Outcome of patients with hemoglobinopathies given either cord blood or bone marrow transplantation from an HLA-identical sibling. Blood. 2013;122:1072-1078. [PMID: 23692854 DOI: 10.1182/blood-2013-03-489112]

Advances in umbilical cord blood cell therapy: the present and the future

INTRODUCTION

Umbilical cord blood (UCB), previously seen as medical waste, is increasingly recognized as a valuable source of cells for therapeutic use. The best-known application is in hematopoietic stem cell transplantation (HSCT), where UCB has become an increasingly important graft source in the 28 years since the first umbilical cord blood transplantation (UCBT) was performed. Recently, UCB has been increasingly investigated as a putative source for adoptive cell therapy. Areas covered: This review covers the advances in umbilical cord blood transplantation (UCBT) to overcome the limitation regarding cellular dose, immunological naivety and additional cell doses such as DLI. It also provides an overview regarding the progress in adoptive cellular therapy using UCB. Expert opinion: UCB has been established as an important source of stem cells for HSCT. Successful strategies to overcome the limitations of UCBT, such as the limited cell numbers and naivety of the cells, are being developed, including novel methods to perform in vitro expansion of progenitor cells, and to improve their homing to the bone marrow. Promising early clinical trials of adoptive therapies with UCB cells, including non-immunological cells, are currently performed for viral infections, malignant diseases and in regenerative medicine.

Treosulfan-Based Conditioning Regimen in Sibling and Alternative Donor Hematopoietic Stem Cell Transplantation for Children with Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Lack of suitable donors and regimen related toxicity are major barriers for hematopoietic stem cell transplantation (HSCT) in patients with sickle cell disease (SCD). The aim of the study is the assessment of efficacy and toxicity of Treosulfan-based conditioning regimen for SCD also when alternative donors such as mismatched unrelated donor and haploidentical donor are employed.

METHODS

We report our single-center experience: 11 patients with SCD received HSCT with a Treosulfan/Thiotepa/Fludarabine/Anti-thymoglobulin conditioning regimen between 2010 and 2015. The donor was a matched sibling donor (n= 7), a haploidentical parent (n= 2), a matched unrelated donor (n= 1) or a mismatched unrelated donor (n=1). The haploidentical and mismatched unrelated donor grafts were manipulated by removing TCRαβ and CD19 positive cells.

RESULTS

All patients survived the procedure and achieved stable engraftment. Stable mixed chimerism was observed in 5/11 patients. Grade III-IV regimen related toxicity was limited to mucositis and no grade III-IV graft-versus-host disease (GvHD) occurred. No SCD manifestation was observed post transplant and cerebral vasculopathy improved in 3/5 evaluable patients. Organ function evaluation showed no pulmonary, cardiac or renal toxicity but gonadal failure occurred in 1/4 evaluable patients.

CONCLUSION

Our data suggest that Treosulfan is associated with low toxicity and may be employed also for unrelated and haploidentical donor HSCT.

Hematopoietic Stem Cell Transplantation in Adult Sickle Cell Disease: Problems and Solutions

Sickle cell disease-related organ injuries cannot be prevented despite hydroxyurea use, infection prophylaxis, and supportive therapies. As a consequence, disease-related mortality reaches 14% in adolescents and young adults. Hematopoietic stem cell transplantation is a unique curative therapeutic approach for sickle cell disease. Myeloablative allogeneic hematopoietic stem cell transplantation is curative for children with sickle cell disease. Current data indicate that long-term disease-free survival is about 90% and overall survival about 95% after transplantation. However, it is toxic in adults due to organ injuries. In addition, this curative treatment approach has several limitations, such as difficulties to find donors, transplant-related mortality, graft loss, graft-versus-host disease (GVHD), and infertility. Engraftment effectivity and toxicity for transplantations performed with nonmyeloablative reduced-intensity regimens in adults are being investigated in phase 1/2 trials at many centers. Preliminary data indicate that GVHD could be prevented with transplantations performed using reduced-intensity regimens. It is necessary to develop novel regimens to prevent graft loss and reduce the risk of GVHD.

Current Results and Future Research Priorities in Late Effects after Hematopoietic Stem Cell Transplantation for Children with Sickle Cell Disease and Thalassemia: A Consensus Statement from the Second Pediatric Blood and Marrow Transplant Consortium International Conference on Late Effects after Pediatric Hematopoietic Stem Cell Transplantation

Sustained donor engraftment after allogeneic hematopoietic cell transplantation (HCT) converts to healthy donor hemoglobin synthesis and halts disease symptoms in patients with sickle cell disease and thalassemia major. A disease-free survival probability that exceeds 90% has been reported when HCT using an HLA-matched sibling donor is performed in young patients with low-risk disease or treatment-related risk factors. Alternate donor HCT and HCT in adults is performed infrequently because of a higher risk profile. Transplant-specific risks include conditioning regimen-related toxicity, graft-versus-host disease, graft rejection with marrow aplasia or disease recurrence, and infections associated with immunosuppression and delayed immune reconstitution. The magnitude of risk depends on patient age, clinical status of the underlying disease (eg, organ injury from vasculopathy and iron overload), donor source, and intensity of the conditioning regimen. These risks are commonly monitored and reported in the short term. Documenting very late outcomes is important, but these data are rarely reported because of challenges imposed by patient drop-out and insufficient resources. This report summarizes long-term follow-up results after HCT for hemoglobin disorders, identifies gaps in knowledge, and discusses opportunities for future investigations. This consensus summary will be followed by a second article detailing comprehensive long-term follow-up recommendations to aid in maintaining health in these individuals and identifying late complication risks that could facilitate interventions to improve outcomes.

