Development of gene therapy for thalassemia

Advances in gene therapy approaches targeting neuro-inflammation in neurodegenerative diseases

Over the last three decades, neurodegenerative diseases (NDs) have increased in frequency. About 15% of the world's population suffers from NDs in some capacity, which causes cognitive and physical impairment. Neurodegenerative diseases, including Amyotrophic Lateral Sclerosis, Parkinson's disease, Alzheimer's disease, and others represent a significant and growing global health challenge. Neuroinflammation is recognized to be related to all NDs, even though NDs are caused by a complex mix of genetic, environmental, and lifestyle factors. Numerous genes and pathways such as NFκB, p38 MAPK, Akt/mTOR, caspase, nitric oxide, and COX are involved in triggering brain immune cells like astrocytes and microglia to secrete inflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6. In AD, the binding of Aβ with CD36, TLR4, and TLR6 receptors results in activation of microglia which start to produce proinflammatory cytokines and chemokines. Consequently, the pro-inflammatory cytokines worsen and spread neuroinflammation, causing the deterioration of healthy neurons and the impairment of brain functions. Gene therapy has emerged as a promising therapeutic approach to modulate the inflammatory response in NDs, offering potential neuroprotective effects and disease-modifying benefits. This review article focuses on recent advances in gene therapy strategies targeting neuroinflammation pathways in NDs. We discussed the molecular pathways involved in neuroinflammation, highlighted key genes and proteins implicated in these processes, and reviewed the latest preclinical and clinical studies utilizing gene therapy to modulate neuroinflammatory responses. Additionally, this review addressed the prospects and challenges in translating gene therapy approaches into effective treatments for NDs.

Systematic review of hematopoietic stem cell gene therapy approach in thalassemia: Comparative analysis in animal models

Hematopoietic stem cell (HSC) gene therapy has shown potential as a therapeutic approach for thalassemia in recent years. However, a comparison of the varying gene therapy methods of HSC gene therapy in thalassemia has never been reviewed. This study aims to evaluate the utilization of HSC gene therapy approaches in animal models of thalassemia. A systematic review was conducted in five databases: PubMed, EBSCOHost, Science Direct, SCOPUS, and Proquest using a combination of the terms hematopoietic stem cell or hematopoietic stem cell or HSC, thalassemia, genetic therapy or gene therapy and animal model. Only journals published in English between 2008 and 2023 were included. This literature included six studies analyzing the use of HSC gene therapy in thalassemic mice models. The three outcomes being assessed in this review were globin levels, hematological parameters, and red blood cell (RBC) phenotypes. Gene therapy approaches for thalassemia using HSC showed significant improvement in β-globin levels and RBC phenotypes. Phenotypic improvements were also observed. These outcomes indicate good efficacy in gene therapy for thalassemia in mice models. Furthermore, more studies assessing the efficacy of HSC gene therapy in the human model should be done in future studies.

A systematic review of clinical trials for gene therapies for β-hemoglobinopathy around the world

BACKGROUND AIMS

Amidst the success of cell therapy for the treatment of onco-hematological diseases, the first recently Food and Drug Administration-approved gene therapy product for patients with transfusion-dependent β-thalassemia (TDT) indicates the feasibility of gene therapy as curative for genetic hematologic disorders. This work analyzed the current-world scenario of clinical trials involving gene therapy for β-hemoglobinopathies.

METHODS

Eighteen trials for patients with sickle cell disease (SCD) and 24 for patients with TDT were analyzed.

RESULTS

Most are phase 1 and 2 trials, funded by the industry and are currently recruiting volunteers. Treatment strategies for both diseases are fetal hemoglobin induction (52.4%); addition of wild-type or therapeutic β-globin gene (38.1%) and correction of mutations (9,5%). Gene editing (52.4%) and gene addition (40.5%) are the two most used techniques. The United States and France are the countries with the greatest number of clinical trials centers for SCD, with 83.1% and 4.2%, respectively. The United States (41.1%), China (26%) and Italy (6.8%) lead TDT trials centers.

CONCLUSIONS

Geographic trial concentration indicates the high costs of this technology, logistical issues and social challenges that need to be overcome for gene therapy to reach low- and middle-income countries where SCD and TDT are prevalent and where they most impact the patient's health.

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.

Does Hepcidin Tuning Have a Role among Emerging Treatments for Thalassemia?

