Allogeneic hematopoietic stem cell transplantation in thalassemia major: results of a reduced-toxicity conditioning regimen based on the use of treosulfan

Exploring the bone marrow micro environment in thalassemia patients: potential therapeutic alternatives

Genetic mutations in the β-globin gene lead to a decrease or removal of the β-globin chain, causing the build-up of unstable alpha-hemoglobin. This condition is referred to as beta-thalassemia (BT). The present treatment strategies primarily target the correction of defective erythropoiesis, with a particular emphasis on gene therapy and hematopoietic stem cell transplantation. However, the presence of inefficient erythropoiesis in BT bone marrow (BM) is likely to disturb the previously functioning BM microenvironment. This includes accumulation of various macromolecules, damage to hematopoietic function, destruction of bone cell production and damage to osteoblast(OBs), and so on. In addition, the changes of BT BM microenvironment may have a certain correlation with the occurrence of hematological malignancies. Correction of the microenvironment can be achieved through treatments such as iron chelation, antioxidants, hypoglycemia, and biologics. Hence, This review describes damage in the BT BM microenvironment and some potential remedies.

Comparison of fludarabine/melphalan (FluMel) with fludarabine/melphalan/BCNU or thiotepa (FBM/FTM) in patients with AML in first complete remission undergoing allogeneic hematopoietic stem cell transplantation - a registry study on behalf of the EBMT Acute Leukemia Working Party

Conditioning protocols for patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) are being developed continuously to improve their anti-leukemic efficacy and reduce their toxicity. In this study, we compared the conditioning protocol of fludarabine with melphalan 140 mg/m2 (FluMel) with conditioning protocols based on this same backbone but with an additional alkylating agent i.e., either fludarabine/BCNU (also known as carmustine)/melphalan (FBM), or fludarabine/thiotepa/melphalan (FTM) 110 mg/m2. We included 1272 adult patients (FluMel, n = 1002; FBM/FTM, n = 270) with acute myeloid leukemia (AML) with intermediate/poor cytogenetic risk in first complete remission (CR) from the registry of the EBMT Acute Leukemia Working Party. Despite patients in the FBM/FTM group were older (64.1 years vs. 59.8 years, p < 0.001) and had a worse Karnofsky performance score (KPS < 90, 33% vs. 24%, p = 0.003), they showed a better overall survival (OS) (2 y OS: 68.3% vs. 58.1%, p = 0.02) and less non-relapse mortality (NRM) (2 y NRM: 15.8% vs. 22.2%, p = 0.009) compared to patients treated with FluMel. No significant differences were observed in relapse incidence (RI) (2 y RI: 24.9% vs. 23.7%, p = 0.62). In conclusion, the addition of a second alkylating agent (BCNU/carmustine or thiotepa) to FluMel as FBM/FTM conditioning, improves OS in AML patients in first CR with intermediate/poor risk cytogenetics after allo-HCT.

Treosulfan vs busulfan conditioning for allogeneic bmt in children with nonmalignant disease: a randomized phase 2 trial

Optimal conditioning prior to allogeneic hematopoietic stem cell transplantation for children with non-malignant diseases is subject of ongoing research. This prospective, randomized, phase 2 trial compared safety and efficacy of busulfan with treosulfan based preparative regimens. Children with non-malignant diseases received fludarabine and either intravenous (IV) busulfan (4.8 to 3.2 mg/kg/day) or IV treosulfan (10, 12, or 14 g/m2/day). Thiotepa administration (2 × 5 mg/kg) was at the investigator's discretion. Primary endpoint was freedom from transplantation (treatment)-related mortality (freedom from TRM), defined as death between Days -7 and +100. Overall, 101 patients (busulfan 50, treosulfan 51) with at least 12 months follow-up were analyzed. Freedom from TRM was 90.0% (95% CI: 78.2%, 96.7%) after busulfan and 100.0% (95% CI: 93.0%, 100.0%) after treosulfan. Secondary outcomes (transplantation-related mortality [12.0% versus 3.9%]) and overall survival (88.0% versus 96.1%) favored treosulfan. Graft failure was more common after treosulfan (n = 11), than after busulfan (n = 2) while all patients were rescued by second procedures except one busulfan patient. CTCAE Grade III adverse events were similar in both groups. This study confirmed treosulfan to be an excellent alternative to busulfan and can be safely used for conditioning treatment in children with non-malignant disease.

Stem cell transplantation for ALL: you've always got a donor, why not always use it?

Hematopoietic stem cell transplantation (HSCT) represents a consolidated therapeutic strategy for high-risk pediatric acute lymphoblastic leukemia (ALL), offering the potential for curative treatment. This manuscript delves into the debate around the more universal application of HSCT for pediatric ALL in the modern era, considering the ubiquitous availability of suitable donors. In fact, despite significant advancements in chemotherapy, targeted therapy, and immunotherapy, a subset of pediatric patients with ALL with high-risk features or relapse continue to encounter poor prognostic outcomes. For this subgroup of patients, HSCT often remains the only potentially curative measure, leveraging the graft-versus- leukemia effect for long-term disease control. Nevertheless, the procedure's complexity and associated risks have traditionally curtailed its widespread use. However, the scenario is shifting with improvements in HLA matching, availability of alternative donor sources, less toxic conditioning regimens, and improved supportive care protocols. Concurrently, emerging therapies like CD19+ CAR T cells present new considerations for definitive therapy selection in relapsed/ refractory ALL. This article reviews critical current evidence and debates the potential of HSCT as a more universal treatment for ALL, reevaluating traditional treatment stratification in light of the constant availability of stem cell donors.

Busulfan-Based and Treosulfan-Based Myeloablative Conditioning for Allogeneic Transplantation in Children with Thalassemia Major: a Single-Center Experience From Southern Turkey

OBJECTIVES

Allogeneic hematopoietic stem cell transplant is the only curative treatment for patients with transfusion-dependent thalassemia major. In recent years, a number of novel approaches have improved patient outcomes and quality of life by minimizing the toxicity of conditioning regimens. The objective of this study was to compare the role of treosulfan- and busulfan-based conditioning in transfusion-dependent thalassemia.

MATERIALS AND METHODS

Data were collected retrospectively on 121 children with beta thalassemia major who underwent hematopoietic stem cell transplant using treosulfan-based (n = 37) or busulfan-based (n = 84) conditioning regimens between 2012 and 2022.

RESULTS

Two-year overall survival was 87.5% in the busulfan-based conditioning group and 91.1% in the treosulfan-based conditioning group.The group given the busulfan regimen compared with treosulfan regimen had significantly increased number of side effects (58.3% vs 21.6%, respectively; P < .001). When the busulfan-based regimen by level was evaluated, we observed no significant differences between the frequency of side effects according to drug serum levels. In addition, no significant differences were shown between the 2 regimen groups for cumulative incidence of acute and chronic graft-versus-host disease.

CONCLUSIONS

The safety and effectiveness of a treosulfan-based myeloablative conditioning regimen has been confirmed by ourretrospective investigation of pediatric patients with beta thalassemia.

Treosulfan Versus Busulfan-based Conditioning in Pediatric Patients Undergoing Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-analysis

It is unclear whether there is a difference in outcomes with treosulfan or busulfan-based conditioning in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT). We reviewed the evidence on this topic through a systematic review and meta-analysis, the comparison between treosulfan and busulfan-based conditioning in pediatric patients undergoing HSCT for instance. Six studies were included. Meta-analysis showed that there was no difference in the incidence of acute graft versus host disease (odds ratio [OR]: 0.96; 95% CI: 0.57, 1.61), grade II to IV acute graft versus host disease (OR: 1.19; 95% CI: 0.83, 1.72), chronic GVHD (OR: 1.18; 95% CI: 0.70, 2.00), and veno-occlusive disease (OR: 0.92; 95% CI: 0.22, 3.85) between treosulfan and busulfan groups. Pooled analysis indicated marginally better survival with treosulfan-based conditioning (OR: 1.57; 95% CI: 1.00, 2.44), however, these results were unstable on sensitivity analysis. A meta-analysis found no difference in transplant-related mortality (OR: 0.70; 95% CI: 0.34, 1.42) between the two groups. Retrospective data from a heterogenous population indicates that there is no difference in the rate of GVHD after treosulfan versus busulfan-based conditioning for pediatric HSCT. A marginal improvement in survival was noted with treosulfan but the results remained unstable. Future randomized controlled trials are needed to provide better evidence.

