Two years have passed since the Clinical Trials Act came into effect in April 2018. There were a series of research misconducts behind the legislation, and the Clinical Trials Act was enacted to ensure confidence in clinical trials conducted in Japan. The term “specified clinical trials” refers to clinical trials conducted using pharmaceuticals or medical devices, approval for which has not been obtained, or clinical trials conducted receiving research funds or other benefits provided by a manufacturer with marketing approval for pharmaceuticals or medical devices. The key elements in conducting specified clinical trials are as follows: (1) compliance with clinical trial standards, (2) approval by the certified review board, (3) submission of the trial plan to the Minister of Health, Labour, and Welfare, and (4) entering into an agreement with a manufacturer providing research funds. This manuscript overviews the Clinical Trials Act and the conduct of specified clinical trials by reviewing the key issues behind the legislation.

In 2013, there were cases in which clinical research papers on antihypertensive drugs conducted at five universities in Japan were retracted. Based on this case, the clinical research system in Japan was reviewed, and it was particularly required to strengthen the conflict of interest (COI) management system. Clinical Trial Act effected in April 2017 imposed a conflict of interest management obligation on researchers conducting clinical research. Conflict of interest management is accountability for the society and patients and protection of the cutting-edge research. This reviews the necessity and purpose of conflict of interest management and introduces the types of research and the required management of conflict of interest.

In 2000, imatinib became the first tyrosine kinase inhibitor (TKI) approved for the treatment of chronic myeloid leukemia (CML); this was soon followed by second generation (nilotinib, dasatinib, and bosutinib) and third generation (ponatinib) TKIs, all of which are currently available for the treatment of CML. Their emergence has revolutionized treatment strategies for CML, leading to a new era that has seen the 10-year overall survival rate for CML patients exceed 80%; despite the impact of TKIs on CML prognosis, only 10 to 20% of CML patients maintain treatment-free remission after TKI cessation. Moreover, prolonged treatment produces various adverse effects, such as serious vascular adverse events including stroke, myocardial infarction, and peripheral arterial occlusive disease. The pathophysiological mechanisms underlying those effects remain unclear, and protocols for managing such life-threatening events have not been established. Thus, I conducted a narrative review of the literature to clarify the current state of knowledge. Based on that review and my experiences during daily clinics, I herein present a discussion on the incidence, diagnosis, and management of TKI-induced vascular adverse events.

Langerhans cell histiocytosis (LCH) is a rare disease characterized by tissue infiltration of clusters of CD1a⁺/CD207⁺ histiocyte-like cells and a resultant surrounding inflammatory reaction. Because of its morphological similarity to cutaneous Langerhans cells, LCH was formerly named histiocytosis X in 1987. However, its cell lineage appears closely related to myeloid dendritic cells. In 2010, BRAF-V600E was detected in biopsy specimens from the majority of LCH patients. The subsequent observation of extracellular signal-regulated kinase phosphorylation in almost all LCH samples suggested that LCH was a neoplasm provoked by activation of the mitogen-activated protein (MAP) kinase pathway. Therefore, the 2016 Revised Classification by the Histiocyte Society defined LCH as an inflammatory myeloid neoplasm. Although a series of global and domestic clinical trials have improved the prognosis of pediatric LCH patients, no standard therapy with a high level of evidence for adult cases exists. Generally, LCH patients have a favorable prognosis, but delayed diagnosis and intervention may cause severe damage to the involved organs, resulting in a poor quality of life. Here we present recent advances in the pathophysiology and treatment of LCH to enlighten the understanding of this orphan disease.

A literature review of the data of hematological cancer survivors revealed that both the cumulative proportion and burden of late effects change according to the attained age, primary cancer, and type of treatment. I selected neurocognitive dysfunction, cardiovascular disease, endocrinological dysfunction, musculoskeletal dysfunction, subsequent immunodeficiency, and reproductive dysfunction as representative late effects. I accordingly explained the characteristics of secondary cancers as the most life-threatening late effects and compared the late effects between survivors who did and did not undergo hematopoietic stem cell transplantation, respectively. The main goals of my educational lecture are as follows: (1) to highlight important late effects in hematological cancer survivors and their risk factors; (2) to discuss primary secondary cancers and explain their characteristics (e.g., frequency, incubation periods, and risk factors); (3) to characterize late effects after hematopoietic stem cell transplantation; and (4) to use representative long-term follow-up guidelines if necessary.

Lymphocytes play pivotal roles in innate and adaptive immunity. The differentiation process by which hematopoietic stem cells (HSCs) acquire specific functions has been extensively investigated and is considered the paradigm of cell differentiation. It has been widely accepted that highly enriched HSCs are heterogeneous with respect to their lymphopoietic potential, and aged or stressed HSCs are skewed to the myeloid lineage. Several transcription factors and cytokine signaling pathways have been reported as essential to lymphocyte differentiation. However, the molecular mechanism that modulates the earliest stage remains unclear. Furthermore, the origin and characteristics of early T-lymphoid progenitors that migrate from the bone marrow to the thymus are still unknown in this field. Epigenetic mechanisms likely influence early lineage specification through the regulation of mitochondrial function and modification of nuclear chromatin structure. This review summarizes previous and recent findings on the processes involved in early lymphocyte differentiation. Thus, it provides a foundation for the understanding of the physiology of HSC aging and the pathology of intractable acute lymphocytic leukemia.

Mammals have developed bone marrow (BM) inside the bone tissue because of evolution. Now, it appears that bone tissue displays functional communication with the hematopoietic system. Osteoblast lineage cells serve as a part of the microenvironment for immature hematopoietic cells, whereas mature hematopoietic cells play important roles in regulating osteoblast activity. The nervous system maintains the balance between the hematopoietic and skeletal systems. An understanding of the multiple-organ network that exists between the BM and other systems is useful to elucidate phenomena in clinical hematology and even in other fields, an area which I propose to call “marrowlogy.”

