Multi-mode imaging to underpin a drug development pipeline for a new, peptide class of antibiotics

使用静脉内递送的杀菌AMP成功治疗细菌性肺部感染是极其罕见的。事实上，在已知已进入临床或临床前研究的36种AMP中，只有7种正在或正在开发用于静脉内递送（3种已停产），并且没有一种被认为使用直接抗菌机制在体内起作用。因此，成功开发这种新型抗生素的途径远不清楚，需要新的方法来了解药代动力学（PK），生物分布和药效学（PD），任何毒性的起源，与先天免疫系统的相互作用以及这类抗生素根除细胞内细菌的能力，这些细菌越来越被怀疑是临床失败的原因，我们认为多模式成像方法是解决这些实质性障碍的关键。具体而言，该项目旨在生产和合成一组不同标记的AMP类似物，这些类似物将能够在体外和体内进行荧光成像和体内放射性药物示踪。使用固相合成将罗丹明或其衍生物连接到AMP引线上，将使得能够研究上皮细胞、巨噬细胞和中性粒细胞中肽的（共）定位，以了解任何细胞毒性的机制、对细胞因子释放的影响和到达细胞内病原体的能力。近红外（700-900 nm）荧光标记将使时间分辨的AMP的生物分布研究提供静脉注射或通过干粉吹入肺。通过缀合的六齿羟基吡啶酮（HOPO）螯合剂，用68 Ga标记用于PET成像的AMP将增加灵敏度，使得能够进行感染解决的时间分辨研究，并且可能导致选择性但非特异性的检测方法。

Successful therapy of a bacterial lung infection using a bactericidal AMP delivered i.v. is extremely rare. Indeed, of thirty-six AMPs known to have entered clinical or preclinical studies, only seven are or were being developed for i.v. delivery (three discontinued) and none are thought to act in vivo using a direct antibacterial mechansism. The pathway for successful development of this new classs of antibiotics is therefore far from clear with new approaches needed to understand pharmacokinetics (PK), biodistribution and pharmacodynamics (PD), the origin of any toxicity, interactions with the innate immune system and the ability of this class to eradicate intracellular bacteria which are increasingly suspected as being the cause of clinical failure, relapses and resistance after antibiotic therapy.We propose that a multi-mode imaging approach is the key to addressing these substantial barriers. Specifically, this project aims to produce and characterise a panel of differently labelled AMP analogues that will enable in vitro and in vivo fluorescence imaging and in vivo radiopharmaceutical tracing. Attaching rhodamine or its derivatives to the AMP leads, using solid-phase synthesis, will enable the study of (co)localisation of the peptides in epithelial cells, macrophage and neutrophil to understand the mechanisms of any cytotoxicity, impact on cytokine release and ability to reach intracellular pathogens. Near-infrared (700-900 nm) fluorescent labels will enable time-resolved biodistribution studies of AMP delivered i.v. or via dry-powder insufflation to the lung. Labelling AMPs for PET imaging with 68Ga, via a conjugated hexadentate HydrOxyPyridinOne (HOPO) chelator, will increase sensitivity, enable time-resolved studies of infection resolution and may lead to a selective but non-specific means of