Alternative Donor/Unrelated Donor Transplants for the β-Thalassemia and Sickle Cell Disease

Considerable progress with respect to donor source has been achieved in allogeneic stem cell transplant for patients with hemoglobin disorders, with matched sibling donors in the 1980s, matched unrelated donors and cord blood sources in the 1990s, and haploidentical donors in the 2000s. Many studies have solidified hematopoietic progenitors from matched sibling marrow, cord blood, or mobilized peripheral blood as the best source-with the lowest graft rejection and graft versus host disease (GvHD), and highest disease-free survival rates. For patients without HLA-matched sibling donors, but who are otherwise eligible for transplant, fully allelic matched unrelated donor (8/8 HLA-A, B, C, DRB1) appears to be the next best option, though an ongoing study in patients with sickle cell disease will provide data that are currently lacking. There are high GvHD rates and low engraftment rates in some of the unrelated cord transplant studies. Haploidentical donors have emerged in the last decade to have less GvHD; however, improvements are needed to increase the engraftment rate. Thus the decision to use unrelated cord blood units or haploidentical donors may depend on the institutional expertise; there is no clear preferred choice over the other. Active research is ongoing in expanding cord blood progenitor cells to overcome the limitation of cell dose, including the options of small molecule inhibitor compounds added to ex vivo culture or co-culture with supportive cell lines. There are inconsistent data from using 7/8 or lower matched unrelated donors. Before routine use of these less matched donor sources, work is needed to improve patient selection, conditioning regimen, GvHD prophylaxis, and/or other strategies.

Personalized medicine and blood disorders

Personalized medicine has been using genomics approaches to elucidate the etiology of a disease as well as to personalize the management for patients of a particular disease based on that individual's genetic features. It benefits patients across a multitude of therapeutic areas and advancements are particularly evident in hematology/oncology. The importance of genomics discoveries and development in nonmalignant blood disorders generally goes unrecognized, but it becomes critical now due to the global disease burden and a high mortality. This paper focuses on the exploration of personalized medicine applications in hemoglobin diseases, and thrombotic and bleeding disorders. It discusses the challenges which slow down the implementation as well. The available data suggest that the ability to understand the clinical features of a patient's genetic profile and the knowledge of disease mechanisms are the keys to facilitate new diagnosis, new therapies, new prescriptions and better healthcare.

Immunosuppressive therapy versus alternative donor hematopoietic stem cell transplantation for children with severe aplastic anemia who lack an HLA-matched familial donor

We compared the outcomes of immunosuppressive treatment (IST) with those of alternative donor hematopoietic stem cell transplantation (HSCT) in children and adolescents with severe aplastic anemia (SAA). The medical records of 42 patients with SAA who received frontline IST (N=19) or frontline HSCT with an alternative donor (N=23) between 1998 and 2012 were analyzed retrospectively. Six patients responded in the frontline IST group, whereas 11 underwent salvage HSCT after IST failure. Twenty-one of 23 patients who underwent frontline HSCT survived without treatment failure. The estimated failure-free survival rate of the frontline HSCT group was higher than that of the frontline IST group (91.3% vs 30.7% respectively, P<0.001). Six of 11 patients who underwent salvage HSCT experienced event-free survival (EFS). The estimated EFS of the frontline HSCT group was higher than that of the salvage HSCT group (91.3% vs 50.9% respectively, P=0.015). The outcome of alternative donor HSCT was better than commonly reported rates, especially in patients who underwent frontline HSCT. These results suggest that frontline alternative donor HSCT may be a better treatment option than IST for children and adolescents with SAA who lack a human leukocyte Ag-matched familial donor.

A trial of unrelated donor marrow transplantation for children with severe sickle cell disease

Children with sickle cell disease experience organ damage, impaired quality of life, and premature mortality. Allogeneic bone marrow transplant from an HLA-matched sibling can halt disease progression but is limited by donor availability. A Blood and Marrow Transplant Clinical Trials Network (BMT CTN) phase 2 trial conducted from 2008 to 2014 enrolled 30 children aged 4 to 19 years; 29 were eligible for evaluation. The primary objective was 1-year event-free survival (EFS) after HLA allele-matched (at HLA-A, -B, -C, and -DRB1 loci) unrelated donor transplant. The conditioning regimen included alemtuzumab, fludarabine, and melphalan. Graft-versus-host disease (GVHD) prophylaxis included calcineurin inhibitor, short-course methotrexate, and methylprednisolone. Transplant indications included stroke (n = 12), transcranial Doppler velocity >200 cm/s (n = 2), ≥3 vaso-occlusive pain crises per year (n = 12), or ≥2 acute chest syndrome episodes (n = 4) in the 2 years preceding enrollment. Median follow-up was 26 months (range, 12-62 months); graft rejection was 10%. The 1- and 2-year EFS rates were 76% and 69%, respectively. The corresponding rates for overall survival were 86% and 79%. The day 100 incidence rate of grade II-IV acute GVHD was 28%, and the 1-year incidence rate of chronic GVHD was 62%; 38% classified as extensive. There were 7 GVHD-related deaths. A 34% incidence of posterior reversible encephalopathy syndrome was noted in the first 6 months. Although the 1-year EFS met the prespecified target of ≥75%, this regimen cannot be considered sufficiently safe for widespread adoption without modifications to achieve more effective GVHD prophylaxis. The BMT CTN #0601 trial was registered at www.clinicaltrials.gov as #NCT00745420.

