AAV-Mediated Gene Therapy for Hemophilia

描述（由申请方提供）：本提案中待检验的主要假设是，腺相关病毒（AAV）载体的肝脏靶向递送可安全介导治疗水平的凝血因子VIII（FVIII）的长期表达，用于治疗血友病A。我们已经使用这种方法在小鼠和非人灵长类动物中安全地产生稳定的治疗水平的凝血因子IX（FIX）。此外，我们最近启动了一项针对血友病B的AAV介导的肝脏靶向基因转移的I/II期临床试验，在该试验中，我们在第一例受试者中使用单次载体剂量建立了稳定的治疗性FIX表达。用于支持本试验的大部分临床前数据是在我们目前的R 01资助下产生的。在这次更新申请中，我们将扩大我们的努力，包括血友病A，最常见的遗传性出血性疾病。然而，血友病A的基因转移存在一些独特的挑战。其中包括：1）编码FVIII的基因的尺寸大，2）FVIII合成和分泌的效率差和3）FVIII抑制剂的发生率高。此外，持续需要提高AAV生产和AAV介导的转基因表达的效率。基于我们知识上的这些差距，我们在更新提案中提出了三个具体目标。目的1：评估编码新型强效FVIII变体的AAV血清型8载体的安全性和有效性。目的2：在AAV介导的肝靶向FVIII基因转移后消除针对FVIII的抗体并建立永久耐受性。目标3：通过防止转导肝细胞内载体基因组的转录沉默来提高AAV介导的FVIII表达的效率。我们将在我们的非人灵长类动物模型中使用在我们的GMP设施中生产的载体进行这些计划的研究，从而能够以高度相关的方式进行仔细的评价。我们预计将根据本次更新申请中提出的实验产生的临床前结果，启动至少一项临床凝血因子VIII基因转移试验。此外，这些研究的结果不仅对血友病A基因治疗，而且对其他可能适合AAV介导的肝脏靶向基因转移的疾病都具有很大的实用性。

DESCRIPTION (provided by applicant): The overriding hypothesis to be tested in this proposal is that liver-targeted delivery of adeno-associated virus (AAV) vectors can safely mediate long-term expression of therapeutic levels of coagulation factor VIII (FVIII) for the treatment of hemophilia A. We have already used this approach to safely generate stable, therapeutic levels of coagulation factor IX (FIX) in mice and non-human primates. In addition, we have recently initiated a phase I/II clinical trial of AAV-mediated, liver-targeted gene transfer for hemophilia B in which we have established stable, therapeutic FIX expression with a single vector dose in our first subject. Much of the pre- clinical data used to support this trial were generated under our current R01 grant. In this renewal application, we will expand our efforts to include hemophilia A, the most common inherited bleeding disorder. However, there are several unique challenges to gene transfer for hemophilia A. These include: 1) the large size of the gene encoding FVIII, 2) the poor efficiency of FVIII synthesis and secretion and 3) the high incidence of FVIII inhibitors. In addition, there is a continued need to improve the efficiency of both AAV production and AAV- mediated transgene expression. Based in these gaps in our knowledge we are proposing three Specific Aims in our renewal proposal. Aim 1: To assess the safety and efficacy of an AAV serotype 8 vector encoding a novel, potent FVIII-variant. Aim 2: To eradicate antibodies against FVIII and establish permanent tolerance following AAV-mediated, liver- targeted FVIII gene transfer. Aim 3: To improve the efficiency of AAV-mediated FVIII expression by preventing transcriptional silencing of vector genomes within transduced hepatocytes. We will perform these planned studies in our non-human primate model with vector produced in our GMP facility, thereby enabling careful evaluation in a highly relevant manner. We anticipate opening at least one clinical FVIII gene transfer trial based on the preclinical results generated from the experiments proposed in this renewal application. In addition, results from these studies will be of great utility not only for hemophilia A gene therapy but also other disorders that are potentially amenable to AAV-mediated, liver-targeted gene transfer.