Low incidences of acute and chronic graft-versus-host disease after unrelated bone marrow transplantation with low-dose anti-T lymphocyte globulin

In-vivo or ex-vivo T cell depletion or both to prevent graft-versus-host disease after hematopoietic stem cell transplantation

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) represents a widely accepted therapeutic strategy for the treatment of hematologic disorders which are otherwise considered incurable. Alloreactive T cells infused with the stem cell inoculum may generate graft-versus-host disease (GVHD) representing one the most relevant obstacles to the successful outcome of patients receiving allogeneic HSCT. Areas covered: In this review, the authors provide an overview of the most recent approaches of T-cell depletion (TCD) including ex-vivo αβ+ TCD and in-vivo TCD with anti-thymocyte globulin (ATG). Expert opinion: Ex vivo depletion of donor T-cells prevents both acute and chronic GVHD without the need for any additional posttransplant immunological prophylaxis either in haploidentical HSCT and HLA matched transplants. Three prospective trials evaluating the efficacy of ATG in matched unrelated donor transplant recipients demonstrated that ATG reduces the incidence of both acute and chronic GVHD without a significant increase of relapse rate, and similar results have been reported in the setting of blood stem cell grafts from matched sibling donors.

Friend or foe? Mogamulizumab in allogeneic hematopoietic stem cell transplantation for adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL/ATLL) is a peripheral T-cell neoplasm associated with human T-lymphotropic virus type-1 (HTLV-1). Even the currently most intensive chemotherapy regimen modified LSG15 (mLSG15, VCAP-AMP-VECP) results in a dismal clinical outcome, with a median overall survival of only around 1 year. Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) may lead to long-term remission in a proportion of patients with aggressive ATL, the clinical outcome in patients with refractory or relapsed ATL is unsatisfactory. The anti-CCR4 antibody mogamulizumab (moga) has been recently approved for ATL in Japan, and it is effective in a significant proportion of patients with refractory or relapsed ATL. However, there are major concerns about the harmful influences of pretransplant moga on the immune reconstitution after allo-HSCT. Specifically, moga depletes regulatory T cells (Tregs) for at least a few months, which may increase the risk of graft-versus-host disease (GVHD) after allo-HSCT. A recent retrospective study from Japan clearly showed that pretransplant moga increased the risk of severe and steroid-refractory GVHD, which led to increases in non-relapse mortality and overall mortality. To improve the overall clinical outcome in patients with relapsed or refractory ATL, more studies are needed to incorporate moga without increasing adverse effects on the clinical outcome after allo-HSCT. In this review, we aim to provide an updated summary of the research related to moga and allo-HSCT.

Impact of low-dose rabbit anti-thymocyte globulin in unrelated hematopoietic stem cell transplantation

We retrospectively evaluated the outcome of administering low-dose rabbit anti-thymocyte globulin (thymoglobulin: ATG-T) to 219 patients (ATG-T group, n = 30; no-ATG-T group, n = 189) who received an initial unrelated hematopoietic stem cell transplantation (uHSCT). The median total dose of ATG-T was 1.5 mg/kg. There was no significant difference in the cumulative incidences of grade II-IV (42 vs. 38 %, P = 0.87) and grade III-IV (5 vs. 7 %, P = 0.52) acute GVHD. In patients who received uHSCT from a donor with at least one HLA allele mismatch, the cumulative incidence of extensive chronic GVHD was significantly lower in the ATG-T group than that in the no-ATG-T group (13 vs. 44 %, P = 0.02). No patient in the ATG-T group developed chronic lung dysfunction. The probabilities of 1-year, GVHD-free/relapse-free survival (GRFS) were 61 % in the ATG-T group and 35 % in the no-ATG-T group (P = 0.02). Patients in the ATG-T group discontinued immunosuppressive drugs significantly earlier than those in the no-ATG-T group (P < 0.01). The use of low-dose ATG-T did not increase the incidence of severe infectious disease. The use of low-dose ATG-T in patients who received uHSCT was associated with a superior GRFS, reflecting the reduced incidence of severe/persistent GVHD without compromising overall survival.

Pediatric chronic myeloid leukemia is a unique disease that requires a different approach

Chronic myelogenous leukemia (CML) in children is relatively rare. Because of a lack of robust clinical study evidence, management of CML in children is not standardized and often follows guidelines developed for adults. Children and young adults tend to have a more aggressive clinical presentation than older adults, and prognostic scores for adult CML do not apply to children. CML in children has been considered to have the same biology as in adults, but recent data indicate that some genetic differences exist in pediatric and adult CML. Because children with CML may receive tyrosine kinase inhibitor (TKI) therapy for many decades, and are exposed to TKIs during a period of active growth, morbidities in children with CML may be distinct from those in adults and require careful monitoring. Aggressive strategies, such as eradication of CML stem cells with limited duration and intensive regimens of chemotherapy and TKIs, may be more advantageous in children as a way to avoid lifelong exposure to TKIs and their associated adverse effects. Blood and marrow transplantation in pediatric CML is currently indicated only for recurrent progressive disease, and the acute and long-term toxicities of this option should be carefully evaluated against the complications associated with lifelong use of TKIs.

B-cell function after unrelated umbilical cord blood transplantation using a minimal-intensity conditioning regimen in patients with X-SCID

Patients with X-linked severe combined immunodeficiency (X-SCID) suffer from severe and persistent infections, and usually die early in life unless treated by hematopoietic stem cell transplantation. If a patient has an HLA-identical sibling donor, preparative conditioning is not necessary for T-cell engraftment and B-cell function. However, in the absence of such a donor, long-term reconstitution of full B-cell function is often problematic, leading in many cases to a lifetime requirement for immunoglobulin replacement therapy. Preparative myeloablative conditioning has been shown to improve long-term B-cell function, but may aggravate pre-existing infection and transplant-related toxicity. It is thus important to determine the minimum intensity of conditioning that assures immunoglobulin production. In the present study, we performed reduced-intensity conditioning (RIC), consisting of fludarabine 125 mg/m(2) and melphalan 80 mg/m(2), prior to unrelated umbilical cord blood transplantation (UCBT) for five patients with X-SCID, none of them had an HLA-identical donor. Four patients survived more than 4 years without sequelae, and none required long-term immunoglobulin replacement therapy. One patient succumbed to sepsis in conjunction with severe GVHD. Our result demonstrates that the RIC regimen described above in combination with UCBT is an effective and less toxic conditioning to correct B-cell function in patients with X-SCID.

Role of non-HLA gene polymorphisms in graft-versus-host disease

A large number of reports have associated various non-HLA gene polymorphisms with the risk and severity of graft-versus-host disease (GVHD). To date, candidate gene studies and genome-wide association studies have been performed to investigate such non-HLA gene polymorphisms in relation to GVHD. Candidate gene studies are hypothesis-driven and cost-effective, whereas genome-wide association studies have the potential to discover new gene polymorphisms, including possible biomarkers and therapeutic targets. Some gene polymorphisms have the potential to affect protein function or gene expression, or to encode minor histocompatibility antigens. Non-HLA genotyping for genes influencing GVHD prior to transplantation should provide useful information that will facilitate choosing the donor, type of graft, conditioning treatment, and GVHD prophylaxis. However, attention should be paid to the need for validation studies and ethical issues.