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，由于血液中凝血因子VIII（FVIII）水平非常低。对严重受影响患者健康的主要影响是自发的（在没有创伤或损伤的情况下）反复出血到膝关节，髋关节，踝关节和肘关节，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。目前的治疗是静脉注射FVIII凝血因子蛋白浓缩物，以应对出血。定期注射FVIII凝血因子蛋白浓缩物每周三次可以预防自发性出血和关节损伤。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引起疾病，可以通过工程改造将人类FVIII基因（AAV 8-HLP-codop-hFVIII-V3）输送到肝脏，而肝脏通常是制造FVIII的地方。我们最近已经使用这种类型的AAV载体用于血友病B的基因治疗，血友病B是一种具有相同临床表现的相关病症，除了它是由于称为因子IX的不同蛋白质的低水平而产生。在广泛的临床前研究之后，将向患有重度血友病A的成人患者的外周静脉中施用单剂量的含有新的更有效的人凝血因子VIII变体（AAV 8-HLP-codop-hFVIII-V3）的AAV载体。我们建议检测三个剂量水平：2 e11、6 e11和2 e12载体基因组/kg体重，这与血友病B临床试验中检测的剂量范围相同。主要目标是确定安全性，为此，我们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检查。只有在前一名受试者的急性毒性观察至少28天后，才能对每名受试者进行入组。如果在一名受试者中观察到严重不良毒性，则将暂停试验。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。这种表达水平可以显著降低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，动物模型对人类预后的预测效果较差。成功的血友病A基因治疗将改变这种疾病的治疗范式，也将支持其他影响肝脏的疾病（包括溶酶体储积症和肝细胞癌）的基因治疗的开发。

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.