Nivolumab in patients with relapsed or refractory peripheral T-cell lymphoma: modest activity and cases of hyperprogression

Role of the crosstalk B:neoplastic T follicular helper (TFH) cells in the pathobiology of nodal TFH cell lymphomas

Angioimmunoblastic T cell lymphoma (AITL), the most common form of peripheral T cell lymphoma, originates from follicular helper T (Tfh) cells and is notably resistant to current treatments. The disease progression and maintenance, at least in early stages, are driven by a complex interplay between neoplastic Tfh and clusters of B-cells within the tumor microenvironment, mirroring the functional crosstalk observed inside germinal centers. This interaction is further complicated by recurrent mutations, such as TET2 and DNMT3A, which are present in both Tfh cells and B cells. These findings suggest that the symbiotic relationship between these two cell types could represent a therapeutic vulnerability. This review examines the key components and signaling mechanisms involved in the synapses between B cells and Tfh cells, emphasizing their significant role in the pathobiology of AITL and potential as therapeutic targets.

Higher tumor mutational burden and PD-L1 expression correlate with shorter survival in hematologic malignancies

Background

The prognostic implications of tumor mutational burden (TMB) and programmed death ligand 1 (PD-L1) expression are poorly studied in hematologic malignancies.

Objectives

This study aimed to better understand the characteristics and prognostic value of TMB and PD-1/PD-L1 in hematologic malignancies.

Design

This real-world study was conducted among patients with hematologic malignancies who had next-generation sequencing (NGS) (Foundation Medicine) at the University of California San Diego Moores Cancer Center (2014-2018).

Methods

TMB was measured by NGS. PD-L1 expression (tumor proportion score, TPS) was measured by immunohistochemistry (classified as high (⩾50%), low (1-49%), and negative (<1%)). Data was curated from the electronic medical records.

Results

In 388 evaluable patients, the most common diagnoses were B-cell non-Hodgkin lymphoma (NHL) (35%) and Philadelphia chromosome-negative myeloproliferative disorders (16%). Median TMB was 1.6 mutations/Mb (range, 0-46.83). Forty-eight patients (12%) had TMB ⩾10 mutations/Mb, 90% of which were B-cell or T-cell NHL. In 85 samples with available PD-L1 scores, 11 were high; 26, low; and 48, no tumor cell expression. PD-L1 TPS positive (⩾1%) was most common in T-cell NHL (7/9 (77%) cases) followed by B-cell NHL (21/51 (41%) cases). TMB ⩾4 mutations/Mb and PD-L1 score ⩾1% were significantly associated with shorter overall survival (OS) from diagnosis, with hazard ratio (HR) = 1.46 (p = 0.02, 95% confidence interval (CI) 1.05-2.03) and HR = 2.11 (p = 0.04, 95% CI 1.04-4.30), respectively; the relationship was more pronounced when PD-L1 ⩾50% versus <50% was used (HR = 2.80, p = 0.02, 95% CI 1.19-6.59). Higher TMB and higher PD-L1 positivity correlation were significant but weak (Pearson correlation coefficient R 2 = 0.04, p = 0.04).

Conclusion

TMB ⩾4 mutations/Mb and positive PD-L1 TPS are poor prognostic factors, correlating with shorter OS across hematologic malignancies.

Trial registration

ClinicalTrials.gov NCT02478931.

Immunobiology and treatment of cutaneous T-cell lymphoma

INTRODUCTION

Primary cutaneous T cell lymphomas (CTCL) are a heterogenous group of non-Hodgkin lymphomas derived from skin-homing T cells. These include mycosis fungoides and its leukemic variant Sezary syndrome, as well as the CD30+ lymphoproliferative disorders.

AREAS COVERED

In this review, we provide a summary of the current literature on CTCL, with a focus on the immunopathogenesis and treatment of mycosis fungoides and Sezary syndrome.

EXPERT OPINION

Recent advances in immunology have provided new insights into the biology of malignant T cells. This in turn has led to the development of new therapies that modulate the immune system to facilitate tumor clearance or target specific aspects of tumor biology.

Development of Subcutaneous Panniculitis-Like T-cell Lymphoma After Immune Checkpoint Inhibitor Treatment

Program death 1 (PD-1) inhibitors such as nivolumab are immune checkpoint inhibitors that have revolutionized the treatment of metastatic melanoma. Despite its success in treating melanoma, immune activation can lead to immune-related adverse effects, which are experienced by half of melanoma patients treated with PD-1 inhibitors. Despite the common frequency of immune-mediated adverse events, the development of a secondary lymphoma is exceedingly rare. We present the case of a 53-year-old woman diagnosed with stage IV metastatic melanoma, treated with nivolumab, who subsequently developed fatal subcutaneous panniculitis-like T-cell lymphoma (SPTCL).

