Current and emerging therapeutic strategies in adult T-cell leukemia-lymphoma

Adult T-cell leukemia-lymphoma (ATL) is classified into four clinical subtypes: acute, lymphoma, chronic, and smoldering. Chronic ATL is further divided into unfavorable and favorable chronic types according to serum lactate dehydrogenase, blood urea nitrogen, and serum albumin values. Acute, lymphoma, and unfavorable chronic types are categorized as aggressive ATL, whereas favorable chronic and smoldering types are categorized as indolent ATL. Intensive chemotherapy alone is not sufficient to prevent relapse of aggressive ATL. Allogeneic hematopoietic stem cell transplantation is a potential therapeutic option to cure aggressive ATL in younger patients. Reduced-intensity conditioning regimens have decreased transplantation-related mortality, and increased donor availability has dramatically improved transplant access. New agents, including mogamulizumab, brentuximab vedotin, tucidinostat, and valemetostat, have recently become available for patients with aggressive ATL in Japan. Here, I provide an overview of recent advances in therapeutic strategies for ATL.

[The results of a nationwide survey on patients with adult T-cell leukemia-lymphoma]

Adult T-cell leukemia-lymphoma (ATL) is a rare disease, and the nationwide surveys conducted in Japan have played an important role in improving our understanding of the clinical features and prognosis of this disease. The diagnostic criteria of clinical subtypes have been proposed based on the surveys conducted on patients with ATL who were diagnosed in the 1980s; the current treatment guideline in Japan is based on this classification of ATL subtypes. In the survey for patients diagnosed between 2000 and 2009, the usefulness of the clinical subtypes was confirmed, and soluble interleukin-2 receptor was identified as a new prognostic factor for chronic- and smoldering-type ATL. We conducted another survey for patients who were diagnosed in 2010 and 2011. The age at diagnosis was higher than that reported in previous trials, and the median patient age at diagnosis was 68 years in the study. The 4-year survival rate was better than that in previous studies on acute- and lymphoma-type disease; however, the prognosis has not improved in chronic- and smoldering-type disease. Further nationwide surveys are expected to improve the treatment strategies for ATL.

A decision analysis comparing unrelated bone marrow transplantation and cord blood transplantation in patients with aggressive adult T-cell leukemia-lymphoma

Patients with aggressive adult T-cell leukemia-lymphoma (ATL) have dismal outcomes with intensive chemotherapy. Early up-front allogeneic hematopoietic stem cell transplantation (allo-HSCT) is generally recommended. However, the choice of stem cell source, i.e., unrelated bone marrow transplant (UBMT) or cord blood transplantation (CBT), when an HLA-matched related donor is unavailable remains controversial. Thus, we undertook a decision analysis to compare the outcomes of two therapeutic strategies: chemotherapy followed by up-front UBMT at 6 months, and chemotherapy followed by up-front CBT at 3 months. Patients were stratified into low-, intermediate-, and high-risk groups according to the modified ATL-prognostic index. The model simulated life expectancy (LE) and quality-adjusted LE (QALE). LE following up-front UBMT was higher than that following up-front CBT in the low-risk group (2.63 vs. 2.28 years), but was comparable in the intermediate- (2.06 vs. 2.01 years) and high-risk groups (1.25 vs. 1.30 years). The Monte Carlo simulation for LE and QALE in each risk group showed that there was significant uncertainty in all categories. In conclusion, up-front UBMT was superior to up-front CBT in the low-risk group, but the strategies were comparable in the intermediate- and high-risk groups.

[Impact of pretransplant anti-CCR4 antibody administration on clinical outcomes in allogeneic hematopoietic stem cell transplantation]

Adult T-cell leukemia-lymphoma (ATL) is a peripheral T-cell lymphoma caused by human T-cell lymphotropic virus type I. Patients with aggressive ATL exhibit poor outcomes, even with dose-dense intensive chemotherapy. Thus, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered in all patients eligible for transplant. However, patients with aggressive ATL often have chemo-refractoriness or experience early relapse during chemotherapy. Allo-HSCT is often ineffective in patients with active disease status. Mogamulizumab (Moga) was approved in 2012 in Japan as a potent treatment option for patients with relapsed or refractory ATL. However, there is a major concern that the use of Moga before allo-HSCT could increase the risk of post-transplant complications, such as graft-versus-host disease (GVHD), because Moga depletes regulatory T cells. Here, we would like to describe the possible effects of pre-transplant Moga on post-transplant complications, such as acute GVHD, and to discuss how Moga could be efficiently incorporated in the treatment regimen of patients with aggressive ATL to maximize the expected clinical benefit.

