CTLA-4 blockade following relapse of malignancy after allogeneic stem cell transplantation is associated with T cell activation but not with increased levels of T regulatory cells

The Immunotherapy of Acute Myeloid Leukemia: A Clinical Point of View

The potential of the immune system to eradicate leukemic cells has been consistently demonstrated by the Graft vs. Leukemia effect occurring after allo-HSCT and in the context of donor leukocyte infusions. Various immunotherapeutic approaches, ranging from the use of antibodies, antibody-drug conjugates, bispecific T-cell engagers, chimeric antigen receptor (CAR) T-cells, and therapeutic infusions of NK cells, are thus currently being tested with promising, yet conflicting, results. This review will concentrate on various types of immunotherapies in preclinical and clinical development, from the point of view of a clinical hematologist. The most promising therapies for clinical translation are the use of bispecific T-cell engagers and CAR-T cells aimed at lineage-restricted antigens, where overall responses (ORR) ranging from 20 to 40% can be achieved in a small series of heavily pretreated patients affected by refractory or relapsing leukemia. Toxicity consists mainly in the occurrence of cytokine-release syndrome, which is mostly manageable with step-up dosing, the early use of cytokine-blocking agents and corticosteroids, and myelosuppression. Various cytokine-enhanced natural killer products are also being tested, mainly as allogeneic off-the-shelf therapies, with a good tolerability profile and promising results (ORR: 20-37.5% in small trials). The in vivo activation of T lymphocytes and NK cells via the inhibition of their immune checkpoints also yielded interesting, yet limited, results (ORR: 33-59%) but with an increased risk of severe Graft vs. Host disease in transplanted patients. Therefore, there are still several hurdles to overcome before the widespread clinical use of these novel compounds.

Navigating the Immune Maze: Pioneering Strategies for Unshackling Cancer Immunotherapy Resistance

Cancer immunotherapy has ushered in a transformative era in oncology, offering unprecedented promise and opportunities. Despite its remarkable breakthroughs, the field continues to grapple with the persistent challenge of treatment resistance. This resistance not only undermines the widespread efficacy of these pioneering treatments, but also underscores the pressing need for further research. Our exploration into the intricate realm of cancer immunotherapy resistance reveals various mechanisms at play, from primary and secondary resistance to the significant impact of genetic and epigenetic factors, as well as the crucial role of the tumor microenvironment (TME). Furthermore, we stress the importance of devising innovative strategies to counteract this resistance, such as employing combination therapies, tailoring immune checkpoints, and implementing real-time monitoring. By championing these state-of-the-art methods, we anticipate a paradigm that blends personalized healthcare with improved treatment options and is firmly committed to patient welfare. Through a comprehensive and multifaceted approach, we strive to tackle the challenges of resistance, aspiring to elevate cancer immunotherapy as a beacon of hope for patients around the world.

Research Progress on Molecular Subtyping and Modern Treatment of Triple-Negative Breast Cancer

Breast cancer has become the most common malignant tumor worldwide. Triple-negative breast cancer (TNBC) is a type of breast cancer that is negative for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Compared with other molecular subtypes of breast cancer, TNBC is the most aggressive and highly heterogeneous. TNBC is insensitive to endocrine and anti-HER2 therapy, and chemotherapy is currently the main systemic treatment. With the continuous development of detection techniques and deepening research on TNBC molecular subtypes, drugs targeting immune checkpoints and different targets have emerged, such as atezolizumab, pembrolizumab, poly (ADP-ribose) polymerase (PARP) inhibitors, trophoblast cell-surface antigen 2 (TROP-2), and antibody-drug conjugates. These therapies provide new hope for TNBC treatment. Based on the analysis and classification of TNBC, this article summarizes the immunotherapy, targeted therapy, and new treatment combinations, providing references for the precise treatment of TNBC in the future.

Modeling the interaction between donor-derived regulatory T cells and effector T cells early after allogeneic hematopoietic stem cell transplantation

While allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potential curative therapy against hematological malignancies, modulation of donor T cell alloreactivity is required to enhance the graft-versus-leukemia (GVL) effect and control graft-versus-host-disease (GVHD) after allo-HSCT. Donor-derived regulatory CD4⁺CD25⁺Foxp3⁺ T cells (Tregs) play a central role in establishing of immune tolerance after allo-HSCT. They could be a key target to be modulated for increasing the GVL effect and control of GVHD. We constructed an ordinary differential equation model incorporating bidirectional interactions between Tregs and effector CD4⁺ T cells (Teffs) as a mechanism for control of Treg cell concentration. The goal is to elucidate how the interaction between Tregs and Teffs is modulated in order to get insights into fine tuning of alloreactivity after allo-HSCT. The model was calibrated with respect to published Treg and Teff recovery data after allo-HSCT. The calibrated model exhibits perfect or near-perfect adaptation to stepwise perturbations between Treg and Teff interactions, as seen in Treg cell populations when patients with relapsed malignancy were treated with anti-CTLA-4 (cytotoxic T lymphocyte-associated antigen 4). In addition, the model predicts observed shifts of Tregs and Teffs concentrations after co-stimulatory receptor IL-2R or TNFR2 blockade with allo-HSCT. The present results suggest simultaneous blockades of co-stimulatory and co-inhibitory receptors as a potential treatment for enhancing the GVL effect after allo-HSCT without developing GVHD.

In or out of control: Modulating regulatory T cell homeostasis and function with immune checkpoint pathways

Regulatory T cells (Tregs) are the master regulators of immunity and they have been implicated in different disease states such as infection, autoimmunity and cancer. Since their discovery, many studies have focused on understanding Treg development, differentiation, and function. While there are many players in the generation and function of truly suppressive Tregs, the role of checkpoint pathways in these processes have been studied extensively. In this paper, we systematically review the role of different checkpoint pathways in Treg homeostasis and function. We describe how co-stimulatory and co-inhibitory pathways modulate Treg homeostasis and function and highlight data from mouse and human studies. Multiple checkpoint pathways are being targeted in cancer and autoimmunity; therefore, we share insights from the clinic and discuss the effect of experimental and approved therapeutics on Treg biology.

The prognostic and therapeutic potentials of CTLA-4 in hematological malignancies

INTRODUCTION

Hematological Malignancies (HMs) are a group of progressive, difficult-to-treat, and highly recurrent diseases. A suppressed phenotype of the immune system is present in HMs and growing evidence indicates the role of Cytotoxic T lymphocyte-Associated protein 4 (CTLA-4) in the course of HMs.

AREAS COVERED

This article reviews the recent literature on the role of CTLA-4 in different subtypes of HMs. Here, the studies on the expression pattern, its effect on the prognosis of different HMs, and polymorphisms of CTLA-4 have been elaborated. Finally, the effect of targeting CTLA-4 in vitro and in vivo, as well as in clinical trials, is discussed.

EXPERT OPINION

According to the recent literature, CTLA-4 is overexpressed in different HMs, which is correlated with poor survival, while it is associated with better a prognosis in Chronic Lymphocytic Leukemia (CLL). Targeting CTLA-4 in Acute Myeloid Leukemia (AML), Sezary Syndrome (SS), Hodgkin's Lymphoma (HL), and so on, is helpful. While this is not recommended and may even be harmful in multiple myeloma (MM) and CLL. Also, it seems that certain CTLA-4 gene polymorphisms are efficient factors in the course of HMs. Future studies may broaden our knowledge regarding the role of CTLA-4 in HMs.

