Checkpoint Blockade Toxicity and Immune Homeostasis in the Gastrointestinal Tract

Broadening the Impact of Immunotherapy to Pancreatic Cancer: Challenges and Opportunities

Pancreatic ductal adenocarcinoma (PDAC) is projected to become the second deadliest cancer in the United States by 2025, with 5-year survival at less than 10%. In other recalcitrant cancers, immunotherapy has shown unprecedented response rates, including durable remissions after drug discontinuation. However, responses to immunotherapy in PDAC are rare. Accumulating evidence in mice and humans suggests that this remarkable resistance is linked to the complex, dueling role of the immune system in simultaneously promoting and restraining PDAC. In this review, we highlight the rationale that supports pursuing immunotherapy in PDAC, outline the key barriers that limit immunotherapy efficacy, and summarize the primary preclinical and clinical efforts to sensitize PDAC to immunotherapy.

Adverse Events Following Cancer Immunotherapy: Obstacles and Opportunities

Oncology has recently undergone a revolutionary change with widespread adoption of immunotherapy for many cancers. Immunotherapy using monoclonal antibodies against checkpoint molecules, including programmed death (PD)-1, PD ligand (PD-L)1, and cytotoxic T lymphocyte-associated antigen (CTLA)-4, is effective in a significant subset of patients. However, immune-related adverse events (irAEs) have emerged as frequent complications of checkpoint blockade, likely due to the physiological role of checkpoint pathways in regulating adaptive immunity and preventing autoimmunity. As immunotherapy becomes more common, a better understanding of the etiology of irAEs and ways to limit these events is needed. At the same time, studying these new therapy-related disorders provides an opportunity to better understand naturally occurring human autoimmune and inflammatory disorders, with the potential to improve therapies for cancer and autoimmune diseases.

Combination regimens with PD-1/PD-L1 immune checkpoint inhibitors for gastrointestinal malignancies

Gastrointestinal (GI) malignant neoplasms have a high global incidence and treatment prospects for patients with advanced GI tumors are dismal. PD-1/PD-L1 inhibitors emerged as a frontline treatment for several types of cancer. However, the shortcomings of PD-1/PD-L1 inhibitors have been observed, including low objective response rates and acquired tumor resistance, especially in patients receiving PD-1/PD-L1 inhibitors as a single treatment. Accumulating evidence from clinical trials increasingly suggests that combined immunotherapies enhance therapeutic responses in patients with malignances, especially for GI tumors which have a complex matrix, and significant molecular and immunological differences. Preclinical and clinical studies suggest there are advantages to combined immunological regimens, which represents the next logical step in this field, although further research is necessary. This literature review explores the current limitations of monotherapies, before critically discussing the rationale behind combination regimens. Then, we provide a summary of the clinical applications for gastrointestinal cancers.

Checkpoint inhibitor-associated autoimmunity

Checkpoint inhibitors (CI) have revolutionized the management of many cancers but can result in immune-related adverse events (IRAE). In this chapter, we review the clinical manifestations and management of the most common IRAE, plus less common IRAE, such as inflammatory arthritis, of particular interest to rheumatologists. We review the mechanism of action of CI, predictors of IRAE, and the impact of IRAE on cancer outcomes. The study of IRAE is in its infancy; there are very few prospective studies and virtually no treatment trials. Where possible, we have drawn estimates of IRAE incidence from meta-analyses of randomized controlled trials. Clinical descriptions are derived from case series and case reports. Readers are encouraged to refer to consensus guidelines for IRAE management published by the American Society of Clinical Oncology and the Society for Immunotherapy of Cancer.

Early introduction of selective immunosuppressive therapy associated with favorable clinical outcomes in patients with immune checkpoint inhibitor-induced colitis

BACKGROUND

Current treatment guidelines for immune-mediated colitis (IMC) recommend 4 to 6 weeks of steroids as first-line therapy, followed by selective immunosuppressive therapy (SIT) (infliximab or vedolizumab) in patients who do not respond to steroids. We assessed the effect of early SIT introduction and number of SIT infusions on clinical outcomes.