Treatment strategies and outcome in relapsed peripheral T-cell lymphoma: results from the Netherlands Cancer Registry

ABSTRACT

Optimal treatment in patients with refractory or relapsed peripheral T-cell lymphomas (R/R T-NHLs) is unknown. In this population-based study, outcomes in R/R peripheral T-cell lymphoma not otherwise specified (PTCL NOS), angioimmunoblastic T-cell lymphoma (AITL), and anaplastic lymphoma kinase-positive (ALK+) and ALK-negative (ALK-) anaplastic large cell lymphoma (ALCL) were evaluated. Patients with PTCL NOS, AITL, ALK+ ALCL, and ALK- ALCL (≥18 years) diagnosed in 2014 to 2019 were identified using the Netherlands Cancer Registry. End points were overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). The 2-year PFS of 821 patients was 57%. Among 311 patients with a relapse, 243 received second-line treatment: 44% received salvage chemotherapy, 20% received brentuximab vedotin (BV), and 36% received other treatment. In third-line treatment, BV was most commonly used (38%). ORR after second-line treatment was 47%. Two-year PFS and OS after relapse were 25% and 34%, respectively. The risk of second relapse was negatively affected by early relapse (<12 months after diagnosis), whereas BV reduced this risk compared with salvage chemotherapy. Reduced risk of relapse was independent of histological subtype. The best outcomes were observed for patients treated with salvage chemotherapy receiving consolidative autologous and allogeneic stem cell transplantation (SCT) (2-year OS 68%), patients treated with BV achieving a second complete remission (2-year OS 74%) and patients with allogeneic SCT (2-year OS 60%). The risk of second relapse was significantly lower for patients with R/R T-NHL treated with BV compared with patients treated with salvage chemotherapy, and this was irrespective of subtype. Therefore, the use of salvage chemotherapy for patients with R/R T-NHL is challenged.

A combination of 5-azacytidine and nivolumab is a potentially effective rescue therapy in relapsed/refractory AITL

Introduction

Angioimmunoblastic T-cell lymphoma (AITL) is a peripheral T-cell lymphoma characterized by a T follicular helper cell phenotype expressing PD-1 (programmed cell death-1). AITL exhibits a poor response to conventional chemotherapy, with a median 5-year overall survival of 44% and a progression-free survival of 32%. Relapse is common, resulting in a median overall survival of 6 months. Recurrent mutations are detected in genes regulating DNA methylation, including TET2, DNMT3A, and IDH2 variants, along with the prevalent RHOA G17V mutation. In this context, patients treated with the hypomethylating agent 5-azacytidine achieved overall response and complete response rates of 75% and 41%, respectively. We hypothesized that targeted therapies combining anti-PD-1 checkpoint blockers with hypomethylating agents could be efficient in AITL patients and less toxic than standard chemotherapy.

Methods

Here, we report the efficacy of a regimen combining 5-azacytidine and nivolumab in nine relapsed or refractory AITL patients.

Results

This regimen was well-tolerated, especially in elderly patients. The overall response rate was 78%, including four partial responses (44%) and three complete responses (33%). Allogeneic hematopoietic stem cell transplantation was performed in two patients who reached complete response.

Discussion

These preliminary favorable results may serve as a basis for further investigation in prospective studies.

KLRG1 Cell Depletion as a Novel Therapeutic Strategy in Patients with Mature T-Cell Lymphoma Subtypes

PURPOSE

Develop a novel therapeutic strategy for patients with subtypes of mature T-cell and NK-cell neoplasms.

EXPERIMENTAL DESIGN

Primary specimens, cell lines, patient-derived xenograft models, commercially available, and proprietary anti-KLRG1 antibodies were used for screening, target, and functional validation.

RESULTS

Here we demonstrate that surface KLRG1 is highly expressed on tumor cells in subsets of patients with extranodal NK/T-cell lymphoma (ENKTCL), T-prolymphocytic leukemia (T-PLL), and gamma/delta T-cell lymphoma (G/D TCL). The majority of the CD8+/CD57+ or CD3-/CD56+ leukemic cells derived from patients with T- and NK-large granular lymphocytic leukemia (T-LGLL and NK-LGLL), respectively, expressed surface KLRG1. The humanized afucosylated anti-KLRG1 monoclonal antibody (mAb208) optimized for mouse in vivo use depleted KLRG1+ TCL cells by mechanisms of ADCC, ADCP, and CDC rather than apoptosis. mAb208 induced ADCC and ADCP of T-LGLL patient-derived CD8+/CD57+ cells ex vivo. mAb208 effected ADCC of subsets of healthy donor-derived KLRG1+ NK, CD4+, CD8+ Tem, and TemRA cells while sparing KLRG1- naïve and CD8+ Tcm cells. Treatment of cell line and TCL patient-derived xenografts with mAb208 or anti-CD47 mAb alone and in combination with the PI3K-δ/γ inhibitor duvelisib extended survival. The depletion of macrophages in vivo antagonized mAb208 efficacy.

