The complex, confusing and poorly understood immune responses to AAV-mediated gene transfer in haemophilia-Is more or less immunosuppression required?

Attempts to achieve a functional cure or amelioration of the severe X linked bleeding disorders haemophilia A (factor VIII deficiency) and haemophilia B (factor IX deficiency) using AAV-based vectors have been frustrated by immune responses that limit efficacy and durability. The immune responses include adaptive and innate pathways as well as cytokine mediated inflammation, especially of the target organ cells-hepatocytes. Immune suppression has only been partly effective in clinical trials at ameliorating the immune response and the lack of good animal models has delayed progress in identifying mechanisms and developing more effective approaches to controlling these effects of AAV gene transfer. Here we discuss the arguments for and against more potent immunosuppression to improve factor expression after AAV-mediated gene therapy.

The benefits of gene therapy in people with haemophilia.

Haemophilia is an inherited bleeding disorder which causes significant morbidity and mortality, especially in the severe form. Prophylaxis with factor replacement has high efficacy in reducing bleeding but is limited by the need for frequent intravenous infusion and fluctuations in haemostasis between doses. Additional prophylaxis therapies are being developed which may overcome some of the current treatment barriers. Gene therapy (GT) is being developed to provide a functional cure such that there is sustained factor expression and minimal to no need for additional haemostatic therapy. There are now two approved gene therapies for haemophilia which may be transformative for many individuals. Benefits of GT should go beyond increasing factor activity and reducing bleeding as persons with haemophilia aim to achieve a 'haemophilia-free mind' and health equity with optimal health and well-being.

Monitoring for liver cancer post-gene therapy-How much and how often?

Hepatocellular carcinoma (HCC) has long been recognized as a complication in people with chronic liver disease, particularly those with cirrhosis. Two gene therapies for haemophilia A and B recently approved in Europe and the US utilize adeno-associated virus (AAV) vectors designed to target hepatocytes. A number of other AAV gene therapies are undergoing clinical investigation for both liver and extrahepatic diseases, many of which likely transduce hepatocytes as well. Although AAV vectors predominantly persist in episomal forms, concerns about insertional mutagenesis have arisen due to findings in pre-clinical models and in a small subset of human HCC cases featuring wild-type AAV integrations in proximity to potential oncogenes. Despite the absence of any causative link between AAV vector therapy and HCC in approved extrahepatic gene therapies or haemophilia gene therapy trials, the package inserts for the recently approved haemophilia gene therapies advise HCC screening in subsets of individuals with additional risk factors. In this review, we discuss HCC risk factors, compare various screening modalities, discuss optimal screening intervals, and consider when to initiate and possibly discontinue screening. At this early point in the evolution of gene therapy, we lack sufficient data to make evidence-based recommendations on HCC screening. While AAV vectors may eventually be shown to be unassociated with risk of HCC, we presently favour a cautious approach that entails regular surveillance until such time as it is hopefully proven to be unnecessary.

Which patients should be considered for gene therapy.

Gene therapy for haemophilia, utilizing adeno-associated viral vectors (AAVs) and coagulation factor genes, have demonstrated promising results, leading to recent approvals and introduction of the first gene therapy products into clinical practice. For successful and safe use, there are predefined inclusion and exclusion criteria, and the treatment process and associated risks should be thoroughly understood and long-term safety and efficacy carefully evaluated during follow up. As gene therapy becomes more accessible outside of clinical study centers, continuous evaluation of patient eligibility for subsequent AAV-based treatments becomes essential. Thorough evaluation of factors such as liver condition, anti-AAV status, and medical history ensures that gene therapy maximizing benefits while minimizing risks. Apart from fulfilling the established inclusion and exclusion criteria, the success of gene therapy is greatly influenced by the motivation and willingness of patients to accept temporary constraints, such as regular laboratory monitoring, potential use of immunosuppressants, and thorough documentation. Furthermore, various patient-related factors play a significant role in the management and outcomes of gene therapy, making a comprehensive evaluation essential. With the accumulation of more data, there is potential for the expansion of certain inclusion criteria, which may allow for a larger number of eligible patients to benefit from gene therapy. Empowering patients through shared decision-making enables them to thoroughly consider the therapy's potential benefits and risks.

Hepatitis after gene therapy, what are the possible causes?