Expansion of stem cell numbers without reduction in their regenerative potential is crucial for therapeutic applications. However, the repeated cell divisions and aging impair stem cell function. We found that Pot1a, a component of the shelterin that protects telomeres, involves the maintenance of hematopoietic stem cell (HSC) activity during aging. Pot1a maintained the self-renewal activity of HSCs through the prevention of DNA damage responses in HSCs and suppression of the production of reactive oxygen species. Furthermore, the exogenous Pot1a expanded the HSC number and rejuvenated aged HSCs function upon ex vivo culture. Consistent with these results, treatment with exogenous human POT1 protein maintains human HSC activity in culture. Collectively, these results show that Pot1a or POT1 sustains HSC activity and can be used to expand HSC numbers ex vivo.

Aplastic anemia is a syndrome characterized by the decrease in hematopoietic stem cells along with bone marrow hypoplasia and pancytopenia, which is likely to be a T cell-mediated autoimmune disease. Since the response rate to immunosuppressive therapy is higher if started ahead of time, early initiation of treatment is recommended even in non-severe cases. Among treatment approaches in severe cases, immunosuppressive therapy with anti-thymocyte globulin (ATG) plus cyclosporin is the basic approach. However, the effectiveness of thrombopoietin receptor agonists has also been reported, with recovery of hematopoiesis in three blood lineages observed in some patients. Despite no evidence of increased incidence of genetic mutations with thrombopoietin receptor agonist treatment, bone marrow testing is recommended after three to six months of long-term treatment to detect the presence of chromosomal abnormalities. With regard to hematopoietic stem cell transplantation for aplastic anemia, cyclophosphamide is reduced as a pretreatment therapy, and instead, fludarabine is used in combination in order to reduce cardiotoxicity. Since HLA haploidentical hematopoietic stem cell transplantation has been developed and is being reportedly used in patients with no suitable donors, this transplantation approach might also be extended to aplastic anemia patients who were not considered eligible for transplantation in the past.

Paroxysmal nocturnal hemoglobinuria (PNH) causes clonal expansion of hematopoietic stem cells with abnormal GPI-anchor biosynthesis. The major pathological condition of PNH is that the erythrocytes lacking the complement regulatory factors CD55 and CD59, which are GPI-anchored proteins, lead to intravascular hemolysis through complement activation. Clonal expansion has been assumed to be involved in an immunological attack on hematopoietic stem cells, and the bone marrow failure associated therewith modifies the pathology to varying degrees. The introduction of eculizumab made complement control possible; however, the problems associated with it became apparent as the treatment progressed. Additionally, the PNH Reference Guide was significantly revised in 2016, partly because PNH was designated as a Japanese medical subsidy. With the revised edition of 2020, minor revisions have been added to reflect further advances in treatment and understanding of the disease, while mainly dealing with the clinical introduction of eculizumab derivative, ravulizumab, which uses recycling antibody technology. This review outlines the points of the 2020 revision, including the important points of the previous revision.

Autoimmune hemolytic anemia (AIHA) is a rare disease with an unknown etiology. Although the diagnosis of a typical case is expected to be easy, the actual diagnosis is often challenging due to the diversity of conditions. Prednisolone treatment continues for a long period and causes several adverse events, including infection and osteoporosis. Therefore, a solid understanding of the pathophysiology, depending on the disease type, is necessary to avoid ineffective and unnecessary treatment and achieve a good outcome. Previously, we reported two studies concerning colorectal cancer that ectopically expresses band 3 erythrocyte membrane protein, leading to cancer-related anemia without bleeding through an immune response identical to or resembling AIHA. In this article, the methods of laboratory examination for the diagnosis of AIHA are summarized to serve as physicians’ reference. Furthermore, points for conventional management and emerging treatments against specific targets are briefly described. In addition, due to the increasing knowledge on B-1 cells’ participation in malignant and autoimmune diseases, the pathophysiological role of B-1 cells in AIHA is scrutinized through their physiological function in innate and adaptive immunity, in terms of the production of anti-band 3 antibodies. The screening and analysis of primary disease in AIHA should improve clinical outcomes.

Acquired pure red cell aplasia (PRCA) is characterized by normocytic anemia, reticulocytopenia, and a marked decrease in erythroid cell count in the bone marrow. PRCA develops in the context of various backgrounds, including recently recognized immune checkpoint inhibitor-associated PRCA, that need careful differential diagnoses. Besides humoral abnormalities such as major ABO-incompatible allogeneic hematopoietic stem cell transplantation-related PRCA, dysregulations of T cells have been shown. STAT3 gene mutations of cytotoxic T cells were identified in 40% of PRCA patients, which might suggest their use as novel molecular markers for PRCA. As initial management options for PRCA, red blood cell transfusion and immunosuppressive therapy (IST) drugs, such as cyclosporin, are usually selected. Roughly 80% of patients respond to IST; however, some relapse afterward or are refractory to IST. When patients with PRCA become refractory to two or three lines of IST, allogeneic hematopoietic stem cell transplantation (HCT) would become an appropriate choice, although the optimal procedures for allogeneic HCT have not been determined. A prospective study of PRCA in Japan has been ongoing since 2016 to solve the myriad clinical issues of PRCA.

Inflammation is a physiological process that primarily occurs as a way to help protect the host against tissue damage and invasion by pathogens. During inflammation, erythropoiesis is suppressed and, if it lasts, anemia develops. The mechanisms underlying this are complex and not fully understood, but various cytokines, such as tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), and IL-6, are involved. TNF-α upregulates PU.1, which is a crucial transcription factor in granulocytic differentiation, and downregulates GATA-1, a master transcription factor for erythroid differentiation, in hematopoietic stem cells. TNF-α and IL-1β suppress erythropoietin production in the kidney, whereas IFN-γ downregulates the expression of erythropoietin receptors in erythroid precursor cells. Moreover, IL-6 upregulates the production of hepcidin, the master regulator of systemic iron metabolism, in the liver. Hepcidin reduces the iron available for erythropoiesis by downregulating the rate of iron release from macrophages. Activated macrophages may also contribute to the development of anemia by shortening the erythrocyte lifespan. Proper management of the underlining conditions is necessary in treating anemia associated with inflammation. Erythropoiesis-stimulating agents may be administered to patients with chronic kidney disease, whereas anti-IL-6 agents may be beneficial for anemic patients with rheumatoid arthritis and idiopathic multicentric Castleman disease.