Modern Immunotherapy in the Treatment of Triple-Negative Breast Cancer

Simple Summary

This review summarizes reports from the latest clinical trials assessing the safety and clinical effectiveness of new biological drugs stimulating the immune system to fight cancer. The aim of this study is to show the enormous therapeutic potential of monoclonal antibodies in the treatment of cancer, in particular triple negative breast cancer (TNBC). Introduction of these innovative drugs to the standard clinical cancer therapies, including TNBC, allows for an increase in the response rate to the applied treatment, and consequently extending the lives of patients suffering from cancer. We hope to draw attention to the extremely difficult-to-treat TNBC, as well as the importance of the development of clinical trials evaluating drugs modulating the immune system in TNBC therapy.

Abstract

Triple-Negative Breast Cancer is a subtype of breast cancer characterized by the lack of expression of estrogen receptors, progesterone receptors, as well as human epidermal growth factor receptor 2. This cancer accounts for 15–20% of all breast cancers and is especially common in patients under 40 years of age, as well as with the occurring BRCA1 mutation. Its poor prognosis is reflected in the statistical life expectancy of 8–15 months after diagnosis of metastatic TNBC. So far, the lack of targeted therapy has narrowed therapeutic possibilities to classic chemotherapy. The idea behind the use of humanized monoclonal antibodies, as inhibitors of immunosuppressive checkpoints used by the tumor to escape from immune system control, is to reduce immunotolerance and direct an intensified anti-tumor immune response. An abundance of recent studies has provided numerous pieces of evidence about the safety and clinical benefits of immunotherapy using humanized monoclonal antibodies in the fight against many types of cancer, including TNBC. In particular, phase three clinical trials, such as the IMpassion 130, the KEYNOTE-355 and the KEYNOTE-522 resulted in the approval of immunotherapeutic agents, such as atezolizumab and pembrolizumab by the US Food and Drug Administration in TNBC therapy. This review aims to present the huge potential of immunotherapy using monoclonal antibodies directed against immunosuppressive checkpoints—such as atezolizumab, avelumab, durvalumab, pembrolizumab, nivolumab, cemiplimab, tremelimumab, ipilimumab—in the fight against difficult to treat TNBCs as monotherapy as well as in more advanced combination strategies.

Post-hematopoietic stem cell transplantation relapse: Role of checkpoint inhibitors

Background and Aims

Despite the revolutionary effects of hematopoietic stem cell transplantation (HSCT) in treating hematological malignancies, post-HSCT relapse is considered a critical concern of clinicians. Residual malignant cells employ many mechanisms to evade immune surveillance and survive to cause relapse after transplantation. One of the immune-frustrating mechanisms through which malignant cells can compromise the antitumor effects is misusing the self-limiting system of immune response by overexpressing inhibitory molecules to interact with the immune cells, leading them to so-called "exhausted" and ineffective. Introduction of these molecules, known as immune checkpoints, and blocking them was a prodigious step to decrease the relapses.

Methods

Using keywords nivolumab, pembrolizumab, and ipilimumab, we investigated the literature to figure out the role of the immune checkpoints in the HSCT setting. Studies in which these agents were administrated for relapse after transplantation were reviewed. Factors such as the interval from the transplant to relapse, previous treatment history, adverse events, and the patients' outcome were extracted.

Results

Here we provided a mini-review discussing the experiences of three immune checkpoints, including nivolumab, pembrolizumab, and ipilimumab, as well as the pros and cons of using their blockers in relapse control after HSCT. In conclusion, it seems that CI therapy seems effective for this population. Future investigations may provide detailed outlook of this curative options.

Prognostic and therapeutic role of tumor-infiltrating lymphocyte subtypes in breast cancer

Increased levels of total tumor-infiltrating lymphocytes (TILs) are generally associated with good prognosis in several breast cancer subtypes. Subtypes of TILs impact both tumor cells and immune cells in a variety of different ways, leading to either a pro-tumor or antitumor effect. Tumor-infiltrating CD8+ T cells and natural killer (NK) cells perform as effector cells against tumor cells and are associated with better clinical outcome. Immunotherapy approaches that improve the antitumor activity and proliferation of CD8+ T and NK cells include PD-1/PD-L1 blockade, CAR T cell therapy, or ex vivo-stimulated NK cells. A subset of CD8+ T cells, tissue-resident memory T cells, has also recently been associated with good prognosis in breast cancer patients, and has potential to serve as a predictive biomarker and therapeutic target. Tumor-infiltrating B cells also secrete apoptosis-inducing IgG antibodies and can act as antigen-presenting cells to prime CD4+ and CD8+ T cells. On the other hand, regulatory T and regulatory B cells modulate the immune response from CD8+ T cells and NK cells by secreting immunosuppressive cytokines and inhibiting maturation of antigen-presenting cells (APCs). These regulatory cells are typically associated with poor prognosis, therefore rendering suppression of their regulatory function a key immunotherapeutic strategy.

The Role of Immune Checkpoint Molecules for Relapse After Allogeneic Hematopoietic Cell Transplantation

Immune checkpoint molecules represent physiological brakes of the immune system that are essential for the maintenance of immune homeostasis and prevention of autoimmunity. By inhibiting these negative regulators of the immune response, immune checkpoint blockade can increase anti-tumor immunity, but has been primarily successful in solid cancer therapy and Hodgkin lymphoma so far. Allogeneic hematopoietic cell transplantation (allo-HCT) is a well-established cellular immunotherapy option with the potential to cure hematological cancers, but relapse remains a major obstacle. Relapse after allo-HCT is mainly thought to be attributable to loss of the graft-versus-leukemia (GVL) effect and hence escape of tumor cells from the allogeneic immune response. One potential mechanism of immune escape from the GVL effect is the inhibition of allogeneic T cells via engagement of inhibitory receptors on their surface including PD-1, CTLA-4, TIM3, and others. This review provides an overview of current evidence for a role of immune checkpoint molecules for relapse and its treatment after allo-HCT, as well as discussion of the immune mediated side effect graft-vs.-host disease. We discuss the expression of different immune checkpoint molecules on leukemia cells and T cells in patients undergoing allo-HCT. Furthermore, we review mechanistic insights gained from preclinical studies and summarize clinical trials assessing immune checkpoint blockade for relapse after allo-HCT.

Nanoencapsulated rituximab mediates superior cellular immunity against metastatic B-cell lymphoma in a complement competent humanized mouse model

BACKGROUND

Despite the numerous applications of monoclonal antibodies (mAbs) in cancer therapeutics, animal models available to test the therapeutic efficacy of new mAbs are limited. NOD.Cg-Prkdc^scid Il2rg ^tm1Wjl /SzJ (NSG) mice are one of the most highly immunodeficient strains and are universally used as a model for testing cancer-targeting mAbs. However, this strain lacks several factors necessary to fully support antibody-mediated effector functions-including antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity (CDC)-due to the absence of immune cells as well as a mutation in the Hc gene, which is needed for a functional complement system.

