Nivolumab salvage therapy before or after allogeneic stem cell transplantation in Hodgkin lymphoma

Outcome of High-Dose Chemotherapy Followed by Autologous Stem Cell Transplantation in Relapsed/Refractory Hodgkin Lymphoma after Different Numbers of Salvage Regimens

The introduction of novel drugs (PD-1 inhibitors and/or brentuximab vedotin) into salvage regimens has improved the response rate and the outcome of patients with relapsed/refractory Hodgkin lymphoma. However, the impact of new drugs on the outcome has not been adequately investigated so far. We retrospectively analyzed 42 consecutive patients treated at our institution with high-dose chemotherapy/autologous stem cell transplantation after either one standard chemotherapy represented by BEGEV (n = 28) or >1 salvage therapy (ST) comprising novel drugs (n = 14). With a median follow-up of 24 months, the 2-year cumulative incidence of relapse was similar between the two cohorts: 26% for 1 ST and 18% for >1 ST (p = 0.822). Consistently, overall survival and progression-free survival did not differ among the two groups: 3-year overall survival was 91% and 89% (p = 0.731), respectively, and 3-year progression-free survival was 74% and 83% (p = 0.822) for only one and more than one salvage regimens, respectively. Of note, the post-transplant side effects and engraftment rates were similar between the 1 ST and >1 ST cohorts. In conclusion, consolidation with high-dose chemotherapy/autologous stem cell transplantation is a safe and curative option, even for patients achieving disease response after more than one rescue line of therapy.

Successful restoration of checkpoint inhibitors efficacy after allogeneic hematopoietic cell transplant for classic Hodgkin lymphoma patients

BACKGROUND

Classic Hodgkin lymphoma (cHL) is a highly-curable disease. However, relapses after bone marrow transplant are challenging especially relapses after allogeneic transplant.

METHODS

A retrospective chart review of the institution transplant database to summarize the safety and efficacy of checkpoint inhibitors (CPIs) use for cHL relapses postallo-HCT in patients who already failed to derive sustained benefit from CPIs received prior to allo-HCT.

RESULTS

Six cases were identified and reviewed. All patients received and failed to derive sustained benefit from CPIs and brentuximab vedotin preallo-HCT. The median age at the time of allo-HCT was 28.6 years (IQR 23.6-34.2), the median number of lines received prior to allo-HCT was 6.5 (range 5-9). The median duration of CPI therapy prior to allo-HCT was 8.1 months (IQR 6.7-12.9). The median time between the discontinuation of CPI and allo-HCT was 5.78 months (IQR 3.15-15.8). The median time to progression postallo-HCT was 5.75 months (IQR 2.6-11.7). The median time between allo-HCT and re-challenge with a CPI was 7.6 months (IQR 3.2-28.6). The median time of follow up after starting postallo-HCT CPIs was 16 months (IQR 7.25-25.75). Five out six patients responded and two patients developed GvHD.

CONCLUSION

Our report shows preserved efficacy without any new safety signals by using CPIs postallo-HCT despite using and having failed to derive sustained benefit from CPIs preallo-HCT.

Filling the Gap: The Immune Therapeutic Armamentarium for Relapsed/Refractory Hodgkin Lymphoma

Despite years of clinical progress which made Hodgkin lymphoma (HL) one of the most curable malignancies with conventional chemotherapy, refractoriness and recurrence may still affect up to 20–30% of patients. The revolution brought by the advent of immunotherapy in all kinds of neoplastic disorders is more than evident in this disease because anti-CD30 antibodies and checkpoint inhibitors have been able to rescue patients previously remaining without therapeutic options. Autologous hematopoietic cell transplantation still represents a significant step in the treatment algorithm for chemosensitive HL; however, the possibility to induce complete responses after allogeneic transplant procedures in patients receiving reduced-intensity conditioning regimens informs on its sensitivity to immunological control. Furthermore, the investigational application of adoptive T cell transfer therapies paves the way for future indications in this setting. Here, we seek to provide a fresh and up-to-date overview of the new immunotherapeutic agents dominating the scene of relapsed/refractory HL. In this optic, we will also review all the potential molecular mechanisms of tumor resistance, theoretically responsible for treatment failures, and we will discuss the place of allogeneic stem cell transplantation in the era of novel therapies.

