein inhibitor antibodies (CPI), including cytotoxic T-lymphocyte-associated antigen 4 inhibitors (ipilimumab, tremelimumab) and the programmed cell death protein 1 pathway/programmed cell death protein 1 ligand inhibitors (pembrolizumab, nivolumab, durvalumab, atezolizumab), have entered routine practice for the treatment of many cancers. They improve the outcome for many cancers, and more patients will be treated with CPI in the future. Although CPI can lead to adverse events (AE) less frequently than for chemotherapy, their use can require intensive care unit admission in case of severe immune-related adverse events (IrAE). Moreover, some of these events, particularly late events, are poorly documented, so a high level of suspicion should be maintained for patients receiving CPI. Intensivists should be aware in general of the known complications and appropriate management of these AE. Nevertheless, a multidisciplinary collaboration remains essential for their diagnosis and management. This review described the most severe complications related to CPI.

Tipping the balance: inhibitory checkpoints in intestinal homeostasis

The small intestinal and colonic lamina propria are populated with forkhead box P3 (FOXP3)⁺CD4⁺ regulatory T cells (Tregs) and interleukin-10-producing T cells that orchestrate intestinal tolerance to harmless microbial and food antigens. Expression of co-inhibitory receptors such as CTLA-4 and PD-1 serve as checkpoints to these cells controlling their T-cell receptor (TCR)-mediated and CD28-mediated activation and modulating the phenotype of neighboring antigen presenting cells. Recent discoveries on the diversity of co-inhibitory receptors and their selective cellular expression has shed new light on their tissue-dependent function. In this review, we provide an overview of the co-inhibitory pathways and checkpoints of Treg and effector T cells and their mechanisms of action in intestinal homeostasis. Better understanding of these inhibitory checkpoints is desired as their blockade harbors clinical potential for the treatment of cancer and their stimulation may offer new opportunities to treat chronic intestinal inflammation such as inflammatory bowel disease.

Management of Gastrointestinal Toxicity from Immune Checkpoint Inhibitor

Immune checkpoint inhibitors have shown anti-tumour activity in cancers such as melanoma, renal cell carcinoma, non-small-cell lung cancer, urothelial carcinoma, colorectal cancer, and Hodgkin's lymphoma. Though immune checkpoint inhibitors have revolutionized the treatment and prognosis of some advanced malignancies, they are also associated with a significant risk of immune-related adverse events. These adverse events can occur in any organ system, but gastrointestinal side effects are among the most commonly reported, with manifestations ranging from mild diarrhoea to severe colitis, sharing some features with inflammatory bowel disease. Anticipating a greater use of these drugs in the future, gastroenterologists should expect to be increasingly faced with gastrointestinal immune-related adverse events. Knowledge of these toxicities, as well as effective management algorithms, is essential to enable early diagnosis and treatment, decreasing morbidity and mortality. We reviewed the currently available literature on gastrointestinal toxicity induced by immune checkpoint inhibitors, namely the clinical features, diagnosis, and management.

Enterocolitis due to immune checkpoint inhibitors: a systematic review

Immune checkpoint inhibitors targeting cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) and programmed death-1 (PD-1)/ligand are increasingly used to treat several types of cancer. These drugs enhance antitumour T-cell activity and therefore induce immune-related adverse effects (irAE), of which gastrointestinal (GI) irAE are among the most frequent and severe. This systematic literature review summarises the clinical manifestations, management and pathophysiology of GI irAE due to immune checkpoint inhibitors. GI irAE induced by anti-CTLA-4 are frequent, potentially severe and resemble IBD, whereas those induced by PD-1 blockade seem to be less frequent and clinically more diverse. Baseline symbiotic gut microbiota is associated with an enhanced antitumour response to immune checkpoint inhibitors and an increased susceptibility to developing enterocolitis, in patients treated with anti-CTLA-4. These findings open new perspectives for possible manipulation of the gut microbiota in order to better identify responders to immune checkpoint inhibitors and to increase their efficacy and safety.

