A plethora of gene therapies for hemoglobinopathies

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.

A landscape analysis and discussion of value of gene therapies for sickle cell disease

INTRODUCTION

Sickle cell disease (SCD) is a rare genetic disease with limited therapeutic options. Gene-based therapies are being investigated in clinical trials to evaluate their curative potential. The expected life-long benefits of one-time administration of genetically corrected stem cells present uncharted challenges in estimating value of these treatments. Our objective is to conduct a landscape analysis of clinical trials and prompt a discussion estimating the value of gene therapy as a therapeutic option for SCD.

AREAS COVERED

We searched Clinicaltrials.gov to identify and characterize clinical trials in gene therapies for SCD. We report available results and discuss current concerns and elements of value necessary to consider as these products come to market.

EXPERT OPINION

Gene therapies could represent a major advance in SCD treatment. Although clinical trials are ongoing, reports of serious adverse events have led to pause of these trials, emphasizing the need to prove long-term tolerability. Measured using the methods of health economic evaluation, we anticipate high up-front costs may be offset by potential life-long benefits of these treatments. During development and after treatment approval, attention should be focused on ensuring adequate availability and equitable access to emerging therapies in underserved areas and low-middle-income countries (LMIC).

Understanding and overcoming adverse consequences of genome editing on hematopoietic stem and progenitor cells

Hematopoietic stem and progenitor cell (HSPC) gene therapies have recently moved beyond gene-addition approaches to encompass targeted genome modification or correction, based on the development of zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and CRISPR-Cas technologies. Advances in ex vivo HSPC manipulation techniques have greatly improved HSPC susceptibility to genetic modification. Targeted gene-editing techniques enable precise modifications at desired genomic sites. Numerous preclinical studies have already demonstrated the therapeutic potential of gene therapies based on targeted editing. However, several significant hurdles related to adverse consequences of gene editing on HSPC function and genomic integrity remain before broad clinical potential can be realized. This review summarizes the status of HSPC gene editing, focusing on efficiency, genomic integrity, and long-term engraftment ability related to available genetic editing platforms and HSPC delivery methods. The response of long-term engrafting HSPCs to nuclease-mediated DNA breaks, with activation of p53, is a significant challenge, as are activation of innate and adaptive immune responses to editing components. Lastly, we propose alternative strategies that can overcome current hurdles to HSPC editing at various stages from cell collection to transplantation to facilitate successful clinical applications.

Innovative Treatments for Rare Anemias

Rare anemias (RA) are mostly hereditary disorders with low prevalence and a broad spectrum of clinical severity, affecting different stages of erythropoiesis or red blood cell components. RA often remains underdiagnosed or misdiagnosed, and treatment options have been limited to supportive care for many years. During the last decades, the elucidation of the molecular mechanisms underlying several RA paved the way for developing new treatments. Innovative treatments other than supportive care and allogeneic bone marrow transplantation are currently in clinical trials for β-thalassemias, sickle cell disease (SCD), and congenital hemolytic anemias. Recently, luspatercept, an activin receptor ligand trap targeting ineffective erythropoiesis, has been approved as the first pharmacological treatment for transfusion-dependent β-thalassemia. L-glutamine, voxelotor, and crizanlizumab are new drugs approved SCD, targeting different steps of the complex pathophysiological mechanism. Gene therapy represents an innovative and encouraging strategy currently under evaluation in several RA and recently approved for β-thalassemia. Moreover, the advent of gene-editing technologies represents an additional option, mainly focused on correcting the defective gene or editing the expression of genes that regulate fetal hemoglobin synthesis. In this review, we aim to update the status of innovative treatments and the ongoing trials and discuss RA treatments’ future directions. Interestingly, several molecules that showed promising results for treating one of these disorders are now under evaluation in the others. In the near future, the management of RA will probably consist of polypharmacotherapy tailored to patients’ characteristics.