The molecular determinants for the activities of the reported benzoic acid (SH4–54), salicylic acid (BP-1–102), and benzohydroxamic acid (SH5–07)-based STAT3 inhibitors were investigated to design optimized analogues. All three leads are based on an N-methylglycinamide scaffold, with its two amine groups condensed with three different functionalities. The three functionalities and the CH₂ group of the glycinamide scaffold were separately modified. The replacement of the pentafluorobenzene or cyclohexylbenzene, or replacing the benzene ring of the aromatic carboxylic or hydroxamic acid motif with heterocyclic components (containing nitrogen and oxygen elements) all decreased potency. Notably, the Ala-linker analogues, 1a and 2v, and the Pro-based derivative 5d, all with (R)-configuration at the chiral center, had improved inhibitory activity and selectivity against STAT3 DNA-binding activity in vitro, with IC₅₀ of 3.0 ± 0.9, 1.80 ± 0.94, and 2.4 ± 0.2 μM, respectively. Compounds 1a, 2v, 5d, and other analogues inhibited constitutive STAT3 phosphorylation and activation in human breast cancer and melanoma lines, and blocked tumor cell viability, growth, colony formation, and migration in vitro. Pro-based analogue, 5h, with a relatively polar tetrahydropyranyl (THP) ring, instead of the cyclohexyl, showed improved permeability. In general, the (R)-configuration Pro-based analogs showed the overall best profile, including physicochemical properties (e.g., microsomal metabolic stability, Caco-2 permeability), and in particular, 5d showed improved tumor-cell specificity.

中文翻译：

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基于羧酸的小分子STAT3抑制剂的接头变异与结构-活性关系分析

研究了已报道的苯甲酸（SH4-54），水杨酸（BP-1-102）和苯并异羟肟酸（SH5-07）的STAT3抑制剂的分子决定因素，以设计优化的类似物。所有三个导联均基于N-甲基甘氨酰胺支架，其两个胺基缩合成三个不同的官能团。甘氨酰胺支架的三个功能和CH ₂基团分别进行了修饰。五氟苯或环己基苯的取代，或用杂环成分（含氮和氧元素）取代芳族羧酸或异羟肟酸基序的苯环，均会降低效能。值得注意的是，Ala-linker类似物1a和2v，以及在手性中心均具有（R）构型的基于Pro的衍生物5d在体外具有更高的抑制活性和针对STAT3 DNA结合活性的选择性，IC ₅₀为3.0±0.9、1.80±0.94和2.4分别为±0.2μM。化合物1a，2v，5d和其他类似物在人乳腺癌和黑色素瘤细胞系中抑制STAT3组成型STAT3的磷酸化和激活，并在体外阻断肿瘤细胞的活力，生长，集落形成和迁移。基于专业的模拟，5h具有相对极性的四氢吡喃基（THP）环，而不是环己基，显示出改善的渗透性。通常，基于（R）-构型的类似物显示总体最佳概况，包括理化性质（例如，微粒体代谢稳定性，Caco-2通透性），特别是5d显示出改善的肿瘤细胞特异性。