Adeno-associated virus (AAV) vectors are a leading platform for gene-based therapies for both monogenic and complex acquired disorders. The success of AAV gene transfer highlights the need to answer ...outstanding clinical questions of safety, durability, and the nature of the human immune response to AAV vectors. Here, we present longitudinal follow-up data of subjects who participated in the first trial of a systemically delivered AAV vector. Adult males (n = 7) with severe hemophilia B received an AAV2 vector at doses ranging from 8 × 1010 to 2 × 1012 vg/kg to target hepatocyte-specific expression of coagulation factor IX; a subset (n = 4) was followed for 12–15 years post-vector administration. No major safety concerns were observed. There was no evidence of sustained hepatic toxicity or development of hepatocellular carcinoma as assessed by liver transaminase values, serum α-fetoprotein, and liver ultrasound. Subjects demonstrated persistent, increased AAV neutralizing antibodies (NAbs) to the infused AAV serotype 2 (AAV2) as well as all other AAV serotypes tested (AAV5 and AAV8) for the duration of follow-up. These data represent the longest available longitudinal follow-up data of subjects who received intravascular AAV and support the preliminary safety of intravascular AAV administration at the doses tested in adults. Data demonstrate, for the first time, the persistence of high-titer, multi-serotype cross-reactive AAV NAbs for up to 15 years post- AAV vector administration. Our observations are broadly applicable to the development of AAV-mediated gene therapy.
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Presented here are the longest available longitudinal follow-ups of human subjects following intravascular adeno-associated virus (AAV) vector administration. These data support the preliminary long-term safety of systemic AAV delivery and demonstrate the persistence of high-titer, multi-serotype, cross-reactive AAV NAbs for up to 15 years after vector infusion.
Endogenous and exogenous hormones have significant effects on coagulation and may tip the hemostatic balance toward thrombosis. The endogenous hormonal changes in pregnancy and polycystic ovary ...syndrome, and exogenous hormonal contraception, menopause replacement, and transgender cross-hormone replacement may increase thromboembolism risk. Using the lowest effective dose is critical for prevention, but once thrombosis occurs, anticoagulation may be required, in some, long term. We review the relative risk of thrombosis in these conditions, risk factors, and anticoagulation treatment and prevention. Implementation of lowest effective hormonal therapies, thrombosis reduction strategies, and current anticoagulation management are critical for optimal patient outcomes.
Fitusiran is an RNA interference therapeutic that targets antithrombin (AT) in the liver and interferes with AT translation by binding and degrading messenger RNA-AT, thereby silencing AT gene ...expression and preventing AT synthesis. In both preclinical and clinical studies, AT knockdown results in dose-dependent AT lowering when fitusiran is given weekly or monthly subcutaneously. In clinical trials, fitusiran dose escalation has resulted in improved thrombin generation and clinical hemostasis as measured by reduction in annualized bleed rate. Unlike currently licensed drugs, this improvement was not only in patients with hemophilia A but in also those with hemophilia B, with or without inhibitors. In dental and surgical procedures, fitusiran also provided perioperative hemostasis in association with AT lowering. Fitusiran is well tolerated, with minor local injection site reactions, but in one subject with severe hemophilia A, the concomitant use of daily high-dose factor VIII, inconsistent with trial guidance to avoid high, repeat doses of clotting factor, was associated with fatal thrombosis, suggesting the need for caution when using hemostatic agents in conjunction with fitusiran. Preclinical in vitro and in silico studies indicate improvement in thrombin generation in rare bleeding disorder plasmas, including in plasmas from patients with severe factors V, VII, and X deficiency, suggesting potential therapeutic benefit.
Current hemophilia treatment involves frequent intravenous infusions of clotting factors, which is associated with variable hemostatic protection, a high treatment burden, and a risk of the ...development of inhibitory alloantibodies. Fitusiran, an investigational RNA interference (RNAi) therapy that targets antithrombin (encoded by SERPINC1), is in development to address these and other limitations.
