Discovery of Phospopantetheinyl Transferse Inhibitors Against Mycobacterium tuberculosis

摘要 结核病(TB)对医学科学提出了持续的全球挑战，只有 接近了。由于即使是“常规”结核病治疗的时间长短，以及现有药物的使用年限--这有助于 毁灭性抗药性疾病的出现--新药的发现，特别是那些 通过新的行动机制发挥作用，已变得至关重要。2019年初，包括本实验室在内的一个团队 据报道，AU 8918是第一个高质量的4‘-磷酸铁氨酰转移酶(PptT)抑制剂。PptT，这是 催化将4‘-磷酸铁蛋白部分放置在客户载体蛋白上，这对 分枝杆菌脂肪酸的生物合成和毒力因子。PptT是一种有价值的抗结核靶点 因为(1)它对结核分枝杆菌(Mtb)在体外和小鼠体内的生存是必不可少的，(2)它是发散的 来自最接近的宿主同源基因，以及(3)它与已建立的结核病药物的所有靶点不同。此外，ITS 抑制已被证明能有效地杀死结核分枝杆菌，包括多重和广泛耐药的变种和 (5)阻断小鼠结核分枝杆菌的生长；(6)保护其他细菌或哺乳动物细胞。主要的命中化合物， AU8918对结核分枝杆菌的IC50值为2.3M，体外对结核分枝杆菌的MIC90值为3.1M。 并具有一些与作为候选药物的进步相一致的物理特征，但患有 偏离靶点的心脏毒性可能与钠通道阻断有关。 本提案旨在支持三个实验室之间的持续合作，这些实验室共享 共同的目标是设计、合成和表征适合临床前开发的PptT抑制剂。这个 与Mtb PptT结合的AU 8918及其类似物的五种高分辨共晶结构的可用性已经被 用来建立用于模拟初步评估的稳健的计算机建模协议。几个 提出了创造新的PptT抑制剂的途径，包括(1)对AU 8918的合成孔径雷达探测，(2)发现 以及探索通过对AU 8918的氨基尿素亚基进行生物等位置换而产生的新支架， 以及(3)正在进行的针对PptT的筛选产生的新热门。我们将通过(1)生物化学来描述抑制剂 PptT抑制，(2)抑制剂·PptT共晶体的X射线结晶学，以及(3)先进的生化 表征(包括细胞内巨噬细胞活性测量，通过以下方式验证目标活性 基因敲除/基因敲除研究，针对非目标责任的安全性分析，药代动力学和代谢 特性、代谢组学和协同作用研究)。该项目的最终目标是确定1-2个高级 用于结核杆菌感染小鼠体内研究的化合物，具有以下性质：(&lt；0.1M 对Pptt的效力，&lt；1M MIC90对结核分枝杆菌的效力，保留积极的物理性质，缺乏 心脏毒性或相关钙和钠通道的活性(&gt；30M抑制)。

Abstract Tuberculosis (TB) presents an ongoing global challenge to medical science that will only be met by multiple approaches. Due to the length of even “routine” TB therapy and the age of existing drugs – which contributes to the emergence of devastating resistant forms of the disease – the discovery of new drugs, especially those that function by new mechanisms of action, has become critical. In early 2019, a team including the present laboratory reported AU 8918 as the first high-quality inhibitor of 4'-phosphopantetheinyl transferase (PptT). PptT, which catalyzes the placement of a 4'-phosphopantetheinyl moiety onto a client carrier protein, is essential for the biosynthesis of mycobacterial fatty acids and virulence factors. PptT represents a valuable anti-TB target because (1) it is essential for mycobacterial tuberculosis (Mtb) survival in vitro and in mice, (2) it is divergent from the closest host ortholog, and (3) it is distinct from all targets of established TB drugs. In addition, its inhibition has been shown (4) to effectively kill Mtb including multi- and extensively-drug-resistant variants and (5) to block Mtb growth in mice, while (6) sparing other bacterial or mammalian cells. The primary hit compound, AU 8918, has an IC50 of 2.3 M in biochemical assays of PptT inhibition, a MIC90 of 3.1 M against Mtb in vitro, and has some physical properties features consistent with advancement as a drug candidate, but suffers from off-target cardiotoxicity likely associated with sodium channel blockade. The present proposal seeks to support an ongoing collaboration between three laboratories that share the common goal to design, synthesize, and characterize PptT inhibitors suitable for pre-clinical development. The availability of five high resolution co-crystal structures of AU 8918 and analogs bound to Mtb PptT has been leveraged to establish a robust in silico modeling protocol for the preliminary assessment of analogs. Several avenues to create novel PptT inhibitors are proposed, including (1) SAR exploration of AU 8918, (2) discovery and exploration of new scaffolds arising from bioisosteric replacements of the amidinourea subunit of AU 8918, and (3) new hits arising from an ongoing screen against PptT. We will characterize inhibitors by (1) biochemical PptT inhibition, (2) X-ray crystallography of inhibitor•PptT co-crystals, and (3) advanced biochemical characterization (including intracellular macrophage activity measurements, verification of on-target activity by knockdown/knockout studies, safety profiling against off-target liabilities, pharmacokinetic and metabolic characterization, metabolomics, and synergy studies). The final goal of the project is to identify 1–2 advanced compounds for advancement to in vivo studies in Mtb infected mice, having the following properties: (<0.1 M potency against PptT, <1 M MIC90 against Mtb, retention of positive physical properties, and lacking cardiotoxicity or activity (>30 M inhibition) at relevant Ca and Na channels.