CONCLUSIONS

Our findings suggest the potential benefit of a broader treatment strategy combining therapeutic antibodies with PI3Ki for the treatment of patients with mature T-cell and NK-cell neoplasms. See related commentary by Varma and Diefenbach, p. 2300.

Novel clinical risk stratification and treatment strategies in relapsed/refractory peripheral T-cell lymphoma

Peripheral T cell lymphoma (PTCL) represents a group of heterogeneous hematological malignancies, which are notoriously challenging to treat and outcomes are typically poor. Over the past two decades, clinical prognostic indices for patient risk stratification have evolved, while several targeted agents are now available to complement combination chemotherapy in the frontline setting or as a salvage strategy. With further understanding of the molecular pathobiology of PTCL, several innovative approaches incorporating immunomodulatory agents, epigenetic therapies, oncogenic kinase inhibitors and immunotherapeutics have come to the forefront. In this review, we provide a comprehensive overview of the progress in developing clinical prognostic indices for PTCL and describe the broad therapeutic landscape, emphasizing novel targetable pathways that have entered early phase clinical studies.

Regulatory T cells as crucial trigger and potential target for hyperprogressive disease subsequent to PD-1/PD-L1 blockade for cancer treatment

PD-1/PD-L1 blockade therapy has brought great success to cancer treatment. Nevertheless, limited beneficiary populations and even hyperprogressive disease (HPD) greatly constrain the application of PD-1/PD-L1 inhibitors in clinical treatment. HPD is a special pattern of disease progression with rapid tumor growth and even serious consequences of patient death, which requires urgent attention. Among the many predisposing causes of HPD, regulatory T cells (Tregs) are suspected because they are amplified in cases of HPD. Tregs express PD-1 thus PD-1/PD-L1 blockade therapy may have an impact on Tregs which leads to HPD. Tregs are a subset of CD4+ T cells expressing FoxP3 and play critical roles in suppressing immunity. Tregs migrate toward tumors in the presence of chemokines to suppress antitumor immune responses, causing cancer cells to grow and proliferate. Studies have shown that deleting Tregs could enhance the efficacy of PD-1/PD-L1 blockade therapy and reduce the occurrence of HPD. This suggests that immunotherapy combined with Treg depletion may be an effective means of avoiding HPD. In this review, we summarized the immunosuppressive-related functions of Tregs in antitumor therapy and focused on advances in therapy combining Tregs depletion with PD-1/PD-L1 blockade in clinical studies. Moreover, we provided an outlook on Treg-targeted HPD early warning for PD-1/PD-L1 blockade therapy.

TIGIT is Frequently Expressed in the Tumor Microenvironment of Select Lymphomas: Implications for Targeted Therapy

Immune checkpoint inhibitors against Programmed Cell Death Protein 1/Programmed Cell (PD-1/PD-L1) and CTLA-4/B7 axes have had limited success in hematologic malignancies, requiring the need to explore alternative targets such as T-cell immunoreceptor with Ig and ITIM domains (TIGIT)/CD155 to improve durable clinical responses. We undertook this study to investigate the expression profile of TIGIT such that the potential efficacy of TIGIT blockade could be mapped among lymphoma subtypes. We validated an immunohistochemical assay for TIGIT and evaluated its expression in lymphoma and tumor microenvironment (TME) cells in 661 lymphoma/leukemia biopsies. Multiplex immunofluorescence was used for correlation with normal TME cell subsets. Tumor or TME TIGIT-positivity was defined as moderate to strong membrane staining in at least 10% of tumor or TME cells, respectively. TME TIGIT expression was correlated with overall survival and progression-free survival and comparison with PD-L1 expression. In most cases, lymphoma cells were TIGIT-negative except for angioimmunoblastic and peripheral T-cell lymphomas, which showed 91% and 47% positivity, respectively. A high proportion of small B-cell lymphoma and anaplastic large cell lymphoma cases had TIGIT-positive TME cells. Chronic lymphocytic leukemia/small lymphocytic lymphoma patients with TIGIT-negative TME cells showed significantly shorter overall survival ( P =0.04). No other statistically significant differences were found. When TIGIT was expressed in TME cells, there were a comparable number of TIGIT-positive only and dual TIGIT/PD-L1 positive cases except for more TIGIT-positive only cases in CLL/SLL. TIGIT expression shows distinctive profiles among lymphoma subtypes. Chronic lymphocytic leukemia/small lymphocytic lymphoma and anaplastic large cell lymphoma demonstrated high TME TIGIT expression compared with PD-L1, with a high proportion of dual TIGIT and PD-L1-positivity. Our results are likely to contribute to the design and correlative study of therapeutic response in clinical trials targeting TIGIT alone or in combination with PD1/PDL1.

