Immunomodulation Approaches to Improve Safety And Efficacy of Gene Therapy Treatment in Friedreich’s Ataxia

项目总结/摘要 弗里德赖希共济失调（FA）是遗传性共济失调的最常见形式，每50，000人中就有1人受到影响 在美国. FA是由GAA三核苷酸重复序列遗传引起的常染色体隐性遗传疾病 fraataxin（FXN）基因的扩增，这导致线粒体中FXN水平降低。临床 表现出现在8至16岁之间，作为多系统疾病，主要影响心脏和 神经系统FA是稳步进展的，其特征是生活质量（QOL）下降， 过早死亡，通常由室性心律失常引起。目前没有有效的治疗方法。 使用携带人FXN基因的重组腺相关病毒载体（rAAV）进行基因置换 是一个有前途的治疗策略，为FA显示我们的小组和其他人。我们的团队已经进行了 毒理学和生物分布研究，以支持用于治疗以下疾病的首次人体基因治疗研究： FA. IND将于2020年第二季度提交，我们预计在批准后立即招募首例患者。 然而，基因治疗成功的一个关键的未解决的挑战是宿主免疫应答， 载体衣壳携带转基因的rAAV载体的施用增强细胞和适应性免疫 针对载体衣壳的反应。夸大的免疫反应可能导致安全问题和影响 表达的寿命，以及导致治疗效果的丧失。此外，临床前数据来自 我们的实验室和其他实验室表明，先前自然暴露于AAV（预先存在的免疫力），可导致严重的 输注反应和随后的AAV暴露降低的治疗功效。当前AAV介导的 基因治疗试验必须考虑以低于毒性水平的剂量单次暴露于治疗载体 并排除具有预先存在的AAV免疫的受试者。我们的假设是更有效的剂量 通过随时间增加AAV剂量与多个较低AAV剂量安全地实现。我们广泛 临床前和临床数据表明，利妥昔单抗和西罗莫司的B细胞耗竭与 AAV递送阻止抗体的形成，并证实了我们的假设。然而，长期使用 利妥昔单抗与罕见但破坏性的不良事件有关。在本U 01申请中，我们建议 通过确定最佳的治疗方案， 免疫调节方案，以防止针对AAV衣壳的免疫应答，这将允许安全的免疫应答。 在受试者中重复施用AAV（目的1）和治疗性AAV施用， 豁免（目标2）。我们预计，这些研究将对基因工程的应用产生重大影响。 治疗方法不仅适用于FA，而且适用于广泛的神经肌肉遗传性疾病。

Project Summary / Abstract Friedreich’s ataxia (FA) is the most common form of hereditary ataxia, affecting ~1 in every 50,000 people in the US. FA is an autosomal recessive condition caused by the inheritance of a GAA trinucleotide repeat expansions in the frataxin (FXN) gene, which results in reduced levels of FXN in mitochondria. Clinical manifestations appear between the ages of 8 and 16 as a multisystem disorder, primarily affecting cardiac and nervous system. FA is steadily progressive and is characterized by diminished quality of life (QOL) and premature death, usually caused by ventricular arrhythmia. There is currently no effective treatment. Gene replacement using recombinant adeno-associated viral vectors (rAAV) carrying the human FXN gene is a promising therapeutic strategy for FA as shown by our group and others. Our group has conducted toxicology and biodistribution studies in support of the first-in-human gene therapy study for the treatment of FA. The IND will be submitted in 2020 Q2 and we expect to enroll the first patient immediately after approval. However, a critical unresolved challenge for the success of gene therapy is the host immune response to the vector capsid. Administration of rAAV vectors carrying a transgene elicits cellular and adaptive immune responses against the vector capsid. Exaggerated immune responses can lead to safety concerns and impact longevity of expression, as well as contribute to loss of the therapeutic effect. In addition, preclinical data from our lab and others suggest that prior natural exposure to AAV (pre-existing immunity), can lead to severe infusion reactions and diminished therapeutic efficacy with subsequent AAV exposure. Current AAV-mediated gene therapy trials must consider a single exposure to the therapeutic vector at a dose below the toxic level and exclude subjects with pre-existing AAV immunity. Our hypothesis is that a more effective dose could be achieved safely by incremental dosing of AAV with multiple lower AAV doses over time. Our extensive preclinical and clinical data demonstrate that B-cell depletion with rituximab and sirolimus in association with AAV delivery prevents formation of antibodies and confirm our hypothesis. However, prolonged use of rituximab has been associated with rare but devastating adverse events. In this U01 application, we propose to improve the overall efficacy and safety of the planned FA gene therapy program by identifying an optimal immunomodulation regimen to prevent immune responses against the AAV capsid, which will allow for safe repeated administration of AAV (Aim 1) and therapeutic AAV administration in subjects’ with pre-existing immunity (Aim 2). We anticipate that the proposed studies will have a major impact on the application of gene therapy approaches not only for FA, but for a wide array of neuromuscular genetic disorders.