Mechanisms of checkpoint inhibition-induced adverse events

Immune checkpoint inhibition has revolutionized the treatment of several solid cancers, most notably melanoma and non-small-cell lung cancer (NSCLC). Drugs targeting cytotoxic T lymphocyte antigen (CTLA)-4 and programmed cell death 1 (PD-1) have made their way into routine clinical use; however, this has not been without difficulties. Stimulation of the immune system to target cancer has been found to result in a reduction of self-tolerance, leading to the development of adverse effects that resemble autoimmunity. These adverse effects are erratic in their onset and severity and can theoretically affect any organ type. Several mechanisms for immune-related toxicity have been investigated over recent years; however, no consensus on the cause or prediction of toxicity has been reached. This review seeks to examine reported evidence for possible mechanisms of toxicity, methods for prediction of those at risk and a discussion of future prospects within the field.     

免疫检查点抑制剂在肿瘤治疗中的应用进展

免疫检查点是人类进化出的控制免疫反应强度和持续时间、最大限度减少过度活跃的免疫应答导致的过度炎症反应和自身免疫性疾病的一种机制.相比于放疗、化疗等传统治疗手段,免疫疗法因其对正常细胞毒副作用小而在肿瘤治疗中日渐兴起.该疗法种类繁多,其中免疫检查点抑制疗法通过解除肿瘤免疫耐受、激活机体自身免疫系统进而清除肿瘤细胞,治疗手段极具潜力,成为肿瘤治疗中的研究热点.针对肿瘤免疫效应机制和逃逸机制进行了阐述,综述了抗细胞毒T淋巴细胞相关抗原4和程序性细胞死亡受体1两个免疫检查点抑制剂的作用机制和临床应用,对免疫检查点抑制剂的应用前景进行了展望.     

Cell intrinsic mechanisms of T-cell inhibition and application to cancer therapy

Summary: Establishing a balance between the rapid generation of effective immunity and the production of overly exuberant or excessively prolonged responses is critical to the maintenance of the equilibrium between health and disease. The preservation of homeostasis and prevention of inappropriate activation of immunity is safeguarded by systems integrating the influences of T-cell receptor signaling, pro-inflammatory danger signals, and positive costimulatory signals on the one hand with those of several layers of both cell-intrinsic and cell-extrinsic inhibitory checkpoints on the other. Evolution has thus provided an immunological system capable of clearance of pathogens and infected cells but which generally avoids the severe collateral damage that is associated with failure to control immunity. Central tolerance to self-antigens constitutes the first line of defense against self-destruction. Because central tolerance mechanisms fail to eliminate all self-reactive immune effector cells, other immune-regulating (peripheral tolerance) mechanisms are required to prevent excessive immune responses. Dysfunction of these inhibitory pathways in terms of reduced activity can result in the unmasking of self-directed responses and a variety of autoimmune morbidities. Conversely, enhanced inhibitory activity can restrict the generation of clinically useful immunity to cancers and to chronic infectious pathogens. This may manifest not only as inhibition of immunity directed towards what are largely aberrantly or overexpressed ‘self’ targets on malignant cells but also additional exaggeration of inhibitory pathway activity mediated via upregulation on tumor cells or stromal tissues of the ligands for inhibitory receptors expressed by lymphocytes. The selective pressures exerted by immuno-editing will favor the outgrowth of such immuno-evasive malignant clones. These pathways therefore represent significant hurdles to the generation of therapeutic anti-cancer responses. The most active of the T-cell intrinsic inhibitory pathways belong to the immunoglobulin superfamily, which occupies a central importance in the coordination of immune responses. The CD28/cytotoxic T-lymphocyte antigen-4 (CTLA-4):B7-1/B7-2 receptor/ligand grouping represents the archetypal example of these immune regulators. Therapies aimed at overcoming these mechanisms of peripheral tolerance, in particular by blocking the inhibitory checkpoints, offer the potential to generate anti-tumor activity, either as monotherapies or in synergism with other therapies that directly or indirectly enhance presentation of tumor epitopes to the immune system.     

Gaining ground on a cure through synergy: combining checkpoint inhibitors with cancer vaccines

Introduction: The approval of multiple checkpoint inhibitors (CPIs) for the treatment of advanced malignancies has sparked an explosion of research in the field of cancer immunotherapy. Despite the success of these medications, a large number of patients with advanced malignancy do not benefit from therapy. Early research indicates that a therapeutic combination of cancer vaccines with checkpoint inhibitors may lead to synergistic effects and higher response rates than monotherapy.

Areas covered: This paper summarizes the previously completed and ongoing research on this exciting combination, including the use of the tumor lysate, particle-loaded dendritic cell (TLPLDC) vaccine combined with checkpoint inhibitors in advanced melanoma.

