We have recently described the identification of a novel inherited bone marrow failure syndrome. The first set of patients was diagnosed through the exome analysis of cells from Japanese patients with hypoplastic anemia, which have been deposited to the JCRB cell bank for quite some time previously. Originally, these cases were diagnosed with a novel disorder based on increased levels of sister chromatid exchanges in lymphocytes; however, causative genes were clarified only after applying the recently developed next-generation sequencing technology. Aldehyde degradation deficiency syndrome (ADDS) is caused by combined defects in two genes, ADH5 and ALDH2, which are both critical for degrading endogenously generated formaldehyde. Formaldehyde is highly reactive and toxic to biological molecules including DNA, and its endogenous generation in the absence of the degradation system results in DNA damage that overwhelms the DNA repair capacity, leading to the development of BMF with loss of hematopoietic stem cells and progression to MDS/leukemia. In this short review, we would like to summarize what is known today about ADDS for a wide readership of hematology clinicians in Japan.

Chylothorax is a rare clinical sign in patients with diffuse large B-cell lymphoma (DLBCL), which is often challenging to manage and has a poor prognosis. We report the case of a 59-year-old woman who presented with right pleural effusion at the time of DLBCL diagnosis. Lymphadenopathy rapidly improved in response to chemotherapy. However, the pleural effusion progressed and was identified as chylothorax by thoracentesis. Because attempts to manage the condition with fasting and central venous nutrition were unsuccessful, we performed ultrasound-guided intranodal lipiodol lymphangiography from the inguinal lymph node. Although leak sites were not detected, the pleural effusion markedly improved on the day after the examination and resolved after 2 months. Lymphangiography is a minimally invasive examination with few complications. It contributes not only to the identification of leak sites but also to the improvement and resolution of chylothorax. Therefore, lymphangiography should be considered for refractory chylothorax that is unresponsive to chemotherapy or nutritional management.

Acute myeloid leukemia (AML) is a heterogeneous disease, and recent advances in sequencing technology have revealed that the accumulation of various genetic abnormalities is deeply involved in the pathogenesis of AML and its clonal evolutions during disease progression. Prognostic classifications and therapeutic strategies based on the cytogenetic and genetic abnormalities have been proposed, and several new therapeutic agents targeting the molecular abnormalities have been energetically investigated to eliminate AML cells. In the last few years, several new agents, including FLT3, IDH, BCL-2, and Hedgehog inhibitors, have been approved for the treatment of newly diagnosed AML, and their clinical applications have begun in the United States. Although there has been a delay of several years, the clinical development of these new agents is also underway in Japan, and it is expected that a new era of AML treatment will begin in the near future. It is necessary to establish novel risk-adopted treatment strategies incorporating these agents in monotherapies and/or effectively designed combination therapies.

BCR-ABL tyrosine kinase inhibitors (TKIs) dramatically improve the chronic myeloid leukemia (CML) prognosis, and most CML patients in the chronic phase are now able to lead lives that are comparable to those of healthy individuals. However, the high cost and adverse effects associated with long-term treatment remain issues in the treatment of CML patients. At the setout, a clinical study involving the discontinuation of imatinib was conducted in France. Thereafter, several TKI stop studies of first-generation (imatinib) and second-generation TKIs (dasatinib, nilotinib) have shown an earlier response than that with imatinib. These studies revealed that almost 50% of CML patients who were treated with TKIs and achieved a certain period of sustained deep molecular response can stop TKIs safely and obtain sustained treatment-free remission (TFR). Adverse effects of TKI withdrawal and predicting factors for successful discontinuation including immunity are gradually becoming clear via these studies. For superior CML treatment, several promising agents, including ABL001, are being developed. I trust that these efforts will enable CML patients to maintain TFR in the near future.

After the discovery of driver mutations for myeloproliferative neoplasms (MPN), treatment approach for the disease has achieved tremendous progress. Ruxolitinib, a JAK inhibitor, is now widely used for both patients with myelofibrosis and polycythemia vera in several countries, including Japan. Fedratinib, another JAK inhibitor, has been recently approved in the United States. One of the biggest limitations of treatment with JAK inhibitors is the relatively small proportion of patients who achieve a complete molecular response. Furthermore, most of the patients with myelofibrosis had to discontinue the treatment due to drug-related adverse events or disease progression. Therefore, MPN treatment is still at an early and challenging stage, thereby highlighting the urgent need for establishment of a new and more effective therapeutic strategy. One of the promising candidates for MPN treatment is the use of interferons. Modern forms of interferons demonstrate not only a good hematological response but also a deep molecular response, eradicating abnormal MPN clones harboring driver mutations. A number of new agents targeting molecules outside of the JAK-STAT pathway, PI3kinase, NF-kB, or Bcl-2 family of anti-apoptotic proteins are also being considered and tested in clinical studies as single-agent therapies or in combination with JAK inhibitors.

A human leukocyte antigen (HLA)-matched related donor is considered as the first donor candidate in case of allogenic hematopoietic stem cell transplantation (allo-HSCT). Given the declining birthrate and aging population in Japan, the number of sibling donors is also decreasing. Hence, candidates other than HLA-matched siblings, named “alternative donors,” have attracted increasing attention. Improved graft-versus-host disease (GvHD) prophylaxis with posttransplant cyclophosphamide or pretransplant antithymocyte globulin represented a major breakthrough in allo-HSCT with alternative donors by overcoming the barriers of HLA mismatch. In addition, there have been improved outcomes of unrelated cord blood transplantation, owing to better unit selection along with improved GvHD prophylaxis and supporting strategies. These changes have expanded the range of donor options and consequently, increased donor availability at the critical moment for allo-HSCT. The next challenge that warrants further investigation is the development of personalized strategies to select the best donor from the available multiple options according to the status of each patient.

