Understanding AAV vector immunogenicity: from particle to patient.

Gene therapy holds promise for patients with inherited monogenic disorders, cancer, and rare genetic diseases. Naturally occurring adeno-associated virus (AAV) offers a well-suited vehicle for clinical gene transfer due to its lack of significant clinical pathogenicity and amenability to be engineered to deliver therapeutic transgenes in a variety of cell types for long-term sustained expression. AAV has been bioengineered to produce recombinant AAV (rAAV) vectors for many gene therapies that are approved or in late-stage development. However, ongoing challenges hamper wider use of rAAV vector-mediated therapies. These include immunity against rAAV vectors, limited transgene packaging capacity, sub-optimal tissue transduction, potential risks of insertional mutagenesis and vector shedding. This review focuses on aspects of immunity against rAAV, mediated by anti-AAV neutralizing antibodies (NAbs) arising after natural exposure to AAVs or after rAAV vector administration. We provide an in-depth analysis of factors determining AAV seroprevalence and examine clinical approaches to managing anti-AAV NAbs pre- and post-vector administration. Methodologies used to quantify anti-AAV NAb levels and strategies to overcome pre-existing AAV immunity are also discussed. The broad adoption of rAAV vector-mediated gene therapies will require wider clinical appreciation of their current limitations and further research to mitigate their impact.

Real-World Amount of Clotting Factor Concentrates Dispensed and Annual Medical Expenditures for Japanese Patients with Hemophilia B.

Introduction: Until extended half-life (EHL) factor IX (FIX) concentrates became available in Japan in 2010, patients with hemophilia B received intravenous FIX replacement therapy with standard half-life (SHL) FIX concentrates. Purpose: To investigate the amount of factor dispensed and the associated medical expenditures for the treatment of hemophilia B in the real-world clinical setting in Japan. Methods: This retrospective study comprised patients with hemophilia B (N=197) who had filled prescriptions for FIX concentrates reported in Japan's Medical Data Vision database from 2015 to 2019. Patients were included if they had 2 or more prescriptions for the same FIX concentrates within the first 6 months of the study period and the interval between prescriptions was at least 2 weeks. Results: Since 2015, there was a decrease in the proportion of patients using SHL FIX concentrates and a corresponding increase in international units of dispensed EHL FIX concentrates. Median annualized dispensed dosages (IU/kg body weight) of EHL FIX concentrates were lower than for SHL concentrates for outpatient use only. Annual total health care expenditures per patient and annual expenditures for prescribed FIX concentrates increased each year during the study period. Following a switch from an SHL to an EHL concentrate, the median amount of prescribed FIX concentrate decreased slightly, although median total health care expenditures and FIX concentrate expenditures increased. Conclusion: In the real-world setting in Japan, medical expenditures and the proportion of patients prescribed EHL FIX concentrates for the treatment of hemophilia B have increased.

The impact of bleeding event frequency on health-related quality of life and work productivity outcomes in a European cohort of adults with haemophilia A: insights from the CHESS II study.

BACKGROUND: Haemophilia A carries a substantial healthcare burden, affecting health-related quality of life (HRQoL). The Cost of Haemophilia in Men: a Socioeconomic Survey II (CHESS II), a retrospective real-world study, characterised the burden of haemophilia and its impact on HRQoL and work productivity. The current analysis explored the impact of bleeding events on HRQoL and work productivity in Europe. This analysis focused on data collected from males aged 18 to 64 years with haemophilia A without inhibitors who were receiving replacement factor products or a monoclonal antibody and were not participating in a clinical trial at the time of study recruitment. Descriptive statistics were analysed using scores from EuroQoL's EQ-5D-5L index and EQ-VAS analogue scale and the Work Productivity and Activity Index Specific Health Problem (WPAI:SHP) percentage scores stratified by the number of annual bleeding events (ABs) 0, 1, 2, 3-4, or ≥ 5. RESULTS: Of 918 males with haemophilia A in CHESS II, 318 met inclusion criteria and had data available for HRQoL measures; mean age (SD) was 33.8 (12.1) years and 96% were White. Mean (SD) ABs of 2.7 (2.9) occurred over the preceding 12 months: 20% had 3 or 4 ABs; 17% had ≥ 5 ABs. Mean EQ-5D-5L index scores for patients with 0, 1, 2, 3-4, or ≥ 5 ABs were 0.92, 0.76, 0.76, 0.71, and 0.56, respectively. Mean (SD) EQ-VAS scores were 86.9 (13.6), with 0 ABs versus 69.5 (19.1) for 3 or 4 ABs and 61.2 (17.2) for ≥ 5 ABs. Mean percentage of overall work productivity loss on the WPAI:SHP questionnaire ranged from 9.70 to 0 ABs to 47.65 for ≥ 5 ABs. CONCLUSIONS: In this European sample of adult men with haemophilia A, HRQoL and work productivity scores were lower among those reporting more AB events. Bleeding burden appears to affect HRQoL and productivity; however, this cross-sectional analysis limits the ability to draw firm conclusions on causality.

