Successful treatment with low-dose nivolumab in refractory Hodgkin lymphoma after allogeneic stem cell transplantation

Dosing Regimens of Immune Checkpoint Inhibitors: Attempts at Lower Dose, Less Frequency, Shorter Course

Immune checkpoint inhibitors (ICIs) are a revolutionary breakthrough in the field of cancer by modulating patient's own immune system to exert anti-tumor effects. The clinical application of ICIs is still in its infancy, and their dosing regimens need to be continuously adjusted. Pharmacokinetic/pharmacodynamic studies showed a significant plateau in the exposure-response curve, with high receptor occupancy and plasma concentrations achieved at low dose levels. Coupled with concerns about drug toxicity and heavy economic costs, there has been an ongoing quest to reevaluate the current ICI dosing regimens while preserving maximum clinical efficacy. Many clinical data showed remarkable anticancer effects with ICIs at the doses far below the approved regimens, indicating the possibility of dose reduction. Our review attempts to summarize the clinical evidence for ICIs regimens with lower-dose, less-frequency, shorter-course, and provide clues for further ICIs regimen optimization.

Role of Radiation Based Conditioning Regimens in Patients With High-Risk AML Undergoing Allogenic Transplantation in Remission or Active Disease and Mechanisms of Post-Transplant Relapse

In the two decades there has been a consistent improvement in the clinical outcomes of patients diagnosed with acute leukemia undergoing allogenic stem cell transplantation. These improvements have been made possible by advancements in supportive care practices, more precise risk stratification of leukemia patients by genetic testing at diagnosis, accurate disease assessment by measurable residual disease (MRD) in pretransplant marrow and attempts to clear residual disease clones prior to transplant. Availability of targeted therapies, immunotherapies, and approval of novel drug combinations with BCL-2 inhibitors has also improved remission rates for patients who are undergoing transplant. For patients who are unable to achieve a morphologic or MRD^- remission prior to transplant, the risk of relapse post-transplant remains high. Total body irradiation (TBI) based intensification of transplant conditioning may be able to overcome risk of increased relapse rate in this clinical setting by improving clearance of leukemic clones. However, in the past increased nonrelapse mortality (NRM) associated with escalation of conditioning intensity has neutralized any potential benefit of decreasing relapse rate in HCT patient resulting in no significant improvement in overall survival. In this review we discuss incorporation of newer radiation techniques such as total marrow irradiation (TMI) to safely deliver targeted doses of radiation at higher doses to improve outcomes of patients with active leukemia. We also discuss the mechanisms associated with leukemia relapse and treatment options available in post allo-HCT relapse setting despite use of intensified conditioning regimens.

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.

Considerations for immunotherapy in patients with cancer and comorbid immune dysfunction

Immune checkpoint inhibitors have been widely incorporated for cancer treatment in a variety of solid and hematologic malignancies. Multiple clinical trials have demonstrated the efficacy of PD-1/PD-L1 and CTLA-4 axis inhibition in the metastatic and adjuvant settings. Due to the risks of autoimmune toxicity with these agents, stringent inclusion/exclusion criteria were employed in those initial clinical trials. These criteria led to exclusion or underrepresentation of a variety of patient populations with underlying immune dysfunction. These populations included patients with preexisting autoimmune diseases, solid organ or bone marrow transplant recipients, patients with HIV or viral hepatitis infections, patients receiving concurrent chronic steroid therapy, as well as patients who were elderly, pregnant, or had poor performance status. Thus, established guidelines on the use of immune checkpoint inhibitors in these patients are lacking, and evidence to support efficacy or toxicity are overall limited to retrospective studies and case series. Fortunately, ongoing clinical trials are now including these patients and are shedding light on whether these underrepresented populations can also safely benefit from immune checkpoint inhibitor therapies. In this review, we summarize the most clinically relevant available data on the use of checkpoint inhibitors in immunocompromised patient groups with a primary focus on safety.