The treatments available for thalassemia are rapidly evolving, with major advances made in gene therapy and the modulation of erythropoiesis. The latter includes the therapeutic potential of hepcidin tuning. In thalassemia, hepcidin is significantly depressed, and any rise in hepcidin function has a positive effect on both iron metabolism and erythropoiesis. Synthetic hepcidin and hepcidin mimetics have been developed to the stage of clinical trials. However, they have failed to produce an acceptable efficacy/safety profile. It seems difficult to avoid iron over-restricted erythropoiesis when directly using hepcidin as a drug. Indirect approaches, each one with their advantages and disadvantages, are many and in full development. The ideal approach is to target erythroferrone, the main inhibitor of hepcidin expression, the plasma concentrations of which are greatly increased in iron-loading anemias. Potential means of improving hepcidin function in thalassemia also include acting on TMPRSS6, TfR1, TfR2 or ferroportin, the target of hepcidin. Only having a better understanding of the crosslinks between iron metabolism and erythropoiesis will elucidate the best single option. In the meantime, many potential combinations are currently being explored in preclinical studies. Any long-term clinical study on this approach should include the wide monitoring of functions, as the effects of hepcidin and its modulators are not limited to iron metabolism and erythropoiesis. It is likely that some of the aspects of hepcidin tuning described briefly in this review will play a role in the future treatment of 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.

Molecular genetics of β-thalassemia: A narrative review

ABSTRACT

β-thalassemia is a hereditary hematological disease caused by over 350 mutations in the β-globin gene (HBB). Identifying the genetic variants affecting fetal hemoglobin (HbF) production combined with the α-globin genotype provides some prediction of disease severity for β-thalassemia. However, the generation of an additive composite genetic risk score predicts prognosis, and guide management requires a larger panel of genetic modifiers yet to be discovered.Presently, using data from prior clinical trials guides the design of further research and academic studies based on gene augmentation, while fundamental insights into globin switching and new technology developments have inspired the investigation of novel gene therapy approaches.Genetic studies have successfully characterized the causal variants and pathways involved in HbF regulation, providing novel therapeutic targets for HbF reactivation. In addition to these HBB mutation-independent strategies involving HbF synthesis de-repression, the expanding genome editing toolkit provides increased accuracy to HBB mutation-specific strategies encompassing adult hemoglobin restoration for personalized treatment of hemoglobinopathies. Allogeneic hematopoietic stem cell transplantation was, until very recently, the curative option available for patients with transfusion-dependent β-thalassemia. Gene therapy currently represents a novel therapeutic promise after many years of extensive preclinical research to optimize gene transfer protocols.We summarize the current state of developments in the molecular genetics of β-thalassemia over the last decade, including the mechanisms associated with ineffective erythropoiesis, which have also provided valid therapeutic targets, some of which have been shown as a proof-of-concept.

A systematic review of quality of life in sickle cell disease and thalassemia after stem cell transplant or gene therapy

Patients with sickle cell disease (SCD) and thalassemia experience several complications across their lifespan that lead to impairment in different health-related quality of life (HRQOL) domains. There is increasing interest in curative therapies for patients with SCD and thalassemia, including hematopoietic stem cell transplant (HSCT) and gene therapy; however, the effect of these therapies on various HRQOL domains remains unclear. Our objective was to systematically evaluate the most recent evidence for the effect of HSCT and gene therapy on HRQOL in patients with SCD and thalassemia. A systematic search of medical literature databases was conducted. A total of 16 studies (thalassemia, n = 9; SCD, n = 6; both, n = 1) involving 517 participants met inclusion criteria (thalassemia, n = 416; SCD, n = 101). HSCT was associated with a small to large positive effects in most HRQOL domains (Cohen's d; mean = 0.47; median = 0.37; range, 0.27-2.05). In thalassemia, HSCT was frequently associated with large positive effects in physical and emotional HRQOL domains (median d = 0.79 and d = 0.57, respectively). In SCD, HSCT was associated with large positive effects in all HRQOL domains. Emerging data suggest improvement in HRQOL outcomes across different domains following gene therapy in thalassemia and SCD. The quality of evidence was moderate in 13 studies (81%). HSCT has a positive impact on several HRQOL domains in patients with SCD and thalassemia; however, more longitudinal studies are warranted to assess the sustainability of these effects. Reporting HRQOL outcomes from ongoing gene therapy or gene-editing trials in SCD and thalassemia is key to better understand the benefits of such therapies.