Binding and neutralizing anti-AAV antibodies: Detection and implications for rAAV-mediated gene therapy.

Assessment of anti-adeno-associated virus (AAV) antibodies in patients prior to systemic gene therapy administration is an important consideration regarding efficacy and safety of the therapy. Approximately 30%-60% of individuals have pre-existing anti-AAV antibodies. Seroprevalence is impacted by multiple factors, including geography, age, capsid serotype, and assay type. Anti-AAV antibody assays typically measure (1) transduction inhibition by detecting the neutralizing capacity of antibodies and non-antibody neutralizing factors, or (2) total anti-capsid binding antibodies, regardless of neutralizing activity. Presently, there is a paucity of head-to-head data and standardized approaches associating assay results with clinical outcomes. In addition, establishing clinically relevant screening titer cutoffs is complex. Thus, meaningful comparisons across assays are nearly impossible. Although complex, establishing screening assays in routine clinical practice to identify patients with antibody levels that may impact favorable treatment outcomes is achievable for both transduction inhibition and total antibody assays. Formal regulatory approval of such assays as companion diagnostic tests will confirm their suitability for specific recombinant AAV gene therapies. This review covers current approaches to measure anti-AAV antibodies in patient plasma or serum, their potential impact on therapeutic safety and efficacy, and investigative strategies to mitigate the effects of pre-existing anti-AAV antibodies in patients.

How to assess, detect, and manage joint involvement in the era of transformational therapies: Role of point-of-care ultrasound.

BACKGROUND: Patients with haemophilia experience recurring hemarthroses, mainly involving knees, elbows and ankles, which lead to haemophilic arthropathy, the major chronic complication of haemophilia. With new approaches to haemophilia treatment leading to fewer joint bleeds and, in some cases, no bleeding events, assessing whether current outcome assessment tools provide adequate sensitivity and specificity for management and care of patients with haemophilia is needed. METHODS: An overview of current imaging tools for monitoring joint health, novel osteochondral damage and synovial proliferation biomarkers, and the relationship between assessments for functionality and imaging modalities is provided. Usefulness and sensitivity of point-of-care ultrasound (POCUS) to complement other assessments and use of ultrasound to monitor haemophilic arthropathy are also examined. RESULTS: This review provides rationale for haemophilia teams to move beyond traditional outcomes in joint imaging, as well as guidance and evidence on assessment of joint health for potential new treatment modalities, such as gene therapy. The role of POCUS in the existing paradigm for haemophilia care and management along with the use of ultrasound as a complement to other outcome assessment tools are also discussed. Finally, the clinical effects of subclinical bleeding on joint function are described, to motivate screening for synovial proliferation. CONCLUSION: POCUS can facilitate the early detection of joint damage and can monitor disease progression while providing insights into the efficacy of treatment regimens, and should be considered as an essential assessment tool for managing the care of patients with haemophilia.

Examining patient and professional perspectives in the UK for gene therapy in haemophilia.