Repeated courses of escalating doses of Nivolumab in refractory Hodgkin lymphoma with recurrent relapses post allografting: A safe and effective treatment approach

For patients with Hodgkin Lymphoma (HL) who experience relapse post allogeneic stem cell transplantation, limited treatment options exist, and the ultimate outcome is poor. Recently, the programmed cell death protein-1 (PD-1) inhibitors have shown remarkable efficacy in patients with refractory/relapsed HL, also demonstrating an acceptable safety profile. However, due to effects on T-cell activity, the use of PD-1 inhibitors post allografting may potentially increase the risk of treatment-emergent graft versus host disease. We herein report the clinical course of a patient who experienced multiple relapses of HL post allogeneic stem cell transplantation. He failed several treatment modalities but he responded to escalating doses of the PD-1 inhibitor nivolumab, given at two different treatment time points, also demonstrating minimal and easily manageable toxicity.

The Right Dose: From Phase I to Clinical Practice

To realize the full potential of promising new anticancer drugs, it is of paramount importance to administer them at the right dose. The aim of this educational article is to provide several opportunities to optimize anticancer drug dosing, focusing on oral targeted therapies. First, therapeutic drug monitoring can optimize exposure in individual patients, if the optimal concentration is known. This approach is of particular interest in regard to oral kinase inhibitors with high interindividual pharmacokinetic variability. If exposure is related to response, then therapeutic drug monitoring is potentially feasible, although the clinical utility of this approach has not yet been established. Other approaches to reduce variability include administration of more frequent, smaller doses and administration under optimal prandial conditions. However, for many drugs, the labeled dose has not been demonstrated to be the optimal dose; for such agents, the vast majority of patients may be receiving excessive doses, which results in excessive toxicity. Furthermore, administration of lower off-label doses may reduce both medical and financial toxicity. These strategies should be applied from registration studies to clinical practice, with the goal of better optimizing anticancer treatment.

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.

Graft Versus Host Disease Associated with Immune Checkpoint Inhibitors: A Pharmacovigilance Study and Systematic Literature Review

Background: In patients with allogenic hematopoietic stem cell transplantation (allo-HSCT), immune-checkpoint inhibitors (ICI) are used to treat malignancy recurrence. However, ICI are also associated with graft vs. host disease (GVHD). In this pharmacovigilance analysis, we aimed to characterize cases of GVHD associated with ICI, drawn from the World Health Organization pharmacovigilance database, VigiBase®, and from literature. Methods: We performed VigiBase® query of cases of GVHD associated with ICI. These cases were combined with those of literature, not reported in VigiBase®. The Bayesian estimate of disproportionality analysis, the information component, was considered significant if its 95% credibility interval lower bound was positive; denoting a significant association between GVHD and the suspected ICI. Time to onset between ICI and GVHD onset and subsequent mortality were assessed. Results: Disproportionality analysis yielded 93 cases of GVHD associated with ICI (61.8% men, median age 38 [interquartile range = 27; 50] years). Cases were mostly associated with nivolumab (53/93, 57.0%), pembrolizumab (23/93, 24.7%) and ipilimumab (12/93, 12.9%) monotherapies. GVHD events occurred after 1 [1; 5.5] injection of ICI, with a time to onset of 35 [IQR = 14; 176] days. Immediate subsequent mortality after GVHD was 24/93, 25.8%. There was no significant difference in mortality depending on the molecule (p = 0.41) or the combination regimen (combined vs. monotherapy, p = 0.60). Previous history of GVHD was present in 11/18, 61.1% in cases reported in literature. Conclusion: In this worldwide pharmacovigilance study, disproportionality yielded significant association between GVHD and ICI, with subsequent mortality of 25.8%. Previous history of GVHD was reported in more than half of cases. Clinicaltrials.gov identifier: NCT03492242.

