A comprehensive review of hydroxyurea for β-haemoglobinopathies: the role revisited during COVID-19 pandemic

The effect of red blood cell disorders on male fertility and reproductive health

Male infertility is defined as a failure to conceive after 12 months of unprotected intercourse owing to suspected male reproductive factors. Non-malignant red blood cell disorders are systemic conditions that have been associated with male infertility with varying severity and strength of evidence. Hereditary haemoglobinopathies and bone marrow failure syndromes have been associated with hypothalamic-pituitary-gonadal axis dysfunction, hypogonadism, and abnormal sperm parameters. Bone marrow transplantation is a potential cure for these conditions, but exposes patients to potentially gonadotoxic chemotherapy and/or radiation that could further impair fertility. Iron imbalance might also reduce male fertility. Thus, disorders of hereditary iron overload can cause iron deposition in tissues that might result in hypogonadism and impaired spermatogenesis, whereas severe iron deficiency can propagate anaemias that decrease gonadotropin release and sperm counts. Reproductive urologists should be included in the comprehensive care of patients with red blood cell disorders, especially when gonadotoxic treatments are being considered, to ensure fertility concerns are appropriately evaluated and managed.

Haematopoietic stem cell health in sickle cell disease and its implications for stem cell therapies and secondary haematological disorders

Gene modification of haematopoietic stem cells (HSCs) is a potentially curative approach to sickle cell disease (SCD) and offers hope for patients who are not eligible for allogeneic HSC transplantation. Current approaches require in vitro manipulation of healthy autologous HSC prior to their transplantation. However, the health and integrity of HSCs may be compromised by a variety of disease processes in SCD, and challenges have emerged in the clinical trials of gene therapy. There is also concern about increased susceptibility to haematological malignancies during long-term follow up of patients, and this raises questions about genomic stability in the stem cell compartment. In this review, we evaluate the evidence for HSC deficits in SCD and then discuss their potential causation. Finally, we suggest several questions which need to be addressed in order to progress with successful HSC manipulation for gene therapy in SCD.

An Expert Overview on Therapies in Non-Transfusion-Dependent Thalassemia: Classical to Cutting Edge in Treatment

The thalassemia issue is a growing worldwide health concern that anticipates the number of patients suffering from the disease will soon increase significantly. Patients with β-thalassemia intermedia (β-TI) manifest mild to intermediate levels of anemia, which is a reason for it to be clinically located between thalassemia minor and β-thalassemia major (β-TM). Notably, the determination of the actual rate of β-TI is more complicated than β-TM. The leading cause of this illness could be partial repression of β-globin protein production; accordingly, the rate of β-globin gene repression is different in patients, and the gene repression intensity creates a different clinical status. This review article provides an overview of functional mechanisms, advantages, and disadvantages of the classic to latest new treatments for this group of patients, depending on the disease severity divided into the typical management strategies for patients with β-TI such as fetal hemoglobin (Hb) induction, splenectomy, bone marrow transplantation (BMT), transfusion therapy, and herbal and chemical iron chelators. Recently, novel erythropoiesis-stimulating agents have been added. Novel strategies are subclassified into molecular and cellular interventions. Genome editing is one of the efficient molecular therapies for improving hemoglobinopathies, especially β-TI. It encompasses high-fidelity DNA repair (HDR), base and prime editing, clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 procedure, nuclease-free strategies, and epigenetic modulation. In cellular interventions, we mentioned the approach pattern to improve erythropoiesis impairments in translational models and patients with β-TI that involve activin II receptor traps, Janus-associated kinase 2 (JAK2) inhibitors, and iron metabolism regulation.

CRISPR Gene Therapy: A Promising One-Time Therapeutic Approach for Transfusion-Dependent β-Thalassemia—CRISPR-Cas9 Gene Editing for β-Thalassemia

β-Thalassemia is an inherited hematological disorder that results from genetic changes in the β-globin gene, leading to the reduced or absent synthesis of β-globin. For several decades, the only curative treatment option for β-thalassemia has been allogeneic hematopoietic cell transplantation (allo-HCT). Nonetheless, rapid progress in genome modification technologies holds great potential for treating this disease and will soon change the current standard of care for β-thalassemia. For instance, the emergence of the CRISPR/Cas9 genome editing platform has opened the door for precision gene editing and can serve as an effective molecular treatment for a multitude of genetic diseases. Investigational studies were carried out to treat β-thalassemia patients utilizing CRISPR-based CTX001 therapy targeting the fetal hemoglobin silencer BCL11A to restore γ-globin expression in place of deficient β-globin. The results of recently carried out clinical trials provide hope of CTX001 being a promising one-time therapeutic option to treat β-hemoglobinopathies. This review provides an insight into the key scientific steps that led to the development and application of novel CRISPR/Cas9–based gene therapies as a promising therapeutic platform for transfusion-dependent β-thalassemia (TDT). Despite the resulting ethical, moral, and social challenges, CRISPR provides an excellent treatment option against hemoglobin-associated genetic diseases.

