Myeloid/natural killer (NK) cell precursor acute leukemia as a distinct leukemia type.

Myeloid/natural killer (NK) cell precursor acute leukemia (MNKPL) has been described on the basis of its unique immunophenotype and clinical phenotype. However, there is no consensus on the characteristics for identifying this disease type because of its rarity and lack of defined distinctive molecular characteristics. In this study, multiomics analysis revealed that MNKPL is distinct from acute myeloid leukemia, T cell acute lymphoblastic leukemia, and mixed-phenotype acute leukemia (MPAL), and NOTCH1 and RUNX3 activation and BCL11B down-regulation are hallmarks of MNKPL. Although NK cells have been classically considered to be lymphoid lineage-derived, the results of our single-cell analysis using MNKPL cells suggest that NK cells and myeloid cells share common progenitor cells. Treatment outcomes for MNKPL are unsatisfactory, even when hematopoietic cell transplantation is performed. Multiomics analysis and in vitro drug sensitivity assays revealed increased sensitivity to l-asparaginase and reduced levels of asparagine synthetase (ASNS), supporting the clinically observed effectiveness of l-asparaginase.

Humanized mouse models for immuno-oncology research.

Immunotherapy has emerged as a promising treatment paradigm for many malignancies and is transforming the drug development landscape. Although immunotherapeutic agents have demonstrated clinical efficacy, they are associated with variable clinical responses, and substantial gaps remain in our understanding of their mechanisms of action and specific biomarkers of response. Currently, the number of preclinical models that faithfully recapitulate interactions between the human immune system and tumours and enable evaluation of human-specific immunotherapies in vivo is limited. Humanized mice, a term that refers to immunodeficient mice co-engrafted with human tumours and immune components, provide several advantages for immuno-oncology research. In this Review, we discuss the benefits and challenges of the currently available humanized mice, including specific interactions between engrafted human tumours and immune components, the development and survival of human innate immune populations in these mice, and approaches to study mice engrafted with matched patient tumours and immune cells. We highlight the latest advances in the generation of humanized mouse models, with the aim of providing a guide for their application to immuno-oncology studies with potential for clinical translation.

Multi-omics analysis defines highly refractory RAS burdened immature subgroup of infant acute lymphoblastic leukemia.

KMT2A-rearranged infant acute lymphoblastic leukemia (ALL) represents the most refractory type of childhood leukemia. To uncover the molecular heterogeneity of this disease, we perform RNA sequencing, methylation array analysis, whole exome and targeted deep sequencing on 84 infants with KMT2A-rearranged leukemia. Our multi-omics clustering followed by single-sample and single-cell inference of hematopoietic differentiation establishes five robust integrative clusters (ICs) with different master transcription factors, fusion partners and corresponding stages of B-lymphopoietic and early hemato-endothelial development: IRX-type differentiated (IC1), IRX-type undifferentiated (IC2), HOXA-type MLLT1 (IC3), HOXA-type MLLT3 (IC4), and HOXA-type AFF1 (IC5). Importantly, our deep mutational analysis reveals that the number of RAS pathway mutations predicts prognosis and that the most refractory subgroup of IC2 possesses 100% frequency and the heaviest burden of RAS pathway mutations. Our findings highlight the previously under-appreciated intra- and inter-patient heterogeneity of KMT2A-rearranged infant ALL and provide a rationale for the future development of genomics-guided risk stratification and individualized therapy.

Circulating CD34+ cells of primary myelofibrosis patients contribute to myeloid-dominant hematopoiesis and bone marrow fibrosis in immunodeficient mice.

INTRODUCTION: Primary myelofibrosis (PMF) is a clonal stem cell disorder characterized by myeloid dominant hematopoiesis and dysregulated proliferation of fibroblasts in the bone marrow. However, how these aberrant myeloid cells and fibroblasts are produced remains unclear. AIM AND METHODS: In this study, we examined in vivo engraftment kinetics of PMF patient-derived CD34+ cells in immunecompromised NOD/SCID/IL2rgKO (NSG) mice. Engrafted human cells were analyzed with flow cytometry, and proliferation of fibroblastic cells and bone marrow fibrosis were assessed with the histo-pathological examination. RESULTS: Transplantation of PMF patient-derived circulating CD34+ fractions into NSG newborns recapitulates clinical features of human PMF. Engraftment of human CD45+ leukocytes resulted in anemia and myeloid hyperplasia accompanied by bone marrow fibrosis by six months post-transplantation. Fibrotic bone marrow contained CD45-vimentin+ cells of both human and mouse origin, suggesting that circulating malignant CD34+ subsets contribute to myelofibrotic changes in PMF through direct and indirect mechanisms. CONCLUSION: A patient-derived xenotransplantation (PDX) model of PMF allows in vivo examination of disease onset and propagation originating from immature CD34+ cells and will support the investigation of pathogenesis and development of therapeutic modalities for the disorder.