A Phase 2 Study of Nivolumab Using a Fixed Dose of 40 mg (Nivo40) in Patients With Relapsed/Refractory Hodgkin Lymphoma

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The introduction of nivolumab has changed the landscape of relapsed/refractory classical Hodgkin lymphoma (r/r cHL) treatment. Despite its clinical importance, this therapy may remain inaccessible for a significant number of patients worldwide, especially in low-income countries, due to its high cost. The results of pharmacokinetic analysis and clinical observations suggest the potential efficacy of low dose nivolumab in r/r cHL patients. The aim of this trial was to assess the efficacy and safety of nivolumab at a fixed dose of 40 mg in patients with r/r cHL. The study included 30 patients with r/r cHL, treated with 40 mg nivolumab every 2 weeks. The median dose of nivolumab per kilogram bodyweight was 0.59 mg/kg (0.4–1 mg/kg). Median follow up was 19.2 months (range 12.7–25.4). The objective response rate was 70%, with 13 (43.3%) patients achieving a complete response. Median PFS was 18.4 months (95% CI, 11.3 to 18.5 months) with 18-month PFS of 53.6% (95% CI, 32%–71%). At the time of analysis, 96.7% of patients were alive with a median OS not reached. Severe (grade 3–5) adverse events were observed in 4 patients (13.3%). Nivolumab in a fixed dose of 40 mg was efficient in patients with r/r cHL, independent from dose per kg bodyweight. The results of this study are in good agreement with previously reported data and create a rationale for further studies aimed to define the optimal dosing regimen of nivolumab for the treatment of r/r cHL. Registered at www.clinicaltrials.gov (NCT03343665)

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.

Mechanisms of Leukemia Immune Evasion and Their Role in Relapse After Haploidentical Hematopoietic Cell Transplantation

Over the last decade, the development of multiple strategies to allow the safe transfer from the donor to the patient of high numbers of partially HLA-incompatible T cells has dramatically reduced the toxicities of haploidentical hematopoietic cell transplantation (haplo-HCT), but this was not accompanied by a similar positive impact on the incidence of post-transplantation relapse. In the present review, we will elaborate on how the unique interplay between HLA-mismatched immune system and malignancy that characterizes haplo-HCT may impact relapse biology, shaping the selection of disease variants that are resistant to the “graft-vs.-leukemia” effect. In particular, we will present current knowledge on genomic loss of HLA, a relapse modality first described in haplo-HCT and accounting for a significant proportion of relapses in this setting, and discuss other more recently identified mechanisms of post-transplantation immune evasion and relapse, including the transcriptional downregulation of HLA class II molecules and the enforcement of inhibitory checkpoints between T cells and leukemia. Ultimately, we will review the available treatment options for patients who relapse after haplo-HCT and discuss on how a deeper insight into relapse immunobiology might inform the rational and personalized selection of therapies to improve the largely unsatisfactory clinical outcome of relapsing patients.

Multi-organ failure induced by Nivolumab in the context of allo-stem cell transplantation

Background

Immune checkpoint inhibitors have radically changed the landscape of anti-tumor therapies in several malignancies. However the adverse events associated with immune checkpoint blockade in combination with other treatments remains to be thoroughly documented. Here we report the case of a 33-year-old male with classical Hodgkin lymphoma who was successfully treated for lymphoma but experienced serious and eventually fatal multisystem organ failure following nivolumab administration and allogeneic stem cell transplantation.

Case presentation

The patient was diagnosed with stage IIIa nodular sclerosing Hodgkin lymphoma. Originally treated by chemotherapy and autologous stem cell transplantation, he subsequently received two allogeneic stem cell transplants from matched and haplo-identical siblings upon successive disease recurrences. Nivolumab treatment was administered prior to the second allograft, after which complete remission of lymphoma was achieved (year 10), as evidenced by clinical and radiographic examination. However within the next 3 months, the patient went on to develop a constellation of symptoms affecting multiple organs, including acute pneumonia with no evidence of bacterial infection, widespread cutaneous eruptions on trunk and lower limbs, mucosal ulcerations, myositis, diarrhea and colitis. Further complications included hepatic cytolysis, acute renal failure, pancreatitis, as well as complete heart block. Some of these injuries being suggestive of graft-versus-host disease, the patient was administered immunosuppressive therapy (mycophenolate, steroids and polyvalent immunoglobulins), but died shortly afterwards. Tissue biopsies revealed extensive lymphocytic infiltration (mostly CD3 + T cells) in skin, liver, and most peculiarly in muscles, including the myocardium. Massive lymphoid-histiocytic infiltration of muscle fibers was accompanied by acute necrotizing myositis and endomysial inflammation.