Hepatitis is a common adverse event following gene therapy for haemophilia, often associated with a loss of transgene expression. Investigating the potential causes and implications of this is crucial for the overall success of treatment. Gene therapy trials using adeno-associated virus (AAV) vectors have demonstrated promising results marked by increases in factor FVIII and FIX levels and reductions in episodes of bleeding. However, hepatocellular injury characterised by elevations in alanine aminotransferases (ALT) has been noted. This liver injury is typically transient and asymptomatic, posing challenges in determining its clinical significance. Proposed causes encompass immune-mediated responses, notably T cell cytotoxicity in response to the AAV vector, direct liver injury from the viral capsid or transcribed protein via the unfolded protein response and pre-existing liver conditions. Liver biopsy data conducted years post-gene therapy infusion has shown sinusoidal infiltration without significant inflammation. The overall safety profile of gene therapy remains favourable with no evidence drug-induced liver injury (DILI) based on Hy's Law criteria. Essential pre-therapy monitoring and identifying patients at high risk of liver injury should involve liver function tests and non-invasive fibroscans, while novel blood-based biomarkers are under exploration. Further research is required to comprehend the mechanisms underlying transaminitis, loss of transgene expression and long-term effects on the liver, providing insights for optimising gene therapy for haemophilia.

Hemophilia B and gene therapy: a new chapter with etranacogene dezaparvovec.

ABSTRACT: The US Food and Drug Administration (FDA)'s authorization of etranacogene dezaparvovec (Hemgenix) is a significant milestone, constituting not only the first FDA approval of a gene therapy for hemophilia but also the first approval of a liver-targeted adeno-associated virus vector gene therapy. This review summarizes the nonclinical studies and clinical development that supported regulatory clearance. Similar to other gene therapies for single gene disorders, both the short-term safety and the phenotypic improvement were unequivocal, justifying the modest-sized safety and efficacy database, which included 57 participants across the phase 2b (3 participants) and phase 3 (54 participants) studies. The most common adverse reactions included liver enzyme elevation, headache, flu-like symptoms, infusion-related reactions, creatine kinase elevation, malaise, and fatigue; these were mostly transient. One participant had hepatocellular carcinoma on a study-mandated liver ultrasound conducted 1 year after vector infusion; molecular analysis of the resected tumor showed no evidence of vector-related insertional mutagenesis as the etiology. A remarkable 96% of participants in the phase 3 trial were able to stop factor IX (FIX) prophylaxis, with the study demonstrating noninferiority to FIX prophylaxis in terms of the primary end point, annualized bleeding rate. Key secondary end points such as the annualized infusion rate, which declined by 97%, and the plasma FIX activity level at 18 months after infusion, with least squares mean increase of 34.3 percentage points compared with baseline, were both clinically and statistically significant. The FDA's landmark approval of Hemgenix as a pioneering treatment for hemophilia stands on the shoulders of >20 years of gene therapy clinical research and heralds a promising future for genomic medicines.

[Methodological recommendations for surgical care in patients with hemophilia A receiving prophylactic therapy with emicizumab]. / Metodicheskie rekomendatsii po okazaniyu khirurgicheskoi pomoshchi u patsientov s gemofiliei A, poluchayushchikh profilakticheskuyu terapiyu emitsizumabom.

Methodological recommendations for surgical care in patients with hemophilia A receiving prophylactic therapy with emicizumab. Recommendations of the expert group. Moscow, 2024.

Paradox pain sensitivity using cuff pressure or algometer testing in patients with hemophilia.

INTRODUCTION: Pain is a common comorbidity in patients with hemophilia (PwH) due to hemophilic arthropathy. This study aims to explore pain sensitivity in PwH methodologically investigating in cuff pressure testing compared to algometer testing. METHODS: 37 PwH and 35 healthy control subjects (Con) enrolled in this study. Joint health status was assessed. Subjective pain was evaluated using numeric rating scales. Pain sensitivity was measured with pressure algometry and cuff pressure algometry. Pressure pain thresholds of the algometer (PPTa) were measured at knee, ankle joints, and forehead. Subsequently, thresholds of cuff pressure were measured at the left and right lower legs (PPTcuff). In both, lower values represent higher pain sensitivity. RESULTS: PwH exerted a worse joint health status than Con. Pain sensitivity was higher in PwH compared to Con as PPTa of the knee and ankle joints were lower in PwH. No difference was observed in PPTa at the forehead. Contrastingly, lower pain sensitivity was detected in PwH by higher PPTcuff values compared to Con in both legs. CONCLUSION: While PPTa of the knee and ankle joints are lower in PwH, PPTcuff are higher in PwH compared to Con. This reveals a paradox situation, highlighting that PwH experience local, joint- and hemophilic arthropathy-related pain, whereas pain sensitivity of non-affected soft tissue structures is lower. The reasons explaining the PPTcuff results remain elusive but might be explained by coping strategies counteracting chronic joint pain, resulting in lower sensitivity at non-affected structures.

Assessment of jaw bone mineral density, resorption rates, and oral health in patients with severe hemophilia: a case-control study.

