Delivery of gene therapy in haemophilia treatment centres in the United States: Practical aspects of preparedness and implementation

Gene therapy for hemophilia - From basic science to first approvals of "one-and-done" therapies

Realistic paths to gene therapy for the X-linked bleeding disorder hemophilia started to materialize in the mid 1990s, resulting in disease correction in small and large animal models. Out of a diversity of approaches, in vivo adeno-associated viral (AAV) gene transfer to hepatocytes emerged as the most promising strategy, eventually forming the basis for multiple advanced clinical trials and regulatory approval of two products for the treatment of hemophilia B (coagulation factor IX deficiency) and one for hemophilia A (factor VIII deficiency). Ideally, gene therapy is effective with a single administration, thus providing therapeutic factor levels over a period of years, without the need for frequent injections. Overcoming multiple obstacles, some not predicted by preclinical studies, sustained partial to complete correction of coagulation for several years to an entire decade has now been documented in patients, with observation ongoing. A hyperactive form of FIX improved efficacy in hemophilia B, and superior engineered variants of FVIII are emerging. Nonetheless, challenges remain, including pre-existing immunity to AAV capsids, toxicities, inter-patient variability in response to treatment, and difficulty in obtaining durable therapeutic expression of FVIII. In alternative approaches, in vivo gene editing and ex vivo gene therapies targeting hemopoietic cells are in development.

Corticosteroid use to mitigate transaminitis-associated decline in FVIII levels following valoctocogene roxaparvovec gene therapy: clinical practice guidance

Valoctocogene roxaparvovec is the only factor VIII (FVIII) gene therapy currently approved for adults with severe hemophilia A in Europe and the USA. Elevated alanine transaminase (transaminitis) has been the most common adverse event observed during valoctocogene roxaparvovec clinical trials. Typically mild and transient, this marker of hepatocyte injury coincides, in some patients, with reduced FVIII levels and is generally managed with a reactive course of corticosteroids. An essential step in optimizing outcomes for patients who receive valoctocogene roxaparvovec is reviewing the extensive evidence currently available on this topic to determine practices for managing transaminitis, if it occurs. This forum article provides practical guidance based on the available clinical data and expert opinion for evaluating and managing transaminitis with corticosteroids to mitigate potential declines in FVIII activity levels in adults with severe hemophilia A who have received valoctocogene roxaparvovec.

Gene Therapy in Hemophilia A: Achievements, Challenges, and Perspectives

Strides in advancements of care of persons with hemophilia include development of long-acting factor replacement therapies, novel substitution and hemostatic rebalancing agents, and most recently approved gene therapy. Several decades of preclinical and clinical trials have led to development of adeno-associated viral (AAV) vector-mediated gene transfer for endogenous production of factor VIII (FVIII) in hemophilia A (HA). Only one gene therapy product for HA (valoctocogene roxaparvovec) has been approved by regulatory authorities. Results of valoctocogene roxaparvovec trial show significant improvement in bleeding rates and use of factor replacement therapy; however, sustainability and duration of response show variability with overall decline in FVIII expression over time. Further challenges include untoward adverse effects involving liver toxicity requiring immunosuppression and development of neutralizing antibodies to AAV vector rendering future doses ineffective. Real-life applicability of gene therapy for HA will require appropriate patient screening, infrastructure setup, long-term monitoring including data collection of patient-reported outcomes and innovative payment schemes. This review article highlights the success and development of HA gene therapy trials, challenges including adverse outcomes and variability of response, and perspectives on approach to gene therapy including shared decision-making and need for future strategies to overcome the several unmet needs.

Gene therapy in hemophilia: the dawn of a new era

Hemophilia A and B are hereditary bleeding disorders associated with the X chromosome, stemming from genetic defects in the coding of coagulation factor (F)VIII or FIX protein, leading to partial or complete deficiency. In the absence of effective prophylaxis, these deficiencies can result in irreversible joint damage, known as hemophilic arthropathy, and subsequent disability. Despite advancements in hemophilia treatment, individuals with severe forms of the disease continue to face a high risk of bleeding, particularly in instances of trauma or major surgical procedures. In such scenarios, it remains imperative to administer replacement or bypassing drugs, especially when inhibitors are present. Within this context, gene therapy emerges as a compelling alternative, ensuring sustained expression of the deficient factor at levels often surpassing current recommendations. Some studies report an effect lasting up to 8 years, contributing significantly to clinical improvement and enhancing the quality of life for patients. However, a comprehensive evaluation of this innovative therapy is essential, encompassing both its benefits and potential risks. It is crucial to undertake a multidisciplinary assessment, engage in thoughtful discussions with the patient, and closely monitor the therapy's effects and any eventual side effects of therapy. This approach aims to facilitate an informed and collaborative decision-making process, ultimately maximizing the benefits for each individual patient.

Gene therapy for people with hemophilia B: a proposed care delivery model in Italy

BACKGROUND

Gene therapy is designed to provide people with hemophilia B with a steady and elevated factor (F)IX activity, thereby strengthening protection and relieving the burden of frequent replacement therapy infusions. The European Medicines Agency has approved gene therapy for the severe and moderately severe forms of hemophilia B that uses the FIX-Padua variant (etranacogene dezaparvovec).

OBJECTIVES

The aim was to provide a document dedicated to hemophilia B gene therapy and give a comprehensive overview of the topic.

METHODS

An Italian group of experts in hemophilia carried out a narrative review of the literature and discussed during a virtual meeting several key aspects of the delivery of this treatment in Italy. The discussion covered the organizational model, the role of the multidisciplinary team, the laboratory surveillance, and the patient's journey, from the follow-up to the identification of safety issues and outcome measures.

RESULTS

This article highlights the need to follow the Hub and Spoke organizational model and sheds light on the role of each professional figure within the multidisciplinary teams to favor patient engagement, management, and retention. Moreover, this article stresses the need to perform laboratory tests for patient screening and follow-up and proposes a checklist to help patient identification. Finally, the needs of Italian hemophilia centers have been considered to ensure an efficient implementation of the care delivery model.

CONCLUSION

It is crucial to ensure that centers are appropriately organized, equipped, and trained to adequately select patients, deliver the gene therapy, and perform follow-up.