Spiropyrimidinetrione DNA Gyrase Inhibitors with Potent and Selective Antituberculosis Activity

New antibiotics with either a novel
mode of action or novel mode
of inhibition are urgently needed to overcome the threat of drug-resistant
tuberculosis (TB). The present study profiles new spiropyrimidinetriones
(SPTs), DNA gyrase inhibitors having activity against drug-resistant Mycobacterium tuberculosis (Mtb),
the causative agent of TB. While the clinical candidate zoliflodacin
has progressed to phase 3 trials for the treatment of gonorrhea, compounds
herein demonstrated higher inhibitory potency against Mtb DNA gyrase (e.g., compound 42 with IC50 =
2.0) and lower Mtb minimum inhibitor concentrations
(0.49 μM for 42). Notably, 42 and
analogues showed selective Mtb activity relative
to representative Gram-positive and Gram-negative bacteria. DNA gyrase
inhibition was shown to involve stabilization of double-cleaved DNA,
while on-target activity was supported by hypersensitivity against
a gyrA hypomorph. Finally, a docking model for SPTs with Mtb DNA gyrase was developed, and a structural hypothesis was built
for structure–activity relationship expansion.

为应对耐药结核病（drug-resistant tuberculosis, TB）带来的威胁，亟需开发具有全新作用模式或全新抑制机制的新型抗生素。本研究针对一类新型螺嘧啶三酮类化合物（spiropyrimidinetriones, SPTs）展开系统性表征，该类化合物为DNA旋转酶（DNA gyrase）抑制剂，对作为结核病病原菌的耐药结核分枝杆菌（Mycobacterium tuberculosis, Mtb）具有抗菌活性。尽管临床候选药物唑氟达星（zoliflodacin）已推进至治疗淋病的Ⅲ期临床试验，但本研究所涉及的化合物对结核分枝杆菌DNA旋转酶展现出更高的抑制活性——例如化合物42的半数抑制浓度（IC50）为2.0，且其针对结核分枝杆菌的最低抑菌浓度更低（化合物42为0.49 μM）。值得注意的是，相较于代表性革兰氏阳性菌与革兰氏阴性菌，化合物42及其类似物对结核分枝杆菌展现出选择性抗菌活性。研究证实，该类化合物对DNA旋转酶的抑制作用涉及双链断裂DNA的稳定化，而其靶点结合活性则通过gyrA功能减弱突变体（gyrA hypomorph）的超敏反应得到验证。最后，本研究构建了结核分枝杆菌DNA旋转酶与SPTs的分子对接模型，并为构效关系（structure–activity relationship）拓展提出了结构层面的假说。