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，其特征是缺乏因子IX（F.IX）。这种疾病是一个很好的候选人治疗基因为基础的治疗，因为F.IX低至1-5%的正常与临床效益。4年前开始了对血友病B受试者进行IAAV-2肝定向F.IX基因转移的I/II期临床研究。总体而言，通过肝动脉输送载体的耐受性良好，无严重不良事件。高剂量组1例受试者存在循环F。在接受载体后2周，IX水平为正常水平的12%，但表达是短暂的。表达丧失伴有无症状的转胺酶炎，并自发消退。免疫介导的转导肝细胞的破坏很可能是transaminitis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表达而不损伤肝细胞。这项工作的总体目标是确定麦考酚酸酯（MMF）和他克莫司（TC）对AAV-2-F. IX的短暂免疫抑制方案的疗效和安全性。由MMF/TC组成的方案已在器官移植受者和自身免疫性疾病受试者中进行了广泛的长期免疫抑制治疗试验。在目标1中，我们将使用非人灵长类动物（NHP），这是最接近人类的模型，以确定MMF/TC方案对AAV-2肝脏定向基因转移的有效性和安全性。由于这些药物可能干扰双链DMA合成，我们将通过注射NHP中的AAV-2确定MMF/TC是否会干扰基因转移/转基因表达、载体衣壳在肝组织中的持续时间以及载体生物分布。结果将为关于AAV-2介导的、肝脏直接的F.IX基因递送至成人血友病B受试者的新剂量递增I/II期临床研究提供基础（目的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、载体生物分布以及F. IX抗体形成来确定该方法的安全性。具体地，我们将表征针对AAV-2衣壳的中和抗体在防止AAV-2转导中的作用，将定义针对AAV衣壳肽的免疫应答，并确定所需免疫调节的持续时间。我们还计划通过测量F的生物活性来评估每个受试者的潜在疗效。九.

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.