Cellular stress and coagulation factor production: when more is not necessarily better

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.

Cell-Based Small-Molecule Screening Identifying Proteostasis Regulators Enhancing Factor VIII Missense Mutant Secretion

Missense mutations are the most prevalent alterations in genetic disorders such as hemophilia A (HA), which results from coagulation factor VIII (FVIII) deficiencies. These mutations disrupt protein biosynthesis, folding, secretion, and function. Current treatments for HA are extremely expensive and inconvenient for patients. Small molecule drugs offer a promising alternative or adjunctive strategy due to their lower cost and ease of administration, enhancing accessibility and patient compliance. By screening drug/chemical libraries with cells stably expressing FVIII-Gaussia luciferase fusion proteins, we identified compounds that enhance FVIII secretion and activity. Among these, suberoylanilide hydroxamic acid (SAHA) improved the secretion and activity of wild-type FVIII and common HA-associated missense mutants, especially mild and moderate ones. SAHA increased FVIII interaction with the endoplasmic reticulum chaperone BiP/GRP78 but not with calreticulin. Lowering cellular BiP levels decreased SAHA-induced FVIII secretion and enhancing BiP expression increased FVIII secretion. SAHA also enhanced secretion and BiP interactions with individual domains of FVIII. In vivo, treating mice with SAHA or a BiP activator boosted endogenous FVIII activity. These findings suggest that SAHA serves as a proteostasis regulator, providing a novel therapeutic approach to improve the secretion and functionality of FVIII missense mutants prone to misfolding.

Lentiviral Gene Therapy with CD34+ Hematopoietic Cells for Hemophilia A

BACKGROUND

Severe hemophilia A is managed with factor VIII replacement or hemostatic products that stop or prevent bleeding. Data on gene therapy with hematopoietic stem-cell (HSC)-based expression of factor VIII for the treatment of severe hemophilia A are lacking.

METHODS

We conducted a single-center study involving five participants 22 to 41 years of age with severe hemophilia A without factor VIII inhibitors. Autologous HSCs were transduced with CD68-ET3-LV - a lentiviral vector including a new F8 transgene (ET3) with a myeloid-directed CD68 promoter - either without transduction enhancer (group 1) or with transduction enhancer (group 2). Transduced HSCs were transplanted into recipients after myeloablative conditioning. The treatment was assessed for safety (engraftment and regimen-related toxic effects) and efficacy (factor VIII activity and annualized bleeding rate).

RESULTS

Participants received CD68-ET3-LV-transduced autologous CD34+ HSCs at doses of 5.0×106 to 6.1×106 per kilogram of body weight. The vector copy numbers in the final drug product were 1.0 and 0.6 copies per cell for the two participants in group 1 and 1.5, 0.6, and 2.2 copies per cell for the three participants in group 2. The duration of severe neutropenia was 7 to 11 days and of severe thrombocytopenia was 1 to 7 days. The median factor VIII activity level, measured with the use of a one-stage assay, after day 28 until the last follow-up visit was 5.2 IU per deciliter (range, 3.0 to 8.7) and 1.7 IU per deciliter (range, 1.0 to 4.0) with a peripheral-blood vector copy number of 0.2 and 0.1 copies per cell, respectively, in the two group 1 participants, and 37.1 IU per deciliter (range, 18.3 to 73.6), 19.3 IU per deciliter (range, 6.6 to 34.5), and 39.9 IU per deciliter (range, 20.6 to 55.1) with a peripheral-blood vector copy number of 4.4, 3.2, and 4.8 copies per cell, respectively, in the three group 2 participants. The annualized bleeding rate was zero for all five participants over a cumulative follow-up of 81 months (median follow-up, 14 months; range, 9 to 27).

CONCLUSIONS

Gene therapy for hemophilia A with the use of lentiviral vector-transduced autologous HSCs resulted in stable factor VIII expression, with factor VIII activity correlating to vector copy number in the peripheral blood. (Funded by the Ministry of Science and Technology, Government of India, and others; ClinicalTrials.gov number, NCT05265767; Clinical Trials Registry-India number, CTRI/2022/03/041304.).

The management of liver disease in people with congenital bleeding disorders: guidance from European Association for Haemophilia and Allied Disorders, European Haemophilia Consortium, ISTH, and World Federation of Hemophilia

People with bleeding disorders (PWBD) have been exposed to the risk of developing chronic viral hepatitis and cirrhosis after replacement therapy. Today, the advent of new pharmacologic strategies for the control of hemostasis and the efficacious antiviral therapies against hepatitis C virus and hepatitis B virus have significantly reduced this risk. However, the definitive success for liver health in this clinical setting is also influenced by other factors, such as the severity of liver disease at the time of hepatitis B virus/hepatitis C virus antiviral therapy and the exposure to highly prevalent factors of chronic liver damage (eg, metabolic dysfunction and/or alcohol) that can cause a residual risk of complications such as hepatocellular carcinoma, portal hypertension, and liver insufficiency. With this background, a group of experts selected among hepatologists, hematologists, PWBD treaters, and patient representatives produced this practical multisociety guidance for the protection of liver health and the prevention and management of liver complications in PWBD based on the most updated protocols of care.