Acute graft-versus-host disease (GVHD) is a systemic immune reaction in which mature T cells in the donor inoculum are abnormally activated by the host and donor antigen-presenting cells. These activated cells then attack normal host tissue after allogeneic hematopoietic stem cell transplantation (HSCT). Clinical GVHD develops when the damage exceeds the threshold for tissue tolerance. Furthermore, functional damage of hematopoietic and non-hematopoietic organs due to this acute immune response triggers the subsequent development of chronic GVHD. The endpoint of HSCT is shifting from just surviving the acute phase to having an enriched life until later years; therefore, seamless and detailed immune management is required from the acute to chronic phase after HSCT. Acute GVHD prophylaxis consisted of calcineurin inhibitors and short-term methotrexate for a long time. However, various novel immune-modulating strategies have been developed against the background of recent diversification in donor sources and changes in treatment goals. In this review, we discuss recent clinical developments in basic and clinical research regarding acute or chronic GVHD.

Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative treatment strategy; however, long-term survivors of allo-HCT are at risk of experiencing late adverse effects, including chronic graft-versus-host disease, immunocompromised status, endocrine diseases, secondary cancers, and psychosocial issues. Long-term follow-up (LTFU) clinics for patients who have undergone allo-HCT play a role in the screening and prevention of these late effects. We conducted a nationwide questionnaire survey to characterize the current operation of LTFU clinics in Japan and showed that the establishment rate of LTFU clinics in 188 participating centers was 63%. The influencing factors in the establishment or management of long-term follow-up clinics were analyzed. Several factors were extracted, such as “lack of human resources” and “patients’ and physicians’ lack of understanding of the importance of LTFU” as inhibiting factors and “utilization of tools” as a promoting factor. The development of common LTFU tools, introduction of an electronic patient-reported outcome system, and further increase in the number of certified staff might facilitate the establishment of an efficient and sustainable LTFU system.

CD19 chimeric antigen receptor (CAR) T cell therapy is effective in B cell leukemia and lymphoma. Many researchers are attempting to develop CAR T cells for different types of cancer. B cell maturation antigen (BCMA) is shown to be a promising target for multiple myeloma (MM). However, the treatment for MM remains challenging, and many researchers are trying to identify better target molecules for MM treatment. We have reported that activated integrin β7 is an excellent target for CAR T cells against MM and are currently performing a clinical trial.

Diffuse large B-cell lymphoma (DLBCL) represents a largest number of entities among lymphoid cancers, which are an aggregate of clinically and biologically diverse diseases. In particular, it is believed that various molecular genetic abnormalities are involved in the tumorigenesis of disease development. Owing to recent developments in multiomics analyses, gene expression profile reflecting cell-of-origin and tumor microenvironment and recurrent genetic abnormalities have been discovered; this is an important aspect for the development of future new therapeutic drugs and indications for clinical trials, ultimately encouraging precision medicine in the area of DLBCL. Here, we discuss the possibility of patient stratification based on genetic abnormality.

Intravascular large B-cell lymphoma is a rare disease entity of extranodal large B-cell lymphoma and is characterized by selective growth of tumor cells in the lumina of small vessels in systemic organs. The challenge in obtaining sufficient tumor cells from biopsy specimens has hampered the elucidation of underlying biology. Recent advances in xenograft models and plasma cell-free DNA have revealed that the intravascular large B-cell lymphoma has genetic features similar to those of activated B-cell-like diffuse large B-cell lymphoma and frequent genetic alterations in immune-check point related genes. In terms of clinical aspects, considering the improvement in the clinical outcomes and higher risk of secondary central nervous system (CNS) involvement in the rituximab era, phase 2 trial of R-CHOP therapy combined with high-dose methotrexate and intrathecal chemotherapy as CNS-oriented therapy was conducted. The trial, named the PRIMEUR-IVL study, displayed good progression-free survival and low cumulative incidence of secondary CNS involvement. Further research is necessary to enable a deeper understanding of the pathophysiology of the disease and further improve the clinical outcomes.

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype, and nearly 70% of patients may be cured by administering R-CHOP therapy. However, R-CHOP is found to be inadequate in approximately one-third of the DLBCL cases, and refractory disease to R-CHOP is usually associated with a major cause of mortality. Therefore, it is essential to improve the efficacy of initial treatment in order to avoid unfavorable outcomes in patients with refractory DLBCL. In general, R-CHOP comprises of CHOP regimen that is repeated every 3 weeks and adding one-dose rituximab in each cycle. Although this combination method of rituximab with CHOP is effective and convenient, it does not contain enough scientific rationale and the schedule of rituximab administration has not been optimized. The pharmacokinetics of rituximab differs substantially among individuals and its serum half-life is approximately more than 500 hours; therefore, the peak concentration increases cumulatively by weekly infusion. A previous study revealed that patients with high blood concentration of rituximab showed higher response rate and longer progression-free survival. These findings suggest that the retention of higher levels of rituximab concentration and combination with chemotherapy during an early treatment period may bring about improvement of treatment effect. The HOVON group and Japan Clinical Oncology Group conducted randomized phase III studies to evaluate the efficacy of the dose-dense rituximab strategy for untreated DLBCL.