Transplantation for thalassemia major: alternative donors

Ex vivo culture resting time impacts transplantation outcomes of genome-edited human hematopoietic stem and progenitor cells in xenograft mouse models

Ex vivo resting culture is a standard procedure following genome editing in hematopoietic stem and progenitor cells (HSPCs). However, prolonged culture may critically affect cell viability and stem cell function. We investigated whether varying durations of culture resting times impact the engraftment efficiency of human CD34+ HSPCs edited at the BCL11A enhancer, a key regulator in the expression of fetal hemoglobin. We employed electroporation to introduce CRISPR-Cas9 components for BCL11A enhancer editing and compared outcomes with nonelectroporated (NEP) and electroporated-only (EP) control groups. Post-electroporation, we monitored cell viability, death rates, and the frequency of enriched hematopoietic stem cell (HSC) fractions (CD34+CD90+CD45RA- cells) over a 48-hour period. Our findings reveal that while the NEP group showed an increase in cell numbers 24 hours post-electroporation, both EP and BCL11A-edited groups experienced significant cell loss. Although CD34+ cell frequency remained high in all groups for up to 48 hours post-electroporation, the frequency of the HSC-enriched fraction was significantly lower in the EP and edited groups compared to the NEP group. In NBSGW xenograft mouse models, both conditioned with busulfan and nonconditioned, we found that immediate transplantation post-electroporation led to enhanced engraftment without compromising editing efficiency. Human glycophorin A+ (GPA+) red blood cells (RBCs) sorted from bone marrow of all BCL11A edited mice exhibited similar levels of γ-globin expression, regardless of infusion time. Our findings underscore the critical importance of optimizing the culture duration between genome editing and transplantation. Minimizing this interval may significantly enhance engraftment success and minimize cell loss without compromising editing efficiency. These insights offer a pathway to improve the success rates of genome editing in HSPCs, particularly for conditions like sickle cell disease.

Hematopoietic stem cell transplantation for B-thalassemia major with alemtuzumab

While matched related donor (MRD) allogeneic hematopoietic stem cell transplantation (HSCT) is a curative option for transfusion-dependent beta-thalassemia (TDT), the use of alternative sources has increased, resulting in the exploration of novel transplant-conditioning regimens to reduce the contribution of graft-versus-host disease (GVHD) and graft failure (GF) to transplant-related morbidity and mortality. Alemtuzumab is a CD52 monoclonal antibody that has been successfully incorporated into myeloablative conditioning regimens for other hematologic conditions, yet there have been limited studies regarding the use of alemtuzumab in HSCT for TDT. The purpose of this study was to evaluate engraftment, incidence of GVHD, and transplant related morbidity and mortality in patients with TDT who received alemtuzumab in addition to standard busulfan-based conditioning. The primary endpoint was severe GVHD-free, event-free survival (GEFS). Our cohort included 24 patients with a median age of 6.8 years (range 1.5-14.9). Eleven patients received a 10/10 MRD HSCT, eleven 10/10 unrelated donor (UD), and two mismatched UD. All patients achieved primary engraftment. For all patients, 5-year GEFS was 77.4% and 5-year overall survival (OS) was 91%. The 5-year cumulative incidence of GF (attributed to poor graft function) without loss of donor chimerism was 13.8% (95% CI: 4.5, 35.3). We report low rates of significant acute GVHD grade II-IV (12.5%) and chronic GVHD (4.4%). Younger age and MRD were associated with significantly improved GEFS, OS and EFS. Our results show that the use of alemtuzumab promotes stable engraftment, may reduce rates of severe GVHD, and results in acceptable GEFS, OS, and EFS.

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).

Gene Editing in Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) can be isolated and collected from the body, genetically modified, and expanded ex vivo. The invention of innovative and powerful gene editing tools has provided researchers with great convenience in genetically modifying a wide range of cells, including hematopoietic stem and progenitor cells (HSPCs). In addition to being used to modify genes to study the functional role that specific genes play in the hematopoietic system, the application of gene editing platforms in HSCs is largely focused on the development of cell-based gene editing therapies to treat diseases such as immune deficiency disorders and inherited blood disorders. Here, we review the application of gene editing tools in HSPCs. In particular, we provide a broad overview of the development of gene editing tools, multiple strategies for the application of gene editing tools in HSPCs, and exciting clinical advances in HSPC gene editing therapies. We also outline the various challenges integral to clinical translation of HSPC gene editing and provide the possible corresponding solutions.