OBJECTIVE: Knowledge about oral hygiene, gingival bleeding, mineral density, and resorption of jaw bones in patients with hemophilia is limited. We evaluated the periodontal and bone status in such patients.  Material and methods: Forty-eight patients with severe type A/B hemophilia and 49 age- and sex-matched controls were included. Assessments included simplified oral hygiene index (OHI-S), calculus index, debris index, gingival index (GI), gingival bleeding time index (GBTI), and decayed, missing, and filled teeth index (DMFTI). Bone resorption was evaluated using panoramic mandibular index (PMI), mental index (MI), and alveolar crest ratio (ACR). Mineral density in the condyle, angulus, and premolar areas was assessed using fractal analysis, with fractal dimensions denoted as condyle fractal dimension (CFD) for the condyle, angulus fractal dimension (AFD) for angulus, and premolar fractal dimension (PFD) for premolar region. RESULTS: The mean scores were DMFTI = 11.77, OHI-S = 2.44, PMI = 0.268, MI = 5.822, GI = 3.02, GBTI = 2.64, ACR = 2.06, CFD = 1.31, AFD = 1.31, and PFD = 1.17 in the hemophilia group and DMFTI = 11.449, PMI = 0.494, MI = 7.43, GI = 0.67, GBTI = 0.98, OHI-S = 1.45, ACR = 2.87, CFD = 1.35, AFD = 1.35, and PDF = 1.23 in the control group. Differences were significant for all parameters (p < 0.005) except for the DMFTI index.  Conclusions: Because of poor oral hygiene, high bone resorption, and low bone mineral density in these patients, clinicians should consider potential bone changes when planning to treat these patients.

Clinical Analysis and Mental Health Survey of Hemophilia Carriers: a Cross-sectional Study.

OBJECTIVE: Hemophilia carriers (HCs), who are heterozygous for mutations in the clotting factor VIII/clotting factor IX gene (F8 or F9), may have a wide range of clotting factor levels, from very low, similar to afflicted males, to the upper limit of normal, and may experience mental health issues. The purpose of this study was to provide genetic information on mothers of hemophilia patients and to understand the clotting factor activity and phenotype of HCs. Additionally, we aimed to investigate the mental health status of HCs in China. METHODS: A total of 127 hemophilia mothers, including 93 hemophilia A (HA) mothers and 34 hemophilia B (HB) mothers, were enrolled in this study. Long distance PCR, multiplex PCR, and Sanger sequencing were used to analyze mutations in F8 or F9. Coagulation factor activity was detected by a one-stage clotting assay. The Symptom Checklist 90 (SCL-90, China/Mandarin version) was given to HCs at the same time to assess their mental health. RESULTS: A total of 90.6% of hemophilia mothers were diagnosed genetically as carriers, with inversion in intron 22 and missense mutations being the most common mutation types in HA and HB carriers, respectively. The median clotting factor level in carriers was 0.74 IU/mL (ranging from 0.09 to 1.74 IU/mL) compared with 1.49 IU/mL (ranging from 0.93 to 1.89 IU/mL) in noncarriers, of which 14.3% of HCs had clotting factor levels of 0.40 IU/mL or below. A total of 53.8% (7/13) of HA carriers with low clotting factor levels (less than 0.50 IU/mL) had a history of bleeding, while none of the HB carriers displayed a bleeding phenotype. The total mean score and the global severity index of the SCL-90 for surveyed HCs were 171.00 (±60.37) and 1.78 (±0.59), respectively. A total of 67.7% of the respondents had psychological symptoms, with obsessive-compulsive disorder being the most prevalent and severe. The pooled estimates of all nine factors were significantly higher than those in the general population (P<0.05). CONCLUSIONS: The detection rate of gene mutations in hemophilia mothers was 90.6%, with a median clotting factor level of 0.74 IU/mL, and 14.3% of HCs had a clotting factor level of 0.40 IU/mL or below. A history of bleeding was present in 41.2% of HCs with low clotting factor levels (less than 0.50 IU/mL). Additionally, given the fragile mental health status of HCs in China, it is critical to develop efficient strategies to improve psychological well-being.

Acquired bleeding disorders.

Acquired bleeding disorders can develop in previously healthy people irrespective of age or gender but are particularly common in patients with certain underlying conditions. Here, we review recent advances in the management of acquired haemophilia A (AHA), acquired von Willebrand syndrome (AVWS), and patients with hemostatic abnormalities due to chronic liver disease (CLD). Patients with AHA can now benefit from prophylaxis with emicizumab, a therapeutic antibody that mimics the function of activated coagulation factor VIII. The treatment of AVWS remains challenging in many situations and requires careful consideration of the underlying condition. Haemostatic abnormalities in CLD are often compensated by proportional reduction in pro and anti-haemostatic factors resulting in sustained or even increased thrombin generation. Consequently, bleeding in CLD is rarely caused by haemostatic failure and infusion of plasma or coagulation factor concentrates may not be effective.

The importance and evolution of bleeding disorder registries.

