AAV-Mediated Gene Therapy for Hemophilia

描述(由申请人提供)：本提案中要检验的压倒一切的假设是，肝靶向递送腺相关病毒(AAV)载体可以安全地介导凝血因子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AAV介导的针对血友病B的肝脏靶向基因转移的I/II期临床试验，在该试验中，我们在第一个受试者中建立了稳定的、具有治疗性的FIX表达。用于支持这项试验的大部分临床前数据是在我们目前的R01拨款下产生的。在这次更新申请中，我们将扩大我们的努力，将血友病A，最常见的遗传性出血性疾病包括在内。然而，血友病A的基因转移有几个独特的挑战，包括：1)编码FVIII的基因大，2)FVIII的合成和分泌效率低，3)FVIII抑制剂的发生率高。此外，仍然需要提高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：评价AAV 8型载体编码一种新的、有效的FVIII变异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，清除FVIII抗体并建立永久耐受。目的：通过防止载体基因组在转导的肝细胞内转录沉默来提高AAV介导的FVIII的表达效率。我们将在我们的非人类灵长类动物模型中使用我们的GMP设施产生的载体进行这些计划中的研究，从而能够以高度相关的方式进行仔细的评估。我们预计将根据这一更新申请中建议的实验产生的临床前结果，至少启动一项FVIII基因转移临床试验。此外，这些研究的结果不仅对血友病A的基因治疗有很大的帮助，而且对其他疾病也有很大的帮助，这些疾病可能会受到AAV介导的肝脏靶向基因转移的影响。

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.