Checkpoint Inhibitors and the Changing Face of the Relapsed/Refractory Classical Hodgkin Lymphoma Pathway

PURPOSE OF REVIEW

Checkpoint inhibitors (CPIs) targeting PD1 are highly active in relapsed/refractory classical Hodgkin lymphoma. A plethora of recent studies, often small and non-randomised, have raised many questions about how to optimally integrate these into clinical practice. We aim to discuss the use of CPIs in different relapsed/refractory settings in an effort to better define their role and highlight areas of research.

RECENT FINDINGS

CPIs have shown efficacy at first relapse, as salvage pre- and post-autologous (ASCT) and allogeneic stem cell transplant (alloSCT) and as maintenance post-ASCT. Immune-related adverse events require careful attention, especially when used peri-alloSCT, where it is associated with hyperacute graft-versus-host disease. Newer PD1 inhibitors, as well as strategies to overcome CPI resistance, are being tested. CPIs are increasingly deployed at earlier points in the classical Hodgkin lymphoma pathway. Whilst progress is clearly being made, randomised studies are required to more clearly define the optimal positioning of these agents.

Immune cell subsets in interface cutaneous immune-related adverse events (cirAEs) associated with anti-PD-1 therapy resemble acute graft vs host disease more than lichen planus

Background

Checkpoint immunotherapy is frequently associated with cutaneous immune‐related adverse events (cirAEs), and among those, the most common subtype shows interface reaction patterns that have been likened to lichen planus (LP); however, cutaneous acute graft versus host disease (aGVHD) may be a closer histopathologic comparator. We used quantitative pathology to compare the immunologic composition of anti‐PD‐1‐associated interface reactions to LP and aGVHD to assess for similarities and differences between these cutaneous eruptions.

Methods

Immunohistochemistry for CD4, CD8, CD68, PD‐1, and PD‐L1 was performed on formalin‐fixed paraffin‐embedded tissue from patients with anti‐PD‐1 interface cirAEs (n = 4), LP (n = 9), or aGVHD (n = 5). Densities of immune cell subsets expressing each marker were quantified using the HALO image analysis immune cell module. Plasma cell and eosinophil density were quantified on routine H&E slides.

Results

Specimens from patients with anti‐PD‐1 interface cirAEs showed equivalent total cell densities and immune cell composition to those with aGVHD. Patients with LP showed higher total immune cell infiltration, higher absolute T‐cell densities, increased CD8 proportion, and reduced histiocytic component. The cases with the highest plasma cell counts were all anti‐PD‐1 interface cirAEs and aGVHD.

Conclusion

The composition of immune cell subsets in anti‐PD‐1 interface cirAEs more closely resembles the immune response seen in aGVHD than LP within our cohort. This warrants a closer look via advanced analytics and may have implications for shared pathogenesis and potential treatment options.

The outcome of patients with Hodgkin lymphoma and early relapse after autologous stem cell transplant has improved in recent years

Hodgkin lymphoma (HL) patients who relapse after autologous-stem-cell- transplantation (auto-SCT) have traditionally had a poor prognosis. We analyzed 1781 adult HL patients who relapsed between 2006 and 2017 after a first auto-SCT. The 4-year overall survival (OS) after relapse continuously increased from 32% for patients relapsing in 2006-2008, to 63% for patients relapsing in 2015-2017 (p = 0.001). The improvement over time was predominantly noted in patients who had an early relapse (within 12 months) after auto-SCT (p = 0.01). On multivariate analysis, patients who relapsed in more recent years and those with a longer interval from transplant to relapse had a better OS, whereas increasing age, poor performance status, bulky disease, extranodal disease and presence of B symptoms at relapse were associated with a worse OS. Brentuximab vedotin (BV), checkpoint inhibitors (CPI) and second transplant (SCT2; 86% allogeneic) were used in 233, 91 and 330 patients respectively. The 4-year OS from BV, CPI, and SCT2 use was 55%, 48% and 55% respectively. In conclusion, the outcome after post-transplant relapse has improved significantly in recent years, particularly in the case of early relapse. These large-scale real-world data can serve as benchmark for future studies in this setting.

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.

Novel antibodies which have an impact on immune status after allogeneic hematopoietic cell transplantation

INTRODUCTION

In the field of hematological malignancy, we often have the opportunity to use antibodies such as immune checkpoint inhibitors that can alter a patient's immune status before or after allo-HCT. The appropriate use of these novel agents is highly necessary to optimize disease control and reduce the risk of complications associated with adverse allo-immune reactions.