SOHO State-of-the-Art Updates and Next Questions: Treatment for Newly Diagnosed Peripheral T-Cell Lymphomas

Although a rare subset of non-Hodgkin lymphomas, peripheral T-cell lymphomas (PTCL) account for a disproportionate proportion of patient mortality. Conventional therapies are derived from experience treating aggressive B-cell lymphomas and center around CHOP-based chemotherapy. However, due to the unique biology and diverse subtypes of PTCL, most patients fail to durably respond to this approach and 5-year survival is only 20% to 30%. There have been multiple attempts to improve outcomes for patients with PTCL. Among the more successful strategies are the use of consolidative autologous stem cell transplant, the augmentation of CHOP with etoposide (CHOEP), and the use of brentuximab vedotin in CD30-positive PTCL. Advances in the understanding of histology-specific biology has cultivated enthusiasm to evaluate hypomethylating agents, histone deacetylate inhibitors, and phosphoinositol-3-kinase inhibitors in the frontline setting. Improvements in monitoring disease response and prognostication including the use of cell-free DNA, mutational profiling, and interim PET/CT imaging are also on the horizon. For patients with acute T-cell leukemia/lymphoma, the use of mogamulizumab-based therapy in the frontline setting may lead to advances in care. The true impact of these new-era therapies will only be elucidated as clinical practices incorporate the rapidly changing evidence.

Immune checkpoint blockade in hematological malignancies: current state and future potential

Malignant cells are known to evade immune surveillance by engaging immune checkpoints which are negative regulators of the immune system. By restoring the T-lymphocyte mediated anti-tumor effect, immune checkpoint inhibitors (ICI) have revolutionized the treatment of solid tumors but have met rather modest success in hematological malignancies. Currently, the only FDA approved indications for ICI therapy are in classic hodgkin lymphoma and primary mediastinal B cell lymphoma. Multiple clinical trials have assessed ICI therapy alone and in combination with standard of care treatments in other lymphomas, plasma cell neoplasms and myeloid neoplasms but were noted to have limited efficacy. These trials mostly focused on PD-1/PDL-1 and CTLA-4 inhibitors. Recently, there has been an effort to target other T-lymphocyte checkpoints like LAG-3, TIM-3, TIGIT along with improving strategies of PD-1/PDL-1 and CTLA-4 inhibition. Drugs targeting the macrophage checkpoint, CD47, are also being tested. Long term safety and efficacy data from these ongoing studies are eagerly awaited. In this comprehensive review, we discuss the mechanism of immune checkpoint inhibitors, the key takeaways from the reported results of completed and ongoing studies of these therapies in the context of hematological malignancies.

Past, present and future therapeutic approaches in nodal peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCL) encompass over 30 different entities and although they share post-thymic T- or NK-cell derivation, the disease biology and genomic landscape are very diverse across subtypes. In Western populations, nodal PTCL are the most frequently encountered entities in clinical practice and although important achievements have been made in deciphering the underlying biology and in therapeutic advances, there are still large gaps in disease understanding and clinical scenarios in which controversy over best practice continues. CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone)- based chemotherapy continues to be the 'standard' treatment, with the addition of brentuximab vedotin (BV) in the combination CHP (cyclosphosphamide, doxorubicin, prednisone)-BV representing a new treatment paradigm in CD30+ PTCL although its benefit is less certain in the non-anaplastic large cell lymphoma subtypes. Given the high risk of relapse, consolidative autologous stem cell transplant is considered in nodal PTCL, outside of ALK-positive anaplastic large cell lymphoma; however, in the absence of a randomized controlled trials, practices vary. Beyond CHP-BV, most study activity has focused on adding a novel agent to CHOP (i.e., CHOP + drug X). However, with high complete remission rates observed with some novel therapy combinations, these regimens are being tested in the front-line setting, with a particular rationale in follicular helper T-cell lymphomas which have a clear sensitivity to epigenetic modifying therapies. This is well exemplified in the relapsed/refractory setting in which rational combination therapies are being developed for specific subtypes or guided by underlying biology. Taken together, we have finally moved into an era of a more personalized approach to the management of nodal PTCL.