Is Old (Fludrabine/Busulfan/Cyclophosphamide/rAntiThymocyteGlobulin) Conditioning Still Gold for Allogeneic Transplants in Transfusion Dependent Beta-Thalassemia of All Risk Categories in 21st Century?

Allogeneic stem cell transplant (allo-SCT) is the only curative option for transfusion dependent thalassemia (TDT) until the gene therapy could bring paradigm shift. We analysed TDT allo-SCTs performed with Flu/Bu/Cy/rATG conditioning between October 2018 and April 2022 at our center. A retrospective analysis of 55 consecutive HLA matched alloSCT for TDT and was approved by hospital's Institutional Review Board. Median age was 7(2-13) years. On presentation, number of patients with Class I, II, III were 18 (32.7%), 14(25.4%) and 23(41.8%) respectively {ClassIIIA = 14(25.4%),ClassIIIB = 9(16.3%)}. After downstaging, Class I, II, III were 22(40%), 15(27.2%) and 18(32.7%) patients respectively {ClassIIIA = 15(27.2%),ClassIIIB = 3(5.4%)}. Graft was bone marrow in 53(96.4%) and peripheral blood stem cell in 2(3.6%) patients. Mean CD34 stem cell dose was 3.28(1.2-6.5) × 106/kg. Neutrophils and platelets engrafted at a median of 16(12-32) and 17(12-48) days. Median duration of follow-up was 20.7(1.8-43.9) months. There was no primary rejection. Although, mixed chimerism was common {17(30.9%)}, there was only one secondary rejection (1.8%). Venoocclusive disease was seen 12(21.8%) patients {mild = 9(75%), moderate = 2(16.6%) and severe = 1(8.3%)}. Acute and Chronic graft versus host disease was observed in 4(7.2%) and 4(7.2%) patients respectively. There was no treatment related mortality. Overall survival and Thalassemia Free Survival were 100% ± 0% and 98% ± 2% respectively. Flu/Bu/Cy/rATG conditioning with BM graft is a safe and effective regimen even in higher risk. It also highlights the importance of pretransplant downstaging of risk class in improving the outcomes.

Hematopoietic Stem Cell Transplantation in Thalassemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only consolidated, potentially curative treatment for patients with transfusion-dependent thalassemia major. In the past few decades, several new approaches have reduced the toxicity of conditioning regimens and decreased the incidence of graft-versus-host disease, improving patients' outcomes and quality of life. In addition, the progressive availability of alternative stem cell sources from unrelated or haploidentical donors or umbilical cord blood has made HSCT a feasible option for an increasing number of subjects lacking an human leukocyte antigen (HLA)-identical sibling. This review provides an overview of allogeneic hematopoietic stem cell transplantation in thalassemia, reassesses current clinical results, and discusses future perspectives.

Haploidentical transplant for paediatric patients with severe thalassaemia using post-transplant cyclophosphamide and methotrexate: A prospectively registered multicentre trial from the Bone Marrow Failure Working Group of Hunan Province, China

Haploidentical transplantation strategies for patients with transfusion-dependent thalassaemia (TD-TM) remain to be investigated. In this study, 54 paediatric patients with TD-TM were treated with a novel approach using post-transplant cyclophosphamide (PTCy) and low-dose methotrexate (LD-MTX), following a myeloablative regimen. The incidence of neutrophil and platelet engraftment was 96.3% ± 2.6% and 94.4% ± 3.1% respectively. The cumulative incidence of grades II-III acute graft-versus-host disease (GVHD) was 13.8% ± 4.8% at 100 days. At three years, the cumulative incidence of chronic GVHD was 28.5% ± 8.5%. With a median follow-up of 520 days (132-1325 days), the overall survival (OS) and event-free survival (EFS) were 98.1% ± 1.8% and 90.7% ± 3.9% respectively. Compared with the low-dose cyclophosphamide (CTX) conditioning regimen (120 mg/kg), the high-CTX regimen (200 mg/kg) achieved a higher incidence of stable engraftment (100% vs 66.7% ± 15.7%, p = 0.003), a comparable incidence of grades II-III acute GVHD, a lower incidence of chronic GVHD (20.2% ± 8.3% vs 66.6% ± 19.2%, p = 0.011), and better overall survival (100% vs 88.9% ± 10.5%, p = 0.025) as well as EFS (95.6% ± 3.1% vs 66.7% ± 15.7%, p = 0.008). Our results using unmanipulated haploidentical grafts and PTCy with LD-MTX in TD-TM are encouraging. (chictr.org.cn ChiCTR1800017969).

Busulfan (Bu) and Cyclophosphamide (Cy) based conditioning regimen still holds the promise of being a safe and efficacious regimen for Allogeneic Transplantation in patients with Transfusion Dependent Thalassemia (TDT), even in high risk

BuCy based regimen has been used as a standard myeloablative chemotherapy for haematopoietic stem cell transplantation in thalassemia. However, treosulfan based conditioning regimen has emerged due to concerns of toxicities. We retrospectively analysed the safety and efficacy of Fludrabine/Bu/Cy/ATG vs Treosulfan/Thiotepa/Fludrabine regimens for HSCT in TDT conducted at our institute (2013-2021). In 75 patients, 36 (48%) received Flu/Bu/Cy/ATG whereas 39(52%) received Treo/Thio/Flu. Median age was 6(1-12) and 9 (1-15) years respectively. Number of patients with Class I, II, III were 14, 10, 12 in Flu/Bu/Cy/ATG vs 2, 19, 18 in Treo/Thio/Flu group respectively. Graft was growth factor mobilized bone marrow in Flu/Bu/Cy/ATG vs peripheral blood stem cell in Treo/Thio/Flu group. Mean stem cell dose was 3.82(2.2-9.1) vs 5(1.65-8.01) 10⁶ /kg in Flu/Bu/Cy/ATG vs Treo/ Thio/ Flu group respectively. Neutrophils and platelets engrafted at a median of 16(14-21) and 16 (9-47) days in Flu/Bu/Cy/ATG and 15(10-20) and 13(9-41) days in Treo/ Thio/ Flu group. Median duration of follow-up was 28 (23-32.9) months. Five (6.6%) patients had rejection (all secondary). Venoocclusive disease was observed in 02 (5.7%) vs 04 (10.3%) patients (p=0.047) respectively. Flu/Bu/Cy/ATG had 04(11.4%) patients with acute GVHD vs 15(38.5%) patients which had significant impact on survival (p=0.038). We observed chronic GVHD in 04(11.4%) and 11(28.2%) patients respectively with significant impact on survival (p=0.031). Four (5.1%) patients had TRM in Treo/Thio/ Flu group, in contrast to none in Flu/Bu/Cy/ATG group. Mixed chimerism was common in Flu/Bu/Cy/ATG {20 (57.1%)} vs Treo/Thio/Flu group {12(30.1%)}. 5-year EFS and OS of entire cohort were 87%+4% and 94%+3% respectively. Estimated TFS, EFS, OS of Flu/Bu/Cy/ATG vs Treo/Thio/Flu was 97.1%+2.9% vs 89.2%+5.1%(p=0.251), 97+3% vs 80.7+6% (p=0.041) and 100% vs 90.4+5 % (p=0.067) respectively. In our experience Flu/Bu/Cy/ATG regimen is safe and effective even in high risk TDT. However, one needs to be vigilant for mixed chimerism.

Emerging approaches to improve allogeneic hematopoietic cell transplantation outcomes for nonmalignant diseases

Many congenital or acquired nonmalignant diseases (NMDs) of the hematopoietic system can be potentially cured by allogeneic hematopoietic cell transplantation (HCT) with varying types of donor grafts, degrees of HLA matching, and intensity of conditioning regimens. Unique features that distinguish the use of allogeneic HCT in this population include higher rates of graft failure, immune-mediated cytopenias, and the potential to achieve long-term disease-free survival in a mixed chimerism state. Additionally, in contrast to patients with hematologic malignancies, a priority is to completely avoid graft-versus-host disease in patients with NMD because there is no theoretical beneficial graft-versus-leukemia effect that can accompany graft-versus-host responses. In this review, we discuss the current approach to each of these clinical issues and how emerging novel therapeutics hold promise to advance transplant care for patients with NMDs.

