Outcomes of allogeneic haematopoietic cell transplantation for myelofibrosis in children and adolescents: the retrospective study of the EBMT Paediatric Diseases WP.

This retrospective study evaluated 35 children (median age 5.2 years; range 0.4-18) with myelofibrosis (MF), including 33 with primary myelofibrosis and 2 with secondary myelofibrosis transplanted from matched sibling donor (MSD) (n = 17) or non-MSD (n = 18) between 2000 and 2022. Conditioning was usually chemotherapy-based (n = 33) and myeloablative (n = 32). Fifteen patients received bone marrow (BM), 14 haematopoietic cells (HC) from peripheral blood (PB), and 6 from cord blood (CB). Day +100 acute GvHD II-IV incidence was significantly lower after MSD-haematopoietic cell transplantation (MSD-HCT) than after non-MSD-HCT [18.8% (4.3-41.1) vs 58.8% (31-78.6); p = 0.01]. Six-year non-relapse mortality (NRM) was 18% (7.1-32.8), relapse incidence was 15.9% (5.6-30.9), progression-free survival (PFS) was 66.1% (47-79.7), GvHD-free relapse-free survival was 50% (30.6-66.7), and overall survival (OS) was 71.1% (51.4-84). Six-year PFS and OS were significantly higher after BM transplantation compared to HCT from other sources [85.1% (52.3-96.1) vs 50.8% (26.3-71), p = 0.03, and 90.9% (50.8-98.7) vs 54% (28.1-74.2), p = 0.01, respectively], whereas NRM was significantly lower [0% vs 32% (12.3-53.9); p = 0.02]. This first multicentre study on outcomes of allogeneic HCT in children with myelofibrosis proves feasibility and curative effect of transplantation in these children, suggests that bone marrow transplantation is associated with better outcomes, and indicates the need for further studies.

Successes and pitfalls in orphan drug development for sickle cell disease.

ABSTRACT: Sickle cell disease (SCD) is a hereditary red cell disorder with a large disease burden at a global level. In the United States and Europe, medicines may qualify for orphan designation (OD), a regulatory status that provides incentives to boost development. We evaluated the development of new therapies for SCD using data for OD granted in the United States and Europe over the last 2 decades (2000-2021). We analyzed their characteristics, pathophysiological targets, trends, and OD sponsors. We then investigated the approval outcomes, including the phase success rate and reasons for discontinuation across different variables. We identified 57 ODs for SCD: 43 (75.4%) small molecules, 32 (56.1%) for oral administration, and 36 (63.1%) for chronic use to prevent SCD complications. At the end of the study (2021), development of 34 of 57 ODs was completed. Four ODs were approved with a success rate of 11.8%. Products targeting upstream causative events of SCD pathophysiology had a 1.8 higher success rate compared with products targeting disease consequences. Large companies showed a fourfold higher success rate compared with small-medium enterprises. Failures in clinical development were mainly seen in phase 3 for a lack of efficacy on vaso-occlusive crisis as the primary study end point, likely related to variable definitions and heterogeneity of pain scoring and treatment. Both advances in SCD knowledge and regulatory incentives paved the way for new therapies for SCD. Our finding of high failure rates in late-stage clinical development signals the need for better early-stage predictive models, also in the context of meaningful clinical end points.

Busulfan-fludarabine- or treosulfan-fludarabine-based conditioning before allogeneic HSCT from matched sibling donors in paediatric patients with sickle cell disease: A study on behalf of the EBMT Paediatric Diseases and Inborn Errors Working Parties.