AREAS COVERED

Clinical data on several monoclonal antibodies targeting programmed cell death 1 (PD-1) (nivolumab or pembrolizumab), C-C chemokine receptor 4 (CCR4) (mogamulizumab), CD30 (brentuximab vedotin), or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) (ipilimumab) are reviewed, with a focus on the incidence and severity of graft-versus-host disease (GVHD).

EXPERT OPINION

While previous studies demonstrated a favorable prognosis in patients who received nivolumab prior to transplantation, the pretransplant use of nivolumab increases the incidence of GVHD, partly due to the expansion and activation of preexisting T cells. Mogamulizumab also has a significant impact on GVHD, caused by persistent depletion of regulatory T cells with CCR4 positivity. Regarding brentuximab vedotin, phase 1 trials have demonstrated considerable efficacy for steroid-refractory acute or chronic GVHD. In the future, sophisticated methods will be needed to determine the impact of each agent on immune status after allo-HCT.

Latest advances in the management of classical Hodgkin lymphoma: the era of novel therapies

Hodgkin lymphoma is a highly curable disease. Although most patients achieve complete response following frontline therapy, key unmet clinical needs remain including relapsed/refractory disease, treatment-related morbidity, impaired quality of life and poor outcome in patients older than 60 years. The incorporation of novel therapies, including check point inhibitors and antibody-drug conjugates, into the frontline setting, sequential approaches, and further individualized treatment intensity may address these needs. We summarize the current treatment options for patients with classical Hodgkin lymphoma from frontline therapy to allogeneic hematopoietic stem cell transplantation and describe novel trials in the field.

Use of checkpoint inhibitors in patients with lymphoid malignancies receiving allogeneic cell transplantation: a review

Monoclonal antibodies against checkpoint receptors or its ligands have demonstrated high response rates and durable remissions in patients with relapsed Hodgkin lymphoma (HL) and other lymphoid malignancies. However, most patients will eventually progress on therapy and may benefit from further treatments including allogenic hematopoietic cell transplantation (allo-HCT). Furthermore, the use of checkpoint inhibitors (CPI) has emerged as a treatment option for patients relapsing after allo-HCT. The immune effects of the checkpoint blockade leading to a T-cell activation have raised some concerns on the safety of these therapies used either before or after allo-HCT, due to the potential risk of graft-versus-host disease (GVHD). Furthermore, CPI might also induce other immune toxicities, that can affect almost any organ, as a result of the dysregulation on the immune system balance. This review aims to focus on the evidence behind the use of CPI in patients with lymphoma who undergo allo-HCT. We summarize the clinical data generated to date about the use of CPI in HL and other lymphoid malignancies, the mechanisms of checkpoint inhibition in the context of allo-HCT as well as the clinical and biological observations of different GVHD prophylaxis in this setting. Furthermore, we discuss the evidence from retrospective series and early clinical trials on the feasibility and safety of the use of CPI in patients who relapsed after allo-HCT.

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.

Successful Use of Nivolumab in a Patient with Head and Neck Cancer After Allogeneic Bone Marrow Transplantation

Recently, programmed cell death 1(PD-1) inhibitors have shown a significant curative effect in the treatment of most solid cancers and some hematological malignancies. The effects of PD-1 inhibitors in recurrent head and neck squamous cell carcinoma (HNSCC) have also been confirmed. However, there is a lack of reliable clinical evidence to confirm the safety and efficacy of PD-1 inhibitors in patients after allogeneic hematopoietic stem cell transplantation, especially when the patient has a second primary cancer. Generally, graft-versus-host disease (GVHD) is unpredictable among these patients. Here we report the case of a patient who successfully used nivolumab without any GVHD or other immune-related adverse events for HNSCC after allogeneic bone marrow transplantation because of the Philadelphia chromosome-positive T cell acute lymphoblastic leukemia.

PD-1 antibody and ruxolitinib enhances graft-versus-lymphoma effect without increasing acute graft-versus-host disease in mice

Boosting T cell immune response posttransplant with checkpoint inhibitors increases graft-versus-lymphoma (GVL) effects at the cost of increasing acute graft-versus-host disease (aGVHD). A combined targeted therapy is needed to decrease checkpoint inhibitors-induced aGVHD without impairing GVL. We studied whether this competition could be avoided by giving concurrent anti-PD-1 antibody and ruxolitinib in allotransplant mouse models in which recipients were challenged with A20 or EL4 lymphoma cells. Given alone the PD-1 antibody increased GVL but did not improve survival of recipients challenged with A20 cells because of increased deaths from aGVHD. Adding ruxolitinib decreased levels of effector T cells and related cytokines. Tbx21^- T cells had higher PD-1 levels compared with Tbx21⁺ T cells. Ruxolitinib increased PD-1 levels on donor T cells by suppressing Tbx21 expression. Ruxolitinib increased apoptosis of T cells which was reversed by the PD-1 antibody. PD-1 antibody preserved expression of granzyme B and cytotoxicity of T cells which were decreased by ruxolitinib. The net result of combined therapy was increased GVL, no increase in aGVHD and increased survival. The combined therapy improved survival of recipients challenged by A20 cells which expressed high level of PD-L1, but not EL4 cells which do not express PD-L1.