METHODS

We have developed a humanized mouse model using a novel NSG strain, NOD.Cg^-Hc1 Prkdc^scid Il2rgtm1Wjl/SzJ (NSG^-Hc1), which contains the corrected mutation in the Hc gene to support CDC in addition to other mechanisms endowed by humanization. With this model, we reevaluated the anticancer efficacies of nanoencapsulated rituximab after xenograft of the human Burkitt lymphoma cell line 2F7-BR44.

RESULTS

As expected, xenografted humanized NSG^-Hc1 mice supported superior lymphoma clearance of native rituximab compared with the parental NSG strain. Nanoencapsulated rituximab with CXCL13 conjugation as a targeting ligand for lymphomas further enhanced antilymphoma activity in NSG^-Hc1 mice and, more importantly, mediated antilymphoma cellular responses.

CONCLUSIONS

These results indicate that NSG^-Hc1 mice can serve as a feasible model for both studying antitumor treatment using cancer targeting as well as understanding induction mechanisms of antitumor cellular immune response.

Checkpoint inhibition to prevent or treat relapse in allogeneic hematopoietic cell transplantation

In the past decades, survival has improved after allogeneic hematopoietic cell transplantation (allo-HCT) due largely to advances in the prevention of graft-vs.-host disease (GVHD) and opportunistic infection. However, few inroads have been made into the problem of leukemia relapse which is the primary reason for failure of allo-HCT. The graft-vs.-leukemia (GVL) response, in which engrafted immunocompetent donor immune cells can eliminate leukemia cells, is acknowledged as the foundation upon which the curative potential of allo-HCT is based. Despite our strongly held faith in its existence, we remain unable to define GVL on a mechanistic level. T cells, in part, mediate GVL though the roles of specific T cell subsets, NK cells, B cells, macrophages remain elusive. A higher frequency of marrow-infiltrating T cells expressing PD-1, CTLA-4, and TIM-3 and other immune checkpoints have been observed in relapsed patients compared to those in remission. Studies have described the association of T cells expressing an exhausted phenotype with response to immune manipulation post-HCT. In light of these observations and the well documented activity of immune checkpoint blockade (CPB) in transplant naïve patients with hematologic malignancies, considerable interest has developed in evaluating strategies incorporating CPB to address relapse post-HCT. While checkpoint inhibitors may be provocative agents to test, they also raise concern for potential induction of GVHD and uncontrollable immune breakthrough events. This review will lay the framework upon which CPB is being utilized post-HCT, describe early clinical results, and lay out future directions.

The FLAMSA concept-past and future

The FLAMSA reduced intensity (RIC) concept, also known as "sequential therapy", is a conceptual platform for the treatment of leukemia separated in several parts: induction therapy, a sequence of antileukemic and immunosuppressive conditioning for allogeneic stem cell transplantation, and immune restitution supported by donor lymphocyte transfusions. The antileukemic part consists of fludarabine, cytosine arabinoside, and amsacrine (FLAMSA); non-cross reactive agents like fludarabine and amsacrine have been successfully used in cases of refractoriness and relapse. Immunosuppressive conditioning and transplantation follow after only 3 days of rest. This way, the toxicity of allogeneic transplantation could be reduced and the anti-leukemia effects by using allogeneic immune cells could be optimized. This review summarizes available data on efficacy and toxicity of this approach. Further, possible strategies for improvements are discussed in order to provide better chances for elderly and frail patients and patients with advanced and high-risk disease. Among others, several new agents are available that target molecular changes of leukemia for induction of remission and allow for bridging the time after transplantation until adoptive immunotherapy becomes safe and effective.

Dawn of Monitoring Regulatory T Cells in (Pre-)clinical Studies: Their Relevance Is Slowly Recognised

Regulatory T cells (Tregs) have a prominent role in the control of immune homeostasis. Pharmacological impact on their activity or balance with effector T cells could contribute to (impaired) clinical responses or adverse events. Monitoring treatment-related effects on T cell subsets may therefore be part of (pre-)clinical studies for medicinal products. However, the extent of immune monitoring performed in studies for marketing authorisation and the degree of correspondence with data available in the public domain is not known. We evaluated the presence of T cell immunomonitoring in 46 registration dossiers of monoclonal antibodies indicated for immune-related disorders and published scientific papers. We found that the depth of Treg analysis in registration dossiers was rather small. Nevertheless, data on treatment-related Treg effects are available in public academia-driven studies (post-registration) and suggest that Tregs may act as a biomarker for clinical responses. However, public data are fragmented and obtained with heterogeneity of experimental approaches from a diversity of species and tissues. To reveal the potential added value of T cell (and particular Treg) evaluation in (pre-)clinical studies, more cell-specific data should be acquired, at least for medicinal products with an immunomodulatory mechanism. Therefore, extensive analysis of T cell subset contribution to clinical responses and the relevance of treatment-induced changes in their levels is needed. Preferably, industry and academia should work together to obtain these data in a standardised manner and to enrich our knowledge about T cell activity in disease pathogenesis and therapies. This will ultimately elucidate the necessity of T cell subset monitoring in the therapeutic benefit-risk assessment.

Immunotherapy for acute myeloid leukemia: from allogeneic stem cell transplant to novel therapeutics

Immunotherapy in the form of allogeneic stem cell transplantation (SCT) plays an instrumental role in the treatment of acute myeloid leukemia (AML), with non-transplant modalities of immunotherapy including checkpoint blockade now being actively explored. Here, we provide an overview of the graft versus leukemia (GVL) effect in AML as a window into understanding the prospects of AML immunotherapy. We explore the roles of various cell types in orchestrating anti-leukemic immunity, as well as those contributing to the unique immune suppressive state of myeloid diseases. We discuss specific approaches to engage the immune system, while noting the challenges of the AML antigen landscape and the barriers to immune modulation. We review the potential for immunomodulatory agents in combination with cellular therapies, donor lymphocyte infusion, and following SCT. Finally, to address the challenge of minimal residual disease (MRD) following chemotherapy, we propose combination epigenetic and immunotherapy for the eradication of MRD.

Targeting Leukemia Stem Cell-Niche Dynamics: A New Challenge in AML Treatment

One of the most urgent needs in AML is to improve the disease cure rate as relapse still occurs in 60–80% of patients. Recent evidence suggests that dismal clinical outcomes may be improved by a better definition of the tight interaction between the AML cell population and the bone marrow (BM) microenvironment (“the niche”); the latter has been progressively highlighted to have an active role in the disease process. It has now been well established that the leukemic population may misinterpret niche-derived signals and remodel the niche, providing a shelter to AML cells and protecting them from the cytotoxic effects of chemoradiotherapy. Novel imaging technological advances and preclinical disease models have revealed that, due to the finite number of BM niches, leukemic stem cells (LSCs) and normal hematopoietic stem cells (HSCs) compete for the same functional areas. Thus, the removal of LSCs from the BM niche and the promotion of normal HSC engraftment should be the primary goals in antileukemic research. In addition, it is now becoming increasingly clear that AML-niche dynamics are disease stage specific. In AML, the niche has been linked to disease pathogenesis in the preleukemic stage, the niche becomes permissive once leukemic cells are established, and the niche is transformed into a self-reinforcing structure at a later disease stage. These concepts have been fostered by the demonstration that, in unrelated AML types, endosteal vessel loss occurs as a primary AML-induced niche alteration, and additional AML-induced alterations of the niche and normal hematopoiesis evolve focally and in parallel. Obviously, this endosteal vessel loss plays a fundamental role in AML pathogenesis by causing excessive vascular permeability, hypoxia, altered perfusion, and reduced drug delivery. Each of these alterations may be effectively targeted by various therapeutic procedures, but preservation of endosteal vessel integrity might be the best option for any future antileukemic treatment.