INTRODUCTION: With the development of gene therapy for people with haemophilia (PWH), it is important to understand how people impacted by haemophilia (PIH) and clinicians prioritise haemophilia treatment attributes to support informed treatment decisions. OBJECTIVE: To examine the treatment attribute preferences of PIH and clinical experts in the United Kingdom (UK) and to develop a profile of gene therapy characteristics fit for use in future discrete choice experiments (DCEs). METHODS: Semi-structured interviews were conducted with PIH (n = 14) and clinical experts (n = 6) who ranked pre-defined treatment attributes by importance. Framework analysis was conducted to identify key themes and treatment attributes; points were allocated based on the rankings. Synthesis of results by a multidisciplinary group informed development of a profile of gene therapy characteristics for use in future research. RESULTS: Key themes identified by PIH and clinical experts included patient relevant features and the importance of 'informed decision making'. The six top-ranked treatment attributes were 'effect on factor level' (79 points), 'uncertainty regarding long-term risks' (57 points), 'impact on daily life' (41 points), 'frequency of monitoring' (33 points), 'impact on ability to participate in physical activity' (29 points), and 'uncertainty regarding long-term benefits' (28 points). The final treatment characteristics were categorised as therapeutic option, treatment effectiveness, safety concerns, impact on self-management and quality of life (role limitations). CONCLUSION: We identified several gene therapy characteristics important to PIH and clinicians in the UK. These characteristics will be used in a future DCE to further investigate patient preferences for gene therapy.

Estimating the Prevalence of Transthyretin Amyloid Cardiomyopathy in a Large In-Hospital Database in Japan.

INTRODUCTION: Transthyretin amyloid cardiomyopathy (ATTR-CM)-a debilitating, fatal disease resulting from the deposition of transthyretin (TTR) amyloid fibrils-can be hereditary due to mutations in the TTR gene (ATTRm) or wild type (ATTRwt). The global prevalence of ATTR-CM is largely unknown, although likely underestimated, with no formal epidemiological prevalence studies in Japan. This study aimed to estimate the prevalence of ATTR-CM in a large in-hospital database in Japan. METHODS: This was a retrospective, observational, cross-sectional study which utilized data from all adult patients (aged ≥ 20 years) in the hospital-based Japan Medical Data Vision (MDV) database from January 2010 to September 2018 to estimate the number of currently diagnosed ATTR-CM patients and describe their demographic and clinical characteristics and diagnostic modalities. ATTR-CM patients (ATTRwt and ATTRm) were identified using a range of diagnosis codes that were applied to create broad and narrow definitions of the disease. RESULTS: Over the 9 years of this study, there were 3255 (155.8 per million adult patients in the MDV database) to 3992 (191.1 per million) diagnoses of ATTRwt and 67 (3.2 per million) to 106 (5.1 per million) diagnoses of ATTRm in the MDV database (based on the narrow and broad definitions, respectively). There were 444 (21.2 per million) diagnoses of amyloid light-chain (AL) amyloidosis. Considering only those patients who were also diagnosed with heart failure, there were 1468 (70.3 per million) to 1798 (86.1 per million) diagnoses of ATTRwt and 50 (2.4 per million) to 61 (2.9 per million) diagnoses of ATTRm. Most ATTRwt patients (~ 90%) did not have a record of endomyocardial or abdominal wall biopsy, or of scintigram. CONCLUSION: This retrospective study provides an estimate of the number of patients diagnosed with ATTR-CM in a large in-hospital database in Japan over a period of 9 years. Improving awareness of disease prevalence may improve diagnosis and treatment. FUNDING: Pfizer.

Cell damage following carbon monoxide releasing molecule exposure: implications for therapeutic applications.

The cytoprotective properties of carbon monoxide (CO) gas and CO-releasing molecules (CORMs) are well established. Despite promising pre-clinical results, little attention has been paid to the toxicological profile of CORMs. The effects of CORM-2 and its CO-depleted molecule (iCORM-2) (20-400 µM) were compared in primary rat cardiomyocytes and two cell lines [human embryonic kidney (HeK) and Madine-Darby canine kidney Cells (MDCK)]. Cells were assessed for cell viability, apoptosis, necrosis, cytology, mitochondrial energetics, oxidative stress and cell cycle arrest markers. In separate experiments, the anti-apoptotic effects of CORM-2 and i-CORM-2 treatment were compared against CO gas treatment in HeK and MDCK lines. H(2)O(2) -induced cellular damage, measured by lactate dehydrogenase (LDH) release from primary cardiomyocytes, was reduced by 20 µM CORM-2; LDH activity, however, was directly inhibited by 400 µM CORM-2. Both CORM-2/iCORM-2 and CO gas decreased cisplatin-induced caspase-3 activity in MDCK and HeK cells suggesting an anti-apoptotic effect. Conversely, both CORM-2 and iCORM-2 induced significant cellular toxicity in the form of decreased cell viability, abnormal cell cytology, increased apoptosis and necrosis, cell cycle arrest and reduced mitochondrial enzyme activity. Comparison of these markers after CO gas administration to MDCK cells found significantly less cellular toxicity than in 100 µM CORM-2/iCORM-2-treated cells. CO gas did not have an adverse effect on mitochondrial energetics and integrity. Release of CO by low concentrations of intact CORM-2 molecules provides cytoprotective effects. These results show, however, that the ruthenium-based CORM by-product, iCORM-2, is cytotoxic and suggest that the accumulation of iCORM-2 would seriously limit any clinical application of the ruthenium-based CORMs.