MeGATAs, functional generalists in interactions between cassava growth and development, and abiotic stresses

The proteins with DNA-binding preference to the consensus DNA sequence (A/T) GATA (A/G) belong to a GATA transcription factor family, with a wide array of biological processes in plants. Cassava (Manihot esculenta) is an important food crop with high production of starch in storage roots. Little was however known about cassava GATA domain-containing genes (MeGATAs). Thirty-six MeGATAs, MeGATA1 to MeGATA36, were found in this study. Some MeGATAs showed a collinear relationship with orthologous genes of Arabidopsis, poplar and potato, rice, maize and sorghum. Eight MeGATA-encoded proteins (MeGATAs) analysed were all localized in the nucleus. Some MeGATAs had potentials of binding ligands and/or enzyme activity. One pair of tandem-duplicated MeGATA17-MeGATA18 and 30 pairs of whole genome-duplicated MeGATAs were found. Fourteen MeGATAs showed low or no expression in the tissues. Nine analysed MeGATAs showed expression responses to abiotic stresses and exogenous phytohormones. Three groups of MeGATA protein interactions were found. Fifty-three miRNAs which can target 18 MeGATAs were identified. Eight MeGATAs were found to target other 292 cassava genes, which were directed to radial pattern formation and phyllome development by gene ontology enrichment, and autophagy by Kyoto Encyclopaedia of Genes and Genomes enrichment. These data suggest that MeGATAs are functional generalists in interactions between cassava growth and development, abiotic stresses and starch metabolism.

Knowledge and practices on childhood anaemia, thalassaemia and iron deficiency among mothers of children aged between 6 and 59 months in a suburban area of Sri Lanka

BACKGROUND

Childhood anaemia is one of the most common public health problems worldwide. Here, we aim to describe the knowledge and practices on childhood anaemia, thalassaemia and iron deficiency among mothers of children aged between 6 and 59 months in a suburban district of Sri Lanka.

METHODS

We performed a cross-sectional survey in the Gampaha District of Sri Lanka from December 2020 to February 2021. One well-baby clinic each from four Medical Officer of Health areas in the district was selected using stratified random sampling. Mothers of all children aged between 6 and 59 months attending well-baby clinics were recruited until the sample size was achieved. Data were collected using a self-administered questionnaire and analysed using logistic regression.

RESULTS

A total of 392 mothers were recruited; 53% of their children were males. Only 33% of mothers had an accurate understanding of anaemia, while 71% and 28%, respectively, could name at least one symptom and two causes of anaemia; 12% could not name a single food rich in iron. Only 13% of mothers knew that thalassaemia is a cause of anaemia, and 14% had been screened for thalassaemia. Logistic regression analysis that examined for factors associated with higher knowledge of anaemia revealed that an accurate understanding of anaemia was associated with maternal age over 30 years (p < 0.05) and maternal education level beyond grade ten (p < 0.001). In contrast, higher knowledge of symptoms of anaemia was associated with maternal employment (p < 0.01).

CONCLUSIONS

The knowledge of anaemia and awareness of thalassaemia among mothers was poor. Very few mothers were aware of iron-rich food and feed it to their children. Despite being located in a thalassaemia-endemic region, very few knew that thalassaemia is a cause of anaemia and have got themselves screened for thalassaemia.

Significance of the mathematically calculated red cell indices in patients with qualitative and quantitative hemoglobinopathies

Background

Hemoglobinopathies represent a set of inherited red blood cell (RBCs) disorders, characterized by abnormal hemoglobin molecule. They include qualitative and quantitative hemoglobinopathies, with a structurally abnormal globin chain in the first and defective production in the later. This study assessed, for the first time, the significance of the mathematically calculated RBC indices to identify patients with hemoglobinopathies from normal subjects or iron deficiency anemia (IDA) and to differentiate various types of hemoglobinopathies from each other.

Subjects and methods

The study was a comparative hospital based and included 167 participants with hemoglobinopathies (group 1) and 49 participants with IDA (group 2) as an active comparator. Another 50 healthy volunteers (group 3) were also included. All participants were subjected to medical history, clinical examination, CBC, and HPLC. Next, 10 RBC indices were mathematically calculated from the CBC for each participant.

