Biological pacemaker from proof-of-concept to clinic

项目摘要 该提案的总体目标是为生物学的首次人体研究奠定临床前基础。 起搏器（BioP）作为电子设备的替代品。基于基因的生物P首先被描述为超过一个 十年前;各种构建体的体细胞基因转移（内向整流子的显性负突变体） 通道[Kir2.1AAA]、野生型HCN通道和转录因子[Tbx 18]）都已被证明 创造生物活性。然而，直到最近，体内临床前应用大多限于高度- 入侵模式我们开发了一种临床上现实的微创输送技术，并将其用于 在完全心脏传导阻滞的猪模型中创建BioP。在这里，我们建议使用这种方法来比较两个 具有根本不同的作用机制的“决赛”治疗候选物。第一个是野生型的 离子通道（HCN 2），通过功能性重新激活， 工程.我们的目标不是创造一个忠实的起搏细胞复制品，而是操纵一个单一的 细胞膜通道的组成部分，以诱导在一个可兴奋的，但 正常静止细胞第二种候选治疗药物Tbx 18的活性成分重新编程 心室心肌细胞转化为窦房结（SAN）样起搏细胞（诱导SAN [iSAN]细胞）。没有人 兴奋性的决定因素是选择性过度表达：整个基因表达程序被改变， 导致基本细胞生理学和形态学的变化。该提案利用了上述 在心动过缓的大型动物模型中， 需要翻译到诊所。我们将描述和比较HCN 2的起搏有效性和安全性 和Tbx 18衍生的BioP，检验iSAN细胞将提供上级变时性支持的假设， 与HCN 2相比。我们将继续进行长期疗效，毒理学和生物分布研究， 更有前途的治疗候选药物，然后准备并获得研究新药的批准 (IND)申请首次人体生物磷试验虽然最终的目标可能是使过时的， 电子起搏器，重要的是要现实地考虑潜在的首次在人体中的应用。 因此，我们最初选择开发一种桥接到设备的产品， 起搏器依赖性感染患者的无硬件变时性支持。为了制造生物P 暂时，我们将基因递送到腺病毒载体中，依靠免疫清除来限制生物活性。 尽管如此，我们将测试BioP的导管消融，作为持续性情况下的备用抢救策略。 不希望的BioP活性。该研究提案旨在为临床试验奠定基础 优化BioP最初在贫困人口中。

Project Summary The overall objective of the proposal is to lay the preclinical groundwork for first-in-human studies of biological pacemakers (BioP) as alternatives to electronic devices. Gene-based BioP were first described more than a decade ago; somatic gene transfer of various constructs (a dominant-negative mutant of the inward rectifier channel [Kir2.1AAA], wild-type HCN channels, and a transcription factor [Tbx18]) have all been shown to create BioP activity. However, until recently, in vivo preclinical applications have been mostly limited to highly- invasive models. We have developed a clinically-realistic minimally-invasive delivery technique and used it to create BioP in a porcine model of complete heart block. Here, we propose to use this approach to compare two “finalist” therapeutic candidates with fundamentally different mechanisms of action. The first one is a wild-type ion channel (HCN2) that artificially induces automaticity in ventricular cardiomyocytes by functional re- engineering. The goal is not to create a faithful replica of a pacemaker cell, but rather to manipulate a single component of the membrane channel repertoire so as to induce spontaneous firing in an excitable but normally-quiescent cell. The active principle of the second therapeutic candidate, Tbx18, reprograms ventricular cardiomyocytes into sinoatrial node (SAN)-like pacemaker cells (induced SAN [iSAN] cells). No one determinant of excitability is selectively over-expressed: the entire gene expression program is altered, with resultant changes in fundamental cell physiology and morphology. The proposal utilizes the abovementioned percutaneous delivery method to refine and validate, in a large-animal model of bradycardia, the approaches required for translation to the clinic. We will characterize and compare the pacing efficacy and safety of HCN2 and Tbx18-derived BioP, testing the hypothesis that iSAN cells will provide superior chronotropic support as compared to HCN2. We will go on to perform long-term efficacy, toxicology and biodistribution studies with the more promising therapeutic candidate, and then prepare, and obtain approval of, an Investigational New Drug (IND) application for a first-in-human BioP trial. While the ultimate goal may be to render obsolete the electronic pacemaker, it is important to be realistic in thinking about potential first-in-human applications. Therefore, we have chosen to develop, initially, a bridge-to-device product that will temporarily provide hardware-free chronotropic support in infected patients who are pacemaker-dependent. To make BioP temporary, we deliver the genes in adenoviral vectors, relying on immunological clearance to limit bioactivity. Nevertheless, we will test catheter ablation of the BioP as a backup rescue strategy in case of persistent undesired BioP activity. This research proposal is designed to lay the groundwork for clinical testing of an optimized BioP initially in a needy population.