[Performing integrative transcriptomic and chemical screening to identify patient-specific vulnerabilities in poor-prognosis acute myeloid leukemia].

Genetic complexity and heterogeneity have made drug discovery difficult in human malignancies. In the past few years, we aimed to find vulnerabilities in therapy-resistant and refractory acute myeloid leukemia (AML) through integrative analyses of genomic data, clinical information, and results from in vivo/in vitro cell biological assays. Through analyses, we found that the cells of patients with AML show distinct sensitivity/resistance to small inhibiting molecules for anti-apoptosis and cell cycle/division. In particular, AML cells harboring the IDH1/2 mutations were highly sensitive to BCL-2 inhibition, while inhibition of IAP proteins resulted in efficient elimination of AML cells with varied FLT3, NRAS, and CBL mutations. Linking AML-initiating events with appropriate therapeutic strategies through cellular and genomic analyses might be further translated into nonmyeloid malignancies and solid tumors in the future.

Targeting critical kinases and anti-apoptotic molecules overcomes steroid resistance in MLL-rearranged leukaemia.

BACKGROUND: Acute lymphoblastic leukaemia with mixed lineage leukaemia gene rearrangement (MLL-ALL) frequently affects infants and is associated with a poor prognosis. Primary refractory and relapsed disease due to resistance to glucocorticoids (GCs) remains a substantial hurdle to improving clinical outcomes. In this study, we aimed to overcome GC resistance of MLL-ALL. METHODS: Using leukaemia patient specimens, we performed bioinformatic analyses to identify target genes/pathways. To test inhibition of target pathways in vivo, we created pre-clinical therapeutic mouse patient-derived xenograft (PDX)-models by transplanting human MLL-ALL leukaemia initiating cells (LIC) into immune-deficient NSG mice. Finally, we conducted B-cell lymphoma-2 (BCL-2) homology domain 3 (BH3) profiling to identify BH3 peptides responsible for treatment resistance in MLL-leukaemia. FINDINGS: Src family kinases (SFKs) and Fms-like tyrosine kinase 3 (FLT3) signaling pathway were over-represented in MLL-ALL cells. PDX-models of infant MLL- ALL recapitulated GC-resistance in vivo but RK-20449, an inhibitor of SFKs and FLT3 eliminated human MLL-ALL cells in vivo, overcoming GC-resistance. Further, we identified BCL-2 dependence as a mechanism of treatment resistance in MLL-ALL through BH3 profiling. Furthermore, MLL-ALL cells resistant to RK-20449 treatment were dependent on the anti-apoptotic BCL-2 protein for their survival. Combined inhibition of SFKs/FLT3 by RK-20449 and of BCL-2 by ABT-199 led to substantial elimination of MLL-ALL cells in vitro and in vivo. Triple treatment combining GCs, RK-20449 and ABT-199 resulted in complete elimination of MLL-ALL cells in vivo. INTERPRETATION: SFKs/FLT3 signaling pathways are promising targets for treatment of treatment-resistant MLL-ALL. Combined inhibition of these kinase pathways and anti-apoptotic BCL-2 successfully eliminated highly resistant MLL-ALL and demonstrated a new treatment strategy for treatment-resistant poor-outcome MLL-ALL. FUNDING: This study was supported by RIKEN (RIKEN President's Discretionary Grant) for FI, Japan Agency for Medical Research and Development (the Basic Science and Platform Technology Program for Innovative Biological Medicine for FI and by NIH CA034196 for LDS. The funders had no role in the study design, data collection, data analysis, interpretation nor writing of the report.

Combined inhibition of XIAP and BCL2 drives maximal therapeutic efficacy in genetically diverse aggressive acute myeloid leukemia.

