Emerging therapies in β-thalassemia: toward a new era in management

Unmet needs in β-thalassemia and the evolving treatment landscape

β-thalassemias are genetic disorders causing an imbalance in hemoglobin production, leading to varying degrees of anemia, with two clinical phenotypes: transfusion-dependent thalassemia (TDT) and non-transfusion-dependent thalassemia (NTDT). Red blood cell transfusions and iron chelation therapy are the conventional treatment options for the management of β-thalassemia. Currently available conventional therapies in thalassemia have many challenges and limitations. Accordingly, multiple novel therapeutic approaches are currently being developed for the treatment of β-thalassemias. These strategies can be classified into three categories based on their efforts to address different aspects of the underlying pathophysiology of β-thalassemia: correction of the α/β globin chain imbalance, addressing ineffective erythropoiesis, and targeting iron dysregulation. Managing β- thalassemia presents challenges due to the many complications that can manifest, limited access and availability of blood products, and lack of compliance/adherence to treatment. Novel therapies targeting ineffective erythropoiesis and thus improving anemia and reducing the need for chronic blood transfusions seem promising. However, the complex nature of the disease itself requires personalized treatment plans for each patient. Collaborations and partnerships between thalassemia centers can also help share knowledge and resources, particularly in regions with higher prevalence and limited resources. This review will explore the different conventional treatment modalities available today for the management of β-thalassemia, discuss the unmet needs and challenges associated with them in addition to exploring the role of some novel therapeutic agents in the field.

Beta-thalassemia: is cure still a dream?

β-thalassemia is a monogenic disorder characterized by decreased hemoglobin production, resulting in chronic anemia. There are several factors affecting the clinical presentation of patients with β-thalassemia, and several complications such as iron overload or ineffective erythropoiesis have been linked to this disease. Until nowadays, several conservative therapies namely blood transfusions, iron chelation, and the FDA-approved drug Luspatercept have been adopted alongside other debatable permanent cures. Other clinical trials are being conducted to develop better and safer management techniques for these patients. This review will discuss the different treatment strategies of β-thalassemia including novel therapies, besides all possible curative therapies that are being developed for this disease.

Emerging Therapies in β-Thalassemia

Advances in understanding the underlying pathophysiology of β-thalassemia have enabled efforts toward the development of novel therapeutic modalities. These can be classified into three major categories based on their ability to target different features of the underlying disease pathophysiology: correction of the α/β globin chain imbalance, targeting ineffective erythropoiesis, and targeting iron dysregulation. This article provides an overview of these different emerging therapies that are currently in development for β-thalassemia.

Therapeutic perspective for children and young adults living with thalassemia and sickle cell disease

Hemoglobinopathies, including thalassemias and sickle cell disease, are the most common monogenic diseases worldwide, with estimated annual births of more than 330,000 affected infants. Hemoglobin disorders account for about 3.4% of deaths in children under 5 years of age. The distribution of these diseases is historically linked to current or previously malaria-endemic regions; however, immigration has led to a worldwide distribution of these diseases, making them a global health problem. During the last decade, new treatment approaches and novel therapies have been proposed, some of which have the potential to change the natural history of these disorders. Indeed, the first erythroid maturation agent, luspatercept, and gene therapy have been approved for beta-thalassemia adult patients. For sickle cell disease, molecules targeting vaso-occlusion and hemoglobin S polymerization include crizanlizumab, which has been approved for patients ≥ 16 years, voxelotor approved for patients ≥ 12 years, and L-glutamine for patients older than 5 years.    Conclusion: We herein present the most recent advances and future perspectives in thalassemia and sickle cell disease treatment, including new drugs, gene therapy, and gene editing, and the current clinical trial status in the pediatric populations. What is Known: • Red blood cell transfusions, iron chelation therapy and hematopoietic stem cell transplantation have been the mainstay of treatment of thalassemia patients for decades. • For sickle cell disease, until 2005, treatment strategies were mostly the same as those for thalassemia, with the option of simple transfusion or exchange transfusion. In 2007, hydroxyurea was approved for patients ≥ 2 years old. What is New: • In 2019, gene therapy with betibeglogene autotemcel (LentiGlobin BB305) was approved for TDT patients ≥ 12 years old non β0/β0 without matched sibling donor. • Starting from 2017 several new drugs, such as L-glutamine (approved only by FDA), crizanlizumab (approved by FDA and EMA for patients ≥ 16 years), and lastly voxelotor (approved by FDA and EMA for patients ≥ 12 years old).

Thalassaemia-A global view

The thalassaemias are a group of genetic disorders of haemoglobin which are endemic in the tropics but are now found worldwide due to migration. Basic standard of care therapy includes regular transfusions to maintain a haemoglobin level of around 10 g/dL, together with iron chelation therapy to prevent iron overload. Novel therapies, bone marrow transplantation, and gene therapy are treatment options that are unavailable in many countries with stressed economies. This Wider Perspectives article presents the strategies for management of an adolescent refugee patient with beta thalassaemia, as it would be performed by expert haematologists in six countries: Italy, Lebanon, Oman, the Sudan, Thailand and the United States. The experienced clinicians in each country have adapted their practice according to the resources available, which vary greatly. Even in the current modern era, providing adequate transfusions and chelation is problematic in many countries. On the other hand, ensuring adherence to therapy, particularly during adolescence, is a similar challenge seen in all countries. The concluding section highlights the disparities in available therapies and puts the role of novel therapies into a societal context.