Conditioning Regimens in Patients with β-Thalassemia Who Underwent Hematopoietic Stem Cell Transplantation: A Scoping Review

The success of transplant procedures in patients with beta-thalassemia major (β-thalassemia) goes hand-in-hand with improvements in disease knowledge, better supportive care, discoveries in immunogenetics, increase in stem cell sources, and enhancement of conditioning regimens. The aim of this scoping review was to report the evolution of conditioning regimes for β-thalassemia hematopoietic stem cell transplantation. We performed a systematic search for all relevant articles published before July 2021, using the following Medical Subject Headings: "bone marrow transplantation", "stem cell transplantation", "allogeneic", "thalassemia", "β-thalassemia", and "thalassemia major". The final analysis included 52 studies, published between 1988 and 2021, out of 3877 records. The most common conditioning regimen was a combination of busulfan and cyclophosphamide, with successive dose adjustments or remodulation based on patient characteristics. Pre-transplant treatments, reductions in cyclophosphamide dosage, or the adoption of novel agents such as treosulphan all improved overall survival and thalassemia-free survival in transplant-related mortality high-risk patients. Conditioning regimes were modulated for those without a suitable fully matched sibling or unrelated donor, with encouraging results. Hematopoietic stem cell transplantation with haploidentical donors is currently available to virtually all patients with β-thalassemia. However, disparities in outcome are still present around the world. In developing and limited-resource countries, where most diagnoses are focused, transplants are not always available. Therefore, more efforts are needed to close this treatment gap.

Curative therapy for hemoglobinopathies: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee review comparing outcomes, accessibility and cost of ex vivo stem cell gene therapy versus allogeneic hematopoietic stem cell transplantation

Thalassemia and sickle cell disease (SCD) are the most common monogenic diseases in the world and represent a growing global health burden. Management is limited by a paucity of disease-modifying therapies; however, allogeneic hematopoietic stem cell transplantation (HSCT) and autologous HSCT after genetic modification offer patients a curative option. Allogeneic HSCT is limited by donor selection, morbidity and mortality from transplant conditioning, graft-versus-host disease and graft rejection, whereas significant concerns regarding long-term safety, efficacy and cost limit the broad applicability of gene therapy. Here the authors review current outcomes in allogeneic and autologous HSCT for transfusion-dependent thalassemia and SCD and provide our perspective on issues surrounding accessibility and costs as barriers to offering curative therapy to patients with hereditary hemoglobinopathies.

HSCT remains the only cure for patients with transfusion-dependent thalassemia until gene therapy strategies are proven to be safe

Patients with β-thalassemia suffer from severe anemia, iron overload and multiple complications, that affect their quality of life and well-being. Allogeneic hematopoietic stem cell transplantation (HSCT) from an HLA-matched sibling donor, performed in childhood, has been the gold standard for thalassemic patients for decades. Unfortunately, siblings are available only for the minority of patients. Fully matched unrelated donors have been the second choice for cure, with equal results as far as overall survival is concerned, having though the cost of frequent and serious complications. On the other hand, haploidentical transplantation is performed more frequently during the last decade, with promising results. Gene therapy represents a novel therapeutic approach, with impressive results from clinical trials, both from gene addition strategies, as well as from the emerging gene editing tools. After reviewing current critical points of HSCT using alternative donors and assessing recently reported safety issues of gene therapy methods, we conclude that, although a breakthrough, the safety of gene therapy remains to be established.

Current status of beta-thalassemia and its treatment strategies

Background

Thalassemia is an inherited hematological disorder categorized by a decrease or absence of one or more of the globin chains synthesis. Beta‐thalassemia is caused by one or more mutations in the beta‐globin gene. The absence or reduced amount of beta‐globin chains causes ineffective erythropoiesis which leads to anemia.

Methods

Beta‐thalassemia has been further divided into three main forms: thalassemia major, intermedia, and minor/silent carrier. A more severe form among these is thalassemia major in which individuals depend upon blood transfusion for survival. The high level of iron deposition occurs due to regular blood transfusion therapy.

Results

Overloaded iron raises the synthesis of reactive oxygen species (ROS) that are noxious and prompting the injury to the hepatic, endocrine, and vascular system. Thalassemia can be analyzed and diagnosed via prenatal testing (genetic testing of amniotic fluid), blood smear, complete blood count, and DNA analysis (genetic testing). Treatment of thalassemia intermediate is symptomatic; however; it can also be accomplished by folic supplementation and splenectomy.

Conclusion

Thalassemia major can be cured through regular transfusion of blood, transplantation of bone marrow, iron chelation management, hematopoietic stem cell transplantation, stimulation of fetal hemoglobin production, and gene therapy.

Impact of Treosulfan Exposure on Early and Long-Term Clinical Outcomes in Pediatric Allogeneic Hematopoietic Stem Cell Transplantation Recipients: A Prospective Multicenter Study

Treosulfan-based conditioning has gained popularity in pediatric allogeneic hematopoietic stem cell transplantation (HSCT) because of its presumed favorable efficacy and toxicity profile. Treosulfan is used in standardized dosing regimens based on body surface area. The relationships between systemic treosulfan exposure and early and long-term clinical outcomes in pediatric patients undergoing allogeneic HSCT for nonmalignant diseases remain unclear. In this a multicenter, prospective observational study, we assessed the association between treosulfan exposure and early and, in particular, long-term clinical outcomes. Our study cohort comprised 110 pediatric patients with nonmalignant diseases who underwent HSCT between 2011 and 2019 in Leiden, The Netherlands and Rome, Italy. Blood samples were collected, and treosulfan area under the receiver operating characteristic curve (AUC_0-∞) was estimated as a measure of exposure. Cox proportional hazard survival analyses were performed to assess the relationships between treosulfan exposure and overall survival (OS) and event-free survival (EFS). The predictive value of systemic treosulfan exposure for the occurrence of toxicity within 28 days was evaluated using a multivariable logistic regression analysis. In the overall cohort, OS and EFS at 2 years were 89.0% and 75.3%, respectively, with an excellent OS of 97% in children age <2 years. The occurrence of grade II-IV acute graft-versus-host disease, the level of 1-year whole blood chimerism, and 2-year OS and EFS were not correlated with treosulfan exposure. The occurrence of skin toxicity (odds ratio [OR], 3.97; 95% confidence interval [CI], 1.26-13.68; P = .02) and all-grade mucositis (OR, 4.43; 95% CI, 1.43-15.50; P = .02), but not grade ≥2 mucositis (OR, 1.51; 95% CI, 0.52 to 4.58; P = .46) was related to high treosulfan exposure (>1750 mg*h/L). Our study demonstrates that standardized treosulfan-based conditioning results in a favorable OS and EFS in infants and children with nonmalignant diseases, independent of interindividual variation in treosulfan exposure. These outcomes can be achieved without the need for therapeutic drug monitoring, thereby emphasizing the advantage of treosulfan use in this category of patients. Although higher treosulfan exposure increases the risk of skin toxicity, there is no absolute necessity for therapeutic drug monitoring if proper preventive skin measures are taken. More research is needed to assess whether deescalation of treosulfan doses is possible to minimize early and long-term toxicity without compromising efficacy.

Treosulfan-induced myalgia in pediatric hematopoietic stem cell transplantation identified by an electronic health record text mining tool

Treosulfan is increasingly used as myeloablative agent in conditioning regimen prior to allogeneic hematopoietic stem cell transplantation (HSCT). In our pediatric HSCT program, myalgia was regularly observed after treosulfan-based conditioning, which is a relatively unknown side effect. Using a natural language processing and text-mining tool (CDC), we investigated whether treosulfan compared with busulfan was associated with an increased risk of myalgia. Furthermore, among treosulfan users, we studied the characteristics of given treatment of myalgia, and studied prognostic factors for developing myalgia during treosulfan use. Electronic Health Records (EHRs) until 28 days after HSCT were screened using the CDC for myalgia and 22 synonyms. Time to myalgia, location of pain, duration, severity and drug treatment were collected. Pain severity was classified according to the WHO pain relief ladder. Logistic regression was performed to assess prognostic factors. 114 patients received treosulfan and 92 busulfan. Myalgia was reported in 37 patients; 34 patients in the treosulfan group and 3 patients in the busulfan group (p = 0.01). In the treosulfan group, median time to myalgia was 7 days (0–12) and median duration of pain was 19 days (4–73). 44% of patients needed strong acting opiates and adjuvant medicines (e.g. ketamine). Hemoglobinopathy was a significant risk factor, as compared to other underlying diseases (OR 7.16 95% CI 2.09–30.03, p = 0.003). Myalgia appears to be a common adverse effect of treosulfan in pediatric HSCT, especially in hemoglobinopathy. Using the CDC, EHRs were easily screened to detect this previously unknown side effect, proving the effectiveness of the tool. Recognition of treosulfan-induced myalgia is important for adequate pain management strategies and thereby for improving the quality of hospital stay.