Umbilical cord blood cells from unrelated donor as an alternative source of hematopoietic stem cells for transplantation in children and adults

Umbilical cord blood (CB) is an alternative source of hematopoietic stem cells (HSC) for patients requiring allogeneic HSC transplantation but lacking a suitable human leukocyte antigen (HLA)-matched donor. Using CB has many advantages, including lower HLA-matching requirements, increased donor availability, and low rates of graft-versus-host disease. Furthermore, with over 630,000 cryopreserved volunteer CB units currently stored in international CB banks worldwide, CB is rapidly available for those patients requiring urgent transplantation. However, concern remains over the low HSC doses available in CB grafts, resulting in delayed engraftment and poor immune reconstitution. This article reviews the current use and future developments of unrelated allogeneic CB transplantation (CBT). An overview of the encouraging results of CBT and the comparisons with other HSC sources and transplant strategies both in children and adults with malignant and non-malignant diseases are shown. We will discuss important factors that need to be considered when selecting CB units for transplantation to further improve the results of CBT.

Treating hemoglobinopathies using gene-correction approaches: promises and challenges

Hemoglobinopathies are genetic disorders caused by aberrant hemoglobin expression or structure changes, resulting in severe mortality and health disparities worldwide. Sickle cell disease (SCD) and β-thalassemia, the most common forms of hemoglobinopathies, are typically treated using transfusions and pharmacological agents. Allogeneic hematopoietic stem cell transplantation is the only curative therapy, but has limited clinical applicability. Although gene therapy approaches have been proposed based on the insertion and forced expression of wild-type or anti-sickling β-globin variants, safety concerns may impede their clinical application. A novel curative approach is nuclease-based gene correction, which involves the application of precision genome-editing tools to correct the disease-causing mutation. This review describes the development and potential application of gene therapy and precision genome-editing approaches for treating SCD and β-thalassemia. The opportunities and challenges in advancing a curative therapy for hemoglobinopathies are also discussed.

Haematopoietic stem cell transplantation for sickle cell disease - current practice and new approaches

Sickle cell disease is an inherited disorder that affects over 5 million people worldwide. Current maintenance therapy has been successful in reducing complications and enhancing life expectancy; yet subclinical complications persist. To date, allogeneic haematopoietic stem cell transplant (HSCT) remains the only available curative therapy for sickle cell disease. With declining incidences of rejection and transplant- related mortality, disease-free survival after human leucocyte antigen-identical sibling transplant exceeds 90%. However, the majority of individuals with sickle cell disease do not have an human leucocyte antigen (HLA)-identical sibling; therefore, research is expanding to focus on new approaches to alternative donor transplant. Advances in supportive care and conditioning regimens have led to expansion of the pool of donors to unrelated donors and haploidentical donors. Challenges remain in improving the safety and efficacy of HSCT from alternate donors. Early results from gene therapy may provide another curative option in patients with sickle cell disease. These approaches show early promise, but larger, longitudinal studies are needed to better determine the optimal clinical circumstances for transplant in sickle cell disease.

Unrelated donor stem cell transplantation for transfusion-dependent thalassemia

Thalassemia major is characterized by severe anemia dependent on red cell transfusions from infancy. Conservative management requires a safe source of compatible blood throughout life, strategies to combat iron overload, monitoring and treatment of transfusion-related complications, and management of cardiac and/or hepatic dysfunction from iron accumulation. Complications can result in premature morbidity and mortality. Stem cell transplantation is curative, but outcomes depend on the availability of a histocompatible donor, recipient age, and disease-related complications. Successful transplantation requires stable donor engraftment and donor-derived erythropoiesis and a low incidence of graft-versus-host disease, organ toxicities, and mortality. This translates to a cure with good quality of life and life span. Since recipients are at a high risk for graft rejection (prior transfusions, immunocompetency), myeloablative transplants have been the norm. Recent modifications to standard preparative regimens have significantly reduced transplant toxicities, resulting in >80% disease-free survival in children. Aiming to further reduce regimen-related toxicities, such as veno-occlusive liver disease and sterility, a recent trial explored reduced-intensity conditioning in unrelated donor (URD) transplants utilizing marrow or umbilical cord blood in patients without suitable familial donors. This report summarizes advances in URD transplantation for thalassemia, focusing on conditioning regimen nuances.

Current Indications, Techniques, and Imaging Findings of Stem Cell Treatment and Bone Marrow Transplant

The role of stem cell therapy in the treatment of hematologic and nonhematologic conditions is ever increasing. A thorough knowledge of the applications of stem cells and transplant physiology is essential for understanding the imaging manifestations. Stem cell imaging includes molecular imaging, and diagnostic and interventional radiology. It is possible to make a diagnosis of various complications and diseases associated with stem cell transplant. This article presents a simplified overview of stem cell applications and techniques with focus on hematopoietic stem cell transplant imaging.