Aggressive therapy-resistant and refractory acute myeloid leukemia (AML) has an extremely poor outcome. By analyzing a large number of genetically complex and diverse, primary high-risk poor-outcome human AML samples, we identified specific pathways of therapeutic vulnerability. Through drug screens followed by extensive in vivo validation and genomic analyses, we found inhibition of cytosolic and mitochondrial anti-apoptotic proteins XIAP, BCL2 and MCL1, and a key regulator of mitosis, AURKB, as a vulnerability hub based on patient-specific genetic aberrations and transcriptional signatures. Combinatorial therapeutic inhibition of XIAP with an additional patient-specific vulnerability eliminated established AML in vivo in patient-derived xenografts (PDXs) bearing diverse genetic aberrations, with no signs of recurrence during off-treatment follow-up. By integrating genomic profiling and drug-sensitivity testing, this work provides a platform for a precision-medicine approach for treating aggressive AML with high unmet need.

Understanding Normal and Malignant Human Hematopoiesis Using Next-Generation Humanized Mice.

Rodent models for human diseases contribute significantly to understanding human physiology and pathophysiology. However, given the accelerating pace of drug development, there is a crucial need for in vivo preclinical models of human biology and pathology. The humanized mouse is one tool to bridge the gap between traditional animal models and the clinic. The development of immunodeficient mouse strains with high-level engraftment of normal and diseased human immune/hematopoietic cells has made in vivo functional characterization possible. As a patient-derived xenograft (PDX) model, humanized mice functionally correlate putative mechanisms with in vivo behavior and help to reveal pathogenic mechanisms. Combined with single-cell genomics, humanized mice can facilitate functional precision medicine such as risk stratification and individually optimized therapeutic approaches.

TEG011 persistence averts extramedullary tumor growth without exerting off-target toxicity against healthy tissues in a humanized HLA-A*24:02 transgenic mice.

γδT cells play an important role in cancer immunosurveillance and are able to distinguish malignant cells from their healthy counterparts via their γδTCR. This characteristic makes γδT cells an attractive candidate for therapeutic application in cancer immunotherapy. Previously, we have identified a novel CD8α-dependent tumor-specific allo-HLA-A*24:02-restricted Vγ5Vδ1TCR with potential therapeutic value when used to engineer αßT cells from HLA-A*24:02 harboring individuals. αßT cells engineered to express this defined Vγ5Vδ1TCR (TEG011) have been suggested to recognize spatial changes in HLA-A*24:02 present selectively on tumor cells but not their healthy counterparts. However, in vivo efficacy and toxicity studies of TEG011 are still limited. Therefore, we extend the efficacy and toxicity studies as well as the dynamics of TEG011 in vivo in a humanized HLA-A*24:02 transgenic NSG (NSG-A24:02) mouse model to allow the preparation of a first-in-men clinical safety package for adoptive transfer of TEG011. Mice treated with TEG011 did not exhibit any graft-versus-host disease-like symptoms and extensive analysis of pathologic changes in NSG-A24:02 mice did not show any off-target toxicity of TEG011. However, loss of persistence of TEG011 in tumor-bearing mice was associated with the outgrowth of extramedullary tumor masses as also observed for mock-treated mice. In conclusion, TEG011 is well tolerated without harming HLA-A*24:02+ expressing healthy tissues, and TEG011 persistence seems to be crucial for long-term tumor control in vivo.

Human NK cell development in hIL-7 and hIL-15 knockin NOD/SCID/IL2rgKO mice.

The immune system encompasses acquired and innate immunity that matures through interaction with microenvironmental components. Cytokines serve as environmental factors that foster functional maturation of immune cells. Although NOD/SCID/IL2rgKO (NSG) humanized mice support investigation of human immunity in vivo, a species barrier between human immune cells and the mouse microenvironment limits human acquired as well as innate immune function. To study the roles of human cytokines in human acquired and innate immune cell development, we created NSG mice expressing hIL-7 and hIL-15. Although hIL-7 alone was not sufficient for supporting human NK cell development in vivo, increased frequencies of human NK cells were confirmed in multiple organs of hIL-7 and hIL-15 double knockin (hIL-7xhIL-15 KI) NSG mice engrafted with human hematopoietic stem cells. hIL-7xhIL-15 KI NSG humanized mice provide a valuable in vivo model to investigate development and function of human NK cells.

Co-activation of macrophages and T cells contribute to chronic GVHD in human IL-6 transgenic humanised mouse model.