METHODS

We performed a retrospective review of patients with IMC who received SIT at The University of Texas MD Anderson Cancer Center between January and December 2018. Logistic regression analyses were used to assess associations between clinical outcomes and features of IMC.

RESULTS

Of the 1459 patients who received immune checkpoint inhibitors, 179 developed IMC of any grade; 84 of these 179 patients received SIT. Of the 84 patients who received SIT, 79% were males, and the mean age was 60 years (standard deviation, 14). Compared with patients who received SIT > 10 days after IMC onset, patients who received early SIT (≤10 days) required fewer hospitalizations (P = 0.03), experienced steroid taper failure less frequently (P = 0.03), had fewer steroid tapering attempts (P < 0.01), had a shorter course of steroid treatment (P = 0.09), and had a shorter duration of symptoms (P < 0.01). Patients who received one or two infusions of SIT achieved histologic remission less frequently (P = 0.09) and had higher fecal calprotectin levels after SIT (P = 0.01) compared with patients who received three or more infusions. Risk factors for IMC recurrence after weaning off steroids included: 1) needing multiple hospitalizations, 2) experiencing steroid taper failure after SIT, 3) receiving infliximab rather than vedolizumab, 4) receiving fewer than three infusions of SIT, 5) having higher fecal calprotectin levels after SIT, and 6) receiving a longer course of steroids, hospitalization and IMC symptoms. Unsuccessful weaning from steroids after SIT was associated with high IMC grades; multiple hospitalizations; steroid-resistant IMC; long interval from IMC to SIT initiation; and long duration of steroids, IMC symptoms, and hospitalization.

CONCLUSION

SIT should be introduced early in the disease course of IMC instead of waiting until failure of steroid therapy or steroid taper. Patients who received three or more infusions of SIT had more favorable clinical outcomes.

Cancer Immunotherapy: Beyond Checkpoint Blockade

Blocking antibodies to the immune checkpoint receptors or their ligands have revolutionized the treatment of diverse malignancies. Many tumors are recognized by adaptive immunity, but these adaptive responses can be inhibited by immunosuppressive mechanisms within the tumor, often through pathways outside of the currently targeted checkpoints. For this reason, only a minority of cancer patients achieve durable responses to current immunotherapies. Multiple novel approaches strive to expand immunotherapy's reach. These may include targeting alternative immune checkpoints. However, many investigational strategies look beyond checkpoint blockade. These include cellular therapies to bypass endogenous immunity and efforts to stimulate new adaptive antitumor responses using vaccines, adjuvants, and combinations with cytotoxic therapy, as well as strategies to inhibit innate immune suppression and modulate metabolism within the tumor microenvironment. The challenge for immunotherapy going forward will be to select rational strategies for overcoming barriers to effective antitumor responses from the myriad possible targets.

Antitumor response to microscopic melanoma in the gastric mucosa mimicking ipilimumab-induced gastritis

BACKGROUND

Alongside its clinical success, checkpoint blockade has also given rise to a set of immune-related adverse events (irAEs). In addition to causing considerable morbidity and even mortality, irAEs may limit the success and scope of immunotherapy. Most irAEs arise at mucosal barriers, including the gastrointestinal mucosa, leading most commonly to colitis, though both gastritis and enteritis can result from checkpoint blockade. While guidelines generally recommend confirmatory testing for suspected severe irAEs, the role of endoscopy in diagnosing more moderate irAEs is less clear. Many patients with suspected gastrointestinal irAEs are treated empirically with glucocorticoids based on typical symptoms. Although efficient, this approach may miss less common underlying etiologies, and may expose patients unnecessarily to an increased risk of infection, and a potentially dampened antitumor response.

CASE PRESENTATION

We report a case of ipilimumab-induced antitumor immunity targeting microscopic gastric melanoma metastases, mimicking checkpoint blockade induced gastritis. Immune suppression was avoided and the immunotherapy was continued.

CONCLUSION

Checkpoint blockade can induce rapid inflammatory responses to tumor tissue present throughout the body. These responses are desirable, but may also lead to local tissue injury, causing symptoms that may mimic adverse events. This is particularly important to consider in organs where metastatic disease may be unappreciated at the time of treatment, and where irAEs are otherwise common, such as the gastrointestinal tract. In this setting, empiric immune suppression may inhibit antitumor responses, improving symptoms but at a potential cost to therapeutic efficacy.