Roctavian gene therapy for hemophilia A

ABSTRACT

After successful efforts in adeno-associated virus (AAV) gene addition for hemophilia B gene therapy, the development of valoctocogene roxaparvovec (Roctavian; Biomarin) over the past decade represents a potential new hemophilia A (HA) treatment paradigm. Roctavian is the first licensed HA gene therapy that was conditionally approved in Europe in August 2022 and approved in the United States in June 2023. Beyond Roctavian, there are ongoing pivotal trials of additional AAV vectors for HA, others that are progressing through preclinical development or early-phase clinical trial, as well as non-AAV approaches in clinical development. This review focuses on the clinical development of Roctavian for which the collective clinical trials represent the largest body of work thus far available for any licensed AAV product. From this pioneering clinical development, several outstanding questions have emerged for which the answers will undoubtedly be important to the clinical adaptation of Roctavian and future efforts in HA gene therapy. Most notably, unexplained year-over-year declines in factor VIII (FVIII) expression after Roctavian treatment contrast with stable FVIII expression observed in other AAV HA gene therapy clinical trials with more modest initial FVIII expression. This observation has been qualitatively replicated in animal models that may permit mechanistic study. The development and approval of Roctavian is a landmark in HA therapeutics, although next-generation approaches are needed before HA gene therapy fulfills its promise of stable FVIII expression that normalizes hemostasis.

A novel risk stratification approach and molecular subgroup characterization based on coagulation related genes in colon adenocarcinoma

Colon adenocarcinoma (COAD) represents a significant health concern within the population. Advancing our understanding of COAD is imperative for early detection, enabling personalized treatment interventions, and facilitating the development of effective preventive measures. The coagulation system plays a role in tumor-related pathological processes; however, its specific involvement in COAD and potential contributors remain unclear. This study aimed to establish a novel risk stratification approach by analyzing coagulation related genes (CRGs) associated with COAD. Through a comprehensive bioinformatics analysis of data from public databases, we screened COAD associated CRGs and characterized the associated molecular subtypes. After a comprehensive analysis of the characteristics of each subtype, we applied differentially expressed genes in CRG subtypes to establish a new risk stratification method. Clinical subgroup analysis, immunoinfiltration analysis, therapeutic reactivity prediction and other analytical methods suggest the potential clinical value of the established risk stratification method. As one of the selected targets, the effect of MS4A4A on the proliferation and invasion of COAD was confirmed by in vitro experiments, which partially verified the reliability of bioinformatics results. Our findings delineate CRGs potentially implicated in COAD pathogenesis and offer fresh insights into the influence of the coagulation process on tumorigenesis and progression.

Liver health in hemophilia in the era of gene therapy

Gene therapy for hemophilia is a groundbreaking treatment approach with promising results and potential to reduce the burden of the disease. However, uncertainties remain, particularly regarding the liver side effects of AAV gene therapy, which are more common in hemophilia A. Unlike some other diseases, such as spinal muscular atrophy, where the target cell for gene therapy is different from the one affected by side effects, hemophilia gene therapy operates within the same cellular domain-the hepatocyte. This overlap is challenging and requires a targeted strategy to mitigate the risks associated with liver injury, which often requires temporary immunosuppressive therapy. A comprehensive approach is essential to increase the efficacy of gene therapy and reduce the likelihood of hepatocyte damage. Key components of this strategy include a thorough pre-gene therapy assessment of liver health, careful post-gene therapy liver monitoring, and prompt therapeutic intervention for loss of transgene expression and liver injury. Collaboration between hematologists and hepatologists is essential to ensure a well-coordinated management plan for patients undergoing hemophilia gene therapy. This review addresses the critical aspect of hepatic comorbidities in patients with hemophilia, emphasizing the need to identify and address these issues prior to initiating gene therapy. It examines the known mechanisms of liver damage and emphasizes the importance of liver monitoring after gene therapy. In addition, the review draws insights from experiences with other AAV-based gene therapies, providing valuable lessons that can guide hemophilia centers in effectively managing liver damage associated with hemophilia gene therapy.

Current and emerging gene therapies for haemophilia A and B

INTRODUCTION

After decades of stumbling clinical development, the first gene therapies for haemophilia A and B have been commercialized and have normalized factor (F)VIII and factor (F)IX levels in some individuals in the long term. Several other clinical programs testing adeno-associated viral (AAV) vector gene therapy are at various stages of clinical testing.

DISCUSSION

Multiyear follow-up in phase 1/2 and 3 studies showed long-term and sometimes curative but widely variable and unpredictable efficacy. Liver toxicities, mostly low-grade, occur in the 1st year in at least some individuals in all haemophilia A and B trials and are poorly understood. Wide variability and unpredictability of outcome and slow decline of FVIII levels are a major disadvantage because immune responses to AAV vectors preclude repeat dosing, which otherwise could improve suboptimal or restore declining expression, while overexpression may predispose to thrombosis. Long-term safety outcomes will need lifelong monitoring because AAV vectors infused at high doses integrate into chromosomes at rates that raise questions about potential oncogenicity and necessitate vigilance. Alternative gene transfer systems employing gene editing and/or non-viral vectors are under development and promise to overcome some limitations of the current state of the art for both haemophilia A and B.

CONCLUSIONS

AAV gene therapies for haemophilia have now become new treatment options but not universal cures. AAV is a powerful but imperfect gene transfer platform. Biobetter FVIII transgenes may help solve some problems plaguing gene therapy for haemophilia A. Addressing variability and unpredictability of efficacy, and delivery of gene therapy to ineligible patient subgroups may require different gene transfer systems, most of which are not ready for clinical translation yet but bring innovations needed to overcome the current limitations of gene therapy.