Case Report: Combination Therapy With PD-1 Blockade for Acute Myeloid Leukemia After Allogeneic Hematopoietic Stem Cell Transplantation Resulted in Fatal GVHD

Background: Azacitidine is commonly used in the treatment of relapsed acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT), but the effectiveness of this monotherapy is still very low. A possible mechanism of resistance to hypomethylating agents (HMAs) is the upregulation of the expression of inhibitory checkpoint receptors and their ligands, making the combination of HMAs and immune checkpoint blockade therapy a rational approach. Although the safety of anti-programmed cell death protein (PD)-1 antibodies for patients with post-allo-HSCT remains a complicated issue, the preliminary clinical result of combining azacitidine with anti-PD-1 antibodies is encouraging; however, the safety and efficacy of this approach need further investigation. Case Presentation: We reported a case of treated secondary (ts)-AML in a patient who received tislelizumab (an anti-PD-1 antibody) in combination with azacitidine. The patient relapsed after allo-HSCT and was previously exposed to HMAs-based therapy. The patient received tislelizumab for compassionate use. After the combination treatment, the patient achieved complete remission with incomplete hematologic recovery, negative minimal residual disease (MRD) by flow cytometry (FCM), and negative Wilms' tumor protein 1 (WT1). However, the patient successively developed serious immune-related adverse events (irAEs) and graft vs. host disease (GVHD) and eventually died from complications of GVHD. Conclusion: To our knowledge, this is the first case to report the combined use of tislelizumab and azacitidine to treat relapsed AML posttransplantation. This report highlights the safety concerns of using an anti-PD-1 antibody in combination with azacitidine after allo-HSCT, especially the risk of GVHD, and provides a basis for future studies.

Allogeneic Hematopoietic Stem Cell Transplantation in Cutaneous T-Cell Lymphomas

Simple Summary

Advanced-stage cutaneous T-cell lymphomas are aggressive diseases with frequent disease relapses and a reduced overall survival. Most treatment regimens fail to induce long-term remissions. Allogeneic hematopoietic stem cell transplantation has been associated with treatment-free long-term remissions and holds a potential for cure in this disease but is associated with frequent complications, mostly linked to the development of graft-versus-host disease and infections. Herein, we review the current evidence supporting the use of allogeneic stem cell transplantation in advanced-stage cutaneous T-cell lymphomas.

Abstract

Cutaneous T-cell lymphomas (CTCLs) are non-Hodgkin lymphomas that develop primarily in the skin. They account for almost 80% of primary cutaneous lymphomas. Epidermotropic CTCLs (mycosis fungoides (MF) and Sézary syndrome (SS)) are the most common form of CTCL. The course of the disease ranges from an indolent clinical behavior in early-stage disease to an aggressive evolution in the advanced stages. Advanced-stage disease is defined by the presence of tumors, erythroderma, or significant blood, nodal or visceral involvement. Advanced-stage disease is characterized by frequent disease relapses, refractory disease, a severely impaired quality of life and reduced overall survival. In the last twenty-five years, allogeneic hematopoietic stem cell transplantation (HSCT) has led to prolonged remissions in advanced CTCL, presumably linked to a graft-versus-lymphoma effect and is thus emerging as a potential cure of the disease. However, the high post-transplant relapse rate and severe morbidity and mortality associated with graft-versus-host disease and infections are important issues. Allogeneic HSCT is thus mostly considered in young patients with no comorbidities and an aggressive, advanced-stage CTCL. Allogeneic HSCT gives the best results in patients with a pre-transplant complete remission of the lymphoma. For this reason, one of the challenges is to define the best time to consider allogeneic HSCT in the disease course. Early identification of patients at high risk for progression is important to identify candidates who may benefit from allogeneic HSCT before their disease becomes treatment-refractory. This review describes the role of allogeneic HSCT in CTCL, summarizes the published data and future perspectives in this area.