Results

Gender analysis shows that females represent 36.8% in thalassemia group, 42% in sickle cell disease (SCD) group, and 71.4% in IDA group. The receiver operating characteristic (ROC) curve shows that Ehsani index (EI) is the most reliable screening tool for thalassemics because of showing the highest Youden index and specificity of 41.88% and 88.89%, respectively, followed by Shine and Lal index (SL), with Youden index (YI) value, specificity, and sensitivity equal to 39.78%, 69.70%, and 70.09%, respectively. Similar results were found for IDA. For SCD, SL index is the most suitable screening tool. In conclusion, the mathematically calculated RBC indices are available, cheap, reliable, and sensitive tools for screening patients with hemoglobinopathies.

Safety and efficacy of mitapivat, an oral pyruvate kinase activator, in adults with non-transfusion dependent α-thalassaemia or β-thalassaemia: an open-label, multicentre, phase 2 study

BACKGROUND

Patients with non-transfusion-dependent thalassaemia (NTDT), although they do not require regular blood transfusions for survival, can still accrue a heavy burden of comorbidities. No approved disease-modifying therapies exist for these patients. We aimed to investigate the safety and efficacy of mitapivat (Agios Pharmaceuticals, Cambridge, MA, USA), a pyruvate kinase activator, in adults with non-transfusion-dependent (NTD) α-thalassaemia or NTD β-thalassaemia.

METHODS

In this open-label, multicentre, phase 2 study, patients were recruited from four academic clinical study sites in Oakland, CA, and Boston, MA, USA; Toronto, ON, Canada; and London, UK. Patients were eligible if they were aged 18 years or older, with NTDT (including β-thalassaemia with or without α-globin gene mutations, haemoglobin E β-thalassaemia, or α-thalassaemia), and a baseline haemoglobin concentration of 10·0 g/dL or lower. During a 24-week core period, mitapivat was administered orally at 50 mg twice daily for the first 6 weeks followed by an escalation to 100 mg twice daily for 18 weeks thereafter. The primary endpoint was haemoglobin response (a ≥1·0 g/dL increase in haemoglobin concentration from baseline at one or more assessments between weeks 4 and 12). Efficacy and safety were assessed in the full analysis set (ie, all patients who received at least one dose of study drug). This study is registered with ClinicalTrials.gov, NCT03692052, and is closed to accrual.

FINDINGS

Between Dec 28, 2018, and Feb 6, 2020, 27 patients were screened, of whom 20 were enrolled (15 [75%] with β-thalassaemia and five [25%] with α-thalassaemia) and received mitapivat. The median age of patients was 44 years (IQR 35-56), 15 (75%) of 20 patients were female, five (25%) were male, and ten (50%) identified as Asian. 16 (80% [90% CI 60-93]) of 20 patients had a haemoglobin response (p<0·0001), five (100%) of five with α-thalassaemia and 11 (73%) of 15 with β-thalassaemia. 17 (85%) patients had a treatment-emergent adverse event, and 13 had a treatment-emergent event that was considered to be treatment related. One serious treatment-emergent adverse event occurred (grade 3 renal impairment), which was considered unrelated to study drug, resulting in discontinuation of treatment. The most commonly reported treatment-emergent adverse events were initial insomnia (ten [50%] patients), dizziness (six [30%]), and headache (five [25%]). No patients died during the 24-week core period.

INTERPRETATION

These efficacy and safety results support the continued investigation of mitapivat for the treatment of both α-thalassaemia and β-thalassaemia.

FUNDING

Agios Pharmaceuticals.

Efficacy and Safety of Hydroxyurea as Adjuvant Therapy in Pediatric Patients of Transfusion-Dependent Beta-Thalassemia Major at Zhob, Balochistan

Background

Hydroxyurea is being used effectively in sickle cell anemia and thalassemia intermedia. Its role in transfusion-dependent beta-thalassemia major yet needs to be clearly established. This study has been carried out to assess the efficacy and safety of hydroxyurea as adjuvant therapy in pediatric cases of transfusion-dependent beta-thalassemia major disease.

Materials and methods

This quasi-experimental study was carried out at District Headquarter Hospital (DHQ), Zhob, from February 2021 to January 2022. One hundred ten cases fulfilling the inclusion-exclusion criteria were selected and divided into groups of 55 each. Group A cases received hydroxyurea (10-20 mg/kg/day) in addition to blood transfusion and chelation therapy. Group B received a blood transfusion and chelation therapy only. Both groups were compared in terms of blood transfusion requirement, mean hemoglobin, and mean serum ferritin levels. All the data were analyzed with SPSS 21 (IBM Corp., Armonk, NY).

