AAV2-F.IX Hepatic Gene Transfer under Immunomodulation

描述(由申请人提供)： 血友病B是一种遗传性出血性疾病，其特征是因子IX(F.IX)缺乏。这种疾病是一个很好的基于基因治疗的候选疾病，因为低至正常的1-5%的F.IX与临床益处有关。4年前开始了血友病B患者肝内转导甲型流感病毒2型疫苗的L/Ⅱ期临床研究。总体而言，通过肝动脉的媒介传递耐受性良好，没有严重的不良反应。高剂量组中的一名受试者在接受载体2周后循环中的F-IX水平为正常的12%，但表达时间很短。表达的丧失伴随着自发消退的无症状的转氨炎。免疫介导的肝细胞破坏很可能是导致转移性肝炎和表达丧失的原因。为了避免这种情况的发生，我们将测试免疫调节是否允许在不损害肝细胞的情况下表达。这项工作的总体目标是建立一种由霉酚酸酯(MMF)和他克莫司(TC)组成的暂时性免疫抑制方案对AAV-2-FIX的有效性和安全性。由MMF/TC组成的方案已经在器官移植受者和自身免疫性疾病患者中进行了广泛的长期免疫抑制治疗。在目标1中，我们将使用非人类灵长类动物(NHP)这一最接近人类的模型来建立MMF/TC方案在AAV-2肝脏定向基因转移中的有效性和安全性。由于这些药物可能干扰双链DNA的合成，我们将确定MMF/TC是否会通过在NHP中注射AAV-2来干扰基因转移/转基因表达、载体衣壳的持续时间、在肝组织中和载体的生物分布。这一结果将为新的剂量升级阶段L/11临床研究提供基础，该研究由AAV-2介导，肝脏直接向成人血友病B患者传递F.IX基因(AIMS 2-4)。我们的主要目标是通过监测受试者的局部和全身毒性、载体生物分布和对F.IX的抗体形成来确定这种方法的安全性。具体地说，我们将表征针对AAV-2衣壳的中和抗体在防止AAV-2转导方面的作用，将确定对AAV衣壳多肽的免疫应答，并确定所需的免疫调节持续时间。我们还计划通过测量F.IX的生物活性来评估每个受试者的潜在疗效。

DESCRIPTION (provided by applicant): Hemophilia B is a inherited bleeding disorder characterized by a deficiency of factor IX (F.IX). The disease is an excellent candidate for treatment by gene-based therapy because F.IX as low as 1-5% of normal is associated with clinical benefits. A Phase l/ll clinical study on IAAV-2, liver-directed F.IX gene transfer to hemophilia B subjects was initiated 4 years ago. Overall the vector delivery through the hepatic artery was well tolerated with no serious adverse event. One subject in the high dose group had circulating F. IX levels of 12% of normal 2 weeks after receiving vector, but expression was short lived. The loss of expression was accompanied by an asymptomatic transaminitis that resolved spontaneously. There is high likelihood that immune-mediated destruction of the transduced hepatocytes was responsible for transaminitis and loss of expression. To circumvent this occurrence, we will test whether immunomodulation allows expression without hepatocyte damage. The overall goal of this work is to establish the efficacy and safety of a transient immunosuppressive regimen with mycophenolate mofetil (MMF) and tacrolimus (TC) on AAV-2-F.IX. The regimen consisting of MMF/TC has been extensively tested for long-term immune-suppressive therapy in organ transplant recipients and subjects with autoimmune diseases. In aim 1 we will use non-human primates (NHP), the closest model to human to establish the efficacy and safety of MMF/TC regimen on AAV-2-liver-directed gene transfer. Because these drugs may interfere with double strand DMA synthesis we will determine if MMF/TC will interfere with gene transfer/transgene expression, duration of the vector capsid persistence, in the liver tissue and with vector biodistribution by injecting AAV-2 in NHP. The results will provide the basis for a new dose escalation Phase l/ll clinical study on AAV-2-mediated, liver-direct F.IX gene delivery to adult hemophilia B subjects (aims 2-4). Our main goal is to determine the safety of this approach by monitoring subjects for local and systemic toxicity, vector biodistribution, and for antibody formation to F.IX. Specifically, we will characterize the role of neutralizing antibody to AAV-2 capsid on preventing AAV-2 transduction, will define the immune responses to AAV capsid peptides,,and determine the duration of the immunomodulation required. We also plan to evaluate the potential efficacy in each subject by measuring biological activity of F. IX.