Advances in the pathogenesis and therapeutic strategies of angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive subtype of peripheral T-cell lymphomas with its cell origin determined to be follicular helper T-cells. AITL is characterized by a prominent tumor microenvironment involving dysregulation of immune cells, signaling pathways, and extracellular matrix. Significant progress has been made in the molecular pathophysiology of AITL, including genetic mutations, immune metabolism, hematopoietic-derived microenvironment, and non-hematopoietic microenvironment cells. Early diagnosis, detection of severe complications, and timely effective treatment are crucial for managing AITL. Treatment typically involves various combination chemotherapies, but the prognosis is often poor, and relapsed and refractory AITL remains challenging, necessitating improved treatment strategies. Therefore, this article provides an overview of the pathogenesis and latest advances in the treatment of AITL, with a focus on potential therapeutic targets, novel treatment strategies, and emerging immunotherapeutic approaches.

Angioimmunoblastic T-cell lymphoma: Novel recurrent mutations and prognostic biomarkers by cell-free DNA profiling

Molecular and clinical stratification of patients with angioimmunoblastic T-cell lymphoma (AITL) is unsatisfactory, which hinders the development of personalized therapies. This study aimed to identify molecular biomarkers for AITL based on peripheral cell-free DNA (cfDNA) that could be used to predict prognosis and guide treatment non-invasively. A customized panel containing 46 genes was used to study pretreatment cfDNA and paired tumour tissues in 64 Chinese AITL patients from three clinical centres, and gene mutations in cfDNA and tumour tissue were assessed for concordance (34 paired samples). Then, the association of gene mutations and prognosis was analysed, and a functional enrichment analysis was performed. The sequencing results showed good consistency between cfDNA samples and paired tissue samples. KDM5A, STAT1, FANCM, ERBB4, PIK3R5 and NSD1 were identified as novel recurrent mutations. Mutations in FANCM or combinations of RHOA, KDM5A and FAT1 were associated with poor prognosis. Additionally, functional analysis revealed that RHOAG17 might serve as a predictive biomarker of PD-1 blockade respondence. Our findings confirmed the role of cfDNA as a liquid biopsy in AITL, and revealed novel molecular determinants that can stratify patients and guide treatment options.

Clinical PD-1/PD-L1 Blockades in Combination Therapies for Lymphomas

Immunotherapy with the programmed cell death protein 1 (PD-1)/PD-1 ligand (PD-L1) blockade has revolutionized the treatment of advanced solid cancers. However, these clinical benefits have been limited to cases of malignant lymphomas, showing promising results for only classic Hodgkin lymphoma (cHL) and primary mediastinal B-cell lymphoma (PMBCL). To bring clinical benefits to more patients with lymphoma, numerous combination therapies involving PD-1/PD-L1 blockade have been tested in clinical trials in both frontline and relapsed/refractory settings. This article reviews the current landscape of combination therapies with PD-1/PD-L1 blockade for lymphoma and discusses the potential therapeutic approaches. An interim analysis of a phase 3 study demonstrated increased progression-free survival with nivolumab combination therapy over the current frontline treatment in patients with advanced-stage cHL. The results of combination therapies for aggressive B-cell lymphomas, except for PMBCL, have been disappointing. Several clinical trials of combined PD-1/PD-L1 blockade and Bruton's tyrosine kinase inhibitors are exploring its efficacy in patients with chronic lymphocytic leukemia (CLL) with Richter transformation. Several T-cell lymphoma subtypes respond to PD-1/PD-L1 blockade monotherapy. Further clinical trials are underway to investigate appropriate combination regimens with PD-1/PD-L1 blockade, especially for cHL, CLL with Richter transformation, and T-cell lymphoma, in both frontline and relapsed/refractory settings.

Checkpoint inhibition in hematologic malignancies

Checkpoint inhibitor therapy has emerged as an effective therapeutic strategy for many types of malignancies, especially in solid tumors. Within the last two decades, numerous monoclonal antibody drugs targeting the CTLA-4 and PD-1/PD-L1 checkpoint pathways have seen FDA approval. Within hematologic malignancies, Hodgkin Lymphoma has seen the greatest clinical benefits thus far with more recent data showing efficacy in the front-line setting. As our understanding of checkpoint inhibition expands, using these pathways as a therapeutic target has shown some utility in the treatment of other hematologic malignancies as well, primarily in the relapsed/refractory settings. Checkpoint inhibition also appears to have a role as a synergistic agent to augment clinical responses to other forms of therapy such as hematopoietic stem cell transplant. Moreover, alternative checkpoint molecules that bypass the well-studied CTLA-4 and PD-1/PD-L1 pathways have emerged as exciting new therapeutic targets. Most excitingly is the use of anti-CD47 blockade in the treatment of high risk MDS and TP-53 mutated AML. Overall, there has been tremendous progress in understanding the benefits of checkpoint inhibition in hematologic malignancies, but further studies are needed in all areas to best utilize these agents. This is a review of the most recent developments and progress in Immune Checkpoint Inhibition in Hematologic Malignancies in the last decade.

