Syngeneic transplantation in aplastic anemia: pre-transplant conditioning and peripheral blood are associated with improved engraftment: an observational study on behalf of the Severe Aplastic Anemia and Pediatric Diseases Working Parties of the European Group for Blood and Marrow Transplantation

The state of the art in the treatment of severe aplastic anemia: immunotherapy and hematopoietic cell transplantation in children and adults

Acquired aplastic anemia (AA) is an immune-mediated bone marrow (BM) failure where marrow disruption is driven by a cytotoxic T-cell-mediated autoimmune attack against hematopoietic stem cells. The key diagnostic challenge in children, but also in adults, is to exclude the possible underlying congenital condition and myelodysplasia. The choice of treatment options, either allogeneic hematopoietic cell transplantation (alloHCT) or immunosuppressive therapy (IST), depends on the patient's age, comorbidities, and access to a suitable donor and effective therapeutic agents. Since 2022, horse antithymocyte globulin (hATG) has been available again in Europe and is recommended for IST as a more effective option than rabbit ATG. Therefore, an update on immunosuppressive strategies is warranted. Despite an improved response to the new immunosuppression protocols with hATG and eltrombopag, some patients are not cured or remain at risk of aplasia relapse or clonal evolution and require postponed alloHCT. The transplantation field has evolved, becoming safer and more accessible. Upfront alloHCT from unrelated donors is becoming a tempting option. With the use of posttransplant cyclophosphamide, haploidentical HCT offers promising outcomes also in AA. In this paper, we present the state of the art in the management of severe AA for pediatric and adult patients based on the available guidelines and recently published studies.

HLA Class I Allele Loss and Bone Marrow Transplantation Outcomes in Immune Aplastic Anemia

In patients with immune-mediated acquired aplastic anemia (AA), HLA class I alleles often disappear from the surface of hematopoietic progenitor cells, potentially enabling evasion from cytotoxic T lymphocyte-mediated pathogenesis. Although HLA class I allele loss has been studied in AA patients treated with immunosuppressive therapy (IST), its impact on allogeneic bone marrow transplantation (BMT) has not been thoroughly investigated. The purpose of this study was to evaluate the clinical implications of HLA class I allele loss in patients with acquired AA undergoing allogeneic BMT. The study enrolled acquired AA patients who underwent initial BMT from unrelated donors through the Japan Marrow Donor Program between 1993 and 2011. The presence of HLA class I allele loss due to loss of heterozygosity (HLA-LOH) was assessed using pretransplantation blood DNA and correlated with clinical data obtained from the Japanese Transplant Registry Unified Management Program. A total of 432 patients with acquired AA were included in the study, and HLA-LOH was detected in 20 of the 178 patients (11%) available for analysis. Patients with HLA-LOH typically presented with more severe AA at diagnosis (P = .017) and underwent BMT earlier (P < .0001) compared to those without HLA-LOH. They also showed a slight but significant recovery in platelet count from the time of diagnosis to BMT (P = .00085). However, HLA-LOH status had no significant effect on survival, engraftment, graft failure, chimerism status, graft-versus-host disease, or other complications following BMT, even when the 20 HLA-LOH+ patients were compared with the 40 propensity score-matched HLA-LOH- patients. Nevertheless, patients lacking HLA-A*02:06 or HLA-B*40:02, the alleles most frequently lost and associated with a better IST response, showed higher survival rates compared to those lacking other alleles, with estimated 5-year overall survival (OS) rates of 100% and 44%, respectively (P = .0042). In addition, in a specific subset of HLA-LOH- patients showing clinical features similar to HLA-LOH+ patients, the HLA-A*02:06 and HLA-B*40:02 allele genotypes correlated with better survival rates compared with other allele genotypes, with estimated 5-year OS rates of 100% and 43%, respectively (P = .0096). However, this genotype correlation did not extend to all patients, suggesting that immunopathogenic mechanisms linked to the loss of certain HLA alleles, rather than the HLA genotypes themselves, influence survival outcomes. The survival benefit associated with the loss of these two alleles was confirmed in a multivariable Cox regression model. The observed correlations between HLA loss and the pretransplantation clinical manifestations and between loss of specific HLA class I alleles and survival outcomes in AA patients may improve patient selection for unrelated BMT and facilitate further investigations into the immune pathophysiology of the disease.