Natural Killer Immunotherapy for Minimal Residual Disease Eradication Following Allogeneic Hematopoietic Stem Cell Transplantation in Acute Myeloid Leukemia

The most common cause of death in patients with acute myeloid leukemia (AML) who receive allogeneic hematopoietic stem cell transplantation (allo-HSCT) is AML relapse. Therefore, additive therapies post allo-HSCT have significant potential to prevent relapse. Natural killer (NK)-cell-based immunotherapies can be incorporated into the therapeutic armamentarium for the eradication of AML cells post allo-HSCT. In recent studies, NK cell-based immunotherapies, the use of adoptive NK cells, NK cells in combination with cytokines, immune checkpoint inhibitors, bispecific and trispecific killer cell engagers, and chimeric antigen receptor-engineered NK cells have all shown antitumor activity in AML patients. In this review, we will discuss the current strategies with these NK cell-based immunotherapies as possible therapies to cure AML patients post allo-HSCT. Additionally, we will discuss various means of immune escape in order to further understand the mechanism of NK cell-based immunotherapies against AML.

Mechanisms of immune escape after allogeneic hematopoietic cell transplantation

Relapse of the original disease is a major cause of death after allogeneic hematopoietic cell transplantation for acute leukemias. There is growing evidence that relapses may be explained not only by resistance to chemotherapy but also by the escape of tumor cells from the control of the allogeneic immune response. Mechanisms of immune evasion can involve abrogation of leukemia cell recognition due to loss of HLA genes, immunosuppression by immune-checkpoint ligand expression, production of anti-inflammatory factors, release of metabolically active enzymes, loss of proinflammatory cytokine production, and acquisition of novel driver mutations that promote leukemia outgrowth. These mechanisms, and therapeutic targeting of immune escape, will be discussed. We divide the evidence in support of immune-escape mechanisms into animal studies, human laboratory studies, and human clinical experience. A better understanding of the molecular pathways connected to immune escape and relapse may help to improve our therapeutic armamentarium against acute myeloid leukemia relapse.

Significant Risk of Graft-versus-Host Disease with Exposure to Checkpoint Inhibitors before and after Allogeneic Transplantation

Investigators are using checkpoint inhibitors (CPIs) to treat aggressive hematologic malignancies in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) and in some patients with relapsed disease after allo-HSCT. CTLA-4 inhibitors and PD-1 inhibitors are 2 main types of CPIs, which work through activation of the immune system. On one hand, CPIs can achieve graft-versus-tumor effect, and on the other hand, there is a risk of graft-versus-host disease (GVHD). After a comprehensive literature review, we included data (n = 283) from 24 studies (11 original manuscripts and 13 case reports or case series) and evaluated the results to assess the safety and efficacy of CPI use in conjunction with allo-HSCT. Among the 283 patients, 107 received CPI before allo-HSCT, and 176 received CPI after allo-HSCT. The most common indication for CPI use was for Hodgkin lymphoma. The CPIs used in various studies included ipilimumab, nivolumab, and pembrolizumab. Among the patients exposed to CPI before allo-HSCT, 56% developed acute GVHD and 29% developed chronic GVHD. Investigators reported 20 deaths, 60% of which were GVHD-related. The overall mortality risk with GVHD is 11%. In this group, investigators noted an objective response rate (ORR) in 68% of patients, with complete remission (CR) in 47%, partial remission (PR) in 21%, and stable disease in 11%. Among the patients who received a CPI after allo-HSCT for disease relapse, 14% developed acute GVHD and 9% developed chronic GVHD. Investigators reported 40 deaths, 28% of which were GVHD-related. The mortality risk with GVHD is approximately 7%. Investigators reported ORR in 54% of patients, with CR in 33%, PR in 21%, and disease stabilization in 5%. After careful evaluation of collective data, we found that CPI use both before and after allo-HSCT can be highly effective, but exposure can lead to a significantly increased risk of GVHD-related morbidity and mortality in this patient population. Despite limited availability of data, there is need for extreme caution while making decisions regarding the use of CPIs. Detailed discussions and prospective well-designed clinical trials are needed to explore this issue further.

Biomarkers for checkpoint inhibition in hematologic malignancies

In the past few years we have seen remarkable paradigm shifts in the treatment of many solid tumors due to the introduction of inhibitors targeting immune checkpoints such as PD-1/PD-L1 and CTLA-4. Recent results indicate that checkpoint inhibition also represents a very promising approach for certain types of hematologic malignancies. Unfortunately, treatment with checkpoint inhibitors is also associated with substantial toxicities and high costs and only a subset of patients appears to derive clinical benefit from these treatments. This demonstrates the urgent need for biomarkers for the identification of patient populations that are likely to respond to this type of therapy and/or have fewer side effects. Here, we have reviewed available information on the prognostic and predictive value of biomarkers for anti-CTLA-4 and anti-PD-1/PD-L1 as the most commonly used checkpoint inhibitors. There are currently no reliable biomarkers capable of predicting responses to anti-CTLA-4 agents, such as ipilimumab, in hematologic malignancies. Certain polymorphisms in the CTLA-4 gene, however, seem to have an impact on the patients' outcome, especially in the case of chronic lymphocytic leukemia (CLL). There is now sufficient data supporting PD-L1 expression levels in the tumor tissue as an independent prognostic factor in B cell lymphomas such as diffuse large B-cell lymphoma (DLBCL). Overexpression of PD-L1 in the tumor tissue and elevated serum levels of soluble PD-L1 may also represent adverse prognostic factors in certain subtypes of T cell lymphomas. Finally, expression levels of PD-L1 also seem to predict responses to anti-PD-1/PD-L1 approaches in patients with Hodgkin lymphoma. Future studies will have to further delineate the prognostic/predictive role of PD-L1 expression as a biomarker in hematologic malignancies and may be able to identify confounding variables, which will hopefully to some extent be generalizable to other types of anti-tumor immunotherapies.

Regulatory T cells in acute and chronic kidney diseases

Foxp3-expressing CD4+ regulatory T cells (Tregs) make up one subset of the helper T cells (Th) and are one of the major mechanisms of peripheral tolerance. Tregs prevent abnormal activation of the immune system throughout the lifespan, thus protecting from autoimmune and inflammatory diseases. Recent studies have elucidated the role of Tregs beyond autoimmunity. Tregs play important functions in controlling not only innate and adaptive immune cell activation, but also regulate nonimmune cell function during insults and injury. Inflammation contributes to a multitude of acute and chronic diseases affecting the kidneys. This review examines the role of Tregs in pathogenesis of renal inflammatory diseases and explores the approaches for enhancing Tregs for prevention and therapy of renal inflammation.