In silico multiscale drug design to discover key structural features of potential JAK2 inhibitors

Background: JAK2 inhibitors have been proposed as a new therapeutic option for thalassemia therapy. The objective of this study was to discover the key structural features for improving 2-aminopyrimidine derivatives as potential JAK2 inhibitors. Materials & methods: Quantitative structure-activity relationship (QSAR) approaches (hologram QSAR and comparative molecular similarity indices analysis), molecular dynamics simulations, binding energy calculations and pharmacokinetic predictions were employed. Results: Reliable QSAR models, binding mode and binding interactions of JAK2 inhibitors were obtained and these obtained results were used as the key information for rational design of highly potent JAK2 inhibitors. Conclusion: The concept of new potential JAK2 inhibitors integrated from the obtained results was proved, producing two newly designed compounds, D01 and D02, with potential for use as JAK2 inhibitors.

Improving Ineffective Erythropoiesis in Thalassemia: A Hope on the Horizon

Beta-thalassemia is an inherited hemoglobinopathy characterized by the impaired synthesis of beta-globin chains of hemoglobin leading to chronic hemolytic anemia. The mainstay of treatment for most patients remains regular blood transfusions and iron chelation. This conventional therapy has many limitations and challenges. Allogeneic hematopoietic stem cell transplant (HSCT) is the only available curative treatment but the availability of a suitable donor, financial constraints, and a need for specialist physicians can be limiting factors. Gene therapy is an upcoming curative therapeutic modality. An increased understanding of the underlying pathophysiology and molecular mechanisms of thalassemia has paved the way for novel pharmacological agents targeting ineffective erythropoiesis. These drugs act by decreasing transfusion requirements and hence decrease transfusion-related complications. The present review intends to provide an insight into the recent advances in pharmacological agents targeting ineffective erythropoiesis. Literature was searched and relevant articles evaluating newer drugs in thalassemia were collected from databases, including Pubmed, Scopus, Prospero, Clinicaltrials.gov, Google Scholar, and the Google search engine. We used the following keywords: thalassemia, novel, treatment, drugs, and ineffective erythropoiesis during the initial search. Relevant titles and abstracts were screened to choose relevant articles. Further, the full-text articles were retrieved and relevant cross-references were scanned to collect information for the present review.

2021 update on clinical trials in β-thalassemia

The treatment landscape for patients with β-thalassemia is witnessing a swift evolution, yet several unmet needs continue to persist. Patients with transfusion-dependent β-thalassemia (TDT) primarily rely on regular transfusion and iron chelation therapy, which can be associated with considerable treatment burden and cost. Patients with non-transfusion-dependent β-thalassemia (NTDT) are also at risk of significant morbidity due to the underlying anemia and iron overload, but treatment options in this patient subgroup are limited. In this review, we provide updates on clinical trials of novel therapies targeting the underlying pathology in β-thalassemia, including the α/non-α-globin chain imbalance, ineffective erythropoiesis, and iron dysregulation.

Improving outcomes and quality of life for patients with transfusion-dependent β-thalassemia: recommendations for best clinical practice and the use of novel treatment strategies

INTRODUCTION

β-thalassemia is one of the most common inherited monogenic diseases. Many patients are dependent on a lifetime of red blood cell (RBC) transfusions and iron chelation therapy. Although treatments have a significant impact on quality of life (QoL), life expectancy, and long-term health outcomes have improved in recent decades through safer RBC transfusion practices and better iron chelation strategies. Advances in the understanding of the pathology of β-thalassemia have led to the development of new treatment options that have the potential to reduce the RBC transfusion burden in patients with transfusion-dependent (TD) β-thalassemia and improve QoL.

AREAS COVERED

This review provides an overview of currently available treatments for patients with TD β-thalassemia, highlighting QoL issues, and providing an update on current clinical experience plus important practical points for two new treatments available for TD β-thalassemia: betibeglogene autotemcel (beti-cel) gene therapy and the erythroid maturation agent luspatercept, an activin ligand trap.

EXPERT OPINION

Approved therapies, including curative gene therapies and supportive treatments such as luspatercept, have the potential to reduce RBC transfusion burden, and improve clinical outcomes and QoL in patients with TD β-thalassemia. Cost of treatment is, however, likely to be a significant barrier for payors and patients.

Novel therapies in β-thalassaemia

Beta-thalassaemia is one of the most significant haemoglobinopathies worldwide resulting in the synthesis of little or no β-globin chains. Without treatment, β-thalassaemia major is lethal within the first decade of life due to the complex pathophysiology, which leads to wide clinical manifestations. Current clinical management for these patients depends on repeated transfusions followed by iron-chelating therapy. Several novel approaches to correct the resulting α/β-globin chain imbalance, treat ineffective erythropoiesis and improve iron overload are currently being developed. Up to now, the only curative treatment for β-thalassemia is haematopoietic stem-cell transplantation, but this is a risky and costly procedure. Gene therapy, gene editing and base editing are emerging as a powerful approach to treat this disease. In β-thalassaemia, gene therapy involves the insertion of a vector containing the normal β-globin or γ-globin gene into haematopoietic stem cells to permanently produce normal red blood cells. Gene editing and base editing involves the use of zinc finger nucleases, transcription activator-like nucleases and clustered regularly interspaced short palindromic repeats/Cas9 to either correct the causative mutation or else insert a single nucleotide variant that will increase foetal haemoglobin. In this review, we will examine the current management strategies used to treat β-thalassaemia and focus on the novel therapies targeting ineffective erythropoiesis, improving iron overload and correction of the globin chain imbalance.