Guidelines for the diagnosis and management of adult aplastic anaemia: A British Society for Haematology Guideline

Pancytopenia with hypocellular bone marrow is the hallmark of aplastic anaemia (AA) and the diagnosis is confirmed after careful evaluation, following exclusion of alternate diagnosis including hypoplastic myelodysplastic syndromes. Emerging use of molecular cyto-genomics is helpful in delineating immune mediated AA from inherited bone marrow failures (IBMF). Camitta criteria is used to assess disease severity, which along with age and availability of human leucocyte antigen compatible donor are determinants for therapeutic decisions. Supportive care with blood and platelet transfusion support, along with anti-microbial prophylaxis and prompt management of opportunistic infections remain key throughout the disease course. The standard first-line treatment for newly diagnosed acquired severe/very severe AA patients is horse anti-thymocyte globulin and ciclosporin-based immunosuppressive therapy (IST) with eltrombopag or allogeneic haemopoietic stem cell transplant (HSCT) from a matched sibling donor. Unrelated donor HSCT in adults should be considered after lack of response to IST, and up front for young adults with severe infections and a readily available matched unrelated donor. Management of IBMF, AA in pregnancy and in elderly require special attention. In view of the rarity of AA and complexity of management, appropriate discussion in multidisciplinary meetings and involvement of expert centres is strongly recommended to improve patient outcomes.

Severe aplastic anemia and a healthy pregnancy immediately following syngeneic transplantation: An extremely rare case report

Aplastic anemia is potentially fatal, particularly if the disease does not respond to immunotherapy and progresses to severe pancytopenia. Allogeneic hematopoietic stem cell transplant from an HLA-matched sibling donor, the first-line treatment in patients younger than 40 years, is used as a curative treatment option in severe aplastic anemia. The availability of an identical twin donor is infrequent, and there is limited experience in this context. Additionally, the choices for a conditioning regimen for a syngeneic transplant to prevent engraftment failure and the necessity of graft-vs-host disease prophylaxis are controversial. Although long-term survival gradually increases after an allogeneic hematopoietic stem cell transplant, hypogonadism and infertility are the main problems that significantly affect patients' quality of life. We present a patient diagnosed with severe aplastic anemia who has had a healthy pregnancy immediately after a syngeneic transplant.

What Causes Aplastic Anaemia: Results of Transplants from Genetically-Identical Twins

Background

Aplastic anaemia has diverse aetiologies. Distinguishing between these is, in part, testable by analyzing results of haematopoietic cells transplants between genetically-identical twins one of whom has aplastic anaemia.

Objective

Describe outcomes of genetically-identical twin transplants for aplastic anaemia with and without pretransplant conditioning.

Methods

We interrogated data from an observational database of 59 consecutive recipients of genetically-identical twin transplants for aplastic anaemia reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) 2000-2019.

Results

38 subjects were male. Median age was 18 years (Interquartile Range [IQR], 11-32 years). Median interval from diagnosis to transplant was 2 months (IQR 1-3 months). 11 subjects received a 1st transplant without pretransplant conditioning. 2 of recovered normal bone marrow function. The other 9 received a 2nd transplant with pretransplant conditioning 7 of whom recovered. 48 subjects received pretransplant conditioning before a 1st or 2nd transplant all of whom recovered.

Conclusion

Only some genetically-identical twins with aplastic anaemia recover normal bone marrow function after a 1st haematopoietic cell transplant without pretransplant conditioning whereas most subjects recover when a transplant is preceded by pretransplant conditioning. These data are consistent with an immune-mediated aetiology of aplastic anaemia in most cases.

The late outcomes of syngeneic hematopoietic stem cell transplantation in patients with blood disorders

Introduction. Syngeneic hematopoietic stem cell transplantation is a type of allogeneic stem cell transplantation when the donor of stem cells is a genetically identical (monozygotic) twin of the recipient. After this type of transplantation, there is no immunological conflict as the graft versus host disease, but at the same time, there is no positive effect of the graft-versus-leukemia effect.

Aim: to assess the overall survival, event-free survival, probability of relapse, and transplant-related mortality rates associated with syngeneic stem cell transplantation.

Patients and methods. In the National Research Center for Hematology from January 1988 to December 2018 we performed 654 allo-HSCT: 17 (2.5%) of them from a syngeneic donor. We performed a «paired analysis» with patients after allo-HSCT from a HLA-identical sibling donor. We included patients after allo-HSCT from an HLA-identical related donor (n = 28) in Group 1 and patients after syngeneic stem cell transplantation in group 2 (n = 14). Patients with aplastic anemia (n = 3) were excluded from the «paired analysis».

