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

成功的治疗细菌性肺部感染使用抗菌AMP输注是极其罕见的。事实上，在已知已进入临床或临床前研究的36种抗菌药物中，只有7种正在或正在开发用于静脉给药（3种已停止），而且没有一种被认为是通过直接抗菌机制在体内起作用的。因此，成功开发这类新型抗生素的途径远未明确，需要新的方法来了解药代动力学（PK）、生物分布和药理学（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，这些细菌越来越多地被怀疑是抗生素治疗后临床失败、复发和耐药的原因。我们建议多模式成像方法是解决这些实质性障碍的关键。具体来说，该项目旨在生产和表征一组不同标记的AMP类似物，这将使体外和体内荧光成像以及体内放射性药物追踪成为可能。将罗丹明或其衍生物连接到AMP引线上，使用固相合成技术，将能够研究肽在上皮细胞、巨噬细胞和中性粒细胞中的（co）定位，从而了解任何细胞毒性的机制，对细胞因子释放的影响以及到达细胞内病原体的能力。近红外（700-900 nm）荧光标记将使静脉注射或通过干粉注入肺部的AMP的时间分辨生物分布研究成为可能。用68Ga标记AMPs用于PET成像，通过共轭六齿羟基吡啶酮（HOPO）螯合剂，将提高灵敏度，使感染分辨率的时间分辨研究成为可能，并可能导致选择性但非特异性的方法

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