MICA: An open label dose-escalation study of a novel adeno-associated viral vector for gene transfer in subjects with haemophilia A

血友病A是一种男性出血性疾病，原因是血液中凝血因子VIII(FVIII)水平非常低。对严重患者健康的主要影响是自发的(在没有创伤或受伤的情况下)膝关节、髋关节、脚踝和肘部等关节反复出血，导致关节损伤和慢性残疾。这种疾病很少会因出血进入大脑或其他重要器官而导致死亡。目前的治疗方法是静脉注射FVIII凝血因子蛋白浓缩物，以应对出血。这项研究计划使用一种名为腺相关病毒(AAV)的病毒，这种病毒在自然界中不会导致疾病，可以被改造成将人类FVIII基因(AAV8-HLP-codop-hFVIII-V3)转移到通常制造FVIII的肝脏。我们最近将这种类型的AAV载体用于血友病B的基因治疗，这是一种具有相同临床表现的相关疾病，只是它是由于一种不同的蛋白质水平较低而引起的，称为因子IX。在这项研究中，在所有10名参与者中都观察到FIX在正常水平的1-6%的稳定表达，没有长期的毒性，导致显著的患者受益。在广泛的临床前研究之后，含有新的更有效的人凝血因子VIII变异体(AAV8-HLP-codop-hFVIII-V3)的AAV载体将被单剂量注射到患有严重血友病A的成年患者的外周静脉中。我们建议测试三个剂量水平：每公斤体重2E11、6E11和2E12载体基因组，这与在血友病B临床试验中测试的剂量范围相同。主要目标将是确定安全性，为此，我们已经制定了一项全面的监测计划，其中包括一系列临床和实验室测试。只有在先前的受试者因急性毒性观察了至少28天后，才能进行每一受试者的登记。如果在一个科目中观察到严重的不良反应，将暂停报名。另一个目的是确定导致FVIII在外周血中表达超过5%的载体剂量。这种水平的表达可以显著减少严重出血发作的频率。人类研究之所以至关重要，是因为我们的血友病B基因治疗试验以及该领域的其他基因治疗研究表明，动物模型不能很好地预测人类的结果。血友病A基因治疗的成功将改变这种疾病的治疗模式，并将支持其他影响肝脏的疾病的基因治疗的发展，包括溶酶体储存障碍和肝细胞癌。

Haemophilia A is a bleeding disease in males due to very low levels of coagulation factor VIII (FVIII) in the blood. The major effect on health in severely affected patients is spontaneous (in the absence of trauma or injury) repeated bleeds into joints like the knee, hip, ankles and elbows, cause joint damage and chronic disability. Rarely, the disease causes death due to bleeding into the brain or other important organs. The current treatment is intravenous injection of FVIII clotting factor protein concentrates, in response to bleeding. Regular injection of FVIII clotting factor protein concentrates three times a week prevents spontaneous bleeds and joint damage.This study plans to use a virus called adeno-associated virus (AAV), which in nature causes no disease, and can be engineered to deliver the human FVIII gene (AAV8-HLP-codop-hFVIII-V3) to the liver, where FVIII is normally made. We have recently used this type of AAV vector for gene therapy of haemophilia B, a related condition with identical clinical manifestation, except that it arises because of low levels of a different protein called factor IX. In this study stable expression of FIX at levels 1-6% of normal were observed in all 10 participants without long lasting toxicity, resulting in significant patient benefit.Following extensive preclinical studies, a single dose of AAV vector containing a novel more potent human clotting factor VIII variant (AAV8-HLP-codop-hFVIII-V3) will be administered into a peripheral vein of adult patients with severe Haemophilia A. We propose to test three dose levels: 2e11, 6e11 and 2e12 vector genomes per kg body weight, which is the same dose range tested in the Haemophilia B clinical trial. The main objective will be to establish the safety and to do so we have established a comprehensive monitoring plan which includes an array of clinical and laboratory tests. Enrolment of each subject will proceed only after the previous subject has been observed for at least 28 days for acute toxicity. Enrolment will be suspended if serious adverse toxicity is observed in one subject. The other objective is to determine the dose of vector that results in expression of FVIII at more than 5% in peripheral blood. This level of expression can significantly reduce the frequency of severe bleeding episodes. The reason why human studies are critical is because our haemophilia B gene therapy trial, as well as other gene therapy studies in the field, have shown that animal models are poor predictors of outcome in humans. Successful Haemophilia A gene therapy will transform the treatment paradigm for this disease and will also support the development of gene therapy for other diseases affecting the liver including lysosomal storage disorders and hepatocellular carcinoma.