A phase 2 study of pembrolizumab after autologous stem cell transplantation in patients with T-cell non-Hodgkin lymphoma

Autologous stem cell transplantation (ASCT) is often used as consolidation for several subtypes of peripheral T-cell lymphoma (PTCL) in first remission. However, many patients relapse after ASCT and have a very poor prognosis. There are no approved treatment options for posttransplantation maintenance or consolidation in PTCL. PD-1 blockade has demonstrated some efficacy for patients with PTCL. We, therefore, conducted a phase 2 multicenter study of the anti-PD-1 monoclonal antibody pembrolizumab after ASCT in patients with PTCL in first remission. Pembrolizumab was administered at 200 mg IV every 3 weeks for up to 8 cycles within 21 days from post-ASCT discharge (and within 60 days of stem cell infusion). The primary end point was progression-free survival (PFS) at 18 months after ASCT. Twenty-one patients were treated in this study and 67% (n = 14) completed 8 cycles of treatment. Among all patients who were evaluable, 13 of 21 were alive and achieved PFS at 18 months after ASCT, meeting the study's primary end point. The estimated 18-month PFS was 83.6% (95% confidence interval [CI], 68-100), and overall survival 94.4% (95% CI, 84-100). The toxicity profile was consistent with the known toxicity profile of pembrolizumab, with no grade 5 toxicities. In conclusion, PD-1 blockade after ASCT with pembrolizumab is feasible with a favorable safety profile and promising activity, supporting further confirmatory studies. This trial was registered at www.clinicaltrials.gov as #NCT02362997.

SOHO State of the Art Updates and Next Questions | New Pathways and New Targets in PTCL: Staying on Target

While the peripheral T-cell lymphomas (PTCL) remain a therapeutic challenge, and increasingly account for a disproportionate number of lymphoma-related deaths, improved understanding of disease pathogenesis and classification, and the development of novel therapeutic agents over the past decade, all provide reasons for a more optimistic outlook in the next. Despite their genetic and molecular heterogeneity, many PTCL are dependent upon signaling input provided by antigen, costimulatory, and cytokine receptors. While gain-of-function alterations effecting these pathways are recurrently observed in many PTCL, more often than not, signaling remains ligand-and tumor microenvironment (TME)-dependent. Consequently, the TME and its constituents are increasingly recognized as "on target". Utilizing a "3 signal" model, we will review new-and old-therapeutic targets that are relevant for the more common nodal PTCL subtypes.

Nodal peripheral T-cell lymphoma: Chemotherapy-free management, are we there yet?

Peripheral T-cell lymphomas (PTCLs) are a diverse and uncommon type of lymphoid malignancies with a dismal prognosis. Recent advances in genomic studies have shown recurring mutations that are changing our knowledge of the disease's molecular genetics and pathogenesis. As such, new targeted therapies and treatments to improve disease outcomes are currently being explored. In this review, we discussed the current understanding of the nodal PTCL biology with potential therapeutic implications and gave our insights on the promising novel therapies that are currently under study such as immunotherapy, chimeric antigen receptor T-cell therapy, and oncolytic virotherapy.

Rapid T-cell lymphoma progression associated with immune checkpoint inhibitors

INTRODUCTION

Immune checkpoint inhibitors (ICIs) are widely used for multiple types of malignancies and are considered the fourth pillar in cancer treatment. Anti-programmed death-1 (PD-1) antibodies pembrolizumab and nivolumab are approved for relapsed/refractory classical Hodgkin lymphoma. Nonetheless, two phase 2 trials for T-cell lymphoma were terminated because of hyperprogression after a single dose in some patients.

AREAS COVERED

In this review, we summarize available information on the rapid progression of peripheral T-cell lymphoma including adult T-cell leukemia/lymphoma (ATLL).

EXPERT OPINION

In the abovementioned two trials, disease subtypes in patients who experienced hyperprogression were mostly ATLL or angioimmunoblastic T-cell lymphoma. Possible hyperprogression mechanisms induced by PD-1 blockade are the compensatory upregulation of the expression of other checkpoints, altered expression of lymphoma-promoting growth factors, functional blockade of stromal PD-ligand 1 acting as a tumor suppressor, and unique immune environment in indolent ATLL. The differentiation between hyperprogression and pseudoprogression is practically essential. There are no established methods to predict hyperprogression before administration of an ICI. In the future, the progress of novel diagnostic modalities such as positron emission tomography with computed tomography and circulating tumor DNA is expected to facilitate early cancer detection.