Recommendations on hematopoietic stem cell transplantation for patients with Diamond-Blackfan anemia. On behalf of the Pediatric Diseases and Severe Aplastic Anemia Working Parties of the EBMT

Diamond Blackfan anemia (DBA) is a rare congenital syndrome presenting primarily as pure red cell aplasia with constitutional abnormalities and cancer predisposition. Established treatment options are corticosteroids, regular erythrocyte transfusions with iron chelation therapy, and hematopoietic stem cell transplantation (HSCT). To date, HSCT is the only definitive curative treatment for the hematological phenotype of DBA, but there is little experience with its use. Given the rarity of the disease and its unique features, an expert panel agreed to draw up a set of recommendations on the use of HSCT in DBA to guide clinical decision-making and practice. The recommendations address indications, pretransplant patient evaluation, donor selection, stem cell sources, conditioning regimens, prophylaxis of rejection and graft versus host disease, and post-transplant follow-up.

Graft-versus-host Disease Prophylaxis With Abatacept Reduces Severe Acute Graft-versus-host Disease in Allogeneic Hematopoietic Stem Cell Transplant for Beta-thalassemia Major With Busulfan, Fludarabine, and Thiotepa

BACKGROUND

We hypothesized that the addition of 4 doses of abatacept to our standard acute graft-versus-host disease (GVHD) prophylaxis would reduce the incidence of day +100 severe acute GVHD in children with transfusion-dependent beta-thalassemia major undergoing a myeloablative allogeneic hematopoietic stem cell transplant (HSCT), without impacting engraftment.

METHODS

Twenty-four children with beta-thalassemia major received abatacept at a dose of 10 mg/kg intravenously on days -1, +5, +14, and +28 after HSCT in addition to calcineurin inhibitors and methylprednisolone. Outcomes were compared to 8 beta-thalassemia patients who received standard acute GVHD prophylaxis.

RESULTS

There was no difference in engraftment between the 2 groups. No patient had grades III-IV acute GVHD by day +100 in the abatacept cohort compared with 50% in the standard acute GVHD prophylaxis group (P = 0.001). Viral reactivation occurred in 5 children in the standard acute GVHD cohort and in 20 children in the abatacept cohort (P = 0.2). Thalassemia-free survival after HSCT was 100% in the abatacept cohort compared to 62.5% in the standard cohort at last follow-up (P = 0.007).

CONCLUSIONS

Adding abatacept to our routine GVHD prophylaxis reduced the incidence of day +100 severe acute GVHD without impacting engraftment or survival.

Treosulfan-based conditioning for inborn errors of immunity

Inborn errors of immunity (IEI) are inherited disorders that lead to defects in the development and/or function of the immune system. The number of disorders that can be treated by haematopoietic stem-cell transplantation (HSCT) has increased rapidly with the advent of next-generation sequencing. The methods used to transplant children with IEI have improved dramatically over the last 20 years. The introduction of reduced-toxicity conditioning is an important factor in the improved outcome of HSCT. Treosulfan has myeloablative and immunosuppressive properties, enabling engraftment with less toxicity than traditionally used doses of busulfan. It is firmly incorporated into the conditioning guidelines of the Inborn Errors Working Party of the European Society for Blood and Marrow Transplantation. Unlike busulfan, pharmacokinetically guided dosing of treosulfan is not part of routine practice, but data are emerging which indicate that further improvements in outcome may be possible, particularly in infants who have a decreased clearance of treosulfan. It is likely that individualized dosing, not just of treosulfan, but of all agents used in conditioning regimens, will be developed and implemented in the future. This will lead to a reduction in unwanted variability in drug exposure, leading to more predictable and adjustable exposure, and improved outcome of HSCT, with fewer late adverse effects and improved quality of life. Such conditioning regimens can be used as the basis to study the need for additional agents in certain disorders which are difficult to engraft or require high levels of donor chimerism, the dosing of individual cellular components within grafts, and effects of adjuvant cellular or immunotherapy post-transplant. This review documents the establishment of treosulfan worldwide, as a safe and effective agent for conditioning children with IEI prior to HSCT.

Favorable outcomes of hematopoietic stem cell transplantation in children and adolescents with Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) is a congenital pure red cell aplasia associated with congenital abnormalities and cancer predisposition. Allogeneic hematopoietic stem cell transplantation (HSCT) can correct the hematological phenotype and is indicated in transfusion-dependent patients. In 70 children reported to the German DBA and French HSCT registries, HSCT was performed from 1985 to 2017. Median age at HSCT was 5.5 years (range, 0.9-17.3 years). Two-thirds of patients (64%) were transplanted from a matched sibling donor (MSD), and most procedures were performed after the year 1999 (73%). Primary engraftment was achieved in all patients. One patient developed secondary graft failure. Cumulative incidence of acute graft-versus-host disease (GVHD) was 24% for °II-IV (95% confidence interval [CI], 16% to 37%) and 7% for °III-IV (95% CI, 3% to 17%); cumulative incidence of chronic GVHD was 11% (95% CI, 5% to 22%). The probability of chronic GVHD-free survival (cGFS) was 87% (95% CI, 79% to 95%) and significantly improved over time (<2000: 68% [95% CI, 47% to 89%] vs ≥2000: 94% [95% CI, 87% to 100%], P < .01). cGFS was comparable following HSCT from a MSD and an unrelated donor (UD). Of note, no severe chronic GVHD or deaths were reported following MSD-HSCT after 1999. The difference of cGFS in children transplanted <10 years of age compared with older patients did not reach statistical significance (<10 years: 90% [95% CI, 81% to 99%] vs 10-18 years 78% [95% CI, 58% to 98%]). In summary, these data indicate that HSCT is efficient and safe in young DBA patients and should be considered if a MSD or matched UD is available. HSCT for transfusion dependency only must be critically discussed in older patients.

Pretransplant myeloid and immune suppression, reduced toxicity conditioning with posttransplant cyclophosphamide: Initial outcomes of novel approach for matched unrelated donor hematopoietic stem cell transplant for hemoglobinopathies

Hematopoietic stem cell transplant (HSCT) is currently the only curative option for thalassemia major (TM) and sickle cell disease (SCD). We report our experience of using pretransplant immune suppression (PTIS), augmented Johns Hopkins conditioning, and posttransplant cyclophosphamide (PTCy) as graft-versus-host disease (GvHD) prophylaxis for matched unrelated donor (MUD) transplant in TM/SCD. At a median follow-up of 307.5 days (range 251-395), all patients (three TM, one SCD) are alive and disease free. MUD HSCT with PTIS, augmented Johns Hopkins conditioning, and PTCy as GvHD prophylaxis is a promising way of treating patients with hemoglobinopathies with low regimen-related toxicity (RRT), no risk of graft failure (GF) and minimal GvHD rates.

Co-Transplantation of Haploidentical Stem Cells and a Dose of Unrelated Cord Blood in Pediatric Patients with Thalassemia Major

Allogeneic stem cell transplantation is a cure for patients suffering from thalassemia major (TM). Historically, patients were limited by the selection of donors, while the advancement of haploidentical stem cell transplantation (haplo-SCT) has greatly expanded the donor pool. However, the outcomes of haplo-SCT in TM recipients vary between different programs. In this study, we retrospectively studied 73 pediatric TM patients (median age, 7 years; range, 3 to 14 years) who underwent haplo-cord transplantation. Both the estimated overall survival and transfusion-free survival were 95.26% (CI 95.77% to 96.23%). Neither primary nor secondary graft failures were observed. The median follow-up period was 811 days (range, 370 to 1433 days). Median neutrophil and platelet engraftment times were 22 days (range, 8 to 48 days) and 20 days (range, 8 to 99 days), respectively. Acute graft-versus-host disease (aGVHD) was observed in 52% of patients and of these, 25% developed grade III to IV aGVHD. Cord blood engraftment was associated with delayed immune recovery and increased aGVHD severity. Viral DNAemia occurred in a relatively high proportion of patients but only 7% of patients developed CMV disease, while another 7% of patients had post-transplantation lymphoproliferative disorder. Long-term complication outcomes were good. Only one patient developed extensive chronic GVHD. No surviving patients were reliant on blood transfusion by the time this manuscript was submitted. This is one of the largest studies on the outcomes of pediatric TM patients who received stem cell transplantations from alternative donors. The haplo-cord program is safe and practical for TM patients that do not have matched donors.