Immune checkpoint molecules in acute myeloid leukaemia: managing the double-edged sword

New immunotherapeutic interventions have revolutionized cancer treatment. The immune responsiveness of acute myeloid leukaemia (AML) was first demonstrated by allogeneic stem cell transplantation. In addition, milder immunotherapeutic approaches are exploited. However, the long-term efficacy of these therapies is hampered by various immune resistance and editing mechanisms. In this regard, co-inhibitory signalling pathways have been shown to play a crucial role. Via up-regulation of inhibitory checkpoints, tumour-reactive T cell and Natural Killer cell responses can be strongly impeded. Accordingly, the introduction of checkpoint inhibitors targeting CTLA-4 (CTLA4) and PD-1 (PDCD1, CD279)/PD-L1 (CD274, PDCD1LG1) accomplished a breakthrough in cancer treatment, with impressive clinical responses. Numerous new co-inhibitory players and novel combination therapies are currently investigated for their potential to boost anti-tumour immunity and improve survival of cancer patients. Although the challenge here remains to avoid severe systemic toxicity. This review addresses the involvement of co-inhibitory signalling in AML immune evasion and discusses the opportunities for checkpoint blockers in AML treatment.

Ipilimumab plus Lenalidomide after Allogeneic and Autologous Stem Cell Transplantation for Patients with Lymphoid Malignancies

Purpose: Prevention or treatment of relapsed lymphoid malignancies after hematopoietic stem cell transplantation (HSCT) requires novel strategies. We hypothesized that antitumor-cell responses could be enhanced by the addition of lenalidomide to the cytotoxic T-lymphocyte-associated protein 4 inhibitor ipilimumab.Experimental Design: We conducted a phase II investigator-initiated trial to assess the safety and activity of ipilimumab and lenalidomide in patients with lymphoid malignancies that relapsed after allogeneic HSCT and in high-risk patients after autologous HSCT. Patients received 10 mg of oral lenalidomide daily for 21 days followed by intravenous ipilimumab at 3 mg/kg bodyweight. The regimen was repeated 4 weeks later for a total of four treatments.Results: We enrolled 17 patients (10 allogeneic and seven autologous transplant recipients). Immune-mediated toxicity was limited to one patient with asymptomatic hypothyroidism and one with dermatitis in the allogeneic and autologous groups, respectively. One allogeneic transplant recipient had a flare of prior GVHD while taking lenalidomide that precluded further treatment. All others finished treatment without GVHD. Four of 10 patients in the allogeneic group had complete responses (three of which were durable at 19+, 21+, and 32+ months), and three had partial responses. The disease in six of seven patients in the autologous group remains in remission. The groups had similar immune responses, including a two- to threefold increase in inducible ICOS⁺CD4⁺FoxP3^- T-cell number.Conclusions: Our early-phase data suggested that ipilimumab plus lenalidomide is well tolerated after HSCT. Adverse events did not differ significantly between the allogeneic and autologous groups. Clin Cancer Res; 24(5); 1011-8. ©2017 AACR.

Inflammatory Orbitopathy Associated With Ipilimumab

In this case report, the clinical presentation of an inflammatory orbitopathy seen following treatment with ipilimumab is described. After 3 rounds of ipilimumab (10 mg/kg) treatment for Stage III metastatic melanoma, the subject of this case report developed acute eye pain and proptosis. At initial presentation, she had marked proptosis and diffuse severe ophthalmoparesis. After treatment with high-dose steroids, over a period of 6 months, the symptoms gradually resolved fully. Although the condition may mimic thyroid-associated orbitopathy, imaging and laboratory features suggest that the orbitopathy associated with ipilimumab is not a secondary effect of thyroid dysfunction but a distinct inflammatory condition. The authors conclude that immune-related side effects can occur with biologic agents used to treat malignancies and these side-effects can involve the eye. This case illustrates the occurrence of an inflammatory orbitopathy associated with ipilimumab treatment.

Immunomodulatory Drugs: Immune Checkpoint Agents in Acute Leukemia

Intrinsic immune responses to acute leukemia are inhibited by a variety of mechanisms, such as aberrant antigen expression by leukemia cells, secretion of immunosuppressive cytokines and expression of inhibitory enzymes in the tumor microenvironment, expansion of immunoregulatory cells, and activation of immune checkpoint pathways, all leading to T cell dysfunction and/or exhaustion. Leukemic cells, similar to other tumor cells, hijack these inhibitory pathways to evade immune recognition and destruction by cytotoxic T lymphocytes. Thus, blockade of immune checkpoints has emerged as a highly promising approach to augment innate anti-tumor immunity in order to treat malignancies. Most evidence for the clinical efficacy of this immunotherapeutic strategy has been seen in patients with metastatic melanoma, where anti-CTLA-4 and anti-PD-1 antibodies have recently revolutionized treatment of this lethal disease with otherwise limited treatment options. To meet the high demand for new treatment strategies in acute leukemia, clinical testing of these promising therapies is commencing. Herein, we review the biology of multiple inhibitory checkpoints (including CTLA-4, PD-1, TIM-3, LAG-3, BTLA, and CD200R) and their contribution to immune evasion by acute leukemias. In addition, we discuss the current state of preclinical and clinical studies of immune checkpoint inhibition in acute leukemia, which seek to harness the body's own immune system to fight leukemic cells.

Prognostic Model to Predict Post-Autologous Stem-Cell Transplantation Outcomes in Classical Hodgkin Lymphoma

Purpose Our aim was to capture the biology of classical Hodgkin lymphoma (cHL) at the time of relapse and discover novel and robust biomarkers that predict outcomes after autologous stem-cell transplantation (ASCT). Materials and Methods We performed digital gene expression profiling on a cohort of 245 formalin-fixed, paraffin-embedded tumor specimens from 174 patients with cHL, including 71 with biopsies taken at both primary diagnosis and relapse, to investigate temporal gene expression differences and associations with post-ASCT outcomes. Relapse biopsies from a training cohort of 65 patients were used to build a gene expression-based prognostic model of post-ASCT outcomes (RHL30), and two independent cohorts were used for validation. Results Gene expression profiling revealed that 24% of patients exhibited poorly correlated expression patterns between their biopsies taken at initial diagnosis and relapse, indicating biologic divergence. Comparative analysis of the prognostic power of gene expression measurements in primary versus relapse specimens demonstrated that the biology captured at the time of relapse contained superior properties for post-ASCT outcome prediction. We developed RHL30, using relapse specimens, which identified a subset of high-risk patients with inferior post-ASCT outcomes in two independent external validation cohorts. The prognostic power of RHL30 was independent of reported clinical prognostic markers (both at initial diagnosis and at relapse) and microenvironmental components as assessed by immunohistochemistry. Conclusion We have developed and validated a novel clinically applicable prognostic assay that at the time of first relapse identifies patients with unfavorable post-ASCT outcomes. Moving forward, it will be critical to evaluate the clinical use of RHL30 in the context of positron emission tomography-guided response assessment and the evolving cHL treatment landscape.