Results

Of Group A cases, three were dropped because of side effects of hydroxyurea, and two were lost to follow-up. Similarly, three cases of Group B lost to follow-up, one patient withdrew consent, and one child died at home; thus both groups were left with 50 cases each. The mean age of participants was 11.98 + 3.74 years. There were 51 males and 49 females. Both the groups were comparable in terms of age and gender. Similarly, mean hemoglobin levels and serum ferritin levels were comparable at the start of the study. After one year, there was a significant improvement in mean hemoglobin level (p<0.001) and a significant reduction in serum ferritin levels (p=0.014) in the group taking adjuvant hydroxyurea. The requirement of packed red blood cells (RBCs) significantly decreased in cases taking hydroxyurea (p<0.001).

Conclusion

Hydroxyurea is a safe and effective treatment that significantly decreases the packed RBC transfusion requirement in transfusion-dependent thalassemia children, improves hemoglobin levels, and reduces serum ferritin levels compared to the children on blood transfusions alone.

Pharmacological Induction of Fetal Hemoglobin in β-Thalassemia and Sickle Cell Disease: An Updated Perspective

A significant amount of attention has recently been devoted to the mechanisms involved in hemoglobin (Hb) switching, as it has previously been established that the induction of fetal hemoglobin (HbF) production in significant amounts can reduce the severity of the clinical course in diseases such as β-thalassemia and sickle cell disease (SCD). While the induction of HbF using lentiviral and genome-editing strategies has been made possible, they present limitations. Meanwhile, progress in the use of pharmacologic agents for HbF induction and the identification of novel HbF-inducing strategies has been made possible as a result of a better understanding of γ-globin regulation. In this review, we will provide an update on all current pharmacological inducer agents of HbF in β-thalassemia and SCD in addition to the ongoing research into other novel, and potentially therapeutic, HbF-inducing agents.

A randomised double-blind placebo-controlled clinical trial of oral hydroxyurea for transfusion-dependent β-thalassaemia

Hydroxyurea is an antimetabolite drug that induces fetal haemoglobin in sickle cell disease. However, its clinical usefulness in β-thalassaemia is unproven. We conducted a randomised, double-blind, placebo-controlled clinical trial to evaluate the efficacy and safety of hydroxyurea in transfusion-dependent β-thalassaemia. Sixty patients were assigned 1:1 to oral hydroxyurea 10–20 mg/kg/day or placebo for 6 months by stratified block randomisation. Hydroxyurea treatment did not alter the blood transfusion volume overall. However, a significantly higher proportion of patients on hydroxyurea showed increases in fetal haemoglobin percentage (89% vs. 59%; p < 0.05) and reductions in erythropoietic stress as measured by soluble transferrin receptor concentration (79% vs. 40%; p < 0.05). Based on fetal haemoglobin induction (> 1.5%), 44% of patients were identified as hydroxyurea-responders. Hydroxyurea-responders, required significantly lower blood volume (77 ± SD27ml/kg) compared to hydroxyurea-non-responders (108 ± SD24ml/kg; p < 0.01) and placebo-receivers (102 ± 28ml/kg; p < 0.05). Response to hydroxyurea was significantly higher in patients with HbE β-thalassaemia genotype (50% vs. 0%; p < 0.01) and Xmn1 polymorphism of the γ-globin gene (67% vs. 27%; p < 0.05). We conclude that oral hydroxyurea increased fetal haemoglobin percentage and reduced erythropoietic stress of ineffective erythropoiesis in patients with transfusion-dependent β-thalassaemia. Hydroxyurea reduced the transfusion burden in approximately 40% of patients. Response to hydroxyurea was higher in patients with HbE β-thalassaemia genotype and Xmn1 polymorphism of the γ-globin gene.

