Isoniazid (INH) remains a cornerstone for treatment of drug susceptible tuberculosis (TB), yet the quantitative structure-activity relationships for INH are not well documented in the literature. In this paper, we have evaluated a systematic series of INH analogs against contemporary Mycobacterium tuberculosis strains from different lineages and a few non-tuberculous mycobacteria (NTM). Deletion of the pyridyl nitrogen atom, isomerization of the pyridine nitrogen to other positions, replacement of the pyridine ring with isosteric heterocycles, and modification of the hydrazide moiety of INH abolishes antitubercular activity. Similarly, substitution of the pyridine ring at the 3-position is not tolerated while substitution at the 2-position is permitted with 2-methyl-INH 9 displaying antimycobacterial activity comparable to INH. To assess the specific activity of this series of INH analogs against mycobacteria, we assayed them against a panel of gram-positive and gram-negative bacteria, as well as a few fungi. As expected INH and its analogs display a narrow spectrum of activity and are inactive against all non-mycobacterial strains evaluated, except for 4, which has modest inhibitory activity against Cryptococcus neoformans. Our findings provide an updated analysis of the structure-activity relationship of INH that we hope will serve as useful resource for the community.

异烟肼 (INH) 仍然是治疗药物敏感结核病 (TB) 的基石，但文献中尚未详细记录 INH 的定量构效关系。在本文中，我们评估了一系列 INH 类似物对来自不同谱系的当代结核分枝杆菌菌株和一些非结核分枝杆菌 (NTM) 的系统性影响。吡啶基氮原子的缺失、吡啶氮异构化到其他位置、用等排杂环取代吡啶环以及修饰INH的酰肼部分会消除抗结核活性。类似地，吡啶环在3位上的取代是不能容忍的，而在2位上的取代允许用2-甲基-INH 9进行，其抗分枝杆菌活性与INH相当。为了评估这一系列 INH 类似物针对分枝杆菌的比活性，我们对一组革兰氏阳性和革兰氏阴性细菌以及一些真菌进行了测定。正如预期的那样，INH 及其类似物显示出较窄的活性谱，并且对所评估的所有非分枝杆菌菌株均无活性，但4 菌株除外，该菌株对新型隐球菌具有适度的抑制活性。我们的研究结果提供了对 INH 结构-活性关系的最新分析，我们希望这能为社区提供有用的资源。