In this phase 1 dose-escalation study, we enrolled 4 healthy volunteers and 25 participants with moderate or severe hemophilia A or B who did not have inhibitory alloantibodies. Healthy volunteers received a single subcutaneous injection of fitusiran (at a dose of 0.03 mg per kilogram of body weight) or placebo. The participants with hemophilia received three injections of fitusiran administered either once weekly (at a dose of 0.015, 0.045, or 0.075 mg per kilogram) or once monthly (at a dose of 0.225, 0.45, 0.9, or 1.8 mg per kilogram or a fixed dose of 80 mg). The study objectives were to assess the pharmacokinetic and pharmacodynamic characteristics and safety of fitusiran.
No thromboembolic events were observed during the study. The most common adverse events were mild injection-site reactions. Plasma levels of fitusiran increased in a dose-dependent manner and showed no accumulation with repeated administration. The monthly regimen induced a dose-dependent mean maximum antithrombin reduction of 70 to 89% from baseline. A reduction in the antithrombin level of more than 75% from baseline resulted in median peak thrombin values at the lower end of the range observed in healthy participants.
Once-monthly subcutaneous administration of fitusiran resulted in dose-dependent lowering of the antithrombin level and increased thrombin generation in participants with hemophilia A or B who did not have inhibitory alloantibodies. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02035605 .).
The goal of gene therapy for patients with hemophilia A is to safely impart long-term stable factor VIII expression that predictably ameliorates bleeding with the use of the lowest possible vector ...dose.
In this phase 1-2 trial, we infused an investigational adeno-associated viral (AAV) vector (SPK-8011) for hepatocyte expression of factor VIII in 18 men with hemophilia A. Four dose cohorts were enrolled; the lowest-dose cohort received a dose of 5 × 10
vector genomes (vg) per kilogram of body weight, and the highest-dose cohort received 2 × 10
vg per kilogram. Some participants received glucocorticoids within 52 weeks after vector administration either to prevent or to treat a presumed AAV capsid immune response. Trial objectives included evaluation of the safety and preliminary efficacy of SPK-8011 and of the expression and durability of factor VIII.
The median safety observation period was 36.6 months (range, 5.5 to 50.3). A total of 33 treatment-related adverse events occurred in 8 participants; 17 events were vector-related, including 1 serious adverse event, and 16 were glucocorticoid-related. Two participants lost all factor VIII expression because of an anti-AAV capsid cellular immune response that was not sensitive to immune suppression. In the remaining 16 participants, factor VIII expression was maintained; 12 of these participants were followed for more than 2 years, and a one-stage factor VIII assay showed no apparent decrease in factor VIII activity over time (mean ±SD factor VIII activity, 12.9±6.9% of the normal value at 26 to 52 weeks when the participants were not receiving glucocorticoids vs. 12.0±7.1% of the normal value at >52 weeks after vector administration; 95% confidence interval CI, -2.4 to 0.6 for the difference between matched pairs). The participants had a 91.5% reduction (95% CI, 88.8 to 94.1) in the annualized bleeding rate (median rate, 8.5 events per year range, 0 to 43.0 before vector administration vs. 0.3 events per year range, 0 to 6.5 after vector administration).
Sustained factor VIII expression in 16 of 18 participants who received SPK-8011 permitted discontinuation of prophylaxis and a reduction in bleeding episodes. No major safety concerns were reported. (Funded by Spark Therapeutics and the National Heart, Lung, and Blood Institute; ClinicalTrials.gov numbers, NCT03003533 and NCT03432520.).
WFH Guidelines for the Management of Hemophilia, 3rd edition Srivastava, Alok; Santagostino, Elena; Dougall, Alison ...
Haemophilia : the official journal of the World Federation of Hemophilia,
August 2020, 2020-08-00, 20200801, 2020-08-01, Letnik:
26, Številka:
S6
Journal Article
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