How important is choice of conditioning regimen in allogeneic haematopoietic stem cell transplantation (HSCT) for sickle cell disease (SCD)? We compared HSCT outcomes by conditioning regimen in paediatric patients with SCD from the EBMT registry. In 2010-2020, 251 patients aged <18 years underwent a first matched sibling donor (MSD) HSCT with conditioning based on busulfan-fludarabine (bu-flu; n = 89) or treosulfan-fludarabine (treo-flu; n = 162). In the bu-flu and treo-flu groups, 51.7% and 99.4% of patients, respectively, received thiotepa. Median follow-up was 2.7 years. Two-year overall survival (OS) was 98.7% (95% confidence interval [CI]: 90.9-99.8) with bu-flu and 99.3% (95% CI: 95.2-99.9) with treo-flu (p = 0.63). Grade III-IV acute graft-versus-host disease (GVHD) at 100 days was 2.4% (95% CI: 0.4-7.5) and 0.6% (0.1%-3.2%) for bu-flu and treo-flu respectively (p = 0.25). The 2-year incidence of extensive chronic GVHD was 1.5% (95% CI: 0.1-7.3) with bu-flu and 8.0% (95% CI: 4.1-13.3) with treo-flu (p = 0.057). These multinational data confirm the excellent curative capacity of MSD HSCT with myeloablative conditioning. Both conditioning regimens yielded excellent OS, low rates of acute and chronic GVHD, and low rates of graft failure.

[Access to medicines for rare diseases: regulatory aspects and public health priorities.] / L'accesso ai farmaci per malattie rare tra aspetti regolatori e priorità di salute pubblica.

INTRODUCTION: In the last decades, the development of drugs for rare diseases has been supported by regulatory and financial incentives. On the other hand, public health policies have increasingly taken into account the person affected by a rare disease in their strategies. In this perspective, we examined the relation between the regulatory framework on rare diseases and the regulatory framework on drug approval. Technical proposals have been brought forward to protect the needs of individuals. RESULTS: The legislative framework on rare diseases has developed both at a European and national level with the aim to strengthen the network of centers for diagnosis and care by increasing the degree of social and health protection, as well as to accelerate the assessment, approval and access to new drugs. Since 2000, 210 orphan drugs have been approved by the European Medicines Agency (EMA) (compared to an estimated 7-8,000 rare diseases). Of the 118 orphan drugs active in the community register as of 2020, 97 (82.2%) were available in Italy: 17 (17.5%) in class A; 58 (59.8%) in class H; 12 (12.4%) in class C; 10 (10.3%) in class C-nn. In 2020, expenditure on drugs with an orphan indication accounted for 6% of the total pharmaceutical expenditure (+47% since 2016). These drugs have benefited from incentives at both European and national levels, as well as inclusion in national early access programs. However, the average duration of the assessment process is above the 100-day limit set by law. DISCUSSION: The legislation on rare diseases has developed in different directions, and drug legislation has undoubtedly played a major role in terms of the results achieved. However, orphan drugs enter the market with a high price, which increasingly represents a problem of sustainability for health systems but notwithstanding Italy shows a high ratio between the level of social protection and access times. In this perspective, it is necessary to be provided with tools for a better system balance with a view to optimize these timeframes. Introducing in Italy a system for tracking the negotiation process that considers the clock stops as the EMA does, would allow to know at what point the negotiation process is. In addition, once the 100-day period is over (net of any clock stops) and in case of failure to reach a negotiation agreement, a second 60-day negotiation round could be proposed and so on. In this way, all the parts involved the system would have a clear scope of action to conclude the process in a flexible but certain timeframe. In this regard, the joint clinical assessments foreseen by the new HTA Regulations provide an additional opportunity to harmonize central decisions with national requirements.

Busulfan-fludarabine- or treosulfan-fludarabine-based myeloablative conditioning for children with thalassemia major.