Wilms tumor 1 peptide vaccination after hematopoietic stem cell transplant in leukemia patients

Although the prognosis of leukemia patients after allogeneic hematopoietic stem cell transplantation (HSCT) has greatly improved, relapse is still a major cause of death after HSCT. Cancer vaccines may have the potential to enhance the graft-versus-leukemia (GVL) effect. The post-allogeneic HSCT period provides a unique platform for vaccination, because (I) tumor burden is minimal, (II) lymphopenia allows for rapid expansion of cytotoxic T cells (CTLs), (III) donor-derived CTLs are not exhausted, (IV) inflammation is caused by alloreactions, and (V) the abundance of regulatory T cells is low due to their late recovery. Tumor cell lysates, dendritic cells (DCs), and peptides derived from leukemia-associated antigens (LAAs) have been used as vaccines. Clinical trials with several types of vaccines for post-HSCT patients revealed that the vaccination induced an immunological response and might benefit patients with minimal residual disease; however, the efficacy of this approach must be examined in randomized studies. In addition, it is important to consider the combination of cancer vaccine with checkpoint antibodies, recently shown to be useful in treating leukemia relapse after HSCT.

Checkpoint Inhibition: Programmed Cell Death 1 and Programmed Cell Death 1 Ligand Inhibitors in Hodgkin Lymphoma

Hodgkin lymphoma (HL) is a lymphoid malignancy characterized by a reactive immune infiltrate surrounding relatively few malignant cells. In this scenario, active immune evasion seems to play a central role in allowing tumor progression. Immune checkpoint inhibitor pathways are normal mechanisms of T-cell regulation that suppress immune effector function following an antigenic challenge. Hodgkin lymphoma cells are able to escape immune surveillance by co-opting these mechanisms. The programmed cell death 1 (PD-1) pathway in particular is exploited in HL as the malignant Hodgkin and Reed-Sternberg cells express on their surface cognate ligands (PD-L1/L2) for the PD-1 receptor and thereby dampen the T-cell-mediated antitumoral response. Monoclonal antibodies that interact with and disrupt the PD-1:PD-L1/L2 axis have now been developed and tested in early-phase clinical trials in patients with advanced HL with encouraging results. The remarkable clinical activity of PD-1 inhibitors in HL highlights the importance of immune checkpoint pathways as therapeutic targets in HL. In this review, we discuss the rationale for targeting PD-1 and PD-L1 in the treatment of HL. We will evaluate the published clinical data on the different agents and highlight the safety profile of this class of agents. We discuss the available evidence on the use of biomarkers as predictors of response to checkpoint blockade and summarize the areas under active investigation in the use of PD-1/PD-L1 inhibitors for the treatment of HL.

Programmed death-1 immune checkpoint blockade in the treatment of hematological malignancies

The use of tumor-specific monoclonal antibodies (MAbs) has revolutionize the field of cancer immunotherapy. Although treatment of malignant diseases with MAbs is promising, many patients fail to respond or relapse after an initial response. Both solid tumors and hematological malignancies develop mechanisms that enable them to evade the host immune system by usurping immune checkpoint pathways such as PD-1, PD-2, PDL-1, or PDL-2 (programmed cell death protein-1 or 2 and PD-Ligand 1 or 2), which are expressed on activated T cells and on T-regulatory, B cells, natural killers, monocytes, and dendritic cells. One of the most exciting anticancer development in recent years has been the immune checkpoint blockade therapy by using MAbs against immune checkpoint receptor and/or ligands. Anti-PD1 antibodies have been tested in clinical studies that included patients with hematological malignancies and showed remarkable efficacy in Hodgkin lymphoma (HL). In our review, we will focus on the effect of PD-1 activation on hematological malignancies and its role as a therapeutic target. Key messages The programmed death 1 (PD1) immune checkpoint is an important homeostatic mechanism of the immune system that helps in preventing autoimmunity and uncontrolled inflammation in cases of chronic infections. However, PD1 pathway is also operated by a wide variety of malignancies and represents one of the most important mechanisms by which tumor cells escape from the surveillance of the immune system. Blocking of immune checkpoints by the use of monoclonal antibodies opened a new era in the field of cancer immunotherapy. Results from clinical trials are promising, and currently, this approach has been proven effective and safe in patients with solid tumors and hematological malignancies.

Ipilimumab for Patients with Relapse after Allogeneic Transplantation

BACKGROUND

Loss of donor-mediated immune antitumor activity after allogeneic hematopoietic stem-cell transplantation (HSCT) permits relapse of hematologic cancers. We hypothesized that immune checkpoint blockade established by targeting cytotoxic T-lymphocyte-associated protein 4 with ipilimumab could restore antitumor reactivity through a graft-versus-tumor effect.

METHODS

We conducted a phase 1/1b multicenter, investigator-initiated study to determine the safety and efficacy of ipilimumab in patients with relapsed hematologic cancer after allogeneic HSCT. Patients received induction therapy with ipilimumab at a dose of 3 or 10 mg per kilogram of body weight every 3 weeks for a total of 4 doses, with additional doses every 12 weeks for up to 60 weeks in patients who had a clinical benefit.

RESULTS

A total of 28 patients were enrolled. Immune-related adverse events, including one death, were observed in 6 patients (21%), and graft-versus-host disease (GVHD) that precluded further administration of ipilimumab was observed in 4 patients (14%). No responses that met formal response criteria occurred in patients who received a dose of 3 mg per kilogram. Among 22 patients who received a dose of 10 mg per kilogram, 5 (23%) had a complete response, 2 (9%) had a partial response, and 6 (27%) had decreased tumor burden. Complete responses occurred in 4 patients with extramedullary acute myeloid leukemia and 1 patient with the myelodysplastic syndrome developing into acute myeloid leukemia. Four patients had a durable response for more than 1 year. Responses were associated with in situ infiltration of cytotoxic CD8+ T cells, decreased activation of regulatory T cells, and expansion of subpopulations of effector T cells in the blood.

CONCLUSIONS

Our early-phase data showed that administration of ipilimumab was feasible in patients with recurrent hematologic cancers after allogeneic HSCT, although immune-mediated toxic effects and GVHD occurred. Durable responses were observed in association with several histologic subtypes of these cancers, including extramedullary acute myeloid leukemia. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT01822509.).

Nivolumab for the treatment of classical Hodgkin lymphoma after failure of autologous stem cell transplant and brentuximab

Cancer cells are able to escape surveillance from the immune system by co-opting physiologic mechanisms such as the programmed cell death-1 (PD-1) receptor pathway. Agents able to block the interaction between the PD-1 receptor and its ligands have the potential to release T cells from tumor-induced suppression and eradicate malignant cells. Nivolumab - a PD-1 inhibitor - is approved for the treatment of patients with metastatic melanoma and lung cancer. This agent has been tested in patients with advanced Hodgkin lymphoma (HL) and showed impressive results in a phase I trial. Here we review the profile of Nivolumab including its pharmacological properties, clinical efficacy and safety in patients with advanced classical HL.