Education and Empowering Special Forces to Eradicate Secret Defectors: Immune System-Based Treatment Approaches for Mature T- and NK-Cell Malignancies

Mature T- and NK-cell leukemia/lymphoma (MTCL/L) constitute a heterogeneous group of, currently, 30 distinct neoplastic entities that are overall rare, and all present with a challenging molecular markup. Thus, so far, the use of first-line cancer treatment modalities, including chemotherapies, achieve only limited clinical responses associated with discouraging prognoses. Recently, cancer immunotherapy has evolved rapidly, allowing us to help patients with, e.g., solid tumors and also relapsed/refractory B-cell malignancies to achieve durable clinical responses. In this review, we systematically unveiled the distinct immunotherapeutic approaches available, emphasizing the special impediments faced when trying to employ immune system defense mechanisms to target 'one of their own-gone mad'. We summarized the preclinical and clinical efforts made to employ the various platforms of cancer immunotherapies including antibody-drug conjugates, monoclonal as well as bispecific antibodies, immune-checkpoint blockades, and CAR T cell therapies. We emphasized the challenges to, but also the goals of, what needs to be done to achieve similar successes as seen for B-cell entities.

Hyperprogression of cutaneous T cell lymphoma after anti-PD-1 treatment

BACKGROUNDImmune checkpoint blockade is an emerging treatment for T cell non-Hodgkin's lymphoma (T-NHL), but some patients with T-NHL have experienced hyperprogression with undetermined mechanisms upon anti-PD-1 therapy.METHODSSingle-cell RNA-Seq, whole-genome sequencing, whole-exome sequencing, and functional assays were performed on primary malignant T cells from a patient with advanced cutaneous T cell lymphoma who experienced hyperprogression upon anti-PD-1 treatment.RESULTSThe patient was enrolled in a clinical trial of anti-PD-1 therapy and experienced disease hyperprogression. Single-cell RNA-Seq revealed that PD-1 blockade elicited a remarkable activation and proliferation of the CD4+ malignant T cells, which showed functional PD-1 expression and an exhausted status. Further analyses identified somatic amplification of PRKCQ in the malignant T cells. PRKCQ encodes PKCθ; PKCθ is a key player in the T cell activation/NF-κB pathway. PRKCQ amplification led to high expressions of PKCθ and p-PKCθ (T538) on the malignant T cells, resulting in an oncogenic activation of the T cell receptor (TCR) signaling pathway. PD-1 blockade in this patient released this signaling, derepressed the proliferation of malignant T cells, and resulted in disease hyperprogression.CONCLUSIONOur study provides real-world clinical evidence that PD-1 acts as a tumor suppressor for malignant T cells with oncogenic TCR activation.TRIAL REGISTRATIONClinicalTrials.gov (NCT03809767).FUNDINGThe National Natural Science Foundation of China (81922058), the National Science Fund for Distinguished Young Scholars (T2125002), the National Science and Technology Major Project (2019YFC1315702), the National Youth Top-Notch Talent Support Program (283812), and the Peking University Clinical Medicine plus X Youth Project (PKU2019LCXQ012) supported this work.

Advances in the Study of Hyperprogression of Different Tumors Treated with PD-1/PD-L1 Antibody and the Mechanisms of Its Occurrence

Immune checkpoint inhibitors (ICIs) including PD-1/PD-L1 antibodies, have demonstrated significant clinical benefits in the treatment of individuals with many types of cancer. However, as more and more patients use such therapies, the side effects of immune checkpoint inhibitors have also been discovered. These include accelerated tumor growth in some patients, creating new lesions, and even life-threatening ones. These side effects are known as hyperprogression disease (HPD), and different types of tumors have different HPD conditions after ICIs treatment. Therefore, understanding the pathogenesis of HPD and predicting its occurrence is critical for patients using ICIs therapy. Here, we will briefly review the current status of PD-1/PD-L1 antibody therapy, HPD occurrence in various types of tumors, and the underlying mechanism.

PD-1/PD-L1 and DNA Damage Response in Cancer

The application of immunotherapy for cancer treatment is rapidly becoming more widespread. Immunotherapeutic agents are frequently combined with various types of treatments to obtain a more durable antitumor clinical response in patients who have developed resistance to monotherapy. Chemotherapeutic drugs that induce DNA damage and trigger DNA damage response (DDR) frequently induce an increase in the expression of the programmed death ligand-1 (PD-L1) that can be employed by cancer cells to avoid immune surveillance. PD-L1 exposed on cancer cells can in turn be targeted to re-establish the immune-reactive tumor microenvironment, which ultimately increases the tumor's susceptibility to combined therapies. Here we review the recent advances in how the DDR regulates PD-L1 expression and point out the effect of etoposide, irinotecan, and platinum compounds on the anti-tumor immune response.