Significant advances in supportive care for patients with transfusion-dependent thalassemia major (TDT) have improved patients' life expectancy. However, transfusion-associated iron overload remains a significant barrier to long-term survival with good quality of life. Today, allogeneic hematopoietic stem cell transplantation (HSCT) is the current curative standard of care. Alongside selection of the best available donor, an optimized conditioning regimen is crucial to maximize outcomes for patients with TDT undergoing HSCT. The aim of this retrospective analysis was to investigate the role of busulfan-fludarabine-based and treosulfan-fludarabine-based conditioning in TDT patients undergoing HSCT. We included 772 patients registered in the European Society for Blood and Marrow Transplantation (EBMT) database who underwent first HSCT between 2010 and 2018. Four hundred ten patients received busulfan-fludarabine-based conditioning (median age 8.6 years) and 362 patients received treosulfan-fludarabine-based conditioning (median age 5.7 years). Patient outcomes were retrospectively compared by conditioning regimen. Two-year overall survival was 92.7% (95% confidence interval: 89.3-95.1%) after busulfan-fludarabine-based conditioning and 94.7% (95% confidence interval: 91.7-96.6%) after treosulfan-fludarabine-based conditioning. There was a very low incidence of second HSCT overall. The main causes of death were infections, graft-versus-host disease, and rejection. In conclusion, use of busulfan or treosulfan as the backbone of myeloablative conditioning for patients with TDT undergoing HSCT resulted in comparably high cure rates. Long-term follow-up studies are warranted to address the important issues of organ toxicities and gonadal function.

One single bone marrow harvesting from donors under 3 years of age: assessing safety and efficacy of the procedure.

To candidate children as bone marrow donors raises two main concerns: donor safety and adequate marrow cell dose. Data in the field are limited and guidelines for child donor care management are lacking. In this context, we herein report the experience collected in our center by comparing very-young donors (defined as age ≤ 3 years) with young donors (defined as age > 3 years) who donated bone marrow (BM) for patients affected by beta-globin disorders.

Haploidentical HSCT for hemoglobinopathies: improved outcomes with TCRαß+/CD19+-depleted grafts.

We examined outcomes of haploidentical hematopoietic cell transplantation (haplo-HCT) using T-cell receptor αß+ (TCRαß+)/CD19+-depleted grafts (TCR group, 14 patients) in children with hemoglobinopathies. Patients received a preparative regimen consisting of busulfan, thiotepa, cyclophosphamide, and antithymocyte globulin preceded by fludarabine, hydroxyurea, and azathioprine. The median follow-up among surviving patients was 3.9 years. The 5-year probabilities of overall survival (OS) and disease-free survival (DFS) were 84% and 69%, respectively. The incidence of graft failure was 14%. We compared outcomes to a historical group of 40 patients with hemoglobinopathies who received CD34+-selected grafts (CD34 group). The median follow-up of surviving patients for the CD34 group was 7.5 years. The 5-year probabilities of OS and DFS were 78% and 39%, respectively. The CD34 group had a significantly higher incidence of graft failure (45%) than the TCR group (14%) (P = .048). The incidences of grades 2 to 4 acute graft-versus-host disease (GVHD) in the TCR and CD34 groups were 28% and 29%, respectively, and 21% and 10% (P = .1), respectively, for extensive chronic GVHD. Viral reactivation was common in both groups. The overall incidence of posttransplant lymphoproliferative disorders for the entire group was 16%. Among all patients, 5 developed autoimmune hemolytic anemia or thrombocytopenia, with the overall cumulative incidence of 11%. The 2 groups showed suboptimal CD4+ recovery within the first 6 months of transplantation with no significant difference between groups. These data demonstrate that TCRαß+/CD19+-depleted grafts are associated with a reduced incidence of graft failure, but delayed immune reconstitution and associated morbidity and mortality remain a significant challenge.

Posterior Reversible Encephalopathy Syndrome after Hematopoietic Cell Transplantation in Children with Hemoglobinopathies.