Clinical trials and promising preclinical applications of CRISPR/Cas gene editing

Treatment of genetic disorders by genomic manipulation has been the unreachable goal of researchers for many decades. Although our understanding of the genetic basis of genetic diseases has advanced tremendously in the last few decades, the tools developed for genomic editing were not efficient and practical for their use in the clinical setting until now. The recent advancements in the research of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated protein (Cas) systems offered an easy and efficient way to edit the genome and accelerated the research on their potential use in the treatment of genetic disorders. In this review, we summarize the clinical trials that evaluate the CRISPR/Cas systems for treating different genetic diseases and highlight promising preclinical research on CRISPR/Cas mediated treatment of a great diversity of genetic disorders. Ultimately, we discuss the future of CRISPR/Cas mediated genome editing in genetic diseases.

Decision-making about gene therapy in transfusion dependent thalassemia

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is a treatment option with curative intent for patients with transfusion dependent thalassemia (TDT) but its application is limited by the lack of suitable donors and acceptability due to the related morbidity/mortality. Transplantation of autologous genetically modified hematopoietic cells, gene therapy (GT) is emerging as a promising treatment option for TDT as it eliminates graft versus host disease (GVHD) and need for immunosuppression. Early results of GT suggest that many, but not all patients achieve transfusion independence after the procedure. There is little information about the acceptability of GT in patients with TDT. We sought to examine patient/family knowledge about GT in TDT and to examine factors that influence decision-making about this therapy.

METHODS

Parents of children with TDT and adults with TDT were who provided informed consent underwent semi-structured interviews to understand patient/family knowledge and decision-making regarding GT in TDT. Transcribed interviews were coded and the data was examined for emerging themes using a combination of thematic and content analysis.

RESULTS

Twenty-five study participants with mean age of 38Y (17-52Y) including eight adults living with TDT, and 17 parents of children with TDT underwent semi-structured qualitative interviews. Participant responses coalesced around broad themes related to knowledge of GT, motivating/deterring factors and outcomes. Study participants expressed a desire for 'cure' from thalassemia including transfusion independence, chelation reduction and improved quality of life as motivators for considering GT. Insufficient knowledge about the process, long-term outcomes, safety, and side effects as well as the potential for death/failure of the procedure were deterrents for the consideration GT. Reduction in frequency of transfusions, even without elimination of transfusions was an acceptable outcome of GT for most participants. Participant choice for preferred treatment modality was split between indefinitely continuing transfusions which was familiar to them versus GT which was unfamiliar, and with an uncertain outcome. None of the participants had a matched sibling donor; alternate donor HSCT was the least preferred option in this group.

CONCLUSION

There is tempered excitement about GT in patients/families with TDT with a general willingness to accept transfusions reduction as the outcome.

Genetic correction of concurrent α- and β-thalassemia patient-derived pluripotent stem cells by the CRISPR-Cas9 technology

BACKGROUND

Thalassemia is a genetic blood disorder characterized by decreased hemoglobin production. Severe anemia can damage organs and severe threat to life safety. Allogeneic transplantation of bone marrow-derived hematopoietic stem cell (HSCs) at present represents a promising therapeutic approach for thalassemia. However, immune rejection and lack of HLA-matched donors limited its clinical application. In recent years, human-induced pluripotent stem cells (hiPSCs) technology offers prospects for autologous cell-based therapy since it could avoid the immunological problems mentioned above.

METHODS

In the present study, we established a new hiPSCs line derived from amniotic cells of a fetus with a homozygous β41-42 (TCTT) deletion mutation in the HBB gene and a heterozygous Westmead mutation (C > G) in the HBA2 gene. We designed a CRISPR-Cas9 to target these casual mutations and corrected them. Gene-corrected off-target analysis was performed by whole-exome capture sequencing. The corrected hiPSCs were analyzed by teratoma formation and erythroblasts differentiation assays.

RESULTS

These mutations were corrected with linearized donor DNA through CRISPR/Cas9-mediated homology-directed repair. Corrections of hiPSCs were validated by sequences. The corrected hiPSCs retain normal pluripotency. Moreover, they could be differentiated into hematopoietic progenitors, which proves that they maintain the multilineage differentiation potential.

CONCLUSIONS

We designed sgRNAs and demonstrated that these sgRNAs facilitating the CRISPR-Cas9 genomic editing system could be applied to correct concurrent α- and β-thalassemia in patient-derived hiPSCs. In the future, these corrected hiPSCs can be applied for autologous transplantation in patients with concurrent α- and β-thalassemia.