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.

Safety and efficacy of anti-programmed cell death-1 monoclonal antibodies before and after allogeneic hematopoietic cell transplantation for relapsed or refractory Hodgkin lymphoma: a multicenter retrospective study

We conducted a multicenter study on anti-programmed cell death-1 monoclonal antibodies (anti-PD-1 mAbs) before/after allogeneic hematopoietic cell transplantation (allo-HCT) for Hodgkin lymphoma. Anti-PD-1 mAbs were administered to 25 patients before allo-HCT and to 20 after allo-HCT. In pre-allo-HCT setting, the median interval from the last administration to allo-HCT was 59 days. After allo-HCT, 12 patients developed non-infectious febrile syndrome requiring high-dose corticosteroid. The cumulative incidences of grade II-IV acute graft-versus-host disease (aGvHD) were 47.1%. Eight patients who had GvHD prophylaxis with post-transplant cyclophosphamide (PTCy) had less frequent aGvHD (grade II-IV, 14.6% versus 58.8%; P = 0.086). The 1 year overall survival (OS), relapse/progression, and non-relapse mortality rates were 81.3%, 27.9%, and 8.4%. In post-allo-HCT setting, the median interval from allo-HCT to the first administration was 589 days. The overall and complete response rates were 75% and 40%. At 100 days after anti-PD-1 therapy, the cumulative incidences of grade II-IV aGvHD, moderate-to-severe chronic GvHD, and grade 3-4 immune-related toxicity were 15.0%, 30.0%, and 30.0%. While the 1 year relapse/progression rate was 47.4%, the 1 year OS probability was 89.7%. In conclusion, immune-related complications were frequent despite modifications of GvHD prophylaxis or anti-PD-1 mAb dosing. In anti-PD-1-mAb-pretreated patients, PTCy-based GvHD prophylaxis may be effective.

Relapse of Hodgkin lymphoma after autologous hematopoietic cell transplantation: A current management perspective

Hodgkin lymphoma (HL) is a highly responsive disease with nearly 70% of patients experiencing cure after front-line chemotherapy. Patients who experience disease relapse receive salvage chemotherapy followed by consolidation with autologous hematopoietic cell transplantation (auto-HCT). Nearly 50% of patients relapse after an auto-HCT and constitute a subgroup with poor prognosis. Novel treatments such as immune checkpoint inhibitors and an anti-CD30 monoclonal antibody are currently approved for patients relapsing after auto-HCT; however, the duration of remission with these therapies remains limited. Allogeneic HCT is currently the only potentially curative treatment modality for patients relapsing after a prior auto-HCT. Early clinical trials with chimeric antigen receptor T-cell therapy targeting CD30 are underway for patients with relapsed/refractory HL and are already demonstrating safety and promising efficacy.

PD-L1 siRNA-mediated silencing in acute myeloid leukemia enhances anti-leukemic T cell reactivity

Acute myeloid leukemia (AML) is an immune-susceptible malignancy, as demonstrated by its responsiveness to allogeneic stem cell transplantation (alloSCT). However, by employing inhibitory signaling pathways, including PD-1/PD-L1, leukemia cells suppress T cell-mediated immune attack. Notably, impressive clinical efficacy has been obtained with PD-1/PD-L1 blocking antibodies in cancer patients. Yet, these systemic treatments are often accompanied by severe toxicity, especially after alloSCT. Here, we investigated RNA interference technology as an alternative strategy to locally interfere with PD-1/PD-L1 signaling in AML. We demonstrated efficient siRNA-mediated PD-L1 silencing in HL-60 and patients' AML cells. Importantly, WT1-antigen T cell receptor⁺ PD-1⁺ 2D3 cells showed increased activation toward PD-L1 silenced WT1⁺ AML. Moreover, PD-L1 silenced AML cells significantly enhanced the activation, degranulation, and IFN-γ production of minor histocompatibility antigen-specific CD8⁺ T cells. Notably, PD-L1 silencing was equally effective as PD-1 antibody blockade. Together, our study demonstrates that PD-L1 silencing may be an effective strategy to augment AML immune-susceptibility. This provides rationale for further development of targeted approaches to locally interfere with immune escape mechanisms in AML, thereby minimizing severe toxicity. In combination with alloSCT and/or adoptive T cell transfer, this strategy could be very appealing to boost graft-versus-leukemia immunity and improve outcome in AML patients.