Posterior reversible encephalopathy syndrome (PRES) is a serious adverse event associated with calcineurin inhibitors used for graft-versus-host disease (GVHD) prophylaxis. We compared the incidence of PRES in children with thalassemia (n = 222, 1.4 to 17.8 years old) versus sickle cell disease (SCD; n = 59, 2 to 17 years old) who underwent hematopoietic cell transplantation from HLA-matched siblings or alternative donors and analyzed the risk factors for PRES. Overall, 31 children developed calcineurin inhibitor-related PRES (11%), including 30 patients with seizures and 1 patient without seizures. PRES incidence was significantly higher in SCD patients (22%; 95% confidence interval [CI], 10% to 32%) than in thalassemia patients (8%; 95% CI, 5% to 12%;P = .002). In multivariate analysis, factors associated with PRES were hypertension (hazard ratio [HR], 5.87; 95% CI, 2.57 to 13.43; P = .0001), SCD (HR, 2.49; 95% CI, 1.25 to 4.99; P = .009), and acute GVHD (HR 2.27; 95% CI, 1.06 to 4.85; P= .031). In the entire cohort overall survival (OS) was significantly higher in patients without versus with PRES (90% versus 77%; P = .02). In a subgroup analysis that including matched sibling transplants, OS and disease-free survival (DFS) were similar in thalassemia patients without PRES (92% and 88%, respectively) and with PRES (82% and 73%, respectively), whereas SCD patients with PRES had significantly lower OS (67%) and DFS (67%) than patients without PRES (94% and 94%, respectively; P = .008). Thus, SCD patients had a significantly higher incidence of PRES than thalassemia patients, and hypertension and GVHD were the 2 main risk factors for PRES in patients with hemoglobinopathies. Although PRES did not significantly influence survival in patients with thalassemia, patients with SCD had significantly lower survival after PRES.

Histological features of bone marrow in paediatric patients during the asymptomatic phase of early-stage Black African sickle cell anaemia.

Bone marrow histological features of sickle cell anaemia (SCA) patients during early stages and in the asymptomatic phase of the disease appear an interesting area of study, representing early-stage consequences of SCA with a close relation to its pathophysiology. Unfortunately, this field of research has never been specifically addressed before. Bone marrow biopsies from 26 consecutive Black African SCA patients (M:F=1.6:1; age 2-17 years), free of clinical signs of chronic bone marrow damage, with no recent history of symptomatic vaso-occlusive episodes, and waiting for haematopoietic stem cell transplantation (HSCT), underwent morphological, immunohistochemical and electron microscopy evaluation. Additional comparison with three bone marrow specimens from post-HSCT SCA patients and 10 bone marrow specimens from AS healthy carriers was performed. Bone marrow of SCA patients was normocellular or slighly hypercellular in all cases. Erythroid hyperplasia was a common feature. Myeloid lineage was slightly decreased with normal to slightly diminished neutrophilic granulocytes; CD68 positive monocytic-macrophagic cells appeared slightly increased, with a predominant CD163 positive M2/M(Hb) phenotype. A positive correlation was found between haemoglobin values and number of bone marrow erythroid cells (R2=0.15, p=0.05). Intravascular and interstitial clusters of erythroid sickle cells were found in bone marrow of pre-HSCT homozygous SS SCA patients, as well as heterozygous AS healthy carriers, and the single post-HSCT patient matched to an AS health carrier donor.

Structural and Functional Insights on an Uncharacterized Aγ-Globin-Gene Polymorphism Present in Four ß0-Thalassemia Families with High Fetal Hemoglobin Levels.