Registries are excellent sources of data to address questions that are typically not evaluated in randomized clinical trials, including natural history, disease prevalence, treatment approaches and adverse events, and models of care. Global and regional registries can provide data to identify differences in outcomes and in haemophilia care between countries, economic settings, and regions, while facilitating research and data sharing. In this manuscript, we highlight five bleeding disorder registries: Country registries from Australia and China, Paediatric Network on Haemophilia Management (PedNet) data on children who have received emicizumab, data from the European Haemophilia Safety Surveillance (EUHASS) system, and data on women and girls with haemophilia from the World Federation of Haemophilia (WFH) registries. Data from these and other bleeding disorder registries have been and will continue to be used to advance patient care, understand treatment patterns and adverse reactions, and identify areas of increased need and focus.

Unresolved hemostasis issues in haemophilia.

Despite rapid technological advancement in factor and nonfactor products in the prevention and treatment of bleeding in haemophilia patients, it is imperative that we acknowledge gaps in our understanding of how hemostasis is achieved. The authors will briefly review three unresolved issues in persons with haemophilia (PwH) focusing on the forgotten function that red blood cells play in hemostasis, the critical role of extravascular (outside circulation) FIX in hemostasis in the context of unmodified and extended half-life FIX products and finally on the role that skeletal muscle myosin plays in prothrombinase assembly and subsequent thrombin generation that could mitigate breakthrough muscle hematomas.

Haemophilic arthropathy: Diagnosis, management, and aging patient considerations.

Gene therapy and universal use of safer, more effective, and personalised prophylactic regimens (factor, and nonfactor) are expected to prevent joint bleeding and promote joint health in persons with haemophilia (PwH). Growing evidence suggests that subclinical bleeding, with active and inactive synovial proliferation, continues and haemophilic arthropathy remains a major morbidity in PwH despite early institution of joint prophylaxis. Joint health assessment is evolving with physical examination scores complementing imaging scores. Point-of-care ultrasound is emerging as a safe, cost-effective, and readily available tool for acute determination of musculoskeletal abnormalities, serial evaluation of joints for sonographic markers of haemophilic arthropathy, and in providing objective insight into the efficacy of new therapies. In acute haemarthrosis, arthrocentesis expedites recovery and prevent the vicious cycle of bleed-synovitis-rebleed. When synovial proliferation develops, a multidisciplinary team approach is critical with haematology, orthopaedics, and physiotherapy involvement. Synovectomy is considered for patients with chronic synovitis that fail conservative management. Non-surgical and minimally invasive procedures should always be offered and considered first. Careful patient selection, screening and early intervention increase the success of these interventions in reducing bleeding, pain, and improving joint function and quality of life. Chemical synovectomy is practical in developing countries, but radioactive synovectomy appears to be more effective. When surgical synovectomy is considered, arthroscopic/minimally invasive approach should be attempted first. In advanced haemophilic arthropathy, joint replacement and arthrodesis can be considered. While excited about the future of haemophilia management, navigating musculoskeletal challenges in the aging haemophilia population is equally important.

Identification of the Efficient Enhancer Elements in FVIII-Padua for Gene Therapy Study of Hemophilia A.

Hemophilia A (HA) is a common X-linked recessive hereditary bleeding disorder. Coagulation factor VIII (FVIII) is insufficient in patients with HA due to the mutations in the F8 gene. The restoration of plasma levels of FVIII via both recombinant B-domain-deleted FVIII (BDD-FVIII) and B-domain-deleted F8 (BDDF8) transgenes was proven to be helpful. FVIII-Padua is a 23.4 kb tandem repeat mutation in the F8 associated with a high F8 gene expression and thrombogenesis. Here we screened a core enhancer element in FVIII-Padua for improving the F8 expression. In detail, we identified a 400 bp efficient enhancer element, C400, in FVIII-Padua for the first time. The core enhancer C400 extensively improved the transcription of BDDF8 driven by human elongation factor-1 alpha in HepG2, HeLa, HEK-293T and induced pluripotent stem cells (iPSCs) with different genetic backgrounds, as well as iPSCs-derived endothelial progenitor cells (iEPCs) and iPSCs-derived mesenchymal stem cells (iMSCs). The expression of FVIII protein was increased by C400, especially in iEPCs. Our research provides a novel molecular target to enhance expression of FVIII protein, which has scientific value and application prospects in both viral and nonviral HA gene therapy strategies.

Hemophilia and hepatology, back to the future.

Years ago, patients with hemophilia were often cared for because of liver issues. The use of hemoderivatives in the 1970s and 1980s, and the natural history of chronic hepatitis B and C, led to a surge of patients with cirrhosis and related complications after two or three decades. It was not until the approval of entecavir and tenofovir (2005-2008) against the B virus, and of direct-acting antiviral agents (2015) against the C virus, that a truly effective treatment became available for liver disease. Since then, patients with hemophilia disappeared from hepatology clinics and wards, apart from specific isolated problems.