Sibling cord blood donor program for hematopoietic cell transplantation: the 20-year experience in the Rome Cord Blood Bank

Umbilical cord blood (UCB) represents a source of hematopoietic stem cells for patients lacking a suitably matched and readily available related or unrelated stem cell donor. As UCB transplantation from compatible sibling provides good results in children therefore directed sibling UCB collection and banking is indicated in family who already have a child with a disease potentially treatable with an allogeneic hematopoietic stem cell transplantation. Particularly, related UCB collection is recommended when the patients urgently need a transplantation. To provide access to all patients in need, we developed a "Sibling cord blood donor program for hematopoietic cell transplantation". Here we report results of this project started 20years ago. To date, in this study a total of 194 families were enrolled, a total of 204 UCB samples were successfully collected and 15 pediatric patients have been transplanted. Recently, some authors have suggested novel role for UCB other than in the transplantation setting. Therefore, future studies in the immunotherapy and regenerative medicine areas could expand indication for sibling directed UCB collection.

Novel insights in the management of sickle cell disease in childhood

Sickle cell disease (SCD) is a life-threatening genetic disorder characterized by chronic hemolytic anemia, vascular injury and multiorgan dysfunctions. Over the last few decades, there have been significant improvements in SCD management in Western countries, especially in pediatric population. An early onset of prophylaxis with Penicillin and a proper treatment of the infections have increased the overall survival in childhood. Nevertheless, management of painful episodes and prevention of organ damage are still challenging and more efforts are needed to better understand the mechanisms behind the development of chronic organ damages. Hydroxyurea (Hydroxycarbamide, HU), the only medication approved as a disease-modifying agent by the United States Food and Drug Administration and the European Medicines Agency, is usually under-used, especially in developing countries. Currently, hematopoietic stem-cell transplantation is considered the only curative option, although its use is limited by lack of donors and transplant-related toxicity. SCD symptoms are similar in children and adults, but complications and systemic organ damages increase with age, leading to early mortality worldwide. Experts in comprehensive care of young patients with SCD, especially those approaching the transition age to adulthood, are missing, leading people to rely on urgent care, increasing health care utilization costs and inappropriate treatments. It would be important to establish programs of comprehensive healthcare for patients with SCD from birth to adulthood, to improve their quality and expectancy of life.

Update of hematopoietic cell transplantation for sickle cell disease

PURPOSE OF REVIEW

Hematopoietic cell transplantation (HCT) is a curative therapy for sickle cell disease (SCD) that is utilized very rarely because of limited allogeneic donor availability, limited healthcare resources needed to expand the treatment to regions in the world where most affected individuals reside, and by a view among SCD experts that HCT lacks the evidential rigor with short and long-term toxicity profiles that together might support its broader application.

RECENT FINDINGS

In this update, recent advances focused on donor selection, reduced toxicity preparation for HCT, and treatment of young adults will be presented. The current status of conventional bone marrow transplantation with a human leukocyte antigen-identical sibling donor is summarized.

SUMMARY

HCT for SCD is curative in almost all children who have a human leukocyte antigen-matched sibling donor. The future of this therapy will hinge on expanding the number of individuals who might be treated.

Indications and Results of HLA-Identical Sibling Hematopoietic Cell Transplantation for Sickle Cell Disease

Although a number of published trials exist of HLA-identical sibling hematopoietic cell transplantation (HCT) for sickle cell disease (SCD) that span 2 decades, when and for whom this therapy should be pursued is a subject of debate. Assessments of the risks of transplant-related complications that include infertility and debilitating graft-versus-host disease and long-term quality of life after successful HCT are difficult to perform without prospective trials in transplant and nontransplant cohorts. However, it is possible to assess the risk of mortality and to compare published rates of survival in individuals with SCD treated and not treated by HCT. In this brief review, projections about mortality risk based on recent published reports are reviewed and summarized. The published data show overall survival and event-free survival rates of 95% and 92%, respectively, in children treated by HLA-identical sibling HCT. The overall survival rates in the Center for International Blood and Marrow Transplant Research (N = 412) and European Blood and Marrow Transplant (N = 487) registries were 91% and 95%, respectively. These results provide broad support for the therapeutic value of HLA-identical sibling HCT for children with SCD and serve as the basis for a strong recommendation in favor of the option of HCT when a suitable donor is available. The experience of HLA-identical sibling HCT in adults with SCD is limited but appears to be similar to results in children. These preliminary observations, however, warrant further investigation.

Current and future alternative therapies for beta-thalassemia major

Beta-thalassemia is a group of frequent genetic disorders resulting in the synthesis of little or no β-globin chains. Novel approaches are being developed to correct the resulting α/β-globin chain imbalance, in an effort to move beyond the palliative management of this disease and the complications of its treatment (e.g. life-long red blood cell transfusion, iron chelation, splenectomy), which impose high costs on healthcare systems. Three approaches are envisaged: fetal globin gene reactivation by pharmacological compounds injected into patients throughout their lives, allogeneic hematopoietic stem cell transplantation (HSCT), and gene therapy. HSCT is currently the only treatment shown to provide an effective, definitive cure for β-thalassemia. However, this procedure remains risky and histocompatible donors are identified for only a small fraction of patients. New pharmacological compounds are being tested, but none has yet made it into common clinical practice for the treatment of beta-thalassemia major. Gene therapy is in the experimental phase. It is emerging as a powerful approach without the immunological complications of HSCT, but with other possible drawbacks. Rapid progress is being made in this field, and long-term efficacy and safety studies are underway.