Results. Patients after syngeneic stem cell transplantation did not develop a graft-versus-host disease. The relapse developed in 50% of cases (n = 7). Five patients (35.7%) died: 4 of them due to the relapse of the disease, and 1 – due to the graft failure. The relapse probability in patients after syngeneic HSCT was higher and amounted to 18.4% versus 54.2% (p = 0.047) for allo-HSCT from HLA-identical sibling donor and a syngeneic donor, respectively. Overall and event-free survival in patients after syngeneic HSCT is comparable to those in patients after allo-HSCT from an HLA-identical sibling donor.

Conclusion. Syngeneic hematopoietic stem cell transplantation is justified in the absence of another related or unrelated donor of hematopoietic stem cells. The use of myeloablative conditioning regimens, peripheral blood stem cells as a source of stem cells, or high doses of nucleated cells/kg in the case of using bone marrow will improve post-transplant parameters in patients after syngeneic hematopoietic stem cell transplantation.

[Syngeneic hematopoietic stem cell transplantation for aplastic anemia]

目的

评价同基因造血干细胞移植（syn-HSCT）治疗再生障碍性贫血（AA）的疗效。

方法

对11例接受syn-HSCT的AA患者进行回顾性分析。

结果

全部11例AA患者中男4例，女7例，中位年龄为22（7～44）岁。全部11例患者移植后均获得造血重建，中位粒细胞植入时间为10（8～23）d，中位血小板植入时间为11（8～28）d。8例患者获得长期稳定植入，3例患者植入失败，其中2例行二次移植（1例获得到长期稳定植入，另1例造血重建后再次发生植入失败）。中位随访时间为53（5～135）个月，全部11例患者均存活，其中9例患者外周血象长期正常。

结论

syn-HSCT治疗AA可获得良好的长期生存，植入失败仍是有待解决的主要问题。

Allogeneic hematopoietic stem cell transplantation in aplastic anemia: current indications and transplant strategies

Treatment options for newly diagnosed aplastic anemia (AA) patient includes upfront allogeneic hematopoietic stem cell transplant (HSCT) or immunosuppressive therapy (IST). With recent advances in supportive care, conditioning regimens and post-transplant immunosuppression the overall survival for HSCT approaches 70-90%. Transplant eligibility needs to be assessed considering age, comorbidities, donor availability and probability of response to immunosuppressive therapy (IST). Upfront HSCT should be offered to children and young adults with matched related donor (MRD). Upfront HSCT may also be offered to children and young adults with rapidly available matched unrelated donor (MUD) who require urgent HSCT. Bone marrow (BM) graft source and cyclosporine (CsA) plus methotrexate (MTX) as graft versus host disease (GVHD) prophylaxis are preferable when using anti-thymocyte globulin (ATG) based conditioning regimens. Alemtuzumab is an acceptable alternative to ATG and is used with CsA alone and with either BM or peripheral blood stem cells (PBSC). Cyclophosphamide (CY) plus ATG conditioning is preferable for patients receiving MRD transplant, while Fludarabine (Flu) based conditioning is reserved for older adults, those with risk factors of graft failure and those receiving MUD HSCT. For haploidentical transplant, use of low dose radiotherapy and post-transplant cyclophosphamide has resulted in a marked reduction in graft failure and GVHD.

Treatment Effect of Low-Intensity Pulsed Ultrasound on Benzene- and Cyclophosphamide-Induced Aplastic Anemia in Rabbits

BACKGROUND

Transplantation and immunosuppressive therapies are the available treatments for aplastic anemia; however, each strategy has its advantages and disadvantages.

OBJECTIVE

The aim of this study was to find a new strategy for aplastic anemia treatment.

DESIGN

This was an experimental and comparative study.

METHODS

The aplastic anemia model was established by injecting rabbits with benzene and cyclophosphamide. The rabbits with aplastic anemia were divided into low-intensity pulsed ultrasound (LIPUS) and control groups. The distal femoral metaphysis of rabbits in the LIPUS group was treated with ultrasound for 30 days (20 min/d), whereas the control group received a sham treatment. Diarrhea, mortality, and blood cell count were evaluated. The levels of forkhead box P3, interleukin 17, interleukin 4, and interferon gamma were measured using an enzyme-linked immunosorbent assay. Bone marrow hyperplasia was observed by hematoxylin-eosin staining and scanning electron microscopy.