Expert commentary: Increasing experience with CPIs has led to improved understanding of which patients may benefit and it is increasingly clear that the presence of a pre-existing immune response to the tumor, along with tumor-infiltrating lymphocytes, is key to the success of CPIs. One exciting possibility for the future is the addition of a cancer vaccine to CPI therapy, eliciting these crucial T cells, which can then be augmented and protected by the CPI. A number of current and future studies are addressing this very exciting combination therapy.     

Immune checkpoint inhibitors: The linchpins of modern immunotherapy

Immune checkpoint inhibitors (ICIs) have revolutionized our approach to cancer treatment in the past decade. While monoclonal antibodies to CTLA‐4 and PD‐1/PD‐L1 have produced remarkable and durable responses in a subset of patients, the majority of patients will still develop primary or adaptive resistance. With complex mechanisms of resistance limiting the efficacy of checkpoint inhibitor monotherapy, it is critical to develop combination approaches to allow more patients to benefit from immunotherapy. In this review, I approach the current landscape of ICI research from the perspective of sarcomas, a rare group of bone and soft tissue cancers that have had limited benefit from checkpoint inhibitor monotherapy, and little investigation of biomarkers to predict responses. By surveying the various mechanisms of resistance and treatment modalities being explored in other solid tumors, I outline how ICIs will undoubtedly serve as the critical foundation for future directions in modern immunotherapy.     

Immune checkpoint molecules in pregnancy: Focus on regulatory T cells

Regulatory T (Treg) cells are a specialized subpopulation of T cells that plays critical roles in the maintenance of immune homeostasis. Although efforts have been done, their role in human pregnancy is not fully understood. Numerous studies reported the presence of Treg cells throughout gestation by promoting maternal–fetal tolerance and fetal development. Furthermore, Treg population is heterogeneous as it is expressing different immune checkpoint molecules favoring immune suppressive function. Therefore, better understanding of the heterogeneity and function of Treg cells during pregnancy is critical for an effective immune intervention. Latest evidence has shown that several immune checkpoint molecules are closely associated with pregnancy outcome via multiple inhibitory mechanisms. Majority of these studies demonstrated the modulatory effects of immune checkpoint molecules on effector T-cell immunity, but their effects on Treg activation and function are still an enigma. In this review, we emphasize the potential influence of multiple immune checkpoint molecules, including CTLA-4, PD-1, Tim-3, LAG-3, and TIGIT, either in membrane or soluble form, on the function of decidual and peripheral Treg cells during pregnancy. Additionally, we discuss the promising future of targeting Treg cells via immune checkpoint molecules for pregnancy maintenance and prevention of complicated pregnancies.     

Tumor mutational burden assessed by targeted NGS predicts clinical benefit from immune checkpoint inhibitors in non-small cell lung cancer

In non-small cell lung cancer (NSCLC), immune checkpoint inhibitors (ICIs) significantly improve overall survival (OS). Tumor mutational burden (TMB) has emerged as a predictive biomarker for patients treated with ICIs. Here, we evaluated the predictive power of TMB measured by the Oncomine™ Tumor Mutational Load targeted sequencing assay in 76 NSCLC patients treated with ICIs. TMB was assessed retrospectively in 76 NSCLC patients receiving ICI therapy. Clinical data (RECIST 1.1) were collected and patients were classified as having either durable clinical benefit (DCB) or no durable benefit (NDB). Additionally, genetic alterations and PD-L1 expression were assessed and compared with TMB and response rate. TMB was significantly higher in patients with DCB than in patients with NDB (median TMB = 8.5 versus 6.0 mutations/Mb, Mann–Whitney p = 0.0244). 64% of patients with high TMB (cut-off = third tertile, TMB ≥ 9) were responders (DCB) compared to 33% and 29% of patients with intermediate and low TMB, respectively (cut-off = second and first tertile, TMB = 5–9 and TMB ≤ 4, respectively). TMB-high patients showed significantly longer progression-free survival (PFS) and OS (log-rank test p = 0.0014 for PFS and 0.0197 for OS). While identifying different subgroups of patients, combining PD-L1 expression and TMB increased the predictive power (from AUC 0.63 to AUC 0.65). Our results show that the TML panel is an effective tool to stratify patients for ICI treatment. A combination of biomarkers might maximize the predictive precision for patient stratification. Our study supports TMB evaluation through targeted NGS in NSCLC patient samples as a tool to predict response to ICI therapy. We offer recommendations for a reliable and cost-effective assessment of TMB in a routine diagnostic setting. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Autoimmune phenomena and disease in cancer patients treated with immune checkpoint inhibitors

The discovery and approved treatment with immune checkpoint inhibitors (ICIs) for a variety of cancers has changed dramatically the morbidity and mortality rates for these patients.Despite the obvious benefits, their use is associated with unique immune-related adverse effects (irAEs), including autoimmune conditions such as: inflammatory arthritis, myositis, vasculitis and Sicca syndrome.The appearance of ICIs-induced autoimmune irAE requires from oncologists and rheumatologists a different approach to the identification and treatment of these conditions, which may differ from the classic and traditional approach to rheumatologic diseases. It should be taken into consideration that ICIs therapy in patients with preexisting autoimmunity could be possible, but with a cost of causing disease exacerbation.In this extensive review, we present the autoimmune irAEs, mostly as phenomena, but also as classic autoimmune diseases as well as therapeutic options for the side effects.     