Adult T-Cell Leukemia-Lymphoma

Adult T-cell leukemia-lymphoma (ATL) is a peripheral T-lymphocyte malignancy caused by an RNA retrovirus, human T-cell leukemia virus type 1. ATL is clinically classified into four disease subtypes. The acute, lymphoma type, and cases of the chronic type involving unfavorable prognostic factors are regarded as aggressive ATL subtypes that require immediate treatment. Dose-intensified chemotherapy, such as the VCAP-AMP-VECP regimen, is considered to be the most recommended treatment for aggressive ATL. However, ATL remains difficult to cure and has an extremely poor prognosis, even when such chemotherapy is employed. Allogeneic stem cell transplantation is the only known curative therapy and is recommended for younger patients with aggressive ATL. However, because of the increasing age at the onset of ATL, only a small fraction of patients with ATL can benefit from such transplants; therefore, there is an unmet medical need for novel drugs. Mogamulizumab, a defucosylated, humanized anti-C-C motif chemokine receptor 4 (CCR4) monoclonal antibody, was developed using a novel glycoengineering technique. Mogamulizumab monotherapy achieved clinically meaningful effects in patients with relapsed aggressive ATL and has exhibited acceptable toxicity profiles both inside and outside of Japan. In addition, lenalidomide has shown promising antitumor activity in patients with ATL. Furthermore, based on the results of translational research, several promising novel agents are currently being investigated and might contribute to improving the prognosis of ATL.

Phosphatidylinositol 3-kinase-δ (PI3K-δ) is a potential therapeutic target in adult T-cell leukemia-lymphoma

The prognosis of adult T-cell leukemia-lymphoma (ATL) remains very poor, and there is an urgent clinical need to investigate novel therapies for ATL. The expression of phosphatidylinositol 3-kinase-δ (PI3k-δ) is normally restricted to hematopoietic cells and is known as a key determinant of cell survival in certain cancers. The inhibitor of PI3k-δ, idelalisib, has been shown to be effective in the treatment of chronic lymphocytic leukemia. Here, we report the expression of PI3k-δ and the ability of idelalisib to promote apoptosis in ex vivo ATL samples. The activity of PI3K was quantified by a PI3-Kinase Activity ELISA kit. Although there was no significant difference in mean PI3K activity between healthy donors and patients with ATL, certain cases of ATL showed extremely high PI3K activities. The expression of PI3k-δ protein was detectable in most ATL cases. The freshly isolated cells from ATL patients were cultured with or without idelalisib for 0–10 days, and cell survival was then quantified. Idelalisib induced apoptosis in ATL cells in a time-dependent manner, and significantly reduced the frequency of viable ATL cells at 10 days. No time-dependent effects of idelalisib were observed in non-malignant T cells from the same patients. CCL22 has been reported to promote survival of ATL cells in part through the PI3K-AKT pathway. Idelalisib blocked this CCL22-induced phosphorylation of AKT and significantly inhibited the proliferation of ATL cells. These results validate the PI3K-AKT pathway as a potential therapeutic target in ATL.

[Long-term remission with mogamulizumab monotherapy in a patient with refractory adult T-cell leukemia-lymphoma]

A 73-year-old female with malaise, anorexia, and hydrodipsia was referred to our department. Peripheral blood tests revealed leukocytosis with 51% blast cells exhibiting flower-shaped nuclei. Flow-cytometry to detect tumor cells in peripheral blood indicated CD3+, CD4+, CD8-, and CD25- expression, but those in the lymph nodes expressed CD25+. Southern blots revealed clonal HTLV-1 provirus in the tumor cells, consistent with adult T-cell leukemia-lymphoma. Cytotoxic chemotherapy was ineffective, but eight cycles of mogamulizumab induced complete remission (CR). A relapse lesion appeared on the right breast but disappeared spontaneously. The patient has currently maintained CR for over five years.

Epidemiological and clinical features of adult T-cell leukemia-lymphoma in Japan, 2010-2011: A nationwide survey

Adult T-cell leukemia-lymphoma (ATL) is a mature T-cell malignancy associated with human T-cell leukemia virus type 1 (HTLV-1) infection. Japan is the most endemic country for HTLV-1 and ATL in the world. Recent nationwide studies of Japanese blood donors reported that HTLV-1 carriers spread from endemic areas to non-endemic areas. Therefore, the latest information on nationwide epidemiological and clinical data for ATL is necessary to guide clinical practice. We undertook a multicenter, hospital-based survey of newly diagnosed ATL patients from 2010 to 2011. A total of 996 patients with ATL were registered from 126 hospitals across Japan. Of those, 922 (487 men and 435 women) were included in the analysis. The median age at diagnosis was 68 years (interquartile range, 60-75 years). Overall, 67.2% of ATL was diagnosed in the Kyushu-Okinawa area. The most common subtype was acute (49.5%), followed by lymphoma (25.7%), chronic (14.2%), and smoldering (10.6%). Lymphoma type was more prevalent in men (60%), whereas chronic was more prevalent in women (60%). Half of patients with lymphoma type were aged over 70 years, whereas one-third of patients with the chronic type were aged under 60 years. All of these characteristics were different from those of the previous nationwide surveys in the 1980s and 1990s. This survey clarified that half of current patients with ATL are aged over 68 years who were unable to receive intensive cytotoxic therapies. New less toxic agents for aged patients and further strategies to prevent the development of ATL from HTLV-1 carrier status are needed.