Comparison of Hematopoietic Stem Cell Transplantation Results in Patients with β-Thalassemia Major from Three Different Graft Types

Allogeneic hematopoietic stem cell transplantation (HSCT) is the curative therapy for β-thalassemias that induces severe life-threatening complications. The human leukocyte antigen (HLA) registries and umbilical cord blood banks have carried out diligent searches to find matched unrelated donors (MUDs) for about 70.0% of patients from 2000 onwards. The chance of finding a non-sibling fully matched family donors is higher in some ethnic groups in which consanguineous marriages are common. We have studied and compared transplant complications and outcomes in different graft types (sibling, non-sibling family and unrelated). The non-sibling matched family donor (MFD) group consisted of four mothers, three fathers, five cousins, one paternal uncle and one paternal aunt. There was no significant difference in the mean transfused CD34+ cells, engraftment, median days of neutrophil and platelet recovery were achieved (p > 0.05). The distribution of postttransplant complication did not show any significant difference between groups (p > 0.05). In univariate analysis and multivarite analyses, age, gender, Pesaro risk group (I-II vs. III) and ABO incompatibilty demonstrated a significant difference in disease free survival (p < 0.05). Furthermore, in the second step of investigating overall survival (OS), age, gender and Pesaro risk group (I-II vs. III) showed a significant difference (p < 0.05). There was no significant difference in transplant-related mortality (TRM) between groups. Non-sibling related donor transplants are important for populations where consanguineous marriages are common. Transplant groups according to graft type had similar thalassemia-free survival (TFS) and OS when using a treosulfan-based regimen in our study.

Considerations in Preparative Regimen Selection to Minimize Rejection in Pediatric Hematopoietic Transplantation in Non-Malignant Diseases

The variables that influence the selection of a preparative regimen for a pediatric hematopoietic stem cell transplant procedure encompasses many issues. When one considers this procedure for non-malignant diseases, components in a preparative regimen that were historically developed to reduce malignant tumor burden may be unnecessary. The primary goal of the procedure in this instance becomes engraftment with the establishment of normal hematopoiesis and a normal immune system. Overcoming rejection becomes the primary priority, but pursuit of this goal cannot neglect organ toxicity, or post-transplant morbidity such as graft-versus-host disease or life threatening infections. With the improvements in supportive care, newborn screening techniques for early disease detection, and the expansion of viable donor sources, we have reached a stage where hematopoietic stem cell transplantation can be considered for virtually any patient with a hematopoietic based disease. Advancing preparative regiments that minimize rejection and transplant related toxicity will thus dictate to what extent this medical technology is fully utilized. This mini-review will provide an overview of the origins of conditioning regimens for transplantation and how agents and techniques have evolved to make hematopoietic stem cell transplantation a viable option for children with non-malignant diseases of the hematopoietic system. We will summarize the current state of this facet of the transplant procedure and describe the considerations that come into play in selecting a particular preparative regimen. Decisions within this realm must tailor the treatment to the primary disease condition to ideally achieve an optimal outcome. Finally, we will project forward where advances are needed to overcome the persistent engraftment obstacles that currently limit the utilization of transplantation for haematopoietically based diseases in children.

Hematopoietic Stem Cell Transplantation for Autoimmune Disease

The introduction of targeted biologic therapies has changed the treatment landscape for autoimmune diseases (ADs) substantially, but although these therapies provide more specificity, they require continuous administration, rarely restore organ function or reverse disability, and are not curative. Over the last 25 years, hematopoietic stem cell transplantation (HSCT) has been increasingly used to treat patients in whom the risk:benefit ratio of HSCT is acceptable. In contrast to chronic suppression of immune function, this intensive one-off procedure aims to provide treatment-free remissions by the reinduction of self-tolerance. The European Society for Blood and Marrow Transplantation (EBMT) Autoimmune Diseases Working Party (ADWP) has been central to development of this approach, with over 3,300 HSCT registrations for ADs. Recent data have improved the evidence base to support autologous HSCT in multiple sclerosis, systemic sclerosis, and Crohn's disease, along with a wide range of rarer disease indications, and autologous HSCT has become an integral part of treatment algorithms in various ADs.

Related and unrelated donor transplantation for β-thalassemia major: results of an international survey

We studied 1110 patients with β-thalassemia major aged ≤25 years who received transplants with grafts from HLA-matched related (n = 677; 61%), HLA-mismatched related (n = 78; 7%), HLA-matched unrelated (n = 252; 23%), and HLA-mismatched unrelated (n = 103; 9%) donors between 2000 and 2016. Ninety percent of transplants were performed in the last decade. Eight-five percent of patients received ≥20 transfusions and 88% were inadequately chelated. All patients received myeloablative-conditioning regimen. Overall and event-free survival were highest for patients aged ≤6 years and after HLA-matched related and HLA-matched unrelated donor transplantation. The 5-year probabilities of overall survival for patients aged ≤6 years, 7 to 15 years, and 16 to 25 years, adjusted for donor type and conditioning regimen were 90%, 84%, and 63%, respectively (P < .001). The corresponding probabilities for event-free survival were 86%, 80%, and 63% (P < .001). Overall and event-free survival did not differ between HLA-matched related and HLA-matched unrelated donor transplantation (89% vs 87% and 86% vs 82%, respectively). Corresponding probabilities after mismatched related and mismatched unrelated donor transplantation were 73% vs 83% and 70% vs 78%. In conclusion, if transplantation is considered as a treatment option it should be offered early (age ≤6 years). An HLA-matched unrelated donor is a suitable alternative if an HLA-matched relative is not available.

Acute toxicity and outcome among pediatric allogeneic hematopoietic transplant patients conditioned with treosulfan-based regimens

Treosulfan-based regimens constitute a feasible and increasingly used, but still myeloablative, conditioning in pediatric allogeneic hematopoietic stem cell transplantation (HSCT). We retrospectively analyzed the acute toxicity and outcome of all consecutive (2004-2015) pediatric HSCT patients prepared for HSCT with treosulfan in a single-center setting. We included HSCTs performed for both nonmalignant (n = 23) and malignant diseases (n = 11). The controls were patients with nonmalignant diseases or hematological malignancies conditioned with cyclophosphamide (Cy)-total body irradiation (TBI)-based (39 patients) or busulfan-based regimens (11 patients). The major toxicities of the treosulfan-based regimens were limited to oral mucosa and skin. 50% of the patients needed IV morphine for severe mucositis compared to 31% in patients conditioned with Cy-TBI (P = 0.02). Other toxicities were rare. The disease-free survival (DFS) of patients transplanted for nonmalignant disorders was 88.9 ± 7.5% at 2 years. The event-free survival (EFS) at 2 years in this small cohort for those with a malignant disease and a treosulfan-based conditioning was 54.5 ± 1.5%. We conclude that a treosulfan-based conditioning regimen gives excellent DFS in pediatric HSCT performed for a nonmalignant disorder but with substantial mucosal toxicity. In a malignant disorder a treosulfan-based regimen looks promising but larger, preferably randomized, studies are needed to prove efficacy.