[Hepatic and digestive adverse events of immune checkpoint inhibitors (anti-CTLA-4 and, anti-PD-1/PD-L1): A clinico-pathological review]

Immune checkpoint inhibitors (anti-CTLA-4 and anti-PD-1/PD-L1) have recently revolutionized anti-cancer therapy and are nowadays used in different metastatic cancers. These treatments may induce immune-related adverse events which frequently involve the digestive tract and, to a less extent the liver. The tissular injuries, which are still poorly characterized from a morphological and physiopathological point of view, may lead on one side to the interruption of a life-saving treatment and on the other side to the development of severe complications, if not death. Therefore, it is crucial to diagnose as early as possible and treat these digestive and hepatic adverse effects in an optimal way. This article aims to describe the clinical and pathological presentations of digestive and hepatic adverse events induced by these immunotherapies.

Histopathological and immunophenotypic features of ipilimumab-associated colitis compared to ulcerative colitis

BACKGROUND

Use of the immune checkpoint inhibitor ipilimumab is sometimes complicated by ipilimumab-associated colitis (Ipi-AC), an immune-mediated colitis that mimics inflammatory bowel disease.

OBJECTIVE

We sought to characterize the histopathologic and immunophenotypic features of Ipi-AC and to directly compare these features to ulcerative colitis (UC).

METHODS

This is a retrospective cohort study of 22 patients with Ipi-AC, 12 patients with treatment-naïve UC and five controls with diarrhoea but normal endoscopic findings. Immunohistopathologic features were described, and quantitative immunohistochemistry (IHC) was performed for CD4, CD8, CD20, CD138 and FOXP3.

RESULTS

Endoscopic findings in both the Ipi-AC and UC groups included ulcerated, oedematous and erythematous mucosa. Involvement of the GI tract was more diffuse in Ipi-AC. As compared to UC, a smaller proportion of Ipi-AC biopsies had basal plasmacytosis (14% for Ipi-AC vs. 92% for UC, P < 0.0001) and crypt distortion (23% for Ipi-AC vs. 75% for UC, P = 0.003), whereas Ipi-AC biopsies had more apoptotic bodies in the left colon (17.6 ± 15.3 for Ipi-AC vs. 8.2 ± 4.2 for UC, P = 0.011). Cryptitis, ulcerations and crypt abscesses were common in both groups. Biopsy specimens from Ipi-AC had a lower density of CD20-positive lymphocytes than UC (275.8 ± 253.3 cells mm^-2 for Ipi-AC vs. 1173.3 ± 1158.2 cells mm^-2 for UC, P = 0.022) but had a similar density of CD4, CD8, CD138 and FOXP3-positive cells.

CONCLUSIONS

Ipi-AC is a distinct pathologic entity with notable clinical and histopathological differences compared to UC. These findings provide insights into the pathophysiology of immune-related adverse events (iAEs) from ipilimumab therapy.

Immune-related adverse events with immune checkpoint inhibitors in thoracic malignancies: focusing on non-small cell lung cancer patients

Immune checkpoint inhibitors (ICIs) have revolutionized treatment landscape among non-small cell lung cancer (NSCLC) patients in first- and second-line setting, and may become soon new treatment options in other thoracic malignancies such as small cell lung cancer (SCLC) or mesothelioma. The use of these drugs has indubitably changed the toxicity profile the oncologists are familiar with, and new spectra of immune-related adverse events are being reported with the widespread use of immunotherapies in solid tumors. Clinical management and understanding of immune-related adverse events is new and complex but expertise is still limited. In this review, we are summarizing the incidence and management of main side effects related to ICIs focusing on NSCLC patients.

Ipilimumab-induced acute generalized exanthematous pustulosis in a patient with metastatic melanoma

Ipilimumab is a new anti-cytotoxic T-lymphocyte antigen-4 monoclonal antibody that stimulates the immune response against melanoma. A 50-year-old man received ipilimumab for metastatic melanoma as part of a clinical trial. Two weeks after drug initiation, he developed a widespread oedematous erythema with sterile pustules. The histological examination showed subcorneal pustulosis formation with eosinophils. The clinical-pathological correlation was consistent with acute generalized exanthematous pustulosis. The symptoms resolved within 25 days after discontinuation of ipilimumab. We suspect that neutrophilic accumulation under the epidermis in this patient is a phenomenon similar to intraepithelial neutrophils aggregating on the surface epithelium over laminar propria in ipilimumab-induced colitis. To our knowledge, this is the first reported case of acute generalized exanthematous pustulosis associated with ipilimumab use in metastatic melanoma patients.