INTRODUCTION: Several DNA polymorphisms have been associated with high production of fetal hemoglobin (HbF), although the molecular basis is not completely understood. In order to identify and characterize novel HbF-associated elements, we focused on five probands and their four families (from Egypt, Iraq and Iran) with thalassemia major (either ß(0)-IVSII-1 or ß(0)-IVSI-1) and unusual HbF elevation (>98 %), congenital or acquired after rejection of bone marrow transplantation, suggesting an anticipated favorable genetic background to high HbF expression. METHODS: Patient recruitment, genomic DNA sequencing, western blotting, electrophoretic mobility shift assays, surface plasmon resonance (SPR) biospecific interaction analysis, bioinformatics analyses based on docking experiments. RESULTS: A polymorphism of the Aγ-globin gene is here studied in four families with ß(0)-thalassemia (ß(0)-IVSII-1 and ß(0)-IVSI-1) and expressing unusual high HbF levels, congenital or acquired after rejection of bone marrow transplantation. This (G→A) polymorphism is present at position +25 of the Aγ-globin genes, corresponding to a 5'-UTR region of the Aγ-globin mRNA and, when present, is physically linked in chromosomes 11 of all the familiar members studied to the XmnI polymorphism and to the ß(0)-thalassemia mutations. The region corresponding to the +25(G→A) polymorphism of the Aγ-globin gene belongs to a sequence recognized by DNA-binding protein complexes, including LYAR (Ly-1 antibody reactive clone), a zinc-finger transcription factor previously proposed to be involved in down-regulation of the expression of γ-globin genes in erythroid cells. CONCLUSION: We found a novel polymorphism of the Aγ-globin gene in four families with ß(0)-thalassemia and high levels of HbF expression. Additionally, we report evidence suggesting that the Aγ-globin gene +25(G→A) polymorphism decreases the efficiency of the interaction between this sequence and specific DNA binding protein complexes.

Optimal Outcomes in Young Class 3 Patients With Thalassemia Undergoing HLA-Identical Sibling Bone Marrow Transplantation.

BACKGROUND: Bone marrow transplantation (BMT) for class 3 patients with thalassemia is challenging due to high rates of graft rejection and transplant-related mortality. Since the first studies of BMT in the late 1980s, a number of conditioning regimens have been designed to improve outcomes, but with suboptimal results. Here we report the outcome of transplantation in class 3 patients using a modified protocol. METHODS: Sixty-three patients between 5 and 16.7 years of age with class 3 thalassemia received HLA-matched sibling BMT following either the original protocol (26 patients) or the modified protocol (37 patients). Both regimens comprised preconditioning cytoreduction with hydroxyurea and azathioprine starting at -45 days pretransplant, and fludarabine from days -16 to -12. Conditioning was performed with busulfan and cyclophosphamide (original protocol) or with busulfan, thiotepa, and cyclophosphamide (modified protocol). RESULTS: The 2 groups showed similar patient demographics. At day 0, the degree of cytoreduction (lymphopenia, neuthropenia, and thrombocytopenia) achieved by the modified protocol was greater than the original protocol. The incidence of graft failure/rejection was significantly higher in the original group (15%; 95% confidence interval [95% CI], 5-32%) compared with the modified group (0%) (P = 0.014). The respective 5-year thalassemia-free survival rates were 73% (95% CI, 51-86%) and 92% (95% CI, 77-97%) (P = 0.047). Both groups showed similar incidences of grades II to IV acute graft-versus host disease. Modified protocol did not increase nonhematological toxicity or infectious complications. CONCLUSIONS: The modified treatment protocol effectively and safely prevented graft failure/rejection and significantly increased thalassemia-free survival of class 3 patients with thalassemia.

Haematopoietic stem cell transplantation in Nigerian sickle cell anaemia children patients.

BACKGROUND: Sickle cell anaemia (SCA) remains associated with high risks of morbidity and early death. Children with SCA are at high risk for ischaemic stroke and transient ischaemic attacks, secondary to intracranial arteriopathy involving carotid and cerebral arteries. Allogeneic haematopoietic stem cell transplantation (HSCT) is the only curative treatment for SCA. We report our experience with transplantation in a group of patients with the Black African variant of SCA. PATIENTS AND METHODS: This study included 31 consecutive SCA patients who underwent bone marrow transplantation from human leukocyte antigen (HLA)-identical sibling donors between 2010 and 2014 following a myeloablative-conditioning regimen. RESULTS: The median patient age was 10 years (range 2-17 years). Before transplantation, 14 patients had recurrent, painful, vaso-occlusive crisis; ten patients had recurrent painful crisis in association with acute chest syndrome; three patients experienced ischaemic stroke and recurrent vaso-occlusive crisis; two patients experienced ischaemic stroke; one patient exhibited leukocytosis; and one patient exhibited priapism. Of the 31 patients, 28 survived without sickle cell disease, with Lansky/Karnofsky scores of 100. All surviving patients remained free of any SCA-related events after transplantation. CONCLUSION: The protocols used for the preparation to the transplant in thalassaemia are very effective also in the other severe haemoglobinopathy as in the sickle cell anaemia with 90% disease free survival. Today, if a SCA patient has a HLA identical family member, the cellular gene therapy through the transplantation of the allogeneic haemopoietic cell should be performed. Tomorrow, hopefully, the autologous genetically corrected stem cell will break down the wall of the immunological incompatibility.