Subsequent neoplasms and late mortality in children undergoing allogeneic transplantation for nonmalignant diseases

We examined the risk of subsequent neoplasms (SNs) and late mortality in children and adolescents undergoing allogeneic hematopoietic cell transplantation (HCT) for nonmalignant diseases (NMDs). We included 6028 patients (median age, 6 years; interquartile range, 1-11; range, <1 to 20) from the Center for International Blood and Marrow Transplant Research (1995-2012) registry. Standardized mortality ratios (SMRs) in 2-year survivors and standardized incidence ratios (SIRs) were calculated to compare mortality and SN rates with expected rates in the general population. Median follow-up of survivors was 7.8 years. Diagnoses included severe aplastic anemia (SAA; 24%), Fanconi anemia (FA; 10%), other marrow failure (6%), hemoglobinopathy (15%), immunodeficiency (23%), and metabolic/leukodystrophy syndrome (22%). Ten-year survival was 93% (95% confidence interval [95% CI], 92% to 94%; SMR, 4.2; 95% CI, 3.7-4.8). Seventy-one patients developed SNs (1.2%). Incidence was highest in FA (5.5%), SAA (1.1%), and other marrow failure syndromes (1.7%); for other NMDs, incidence was <1%. Hematologic (27%), oropharyngeal (25%), and skin cancers (13%) were most common. Leukemia risk was highest in the first 5 years posttransplantation; oropharyngeal, skin, liver, and thyroid tumors primarily occurred after 5 years. Despite a low number of SNs, patients had an 11-fold increased SN risk (SIR, 11; 95% CI, 8.9-13.9) compared with the general population. We report excellent long-term survival and low SN incidence in an international cohort of children undergoing HCT for NMDs. The risk of SN development was highest in patients with FA and marrow failure syndromes, highlighting the need for long-term posttransplantation surveillance in this population.

Treosulfan-fludarabine-thiotepa-based conditioning treatment before allogeneic hematopoietic stem cell transplantation for pediatric patients with hematological malignancies

Treosulfan-based conditioning prior to allogeneic transplantation has been shown to have myeloablative, immunosuppressive, and antineoplastic effects associated with reduced non-relapse mortality (NRM) in adults. Therefore, we prospectively evaluated the safety and efficacy of treosulfan-based conditioning in children with hematological malignancies in this phase II trial. Overall, 65 children with acute lymphoblastic leukemia (35.4%), acute myeloid leukemia (44.6%), myelodysplastic syndrome (15.4%), or juvenile myelomonocytic leukemia (4.6%) received treosulfan intravenously at a dose of 10 mg/m²/day (7.7%), 12 g/m²/day (35.4%), or 14 g/m²/day (56.9%) according to their individual body surface area in combination with fludarabine and thiotepa. The incidence of complete donor chimerism at day +28 was 98.4% with no primary and only one secondary graft failure. At 36 months, NRM was only 3.1%, while relapse incidence was 21.7%, and overall survival was 83.0%. The cumulative incidence of acute graft-vs.-host disease was 45.3% for grades I–IV and 26.6% for grades II–IV. At 36 months, 25.8% overall and 19.4% moderate/severe chronic graft-vs.-host disease were reported. These data confirm the safe and effective use of treosulfan-based conditioning in pediatric patients with hematological malignancies. Therefore, treosulfan/fludarabine/thiotepa can be recommended for myeloablative conditioning in children with hematological malignancies.

Hematopoietic Stem Cell Transplantation for Severe Thalassemia Patients from Haploidentical Donors Using a Novel Conditioning Regimen

Patients with severe thalassemia commonly have a survival that is significantly shorter than that of the general population. Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the only established treatment that is potentially curative, but it is limited by the availability of donors and the medical condition of the patient. To expand the donor pool to include haploidentical related donors, we introduced a program consisting of a pharmacologic pretransplant immune suppression phase (PTIS) and 2 courses of dexamethasone and fludarabine, followed by pretransplant conditioning with fludarabine-i.v. busulfan and post-transplant graft-versus-host disease (GVHD) prophylaxis with cyclophosphamide, tacrolimus, and mycophenolate mofetil. We transplanted 83 consecutive transfusion-dependent patients with thalassemia (median age, 12 years; range, 1 to 28 years) with a minimum follow-up of 6 months (median, 15 months; range, 7 to 53 months); the 3-year projected overall and event-free survival is over 96%, and there have been no secondary graft failures. Of the first 31 patients, we had 2 graft failures, both of them occurring in patients with extremely high titers of anti-donor-specific HLA antibodies (anti-DSAs), but after adjusting the PTIS to include bortezomib and rituximab for patients with high titers of anti-DSAs and using pharmacologic dose guidance for busulfan, we had no graft failures in the last 52 patients. Six (7%) of 83 patients developed severe GVHD. We conclude that this is a safe and efficacious approach to allogeneic SCT in thalassemia, yielding results comparable to those available for patients with fully matched donors.

Proposed Therapeutic Range of Treosulfan in Reduced Toxicity Pediatric Allogeneic Hematopoietic Stem Cell Transplant Conditioning: Results From a Prospective Trial

Treosulfan is given off‐label in pediatric allogeneic hematopoietic stem cell transplant. This study investigated treosulfan's pharmacokinetics (PKs), efficacy, and safety in a prospective trial. Pediatric patients (n = 87) receiving treosulfan‐fludarabine conditioning were followed for at least 1 year posttransplant. PKs were described with a two‐compartment model. During follow‐up, 11 of 87 patients died and 12 of 87 patients had low engraftment (≤ 20% myeloid chimerism). For each increase in treosulfan area under the curve from zero to infinity (AUC_(0‐∞)) of 1,000 mg hour/L the hazard ratio (95% confidence interval) for mortality increase was 1.46 (1.23–1.74), and the hazard ratio for low engraftment was 0.61 (0.36–1.04). A cumulative AUC_(0‐∞) of 4,800 mg hour/L maximized the probability of success (> 20% engraftment and no mortality) at 82%. Probability of success with AUC_(0‐∞) between 80% and 125% of this target were 78% and 79%. Measuring PK at the first dose and individualizing the third dose may be required in nonmalignant disease.

Gene Therapy For Beta-Thalassemia: Updated Perspectives

Allogeneic hematopoietic stem cell transplantation was until very recently, the only permanent curative option available for patients suffering from transfusion-dependent beta-thalassemia. Gene therapy, by autologous transplantation of genetically modified hematopoietic stem cells, currently represents a novel therapeutic promise, after many years of extensive preclinical research for the optimization of gene transfer protocols. Nowadays, clinical trials being held on a worldwide setting, have demonstrated that, by re-establishing effective hemoglobin production, patients may be rendered transfusion- and chelation-independent and evade the immunological complications that normally accompany allogeneic hematopoietic stem cell transplantation. The present review will offer a retrospective scope of the long way paved towards successful implementation of gene therapy for beta-thalassemia, and will pinpoint the latest strategies employed to increase globin expression that extend beyond the classic transgene addition perspective. A thorough search was performed using Pubmed in order to identify studies that provide a proof of principle on the aforementioned topic at a preclinical and clinical level. Inclusion criteria also regarded gene transfer technologies of the past two decades, as well as publications outlining the pitfalls that precluded earlier successful implementation of gene therapy for beta-thalassemia. Overall, after decades of research, that included both successes and pitfalls, the path towards a permanent, donor-irrespective cure for beta-thalassemia patients is steadily becoming a realistic approach.

Gene Therapy for Hemoglobinopathies

Gene therapy for β-thalassemia and sickle-cell disease is based on transplantation of genetically corrected, autologous hematopoietic stem cells. Preclinical and clinical studies have shown the safety and efficacy of this therapeutic approach, currently based on lentiviral vectors to transfer a β-globin gene under the transcriptional control of regulatory elements of the β-globin locus. Nevertheless, a number of factors are still limiting its efficacy, such as limited stem-cell dose and quality, suboptimal gene transfer efficiency and gene expression levels, and toxicity of myeloablative regimens. In addition, the cost and complexity of the current vector and cell manufacturing clearly limits its application to patients living in less favored countries, where hemoglobinopathies may reach endemic proportions. Gene-editing technology may provide a therapeutic alternative overcoming some of these limitations, though proving its safety and efficacy will most likely require extensive clinical investigation.