Anti-PD1-induced collagenous colitis in a melanoma patient

Targeted immunotherapy has markedly improved the survival of melanoma patients. We report the case of a melanoma patient who developed a collagenous colitis under an anti-PD1 regimen. A 68-year-old woman was treated for a stage IV melanoma. An anti-PD1, pembrolizumab, was introduced after the failure of a first-line therapy with an anti-CTLA4. At cycle 14, pembrolizumab was interrupted because of grade 3 diarrhea. Histologic analysis of colon mucosa showed a thickened apical subepithelial collagen layer with irregular collagen deposition of more than 25 µm thickness. Budesonide 9 mg/day and cholestyramin 8 g/day were then introduced, leading to a decrease in the number of stools to grade 2. Because of the prognosis of the disease, the efficacy of pembrolizumab in this patient and the lack of other efficient treatments, pembrolizumab was restarted, with no worsening of the diarrhea after a follow-up of 8 weeks. In the era of immunotherapy, a new type of drug-induced colitis has emerged because of monoclonal antibodies targeting immune checkpoints such as CTLA-4 and PD1. Gastrointestinal tract immune-mediated adverse effects are now well described with ipilimumab. To the best of our knowledge, this is the first report of a collagenous colitis in a patient treated with pembrolizumab, thus suggesting a new mechanism of toxicity. Classically, collagenous colitis first-line treatment is based on discontinuation of the suspected treatment. However, there may be a strong benefit to maintaining an anti-PD1 regimen in our patients. In this case, symptomatic management associated with budesonide and cholestyramin enabled continuation of pembrolizumab.

Immune checkpoint inhibitor colitis: the flip side of the wonder drugs

Immune checkpoint inhibitors block the co-inhibitory receptors on T cells to activate their cytotoxic immune function and are rapidly being explored for the treatment of various advanced-stage malignancies. These novel drugs have already significantly increased survival rates. The first available immune checkpoint inhibitors were cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors (such as ipilimumab), followed by programmed cell death protein 1 (PD-1) and programmed cell death protein ligand 1 (PD-L1) inhibitors (such as pembrolizumab and nivolumab). Anti-PD-1 and anti-PD-L1 therapies have demonstrated better efficacy and tolerability and less severe adverse effects compared to anti-CTLA-4 agents. Idelalisib, a PI3Kδ isoform inhibitor, is another immunotherapeutic agent that is often classified separately and is currently used in treatment of chronic lymphocytic leukemia and non-Hodgkin lymphomas. Despite successful therapeutic responses, immune-related adverse events have been reported with the use of these agents. The gastrointestinal side effects, particularly diarrhea, are among the most commonly reported symptoms. The histologic features of immune checkpoint inhibitor-associated colitis show a spectrum of patterns of injury among various drug classes. There is significant overlap between immune checkpoint inhibitor-associated colitis and other colitides, making the differential diagnosis difficult-especially in the absence of clinical history. The histopathology data on immune checkpoint inhibitor-associated colitis are limited. Here we review clinical features as well as various histologic patterns of colitis associated with these groups of medications.

Immune-related adverse events during anticancer immunotherapy: Pathogenesis and management

