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

项目摘要/摘要 弗里德里希共济失调(FA)是遗传性共济失调最常见的形式，每50,000人中就有1人受到影响 在美国。FA是一种常染色体隐性遗传性疾病，由GAA三核苷酸重复序列遗传引起 Frataxin(FXN)基因的扩张，导致线粒体中FXN水平的降低。临床 症状出现在8岁到16岁之间，是一种多系统疾病，主要影响心脏和 神经系统。FA是稳步进步的，其特点是生活质量(QOL)和 早逝，通常由室性心律失常引起。目前还没有有效的治疗方法。 携带人FXN基因的重组腺相关病毒载体(RAAV)的基因置换 是一种很有前途的治疗FA的策略，正如我们小组和其他人所表明的那样。我们小组已经进行了 毒理学和生物分布研究支持人类首个治疗糖尿病的基因治疗研究 FA.IND将于2020年第二季度提交，我们预计在批准后立即招募第一名患者。 然而，基因治疗成功的一个关键的悬而未决的挑战是宿主对 病媒衣壳。携带转基因的rAAV载体诱导细胞免疫和获得性免疫 对媒介衣壳的反应。过度的免疫反应可能会导致安全问题和影响 长寿的表达，以及造成的治疗效果的丧失。此外，临床前数据来自 我们的实验室和其他人认为，先前自然暴露于AAV(先前存在的免疫)，可能会导致严重的 输液反应和随后暴露于AAV的治疗效果降低。当前由AAV介导的 基因治疗试验必须考虑单次接触低于毒性水平的治疗载体。 并排除已有AAV免疫力的受试者。我们的假设是更有效的剂量可能是 随着时间的推移，通过递增AAV剂量和多次较低的AAV剂量，可以安全地实现。我们广泛的 临床前和临床数据表明，利妥昔单抗和西罗莫司对B细胞的耗竭与 AAV的传递可以防止抗体的形成，并证实了我们的假设。然而，长期使用 利妥昔单抗与罕见但毁灭性的不良事件有关。在这份U01申请中，我们建议 通过确定最佳的FA基因治疗方案来提高计划中的FA基因治疗计划的整体有效性和安全性 免疫调节方案，以防止针对AAV衣壳的免疫反应，这将允许安全 既往患者重复使用AAV(目标1)和治疗性AAV应用 豁免(目标2)。我们预计，拟议的研究将对基因的应用产生重大影响。 治疗方法不仅适用于FA，还适用于多种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.