The Role of Immune Checkpoints after Cellular Therapy

Cellular therapies utilize the powerful force of the human immune system to target malignant cells. Allogeneic hematopoietic stem cell transplantation (allo-HCT) is the most established cellular therapy, but chimeric antigen receptor (CAR) T cell therapies have gained attention in recent years. While in allo-HCT an entirely novel allogeneic immune system facilitates a so-called Graft-versus-tumor, respectively, Graft-versus-leukemia (GvT/GvL) effect against high-risk hematologic malignancies, in CAR T cell therapies genetically modified autologous T cells specifically attack target molecules on malignant cells. These therapies have achieved high success rates, offering potential cures in otherwise detrimental diseases. However, relapse after cellular therapy remains a serious clinical obstacle. Checkpoint Inhibition (CI), which was recently designated as breakthrough in cancer treatment and consequently awarded with the Nobel prize in 2018, is a different way to increase anti-tumor immunity. Here, inhibitory immune checkpoints are blocked on immune cells in order to restore the immunological force against malignant diseases. Disease relapse after CAR T cell therapy or allo-HCT has been linked to up-regulation of immune checkpoints that render cancer cells resistant to the cell-mediated anti-cancer immune effects. Thus, enhancing immune cell function after cellular therapies using CI is an important treatment option that might re-activate the anti-cancer effect upon cell therapy. In this review, we will summarize current data on this topic with the focus on immune checkpoints after cellular therapy for malignant diseases and balance efficacy versus potential side effects.

First Report of Severe Acute Graft-Versus-Host Disease After Allogeneic Stem Cell Transplant in a Patient With Myelodysplastic Syndrome Treated With Atezolizumab: Literature Review

Checkpoint inhibitors have become a widely used and available immunotherapy option for treating a variety of malignancies, including hematological malignancies. Patients receiving these therapies may go on to receive a curative allogeneic hematopoietic stem cell transplant (allo-HSCT). This presents a clinical challenge as the safety and efficacy of HSCT is not well reported in this subset of patients and residual programmed death-ligand 1 inhibition could potentially enhance allogeneic T-cell responses, improving the graft-versus-tumor effect, but also increasing the incidence and severity of immune complications such as graft-versus-host disease (GVHD). Here, this report includes a detailed literature review summarizing all available data on HSCT outcomes in the setting of using checkpoint inhibitor therapy pre-transplant. Moreover, we report a case of acute GVHD after allo-HSCT in a patient with high-risk myelodysplastic syndrome who received prior atezolizumab therapy, highlighting the importance of further research into this specific population in order to improve transplant-related outcomes.

Outcome after autologous stem cell transplantation in primary refractory or relapsed Hodgkin lymphoma-a long-term follow-up single center experience

Autologous stem cell transplantation (autoSCT) can achieve long-term remission in primary refractory or relapsed Hodgkin lymphoma (r/r HL); however, still up to 50% of patients relapse after autoSCT. In this retrospective analysis, we investigated the impact of autologous stem cell transplantation in a consecutive, unselected cohort of primary refractory and relapsed Hodgkin lymphoma patients (n = 66) with the majority of patients treated in the pre-brentuximab vedotin and immune checkpoint inhibitor era. In our cohort, a 5-year overall survival (OS) from autoSCT of 59.5% and a 5-year progression-free survival (PFS) after autoSCT of 46.1% was achieved. Multivariate analysis revealed primary refractory disease and early relapse (< 12 months) after initial therapy as well as the presence of B symptoms at relapse as independent risk factors associated with a higher risk for relapse and an inferior PFS and OS. Several other clinical factors, including the presence of extranodal disease at relapse and failure to achieve a complete response to salvage chemotherapy, were associated with a trend towards an inferior survival. Patients relapsing after autoSCT had a particularly poor outcome, regardless of eligibility to undergo allogeneic stem cell transplantation (alloSCT). We further evaluated recently published prognostic models for r/r HL patients undergoing autoSCT and could validate several risk scores in our independent "real world" cohort.

Clinical Development of PD-1 Blockade in Hematologic Malignancies

Clinical development of immune checkpoint inhibitors targeting the PD-1 pathway has led to clinical benefits for patients with multiple solid tumor and hematologic malignancies and has revolutionized modern oncology. High response rates to PD-1 blockade in patients with classical Hodgkin lymphoma and certain subtypes of non-Hodgkin lymphoma highlight an intrinsic biologic sensitivity to this strategy of treatment. Despite early success of checkpoint inhibitor and immunomodulatory drug combinations in phase 2 studies in multiple myeloma, safety concerns in patients treated with the combination of immunomodulatory drugs and checkpoint inhibitors in myeloma have stalled drug development in this space. Novel combination approaches exploring PD-1 inhibitors with epigenetic modifiers in leukemia are underway.