Viral Vector Systems for Gene Therapy: A Comprehensive Literature Review of Progress and Biosafety Challenges

INTRODUCTION

National Institutes of Health (NIH) defines gene therapy as an experimental technique that uses genes to treat or prevent disease. Although gene therapy is a promising treatment option for a number of diseases (including inherited disorders, some types of cancer, and certain viral infections), the technique remains risky and is still under study to make sure that it will be effective and safe.

METHODS

Applications of viral vectors and nonviral gene delivery systems have found an encouraging new beginning in gene therapy in recent years. Although several viral vectors and nonviral gene delivery systems have been developed in the past 3 decades, no one delivery system can be applied in gene therapy to all cell types in vitro and in vivo. Furthermore, the use of viral vector systems (both in vitro and in vivo) present unique occupational health and safety challenges. In this review article, we discuss the biosafety challenges and the current framework of risk assessment for working with the viral vector systems.

DISCUSSION

The recent advances in the field of gene therapy is exciting, but it is important for scientists, institutional biosafety committees, and biosafety officers to safeguard public trust in the use of this technology in clinical trials and make conscious efforts to engage the public through ongoing forums and discussions.

Episomal vectors based on S/MAR and the β-globin Replicator, encoding a synthetic transcriptional activator, mediate efficient γ-globin activation in haematopoietic cells

We report the development of episomal vectors for the specific γ-globin transcription activation in its native position by activator Zif-VP64, based on the Scaffold/Matrix Attachment Region (S/MAR) for episomal retention and the β-globin Replicator, the DNA replication-Initiation Region from the β-globin locus. Vector Zif-VP64-Ep1 containing transcription cassettes CMV- Zif-VP64 and CMV-eGFP-S/MAR transfected a)K562 cells; b)murine β-YAC bone marrow cells (BMC); c)human haematopoietic progenitor CD34⁺ cells, with transfection efficiencies of 46.3 ± 5.2%, 23.0 ± 2.1% and 24.2 ± 2.4% respectively. K562 transfections generated stable cell lines running for 28 weeks with and without selection, with increased levels of γ-globin mRNA by 3.3 ± 0.13, of γ-globin protein by 6.75 ± 3.25 and HbF protein by 2 ± 0.2 fold, while the vector remained episomal and non integrated. In murine β-YAC BMCs the vector mediated the activation of the silent human γ-globin gene and in CD34⁺ cells, increased γ-globin mRNA, albeit only transiently. A second vector Zif-VP64-Ep2, with both transcription cassettes carrying promoter SFFV instead of CMV and the addition of β-globin Replicator, transferred into CD34⁺ cells, produced CD34⁺ eGFP⁺ cells, that generated colonies in colony forming cell cultures. Importantly, these were 100% fluorescent, with 2.11 ± 0.13 fold increased γ-globin mRNA, compared to non-transfected cells. We consider these episomal vectors valid, safer alternatives to viral vectors.

Autologous Stem-Cell-Based Gene Therapy for Inherited Disorders: State of the Art and Perspectives

Gene therapy using patient's own stem cells is rapidly becoming an alternative to allogeneic stem cell transplantation, especially when suitably compatible donors cannot be found. The advent of efficient virus-based methods for delivering therapeutic genes has enabled the development of genetic medicines for inherited disorders of the immune system, hemoglobinopathies, and a number of devastating metabolic diseases. Here, we briefly review the state of the art in the field, including gene editing approaches. A growing number of pediatric diseases can be successfully cured by hematopoietic stem-cell-based gene therapy.

Gene Addition Strategies for β-Thalassemia and Sickle Cell Anemia

Beta-thalassemia and sickle cell anemia are two of the most common diseases related to the hemoglobin protein. In these diseases, the beta-globin gene is mutated, causing severe anemia and ineffective erythropoiesis. Patients can additionally present with a number of life-threatening co-morbidities, such as stroke or spontaneous fractures. Current treatment involves transfusion and iron chelation; allogeneic bone marrow transplant is the only curative option, but is limited by the availability of matching donors and graft-versus-host disease. As these two diseases are monogenic diseases, they make an attractive setting for gene therapy. Gene therapy aims to correct the mutated beta-globin gene or add back a functional copy of beta- or gamma-globin. Initial gene therapy work was done with oncoretroviral vectors, but has since shifted to lentiviral vectors. Currently, there are a few clinical trials underway to test the curative potential of some of these lentiviral vectors. This review will highlight the work done thus far, and present the challenges still facing gene therapy, such as genome toxicity concerns and achieving sufficient transgene expression to cure those with the most severe forms of thalassemia.