HLA-haploidentical hematopoietic stem cell transplantation in pediatric patients with hemoglobinopathies: current practice and new approaches

We review current approaches in HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for pediatric patients with hemoglobinopathies with a focus on recent developments using TCRα/β+/CD19+ depleted grafts in patients with β-thalassemia major (TM) or sickle cell disease (SCD) in two European transplant units. Eleven TM and three SCD patients (Roma cohort) received a preparative regimen consisting of busulfan/thiotepa/cyclophosphamide/ATG preceded by fludarabine/hydroxyurea/azathioprine. The preparative regimen for 5 SCD patients included treosulfan/thiotepa/fludarabine/ATG (Berlin pilot cohort). All grafts were PBSC engineered by TCR-α/β+/CD19+ depletion. In both cohorts, rates for graft failure, treatment related mortality (TRM) and GvHD were encouraging. Overall survival (OS) and disease-free survival (DFS) in the Roma cohort were 84 and 69%, respectively, while OS and DFS are 100% in the Berlin cohort. Immune reconstitution was satisfactory. Although asymptomatic viral reactivation was common, no severe viral infection occured. These data confirm that TCR-α/β+/CD19+ depletion is a well-suited haplo-HSCT strategy for children with hemoglobinopathies. We discuss the results in the context of additional optimization strategies and introduce our concepts for multicenter trial protocols in Germany.

Allogeneic HSCT for Autoimmune Diseases: A Retrospective Study From the EBMT ADWP, IEWP, and PDWP Working Parties

Background: This retrospective study assessed the use and long-term outcome of allogeneic hematopoietic stem cell transplantation (HSCT) in patients with severe autoimmune diseases (ADs), reported to the European Society for Blood and Marrow Transplantation (EBMT) registry.

Methods: Between 1997 and 2014, 128 patients received allogeneic HSCT for various hematological (n = 49) and non-hematological (n = 79) refractory ADs. The median age was 12.7 years (0.2–62.2). Donors were syngeneic for seven, matched related for 46, unrelated for 51, haploidentical for 15, and cord blood for nine patients.

Results: The incidence of grades II-IV acute graft-vs.-host disease (GvHD) was 20.8% at 100 days. Cumulative incidence of chronic GvHD was 27.8% at 5-years. Non-relapse mortality (NRM) was 12.7% at 100-days. Overall survival (OS) and Progression-Free Survival (PFS) were 70.2 and 59.4% at 5-years, respectively. By multivariate analysis, age <18 years, males, and more recent year of transplant were found to be significantly associated with improved PFS. Reduced conditioning intensity was associated with a lower NRM. On a subgroup of 64 patients with detailed information a complete clinical response was obtained in 67% of patients at 1-year.

Conclusions: This large EBMT survey suggests the potential of allogeneic HSCT to induce long-term disease control in a large proportion of refractory ADs, with acceptable toxicities and NRM, especially in younger patients.

Population pharmacokinetics of treosulfan in paediatric patients undergoing hematopoietic stem cell transplantation

Aims

Treosulfan is an alkylating agent increasingly used prior to haematopoietic stem cell transplantation. The aim of this study was to develop a population pharmacokinetic (PK) model of treosulfan in paediatric haematopoietic stem cell transplantation recipients and to explore the effect of potential covariates on treosulfan PK. Also, a limited sampling model (LSM) will be developed to accurately predict treosulfan exposure suitable for a therapeutic drug monitoring setting.

Methods

In this multicentre study, 91 patients, receiving a total dose of 30, 36 or 42 g/m² treosulfan, administered over 3 consecutive days, were enrolled. A population PK model was developed and demographic factors, as well as laboratory parameters, were included as potential covariates. In addition, a LSM was developed using data from 28 patients.

Results

A 2‐compartment model with first order elimination best described the data. Bodyweight with allometric scaling and maturation function were identified as significant predictors of treosulfan clearance. Treosulfan clearance reaches 90% of adult values at 4 postnatal years. A model‐based dosing table is presented to target an exposure of 1650 mg*h/L (population median) for different weight and age groups. Samples taken at 1.5, 4 and 7 hours after start of infusion resulted in the best limited sampling strategy.

Conclusions

This study provides a treosulfan population PK model in children and captures the developmental changes in clearance. A 3‐point LSM allows for accurate and precise estimation of treosulfan exposure.

Bone marrow stromal cells from β-thalassemia patients have impaired hematopoietic supportive capacity

BACKGROUND. The human bone marrow (BM) niche contains a population of mesenchymal stromal cells (MSCs) that provide physical support and regulate hematopoietic stem cell (HSC) homeostasis. β-Thalassemia (BT) is a hereditary disorder characterized by altered hemoglobin beta-chain synthesis amenable to allogeneic HSC transplantation and HSC gene therapy. Iron overload (IO) is a common complication in BT patients affecting several organs. However, data on the BM stromal compartment are scarce.

METHODS. MSCs were isolated and characterized from BM aspirates of healthy donors (HDs) and BT patients. The state of IO was assessed and correlated with the presence of primitive MSCs in vitro and in vivo. Hematopoietic supportive capacity of MSCs was evaluated by transwell migration assay and 2D coculture of MSCs with human CD34⁺ HSCs. In vivo, the ability of MSCs to facilitate HSC engraftment was tested in a xenogenic transplant model, whereas the capacity to sustain human hematopoiesis was evaluated in humanized ossicle models.

RESULTS. We report that, despite iron chelation, BT BM contains high levels of iron and ferritin, indicative of iron accumulation in the BM niche. We found a pauperization of the most primitive MSC pool caused by increased ROS production in vitro which impaired MSC stemness properties. We confirmed a reduced frequency of primitive MSCs in vivo in BT patients. We also discovered a weakened antioxidative response and diminished expression of BM niche–associated genes in BT-MSCs. This caused a functional impairment in MSC hematopoietic supportive capacity in vitro and in cotransplantation models. In addition, BT-MSCs failed to form a proper BM niche in humanized ossicle models.

CONCLUSION. Our results suggest an impairment in the mesenchymal compartment of BT BM niche and highlight the need for novel strategies to target the niche to reduce IO and oxidative stress before transplantation.

FUNDING. This work was supported by the SR-TIGET Core grant from Fondazione Telethon and by Ricerca Corrente.

Hematopoietic Stem Cell Transplantation in Thalassemia

Although recent advances in gene therapy are expected to increase the chance of disease cure in thalassemia major, at present hematopoietic stem cell transplantation (HSCT) remains the only consolidated curative approach for this disorder. The widest experience has been obtained in the HLA-matched family donor (MFD) setting, with probabilities of overall and thalassemia-free survival exceeding 90% and 85%, respectively. As for most patients a suitable MFD is not available, alternative donors (HLA-matched unrelated donor, unrelated cord blood, HLA-haploidentical relative) have been increasingly explored, translating into the expansion of the number of patients treatable with HSCT.

Beyond transfusion therapy: new therapies in thalassemia including drugs, alternate donor transplant, and gene therapy

Transfusion combined with chelation therapy for severe β thalassemia syndromes (transfusion-dependent thalassemia [TDT]) has been successful in extending life expectancy, decreasing comorbidities and improving quality of life. However, this puts lifelong demands not only on the patients but also on the health care systems that are tasked with delivering long-term treatment and comprehensive support. Prevention programs and curative approaches are therefore an important part of overall strategy. Curative treatments alter the dynamic of a patient's health care costs, from financial commitment over 50 years, into a potential "one-off" investment. Since the 1980s, this has usually been available only to the 30% or so of young children with matched sibling donors. By improving the safety of matched related donors and haploidentical hematopoietic stem cell transplants, the potential size of the donor pool for curative therapies may be increased. Recent advances in gene therapy demonstrate that even patients lacking a matched donor can be rendered transfusion independent with an autograft of genetically modified autologous stem cells, with a low short-term risk. Noncurative treatments are also of potential value by decreasing use of blood and chelators and decreasing hospital visits. An example is luspatercept, an activin-receptor trap that modifies transforming growth factor-β signaling, thereby increasing the efficiency of erythropoiesis. This has entered phase 3 clinical trials for TDT and non-TDT and, usefully increases in both Hb and quality of life in non-TDT as well as decreasing transfusion requirements in TDT. Other novel noncurative treatments are entering clinical trials such improvement of erythropoiesis through pharmacological manipulation of hepcidin and iron metabolism.