Immunotherapy is one of the most recent systemic treatments to emerge for use in oncology, and is based on the blocking of inhibitory immune checkpoints to potentiate the immune response to cancer. The anti-cytotoxic T lymphocyte-associated antigen-4 antibody ipilimumab and anti-programmed cell death protein 1 antibodies, including nivolumab and pembrolizumab, are currently available and widely used, and other immune-inhibiting antibodies are now under intensive investigation. These antibodies have shown efficacy in a growing number of tumor types, following initial observations of their notable effects in melanoma treatment. Despite the efficacy of these antibodies, their novel mechanisms of action are also associated with a new class of side effects called immune-related adverse events (IRAEs). These side effects do not share a common pathophysiology with other anticancer treatments and, therefore, they often require specific therapies. When detected early and correctly treated, IRAEs are reversible; however, they can become severe and life-threatening if underestimated or inappropriately treated. This review aims to revisit the pathogenesis of IRAEs, with attention to gastrointestinal manifestations, since these are common and potentially dangerous complications of immunotherapy and represent a major cause of treatment discontinuation. Recommendations and guidelines for the management of IRAEs are also presented, in order to provide a clear and applicable algorithm for use by clinicians.

Colon Immune-Related Adverse Events: Anti-CTLA-4 and Anti-PD-1 Blockade Induce Distinct Immunopathological Entities

BACKGROUND AND AIM

Immune checkpoint inhibitors targeting CTLA-4 and PD-1 improve survival in cancer patients but may induce immune-related adverse events, including colitis. The immunological characteristics of anti-CTLA-4 [αCTLA-4]- and anti-PD-1 [αPD-1]-related colitis have been poorly described. The aim of the present study was to compare the immunological and histological characteristics of αCTLA-4-induced colitis and αPD-1-induced colitis.

METHODS

Colonic biopsies from patients with αCTLA-4-induced colitis, αPD-1-induced colitis, and inflammatory bowel disease [IBD] were analysed by immunohistochemistry and flow cytometry. Tumour necrosis factor alpha [TNFα] concentration was assessed in biopsy supernatants.

RESULTS

CD8+ T cells were found in the lamina propria and epithelium in αPD-1-induced colitis, whereas CD4+ T cells were found in the lamina propria in αCTLA-4-induced colitis. No or low intraepithelial lymphocytes were observed in αCTLA-4-induced colitis. No difference in numbers of mucosal regulatory T cells was observed between αCTLA-4- or αPD-1-induced colitis and IBD patients. Higher numbers of activated ICOS+ conventional CD4+ T cells were observed in αCTLA-4-induced colitis compared with patients with IBD. Among ICOS+CD4+ T cells, conventional CD4+ T cells were the main T cell population in patents with αCTLA-4-induced colitis, whereas Treg cells were predominant in IBD or αPD-1-induced colitis. High mucosal TNFα concentrations were observed in αCTLA-4-induced colitis. Low mucosal TNFα concentrations were associated with steroid sensitivity.

CONCLUSIONS

These observations show that αCTLA-4- and αPD-1-induced colitis have distinct immunological characteristics. Mucosal TNFα concentration might detect patients at risk of developing corticosteroid resistance after CTLA-4 blockade.

Current Advances in Checkpoint Inhibitors: Lessons from Non-Central Nervous System Cancers and Potential for Glioblastoma

The adaptive immune system depends on the sequence of antigen presentation, activation, and then inhibition to mount a proportionate response to a threat. Tumors evade the immune response partly by suppressing T-cell activity using immune checkpoints. The use of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death 1 (PD-1), and programmed cell death ligand 1 (PD-L1) antibodies counteract this suppression, thereby enhancing the antitumor activity of the immune system. This approach has proven efficacy in melanoma, renal cancer, and lung cancer. There is growing evidence that the central nervous system is accessible to the immune system in the diseased state. Moreover, glioblastomas (GBMs) attract CTLA-4-expressing T-cells and express PD-L1, which inhibit activation and continuation of a cytotoxic T-cell response, respectively. This may contribute to the evasion of the host immune response by GBM. Trials are in progress to determine if checkpoint inhibitors will be of benefit in GBM. Radiotherapy could also be helpful in promoting inflammation, enhancing the immunogenicity of tumors, disrupting the blood–brain barrier and creating greater antigen release. The combination of radiotherapy and checkpoint inhibitors has been promising in preclinical trials but is yet to show efficacy in humans. In this review, we summarize the mechanism and current evidence for checkpoint inhibitors in gliomas and other solid tumors, examine the rationale of combining radiotherapy with checkpoint inhibitors, and discuss the potential benefits and pitfalls of this approach.