Conclusions

Multi-organ failure represents a rare but potentially fatal outcome of immune checkpoint blockade in patients receiving allogeneic stem cell grafts. Nivolumab may induce atypical immune-mediated tissue inflammation and damage, such as the extensive muscular polymyositis described here in a patient with Hodgkin lymphoma. Nivolumab might also worsen GVHD symptoms in the context of allogeneic stem cell transplantation. Irrespective of the actual pathological mechanisms, clinicians should be alerted to these fatal drug-related toxicities.

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.

Strategies to enhance the graft versus tumour effect after allogeneic haematopoietic stem cell transplantation

Relapse of haematological malignancies after allogeneic haematopoietic stem cell transplant is a major cause of mortality. The immunological mechanisms that may lead to disease relapse may include immunological immaturity prior to reconstitution of the allogeneic immune system, tumour antigen downregulation or promotion of T-cell exhaustion by interactions with the tumour microenvironment. Current therapeutic strategies for post-transplant relapse are limited in their efficacy and alternative approaches are required. In this review, we discuss the mechanisms of T and NK-cell immune evasion that facilitate relapse of haematological malignancies after allogeneic stem cell transplantation, and explore emerging strategies to augment the allogeneic immune system in order to construct a more potent graft versus tumour response.

High Serum Level of Soluble Programmed Death Ligand 1 is Associated With a Poor Prognosis in Hodgkin Lymphoma

Blockade of the programmed cell death 1-programmed cell death ligand 1 pathway is a new and promising therapeutic approach in Hodgkin lymphoma (HL). To our knowledge, the impact of soluble programmed cell death ligand 1 (sPD-L1) serum levels on HL patient prognosis has not yet been investigated. In this study, the prognostic value of sPD-L1 was assessed in patients with HL. We measured serum sPD-L1 levels and identified their prognostic value in 108 newly diagnosed HL patients using an enzyme-linked immunosorbent assay (ELISA). We found higher serum sPD-L1 concentrations in HL patients than in healthy controls. The best sPD-L1 cutoff value for predicting disease progression risk was 25.1674 ng/ml. The 4-year progression-free survival (PFS) rates for the high-sPD-L1 and low-sPD-L1 groups were 78.8% and 93.3%, respectively. Multivariate survival analysis showed that advanced stage and higher sPD-L1 levels (>25.1674 ng/ml) were independent prognostic factors for shorter PFS. In addition, higher sPD-L1 levels were positively correlated with advanced stage and negatively correlated with peripheral blood monocyte number. The serum sPD-L1 level is an independent prognostic factor for PFS in HL patients and may allow identification of a subgroup of patients who require more intensive therapy and who may benefit from anti-PD-1 agents.

Immunotherapy for the Treatment of Hodgkin Lymphoma: An Evolving Paradigm

Classical Hodgkin lymphoma (cHL) is one of the most common lymphomas in the Western world. Although most patients are cured with standard first-line therapy, up to 20% of patients will have relapsed or refractory disease. Although the conventional approach to treatment has consisted of chemotherapy, radiation, and for those who relapse, autologous or allogeneic transplantation, newer approaches have become available in recent years, including immunoconjugates and checkpoint inhibitors. These approaches have shown significant efficacy in clinical trials and might be associated with fewer long-term toxicities compared with conventional therapies. In this review we discuss the biology of cHL as it pertains to the immunosuppressive tumor microenvironment and then review the existing clinical trial results of several emerging immunotherapies in this context, including immune checkpoint inhibitors and adoptive cellular therapy. Finally, several clinical practice issues pertaining to the use of immunotherapies are discussed.

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.

Investigational PD-1 inhibitors in HL and NHL and biomarkers for predictors of response and outcome

INTRODUCTION

Inhibitors against the PD-1/PD-L1 pathway are revolutionizing the treatment and management of malignancies.

AREAS COVERED

We summarize our current understanding of the function of PD-1, its role in immune evasion, the clinical data available that support the use of PD-1 antagonist in Hodgkin and non-Hodgkin lymphomas, and potential predictors of response.

EXPERT OPINION

We anticipate that in the next 10 years, agents that modulate the immune system such as PD-1 antagonists will be increasingly used in favor over traditional cytotoxic chemotherapeutic agents. PD-1 antagonists will be combined with future immunotherapies or used as adjuncts to cellular therapy to boost tumor-specific immune responses.