Haploidentical Bone Marrow Transplantation with Post-Transplantation Cyclophosphamide Plus Thiotepa Improves Donor Engraftment in Patients with Sickle Cell Anemia: Results of an International Learning Collaborative

Curative therapy for individuals with severe sickle cell disease (SCD) who lack an HLA-identical sibling donor has been frustratingly elusive. In with the goal of improving engraftment while minimizing transplantation-related morbidity, a multi-institutional learning collaborative was developed in the context of a Phase II clinical trial of nonmyeloablative, related HLA-haploidentical (haplo) bone marrow transplantation (BMT) with post-transplantation cyclophosphamide. All eligible participants had hemoglobin SS, and 89% (16 of 18) had an identifiable donor. The median patient age was 20.9 years (IQR, 12.1 to 26.0 years), and the most common indication for transplantation was overt stroke (in 69%; 11 of 16). In the first 3 patients, the conditioning regimen consisted of antithymocyte globulin, fludarabine, cyclophosphamide, and low-dose total body irradiation. Graft-versus-host disease (GVHD) prophylaxis included post-transplantation cyclophosphamide, mycophenolate mofetil, and sirolimus. Primary graft rejection occurred in 2 of the 3 patients (67%), which triggered the study-stopping rule. To reduce graft rejection risk, thiotepa was added to the conditioning regimen, and then 15 patients (including 2 with previous graft rejection) underwent haplo-BMT with this thiotepa-augmented conditioning regimen. At a median follow-up of 13.3 months (interquartile range [IQR], 3.8 to 23.1 months), 93% (14 of 15) had >95% stable donor engraftment at 6 months, with 100% overall survival. The median time to neutrophil engraftment (>500) was 22 days (IQR, 19 to 27 days), and that for platelet engraftment (>50 x 10^9/L) was 28 days (IQR, 27 days to not reached). Two patients had grade III-IV acute GVHD, 1 patient had mild chronic GVHD, and 86% of patients (6 of 7) were off immunosuppression therapy by 1-year post-transplantation. Our data suggest that haplo-BMT with post-transplantation cyclophosphamide and thiotepa improves donor engraftment without significantly increasing morbidity or mortality and could dramatically expand curative options for individuals with SCD.

Fludarabine-based reduced toxicity yet myeloablative conditioning is effective and safe particularly in patients with high-risk thalassemia undergoing allogeneic transplantation

INTRODUCTION

Thalassemia major (TM) is an inherited disorder caused by ineffective erythropoiesis. At the present time, allogeneic stem cell transplantation (allo-SCT) is a curative option. Conventional busulfan and cyclophosphamide based myeloablative conditioning regimens are limited by increased toxicity, especially in high-risk patients. Replacement of cyclophosphamide with fludarabine has reduced toxicity and nonrelapse mortality (NRM), thus improving outcomes. We analyzed long-term data of our fludarabine-based myeloablative, reduced toxicity protocol, specifically in high-risk patients.

METHODS

We retrospectively analyzed a cohort of 47 consecutive patients with TM undergoing allo-SCT from matched donors, using the fludarabine-based regimen (reduced toxicity regimen). The median age of the cohort was 10 years. Thirty-eight patients (80%) were in the high-risk and nine patients (20%) were in the low-risk category. The primary aim of this analysis was thalassemia-free survival (TFS).

RESULTS

The rejection rate was 11% within high-risk patients with NRM of 2%. With a median follow-up period of 7 years (1-15 years), the 10-year TFS in the entire cohort was 87%, and the overall survival (OS) was 97%. The 10-year TFS and OS among the low-risk and high-risk groups were 90% versus 84%, respectively (P = 0.45) and 100% versus 96%, respectively (P = 0.5), and both subsets of patients did equally well.

CONCLUSION

In conclusion, replacement of high-dose cyclophosphamide with fludarabine is well tolerated with minimal regimen-related toxicity and acceptable rejection rates, especially in high-risk patients.

Unrelated and related donor transplantation for beta-thalassemia major: A single-center experience from India

Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment in patients with β-thalassemia major. A matched sibling or a related donor is usually found in only 25%-30% of the patients. There are limited data on matched unrelated donor (MUD) transplants from India. We reviewed HSCT outcome in 56 children with TM who underwent 57 transplants at our center. Related donor (RD) (n=43) and MUD (n=14) transplants were performed with TreoFluT-based conditioning regimen in majority (95%) of patients. Peripheral blood stem cells (PBSC) were the preferred (85%) source of stem cells. The overall survival (OS) at 1 year in RD and MUD groups was 87.6±5.2% and 85.7±9.4% at a median follow-up of 25 (1-92) months and 22.5 (1-50) months, respectively (P=.757). The thalassemia-free survival (TFS) at 1 year was 87.6±5.2% and 77.1±11.7% with a median follow-up of 24 (1-92) and 16.5 (1-50) months, respectively (P=.487). Although acute (14% vs 64%) and chronic graft-versus-host disease (GVHD) (13.9% vs 42.9%), infectious (39.5% vs 71.4%), and non-infectious (37.2% vs 78.5%) complications are higher in MUD transplant group, the present data show a comparable OS and TFS among RD and MUD group with treosulfan-based regimen using PBSC grafts.

Allogeneic hematopoietic stem cell transplantation in congenital hemoglobinopathies with myeloablative conditioning and rabbit anti-thymocyte globulin

Background

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy for β-thalassemia major (TM) and sickle cell disease (SCD) in children. Graft-versus-host disease (GVHD) and treatment-related mortality (TRM) remain significant challenges to improving survival after HSCT. Here, we analyzed the outcome of TM and SCD patients, who received allogeneic HSCT with myeloablative conditioning at our institution.

Methods

Twenty-two patients (15 TM, 7 SCD), with a median age of 9 years (range, 1.6–16.9), underwent allogeneic HSCT using busulfan, cyclophosphamide and rabbit anti-thymocyte globulin-based conditioning. Cells were derived from either the bone marrow (8 patients), or peripheral blood stem cells (14 patients). The majority of patients received HSCT from a matched sibling donor (N=18). GVHD prophylaxis included cyclosporine and short course methotrexate.

Results

All patients achieved donor engraftment. Two SCD patients died from TRM-related grade IV gut GVHD (N=1) or severe bronchiolitis obliterans (BO) (N=1). Cumulative incidence of acute and chronic GVHD was 36.4% and 32.7%, respectively. Veno-occlusive disease (VOD) occurred in 8 patients (36.4%), but resolved in all instances. Epstein-Barr virus (EBV)-related post-transplantation lymphoproliferative disease (PTLD) occurred in 1 patient. The overall survival (OS) was 90.9% (TM 100%, SCD 71.4%), with all patients achieving transfusion independence, while 8 achieved complete donor chimerism.

Conclusion

Busulfan, cyclophosphamide, and ATG-based conditioning for HSCT of TM and SCD patients did not result in graft failure, although modifications may be required to reduce VOD incidence. Further changes to donor type and cell source prioritization are necessary to minimize TRM and morbidity caused by GVHD.

Modified conditioning regimen improves outcomes of unrelated donor peripheral blood stem cell transplantation for β-thalassaemia major patients

BACKGROUND

The objective of this study was to evaluate the feasibility of a modified conditioning regimen for the treatment of patients with β-thalassaemia major (TM), using unrelated donor peripheral blood stem cell transplantation (UD-PBSCT).

METHODS

A modified conditioning regimen based on intravenous busulfan, cyclophosphamide, fludarabine, and antithymocyte globulin was performed in 50 consecutive childhood patients with β-TM and a median age of 4.6 years (range, 2-12 years). According to Pesaro's classification, three classes of risk are identified using the criteria of degree of hepatomegaly, portal fibrosis, and quality of the chelation treatment. Patients with three adverse criteria constituted class III, none of the adverse criteria constituted class I, and one or two of the adverse criteria formed class II. Ten patients were class I, 36 class II, and four class III. All patients were transplanted with UDs containing 37 of 10/10 human leukocyte antigen (HLA)-matched pairs, 11 of 9/10 matched pairs, and two of 8/10 matched pairs. The median follow-up was 36 months (range, 9-96 months).

RESULTS

All patients successfully achieved engraftment, two of whom developed persistent thrombocytopaenia. The incidence of acute graft-versus-host disease (aGVHD) grade III-IV and chronic graft-versus-host disease (cGVHD) were 12% and 8%, respectively. However, 8.3% of HLA-matched and 15.4% of HLA-mismatched patients developed aGVHD. The incidence of severe bacterial infections and fungal pneumonia was 12% and 20%, respectively. The 3-year overall survival, disease-free survival, graft rejection, and transplant-related mortality were 94%, 92%, 2%, and 6%, respectively.

CONCLUSION

This modified conditioning protocol effectively improved outcomes of UD-PBSCT for patients with β-TM.