A systematic review of adverse events in randomized trials assessing immune checkpoint inhibitors

The advent of immune checkpoint-inhibitors (CPI) has transformed treatment for several cancer types. This review was performed to assess the rate of adverse events (AEs) associated with the use of CPI, alone or in combinations. A review of AEs reporting quality was also performed. All publications of Randomized Clinical Trials (RCTs) assessing CPI published before December 2017 were included. To investigate the quality of AEs reporting, a set of items was defined based on the 2004 CONSORT harms extension statement. Rates of Grade 5, serious, and study-withdrawal related AEs were collected in each treatment category. Specific immune related AEs (irAEs) were also collected when available. Pooled estimates of adverse event rates were calculated by using generalized linear mixed model. A total of 35 RCTs including 16,485 patients were included. The overall quality of AEs reporting was satisfactory, but items pertaining to methods of data collection and analysis were infrequently reported. Grade ≥ 3 AEs were reported for 14% (95% CI 12-16) of patients treated with PD(L)-1 inhibitors, 34% (95% CI 27-42) of patients treated with CTLA-4 inhibitors, 55% (95% CI 51-59) of patients on CPI combinations and 46% (95% CI 40-53) of patients on immunotherapy-chemotherapy combination. The profile of irAEs was different among the treatment categories. The use of CPI, especially in combination, is associated with significant rates of Grade ≥ 3 AEs. Healthcare planning should anticipate the expected high number of patients presenting with irAEs in the future.

Importance of endoscopic and histological evaluation in the management of immune checkpoint inhibitor-induced colitis

BACKGROUND

Immune checkpoint inhibitors (ICPI) are efficacious treatments for advanced malignancies but can result in immune mediated diarrhea and colitis (IDC). Currently, the guidelines for the treatment of IDC depend only on clinical symptoms. Endoscopic and histologic features of such adverse events are not well studied in a manner that can help to gauge treatment plans. We aimed to characterize endoscopic and histologic features of IDC and to assess their association with clinical outcomes.

METHODS

Our study included patients who had undergone endoscopy for IDC (1/2010 to 3/2018). Patients with GI infection at time of onset were excluded. High-risk endoscopic features were ulcers deeper than 2 mm, larger than 1 cm, and extensive colonic involvement. Univariate and multivariate logistic regression were performed to assess the association of endoscopic and histological features with clinical outcomes.

RESULTS

A total of 182 patients was included; most were white (92%), males (65%) with a mean age of 60 years. Median time from ICPI initiation to IDC was 7 weeks. Fifty-three percent had grade 3-4 diarrhea, and 32% grade 3-4 colitis. Forty-nine patients had mucosal ulcerations, 66 non-ulcerative inflammation and 67 normal endoscopy. Calprotectin was higher in patients with ulceration (P = 0.04). The sensitivity of lactoferrin to detect histologic and endoscopic inflammation was 90% and 70% respectively. Patients who underwent endoscopy earlier than 7 days after IDC onset had shorter duration of IDC symptoms and duration of steroid treatment than those who underwent endoscopy after 7 days of IDC onset (P = 0.026 and P = 0.053, respectively). Patients who underwent endoscopy > 30 days of symptom onset required longer duration of steroids (P = 0.02), had more recurrent symptoms (P < 0.01) and received later infliximab/vedolizumab add-on therapy than did those who underwent endoscopy ≤30 days (P = 0.03). High-risk features were associated with more frequent (P = 0.03) and longer duration (P = 0.02) hospitalization and infliximab/vedolizumab requirement (P < 0.01). Patients with active histological inflammation had more recurrence (P < 0.01) and repeat endoscopy (P < 0.01). Repeat endoscopy was required in 47 patients. A multivariate logistic regression revealed that longer ICPI treatment was associated with more frequent hospitalizations (OR 1.00; 95%CI 1.00-1.01; P < 0.01) and high-risk endoscopic features were associated with the requirement of infliximab/vedolizumab (OR 3.89; 95%CI 1.68-9.01; P < 0.01).