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.

Hematopoietic stem cell transplantation for thalassemia major using HLA fully-matched and mismatched donor grafts

BACKGROUND

Until now, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only effective method to cure Thalassemia major. However, it has not been determined whether similar results can be obtained with the same conditioning regimen for both fully-matched and mismatched donors grafts. We hypothesized that using modified NF-08-TM conditioning regimen could achieve similar results for both fully and mismatched donors grafts.

METHODS

This retrospective cohort study included patients with β-thalassemia major who underwent HSCT with modified NF-08-TM conditioning regimen at Guangzhou Women and Children's Medical Centre between January 2013 and January 2019.

RESULTS

Among the 257 patients (172 males) included in this study, 3 had two transplantations. Totally 193 and 67 had fully-matched and mismatched donors were examined, respectively. The median follow-up was 29 months; 6-year overall survival (OS), thalassemia-free survival (TFS), graft rejection (GR) and transplantation-related mortality (TRM) were 92.08%, 90.89%, 1.24% and 8.01%, respectively. Multivariate analysis showed that human leukocyte antigen (HLA) compatibility between patient and donor was not independently associated with OS, TFS, GR or TRM. Mismatched donor graft transplantation for β-thalassemia major is associated with similar survival outcomes and incidences of complications (except for acute GVHD) to fully-matched donor graft transplantation based on modified NF-08-TM conditioning regimen.

CONCLUSIONS

In conclusion, based on the modified NF-08-TM regimen, certain mismatched donor transplantations for thalassemia major patients could achieve similar results as fully-matched donor transplantations.

Genome editing approaches to β-hemoglobinopathies

β-hemoglobinopathies are the most common monogenic disorders worldwide and are caused by mutations in the β-globin locus altering the production of adult hemoglobin (HbA). Transplantation of autologous hematopoietic stem cells (HSCs) corrected by lentiviral vector-mediated addition of a functional β-like globin raised new hopes to treat sickle cell disease and β-thalassemia patients; however, the low expression of the therapeutic gene per vector copy is often not sufficient to fully correct the patients with a severe clinical phenotype. Recent advances in the genome editing field brought new possibilities to cure β-hemoglobinopathies by allowing the direct modification of specific endogenous loci. Double-strand breaks (DSBs)-inducing nucleases (i.e., ZFNs, TALENs and CRISPR-Cas9) or DSB-free tools (i.e., base and prime editing) have been used to directly correct the disease-causing mutations, restoring HbA expression, or to reactivate the expression of the fetal hemoglobin (HbF), which is known to alleviate clinical symptoms of β-hemoglobinopathy patients. Here, we describe the different genome editing tools, their application to develop therapeutic approaches to β-hemoglobinopathies and ongoing clinical trials using genome editing strategies.

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.

Genome Editing for β-Hemoglobinopathies: Advances and Challenges

β-hemoglobinopathies are the most common genetic disorders worldwide and are caused by mutations affecting the production or the structure of adult hemoglobin. Patients affected by these diseases suffer from anemia, impaired oxygen delivery to tissues, and multi-organ damage. In the absence of a compatible donor for allogeneic bone marrow transplantation, the lifelong therapeutic options are symptomatic care, red blood cell transfusions and pharmacological treatments. The last decades of research established lentiviral-mediated gene therapy as an efficacious therapeutic strategy. However, this approach is highly expensive and associated with a variable outcome depending on the effectiveness of the viral vector and the quality of the cell product. In the last years, genome editing emerged as a valuable tool for the development of curative strategies for β-hemoglobinopathies. Moreover, due to the wide range of its applications, genome editing has been extensively used to study regulatory mechanisms underlying globin gene regulation allowing the identification of novel genetic and pharmacological targets. In this work, we review the current advances and challenges of genome editing approaches to β-hemoglobinopathies. Special focus has been directed towards strategies aimed at correcting the defective β-globin gene or at inducing fetal hemoglobin (HbF), which are in an advanced state of clinical development.