Low density of FOXP3-positive T cells in normal colonic mucosa is related to the presence of beta2-microglobulin mutations in Lynch syndrome-associated colorectal cancer

Microsatellite instability (MSI-H) is caused by DNA mismatch repair deficiency and occurs in 15% of colorectal cancers. MSI-H cancers generate highly immunogenic frameshift peptide (FSP) antigens, which elicit pronounced local immune responses. A subset of MSI-H colorectal cancers develops in frame of Lynch syndrome, which represents an ideal human model for studying the concept of immunoediting. Immunoediting describes how continuous anti-tumoral immune surveillance of the host eventually leads to the selection of tumor cells that escape immune cell recognition and destruction. Between 30 and 40% of Lynch syndrome-associated colorectal cancers display loss of HLA class I antigen expression as a result of Beta2-microglobulin (B2M) mutations. Whether B2M mutations result from immunoediting has been unknown. To address this question, we related B2M mutation status of Lynch syndrome-associated colorectal cancer specimens (n = 30) to CD3-positive, CD8-positive and FOXP3-positive T cell infiltration in both tumor and normal mucosa. No significant correlation between B2M mutations and immune cell infiltration was observed in tumor tissue. However, FOXP3-positive T cell infiltration was significantly lower in normal mucosa adjacent to B2M-mutant (mt) compared to B2M-wild type (wt) tumors (mean: 0.98% FOXP3-positive area/region of interest (ROI) in B2M-wt vs. 0.52% FOXP3-positive area/ROI in B2M-mt, p = 0.023). Our results suggest that in the absence of immune-suppressive regulatory T cells (Treg), the outgrowth of less immunogenic B2M-mt tumor cells is favored. This finding supports the immunoediting concept in human solid cancer development and indicates a critical role of the immune milieu in normal colonic mucosa for the course of disease.

Directed T-cell therapies for leukemia and lymphoma after hematopoietic stem cell transplant: beyond chimeric antigen receptors

This review focuses on the recent advances utilizing adoptive T-cell immunotherapies for patients after hematopoietic stem cell transplant using T cells after autologous transplant to treat the highest risk patients. The particular emphasis is the use of T cells to treat leukemias and lymphomas with gene transfer and nongene transfer approaches to direct specificity to tumor associated antigens. In this review, we will highlight how these novel therapeutics can be successfully used to prevent or treat high-risk patients who relapse after hematopoietic stem cell transplant.

Immune checkpoint inhibition in lymphoid disease

It has long been understood that the immune system has intrinsic anti-tumour activity in humans, and that a key mechanism of tumour progression is the ability of a tumour to escape this immune surveillance. A number of attempts have been made to harness this anti-tumour immunity in both solid tumour oncology and haematological malignancies with variable success. Examples include the use of allogeneic stem cell transplantation and donor lymphocyte infusion in haematological cancer and vaccine studies in solid tumours. Enhanced signalling of the Programmed cell death-1 (PDCD1, PD-1)/cytotoxic T-lymphocyte-associated protein 4 (CTLA4) 'immune checkpoint' pathway has emerged recently as a critical mechanism by which tumours can escape the natural anti-tumour immune response. As such, novel therapies have been developed to help enhance this natural immunity by switching off the PDCD1/CTLA4 immune checkpoint pathway. The following review will discuss the pathobiology of these pathways and the exciting new data now available in lymphoid malignancies.

Immune therapy of metastatic melanoma developing after allogeneic bone marrow transplant

Metastatic melanoma is frequently treated with immune activating therapy, which poses a theoretical risk of inducing graft versus host disease (GVHD) in those who have received allogeneic stem cell transplantation. The literature reporting the safety of immunotherapy in post transplant patients is limited. We report two patients with metastatic melanoma who received treatment with immunotherapy after allogeneic stem cell transplantation that did not result in GVHD.

T-cell immune suppression in patients with hematologic malignancies: clinical implications

SUMMARY 

The reversion of immune suppression and restoration of T-cell function against leukemia remains a significant clinical challenge. However, the advent of improved antileukemia-specific T-cell induction and the generation of gene-modified T cells has extended cellular immunotherapy to hematological malignancies. Numerous immunotherapeutic protocols have been developed aiming to enhance antileukemia T-cell immune function, eliminate leukemic cells and prevent relapse. By contrast, abnormal expression of CTLA-4 and PD1/PD-L1 plays a critical role in effector T-cell responses and increases Treg suppressive activity in patients with tumors; therefore, blocking CTLA-4, PD1 and PD-L1 is a novel approach for immunotherapy.

Prevention of graft-versus-host disease by adoptive T regulatory therapy is associated with active repression of peripheral blood Toll-like receptor 5 mRNA expression

Acute graft-versus-host disease (GVHD) occurs in 40% to 60% of recipients of partially matched umbilical cord blood transplantation (UCBT). In a phase I study, adoptive transfer of expanded CD4(+)CD25(+)Foxp3(+) natural regulatory T cells (nTregs) resulted in a reduced incidence of grade II-IV acute GVHD. To investigate potential mechanisms responsible for the reduced GVHD risk, we analyzed peripheral blood mononuclear cell mRNA expression of a tolerance gene set previously identified in operation- tolerant kidney transplant recipients, comparing healthy controls and patients who received nTregs and those who did not receive nTregs with and without experiencing GVHD. Samples from patients receiving nTregs regardless of GVHD status showed increased expression of Foxp3 expression, as well as B cell-related tolerance marker. This was correlated with early B cell recovery, predominately of naïve B cells, and nearly normal T cell reconstitution. CD8(+) T cells showed reduced signs of activation (HLA-DR(+) expression) compared with conventionally treated patients developing GVHD. In contrast, patients with GVHD had significantly increased TLR5 mRNA expression, whereas nTreg-treated patients without GVHD had reduced TLR5 mRNA expression. We identified Lin(-)HLADR(-)CD33(+)CD16(+) cells and CD14(++)CD16(-) monocytes as the main TLR5 producers, especially in samples of conventionally treated patients developing GVHD. Taken together, these data reveal interesting similarities and differences between tolerant organ and nTreg-treated hematopoietic stem cell transplantation recipients.

Control of minimal residual cancer by low dose ipilimumab activating autologous anti-tumor immunity

In this perspective article, we address the controversy regarding the safety-efficacy issue in ipilimumab trials. While the CTLA-4 blockade interrupted T-cell pathways responsible for immune down-regulation and mediated regression of established malignant tumors in a minority of patients, this has to be weighed against the immune related adverse events (irAEs) suffered by the majority. Based on two groundbreaking but neglected proof-of-principle papers that demonstrated augmented graft-vs.-malignancy (GVM) effect that reversed the relapse of malignancy without worsening the graft-vs.-host disease (GVHD) by a CTLA-4 blockade, here we suggest a therapeutic paradigm shift, which may help break the impasse and resolve this timely issue in oncology.

Dissecting graft-versus-leukemia from graft-versus-host-disease using novel strategies

The intrinsic anti-leukemic effect of allogeneic hematopoietic cell transplantation (HCT) is dependent on genetic disparity between donor and recipient, intimately associated with graft-versus-host disease (GVHD), and mediated by lymphocytes contained in or derived from the donor hematopoietic cell graft. Three decades of intense effort have not identified clinical strategies that can reliably separate the graft-versus-leukemia (GVL) effect from the alloimmune reaction that drives clinical GVHD. For patients who require HCT and for whom two or more human leukocyte antigen (HLA)-A, -B, -C, and -DRB1-matched donor candidates can be identified, consideration of donor and recipient genotype at additional genetic loci both within and outside the major histocompatibility complex may offer the possibility of selecting the donor [candidate(s)] that poses the lowest probability of GVHD and the highest probability of a potent GVL effect. Strategies for engineering conventional donor lymphocyte infusion also hold promise for prevention or improved treatment of post-transplant relapse. The brightest prospects for selectively enhancing the anti-leukemic efficacy of allogeneic HCT, however, are likely to be interventions that are designed to enhance specific antitumor immunity via vaccination or adoptive cell transfer, rather than those that attempt to exploit donor alloreactivity against the host. Adoptive transfer of donor-derived T cells genetically modified for tumor-specific reactivity, in particular, has the potential to transform the practice of allogeneic HCT by selectively enhancing antitumor immunity without causing GVHD.