Alternative donor allogeneic hematopoietic cell transplantation for hemoglobinopathies

Allogeneic hematopoietic stem cell transplantation (HSCT) offers a curative therapy for patients with hemoglobinopathies, mainly severe sickle cell disease (SCD) and thalassemia (TM). However, the applicability of HSCT has been limited mainly by donor availability, with a less than 25%-30% of eligible patients having human leukocyte antigen (HLA)-matched sibling donors. Previous outcomes using alternate donor options have been markedly inferior due to increased regimen-related toxicity, transplant-related mortality, graft failure, and graft-versus-host disease (GVHD). Advances in transplant technology, including high-resolution HLA typing, improved GVHD prophylactic approaches with tolerance induction, and better supportive care over the last decade, are addressing these historical challenges, resulting in increasing donor options. Herein, we review alternate donor HSCT approaches for severe SCD and TM using unrelated donors, umbilical cord blood units, or related haploidentical donors. Though this is an emerging field, early results are promising and in selected patients, this may be the preferred option to mitigate against the age-related morbidity and early mortality associated with these disorders.

Genetic treatment of a molecular disorder: gene therapy approaches to sickle cell disease

Effective medical management for sickle cell disease (SCD) remains elusive. As a prevalent and severe monogenic disorder, SCD has been long considered a logical candidate for gene therapy. Significant progress has been made in moving toward this goal. These efforts have provided substantial insight into the natural regulation of the globin genes and illuminated challenges for genetic manipulation of the hematopoietic system. The initial γ-retroviral vectors, next-generation lentiviral vectors, and novel genome engineering and gene regulation approaches each share the goal of preventing erythrocyte sickling. After years of preclinical studies, several clinical trials for SCD gene therapies are now open. This review focuses on progress made toward achieving gene therapy, the current state of the field, consideration of factors that may determine clinical success, and prospects for future development.

Successful matched sibling donor marrow transplantation following reduced intensity conditioning in children with hemoglobinopathies

Fifty-two children with symptomatic sickle cell disease sickle cell disease (SCD) (N = 43) or transfusion-dependent thalassemia (N = 9) received matched sibling donor marrow (46), marrow and cord product (5), or cord blood (1) allografts following reduced intensity conditioning (RIC) with alemtuzumab, fludarabine, and melphalan between March 2003 and May 2014*. The Kaplan-Meier probabilities of overall and event-free survival at a median of 3.42 (range, 0.75-11.83) years were 94.2% and 92.3% for the group, 93% and 90.7% for SCD, and 100% and 100% for thalassemia, respectively. Treatment-related mortality (all related to graft versus host disease, GVHD) was noted in three (5.7%) recipients, all 17-18 years of age. Acute and chronic GVHD was noted in 23% and 13%, respectively, with 81% of recipients off immunosuppression by 1 year. Graft rejection was limited to the single umbilical cord blood recipient who had prompt autologous hematopoietic recovery. Fourteen (27%) had mixed chimerism at 1 year and beyond; all had discontinued immunosuppression between 4 and 12 months from transplant with no subsequent consequence on GVHD or rejection. Infectious complications included predominantly bacteremia (48% were staphylococcus) and CMV reactivation (43%) necessitating preemptive therapy. Lymphocyte recovery beyond 6 months was associated with subsidence of infectious complications. All patients who engrafted were transfusion independent; no strokes or pulmonary complications of SCD were noted, and pain symptoms subsided within 6 months posttransplant. These findings support using RIC for patients with hemoglobinopathy undergoing matched sibling marrow transplantation (*www.Clinical Trials.gov: NCT00920972, NCT01050855, NCT02435901).

A complicated disease: what can be done to manage thalassemia major more effectively?

Patients with thalassemia major suffer from many complications, but in the last two decades their lives have improved both in length and quality. We report herein the most common complications and the recent advances that have changed the course of this disease. Also, we report in detail some of the new therapeutic strategies already introduced in practice and briefly some that are still being developed.

2015 Clinical trials update in sickle cell anemia

Polymerization of HbS and cell sickling are the prime pathophysiological events in sickle cell disease (SCD). Over the last 30 years, a substantial understanding at the molecular level has been acquired on how a single amino acid change in the structure of the beta chain of hemoglobin leads to the explosive growth of the HbS polymer and the associated changes in red cell morphology. O2 tension and intracellular HbS concentration are the primary molecular drivers of this process, and are obvious targets for developing new therapies. However, polymerization and sickling are driving a complex network of associated cellular changes inside and outside of the erythrocyte, which become essential components of the inflammatory vasculopathy and result in a large range of potential acute and chronic organ damages. In these areas, a multitude of new targets for therapeutic developments have emerged, with several ongoing or planned new therapeutic interventions. This review outlines the key points of SCD pathophysiology as they relate to the development of new therapies, both at the pre-clinical and clinical levels.

Is ABO mismatch another risk factor for allogeneic hematopoietic stem cell transplantation in pediatric thalassemic patients?

