AN OPEN LABEL DOSE-ESCALATION STUDY OF A SELF COMPLEMENTARY AAV VECTOR FOR GENE THERAPY OF HAEMOPHILIA B

在拟议的研究中，我们希望测试一种名为基因疗法的新方法来治疗血友病B患者。这种遗传性疾病，在没有创伤的情况下发生危及生命的出血，原因是一种名为凝血因子IX(FIX)的凝血蛋白缺失或缺陷，这种凝血蛋白是由于FIX基因的突变而产生的。因此，我们的基因治疗方法的目标是通过将FIX基因的正常副本转移到患者S的肝脏来治疗这种疾病，以便患者S自己的细胞能够持续产生正常的FIX蛋白。为此，我们开发了一种基于腺相关病毒的新型载体(scAAV2/8-LP1-FIXco)，它可以高效地将正常FIX基因转移到其天然合成部位肝脏。重要的是，在病毒来源的基因转移载体中，AAV具有最好的安全性。在小鼠和非人类灵长类动物模型中，我们一致地实现了人类FIX的长期表达，其水平足以防止单次注射scAAV2/8-LP1-FIXco后血友病B患者自发性危及生命的出血。载体只需注入外周静脉，这是一种非常方便的给药途径，不需要外科手术来有效地将FIX基因转移到肝脏。基于这些令人鼓舞的临床前结果，我们希望在少数患有严重血友病B的成年人中评估这一载体系统。符合条件的受试者从世界各地的血友病患者池中抽取，在获得他们的同意之前，将收到关于这项研究的风险和优点的明确和详细的说明。我们的主要目的是建立三个不同剂量水平的scAAV2/8-LP1-hFIXco外周静脉给药的安全性。这项研究将由一个国际医学专家小组监督，将涉及一项全面的调查计划，以监测安全性，特别强调对病毒的免疫反应和正常的FIX蛋白。另一个目标是确定使人FIX的稳定表达达到或超过正常水平的5%所需的载体剂量，这将足以防止自发性出血。我们方法的成功可能会对多种威胁生命的遗传性疾病产生重大影响，包括α-1抗胰蛋白酶缺乏症、溶酶体储存和尿素循环障碍。

In the proposed study we wish to test a new approach called gene therapy for the treatment of patients with haemophilia B. This inherited disorder in which life threatening bleeding occurs without trauma results from an absence or defect of a blood clotting protein called Factor IX (FIX) that arises due to mutations in the FIX gene. The goal of our gene therapy approach, therefore, is to treat the disease by transferring to the patient s liver, a normal copy of the FIX gene so that normal FIX protein can be continuously produced by the patient s own cells. To this end we have developed a novel vector based on adeno-associated virus (scAAV2/8-LP1-FIXco) which is highly efficient at transferring the normal FIX gene to the liver, its natural site of synthesis. Importantly, AAV has the best safety profile among gene transfer vectors of viral origin. In murine and nonhuman primate models we have consistently achieved long-term expression of human FIX at levels that would be sufficient to prevent spontaneous life threatening bleeding in haemophilia B patients following a single injection of scAAV2/8-LP1-FIXco. The vector is simply infused into a peripheral vein, a highly convenient route of administration that dispenses with the need for surgical intervention for efficient transfer of the FIX gene to the liver. Based on these encouraging preclinical results we wish to evaluate this vector system in a small number of adults with severe haemophilia B. Eligible subjects, drawn from the worldwide pool of haemophiliacs, will receive explicit and detailed instructions about the risks and merits of this study prior to obtaining their consent for enrolment. Our primary aim is to establish the safety of peripheral vein administration of scAAV2/8-LP1-hFIXco over three different dosage levels. This study, which will be overseen by an international panel of medical experts, will involve a comprehensive plan of investigations to monitor safety, with particular emphasis on immune response to the virus and normal FIX protein. An additional objective is to determine the dose of vector that is required to achieve stable expression of human FIX at or above 5% of normal levels which would be sufficient to prevent spontaneous bleeding. Success with our approach could significantly impact on a wide variety of life threatening genetic disorders including alpha-1 antitrypsin deficiency, lysosomal storage and urea cycle disorders.