Emerging predictive biomarkers for novel therapeutics in peripheral T-cell and natural killer/T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) and natural killer/T-cell lymphoma (NKTCL) are rare subtypes of non-Hodgkin's lymphoma that are typically associated with poor treatment outcomes. Contemporary first-line treatment strategies generally involve the use of combination chemoimmunotherapy, radiation and/or stem cell transplant. Salvage options incorporate a number of novel agents including epigenetic therapies (e.g. HDAC inhibitors, DNMT inhibitors) as well as immune checkpoint inhibitors. However, validated biomarkers to select patients for individualized precision therapy are presently lacking, resulting in high treatment failure rates, unnecessary exposure to drug toxicities, and missed treatment opportunities. Recent advances in research on the tumor and microenvironmental factors of PTCL and NKTCL, including alterations in specific molecular features and immune signatures, have improved our understanding of these diseases, though several issues continue to impede progress in clinical translation. In this Review, we summarize the progress and development of the current predictive biomarker landscape, highlight potential knowledge gaps, and discuss the implications on novel therapeutics development in PTCL and NKTCL.

Therapeutic Advances in Relapsed and Refractory Peripheral T-Cell Lymphoma

Historic outcomes for patients with relapsed or refractory nodal-based T-cell lymphomas are poor, with survival generally measured in months in multiple reports from the late 20th and early 21st century. Until recently, salvage strategies have mostly been borrowed from other aggressive lymphomas. However, dedicated investigations into the pathogenesis of T-cell lymphomas have resulted in an outpouring of therapies that target these diseases in biologically rational strategies. In particular, an evolving appreciation of the multiple complex oncogenic pathways and epigenetic changes that underlie these diseases has led to numerous agents targeting these aberrancies. Moreover, large reports of salvage allogeneic stem cell transplants in T-cell lymphoma have now been published, showing that adaptive immunotherapy is a potentially curative strategy for patients with relapsed or refractory disease. This review highlights therapeutic advances for relapsed or refractory T-cell lymphomas, including cellular therapy and allogeneic stem cell transplant, and provides a framework for management.

Harnessing the immune system in the treatment of cutaneous T cell lymphomas

Cutaneous T cell lymphomas are a rare subset of non-Hodgkin's lymphomas with predilection for the skin with immunosuppressive effects that drive morbidity and mortality. We are now appreciating that suppression of the immune system is an important step in the progression of disease. It should come as no surprise that therapies historically and currently being used to treat these cancers have immune modulating functions that impact disease outcomes. By understanding the immune effects of our therapies, we may better develop new agents that target the immune system and improve combinatorial treatment strategies to limit morbidity and mortality of these cancers. The immune modulating effect of therapeutic drugs in use and under development for cutaneous T cell lymphomas will be reviewed.

Resistance mechanisms of immune checkpoint inhibition in lymphoma: Focusing on the tumor microenvironment

Immune checkpoint inhibitors (ICIs) have revolutionized the therapeutic strategies of multiple types of malignancies including lymphoma. However, efficiency of ICIs varies dramatically among different lymphoma subtypes, and durable response can only be achieved in a minority of patients, thus requiring unveiling the underlying mechanisms of ICI resistance to optimize the individualized regimens and improve the treatment outcomes. Recently, accumulating evidence has identified potential prognostic factors for ICI therapy, including tumor mutation burden and tumor microenvironment (TME). Given the distinction between solid tumors and hematological malignancies in terms of TME, we here review the clinical updates of ICIs for lymphoma, and focus on the underlying mechanisms for resistance induced by TME, which play important roles in lymphoma and remarkably influence its sensitivity to ICIs. Particularly, we highlight the value of multiple cell populations (e.g., tumor infiltrating lymphocytes, M2 tumor-associated macrophages, and myeloid-derived suppressor cells) and metabolites (e.g., indoleamine 2, 3-dioxygenase and adenosine) in the TME as prognostic biomarkers for ICI response, and also underline additional potential targets in immunotherapy, such as EZH2, LAG-3, TIM-3, adenosine, and PI3Kδ/γ.

Plasmacytic Pleural Effusion as a Major Presentation of Angioimmunoblastic T-Cell Lymphoma: A Case Report

Angioimmunoblastic T-cell lymphoma is one of the peripheral T-cell lymphomas. Reactive plasma cells can occasionally be observed in AITL patients' peripheral blood and bone marrow. Plasmacytic pleural effusion as the presentation of AITL has not been reported before. The mechanisms of plasmacytic pleural effusion are not fully understood. Here we present an 82-year-old male with exuberant plasma cells in his pleural effusion in addition to his peripheral blood and bone marrow aspiration. By presenting this case, we would like to expand the spectrum of disease presentations in AITL and discuss the significance of flow cytometry in the differential diagnosis of pleural effusion. To our knowledge, this is the first case report in the literature, which will be crucial to assist the hematopathologist in accurate diagnosis and treatment.