CONCLUSION

High risk endoscopic features and active histologic inflammation represent important markers of disease severity with clinical implications and should be used in a timely manner to devise IDC-focused treatment algorithms.

On the Road to Immunotherapy-Prospects for Treating Head and Neck Cancers With Checkpoint Inhibitor Antibodies

Head and neck cancers (HNC) represent a heterogeneous cluster of aggressive malignancies that account for 3% of all cancer cases in the UK. HNC is increasing in frequency particularly in the developing world, which is related to changes in risk factors. Unfortunately, the mortality rate is high, which is chiefly attributed to late diagnosis at stages where traditional treatments fail. Cancer immunotherapy has achieved great successes in anti-tumor therapy. Checkpoint inhibitor (CI) antibodies enhance anti-tumor activity by blocking inhibitory receptors to drive tumor-specific T and NK cell effector responses. Since their introduction in 2011, CI antibodies have been approved for many cancer types including HNC. Here, we examine the development of CI therapies and look forward to future developments for treatment of HNC with CI therapies.

Radiation and Local Anti-CD40 Generate an Effective in situ Vaccine in Preclinical Models of Pancreatic Cancer

Radiation therapy induces immunogenic cell death, which can theoretically stimulate T cell priming and induction of tumor-specific memory T cell responses, serving as an in situ vaccine. In practice, this abscopal effect is rarely observed. We use two mouse models of pancreatic cancer to show that a single dose of stereotactic body radiation therapy (SBRT) synergizes with intratumoral injection of agonistic anti-CD40, resulting in regression of non-treated contralateral tumors and formation of long-term immunologic memory. Long-term survival was not observed when mice received multiple fractions of SBRT, or when TGFβ blockade was combined with SBRT. SBRT and anti-CD40 was so effective at augmenting T cell priming, that memory CD8 T cell responses to both tumor and self-antigens were induced, resulting in vitiligo in long-term survivors.

Immune Checkpoint Immunotherapy for Non-Small Cell Lung Cancer: Benefits and Pulmonary Toxicities

Immune checkpoint inhibitors (ICIs) are newer, immunotherapy-based drugs that have been shown to improve survival in advanced non-small cell lung cancer (NSCLC). Unlike traditional chemotherapeutic agents, ICIs work by boosting the body's natural tumor killing response. However, this unique mechanism of action has also led to the recognition of class-specific side effects. Labeled immune-related adverse events, these toxicities can affect multiple organ systems including the lungs. Immune-mediated lung injury because of ICI use, termed checkpoint inhibitor pneumonitis (CIP), occurs in about 3% to 5% of patients receiving ICIs; however, the real-world incidence of this entity may be higher, especially now that ICIs are being used in nonclinical trial settings. In this review, we briefly introduce the biology of ICIs and the indications for ICI use in NSCLC and then discuss the epidemiology and clinical and radiologic manifestations of CIP. Next, we discuss management strategies for CIP, including the current consensus on management of steroid-refractory CIP. Given the nascent nature of this field, we highlight areas of uncertainty and emerging research questions in the burgeoning field of checkpoint inhibitor pulmonary toxicity.

Diagnosis and Management of Hepatitis in Patients on Checkpoint Blockade

Many human tumors are recognized by the adaptive immune system, but these spontaneous antitumor responses are typically inadequate to mediate regression. Blockade of immune regulatory "checkpoint" receptors such as cytotoxic T-lymphocyte-associated antigen 4 and programmed cell death 1 can unleash antitumor immunity, resulting in tumor responses that can be durable. Alongside the enormous promise of immunotherapy for cancer, the immune dysregulation of checkpoint blockade has led to a plethora of new autoimmune adverse events. Hepatic toxicity occurs in 1%-17% of patients on immune checkpoint inhibitors, with the precise incidence dependent on both the drug used and the underlying malignancy. Hepatitis is most commonly a low-grade toxicity, but grade 3 and 4 hepatotoxicity does occur. Here we will answer frequently asked questions regarding immune-related hepatitis to assist in the recognition and management of this important condition.

