rAAV-Mediated Gene Therapy for Hemophillia B

描述（由申请方提供）：血友病B是一种遗传性出血性疾病，是由于凝血因子IX（FIX）合成缺陷所致。基因治疗介导的FIX替代方法具有许多优点，特别是持续表达的潜力。在本项目中待检验的最重要假设是，编码人因子IX（hFIX）cDNA的重组腺相关病毒（rAAV）载体的肝脏靶向递送可以安全地介导hFIX治疗水平的长期表达。这种方法已成功用于在小鼠中产生正常水平的hFIX，但在相关的非人灵长类动物模型或人类中尚未取得一致的成功。需要建立最佳递送方法以确保灵长类动物肝脏的有效rAAV转导，具有持续的高水平转基因表达，并且具有最小的程序或载体相关毒性。此外，对AAV的天然获得性和医源性免疫对rAAV载体转导效率的影响以及操纵这些潜在免疫障碍以成功基因转移的能力尚不清楚。最后，在开始临床试验之前，证明这种基因治疗介导的方法的安全性至关重要。这项拟议的研究旨在解决与人类相关的背景下的这些关键问题。将测试以下假设：（1）替代血清型rAAV-8的rAAV颗粒可产生大于通过rAAV-5颗粒获得的hFIX的全身水平，并且无论使用肠系膜或外周静脉途径的载体施用，均可实现等效的转导效率。(2)当使用替代rAAV血清型时或当在初始载体施用时利用瞬时免疫抑制时，载体再施用可实现等效的转导效率。(3)靶向肝脏的rAAV介导的转移是安全的，不会导致生殖系传播，并且不会有长期毒性，包括器官损伤和恶性肿瘤的发展。这些研究产生的数据将为血友病B的基因治疗试验以及其他可能采用AAV介导的肝脏靶向基因治疗的潜在试验提供见解和临床前数据。

DESCRIPTION (provided by applicant): Hemophilia B is an inherited bleeding disorder that is due to a defect in blood coagulation factor IX (FIX) synthesis. A gene therapy mediated approach to the replacement of FIX has a number of advantages, particularly the potential for sustained expression. The overriding hypothesis to be tested in this project is that liver-targeted delivery of recombinant adeno-associated virus (rAAV) vectors encoding the cDNA for human factor IX (hFIX) can safely mediate long-term expression of therapeutic levels of hFIX. This approach has been used successfully to generate normal levels of hFIX in mice but has not yet consistently been successful in a relevant nonhuman primate model or in humans. Optimal delivery methods need to be established to ensure efficient rAAV transduction of the primate liver with persistent, high-level transgene expression, and with minimal procedure or vector-related toxicity. In addition, the impact of naturally acquired and iatrogenic immunity to AAV on transduction efficiency with rAAV vectors and the ability to manipulate these potential immunologic obstacles to successful gene transfer is unknown. Finally, demonstrating the safety of this gene therapy mediated approach is of critical importance prior to initiating a clinical trial. This proposed study is designed to address these critical issues in a context that is relevant to humans. The following hypotheses will be tested: (1) rAAV particles of an alternative serotype, rAAV-8, can generate systemic levels of hFIX that are greater than those obtained by rAAV-5 particles, and equivalent transduction efficiency can be achieved whether using the mesenteric or peripheral venous route of vector administration. (2) Equivalent transduction efficiency can be achieved with vector re-administration either when an alternate rAAV serotype is used or when transient immunosuppression is utilized at the time of initial vector administration. (3) rAAV mediated transfer targeting the liver is safe, will not lead to germ line transmission, and will be free of long term toxicity, including organ damage, and the development of malignancy. Data generated from these studies will provide insight and preclinical data for a gene therapy trial not only for hemophilia B, but also for other potential trials in which AAV-mediated liver-targeted gene therapy might be employed.