Mogamulizumab for relapsed adult T-cell leukemia-lymphoma: Updated follow-up analysis of phase I and II studies

The present study sought to elucidate the prognosis of adult T‐cell leukemia–lymphoma (ATL) patients receiving mogamulizumab, a defucosylated anti‐CCR4 monoclonal antibody. Progression‐free survival (PFS) and overall survival (OS) of ATL patients enrolled in two studies are herein updated, namely NCT00355472 (phase I study of mogamulizumab in relapsed patients with ATL and peripheral T‐cell lymphoma) and NCT00920790 (phase II study for relapsed ATL). Of 13 patients with relapsed aggressive ATL in the phase I study, four (31%) survived >3 years. For 26 relapsed patients with aggressive ATL in the phase II study, median PFS was 5.2 months and 1‐year PFS was 26%, whereas median OS was 14.4 months, and 3‐year OS was 23%. For patients without a rash or who developed a grade 1 rash only, median PFS was 0.8 months, and 1‐year PFS was zero, with a median OS of 6.0 months, and 3‐year OS of 8%. In contrast, for patients who developed a rash ≥grade 2, median PFS was 11.7 months, and 1‐year PFS was 50%, with a median OS of 25.6 months, and 3‐year OS of 36%. Thus, we conclude that mogamulizumab monotherapy may improve PFS and OS in some patients with relapsed aggressive ATL, especially those who develop a skin rash as a moderate immune‐related adverse event. Therefore, further investigation is warranted to validate the present observations and to clarify the mechanisms involved in the activity of mogamulizumab.

Mogamulizumab for the treatment of relapsed or refractory adult T-cell leukemia-lymphoma

INTRODUCTION

Adult T-cell leukemia-lymphoma (ATL) is an aggressive variant of peripheral T-cell lymphoma of CD4+ T-malignant cells caused by human T-lymphotropic virus type-1. Despite aggressive treatment with multidrug combination chemotherapies, ATL confers a poor prognosis and commonly develops resistance to conventional treatments. Areas covered: Mogamulizumab is a humanized, defucosylated monoclonal antibody that acts by targeting the CC chemokine receptor 4 (CCR4) on malignant cells of ATL. In phase I and II clinical trials, it has achieved overall response rates of 31-50% in CCR4+ malignancies. The most commonly observed hematologic and non-hematologic adverse events included lymphocytopenia, neutropenia, leukocytopenia, infusion reaction, rash, and pyrexia. Expert commentary: Mogamulizumab has shown significant efficacy in treating ATL with moderately high response rates and has been approved in Japan for use in ATL. It may serve as a bridge therapy to achieve disease control prior to allogeneic hematopoietic stem cell transplantation. It also offers potential for use in combination with conventional chemotherapy. Determining the optimal combination of mogamulizumab with conventional and novel therapies remains an important strategy to improve the prognosis of patients with ATL.

Advanced human T-cell leukemia virus type 1 carriers and early-stage indolent adult T-cell leukemia-lymphoma are indistinguishable based on CADM1 positivity in flow cytometry

We previously reported that the cell adhesion molecule 1 (CADM1) versus CD7 plot in flow cytometry reflects disease progression in human T-cell leukemia virus type 1 (HTLV-1) infection. In CD4⁺ cells from peripheral blood, CADM1⁻CD7⁺ (P), CADM1⁺CD7^dim (D) and CADM1⁺CD7⁻ (N) subpopulations are observed. The D and N subpopulations increase as asymptomatic HTLV-1 carriers (AC) progress to indolent adult T-cell leukemia-lymphoma (ATL) and the N subpopulation then expands in aggressive ATL. In the present study we examined whether the analysis can estimate the risk of developing ATL in advanced AC. Peripheral blood samples from AC (N = 41) and indolent ATL patients (N = 19) were analyzed by flow cytometry using the CADM1 versus CD7 plot for CD4⁺ cells and inverse long PCR (clonality analysis) of FACS-sorted subpopulations. Almost all AC with a high HTLV-1 proviral load (>4 copies/100 cells) had a CADM1⁺ (D + N) frequency of >10%. AC with 25% < CADM1⁺ ≤ 50% contained expanded clones similar to smoldering-type ATL. In many patients in the 25% < CADM1⁺ ≤ 50% group, the proportion of abnormal lymphocytes was distributed around the 5% line, which divides AC and smoldering-type ATL in Shimoyama's classification. In conclusion, the CADM1 versus CD7 plot is useful for selection of putative high-risk AC. The characteristics of some AC and smoldering ATL are said to be similar; however, long-term follow up is required and the clinical outcome (e.g. rate of transformation) of these cases should be used to determine whether to include them in the same clinical category.