Increased Coexpression of PD-1, TIGIT, and KLRG-1 on Tumor-Reactive CD8+ T Cells During Relapse after Allogeneic Stem Cell Transplantation

Allogeneic stem cell transplantation (allo-SCT) can be a curative treatment for patients with a hematologic malignancy due to alloreactive T cell responses recognizing minor histocompatibility antigens (MiHA). Yet tumor immune escape mechanisms can cause failure of T cell immunity, leading to relapse. Tumor cells display low expression of costimulatory molecules and can up-regulate coinhibitory molecules that inhibit T cell functionality on ligation with their counter-receptors on the tumor-reactive T cells. The aim of this explorative study was to evaluate immune checkpoint expression profiles on T cell subsets and on cytomegalovirus (CMV)- and/or MiHA-reactive CD8⁺ T cells of allo-SCT recipients using a 13-color flow cytometry panel, and to correlate these expression patterns to clinical outcomes. MiHA-reactive CD8⁺ T cells exhibited an early differentiated CD27⁺⁺/CD28⁺⁺ phenotype with low KLRG-1 and CD57 expression. These T cells also displayed increased expression of PD-1, TIM-3, and TIGIT compared with total effector memory T cells and CMV-specific CD8⁺ T cells in healthy donors and allo-SCT recipients. Remarkably, high coexpression of PD-1, TIGIT, and KLRG-1 on MiHA-reactive CD8⁺ T cells was associated with relapse after allo-SCT. Taken together, these findings indicate that MiHA-specific CD8⁺ T cells of relapsed patients have a distinctive coinhibitory expression signature compared with patients who stay in remission. This phenotype may serve as a potential monitoring tool in patients. Moreover, these findings suggest that PD-1 and TIGIT play important roles in regulating T cell-mediated tumor control, providing a rationale for immunotherapy with blocking antibodies to treat relapse after allo-SCT.

Nivolumab for the Treatment of Classical Hodgkin Lymphoma

Objective: To review nivolumab for the treatment of classical Hodgkin lymphoma (cHL). Data Sources: Literature searches were conducted in Medline (1946 to May week 3 2017), EMBASE (1974 to 2017 week 22), and Google Scholar using the terms Hodgkin lymphoma AND nivolumab. Study Selection and Data Extraction: Two clinical trials (phase I and phase II) were identified. Data Synthesis: Nivolumab inhibits programmed death receptor-1 allowing for increased T-cell mediated immune surveillance of tumors. Nivolumab was evaluated in cHL patients after failure of autologous stem cell transplantation and brentuximab vedotin consolidation. Patients received nivolumab 3 mg/kg every 2 weeks. In the phase I trial, the objective response rate was 87% (95% confidence interval [CI] = 66-97) and the rate of progression-free survival (PFS) at 24 weeks was 86% (95% CI = 62-95). The most common adverse events (AE) included rash (22%) and decreased platelet count (17%). Following extended follow-up at a median of 86 weeks, 50% of the initial responders maintained a durable response. In the phase II clinical trial, 53 patients (66.3%, 95% CI = 54.8-76.4) achieved an objective response and PFS at 6 months was 76.9% (95% CI = 64.9-85.3). The common AE were fatigue (25%), infusion-related reactions (20%), and rash (16%). After further follow-up at a median of 15.4 months, 12-month overall survival was 94.9% (median overall survival not reached). Conclusions: Nivolumab is an effective option in treating patients with relapsed/refractory cHL with an acceptable safety profile. Further studies are needed to investigate the role of nivolumab for the treatment of cHL.

