Exploiting bacterial uptake as a universal platform for antibacterial development

 描述（由申请人提供）：多重耐药革兰氏阴性病原体已被CDC和WHO宣布为主要的新出现的健康危机。这些微生物（包括铜绿假单胞菌、鲍曼不动杆菌和超广谱β-内酰胺酶（ESBL）肠杆菌科）的感染与抗生素敏感微生物的感染相比，死亡率增加约60%。令人担忧的是，耐药形式的感染率正在稳步攀升，目前在美国的一些地区已超过20%。在这种情况下，迫切需要新型抗菌剂。 针对革兰氏阴性病原体的新型铅发现所面临的最重要障碍是通过外膜的药物渗透性差，加上由于冗余外排泵系统导致的高药物外排率，因为它阻止了细胞内药物积累并因此阻止了整个细胞活性。在基于靶点的药物发现工作中的重大投资已经确定了许多针对保守细菌酶靶点的有效线索，但是革兰氏阴性病原体中的低细胞内药物浓度注定了它们的发展。在将有效的生物化学效力转化为有效的细胞活性以及因此无毒性的体内活性方面的这些挑战已经在整个行业中被注意到，并且一致地导致放弃这种方法的战略决策，尽管存在丰富的其他有前途的抗菌先导物。将这种药物先导物递送到细菌细胞质中的方法将是转化，因为它将利用已经在优化这种先导物方面进行的巨大投资。此外，可以应用于任何此类铅的这种输送的通用平台将改变抗生素管道的状态。 我们认为，利用天然的，主动的细菌摄取系统是一个潜在的强大的战略，可以作为一个通用的平台，提供小分子进入细菌细胞质。通过将对其同源细菌酶靶有效的小分子抗生素缀合至由这些摄取系统输入的因子，可以实现抗生素的足够的细胞内浓度。我们提出了一个新的系统，建立在高度保守和冗余的维生素B12摄取系统在铜绿假单胞菌。这些系统有效地将钴胺素衍生物从细胞外环境转运到细胞质，并且能够转运一系列钴胺素衍生物。我们将开发优化的维生素B12抗菌共轭物，这些共轭物被编程为最佳暴露和最小化宿主细胞摄取的毒性。此外，我们将利用高度优化的新型抗菌药物和先导药物，其对革兰氏阴性菌的开发障碍仅是作为货物的细胞质递送。该项目的成功实施不仅将为IND研究提供新型革兰氏阴性抗菌药物，还将证明主动转运偶联药物递送方法在改变抗菌药物发现方面的潜力。

 DESCRIPTION (provided by applicant): Multidrug resistant Gram-negative pathogens have been declared a leading, emerging health crisis by the CDC and WHO. Infections with these organisms, including Pseudomonas aeruginosa, Acinetobacter baumanni, and extended-spectrum beta-lactamase (ESBL) Enterobacteriaceae, carry ~60% increased mortality compared to infection with antibiotic-sensitive organism. Alarmingly, the prevalence of infection with resistant forms is steadily climbing, now >20% in some regions of the United States. In this setting, novel antibacterial agents are desperately needed. The most significant hurdle facing novel lead discovery against Gram-negative pathogens is poor drug permeation through the outer membrane, coupled with high rates of drug efflux due to redundant efflux pump systems, as it prevents intracellular drug accumulation and thus whole cell activity. Significant investments in target-based drug discovery efforts have identified many potent leads against conserved bacterial enzyme targets, but low intracellular drug concentrations in Gram-negative pathogens have doomed their development. These challenges in translating potent biochemical potency to effective cellular activity and thus in vivo activity without toxicity have been noted across the industry and uniformly resulted in strategic decisions to abandon this approach, despite the abundance of otherwise promising antibacterial leads. An approach to deliver such drug leads into the bacterial cytoplasm would be transforming, as it would leverage the tremendous investment that has already been made in the optimization of such leads. Further, a general platform for such delivery that could be applied to any such lead would transform the state of the antibiotic pipeline. We suggest that exploitation of native, active bacterial uptake systems is a potentially powerful strategy that can serve as a universal platform to deliver small molecules into the bacterial cytoplasm. By conjugating small molecule antibiotics that are potent for their cognate bacterial enzymatic target to the factor that is imported by these uptake systems, sufficient intracellular concentrations of the antibiotic can be achieved. We propose a novel system founded on the highly conserved and redundant Vitamin B12 uptake systems in P. aeruginosa. These systems efficiently transport cobalamin derivatives from the extracellular environment to the cytoplasm and are capable of transporting a range of cobalamin derivatives. We will develop optimized Vitamin B12-antibacterial conjugates that are programmed for optimal exposure and minimized toxicities from host cell uptake. In addition, we will leverage highly optimized, novel antibacterial drugs and leads whose barrier to development against Gram-negative bacteria is only cytoplasmic delivery as cargos. The successful delivery of this program will not only provide novel Gram-negative antibacterial agents poised for IND-enabling studies, but will also demonstrate the potential of active transport conjugate drug delivery approaches to transform antibacterial drug discovery.