Genetic and Epigenetic Therapies for β-Thalassaemia by Altering the Expression of α-Globin Gene

β-Thalassaemia is caused by over 300 mutations in and around the β-globin gene that lead to impaired synthesis of β-globin. The expression of α-globin continues normally, resulting in an excess of α-globin chains within red blood cells and their precursors. These unpaired α-globin chains form unstable α-hemichromes that trigger cascades of events to generate reactive oxygen species, leading to ineffective erythropoiesis and haemolysis in patients with β-thalassaemia. The clinical genetic data reported over several decades have demonstrated how the coinheritance of α-thalassaemia ameliorates the disease phenotype of β-thalassaemia. Thus, it is evident that down-regulation of the α-globin gene expression in patients with β-thalassaemia could ameliorate or even cure β-thalassaemia. Over the last few years, significant progress has been made in utilising this pathway to devise a cure for β-thalassaemia. Most research has been done to alter the epigenetic landscape of the α-globin locus or the well-characterised distant enhancers of α-globin. In vitro, pre-clinical studies on primary human erythroid cells have unveiled inhibition of histone lysine demethylation and histone deacetylation as potential targets to achieve selective downregulation of α-globin through epigenetic drug targeting. CRISPR based genome editing has been successfully used in vitro to mutate α-globin genes or enhancers of α-goblin to achieve clinically significant knockdowns of α-globin to the levels beneficial for patients with β-thalassaemia. This review summarises the current knowledge on the regulation of human α-globin genes and the clinical genetic data supporting the pathway of targeting α-globin as a treatment for β-thalassaemia. It also presents the progress of epigenetic drug and genome editing approaches currently in development to treat β-thalassaemia.

Luspatercept for β-thalassemia: beyond red blood cell transfusions

INTRODUCTION

Red blood cell transfusions and iron chelation therapy are the cornerstone of treatment for β-thalassemia, with allogeneic hematopoietic stem cell transplantation and gene therapy offering further disease-management options for eligible patients. With up to 90% of severe cases of β-thalassemia occurring in resource-constrained countries, and estimates indicating that 22,500 deaths occur annually as a direct consequence of undertransfusion, provision of adequate treatment remains a major issue.

AREAS COVERED

In this review, we provide an overview of luspatercept, a first-in-class erythroid maturation agent, and present the available clinical data related to the treatment of β-thalassemia.

EXPERT OPINION

The recent approval of luspatercept offers a new, long-term therapeutic option for adult patients with transfusion-dependent β-thalassemia to reduce red blood cell transfusion burden, anemia, and iron overload.

Ineffective Erythropoiesis in β-Thalassaemia: Key Steps and Therapeutic Options by Drugs

β-thalassaemia is a rare genetic condition caused by mutations in the β-globin gene that result in severe iron-loading anaemia, maintained by a detrimental state of ineffective erythropoiesis (IE). The role of multiple mechanisms involved in the pathophysiology of the disease has been recently unravelled. The unbalanced production of α-globin is a major source of oxidative stress and membrane damage in red blood cells (RBC). In addition, IE is tightly linked to iron metabolism dysregulation, and the relevance of new players of this pathway, i.e., hepcidin, erythroferrone, matriptase-2, among others, has emerged. Advances have been made in understanding the balance between proliferation and maturation of erythroid precursors and the role of specific factors in this process, such as members of the TGF-β superfamily, and their downstream effectors, or the transcription factor GATA1. The increasing understanding of IE allowed for the development of a broad set of potential therapeutic options beyond the current standard of care. Many candidates of disease-modifying drugs are currently under clinical investigation, targeting the regulation of iron metabolism, the production of foetal haemoglobin, the maturation process, or the energetic balance and membrane stability of RBC. Overall, they provide tools and evidence for multiple and synergistic approaches that are effectively moving clinical research in β-thalassaemia from bench to bedside.

Cell and Gene Therapy for Anemia: Hematopoietic Stem Cells and Gene Editing

Hereditary anemia has various manifestations, such as sickle cell disease (SCD), Fanconi anemia, glucose-6-phosphate dehydrogenase deficiency (G6PDD), and thalassemia. The available management strategies for these disorders are still unsatisfactory and do not eliminate the main causes. As genetic aberrations are the main causes of all forms of hereditary anemia, the optimal approach involves repairing the defective gene, possibly through the transplantation of normal hematopoietic stem cells (HSCs) from a normal matching donor or through gene therapy approaches (either in vivo or ex vivo) to correct the patient’s HSCs. To clearly illustrate the importance of cell and gene therapy in hereditary anemia, this paper provides a review of the genetic aberration, epidemiology, clinical features, current management, and cell and gene therapy endeavors related to SCD, thalassemia, Fanconi anemia, and G6PDD. Moreover, we expound the future research direction of HSC derivation from induced pluripotent stem cells (iPSCs), strategies to edit HSCs, gene therapy risk mitigation, and their clinical perspectives. In conclusion, gene-corrected hematopoietic stem cell transplantation has promising outcomes for SCD, Fanconi anemia, and thalassemia, and it may overcome the limitation of the source of allogenic bone marrow transplantation.