GATA1-deficient mice die in utero on 12.5 embryonic day (E12.5) due to a complete block of primitive erythropoiesis in the yolk sac, while GATA2-deficient mice die on E10.5 due to severe anemia and hemorrhage, since GATA2 is essential for the development of hemangioblasts, which are common precursor cells of hematopoietic stem cells and endothelial cells. In contrast, GATA3 is critical to the development of Th2 cells. However, GATA3-deficient mice die in utero before the particular phenotype of hematopoietic system emerges, which is caused by a defect in the development of nervous and renal urinary systems. It has been well elucidated that defects in the hematopoietic GATA factors disturb hematopoietic homeostasis. However, details on how GATA factor dysfunction leads to human hematopoietic diseases remain to be clarified. At the end of the twentieth century, several mutations in GATA1 gene were identified as the cause of familial thrombocytopenia. Since then, various types of hematopoietic diseases elicited by GATA1 and GATA2 dysfunctions have been reported. This review summarizes recent topics of GATA factor-related hematopoietic diseases.

Through intensive efforts of genome sequencing of myeloid malignancies, a comprehensive registry of driver mutations has been revealed, virtually providing us with a complete spectrum of driver mutations in these diseases. Importantly, there have been significant correlations between driver mutations, which suggests that some combinations of genetic events confer strong selective advantage on mutated stem cells. Next-generation sequencing technology have also revealed that clonal hematopoiesis is a common, age-related process in which a somatically mutated hematopoietic precursor gives rise to a genetically distinct subpopulation in the blood. Furthermore, novel germline mutations were identified, indicating that mutated stem cells appear long before myelodysplastic syndrome (MDS) presentation. Such founding mutations are thought to be acquired and positively selected in a well-organized manner to allow for expansion of the initiating clone to compromise normal hematopoiesis, ultimately giving rise to MDS and subsequent transformation to acute myeloid leukemia (AML) in many patients.

Evidence of human leukemia stem cells (LSCs) in acute myeloid leukemia (AML) was first reported nearly a quarter century ago through the identification of rare engrafting cell subpopulations in patient-derived xenograft assays. Since then, studies have revealed diverse characteristics of AML stem cells. Initiating mutations convert normal hematopoietic stem cells (HSCs) to pre-leukemic HSCs. The repopulation advantage of pre-leukemic HSCs over normal HSCs leads to clonal evolution. Acquisition of additional mutations in pre-leukemic HSCs results in the development of AML composed of genetically distinct subclones. Each subclone contains LSCs with unique characteristics, and these LSCs contribute to therapeutic resistance and relapse. Interestingly, some LSCs can escape from antitumor immune responses, thereby survive the treatment. This article summarizes recent advances in the field of LSC biology from genomic and immunological perspectives.

Genomics and novel molecularly targeted drugs for treating acute myelogenous leukemia (AML) are developing rapidly. To optimize the allocation of patients to the best possible treatment, we have to expedite test results of cytogenetic and molecular analyses for target mutations such as CBF and FLT3, since gene mutations are specifically associated with patient prognosis and therefore inform medical decision making. However, novel agents cannot completely eradicate AML because of the emergence of resistance to these agents; therefore, at the moment it is still necessary to combine cytotoxic treatment with novel agents. Hence, it becomes vital to understand how to stratify AML patients and subsequently treat the right patients with the right combination of cytotoxic treatments and novel agents.

Some studies have reported the clinical significance of minimal/measurable residual disease (MRD) in considering the prognostic stratification and therapeutic intervention after complete remission in acute myeloid leukemia (AML). In the clinical setting, multicolor flow cytometry (MFC), a quantitative PCR method targeting the expression of fusion genes generated by chromosomal translocation, such as PML-RARA, RUNX1-RUNXT1, and CBFB-MYH11, as well as WT1 mRNA, was used to detect MRD in AML. In recent years, quantitative PCR, next-generation sequence, and digital-droplet PCR methods targeting genetic alterations often detected in AML have been developed to assess its clinical significance. However, besides analysis methods, many common problems persist in MRD evaluation, such as sample collection points, type of samples, and threshold setting. Although several gene mutations involved in clonal hematopoiesis have been detected in CR patients, their presence did not correlate with the prognosis, and some leukemia-specific mutations did not always persist during the clonal evolution of AML. Therefore, it is essential to combine multiple methods, such as target gene mutation, quantitative PCR, and MFC to enhance the sensitivity of measurement. Furthermore, the establishment of novel treatment strategies incorporating MRD and molecular abnormalities is warranted for better clinical outcomes of AML.

In acute myeloid leukemia (AML), a number of chromosomal abnormalities and gene mutations associated with onset and recurrence were discovered by the recent progress of genome analysis technology. The founding did not only have clinical application as prognostic factors and minimal residual disease markers but also contributed to novel molecular targeted drug development. Many new drugs, such as first-generation FLT3 inhibitor, IDH1/2 inhibitor, and BCL2 inhibitor, have been developed in Europe and the United States. In addition, the second-generation FLT3 inhibitors, gilteritinib and quizartinib, were developed in Japan, which significantly improved the treatment outcome of AML. However, there is still a large disparity in drug availability between Europe and the United States and Japan. As a result, treatment guidelines in Europe and the United States cannot be applied to practical use in Japan. This paper presents an outline of the prognosis stratification and indication of allogenic hematopoietic cell transplantation for AML by gene diagnosis in Japan.