Recent advances in the treatment of adult T-cell leukemia-lymphomas

Recent advances in treatment for adult T-cell leukemia-lymphoma (ATL) are reviewed herein. It is currently possible to select a therapeutic strategy for ATL and predict prognosis by classification of patients by clinical subtypes and clinicopathological factors. Although the overall survival (OS) of patients with ATL has increased marginally because of advances in chemotherapy, further prolongation of survival might be difficult with conventional chemotherapy alone. Promising results have been reported for antiviral therapy using zidovudine and interferon-α, and, indeed, antiviral therapy is currently the standard treatment for patients with ATL in western countries. Remarkably, the 5-year OS rates are 100% for both the smoldering-type and chronic-type ATL. Recently, treatments for ATL have included allogeneic hematopoietic stem cell transplantation and molecular targeted therapies. Furthermore, the anti-CCR4 monoclonal antibody mogamulizumab has been shown to have marked cytotoxic effects on ATL cells, especially in the leukemic type of ATL. In the lymphoma type of ATL, the response rate may be improved by combining mogamulizumab with chemotherapy. It should be recognized that prevention of infection from carriers of human T-cell leukemia virus type-I and transfer of the virus from mother to infant are crucial issues for the eradication of ATL.

Heat shock protein 90 inhibitor NVP-AUY922 exerts potent activity against adult T-cell leukemia-lymphoma cells

Adult T-cell leukemia–lymphoma (ATL), an aggressive neoplasm etiologically associated with HTLV-1, is a chemoresistant malignancy. Heat shock protein 90 (HSP90) is involved in folding and functions as a chaperone for multiple client proteins, many of which are important in tumorigenesis. In this study, we examined NVP-AUY922 (AUY922), a second generation isoxazole-based non-geldanamycin HSP90 inhibitor, and confirmed its effects on survival of ATL-related cell lines. Analysis using FACS revealed that AUY922 induced cell-cycle arrest and apoptosis; it also inhibited the growth of primary ATL cells, but not of normal PBMCs. AUY922 caused strong upregulation of HSP70, a surrogate marker of HSP90 inhibition, and a dose-dependent decrease in HSP90 client proteins associated with cell survival, proliferation, and cell cycle in the G₁ phase, including phospho-Akt, Akt, IKKα, IKKβ, IKKγ, Cdk4, Cdk6, and survivin. Interestingly, AUY922 induced downregulation of the proviral integration site for Moloney murine leukemia virus (PIM) in ATL cells. The PIM family (PIM-1, -2, -3) is made up of oncogenes that encode a serine/threonine protein kinase family. As PIM kinases have multiple functions involved in cell proliferation, survival, differentiation, apoptosis, and tumorigenesis, their downregulation could play an important role in AUY922-induced death of ATL cells. In fact, SGI-1776, a pan-PIM kinase inhibitor, successfully inhibited the growth of primary ATL cells as well as ATL-related cell lines. Our findings suggest that AUY922 is an effective therapeutic agent for ATL, and PIM kinases may be a novel therapeutic target.

Antitumor effects of bevacizumab in a microenvironment-dependent human adult T-cell leukemia/lymphoma mouse model

OBJECTIVE

The objective of this study was to evaluate the therapeutic potential of bevacizumab with or without systemic chemotherapy for adult T-cell leukemia/lymphoma (ATL) and clarify the significance of angiogenesis for ATL pathogenesis.

METHODS

NOD/Shi-scid, IL-2Rγ(null) (NOG) mice were used as recipients of tumor cells from a patient with ATL, which engraft and proliferate in a microenvironment-dependent manner. The ATL cells could be serially transplanted in NOG mice, but could not be maintained in in vitro cultures.

RESULTS

Injection of bevacizumab alone significantly increased necrosis and decreased vascularization in the tumor tissue. Levels of human soluble interleukin two receptor in the serum (reflecting the ATL tumor burden) of bevacizumab-treated mice were significantly lower than in untreated mice. Although bevacizumab monotherapy showed these clear anti-angiogenesis effects, it did not prolong survival. In contrast, injection of bevacizumab together with cyclophosphamide, doxorubicin, vincristine, prednisolone (CHOP) led to a significant prolongation of survival of the ATL mice relative to CHOP alone.

CONCLUSIONS

This is the first report to evaluate the efficacy of bevacizumab for ATL in a tumor microenvironment-dependent model. Bevacizumab therapy combined with chemotherapy could be a valuable treatment strategy for that subgroup of ATL probably depending to a large extent on angiogenesis via vascular endothelial growth factor.