Base and Prime Editing Technologies for Blood Disorders

Nuclease-based genome editing strategies hold great promise for the treatment of blood disorders. However, a major drawback of these approaches is the generation of potentially harmful double strand breaks (DSBs). Base editing is a CRISPR-Cas9-based genome editing technology that allows the introduction of point mutations in the DNA without generating DSBs. Two major classes of base editors have been developed: cytidine base editors or CBEs allowing C>T conversions and adenine base editors or ABEs allowing A>G conversions. The scope of base editing tools has been extensively broadened, allowing higher efficiency, specificity, accessibility to previously inaccessible genetic loci and multiplexing, while maintaining a low rate of Insertions and Deletions (InDels). Base editing is a promising therapeutic strategy for genetic diseases caused by point mutations, such as many blood disorders and might be more effective than approaches based on homology-directed repair, which is moderately efficient in hematopoietic stem cells, the target cell population of many gene therapy approaches. In this review, we describe the development and evolution of the base editing system and its potential to correct blood disorders. We also discuss challenges of base editing approaches-including the delivery of base editors and the off-target events-and the advantages and disadvantages of base editing compared to classical genome editing strategies. Finally, we summarize the recent technologies that have further expanded the potential to correct genetic mutations, such as the novel base editing system allowing base transversions and the more versatile prime editing strategy.

Ready for Repair? Gene Editing Enters the Clinic for the Treatment of Human Disease

We present an overview of clinical trials involving gene editing using clustered interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9), transcription activator-like effector nucleases (TALENs), or zinc finger nucleases (ZFNs) and discuss the underlying mechanisms. In cancer immunotherapy, gene editing is applied ex vivo in T cells, transgenic T cell receptor (tTCR)-T cells, or chimeric antigen receptor (CAR)-T cells to improve adoptive cell therapy for multiple cancer types. This involves knockouts of immune checkpoint regulators such as PD-1, components of the endogenous TCR and histocompatibility leukocyte antigen (HLA) complex to generate universal allogeneic CAR-T cells, and CD7 to prevent self-destruction in adoptive cell therapy. In cervix carcinoma caused by human papillomavirus (HPV), E6 and E7 genes are disrupted using topically applied gene editing machinery. In HIV infection, the CCR5 co-receptor is disrupted ex vivo to generate HIV-resistant T cells, CAR-T cells, or hematopoietic stem cells. In β-thalassemia and sickle cell disease, hematopoietic stem cells are engineered ex vivo to induce the production of fetal hemoglobin. AAV-mediated in vivo gene editing is applied to exploit the liver for systemic production of therapeutic proteins in hemophilia and mucopolysaccharidoses, and in the eye to restore splicing of the CEP920 gene in Leber's congenital amaurosis. Close consideration of safety aspects and education of stakeholders will be essential for a successful implementation of gene editing technology in the clinic.

Gene Therapy for Beta-Hemoglobinopathies: Milestones, New Therapies and Challenges

Inherited monogenic disorders such as beta-hemoglobinopathies (BH) are fitting candidates for treatment via gene therapy by gene transfer or gene editing. The reported safety and efficacy of lentiviral vectors in preclinical studies have led to the development of several clinical trials for the addition of a functional beta-globin gene. Across trials, dozens of transfusion-dependent patients with sickle cell disease (SCD) and transfusion-dependent beta-thalassemia (TDT) have been treated via gene therapy and have achieved reduced transfusion requirements. While overall results are encouraging, the outcomes appear to be strongly influenced by the level of lentiviral integration in transduced cells after engraftment, as well as the underlying genotype resulting in thalassemia. In addition, the method of procurement of hematopoietic stem cells can affect their quality and thus the outcome of gene therapy both in SCD and TDT. This suggests that new studies aimed at maximizing the number of corrected cells with long-term self-renewal potential are crucial to ensure successful treatment for every patient. Recent advancements in gene transfer and bone marrow transplantation have improved the success of this approach, and the results obtained by using these strategies demonstrated significant improvement of gene transfer outcome in patients. The advent of new gene-editing technologies has suggested additional therapeutic options. These are primarily focused on correcting the defective beta-globin gene or editing the expression of genes or genomic segments that regulate fetal hemoglobin synthesis. In this review, we aim to establish the potential benefits of gene therapy for BH, to summarize the status of the ongoing trials, and to discuss the possible improvement or direction for future treatments.