The ABO incompatibility between donor and recipient is not considered a barrier to successful allogeneic HSCT. Nevertheless, conflicting data still exist about the influence of ABO incompatibility on transplant outcome in pediatric patients with thalassemia. Fifty-one children with beta-thalassemia major who underwent allogeneic HSCT were enrolled this study. Twenty-three of them (45%) received an ABO-incompatible transplant [minor ABO mismatch: six (26%), major ABO mismatch: fourteen (61%), and bidirectional mismatch: three (13%)]. In this study, ABO incompatibility did not significantly impair GVHD, VOD, neutrophil and platelet engraftment, TRM, OS and TFS. Particularly in major and bidirectional ABO-mismatched patients, a delayed erythroid recovery was recorded as compared to the group receiving an ABO-compatible graft (median time, 31 and 38 days vs. 19.5 days; p: 0.02 and p: 0.03). Median time to red cell transfusion independence was significantly longer in major ABO-incompatible patients (median time, 87 days vs. 32 days; p: 0.001). Therefore, whenever feasible, major ABO-mismatched donors should be avoided in HSCT recipients, to prevent delayed erythroid recovery with prolonged RBC transfusion needs and impaired quality of life.

Alloimmunization is associated with older age of transfused red blood cells in sickle cell disease

Red blood cell (RBC) alloimmunization is a significant clinical complication of sickle cell disease (SCD). It can lead to difficulty with cross-matching for future transfusions and may sometimes trigger life-threatening delayed hemolytic transfusion reactions. We conducted a retrospective study to explore the association of clinical complications and age of RBC with alloimmunization in patients with SCD followed at a single institution from 2005 to 2012. One hundred and sixty six patients with a total of 488 RBC transfusions were evaluated. Nineteen patients (11%) developed new alloantibodies following blood transfusions during the period of review. The median age of RBC units was 20 days (interquartile range: 14-27 days). RBC antibody formation was significantly associated with the age of RBC units (P = 0.002), with a hazard ratio of 3.5 (95% CI: 1.71-7.11) for a RBC unit that was 7 days old and 9.8 (95% CI: 2.66-35.97) for a unit that was 35 days old, 28 days after the blood transfusion. No association was observed between RBC alloimmunization and acute vaso-occlusive complications. Although increased echocardiography-derived tricuspid regurgitant jet velocity (TRV) was associated with the presence of RBC alloantibodies (P = 0.02), TRV was not significantly associated with alloimmunization when adjusted for patient age and number of transfused RBC units. Our study suggests that RBC antibody formation is significantly associated with older age of RBCs at the time of transfusion. Prospective studies in patients with SCD are required to confirm this finding.

Allogeneic donor availability for hematopoietic stem cell transplantation in children with sickle cell disease

Hematopoietic stem cell transplant is curative of sickle cell disease (SCD) but limited by donor availability. Searches for 85 patients with SCD without matched sibling donors from 2009-2013 using modern techniques (allele-level HLA matching for unrelated donors and higher total nucleated cell doses for umbilical cord blood (UCB)) showed potential match probabilities of 20% for 8/8 HLA-matched unrelated donors, 84% for 7/8 donors, and 97% for two 4-6/6 UCBs suitable for ex-vivo expanded/double cord transplant. Searches performed by age 43 months would have a 90% chance of finding a suitable 5-6/6 UCB.

Perspectives in Genetics and Sickle Cell Disease Prevention in Africa: Beyond the Preliminary Data from Cameroon

Management of sickle cell disease (SCD) in Africa needs to be accompanied by various preventive strategies, including early detection via prenatal genetic diagnosis (PND). Contrary to Cameroonian doctors who considered termination of an affected pregnancy (TAP) for SCD in 36.1%, the majority of parents (62.5%) with affected children accepted TAP in principle. In practice, most women opted for TAP (90%), justified by a huge psycho-social burden. The ethical and legal challenges of PND prompted the need to explore the use of genetics for secondary prevention of SCD. In 610 Cameroonian SCD patients, the genomic variations in two principal foetal haemoglobin-promoting loci were significantly associated with foetal haemoglobin levels. In addition, the co-inheritance of a 3.7-kb α-globin gene deletion and SCD was associated with a late disease onset and possibly improved survival: there was a much higher allele frequency of the 3.7-kb α-globin gene deletion in SCD patients (∼ 40%) than in haemoglobin AA controls (∼ 10%). The data indicate the urgent need to develop and implement policy actions in sub-Saharan Africa on at least four levels: (1) the implementation of SCD screening practices and early neonatal follow-up; (2) the development and incorporating of socio-economic support to alleviate the burden of SCD on affected families; (3) the exploration of the appropriateness of the medical abortion laws for SCD, and (4) the development of national plans for genetic medicine, including research on genomic variants that affect the phenotypes of SCD, in order to potentially use them for anticipatory guidance.

