The current work developed diverse novel napabucasin-melatonin hybrids as potent STAT3 inhibitors. Several biological studies have suggested many compounds demonstrating potent inhibition against different tumor cells. Among these, compound 7e depicted enhanced inhibition against HepG2, MDA-MB-231, and A549 cells than napabucasin, with IC₅₀ values of 1.06, 1.38, and 1.3 µM, respectively. Based on fluorescence polarization analysis, compound 7e was bound to the SH2 domain in STAT3, with an IC₅₀ value of 12.95 µM. Molecular docking further confirmed the 7e binding mode inside the SH2 domain of STAT3. Further mechanistic studies indicated that 7e inhibited the activation of STAT3 (Y705), and thus reduced the expression of STAT3 downstream genes (CyclinD1, Bcl-2 and c-Myc) instead of affecting p-STAT1 expression. Meanwhile, the phosphorylation levels of its upstream kinases JAK2 and bypass kinase Erk1/2 remain unaffected. Simultaneously, 7e induced cancer cell apoptosis in a concentration-dependent manner. Significantly, 20 mg/kg (i.p.) compound 7e suppressed the mouse HepG2 xenograft development in vivo without body weight loss, suggesting that it could be an effective antitumor agent.

目前的工作开发了多种新型萘帕布卡星-褪黑激素杂化物作为有效的 STAT3 抑制剂。几项生物学研究表明，许多化合物对不同的肿瘤细胞表现出有效的抑制作用。其中，化合物7e对 HepG2、MDA-MB-231 和 A549 细胞的抑制作用强于萘帕布卡星，IC ₅₀值分别为 1.06、1.38 和 1.3 µM。基于荧光偏振分析，化合物7e与 STAT3 中的 SH2 结构域结合，IC ₅₀值为 12.95 µM。分子对接进一步证实了STAT3的SH2结构域内部的7e结合模式。进一步的机理研究表明7e抑制 STAT3 (Y705) 的激活，从而降低 STAT3 下游基因（CyclinD1、Bcl-2 和 c-Myc）的表达，而不是影响p -STAT1 的表达。同时，其上游激酶 JAK2 和旁路激酶 Erk1/2 的磷酸化水平不受影响。同时，7e以浓度依赖性方式诱导癌细胞凋亡。值得注意的是，20 mg/kg (ip) 化合物7e在体内抑制了小鼠 HepG2 异种移植物的发育而体重没有减轻，这表明它可能是一种有效的抗肿瘤剂。