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.

Recommendations for managing PD-1 blockade in the context of allogeneic HCT in Hodgkin lymphoma: taming a necessary evil

PD-1 blockade is an effective therapy in relapsed/refractory (R/R) classical Hodgkin Lymphoma (cHL) who have relapsed after or are ineligible for autologous hematopoietic cell transplantation (HCT). Although single-agent anti-PD-1 monoclonal antibodies (mAb’s) are associated with high response rates and durable remissions, available results to date suggest that a large majority of patients will eventually progress on therapy. Many of these patients are potential candidates for allogeneic HCT (allo-HCT) after receiving anti-PD-1 mAb’s, and allo-HCT remains for now the only treatment with demonstrated curative potential in this setting. However, initial reports suggested that allo-HCT in this setting may be associated with increased risk of early transplant-related toxicity, likely driven by lingering effects of PD-1 blockade. Furthermore, many patients with R/R cHL who undergo allo-HCT will relapse after transplantation, most often with limited treatment options. Here again, PD-1 blockade appears to yield high response rates, but with an increased risk of attendant immune toxicity. Many questions remain regarding the use of PD-1 blockade before or after allo-HCT, especially in relation to the feasibility, outcome, optimal timing, and method of allo-HCT after PD-1 blockade. Despite the scarcity of prospective data, these questions are unavoidable and must be tackled by clinicians in the routine care of patients with advanced cHL. We provide consensus recommendations of a working group based on available data and experience, in an effort to help guide treatment decisions until more definitive data are obtained.

Pembrolizumab and its role in relapsed/refractory classical Hodgkin's lymphoma: evidence to date and clinical utility

Immune evasion is a critical mechanism of malignant cell survival, and relies in part on molecular signaling through the programmed cell death 1 (PD-1)/PD-1 ligand (PD-L1) axis that contributes to T cell exhaustion. Immune modulatory therapy with monoclonal antibodies against PD-1 designed to enhance antitumor immune response have shown promise in the treatment of advanced solid tumors and hematologic malignancies. Classical Hodgkin's lymphoma (cHL), a unique B cell malignancy characterized by an extensive but ineffective immune cell infiltrate surrounding a small number of tumor cells, has shown significant response to anti-PD-1 directed therapy. The anti-PD-1 monoclonal antibodies nivolumab and pembrolizumab have shown similarly remarkable activity in relapsed/refractory cHL and have been approved by the Food and Drug Administration for treatment of this disease. In this article we review the rationale of targeting the PD-1/PD-L1 axis in cHL and the pharmacology of pembrolizumab, and summarize the data on activity and safety profile of this agent in the treatment of relapsed/refractory cHL. We also discuss the potential benefits and pitfalls of using PD-1 blockade in the setting of allogeneic stem-cell transplantation, and summarize ongoing prospective trials of single-agent pembrolizumab and combination strategies as well as future directions.

Brentuximab vedotin prior to allogeneic stem cell transplantation in Hodgkin lymphoma: a report from the EBMT Lymphoma Working Party

Brentuximab vedotin (BV) is an anti-CD30 antibody-drug conjugate. Preliminary data suggest that BV might improve outcomes after allogeneic stem cell transplantation (SCT) for Hodgkin lymphoma (HL) when used as pre-transplant salvage therapy. Between 2010 and 2014, 428 adult patients underwent an allogeneic SCT for classical HL at participating centres of the European Society for Blood and Marrow Transplantation. We compared the outcomes of 210 patients who received BV prior to allogeneic SCT with that of 218 patients who did not receive BV. The median follow-up for survivors was 41 months. Patients in the BV group were more heavily pre-treated (median pre-allograft treatment lines: 4 vs. 3). The two groups were comparable in terms of disease status, performance status, comorbidities, prior autologous SCT, type of donor, conditioning and in vivo T cell depletion. In multivariate analysis, pre-allograft BV had no impact on acute graft-versus-host disease (GVHD), non-relapse mortality, cumulative incidence of relapse, progression-free survival or overall survival (OS), but significantly reduced the risk of chronic GVHD (hazard ratio = 0·64; 95% confidence interval = 0·45-0·92; P < 0·02). Older age, poor performance status, use of pre-transplant radiotherapy and active disease at SCT adversely affected OS. Patients allografted for HL after prior exposure to BV do not have a superior outcome after allogeneic SCT except for a lower risk of chronic GVHD. However, BV may improve the outlook of allogeneic SCT by helping otherwise refractory patients to achieve a more favourable disease status, facilitating allotransplant success.