All-trans retinoic acid (ATRA) in combination with chemotherapies had been the standard therapy for newly diagnosed acute promyelocytic leukemia (APL). In Japan, APL204 study using ATRA+chemotherapy showed favorable outcomes, in which 7-year event-free and overall survival rates were 79% and 87%, respectively. Recently, a combination of ATRA and arsenic trioxide (ATO) has emerged as a promising therapy for newly diagnosed APL. Specifically, for patients with standard-risk APL with an initial white blood cell count (WBC) of <10,000/µl, two randomized controlled trials showed superior outcomes using ATRA+ATO to ATRA+chemotherapy, with long-term survival rates above 90%. Now ATRA+ATO is considered as an established standard therapy for newly diagnosed patients with standard-risk APL. Some prospective studies have also showed the efficacies of ATRA+ATO in patients with high-risk APL with an initial WBC of >10,000/µl although the administration of gemtuzumab ozogamicin or idarubicin was required in addition to ATRA+ATO during induction therapy. This review briefly summarizes the findings of ATRA+chemotherapy, focusing on the APL204 study, and introduces trials of ATRA+ATO for newly diagnosed APL. Furthermore, it describes the management of complications, including disseminated coagulation and differentiation syndrome.

Subsequent malignant neoplasms (SMNs) are one of the most serious late complications in pediatric patients with cancer, with more than 10% of long-term cancer survivors developing SMNs. Germline mutations in cancer predisposition genes have been recently highlighted as a risk factor. For example, germline mutations in the TP53 gene were reported to be a risk factor for SMNs. A comprehensive genomic analysis for a large cohort of long-term survivors of childhood cancer showed that variants in cancer predisposition genes were correlated with the higher cumulative incidence of SMNs. As another genetic risk, previous reports suggested that polymorphisms in genes regulating thiopurine pathway such as TPMT gene might contribute to SMN development after acute lymphoblastic leukemia treatment. Considering improved survival probability, attention should be paid for late complications. Thus, therapeutic strategy should be optimized based on a risk for SMNs of each individual.

Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell neoplasm characterized by the Philadelphia chromosome, t (9;22)(q34;q11.2), which causes the generation of the BCR-ABL1 oncoprotein with constitutively active tyrosine kinase. Treatment with tyrosine kinase inhibitors (TKIs) has significantly improved the prognosis of CML. Optimal treatment decisions at specific time points in patients with suboptimal response minimizes the risk of disease progression and CML-related death. The expected survival for patients with CML treated with TKI is now similar to that of the general population. Given the stable clinical course over the years, treatment-free remission (i.e., functional cure) can be considered in patients with sustained deep molecular response. Second-generation TKIs achieved higher rates of deep molecular response than imatinib, which could translate to increased candidates for functional cure without TKI therapy. The third-generation TKI, ponatinib, brought a new hope to patients who failed multiple TKIs because of resistance and/or intolerance. EUTOS long-term survival (ELTS) score can guide optimal treatment selection.

Since the discovery of the gain-of-function mutation JAK2 V617F, significant progress has been made in clarifying the pathology and developing novel agents for myeloproliferative neoplasms, including polycythemia vera (PV). The treatment strategy for PV is to first classify patients into either high- or low-risk groups for thrombosis. All patients with PV should be treated with low-dose aspirin and phlebotomy. In addition, for high-risk PV patients, cytoreductive therapy is recommended. Although hydroxyurea (HU) is the most popular agent for PV treatment, the advantages of ruxolitinib, a JAK inhibitor, for patients who are intolerant or resistant to HU were recently reported. Furthermore, the ability of interferon-α to selectively eliminate the malignant clone and induce complete molecular response was previously demonstrated. In this article, important clinical trials associated with the treatment strategy for PV and recent advances in PV treatments are described.

Primary myelofibrosis (PMF) is classified as a clonal myeloproliferative neoplasm (MPN) characterized by bone marrow fibrosis and subsequent extramedullary hematopoiesis that causes progressive anemia, symptomatic splenomegaly, and various constitutional symptoms and eventual transformation into acute leukemia. The main MPN pathophysiology is the constitutive activation of JAK2/STAT signaling. JAK2, MPL, and CALR mutations, known as phenotypic driver mutations, are directly implicated in the disease pathogenesis by the activation of JAK2/STAT signaling. Moreover, other gene mutations, including methylation-related regulators, histone modification-related factors, and RNA splicing molecules, also contribute to the pathogenesis of MPN development. Patients with PMF, unlike other MPNs, experience a significantly worse prognosis. Thus, the risk of disease should be evaluated individually, and a tailored treatment plan should be developed based on each patient's disease risk. Gene mutation information is becoming more important in evaluating the risk of disease and determining treatment options. Allogeneic hematopoietic stem cell transplantation is the only curative treatment, but its indication is limited because of the age of onset. A JAK2 inhibitor, ruxolitinib, improves splenomegaly and disease-related constitutive symptoms. To date, new JAK2 inhibitors and drugs that delay the progression of fibrosis and leukemic transformation are under development and are expected to improve the prognosis for PMF.

Frequent packed red blood cell (pRBC) transfusion can cause transfusional iron overload. Excess iron generates reactive oxygen species and provokes organ dysfunction. In lower-risk myelodysplastic syndrome (MDS), hyperferritinemia is known as one of the negative prognostic factors. Thus far, iron chelation therapy (ICT) is the only effective treatment for chronic iron overload induced by transfusion. Transfusional iron overload is diagnosed when serum ferritin (SF) levels are ≥500 ng/ml and cumulative volume of pRBC transfusion is ≥20 JPN units. ICT should be initiated when SF levels are ≥1,000 ng/ml and will be further continued until SF levels decline to <500 ng/ml. ICT serves to ameliorate organ dysfunction. A prospective study demonstrated that in patients with lower-risk MDS, ICT can reduce the risk of combined events, including cardiac events, hepatic events, AML transformation, and death of any cause. In some patients, hematological improvement will be observed. However, clinical features underling this hematological phenomenon are not fully understood. Therefore, ICT should not be performed solely for the purpose of hematological recovery.