Anemia: progress in molecular mechanisms and therapies

Anemia is a major source of morbidity and mortality worldwide. Here we review recent insights into how red blood cells (RBCs) are produced, the pathogenic mechanisms underlying various forms of anemia, and novel therapies derived from these findings. It is likely that these new insights, mainly arising from basic scientific studies, will contribute immensely to both the understanding of frequently debilitating forms of anemia and the ability to treat affected patients. Major worldwide diseases that are likely to benefit from new advances include the hemoglobinopathies (β-thalassemia and sickle cell disease); rare genetic disorders of RBC production; and anemias associated with chronic kidney disease, inflammation, and cancer. Promising new approaches to treatment include drugs that target recently defined pathways in RBC production, iron metabolism, and fetal globin-family gene expression, as well as gene therapies that use improved viral vectors and newly developed genome editing technologies.

Hematopoietic stem cell transplantation in thalassemia major and sickle cell disease: indications and management recommendations from an international expert panel

Thalassemia major and sickle cell disease are the two most widely disseminated hereditary hemoglobinopathies in the world. The outlook for affected individuals has improved in recent years due to advances in medical management in the prevention and treatment of complications. However, hematopoietic stem cell transplantation is still the only available curative option. The use of hematopoietic stem cell transplantation has been increasing, and outcomes today have substantially improved compared with the past three decades. Current experience world-wide is that more than 90% of patients now survive hematopoietic stem cell transplantation and disease-free survival is around 80%. However, only a few controlled trials have been reported, and decisions on patient selection for hematopoietic stem cell transplantation and transplant management remain principally dependent on data from retrospective analyses and on the clinical experience of the transplant centers. This consensus document from the European Blood and Marrow Transplantation Inborn Error Working Party and the Paediatric Diseases Working Party aims to report new data and provide consensus-based recommendations on indications for hematopoietic stem cell transplantation and transplant management.

Guidelines for the Standard Monitoring of Patients With Thalassemia: Report of the Thalassemia Longitudinal Cohort

Chronic transfusion therapy has played a central role in extending life expectancy for patients with hemoglobinopathies such as thalassemia. However, this life-saving therapy is associated with numerous complications that now comprise the bulk of management considerations for patients with thalassemia. This review reports on the experience of the Thalassemia Longitudinal Cohort and reviews available literature to establish guidelines for the management of patients with thalassemia.

Treosulfan-based conditioning regimen for allogeneic haematopoietic stem cell transplantation in children with sickle cell disease

Although allogeneic haematopoietic stem cell transplantation (HSCT) still represents the only consolidated possibility of cure for sickle cell disease (SCD) patients, its use has been limited by the risk of morbidity and mortality associated with conventional myeloablative therapy. The introduction of treosulfan to replace busulfan in conditioning regimens has recently been explored by virtue of its lower toxicity profile. We report our experience with a treosulfan/thiotepa/fludarabine conditioning for human leucocyte antigen (HLA)-matched sibling or unrelated donor-HSCT in 15 children with SCD, and compare patient outcomes with those of a historical cohort (15 patients) given a busulfan-based regimen. Engraftment was achieved in 28 out of 30 patients (93%), with one case of graft failure in either group. The conditioning regimen was well tolerated in both groups, with no cases of grade III-IV regimen-related toxicity. The 7-year overall survival (OS) and disease-free survival (DFS) for the whole cohort were 100% and 93%, respectively, with a 93% DFS in both busulfan and treosulfan groups. No SCD-related adverse events occurred after engraftment in patients with complete or mixed donor chimerism. This retrospective analysis suggests that a treosulfan-based conditioning regimen is able to ensure engraftment with excellent OS/DFS and low regimen-related toxicity in patients with SCD.

Indications for allo- and auto-SCT for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2015

This is the sixth special report that the European Society for Blood and Marrow Transplantation regularly publishes on the current practice and indications for haematopoietic SCT for haematological diseases, solid tumours and immune disorders in Europe. Major changes have occurred in the field of haematopoietic SCT over the last years. Cord blood units as well as haploidentical donors have been increasingly used as stem cell sources for allo-SCT, thus, augmenting the possibility of finding a suitable donor for a patient. Continuous refinement of conditioning strategies has also expanded not only the number of potential indications but also has permitted consideration of older patients or those with co-morbidity for a transplant. There is accumulating evidence of the role of haematopoietic SCT in non-haematological disorders such as autoimmune diseases. On the other hand, the advent of new drugs and very effective targeted therapy has challenged the role of SCT in some instances or at least, modified its position in the treatment armamentarium of a given patient. An updated report with revised tables and operating definitions is presented.

Cord blood clinical processing, cryopreservation, and storage

Allogeneic umbilical cord blood (UCB) hematopoietic stem cell transplantation has become a crucial advancement in the treatment for a variety of diseases including hematopoietic and non-hematopoietic malignancies, BM failure syndromes, hemoglobinopathies, and metabolic and immunodeficiency disorders. It has been well documented that the success of UCB engraftment is tied to UCB banking processes, and now there are established guidelines for standardization of collection, banking, processing, and cryopreservation for unrelated UCB units with purpose of achieving consistent production of high quality placental and UCB units for administration. In 2011, Canada's Ministry of Health has announced Canada's first national, publicly funded umbilical cord blood bank, which aims to provide altruistic donations for unrelated allogeneic hematopoietic stem cell transplant. In this chapter, we describe specific protocols for clinical processing, cryopreservation, and storage of UCB used by the Canadian Blood Services National Public Umbilical Cord Blood Bank.