CTLA-4 polymorphism and clinical outcome post allogeneic hematopoietic stem cell transplantation

CTLA-4 inhibitory molecule plays an important role in regulating T cell activation. It is considered a crucial element in keeping the immune balance and has been implicated in cancer, autoimmunity and transplantation immunology. Inconsistent observations are reported regarding its association with hematopoietic stem cell transplantation (HSCT). Genotyping of CTLA-4 was performed in recipients and their HLA-matched donors for +49A/G and CT60 polymorphisms (80 and 94 pairs, respectively) using PCR-RFLP. No association was encountered between both polymorphisms in patients and donors and acute or chronic graft versus host disease. Significant association was observed between recipient +49A/G G allele and lower disease-free survival and overall survival compared to AA genotype (HR: 2.17, p = 0.03, 95% CI: 1.05-4.48 and HR: 2.54, p = 0.01, 95% CI: 1.16-5.54), respectively. Our results suggest that CTLA-4 genotyping may predict outcome in patients post HSCT. To validate our results, further studies on a larger cohort are needed.

Developing strategies in the immunotherapy of leukemias

BACKGROUND

In the current treatment paradigms for leukemias, hematopoietic stem cell transplant (HSCT) is considered the best option with a curative potential although more often than not it simply delays disease progression. Advances are needed, both in current therapies and in the development of new strategies. Partly from studying the nuances of the curative potential of stem cell transplant, we have come to appreciate the relevance of the immune response and the potential of immunotherapy.

METHODS

This review article summarizes the recent advances in the field of immunology and immunotherapy for leukemia.

RESULTS

In passive immunotherapy, recent progress in chimeric T-cell antigen receptor technology has been encouraging. In active immunotherapy, a cancer vaccine may potentially enhance HSCT. An overview of various clinical studies of peptide vaccination strategies focusing on molecular targets such as the Wilms' tumor gene 1 (WT1), proteinase 3 (PR3), and receptor for hyaluronan acid-mediated motility (RHAMM) is provided. Cell-based vaccination strategies are also briefly explored.

CONCLUSIONS

The immune system clearly has the capacity to recognize and react to leukemic cells, and recent evidence directs our attention to the importance of mounting inflammatory and CD4 T-cell responses to complement and support the cytotoxic activity elicited by peptide vaccines.

T cell profiling reveals high CD4+CTLA-4 + T cell frequency as dominant predictor for survival after prostate GVAX/ipilimumab treatment

Immune checkpoint blockade enhances antitumor responses, but can also lead to severe immune-related adverse events (IRAE). To avoid unnecessary exposure to these potentially hazardous agents, it is important to identify biomarkers that correlate with clinical activity and can be used to select patients that will benefit from immune checkpoint blockade. To understand the consequences of CTLA-4 blockade and identify biomarkers for clinical efficacy and/or survival, an exploratory T cell monitoring study was performed in a phase I/II dose escalation/expansion trial (n = 28) of combined Prostate GVAX/ipilimumab immunotherapy. Phenotypic T cell monitoring in peripheral blood before and after Prostate GVAX/ipilimumab treatment revealed striking differences between patients who benefited from therapy and patients that did not. Treatment-induced rises in absolute lymphocyte counts, CD4(+) T cell differentiation, and CD4(+) and CD8(+) T cell activation were all associated with clinical benefit. Moreover, significantly prolonged overall survival (OS) was observed for patients with high pre-treatment frequencies of CD4(+)CTLA-4(+), CD4(+)PD-1(+), or differentiated (i.e., non-naive) CD8(+) T cells or low pre-treatment frequencies of differentiated CD4(+) or regulatory T cells. Unsupervised clustering of these immune biomarkers revealed cancer-related expression of CTLA-4(+) in CD4(+) T cells to be a dominant predictor for survival after Prostate GVAX/ipilimumab therapy and to thus provide a putative and much-needed biomarker for patient selection prior to therapeutic CTLA4 blockade.

Active immunotherapy: current state of the art in vaccine approaches for NHL

Immune therapy of cancer is a rapidly evolving field, with long-deserved successes now finally achieved. As new pathways triggered by the immune synapsis are elucidated, and new molecules responsible for immune checkpoints are being discovered, it is becoming clear that vaccination against a single antigen aided by non-specific immune stimulation is not sufficient for an efficient, long term, immune response. Though lymphoma is a highly curable malignancy, there is still a subset of patients that is at very high risk of disease relapse even after successfully completing chemotherapy or a stem cell transplant. Patients with minimal residual disease are particularly suitable for vaccination. Over the past 3 decades, the classic model of lymphoma-specific idiotype vaccine has evolved and recent data on vaccination with nonspecific oligodeoxynucleotides has provided very encouraging results. Furthermore, the introduction of checkpoint blockade via agonist or antagonist monoclonal antibodies holds the promise of significant improvement in the efficacy of future vaccines. What follows is a brief summary of the historical highlights in lymphoma immunotherapy as well as an update on the most recently published clinical trials and a look at future developments.

Interesting possibilities to improve the safety and efficacy of ipilimumab (Yervoy)

As predicted, an anti-CTLA-4 mAb (ipilimumab) on binding to T lymphocytes breaks down immune-tolerance. Thereby, it was hoped, tumor-specific-T cells would be freed for a sustained attack on cancer cells. Data on ipilimumab treatment in 1498 patients with advanced melanoma (in 14 phase I-III trials) has shown immune-related adverse events (irAEs) in 64.2% of the patients consistent with tolerance breakdown. However, there is no evidence that the antitumor effects via a CTLA-4 blockade are attributable to T cells specifically targeting tumor cells. In fact, several trials indicate a possible correlation between grade 3 and 4 irAEs with clinical efficacy of ipilimumab; tumor regression may be associated with autoimmunity development. Therefore, we suggest a new treatment paradigm. The non-tumor specific pan-lymphocytic activation should be exploited by a 'pretargeting' approach proven successful in radioimmunodetection and radioimmunotherapy. First, an anti-tumor mAb conjugated with streptavidin (StAv) should be administered to be followed by the delivery of biotin-labeled anti-CTLA-4 mAb. This schedule has the virtue of endowing T cells with the ability to travel to tumor sites without prematurely succumbing to apoptosis, while streptavidin's ultra-high affinity for biotin (K(D), 10⁻¹⁵ M) ensures capturing all T cells binding biotin labeled anti-CTLA-4. Using the law of mass action, we calculated that following administration of ipilimumab at >1 mg/L concentration (∼5 mg per patient ∼70 kgbw), the immense forces of the immune system liberated by the anti-CTLA-4 antibody blockade would then be focused with laser sharp accuracy on tumor cells without collateral damage to normal host cells.