Tyrosine kinase inhibitors and immune checkpoint blockade in allogeneic hematopoietic cell transplantation

Advances in the prevention of graft-versus-host disease (GVHD) and opportunistic infection have improved survival after allogeneic hematopoietic cell transplantation (allo-HCT) in the past decade. However, few inroads have been made into the treatment or prevention of relapse of the underlying malignancy for which allo-HCT is being performed. The introduction of US Food and Drug Administration-approved agents with significant activity in a variety of hematologic malignancies provides an opportunity to evaluate these interventions in the allo-HCT setting. Some of the most promising new agents include tyrosine kinase inhibitors (TKIs) directed at bcr-abl, kinase inhibitors targeting fms-like tyrosine kinase 3, and immune checkpoint inhibitors blocking both CTLA4 and PD-1. Data have emerged indicating potential efficacy of these agents in preventing or treating relapse, though definitive evidence remains elusive. However, potential toxicity can be considerable, highlighting the need for further clinical trials to define the therapeutic window. This review explores the immunologic and clinical consequence of treatment with both TKIs and checkpoint inhibitors in the peri- and post-allo-HCT setting.

Stop and go: hematopoietic cell transplantation in the era of chimeric antigen receptor T cells and checkpoint inhibitors

PURPOSE OF REVIEW

For several decades, hematopoietic cell transplantation (HCT) has been considered the standard curative therapy for many patients with hematological malignancies. In addition to the cytotoxic effects of the chemotherapy and radiation used in the conditioning regimen, the benefits of HCT are derived from a reset of the immune system and harnessing the ability of donor T cells to eliminate malignant cells. With the dawn of the era of immunotherapies in the form of checkpoint inhibitors and chimeric antigen receptor (CAR) T cells, the role of HCT has evolved.

RECENT FINDINGS

Immunotherapy with checkpoint inhibitors is increasingly being used for relapsed Hodgkin and non-Hodgkin lymphoma after autologous HCT. Checkpoint inhibitors are also being tested after allogeneic HCT with observable benefits in treating hematological malignancies, but with a potential risk of increased graft versus host disease and transplant-related mortality. Immunotherapy with Cluster of differentiation 19 CAR T cells are powerful options with aggressive B-cell malignancies both for therapy and as induction leading to allogeneic HCT.

SUMMARY

Although immunotherapies with checkpoint inhibition and CAR T cells are increasingly being used to treat hematological malignancies, HCT remains a standard of care for most of the diseases with the best chance of cure. Combination of these therapies with HCT has the potential to more effectively treat hematological malignancies.

Immunotherapy of Lymphoma and Myeloma: Facts and Hopes

Immune checkpoint blockade has driven a revolution in modern oncology, and robust drug development of immune checkpoint inhibitors is underway in both solid tumors and hematologic malignancies. High response rates to programmed cell death 1 (PD-1) blockade using nivolumab or pembrolizumab in classical Hodgkin lymphoma (cHL) and several variants of non-Hodgkin lymphoma (NHL) revealed an intrinsic biological sensitivity to this approach, and work is ongoing exploring combinations with immune checkpoint inhibitors in both cHL and NHL. There are also preliminary data suggesting antitumor efficacy of PD-1 inhibitors used in combination with immunomodulatory drugs in multiple myeloma, and effects of novel monoclonal antibody therapies on the tumor microenvironment may lead to synergy with checkpoint blockade. Although immune checkpoint inhibitors are generally well tolerated, clinicians must use caution and remain vigilant when treating patients with these agents in order to identify immune-related toxicities and prevent treatment-related morbidity and mortality. Autologous stem cell transplant is a useful tool for treatment of hematologic malignancies and has potential as a platform for use of immune checkpoint inhibitors. An important safety signal has emerged surrounding the risk of graft-versus-host disease associated with use of PD-1 inhibitors before and after allogeneic stem cell transplant. We aim to discuss the facts known to date in the use of immune checkpoint inhibitors for patients with lymphoid malignancies and our hopes for expanding the benefits of immunotherapy to patients in the future. Clin Cancer Res; 24(5); 1002-10. ©2017 AACR.