Smoothing the crescent curve: sickle cell disease

Sickle cell disease (SCD) is an inherited disorder secondary to a point mutation at the sixth position of the beta chain of human hemoglobin that results in the replacement of valine for glutamic acid. This recessive genetic abnormality precipitates the polymerization of the deoxygenated form of hemoglobin S that induces a major distortion of red blood cells (sickle red blood cells), which decreases sickle red blood cell deformability, leading to chronic hemolysis and vasoocclusion. These processes can result in severe complications, including chronic pain, end organ dysfunction, stroke, and early mortality. The only proven curative therapy for patients with SCD is myeloablative conditioning and allogeneic stem cell transplantation from HLA-matched sibling donors. In this review, we discuss the most recent advances in allogeneic stem cell transplantation in SCD, including more novel approaches such as reduced toxicity conditioning and the use of alternative allogeneic donors (matched unrelated donors, umbilical cord blood transplantation, haploidentical donors) and autologous gene correction stem cell strategies. Prospects are bright for new stem cell approaches for patients with SCD that will enable curative stem and genetic correction therapies for a greater number of patients suffering from this chronic and debilitating condition.

Autoimmune thyroid disease following alemtuzumab therapy and hematopoietic cell transplantation in pediatric patients with sickle cell disease

Allogenic hematopoietic cell transplantation (alloHCT) is currently the only curative treatment option for patients with sickle cell disease. Alemtuzumab is a monoclonal antibody directed against CD52 positive cells used in myeloablative conditioning regimens for alloHCT. Its use has been associated with development of autoimmune disease in adult patients with rheumatologic conditions. We report on three cases of new onset autoimmune thyroid disease after alloHCT treatment with alemtuzumab in pediatric patients with sickle cell disease.

A reduced-toxicity regimen is associated with durable engraftment and clinical cure of nonmalignant genetic diseases among children undergoing blood and marrow transplantation with an HLA-matched related donor

Blood and marrow transplantation (BMT) is a standard curative therapy for patients with nonmalignant genetic diseases. Myeloablative conditioning has been associated with significant regimen-related toxicity (RRT), whereas reduced-intensity conditioning regimens have been associated with graft failure. In this prospective pilot trial conducted at 2 centers between 2006 and 2013, we report the outcome of 22 patients with nonmalignant genetic diseases who were conditioned with a novel reduced-toxicity regimen: i.v. busulfan (16 mg/kg), alemtuzumab (52 mg/m(2)), fludarabine (140 mg/m(2)), and cyclophosphamide (105 mg/kg). The median age of the study population was 3.5 years (range, 5 months to 26 years). No cases of sinusoidal obstruction syndrome, severe or chronic graft-versus-host disease (GVHD), or primary graft failure were reported. Median time to neutrophil engraftment (>500 cells/μL) and platelet engraftment (>20K cells/μL) were 19 (range, 12 to 50) and 23.5 (range, 14 to 134) days, respectively. The median length of follow-up was 3 years (range, .2 to 6.3). The overall survival rates were 95% at 100 days (95% confidence interval, .72 to .99) and 90% at 6 years (95% confidence interval, .68 to .98). RRT and chronic GVHD are significant barriers to BMT for patients with nonmalignant genetic diseases. This alemtuzumab-based reduced-toxicity regimen appears to be promising with durable engraftment, effective cure of clinical disease, low rates of RRT, and no observed chronic GVHD.

Hematopoietic stem cell transplantation for sickle cell disease: state of the science

Sickle cell disease (SCD) is an inherited disorder secondary to a point mutation at the sixth position of the beta chain of human hemoglobin resulting in the replacement of valine for glutamic acid. This recessive genetic abnormality precipitates the polymerization of the deoxygenated form of hemoglobin S inducing a major distortion of red blood cells (S-RBC), which decreases S-RBC deformability leading to chronic hemolysis and vaso-occlusion. These processes can result in severe complications including chronic pain, end-organ dysfunction, stroke, and early mortality. The only proven curative therapy for patients with SCD is myeloablative conditioning and allogeneic stem cell transplantation from HLA-matched sibling donors. In this review, we discuss the most recent advances in allogeneic stem cell transplantation in patients with SCD including more novel approaches such as reduced toxicity conditioning and the use of alternative allogeneic donors, including matched unrelated donors (MUDs), unrelated cord blood donors (UCBT), and familial haploidentical (FHI) donors. The results to date are very encouraging regarding allogeneic stem cell transplantation for patients with SCD including high survival rates and enabling a greater number of patients suffering from this chronic and debilitating condition to receive curative allogeneic stem cell therapies. However, we still have several areas to investigate and barriers to overcome to successfully cure the majority of patients with severe SCD through allogeneic stem cell therapies.

Hematopoietic stem cell transplantation for patients with sickle cell disease: progress and future directions

Research has solidified matched sibling marrow, cord blood, or mobilized peripheral blood as the best source for allogeneic hematopoietic stem cell transplantation for patients with sickle cell disease, with low graft rejection and graft-versus-host disease (GVHD) and high disease-free survival rates. Fully allelic matched unrelated donor is an option for transplant-eligible patients without HLA-matched sibling donors. Unrelated cord transplant studies reported high GVHD and low engraftment rates. Haploidentical transplants have less GVHD, but improvements are needed to increase the low engraftment rate. The decision to use unrelated cord blood units or haploidentical donors depends on institutional expertise.