Invasive pulmonary aspergillosis in a haematopoietic stem cell transplant recipient with sickle cell disease: a successful treatment.

Sickle Cell Anaemia (SCA) is the most common inherited blood disorder and is associated with severe morbidity and decreased survival. Allogeneic Haematopoietic Stem Cell Transplantation (HSCT) is the only curative approach. Nevertheless the decision to perform a bone marrow transplant includes the risk of major complications and transplant-related mortality. Infections represent the leading cause of death in SCA patients undergoing HSCT. Invasive Pulmonary Aspergillosis (IPA) is a devastating opportunistic infection and remains a significant cause of morbidity and mortality in HSCT recipients. Data regarding IPA in the setting of SCA are lacking. In the present report, we describe a patient with SCA, who developed IPA after allogeneic bone marrow transplant. The fungal infection was treated by systemic antifungal therapy in addition to surgery, despite mild chronic graft versus host disease (GVHD) and continuing immunosuppressive therapy. This case shows that IPA occurring in bone marrow recipients with SCA can be successfully treated.

New insights into the pharmacokinetics of intravenous busulfan in children with sickle cell anemia undergoing bone marrow transplantation.

BACKGROUND: Busulfan (Bu) is an integral part of conditioning regimens for patients with sickle cell anemia (SCA) undergoing transplantation. Patients with SCA might predispose to transplant-related neurological and pulmonary toxicities due to pre-existing disease-related cerebrovascular and lung injury. Bu therapy appears to be an important contributing factor in this context. PROCEDURE: We studied the pharmacokinetics of intravenous Bu and clinical outcomes of 36 children with SCA undergoing bone marrow transplantation. Most patients had pre-existing organ system damage. Busulfan was administered every 6 hr for 4 days with pharmacokinetic-guided dose adjustment to target a conservative area under the concentration versus time curve (AUC) range of 900-1,350 µMol*min. RESULTS: We found that the first-dose Bu clearance was significantly higher (P < 0.0005) than the subsequent daily clearance, which remained unchanged during the following days. After the first-dose, 69% of patients achieved the target range. We adapted a new dose-adjustment strategy targeting exposures to the lower end (900 µMol*min) of the AUC range after the first dose of Bu to avoid unnecessary dose increases on subsequent days due to differences in clearance. This strategy enabled most patients to maintain the AUC within therapeutic range following dose adjustments. CONCLUSIONS: Differences in Bu clearance after the first-dose and subsequent daily doses in patients with SCA should be considered for pharmacokinetic-guided dose adjustment. Conservative AUC range and targeting exposures to the lower end of the range after the first dose was associated with negligible toxicity, and high engraftment and sickle cell-free survival rates.

Peripheral red blood cell split chimerism as a consequence of intramedullary selective apoptosis of recipient red blood cells in a case of sickle cell disease.

Allogeneic cellular gene therapy through hematopoietic stem cell transplantation is the only radical cure for congenital hemoglobinopathies like thalassemia and sickle cell anemia. Persistent mixed hematopoietic chimerism (PMC) has been described in thalassemia and sickle cell anemia. Here, we describe the clinical course of a 6-year-old girl who had received bone marrow transplant for sickle cell anemia. After the transplant, the patient showed 36% donor hematopoietic stem cells in the bone marrow, whereas in the peripheral blood there was evidence of 80% circulating donor red blood cells (RBC). The analysis of apoptosis at the Bone Marrow level suggests that Fas might contribute to the cell death of host erythroid precursors. The increase in NK cells and the regulatory T cell population observed in this patient suggests that these cells might contribute to the condition of mixed chimerism.