Customizing the genome as therapy for the β-hemoglobinopathies

Despite nearly complete understanding of the genetics of the β-hemoglobinopathies for several decades, definitive treatment options have lagged behind. Recent developments in technologies for facile manipulation of the genome (zinc finger nucleases, transcription activator-like effector nucleases, or clustered regularly interspaced short palindromic repeats-based nucleases) raise prospects for their clinical application. The use of genome-editing technologies in autologous CD34(+) hematopoietic stem and progenitor cells represents a promising therapeutic avenue for the β-globin disorders. Genetic correction strategies relying on the homology-directed repair pathway may repair genetic defects, whereas genetic disruption strategies relying on the nonhomologous end joining pathway may induce compensatory fetal hemoglobin expression. Harnessing the power of genome editing may usher in a second-generation form of gene therapy for the β-globin disorders.

Restriction of HIV-1-based lentiviral vectors in adult primary marrow-derived and peripheral mobilized human CD34+ hematopoietic stem and progenitor cells occurs prior to viral DNA integration

Background

Gene therapy is currently being attempted using a number of delivery vehicles including lentiviral-based vectors. The delivery and insertion of a gene using lentiviral-based vectors involves multiple discrete steps, including reverse transcription of viral RNA into DNA, nuclear entry, integration of viral DNA into the host genome and expression of integrated genes. Transduction of murine stem cells by the murine leukemia viruses is inefficient because the expression of the integrated DNA is profoundly blocked. Transduction of human stem cells by lentivirus vectors is also inefficient, but the cause and specific part of the retroviral lifecycle where this block occurs is unknown.

Results

Here we demonstrate that the dominant point of restriction of an HIV-1-based lentiviral vector in adult human hematopoietic stem and progenitor cells (HSPCs) from bone marrow and also those obtained following peripheral mobilization is prior to viral DNA integration. We specifically show that restriction of HSPCs to an HIV-1-based lentiviral vector is prior to formation of nuclear DNA forms.

Conclusions

Murine restriction of MLV and human cellular restriction of HIV-1 are fundamentally different. While murine restriction of MLV occurs post integration, human restriction of HIV-1 occurs before integration.

Advances in understanding erythropoiesis: evolving perspectives

Red blood cells (RBCs) are generated from haematopoietic stem and progenitor cells (HSPCs) through the step-wise process of differentiation known as erythropoiesis. In this review, we discuss our current understanding of erythropoiesis and highlight recent advances in this field. During embryonic development, erythropoiesis occurs in three distinct waves comprising first, the yolk sac-derived primitive RBCs, followed sequentially by the erythro-myeloid progenitor (EMP) and HSPC-derived definitive RBCs. Recent work has highlighted the complexity and variability that may exist in the hierarchical arrangement of progenitors responsible for erythropoiesis. Using recently defined cell surface markers, it is now possible to enrich for erythroid progenitors and precursors to a much greater extent than has been possible before. While a great deal of knowledge has been gained on erythropoiesis from model organisms, our understanding of this process is currently being refined through human genetic studies. Genes mutated in erythroid disorders can now be identified more rapidly by the use of next-generation sequencing techniques. Genome-wide association studies on erythroid traits in healthy populations have also revealed new modulators of erythropoiesis. All of these recent developments have significant promise not only for increasing our understanding of erythropoiesis, but also for improving our ability to intervene when RBC production is perturbed in disease.

Development of gene therapy for blood disorders: an update

This review addresses the current status of gene therapy for immunodeficiencies, chronic granulomatous disease, suicide gene therapy for graft-versus-host disease, viral infections, malignant hematologic disorders, hemophilia, and the hemoglobin disorders. New developments in vector design have fostered improved expression as well as enhanced safety, particularly of integrating retroviral vectors. Several immunodeficiencies have been treated successfully by stem cell-targeted, retroviral-mediated gene transfer with reconstitution of the immune system following infusion of the transduced cells. In a trial for hemophilia B, long-term expression of human FIX has been observed following adeno-associated viral vector-mediated gene transfer into the liver. This approach should be successful in treating any disorder in which liver production of a specific protein is therapeutic.

Management of the thalassemias

During the last 30 years, in addition to the considerable progress made in control and prevention of thalassemias(3), there have also been major advances in their symptomatic management, at least in wealthier countries where appropriate facilities are available. Remarkable improvements in survival in the severe forms of thalassemia have followed the more judicious use of blood transfusion and, in particular, the ability to manage the iron accumulation resulting from transfusion with its severe and ultimately lethal effects on endocrine and cardiac function.