BACKGROUND: Graft-versus host disease (GVHD) is a complication of stem cell transplantation associated with significant morbidity and mortality. Non-specific immune-suppression, the mainstay of treatment, may result in immune-surveillance dysfunction and disease recurrence. METHODS: We created humanised mice model for chronic GVHD (cGVHD) by injecting cord blood (CB)-derived human CD34+CD38-CD45RA- haematopoietic stem/progenitor cells (HSPCs) into hIL-6 transgenic NOD/SCID/Il2rgKO (NSG) newborns, and compared GVHD progression with NSG newborns receiving CB CD34- cells mimicking acute GVHD. We characterised human immune cell subsets, target organ infiltration, T-cell repertoire (TCR) and transcriptome in the humanised mice. FINDINGS: In cGVHD humanised mice, we found activation of T cells in the spleen, lung, liver, and skin, activation of macrophages in lung and liver, and loss of appendages in skin, obstruction of bronchioles in lung and portal fibrosis in liver recapitulating cGVHD. Acute GVHD humanised mice showed activation of T cells with skewed TCR repertoire without significant macrophage activation. INTERPRETATION: Using humanised mouse models, we demonstrated distinct immune mechanisms contributing acute and chronic GVHD. In cGVHD model, co-activation of human HSPC-derived macrophages and T cells educated in the recipient thymus contributed to delayed onset, multi-organ disease. In acute GVHD model, mature human T cells contained in the graft resulted in rapid disease progression. These humanised mouse models may facilitate future development of new molecular medicine targeting GVHD.

Atypical SIFD with novel TRNT1 mutations: a case study on the pathogenesis of B-cell deficiency.

Mutation in the gene encoding tRNA nucleotidyl transferase, CCA-adding 1 (TRNT1), an enzyme essential for the synthesis of the 3'-terminal CCA sequence in tRNA molecules, results in a disorder that features sideroblastic anemia, B-cell immunodeficiency, periodic fever, and developmental delay. Mutations in TRNT1 are also linked to phenotypes including retinitis pigmentosa, cataracts, and cardiomyopathy. To date, it has remained unclear how defective TRNT1 is linked to B-cell deficiency. Here we report the case of a 12-year-old boy without sideroblastic anemia who harbors novel compound heterozygous mutations in TRNT1. Immunophenotypic analysis revealed severely decreased levels of B cells and follicular helper T cells. In the bone marrow, B-cell maturation stopped at the CD19+CD10+CD20+/- pre-B-cell stage. Severe combined immunodeficiency mice transplanted with bone marrow hematopoietic stem cells from the patient showed largely normal B-cell engraftment and differentiation in the bone marrow and periphery at 24 weeks post-transplantation, comparable to those in mouse transplanted with healthy hematopoietic stem cells. Biochemical analysis revealed augmented endoplasmic reticulum (ER) stress response in activated T cells. Peripheral B-cell deficiency of TRNT1 deficiency may be associated with augmented ER stress in immature B cells in the bone marrow.

Development of a simple new flow cytometric antibody-dependent cellular cytotoxicity (ADCC) assay with excellent sensitivity.

Antibody-based therapeutic strategies have become recognized as useful clinical options in several types of cancer, often with the expectation that such therapies will trigger target cell elimination via antibody-dependent cellar cytotoxicity (ADCC) by natural killer cells. The successful development of therapeutic monoclonal antibodies (mAbs) requires an assay system that permits a critical evaluation of their physicochemical and biological characteristics. At present a number of ADCC assay systems have been reported, however, there is still room for improvement in terms of usability, operability and sensitivity. Here we report a novel flow cytometric ADCC assay that uses a human natural killer cell line stably transfected with mouse FcγRIII, and Fc receptor common-γ chain (FcRγ) and a reporter gene as effector cells. This assay relies on discriminating effector and target cells by their differential immunofluorescence, which allows for clear-cut gating and accurate calculation of the number of surviving cells in a target population. This assay is easy and quick to perform and provides reliable data even for low frequency target cells in assay samples and with low concentrations of mAbs. Furthermore, our approach allows us to identify synergistic ADCC activity of mAbs with different epitope specificities on the same target antigen.

Deregulated Mucosal Immune Surveillance through Gut-Associated Regulatory T Cells and PD-1+ T Cells in Human Colorectal Cancer.