Reduction of intramedullary apoptosis after stem cell transplantation in black african variant of pediatric sickle cell anemia.

BACKGROUND AND PURPOSE: Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment for sickle cell anemia (SCA). We report our experience with transplantation in children with the Black African variant of SCA and the effects of transplant on erythroid compartment in bone marrow (BM). PATIENTS AND METHODS: Twenty-seven consecutive patients who underwent BM transplantation from HLA-identical donors following a myeloablative conditioning regimen were included. Using both CD71 and FSC parameters, we obtained three erythroid populations: EryA-C. Ery A (CD71(high) FSC(high)) are basophilic; Ery B (CD71(high) FSC(low)) are late basophilic and polychromatic; and Ery C (CD71(low) FSC(low)) are orthochromatic erythroblasts and reticulocytes. To analyze the effect of transplantation on intramedullary apoptosis, we studied Fas (CD95+) and caspase-3 expression in erythroblast subpopulations. RESULTS: All patients experienced sustained engraftment, and all surviving patients remained free of SCA-related events after transplantation. The erythroid population showed expansion in the BM at baseline. After transplant, levels decreased, especially of Ery C, in parallel to reduced Fas expression and an initial caspase 3 increase in erythroid population, similar to reported later steps of "normal" erythroid maturation. CONCLUSIONS: The results suggest a good chance of cure for children with SCA, with an excellent survival rate. We also observed "normalization" of erythroid populations in parallel with a decreased intramedullary apoptosis rate, suggesting normal erythroid maturation in ex-SCA patients after HSCT.

Bone marrow transplantation for thalassemia from alternative related donors: improved outcomes with a new approach.

Bone marrow transplantation (BMT) performance can be limited by a lack of ideal donors, and the role of alternative donor hematopoietic cell transplantation in thalassemia is not well established. Here we used a new treatment protocol (Pc 26.1) in 16 thalassemia patients to perform BMT using phenotypically HLA-identical or 1-antigen-mismatched relatives (related donors [RDs]). We compared these results with HLA-matched sibling (matched sibling donors [MSDs]) BMT in 66 patients. The entire RD group and 88% of MSD group had sustained engraftment. Rejection incidence was 0% in the RD and 12% (95% confidence interval [95% CI], 6%-21%) in MSD groups (P = .15), with respective thalassemia-free survival probabilities of 94% (95% CI, 63%-99%) and 82% (95% CI, 70%-89%) (P = .24). Transplant-related mortality was 6% (95% CI, 1%-26%) in the RD group and 8% (95% CI, 3%-16%) in the MSD group (P = .83). The intensified new protocol was not associated with increased nonhematologic toxicity. The present data show that the Pc 26.1 preparative regimen allows thalassemia patients to safely undergo BMT from RDs who are not HLA-matched siblings, with transplant outcomes similar to patients with MSD grafts.

Hematopoietic stem cell transplantation in thalassemia and sickle cell anemia.

The globally widespread single-gene disorders ß-thalassemia and sickle cell anemia (SCA) can only be cured by allogeneic hematopoietic stem cell transplantation (HSCT). HSCT treatment of thalassemia has substantially improved over the last two decades, with advancements in preventive strategies, control of transplant-related complications, and preparative regimens. A risk class-based transplantation approach results in disease-free survival probabilities of 90%, 84%, and 78% for class 1, 2, and 3 thalassemia patients, respectively. Because of disease advancement, adult thalassemia patients have a higher risk for transplant-related toxicity and a 65% cure rate. Patients without matched donors could benefit from haploidentical mother-to-child transplantation. There is a high cure rate for children with SCA who receive HSCT following myeloablative conditioning protocols. Novel non-myeloablative transplantation protocols could make HSCT available to adult SCA patients who were previously excluded from allogeneic stem cell transplantation.