Unrelated Donor Transplantation in Children with Thalassemia using Reduced-Intensity Conditioning: The URTH Trial

Allogeneic hematopoietic stem cell transplantation (HSCT) can cure transfusion-dependent thalassemia (TDT). In a multicenter trial we investigated the efficacy of reduced-intensity conditioning (RIC) before unrelated donor (URD) HSCT in children with TDT. Thirty-three children, ages 1 to 17 years, received bone marrow (BM) or umbilical cord blood (UCB) allografts. Median time to neutrophil engraftment was 13 days (range, 10 to 25) and 24 days (range, 18 to 49) and platelet engraftment 23 days (range, 12 to 46) and 50 days (range, 31 to 234) after BM and UCB allografts, respectively. With a median follow-up of 58 months (range, 7 to 79), overall and thalassemia-free survival was 82% (95% CI, .64% to .92%) and 79% (95% CI, .6% to .9%), respectively. The cumulative incidence of grades II to IV acute graft-versus-host disease (GVHD) after BM and UCB allografts was 24% and 44%; the 2-year cumulative incidence of chronic extensive GVHD was 29% and 21%, respectively; 71% of BM and 91% of UCB recipients discontinued systemic immunosuppression by 2 years. Six patients who had Pesaro risk class 2 (n = 5) and class 3 (n = 1) died of GVHD (n = 3), viral pneumonitis (n = 2) and pulmonary hemorrhage (n = 1). Outcomes after this RIC compared favorably with URD HSCT outcomes for TDT and supported engraftment in 32 of 33 patients. Efforts to reduce GVHD and infectious complications are being pursued further.

Hemoglobin disorders: lentiviral gene therapy in the starting blocks to enter clinical practice

The β-hemoglobinopathies, transfusion-dependent β-thalassemia and sickle cell disease, are the most prevalent inherited disorders worldwide and affect millions of people. Many of these patients have a shortened life expectancy and suffer from severe morbidity despite supportive therapies, which impose an enormous financial burden to societies. The only available curative therapy is allogeneic hematopoietic stem cell transplantation, although most patients do not have an HLA-matched sibling donor, and those who do still risk life-threatening complications. Therefore, gene therapy by one-time ex vivo modification of hematopoietic stem cells followed by autologous engraftment is an attractive new therapeutic modality. The first proof-of-principle of conversion to transfusion independence by means of a lentiviral vector expressing a marked and anti-sickling β^T87Q-globin gene variant was reported a decade ago in a patient with transfusion-dependent β-thalassemia. In follow-up multicenter Phase II trials with an essentially identical vector (termed LentiGlobin BB305) and protocol, 12 of the 13 patients with a non-β⁰/β⁰ genotype, representing more than half of all transfusion-dependent β-thalassemia cases worldwide, stopped red blood cell transfusions with total hemoglobin levels in blood approaching normal values. Correction of biological markers of dyserythropoiesis was achieved in evaluated patients. In nine patients with β⁰/β⁰ transfusion-dependent β-thalassemia or equivalent severity (β^IVS1-110), median annualized transfusion volume decreased by 73% and red blood cell transfusions were stopped in three patients. Proof-of-principle of therapeutic efficacy in the first patient with sickle cell disease was also reported with LentiGlobin BB305. Encouraging results were presented in children with transfusion-dependent β-thalassemia in another trial with the GLOBE lentiviral vector and several other gene therapy trials are currently open for both transfusion-dependent β-thalassemia and sickle cell disease. Phase III trials are now under way and should help to determine benefit/risk/cost ratios to move gene therapy toward clinical practice.

New therapeutic targets in transfusion-dependent and -independent thalassemia

β-Thalassemias are characterized by reduced production of β-globin chain, resulting in α/β-chain unbalance and precipitation of α-globin-heme complexes and determining ineffective erythropoiesis. Ineffective erythropoiesis, chronic hemolytic anemia, and compensatory hematopoietic expansion are the disease hallmarks, and they are related to the severity of the chain unbalance. Several clinical forms of β-thalassemia, including the coinheritance of β-thalassemia with hemoglobin E resulting in hemoglobin E/β-thalassemia, have been described. Clinically, β-thalassemias can be classified as transfusion-dependent thalassemia (TDT) and non-transfusion-dependent thalassemia (NTDT) according to the severity of the phenotype, which is caused by a wide spectrum of mutations in a homozygous or compound heterozygous state. Current treatment of TDT consists of regular transfusions that lead to iron overload, requiring iron chelation to prevent iron-related organ toxicity. NTDT patients do not require transfusions or only occasionally require them; however, they develop iron overload as well because of increased intestinal iron absorption caused by chronic anemia. Hematopoietic stem cell allogenic transplant is the only approved cure for β-thalassemia; however, it is still limited by clinical conditions and the availability of matched donors as well as by potential graft-versus-host disease (GVHD). Gene therapy could avoid the GVHD risk, although hematopoietic stem cells must be genetically modified ex vivo. Epigenetic manipulation and genomic editing are novel experimental approaches. An increased understanding of the pathophysiology that controls the disease process prompted us to explore alternative therapeutic approaches that address the underlying chain unbalance, ineffective erythropoiesis, and iron dysregulation. Molecules, such as JAK2 inhibitors and the activin-receptor ligand trap that target ineffective erythropoiesis, are already in clinical trials with promising results. Other agents aimed to generate iron-restricted erythropoiesis are also under experimental evaluation.