Advances in immunotherapy for pediatric acute myeloid leukemia

INTRODUCTION

Achieving better disease control in patients diagnosed with acute myeloid leukemia (AML) has proven challenging. Overall survival has been impacted by addressing treatment related mortality with focused supportive care measures. Despite this improvement, it remains difficult to induce durable leukemia remissions despite aggressive chemotherapeutic regimens. The addition of hematopoietic stem cell transplants (HSCT) has allowed further treatment intensification and provided the benefit of graft-versus-leukemia (GVL) effect. However, HSCT carries the risk of transplant related morbidities, particularly GVHD, and anti-tumor responsiveness is still suboptimal. Thus, there is a need for alternate therapies. Immunotherapy has the potential to address this need. Areas covered: Expert opinion: The elusiveness of an ideal surface antigen target together with an immunosuppressive leukemic microenvironment add to the already difficult challenge in developing AML-targeted immunotherapies. Though many hurdles remain, recent translational discovery and progressive clinical advances anticipate exciting future developments.

AREAS COVERED

This review highlights promises and challenges to immune-based therapies for AML. It aims to summarize immunotherapeutic strategies trialed in AML patients to date, inclusive of: antibodies, vaccines, and cellular therapy. It emphasizes those being used in the pediatric population, but also includes adult clinical trials and translational science that may ultimately extend to pediatric patients.

Emerging treatment options for the management of Hodgkin's lymphoma: clinical utility of nivolumab

Classical Hodgkin's lymphoma (cHL) is a B-cell malignancy comprised of pathologic Reed Sternberg cells with a surrounding immune-tolerant inflammatory milieu. RS cells evade immune recognition in part through programmed death ligand 1 (PD-L1) overexpression, which is genetically programmed through copy number alterations, polysomy, and amplification of the 9p24.1 locus encoding PD-L1. By engaging with PD-1+ T-cells, PD-L1 delivers a potent immune suppressive signal promoting immunologic escape of the tumor cell. Enhancing antitumor immune response by targeting PD-1 with the monoclonal antibody nivolumab has proved to be effective in multiple solid tumors, but the highest response rates to date have been reported in patients with cHL, with over 65% of treated patients achieving an objective clinical response. In this review, we will summarize the published evidence regarding the activity of nivolumab in cHL as well as its current place in therapy. We will review the pharmacology, mechanism of action, and side effects of nivolumab as well as the emerging data indicating possible increased risk of graft versus host disease in patients treated with PD-1 inhibitors either pre- or post-allogeneic stem cell transplant. Given the remarkable single-agent activity and safety profile of PD-1 inhibitors in heavily pretreated patients with cHL, the possibility of employing nivolumab in combination with other active agents and earlier in therapy is a promising area of active investigation, and we will briefly summarize current clinical trials.

PD-1 blockade for relapsed lymphoma post-allogeneic hematopoietic cell transplant: high response rate but frequent GVHD

Given the limited treatment options for relapsed lymphoma post-allogeneic hematopoietic cell transplantation (post-allo-HCT) and the success of programmed death 1 (PD-1) blockade in classical Hodgkin lymphoma (cHL) patients, anti-PD-1 monoclonal antibodies (mAbs) are increasingly being used off-label after allo-HCT. To characterize the safety and efficacy of PD-1 blockade in this setting, we conducted a multicenter retrospective analysis of 31 lymphoma patients receiving anti-PD-1 mAbs for relapse post-allo-HCT. Twenty-nine (94%) patients had cHL and 27 had ≥1 salvage therapy post-allo-HCT and prior to anti-PD-1 treatment. Median follow-up was 428 days (range, 133-833) after the first dose of anti-PD-1. Overall response rate was 77% (15 complete responses and 8 partial responses) in 30 evaluable patients. At last follow-up, 11 of 31 patients progressed and 21 of 31 (68%) remain alive, with 8 (26%) deaths related to new-onset graft-versus-host disease (GVHD) after anti-PD-1. Seventeen (55%) patients developed treatment-emergent GVHD after initiation of anti-PD-1 (6 acute, 4 overlap, and 7 chronic), with onset after a median of 1, 2, and 2 doses, respectively. GVHD severity was grade III-IV acute or severe chronic in 9 patients. Only 2 of these 17 patients achieved complete response to GVHD treatment, and 14 of 17 required ≥2 systemic therapies. In conclusion, PD-1 blockade in relapsed cHL allo-HCT patients appears to be highly efficacious but frequently complicated by rapid onset of severe and treatment-refractory GVHD. PD-1 blockade post-allo-HCT should be studied further but cannot be recommended for routine use outside of a clinical trial.