Myelodysplastic syndromes (MDS) are neoplastic diseases of the hematopoietic stem cells, caused by genetic mutations. The clinical courses of MDS are highly variable based on the underlying genetic aberrations, ranging from slowly progressing cytopenia to rapidly-manifesting fatal diseases, including the development of acute myelogenous leukemia. The management of lower-risk MDS, which is risk-stratified based on the revised International Prognostic Scoring System (IPSS-R), mainly consists of a supportive therapy, including blood transfusion to treat anemia and thrombocytopenia. Recently, three novel drugs were approved, which became available in Japan. These include darbepoetin alfa, an erythropoiesis-stimulating agent; lenalidomide, which is specifically active for anemia of 5q- syndrome; and deferasirox, an oral iron-chelating agent. Decision analyses also provide evidence in determining the optimal timing for the potentially curative allogeneic hematopoietic stem cell transplantation for lower-risk MDS. Thus, the management of lower-risk MDS should be optimized using these novel agents and newly available evidence.

Myelodysplastic syndromes (MDS) are malignant clonal stem cell disorders. There are two main treatment options for higher-risk MDS, i.e., eligible and ineligible hematopoietic stem cell transplantation (HSCT). Transplantation-eligible patients should receive HSCT immediately, with or without prior therapy. In contrast, for patients who are ineligible for HSCT, azacitidine (AZA) may now be the first choice of treatment, which significantly prolongs overall survival in responder patients when compared with conventional care regimens. However, there are major problems regarding the management of patients with disease relapse after HSCT and those with loss of response to AZA. In this review, treatment strategies and future perspectives, including the use of novel agents, are presented with the aim of improving the outcome of higher-risk MDS.

The introduction of imatinib (IM) has led to a paradigm shift in the treatment strategy for Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL). After introducing IM, second- and third-generation tyrosine kinase inhibitors (TKIs), which have stronger BCR-ABL1 inhibitory activity than IM, have appeared and their therapeutic results are beginning to be reported. However, to date, no comparison study between individual TKI and the current treatment strategy for Ph + ALL has been performed considering either a TKI-based regimen in induction followed by combination chemotherapy with a TKI or allogeneic hematopoietic stem cell transplantation (alloSCT). In the case of treating with ponatinib, it was suggested that the inclusion of alloSCT into the treatment strategy could be avoided. Because alloSCT has an appreciable treatment-related mortality rate and an upper age limit, the treatment strategy without alloSCT may remain mainstream in the future. Chemotherapy-free treatments, such as a TKI plus a monoclonal antibody or immunotherapy, are also expected to gain traction an alternate strategy and are now under investigation.

With pediatric-inspired chemotherapy, the survival of adult patients with Philadelphia chromosome-negative acute lymphoblastic leukemia (ALL) has improved. For standard-risk patients in the first complete remission (CR1), pediatric-inspired chemotherapy may be superior than allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, increased dose of steroid, vincristine, and L-asparaginase (L-Asp) in pediatric-inspired chemotherapy induces adverse events in certain number of adult ALL patients. Especially, the administration of L-Asp is often reduced to 60-70% for thrombosis or liver dysfunction. The optimal dose of these agents for adult ALL patients with higher age is under investigation. Moreover, minimal residual disease (MRD) >10⁻⁴ is a poor prognostic factor. The time point for the assessment of MRD should be defined. For relapsed or refractory ALL, inotuzumab ozogamicin and blinatumomab are promising antibody agents that diminish MRD and proceed to allo-HSCT.

Interim positron emission tomography (iPET-2)-guided therapy following two cycles of ABVD chemotherapy has been developed for newly diagnosed classical Hodgkin lymphoma (cHL) patients in several prospective trials. In localized-stage cHL, radiotherapy cannot be omitted, even in iPET-negative patients after two or three cycles of ABVD, whereas two cycles of escalated BEACOPP regimens followed by involved nodular radiotherapy (30 Gy) is a useful treatment option for iPET-2 positive patients after two cycles of ABVD. In advanced-stage cHL, approximately 20% of cases were iPET-2 positive, and the switch to BEACOPP-based regimens was reported as a useful treatment option, with 3-year progression-free survival of approximately 60-65%, in iPET-2-positive patients in three clinical trials. Furthermore, the switch to AVD (omission of bleomycin after two cycles of ABVD) is a reasonable treatment option in iPET-2-negative patients, particularly those at risk for bleomycin lung toxicity in advanced-stage cHL. This review summarizes the current evidence regarding interim PET-guided therapy for newly diagnosed cHL patients.

Follicular lymphoma (FL) is incurable with the current standard therapeutic strategy despite improvements of the natural history of FL in the last few decades. For advanced-stage patients with low-tumor burden, watchful waiting remains the standard treatment. The optimal timing of rituximab monotherapy has not been elucidated. For advanced-stage patients with high-tumor burden, anti-CD20 monoclonal antibody and chemotherapy are the standard care. A subset of FL patients who had early progression of relapse within 24 months has a significantly poor prognosis. Among the early progression of the disease group, more early progression and transformation are important factors. Recently, genomic analysis suggests that high-risk biology may depend on the type of chemotherapy. Therefore, the genomic profile could help develop appropriate treatment selection in the future. This review includes the current FL treatment strategy and prognostic factors.

Peripheral T-cell lymphoma (PTCL) is a kind of aggressive lymphoma with a poorer prognosis than mature B-cell lymphoma. Presently, the standard of care for PTCL is considered to be the CHOP regimen, yet clinical outcomes remain insufficient. The intensification of chemotherapy and front-line high-dose chemotherapy have been examined as potential therapeutic strategies by several clinical trials. A recent double-blind phase III trial examining the effects of brentuximab vedotin (BV) when incorporated into front-line chemotherapy involved CD30-positive PTCL cases and found that a progression-free survival benefit was observed by adding BV to the therapeutic regimen, especially in the context of anaplastic large-cell lymphoma. Other molecular target agents, i.e., antibodies and small molecules, have also actively been developed. Investigators should conduct further clinical trials to establish the next standard treatment by the optimization of classic chemotherapeutic agents and molecular target agents.