Negative regulators of T-cell activation: potential targets for therapeutic intervention in cancer, autoimmune disease, and persistent infections

Summary:  The generation of productive adaptive immune responses depends on the antigen-specific activation of T and B cells. The outcome of T-cell receptor engagement is influenced by signals from both positive and negative regulatory molecules that can either activate or inhibit T-cell function. CD28 and cytotoxic T-lymphocyte antigen-4 are the prototypical members of an immunoglobulin domain-containing protein family that play important roles in the control of T-cell responses against infection, cancer, and in autoimmune disease. Although the precise molecular details of their functions are still under active investigation, tumors and chronic pathogens seem to have exploited these pathways to achieve immune evasion. Furthermore, malfunction of the inhibitory arm of the immune response appears responsible for the development of multiple autoimmune pathologies. As a result, the negative regulators of T-cell activation have become attractive targets for therapeutic intervention in cancer, chronic infection, and autoimmune disease. The application of findings from basic research has provided insight into the manipulation of these pathways in the clinic and offers promising strategies for the treatment of disease.     

Immune checkpoints in central nervous system autoimmunity

A number of autoimmune diseases, including multiple sclerosis, are mediated by self-reactive T cells that have escaped the deletional mechanisms of central tolerance. Usually, these T cells are kept at bay through peripheral tolerance mechanisms, including regulation through coinhibitory receptors and suppression by regulatory T cells. However, if these mechanisms fail, self-reactive T cells are activated and autoimmune responses ensue. This review outlines how the coinhibitory receptors CTLA-4 (cytotoxic T-lymphocyte antigen-4), PD-1 (programed death-1), Tim-3 (T-cell immunoglobulin- and mucin domain-containing molecule 3), and TIGIT (T-cell immunoreceptor with immunoglobulin and ITIM domains) act at different checkpoints to inhibit autoreactive T cells and suppress the development of central nervous system autoimmunity. Loss of each of these receptors predisposes to autoimmunity, indicating a non-redundant role in maintaining peripheral tolerance. At the same time, their functional patterns seem to overlap to a large degree. Therefore, we propose that only the concerted action of a combination of inhibitory receptors is able to maintain peripheral tolerance and prevent autoimmunity.     

Combined anti-PD-1 and anti-CTLA-4 checkpoint blockade: Treatment of melanoma and immune mechanisms of action

Cytotoxic T-lymphocyte associated protein-4 (CTLA-4) and the Programmed Death Receptor 1 (PD-1) are immune checkpoint molecules that are well-established targets of antibody immunotherapies for the management of malignant melanoma. The monoclonal antibodies, Ipilimumab, Pembrolizumab, and Nivolumab, designed to interfere with T cell inhibitory signals to activate immune responses against tumors, were originally approved as monotherapy. Treatment with a combination of immune checkpoint inhibitors may improve outcomes compared to monotherapy in certain patient groups and these clinical benefits may be derived from unique immune mechanisms of action. However, treatment with checkpoint inhibitor combinations also present significant clinical challenges and increased rates of immune-related adverse events. In this review, we discuss the potential mechanisms attributed to single and combined checkpoint inhibitor immunotherapies and clinical experience with their use.     

Harnessing the immune system for the treatment of melanoma: current status and future prospects

When malignant melanoma is diagnosed early, surgical resection is the intervention of choice and is often curative, but many patients present with unresectable disease at later stages. Due to its complex etiology paired with well-documented chemoresistance and high metastatic potential, patients with advanced melanoma had a poor prognosis, and the treatment of this disease remained unsatisfactory for many years. Recently, targeted therapy, immune checkpoint inhibition, or combinatory approaches have revolutionized the therapeutic options of melanoma allowing considerable improvement in disease control and survival. In this review we will summarize these novel therapeutic strategies with particular focus on combinatory immunotherapies and further discuss recent data derived from immunogenomic studies and potential options to improve the therapeutic efficacy of immune modulatory approaches.     