KEY POINTS

Immune related hepatitis is a potentially serious complication of checkpoint blockade.The differential for elevated liver function tests in patients on checkpoint blockade is broad.Diagnostic testing such as viral serologies, liver ultrasound, cross sectional imaging, and liver biopsy may help in the diagnosis of immune related hepatitis in select patients.Patients with underlying cirrhosis are an at risk population for whom current grading criteria may underestimate the severity of liver inflammation.Severe immune related hepatitis is best managed by a multi-disciplinary team that includes a hepatologist.Most patients with immune related hepatitis respond to corticosteroids, but a substantial fraction require treatment with a secondary immunosuppressive agent.

Biomarkers for predicting efficacy of PD-1/PD-L1 inhibitors

Programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) is a negative modulatory signaling pathway for activation of T cell. It is acknowledged that PD-1/PD-L1 axis plays a crucial role in the progression of tumor by altering status of immune surveillance. As one of the most promising immune therapy strategies, PD-1/PD-L1 inhibitor is a breakthrough for the therapy of some refractory tumors. However, response rate of PD-1/PD-L1 inhibitors in overall patients is unsatisfactory, which limits the application in clinical practice. Therefore, biomarkers which could effectively predict the efficacy of PD-1/PD-L1 inhibitors are crucial for patient selection. Biomarkers reflecting tumor immune microenvironment and tumor cell intrinsic features, such as PD-L1 expression, density of tumor infiltrating lymphocyte (TIL), tumor mutational burden, and mismatch-repair (MMR) deficiency, have been noticed to associate with treatment effect of anti-PD-1/anti-PD-L1 therapy. Furthermore, gut microbiota, circulating biomarkers, and patient previous history have been found as valuable predictors as well. Therefore establishing a comprehensive assessment framework involving multiple biomarkers would be meaningful to interrogate tumor immune landscape and select sensitive patients.

Anti-CTLA-4 therapy requires an Fc domain for efficacy

Ipilimumab, an antibody that recognizes cytotoxic T lymphocyte antigen (CTLA)-4, was the first approved “checkpoint”-blocking anticancer therapy. In mice, the response to antibodies against CTLA-4 depends entirely on expression of the Fcγ receptor. We developed H11, an alpaca heavy chain-only antibody fragment against CTLA-4 that lacks an Fc portion and inhibits interactions between CTLA-4 and its ligand. By using H11 to visualize CTLA-4 expression in the whole animal, we found that accessible CTLA-4 is largely confined to the tumor; however, H11 treatment has minimal effects on antitumor responses. Installing the murine IgG2a constant region on H11 greatly enhances antitumor response. We were thus able to dissociate CTLA-4 blockade from CTLA-4–dependent receptor engagement as an explanation for the antitumor effect.

Ipilimumab, a monoclonal antibody that recognizes cytotoxic T lymphocyte antigen (CTLA)-4, was the first approved “checkpoint”-blocking anticancer therapy. In mouse tumor models, the response to antibodies against CTLA-4 depends entirely on expression of the Fcγ receptor (FcγR), which may facilitate antibody-dependent cellular phagocytosis, but the contribution of simple CTLA-4 blockade remains unknown. To understand the role of CTLA-4 blockade in the complete absence of Fc-dependent functions, we developed H11, a high-affinity alpaca heavy chain-only antibody fragment (VHH) against CTLA-4. The VHH H11 lacks an Fc portion, binds monovalently to CTLA-4, and inhibits interactions between CTLA-4 and its ligand by occluding the ligand-binding motif on CTLA-4 as shown crystallographically. We used H11 to visualize CTLA-4 expression in vivo using whole-animal immuno-PET, finding that surface-accessible CTLA-4 is largely confined to the tumor microenvironment. Despite this, H11-mediated CTLA-4 blockade has minimal effects on antitumor responses. Installation of the murine IgG2a constant region on H11 dramatically enhances its antitumor response. Coadministration of the monovalent H11 VHH blocks the efficacy of a full-sized therapeutic antibody. We were thus able to demonstrate that CTLA-4–binding antibodies require an Fc domain for antitumor effect.