The development of targeted therapies, such as rituximab—an anti-CD20 antibody targeting CD20, has undergone a paradigm shift from conventional chemotherapy for malignant lymphoma (ML). Although a subset of ML patients has been cured, the treatment of refractory and relapsed diseases remains challenging. Fortunately, growing insights on molecular biology for ML have led to the development of a number of innovative agents. Moreover, a plethora of targeted therapies, including novel antibodies targeting surface antigens, and small molecular inhibitors targeting oncogenic signaling pathways, tumor suppressors, and epigenetic regulation are currently under investigation for the improvement of dismal prognosis. In addition, immunotherapies, including immune checkpoint inhibitors, bispecific T-cell engager antibodies, and chimeric antigen receptor T-cells for ML have been rapidly developed to target tumor microenvironment. These promising mechanism-based targeted therapies could lead to a successful ML management.

Molecular targeted therapies with small molecule inhibitors and antibodies have rapidly replaced chemoimmunotherapy, which has been the gold standard of care for patients with chronic lymphocytic leukemia (CLL). We discuss the current treatment strategies for CLL with special emphasis on genomic and molecular risk factors including IGHV unmutated status, 11q deletion, and 17p deletion. Ibrutinib and venetoclax are two molecular targeted agents currently available in Japan. They are highly effective, well tolerated, and have improved overall survival. Therefore, molecular targeted therapies are preferred to chemoimmunotherapy for most patients. Ongoing studies will clarify the optimal option between combination and sequence of treatment regimens with an appropriate timing of therapeutic intervention for longer survival. We are nearing an era of chemotherapy-free CLL management.

Immune checkpoint blockade has been widely applied for the treatment of malignant tumors, including hematological malignancies. Nevertheless, growing evidence has indicated that there are specific situations in which somatic or germline abnormalities in gene coding for immune checkpoint-associated molecules may play a role in the development and progression of lymphoid malignancies. Somatic mutations in the PDCD1 gene and generation of the CTLA4-CD28 fusion gene have been reported in T-cell lymphomas and are considered to be involved in disease progression. By contrast, rare germline variants in CTLA4 and HAVCR2 are suggested to be associated with the predisposition to immunodeficiency-associated lymphomas and subcutaneous panniculitis-like T-cell lymphoma, respectively. Abnormalities in the associated molecules may alter the properties of lymphocytes and contribute to cellular transformation because immune checkpoints modulate the activities and functions of lymphocytes. Many new therapies targeting immune checkpoints are under development and have been applied in clinics, and notably, immune checkpoint blockade may lead to an unexpected deterioration in health or the development of new lymphoid malignancies in some specific situations.

Epstein-Barr virus (EBV), the first human tumor virus, was discovered more than 55 years ago. Although EBV is carried by the majority of human population, it contributes to only a small subset of all human cancers. In individuals, this virus manifests lymphotropism, establishes latent infection, and eventually hides in resting memory B cells. However, persons who fail to maintain the virus in its latent state may develop EBV-driven lymphoproliferative disorders (LPDs) and lymphomas. B-cell LPDs and lymphomas occur predominantly in immunocompromised patients, whereas T/NK-cell LPDs and lymphomas mainly arise in immunocompetent individuals. Improved understanding of the biology of these LPDs and the role of EBV expands the potential of new therapy targeting EBV-specific molecules.

Novel drugs, such as proteasome inhibitors, immunomodulators, and antibody drugs, have been consistently developed, and several standard treatment regimens were approved for elderly patients with multiple myeloma who are ineligible for autologous transplantation. Meanwhile, the clinical characteristics of elderly patients are more diverse than those of younger patients in terms of various factors, such as cognitive, mental, or social functions as well as physical or organ functions. Therefore, it is difficult to implement a standard treatment regimen to all elderly patients with a one-size-fits-all approach. Furthermore, it is important to evaluate the diversity of elderly patients as objectively as possible by evaluating organ functions and frailty in accordance with geriatric assessment, which helps determine the treatment plan. In addition, it is also ideal to select the treatment after considering the factors associated with tumors, such as the presence or absence of unfavorable chromosomal abnormalities.

Recent advances in novel therapeutic agents, such as proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies, have markedly improved treatment outcomes in patients with multiple myeloma. The novel agent-based induction, followed by autologous transplantation, is considered as the standard treatment for transplant-eligible patients. Post-transplant consolidation and maintenance therapy can help maintain the subsequent response and further improve the treatment outcome in patients. Currently, there are several validated sensitive assays evaluating minimal residual disease (MRD), which have provided a means to quantitatively assess residual disease and accurately predict its prognosis in terms of progression-free and overall survival. Novel clinical studies that formally assess the effect of MRD negativity on clinical decision-making are ongoing. This session aims to provide an in-depth and comprehensive summary of the latest treatment strategy and MRD-based knowledge in newly diagnosed transplant-eligible patients with multiple myeloma.

The treatment paradigm in multiple myeloma (MM) together with the introduction of novel agents have resulted in a considerably improved survival. However, the disease is still considered incurable. One of the factors of its recurrence was that acquired genomic events associated with the progression of MM lead to inter- and intrapatient clonal heterogeneities. Also, just like many other cancers, MM contains cancer stem cells, a rare subpopulation of MM cells that exhibit the capacity for self-renewal and differentiation, but also pronounced drug resistance. Furthermore, a growing body of evidence suggests the role of tumor microenvironment and anti-myeloma immune status in the progression and maintenance of MM. Despite much progress in MM pathology, there are still several issues left unsolved. In this review, we will discuss the recent advances in our understanding of the pathology of MM from the perspective of tumor cell-of-origin and how these advances can lead to more effective therapies targeting MM.