Disturbed balance between immune surveillance and tolerance may lead to poor clinical outcomes in some malignancies. In paired analyses of adenocarcinoma and normal mucosa from 142 patients, we found a significant increase of the CD4/CD8 ratio and accumulation of regulatory T cells (Tregs) within the adenocarcinoma. The increased frequency of Tregs correlated with the local infiltration and extension of the tumor. There was concurrent maturation arrest, upregulation of programmed death-1 expression, and functional impairment in CD8+ T cells (CTLs) isolated from the adenocarcinoma. Adenocarcinoma-associated Tregs directly inhibit the function of normal human CTLs in vitro. With histopathological analysis, Foxp3+ Tregs were preferentially located in stroma. Concurrent transcriptome analysis of epithelial cells, stromal cells, and T cell subsets obtained from carcinomatous and normal intestinal samples from patients revealed a distinct gene expression signature in colorectal adenocarcinoma-associated Tregs, with overexpression of CCR1, CCR8, and TNFRSF9, whereas their ligands CCL4 and TNFSF9 were found upregulated in cancerous epithelium. Overexpression of WNT2 and CADM1, associated with carcinogenesis and metastasis, in cancer-associated stromal cells suggests that both cancer cells and stromal cells play important roles in the development and progression of colorectal cancer through the formation of a tumor microenvironment. The identification of CTL anergy by Tregs and the unique gene expression signature of human Tregs and stromal cells in colorectal cancer patients may facilitate the development of new therapeutics against malignancies.

Overcoming mutational complexity in acute myeloid leukemia by inhibition of critical pathways.

Numerous variant alleles are associated with human acute myeloid leukemia (AML). However, the same variants are also found in individuals with no hematological disease, making their functional relevance obscure. Through NOD.Cg-PrkdcscidIl2rgtmlWjl/Sz (NSG) xenotransplantation, we functionally identified preleukemic and leukemic stem cell populations present in FMS-like tyrosine kinase 3 internal tandem duplication-positive (FLT3-ITD)+ AML patient samples. By single-cell DNA sequencing, we identified clonal structures and linked mutations with in vivo fates, distinguishing mutations permissive of nonmalignant multilineage hematopoiesis from leukemogenic mutations. Although multiple somatic mutations coexisted at the single-cell level, inhibition of the mutation strongly associated with preleukemic to leukemic stem cell transition eliminated AML in vivo. Moreover, concurrent inhibition of BCL-2 (B cell lymphoma 2) uncovered a critical dependence of resistant AML cells on antiapoptotic pathways. Co-inhibition of pathways critical for oncogenesis and survival may be an effective strategy that overcomes genetic diversity in human malignancies. This approach incorporating single-cell genomics with the NSG patient-derived xenograft model may serve as a broadly applicable resource for precision target identification and drug discovery.

The Impact of a Humanized CCR4 Antibody (Mogamulizumab) on Patients with Aggressive-Type Adult T-Cell Leukemia-Lymphoma Treated with Allogeneic Hematopoietic Stem Cell Transplantation.

Although a humanized CCR4 antibody (mogamulizumab) was reported to be effective for refractory adult T-cell leukemia-lymphoma (ATL), several reports regarding the use of mogamulizumab before allo-hematopoietic stem cell transplantation (HSCT) strongly indicated a high incidence of severe acute graft-versus-host-disease (GVHD) and treatment-related mortality (TRM). We retrospectively analyzed nine aggressive-type ATL patients who underwent allo-HSCT at a single institution in Miyazaki from 2006.1.1 to 2015.7.31. Among nine ATL patients, three had used mogamulizumab before treatment with allo-HSCT because of the poor control of refractory ATL. All three patients were treated with four to eight cycles of mogamulizumab. The interval from last administration of mogamulizumab to allo-HSCT was two to five months. All three patients with prior mogamulizumab treatment developed mild-moderate acute GVHD (grade 2) 28, 34, or 40 days after allo-HSCT. Acute GVHD was controlled by prednisolone treatment. Two patients in complete remission before allo-HSCT exhibited relatively prolonged survival (survival rate, 66%). Moreover, one patient developed human T-cell leukemia virus type 1-associated myelopathy-mimicking myelitis at five months after allo-HSCT. In contrast, two of six ATL patients without a history of mogamulizumab use survived (survival rate 33%). Thus, in cases of mogamulizumab use before treatment with allo-HSCT for refractory ATL, an appropriately long interval from the last administration of mogamulizumab to allo-HSCT may be one of factors to reduce TRM by acute GVHD, and to subsequently enhance graft-versus-tumor effects in ATL cases. Furthermore, caution is needed when administering mogamulizumab before allo-HSCT for severe GVHD and TRM.

[A Case of Perforative Peritonitis Due to Intestinal Metastasis from Lung Cancer].

