Measuring Intralesional Bedaquiline Exposures in Cavitary TB Using Noninvasive In Vivo PET Imaging

目前的抗生素剂量建议和药物敏感性折点是基于血浆 浓度和历史疗效指标，没有感染部位的具体信息。以来 靶组织中不适当的抗生素浓度可导致治疗失败， 生物体或毒性，一些研究和美国食品和药物管理局（FDA）支持测量 感染组织中的药物浓度。然而，目前检测组织药物水平的工具是侵入性的（需要 组织切除），这在人类中是困难的，并且即使在动物中也通常限于单个时间点。 我们的总体假设是，多种异质性病理状态，例如空洞，肺炎， 和肺结核（TB）中的坏死病变同时发生在同一患者中。而且这些 病变还可以具有不同的细菌负荷和抗生素暴露，其也随疾病而变化 进展和抗生素治疗。空洞是人类结核病的一个重要病理特征， 感染传播、复发和治疗后出现耐药性的公认危险因素。 虽然腔壁细菌负荷高（107-109），但其血管化不良， 胶囊因此，虽然需要足够高的抗生素水平来有效地杀死腔中的细菌，但使用 在肺结核患者的PET生物成像中，我们已经证明利福平暴露是矛盾的， 洞穴墙壁中最低的。 贝达喹啉是一种含溴的二芳基喹啉，最近被批准用于治疗多药耐药。 耐药（MDR）结核病（TB）。然而，贝达喹啉分布到感染组织（例如肉芽肿和 空洞病变）尚未得到广泛研究，而初步临床前研究报告了变异性 干酪坏死性肉芽肿小鼠的治疗反应。虽然治疗MDR非常有效， 结核病、贝达喹啉也可引起心脏事件（QT间期延长），导致安全性警告， 监管机构。因此，需要非侵入性的方法来测量生物分布。 感染组织（例如腔）和其他靶器官中的贝达喹啉，以告知适当的给药和发展 有效的抗生素治疗，毒性最小。该项目的总体目标是利用我们的 在结核病动物模型和体内PET方面的专业知识，这是一种可临床转化的技术。我们将开发高效 76 Br-贝达喹啉的放射性标记方法。使用结核分枝杆菌感染作为模型， 活体动物多室定量76 Br-贝达喹啉PET中的异质性坏死病变 和死后高分辨率/灵敏度放射自显影（<10 µm分辨率，亚纳克灵敏度） 将用于空洞性TB的动物模型，以提供详细的生物分布和时间动力学， 多室病灶内贝达喹啉暴露。这项提议填补了一个重要的研究空白 结核病药物开发，并符合NIAID结核病研究战略计划。

Current antibiotic dosing recommendations and breakpoints for drug susceptibility are based on plasma concentrations and historic measures of efficacy, without specific information at the infection sites. Since inappropriate antibiotic concentrations in target tissues can lead to treatment failure, selection of resistant organisms, or toxicity, several studies and the U.S. Food and Drug Administration (FDA) support measuring drug concentrations in infected tissues. However, current tools to detect tissue drug levels are invasive (require tissue resection), which is difficult in humans and generally limited to a single time point even in animals. Our overarching hypothesis is that multiple, heterogeneous pathological states, e.g. cavitation, pneumonia, and necrotic lesions in pulmonary tuberculosis (TB), occur simultaneously in the same patient. Moreover, these lesions can also have distinct bacterial burdens and antibiotic exposures, which also change with disease progression and antibiotic treatment. Cavitation is a key pathological feature of human TB and a well- recognized risk factor for transmission of infection, relapse, and emergence of drug resistance after treatment. While cavitary walls have high bacterial burden (107-109), they are poorly vascularized with thick fibrous capsules. Therefore, while adequately high antibiotic levels are need to effectively kill bacteria in cavities, using PET bioimaging in patients with pulmonary TB, we have demonstrated that rifampin exposure is paradoxically the lowest in cavitary walls. Bedaquiline, a bromine-containing diarylquinoline, was recently approved for the treatment of multi-drug resistant (MDR) tuberculosis (TB). However, bedaquiline distribution into infected tissues (e.g. granulomas and cavitary lesions) has not been studied extensively whilst preliminary preclinical studies have reported variability in the treatment response in mice with caseous necrotic granulomas. While highly effective in treating MDR- TB, bedaquiline can also cause cardiac events (QT-interval prolongation) leading to safety warnings by regulatory agencies. Therefore, there is a need for noninvasive methods to measure the biodistribution of bedaquiline in infected tissues (e.g. cavities) and other target organs to inform appropriate dosing and develop effective, antibiotic treatments with minimal toxicities. The overall goals of this project are to leverage our expertise in animal models of TB and in vivo PET, a clinically translatable technology. We will develop efficient radiolabeling methods for 76Br-bedaquiline. Using Mycobacterium tuberculosis infections as a model for heterogeneous necrotic-lesions in multiple-compartments, quantitative 76Br-bedaquiline PET in live animals and post-mortem high-resolution / sensitivity autoradiography (<10 µm resolution, sub-nanogram sensitivity) will be utilized in animal models of cavitary TB to provide detailed biodistribution and temporal kinetics of intralesional bedaquiline exposures in multiple-compartments. This proposal fulfills an important research gap in TB drug development and aligned with the NIAID Strategic Plan for TB Research.