Tin protoporphyrin provides protection following cerebral hypoxia-ischemia: involvement of alternative pathways.

The contribution of heme oxygenase (HO)-linked pathways to neurodegeneration following cerebral hypoxia-ischemia (HI) remains unclear. We investigated whether HO modulators affected HI-induced brain damage and explored potential mechanisms involved. HI was induced in 26-day-old male Wistar rats by left common carotid artery ligation, followed by exposure to a humidified atmosphere of 8% oxygen for 1 hr. Tin protoporphyrin (SnPP; an HO inhibitor), ferriprotoporphyrin (FePP; an HO inducer), or saline was administered intraperitoneally once daily from 1 day prior to HI until sacrifice at 3 days post-HI. SnPP reduced (P < 0.05) infarct volume compared with saline-treated animals, but FePP had no effect on brain injury. SnPP did not significantly inhibit HO activity at 3 days post-HI, but SnPP increased (P < 0.001) total nitric oxide synthase (NOS) activity compared with HI + saline. Both inducible NOS and cyclooxygenase activities were attenuated (P < 0.05) by SnPP, whereas mitochondrial complex I and V activities were augmented (P < 0.05) by SnPP. SnPP had no effect on NMDA receptor currents. Overall, like other HO inhibitors, SnPP produced many nonselective effects, such as attenuation of inflammatory enzymes and increased mitochondrial respiratory function, which were associated with a protective response 3 days post-HI.

Domoic acid impairment of cardiac energetics.

Excitatory mediated neuronal injury has been shown to involve a complex cascade of events. However, the associated cardiac damage reported in humans and marine animals following exposure to excitotoxins has not been well characterized. We hypothesized that the excitotoxin domoic acid can traverse cardiac cell membranes and elicit a deleterious effect on cardiac mitochondrial energetics. Domoic acid (0.05-0.25 microM; 10 min) treatment of isolated rat cardiac mitochondria produced a marked decrease of both mitochondrial flavin adenine dinucleotide (FAD)- and nicotinamide adenine linked respiratory control indices (p < 0.001). Enzymatic assays of the mitochondrial electron transport chain (complexes I-V) and the mitochondrial matrix marker enzyme citrate synthase, showed marked concentration-dependent impairment in activity and integrity following exposure to domoic acid (p < 0.01). Similar mitochondrial effects were seen following exposure to the glutamic acid analog, kainic acid (0.5-2 microM). Domoic acid (0.05-10 microM; 40 min) was shown by competitive enzyme-linked immunosorbent assay to traverse the cellular membrane of H9c2 rat cardiac myoblasts. Exposure of intact H9c2 cells to domoic acid (10 microM; 24 h) impaired complex II-III activity but did not compromise cellular viability as assessed using cell quantification or lactate dehydrogenase leakage assays. Assessment of reactive oxygen species (superoxide and hydrogen peroxide) production in both isolated cardiac mitochondria and H9c2 cardiomyocytes failed to show any significant differences following exposure to domoic acid (0.05-5 microM). This is the first study to demonstrate a direct effect of domoic acid on cardiac mitochondrial energetics. However, the absence of substantial damage to intact cardiomyocytes raises questions regarding direct toxicological effects on cardiac energetics or viability under conditions of natural domoic acid exposure.

Expanding retrograde saphenous vein graft aneurysm treated with endovascular coiling.

Saphenous vein graft aneurysm is a potentially fatal complication of coronary artery bypass grafting and usually requires surgery. This report describes endovascular coiling of a saphenous vein graft aneurysm that developed after redo coronary artery bypass grafting. The aneurysm occurred in a proximally occluded saphenous vein graft after revascularization of the same target vessel. The procedure required a retrograde approach through a patent left internal mammary and left anterior descending artery to reach and successfully thrombose the aneurysm.