RESULTS

The numbers of red blood cells (RBCs), white blood cells (WBCs), and platelets (PLTs) were lower, the amount of hematopoietic tissue was lower, and the amount of adipose tissue was higher in the rabbit aplastic anemia model than in the normal rabbits. The numbers of RBCs, WBCs, and PLTs increased after LIPUS treatment. The interleukin 17 level decreased, whereas the forkhead box P3 level increased. The amount of hematopoietic tissue increased, whereas the amount of adipose tissue decreased.

LIMITATIONS

The number of hematopoietic stem cells could not be evaluated.

CONCLUSIONS

LIPUS improved the hematopoietic microenvironment, accelerated the reconstruction of bone marrow cells, and increased the quantity and quality of RBCs, WBCs, and PLTs in the peripheral blood. Hence, it can serve as a novel treatment strategy for aplastic anemia in the future.

Successful treatment of severe aplastic anemia with syngeneic stem cell transplantation in the setting of active disseminated mucormycosis

Severe aplastic anemia (SAA) is a hematological disease resulting in pancytopenia due to bone marrow failure. Treatment consists of immunosppressive therapy, or allo-SCT. Patients with aplastic anemia are predisposed to invasive fungal infections due to mucormycosis. Till now, syngeneic SCT in the context of active mucormycosis infection for patients with severe aplastic anemia is lacking in the literature.

Here, we report a case of severe aplastic anemia with disseminated mucormycosis infection undergoing syngeneic transplant.

Improved outcome of haploidentical transplantation in severe aplastic anemia using reduced-intensity fludarabine-based conditioning

Significant improvements in hematopoietic stem cell transplantation (HSCT) with haploidentical family donors (HFD) have confirmed its therapeutic role in severe aplastic anemia (SAA) and led to the evolution of treatment algorithms. However, the optimal conditioning regimen for HFD-HSCT remains undefined, especially the dosage of cyclophosphamide (Cy). A total of 77 patients with SAA from two research centers, who received HFD-HSCT with reduced-intensity fludarabine + cyclophosphamide + thymoglobulin ± busulfan conditioning regimen plus third-party cells infusion were included in this study, of which 67 pairs had 4-5 loci mismatched. We were particularly interested in whether the dosage of Cy significantly impacted graft failure (GF) and overall survival (OS). All patients showed sustained hematopoietic engraftment without any increase in severe aGVHD and transplantation-related mortality (TRM). The incidences of grade II-IV aGVHD, grade III-IV aGVHD and extensive cGVHD were 18%, 10% and 7%, respectively. The probabilities of 1-year and 5-year OS were 93.1% and 87.9%, respectively. Furthermore, patient age <15 years, MNC cells >8×10⁸/kg and donor age <45 years were associated with better survival (P=0.043, P=0.023, and P=0.037, respectively) and engraftment (P=0.019, P=0.008, and P=0.001, respectively). Our findings indicated that SAA patients lack MSD benefited the most if HFD-HSCT was performed with reduced-intensity fludarabine-based conditioning regimen. Improved outcomes with HFD-HSCT may lead to a salvaged therapy and an expanded direct role for SAA in the future.

Long-lasting Remission Induced by Syngeneic Haematopoietic Stem Cell Transplantation in a Patient with Refractory Crohn's Disease

BACKGROUND AND AIMS

Autologous haematopoietic stem cell transplantation (HSCT) is considered a salvage therapy for patients with refractory immune-mediated diseases. Syngeneic HSCT may be an alternative to autologous HSCT, with potential advantages in terms of safety and efficacy.

METHODS

A patient with severe Crohn's disease refractory to available medical therapies underwent a syngeneic HSCT from her identical twin sister. Cyclophosphamide and rabbit anti-thymocyte globulin were administered for conditioning.

RESULTS

After transplant, the patient presented successful engraftment, complete haematological and immunological reconstitution, and no severe complications. The patient achieved complete remission after transplant which is sustained 4 years after transplantation without any active treatment for Crohn's disease.

CONCLUSIONS

Patients with refractory immune-mediated diseases who have an identical disease-free twin may benefit from a syngeneic HSCT.