The treatment strategy of adult idiopathic thrombocytopenic purpura (ITP) in Japan had consisted of corticosteroids as the first-line option, splenectomy as the second-line option, and others as the third-line option, respectively, for a long time. However, thrombopoietin receptor agonists (TPO-RAs) have been widely adopted recently for corticosteroid-resistant ITP, and indications for rituximab have been extended to adult ITP in Japan, suggesting that ITP treatment is dramatically changing. In the “Reference guide for adult ITP treatments in Japan” revised in 2019, TPO-RAs and rituximab are equally recommended as second-line treatments alongside splenectomy. It is suggested to select from among the second-line treatments with careful consideration of not only their advantages and disadvantages but also aspects of the condition and situation of each patient such as any comorbidities or lifestyle factors. Moreover, since multiple effective therapeutic options are now available as second-line options, it is preferable to consider an early transition to second-line treatments for corticosteroid-refractory/dependent ITP patients.

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) caused by ADAMTS13 deficiency. Although the name of TTP is well known, most hematologists find its diagnosis and treatment difficult because it is ultrarare. TTP is an acute-onset and fatal disorder. Approximately 90% of TTP patients die within 2 weeks of onset without proper medical treatment. Although most doctors may remember being taught the five TTP symptoms (fever, transient central nervous system symptoms, hemolytic anemia, thrombocytopenia, and kidney dysfunction) at medical school, only 7% of TTP patients present with all five symptoms. Thus, TTP must be suspected in patients with microangiopathic hemolytic anemia and thrombocytopenia, and plasma therapy must be initiated as soon as possible after ordering the ADAMTS13 test. In this article, I describe how to differentially diagnose TMA as well as the standard and the updated therapy, such as rituximab and caplacizumab, for TTP treatment.

Hemophilia A and B are hereditary coagulation disorders caused by functional and quantitative abnormalities of coagulation factor VIII (FVIII) in hemophilia A and coagulation factor IX (FIX) in hemophilia B. A definitive diagnosis is made through the measurement of FVIII or FIX activity and ruling out other pathological conditions or diseases with decreased FVIII or FIX activity. Severity is classified as severe, moderate, and mild according to factor activity level. Moreover, as frequency of hemorrhage and severity are usually correlated, severe patients have a high risk of intracranial hemorrhage during infancy as well as joint damage due to recurrent hemarthrosis. However, there are some non-severe patients who have symptoms like bleeding and joint damage. Therefore, it is necessary to determine the treatment strategy not only based on severity but also on bleeding symptoms. The treatment for hemophilia is mainly replacement therapy using clotting factor concentrates (standard or extended half-life), such as prophylaxis or on-demand therapy for bleeding. However, there are also clinical problems, such as venous access and development of inhibitors. Recently, a non-factor agent has emerged as a new treatment option. Thus, the management of hemophilia is on a turning point.

Recent advances in real-time imaging techniques have greatly contributed to the full understanding of the role of functional molecules and distinctive cells. When the vascular wall is injured, platelet thrombus is immediately formed, and the subsequent fibrin formation strengthens the thrombus to prevent bleeding. These sequential reactions are well coordinated; therefore, vascular occlusion is less likely to occur as an unnecessary thrombus is not formed or quickly lysed. Real-time imaging analyses in a vascular injury mouse model and in vitro human platelet-containing plasma clot model enabled us to visualize dynamic behaviors of individual factors. In addition to impaired hemostasis, immature lysis due to impaired fibrinolysis inhibition seemed to be involved in the pathological changes in hemophilic arthropathy in hemophilia. Further imaging analysis could elucidate the spatiotemporal crosstalk regulatory mechanisms in more detail with regard to thrombus formation and dissolution.

Although antiplatelet drugs are widely used for the prevention and treatment of atherothrombosis, clinical tests capable of evaluating their efficacy have not been established. Focusing on platelet aggregates in blood, we announced the world’s first basic technology, an intelligent Image-Activated Cell Sorter (iIACS), that can exhaustively and rapidly identify cells one-by-one using image analysis with high-speed imaging and deep learning to sort specific cells according to the analysis results. This technology has even enabled the detection of single platelets with a size of 2 µm in blood samples and the quantification of the proportion of platelet aggregates by size. Furthermore, by applying this technique, we discovered different morphological features of platelet aggregates formed by different types of agonists that activate platelets. Here, we discuss this application in the early diagnosis of thrombotic microangiopathy (TMA). In the early stage of TMA, consumptive thrombocytopenia is caused by excessive platelet activation. Therefore, the detection of excessive platelet aggregates can lead to early TMA diagnosis.

Lymphoproliferative disease (LPD) is a comprehensive concept covering diseases ranging from transient lymphadenopathy to lymphoma. LPD is frequently associated with Epstein-Barr virus (EBV) infections and tends to occur in patients with inborn errors of immunity (IEI) and in patients after organ transplantation. Most patients with severe combined immunodeficiency or X-linked lymphoproliferative disease develop LPD. Autoimmune lymphoproliferative syndrome (ALPS), a typical LPD disease, is caused by germline mutations in FAS, FASL, CASP10, CASP8 and FADD, which are involved in the apoptosis pathway. ALPS patients develop autoimmune diseases and LPDs such as hepatosplenomegaly and lymphadenopathy. On the other hand, RAS-associated ALPS-like syndrome and CTLA4 haploinsufficiency also belong to ALPS-associated diseases. EBV-associated LPD is a clinical condition that should be noted in patients with IEI. Patients with genetic defects in SH2D1A, XIAP, CD27, CD70, CD137, ITK, CTPS, RASGRP1, and MAGT1 are prone to EBV-associated LPD.