PD-1单克隆抗体瘤内用药对小鼠肺癌疗效的影响

目的探索PD-1单克隆抗体瘤内用药对小鼠肺癌的治疗作用,旨在寻找更安全、有效的免疫治疗方案。方法将皮下荷瘤成功的C57BL/6J肺癌小鼠随机分为5组:尾静脉注射生理盐水组(intravenous injection,IV)、瘤内注射生理盐水组(intratumoral injection,IT)、尾静脉注射PD-1单抗组(IV 10 mg/kg)、瘤内注射PD-1单抗组(IT 10 mg/kg)、瘤内注射PD-1单抗剂量减半组(IT 5 mg/kg),分析各组小鼠的生存率和小鼠荷瘤生长情况;运用流式细胞术分析CD8⁺T细胞/CD4⁺T细胞比例,使用免疫组织化学分析各组小鼠荷瘤组织CD45、Ki67的表达,并对上述数据进行统计学分析。结果瘤内注射PD-1单抗可显著抑制小鼠肺癌组织的生长、延长小鼠生存时间,且瘤内组织Ki67表达下调,CD45表达、CD8⁺T细胞/CD4⁺T细胞免疫细胞比例增加。结论瘤内注射组小鼠荷瘤组织生长速度明显受抑、肿瘤细胞增殖指数和生存时间显著降低,提示瘤内注射PD-1单抗对小鼠肺癌的发展进程具有抑制作用,此创新式的治疗方法将为临床治疗肿瘤提供新的思路和策略。     

Immunotherapies based on PD-1/PD-L1 pathway inhibitors in ovarian cancer treatment

Immunotherapies based on anti-programmed death 1/programmed death ligand 1 (PD-1/PD-L1) pathway inhibitors may turn out effective in ovarian cancer (OC) treatment. They can be used in combination with standard therapy and are especially promising in recurrent and platinum-resistant OC. There is growing evidence that the mechanism of the PD-1/PD-L1 pathway can be specific for a particular histological cancer type. Interestingly, the data have shown that the PD-1/PD-L1 pathway blockade may be effective, especially in the endometrioid type of OC. It is important to identify the cause of anti-tumor immune response suppression and exclude its other mechanisms in OC patients. It is also necessary to conduct subsequent studies to confirm in which OC cases the treatment is effective and how to select patients and combine drugs to improve patient survival.     

抑制性受体对淋巴细胞活化的调节作用

淋巴细胞在接受正向活化信号的同时也接受各种抑制性信号的调节,以维持机体正常的稳态,避免免疫应答过度对机体的病理损坏。调节淋巴细胞活化的抑制性受体主要包括3类:识别MHC分子的抑制性受体、抑制性Fc受体及与B7家族成员结合的抑制性受体,系统地了解其种类、配体、作用机制、与疾病的关系等将为人们进一步深入了解免疫应答的调控机制提供参考。     

Immune checkpoint inhibitors: new strategies to checkmate cancer

Immune checkpoint inhibitors (ICIs) targeting cytotoxic T lymphocyte‐associated protein‐4 (CTLA‐4) or programmed cell death protein 1 (PD‐1) receptors have demonstrated remarkable efficacy in subsets of patients with malignant disease. This emerging treatment modality holds great promise for future cancer treatment and has engaged pharmaceutical research interests in tumour immunology. While ICIs can induce rapid and durable responses in some patients, identifying predictive factors for effective clinical responses has proved challenging. This review summarizes the mechanisms of action of ICIs and outlines important preclinical work that contributed to their development. We explore clinical data that has led to disease‐specific drug licensing, and highlight key clinical trials that have revealed ICI efficacy across a range of malignancies. We describe how ICIs have been used as part of combination therapies, and explore their future prospects in this area. We conclude by discussing the incorporation of these new immunotherapeutics into precision approaches to cancer therapy.     

Rheumatic immune related adverse events in patients treated with checkpoint inhibitors for immunotherapy of cancer

Immune checkpoints are small molecules expressed by immune cells that play critical roles in maintaining immune homeostasis. Immune checkpoint inhibitors (ICPIs) are new cancer drugs that target self-tolerance pathways exploited by tumors to escape immune destruction, such as cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed cell death 1 (PD-1) or its ligand (PD-L1). Several ICPIs have been approved by Food and Drug Administration, increasing overall survival with different cancers. However, their use can determine development of many different inflammatory side effects, that are defined immune-related adverse effects (irAEs); among others, rheumatological irAEs can develop in these patients. Currently, we have limited data about these adverse effects; particularly, few evidence come from clinical trials about patients with pre-existing autoimmune diseases because they were excluded from them. Therefore we analysed the existing scientific literature dealing with this issue, in order to answer to different clinical questions. According to all reviewed data, rheumatological irAEs are not infrequent, in both previously diseased and undiseased patients, but they are often mild and reversible. Close monitoring and interdisciplinary management and monitoring is necessary in order to ensure best care. Many questions remain unanswered or not completely answered; further data are necessary to implement our knowledge in this field and to standardize and optimize clinical practice.