Health-related Quality of Life and Associated Factors Among Thalassemia Major Patients, Southeast of Iran

Low quality of life (QOL) is a feature that has been overlooked in thalassemia major (TM) patients. Our aim was to assess QOL in school-aged TM patients in Zabol city and surrounding rural areas in southeast of Iran. The study was performed in 2014. QOL was evaluated using Pediatric Quality of Life Inventory 4 (PedsQL4) questionnaire addressing physical, emotional, social, and educational, along with psychological health in 80 TM patients. Also, 80 age-matched and sex-matched subjects without any chronic illness served as control group. Mean age of the patients was 11.7±4.1 years old. Total QOL scores was 51.4±13.3 in the patients. In comparison, mean value of total QOL score in controls was 91.1±3.3 (P<0.0001). Poor and moderate QOL were observed in 44.7% and 48.7% of the patients, respectively. Mean functioning scores for physical, emotional, social, educational, and psychological dimensions in the patients were 56.2±119, 69.6.4±23.3, 27.1±22.1, 52.3±18.1, and 48.9±11.8, respectively. The lowest level of QOL was related to the social field (81.3% with less than average score), while the highest QOL was related to the emotional aspect (58.8% with good QOL; >75 scores). Overall, female sex, poor compliance with chelation therapy, and residency in urban areas were significantly associated with poor QOL. In conclusion, providing a psychiatric health package seems to be essential for improving QOL in TM patients, especially in social field.

T Cell-Depleted and T Cell-Replete HLA-Haploidentical Stem Cell Transplantation for Non-malignant Disorders

PURPOSE OF REVIEW

Hematopoietic stem cell transplantation (HSCT) is a treatment option for children with malignant and non-malignant disorders as well as an expanding number of inherited disorders. However, only a limited portion of patients in the need of an allograft have an HLA-compatible, either related or unrelated, donor. Haploidentical HSCT is now considered a valid treatment option, especially in view of the recent insights in terms of graft manipulation. This review will offer an overview of clinical results obtained through the use of haploidentical HSCT in non-malignant diseases. We will analyze major advantages and drawbacks of both T cell depleted and unmanipulated HSCT, discussing future challenges for further improving patients' outcome.

RECENT FINDINGS

T cell depletion (TCD) aims to reduce the morbidity and mortality associated with graft-versus-host disease (GvHD). However, the delayed immune recovery and the risk of graft failure still remain potential problems. In the last years, the use of post-transplant cyclophosphamide has been shown to be an alternative effective strategy to prevent GvHD in recipients of haploidentical HSCT. Recent data suggest that both T cell depleted and T cell-replete haplo-HSCT are suitable options to treat children with several types of non-malignant disorders lacking an HLA-identical donor.

Investigational drugs in phase I and phase II clinical trials for thalassemia

INTRODUCTION

Regular transfusion and iron chelation are the current treatment of severe forms of thalassemia. As a consequence of this demanding supportive treatment, there are several unmet therapeutic needs. Due to a deeper understanding in the pathophysiology of thalassemia, new therapeutic strategies have been developed that are now in pre-clinical and clinical trials. Areas covered: Activin receptor ligand traps (luspatercept and sotatercept), drugs targeting ineffective erythropoiesis, showed encouraging results in Phase I and II clinical trials. A phase III clinical trial is currently ongoing. Ruxolitinib, a Jak2 inhibitor, has been tested to limit stress erythropoiesis in a phase II clinical trial. In addition, improvement in iron chelation has been developed. Moreover, several trials of gene therapy are currently active in different countries with different lentiviral vectors. Expert opinion: The most promising molecules are the activin receptor ligand traps. Together with gene therapy these could be an alternative to bone marrow transplant, aiming towards a curative strategy. The main limit to gene therapy seems to be the conditioning regimen, thus an in vivo gene therapy would be more suitable. At pre-clinical level gene editing is showing extremely encouraging results.