A promising sword of tomorrow: Human γδ T cell strategies reconcile allo-HSCT complications

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is potentially a curative therapeutic option for hematological malignancies. In clinical practice, transplantation associated complications greatly affected the final therapeutical outcomes. Currently, primary disease relapse, graft-versus-host disease (GVHD) and infections remain the three leading causes of a high morbidity and mortality in allo-HSCT patients. Various strategies have been investigated in the past several decades including human γδ T cell-based therapeutical regimens. In different microenvironments, human γδ T cells assume features reminiscent of classical Th1, Th2, Th17, NKT and regulatory T cells, showing diverse biological functions. The cytotoxic γδ T cells could be utilized to target relapsed malignancies, and recently regulatory γδ T cells are defined as a novel implement for GVHD management. In addition, human γδ Τ cells facilitate control of post-transplantation infections and participate in tissue regeneration and wound healing processes. These features potentiate γδ T cells a versatile therapeutical agent to target transplantation associated complications. This review focuses on insights of applicable potentials of human γδ T cells reconciling complications associated with allo-HSCT. We believe an improved understanding of pertinent γδ T cell functions would be further exploited in the design of innovative immunotherapeutic approaches in allo-HSCT, to reduce mortality and morbidity, as well as improve quality of life for patients after transplantation.

Matched related donor hematopoietic stem cell transplantation results in a long-term follow-up of a pediatric acquired severe aplastic anemia subset: A stem cell source perspective

HSCT has substantially improved pediatric acquired SAA patients' outcomes. Retrospectively, we attempted to assess the outcome of MRD HSCT in 65 pediatric patients referred to a single center from 1992 to 2012. We were particularly interested to find out whether source of SC (PB, n = 40 and BM, n = 25) significantly impacts EFS and GVHD incidence. With a median follow-up of 45 months, total EFS was 87.7%; EFS for PB and BM groups was 87.5% and 88%, respectively. Acute GVHD (grades 3-4) occurred in 13 patients (PB, n = 10 [25%] and BM, n = 3 [12%]), acute GVHD (grades 2-4) occurred in 24 (PB, n = 16 [40%] and BM, n = 8 [32%]). Extensive chronic GVHD occurred in five patients (PB, n = 3 [7.5%] and BM, n = 2 [8%]). Cox regression revealed that elapsed time of <10 months between diagnosis and HSCT is associated with improved survival (hazard ratio, 95% CI = 1.204, 1.010-1.434, p = 0.038). SC source did not significantly affect EFS, incidence of acute GVHD (grades 3-4), or extensive chronic GVHD (p = 0.938, 0.121, and 0.487, respectively). Based on our findings, pediatric acquired SAA patients are benefitted most if MRD-HSCT is carried out early in disease process and SC source does not affect outcome of MRD-HSCT in these patients.

Timing of allogeneic stem cell transplantation for myelodysplastic syndromes and aplastic anemia

Allogeneic hematopoietic stem cell transplantation (HSCT) for myelodysplastic syndrome (MDS) is a potentially curative procedure, but is associated with a significant risk of morbidity and mortality. With the recent approval of disease-modifying agents, the appropriate timing of allogeneic HSCT needs to be addressed. Similarly, the optimal use of these disease-modifying agents before HSCT needs to be determined. In severe aplastic anemia, HSCT is a proven cure, but HLA-matched sibling donors are found in fewer than 25% of newly diagnosed patients. The use of early unrelated donor HSCT is an evolving concept that will become more accepted as improvements in HSCT outcomes continue.

Bone marrow mesenchymal stem cells from patients with aplastic anemia maintain functional and immune properties and do not contribute to the pathogenesis of the disease

Aplastic anemia is a life-threatening bone marrow failure disorder characterized by peripheral pancytopenia and marrow hypoplasia. The majority of cases of aplastic anemia remain idiopathic, although hematopoietic stem cell deficiency and impaired immune responses are hallmarks underlying the bone marrow failure in this condition. Mesenchymal stem/stromal cells constitute an essential component of the bone marrow hematopoietic microenvironment because of their immunomodulatory properties and their ability to support hematopoiesis, and they have been involved in the pathogenesis of several hematologic malignancies. We investigated whether bone marrow mesenchymal stem cells contribute, directly or indirectly, to the pathogenesis of aplastic anemia. We found that mesenchymal stem cell cultures can be established from the bone marrow of aplastic anemia patients and display the same phenotype and differentiation potential as their counterparts from normal bone marrow. Mesenchymal stem cells from aplastic anemia patients support the in vitro homeostasis and the in vivo repopulating function of CD34(+) cells, and maintain their immunosuppressive and anti-inflammatory properties. These data demonstrate that bone marrow mesenchymal stem cells from patients with aplastic anemia do not have impaired functional and immunological properties, suggesting that they do not contribute to the pathogenesis of the disease.