Discovery of β-carboline derivatives as potent STAT3 dual phosphorylation inhibitor for hepatocellular carcinoma treatment.

Hepatocellular carcinoma (HCC) remains a significant clinical challenge, and targeting the dual phosphorylation of signal transducer and activator of transcription 3 (STAT3) has emerged as a promising strategy for HCC treatment. In this study, 25 novel β-carboline-benzo[b]thiophene 1,1-dioxide hybrids were designed and synthesized via structural modification of the β-carboline scaffold. Among them, compound 18 exhibited the most potent antiproliferative activity against Huh-7 cells in vitro, with an IC50 value of 1.30 ± 0.05 μM, and significantly suppressed colony formation and cell migration. Mechanistic investigations demonstrated that compound 18 directly bound to STAT3 protein with a KD value of 5.63 μM, as determined by surface plasmon resonance (SPR), and markedly inhibited its phosphorylation at both Tyr705 and Ser727 residues, consequently blocking its nuclear translocation. In addition, compound 18 impaired mitochondrial function by reducing ATP production and elevating reactive oxygen species (ROS) levels. In a Huh-7 xenograft mouse model, compound 18 administered at 7.5 mg/kg achieved a tumor inhibition rate of 55.08%. Collectively, these results indicate compound 18 as a promising STAT3 dual phosphorylation inhibitor for HCC treatment.