We here describe a case of an acute peritonitis due to perforation of a small intestine tumor metastasized from a lung cancer. A 66-year-old man who had undergone a bladder cancer procedure 2 years ago and was hospitalized for the second operation, complained sudden abdominal pain. An enhanced abdominal CTrevealed a small amount of free gas and ascites in the abdominal cavity. On the same day, emergency exploratory surgery was performed with the diagnosis of perforative peritonitis. A laparotomy revealed a jejunal tumor with perforation 40 cm distal from the Treitz ligament. After surgery, the patient confessed that he had got a notice of the recurrence of lung cancer which had been treated 9 years ago. The pathological result indicated the lesion was metastasis from lung cancer. Although small intestinal metastatic tumor from lung cancer is rare, it should be considered when acute abdomen is observed.

Clinical Features and Treatment Outcomes of 51 Patients with Chronic Myeloid Leukemia Treated with a Tyrosine Kinase Inhibitor at a Single Institution from 2002 to 2014.

Although clinical trials of first- and second-generation tyrosine kinase inhibitors (TKIs) have been shown to improve the prognosis of chronic myeloid leukemia (CML), there is still uncertainty about the clinical features, treatment outcomes, adverse effects, and other possible problems of their use in the clinical setting. We retrospectively analyzed 51 CML patients treated with TKIs at a single institution between 2002 and 2014. The patients (median age: 53.8 years) were classified as having chronic (n = 48), accelerated (n = 2), or blastic phase (n = 1) CML. Our treatments included both 1st generation TKIs (60.8%) and 2nd generation TKIs (39.2%). We found that the overall response rates of complete cytogenetic response (CCyR), major molecular response (MMR), and MR4 (molecular response 4) were 90.2%, 78.4%, and 64.7%, respectively. Second line 2nd generation TKIs had response rates equivalent to those of 1st line 1st generation TKIs. Moreover, 1st line 2nd generation TKIs tended to achieve an early response rate. Overall survival (OS) at 5 years was 93.2%. Sudden blastic crisis (BC) occurred in 2 CML patients receiving TKI with CCyR status. Hematopoietic stem cell transplantation was performed for BC (n = 1) and sudden BC (n = 2). Side effects of all grades (1-3) and grade 3 alone were 64.7% and 11.8%, respectively. Dose reduction, replacement with another TKI, or low dose TKI treatment may be useful methods to control side effects. Further reasons of TKI discontinuation were economic problems (n = 3) and pregnancy (n = 1). Consequently, our treatment strategy for CML demonstrated good response rate and OS. Currently, treatment discontinuation due to intolerance, resistance, economic problems, pregnancy, and sudden BC remains a concern in clinical practice.

Clinical Impact of a Humanized CCR4 Antibody (Mogamulizumab) in 14 Patients with Aggressive Adult T-cell Leukemia-lymphoma Treated at a Single Institution During a Three-year Period (2012-2014).

Objective We elucidated the effectiveness of a humanized CCR4 antibody (mogamulizumab) on adult T-cell leukemia-lymphoma (ATL), which typically has a poor outcome. Methods We retrospectively analyzed 14 patients with aggressive ATL who had been treated at our institution with weekly cycles of mogamulizumab for eight weeks from 2012-2014. Results The patients (median age: 63 years old) were classified as having acute- (n=10) or lymphoma-type (n=4) ATL. The prior treatment regimens consisted of CHOP, VCAP-AMP-VECP, DeVIC and CHASE, with an average of two courses (range: 1-4). The prior disease responses were partial remission (n=3) and progressive disease (n=11). The treatment was administered in the primary refractory setting (n=8), for relapse (n=2), or as bridging therapy before hematopoietic stem cell transplantation (n=4). The overall response rates were 64% and 43% after four and eight cycles (or after the final cycles), respectively. The median overall survival (OS), OS rate at six months and OS rate at 12 months were 66 days, 41.7% and 20.8%, respectively. All of the patients with acute-type ATL who showed a response to treatment had an early response. Notably, six of the 14 ATL patients showed somewhat prolonged survival (>100 days). However, relapse or disease progression in the peripheral blood, central nervous system, lymph nodes, skin, and/or bone occurred within a relatively short period after treatment. The adverse effects were tolerable, and included lymphopenia, cytomegalovirus infection and skin rash. Conclusion Mogamulizumab therapy resulted in an early and high remission rate and somewhat prolonged survival in patients with refractory ATL. However, the duration of remission was short, and there was early relapse and disease progression. This study may show the current impact of mogamulizumab in clinical practice.