Evidence of the molecular epidemiology of thrombophilia is growing, and the clinical management of adult thromboembolism patients has recently made significant progress. On the other hand, there is little or no evidence concerning the genetic variation, treatment, and prophylaxis of thromboembolism development in the early life stage. The clinical presentation of early-onset thrombosis/thrombophilia, which mostly occurs in newborns and adolescents, differs from that in cases of adult-onset. Recurrent purpura fulminans and/or intracranial hemorrhage/infarction leads to dangerous lifelong complications. As in the setting of cancer genomic medicine, germline variants require determination for the individualized control of early-onset thrombophilia. The genetic predisposition to thrombosis varies among ethnicities. In the Japanese population, the protein S variant (PS-Tokushima, K196E) has attracted attention as the cause of a common and low-risk prothrombotic predisposition in adults, while protein C deficiency greatly impacts the onset of pediatric thrombosis. In 2020, 3 years after the registration of idiopathic thrombosis as a designated intractable disease, genetic tests have been promulgated for health insurance portability. Disease-specific therapy for early-onset thrombophilia is crucial. Here, we review the genetic heterogeneity, prophylaxis, and treatment strategy of the rare subgroups of severe heritable thrombosis conditions in Japan.

Myeloid leukemia with Down syndrome (ML-DS) demonstrates unique characteristics such as the predominance of FAB M7, an age predilection during the first 4 years of life, and higher sensitivity to chemotherapeutic agents, which translate into a good treatment response as well as increased treatment-related toxicities. Consequently, patients with ML-DS have traditionally been treated separately from non-DS acute myeloid leukemia (AML) children. The 3-year event-free survival rates in recent clinical studies in the Western countries and Japan are all more than 85%. In Japan, two studies (AML-D05 and AML-D11) were conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group. The efficacy of risk-oriented therapy according to morphological response was evaluated in the AML-D05 study. Despite that a dose reduction of chemotherapeutic agents could be performed in many cases, the overall outcome was comparable with those of previous Japanese studies. In the subsequent AML-D11 study, the role of minimal residual disease (MRD) was evaluated. MRD by flow cytometry (FCM) and targeted deep sequencing of GATA1 following the initial induction therapy were significant prognostic factors for predicting relapse. Dose modification according to the end-of-induction FCM-MRD is being attempted in the ongoing JCCG AML-D16 study.

Allogeneic hematopoietic stem cell transplantation (HSCT) from a human leukocyte antigen (HLA)-matched related donor is an effective treatment option for sever aplastic anemia (SAA). HSCT from an unrelated donor has also been reported. Engraftment failure and graft-versus-host disease (GVHD) are major obstacles in HSCT for SAA, and the combination of high-dose cyclophosphamide (CY) and anti-thymocyte globulin (ATG) has been utilized as a conditioning regimen for overcoming these obstacles. However, cardiac toxicity due to high-dose CY has been a major challenge, and the reduction of CY with the addition of fludarabine (Flu) has recently been considered to decrease toxicity. In Kanto Study Group for Cell Therapy (KSGCT), a prospective study using Flu, reduced-dose CY, and low-dose thymoglobulin as a conditioning regimen was performed, which demonstrated a promising result with the overall survival rate of 96.3% at one year. However, it should be noted that the use of Flu may affect the occurrence of secondary graft failure. Outcomes in HSCT from alternative donors, including cord blood and haploidentical-related donors, are improving. Therefore, we have more options in HSCT for SAA.

Graft-versus-host disease (GVHD) is one of the most important complications after an allogeneic hematopoietic stem cell transplantation (allo-SCT). The current National Institutes of Health's (NIH) consensus is that clinical manifestations, and not the time to symptomatic onset after transplantation, determine whether the clinical syndrome of GVHD is considered acute or chronic. In the past decade, peripheral blood stem cell transplantation from an unrelated donor can be performed in Japan. Furthermore, poor-risk patients without human leukocyte antigen (HLA)-matched donor can receive allo-SCT from HLA haploidentical donor. Therefore, severe or steroid-refractory GVHD would be increased. Corticosteroid, at a dose of 2 mg/kg, is a standard first-line therapy for acute GVHD. If there is no improvement after the first-line therapy, second-line therapy should be administered immediately. Although anti-thymocyte globulin and mesenchymal stem cells are covered by health insurance in Japan, another treatment options should be determined for steroid-refractory acute GVHD. Furthermore, severe chronic GVHD increases patients' mortality and decreases their quality of life. A number of novel drugs targeting specific biological pathways for GVHD are under development. Currently, more than 60 clinical trials are carried out for the treatment of steroid-refractory GVHD worldwide for drug approval. The accumulation of novel evidence for GVHD treatment is expected to be established.

Posttransplant cyclophosphamide (PTCy) was initially developed by the Johns Hopkins group as a graft-versus-host disease (GVHD) prophylaxis for human leukocyte antigen (HLA)-haploidentical stem cell transplantation. Recently, PTCy has been attempted in HLA-matched transplantation. In HLA-haploidentical hematopoietic transplantation, several retrospective studies have compared HLA-matched transplantation with HLA-haploidentical hematopoietic transplantation using PTCy. In these reports, transplantation outcomes have been comparable. Therefore, PTCy- based haploidentical transplantation is a viable alternative to HLA-matched transplantation. Moreover, In HLA-matched transplantation, PTCy alone may be sufficient in the prevention of GVHD in HLA-matched bone marrow transplantation. Although PTCy alone is not enough in HLA-matched peripheral blood stem cell transplantation, PTCy has demonstrated excellent GVHD inhibition when combined with several immunosuppressive agents, such as calcineurin inhibitor and mycophenolate mofetil. Furthermore, PTCy also playing a significant role in other areas, such as aplastic anemia, salvage transplantation for graft failure, and allogeneic transplantation after checkpoint inhibitor use. PTCy can be performed inexpensively and without any special equipment or techniques at any institution. It is expected that PTCy will continue to spread worldwide in the future.