Design, synthesis, and structure-activity relationships of novel flavone derivatives as tankyrase inhibitors against colorectal cancer.

Colorectal cancer (CRC) is a lethal malignancy driven by Wnt/β-catenin pathway hyperactivation. Tankyrase (TNKS) is a promising therapeutic target for CRC; however, existing inhibitors suffer from poor subtype selectivity and severe intestinal toxicity. Guided by structure-based drug design (SBDD), we developed a novel series of flavone-based TNKS inhibitors using 4'-hydroxyflavone, a plant-derived hit, as the structural scaffold. By systematically introducing diverse aliphatic amines and fluorine atoms onto the flavone B-ring, we designed and synthesized 37 derivatives. Structure-activity relationship (SAR) analysis revealed that bulky para-dialkylamides significantly improved binding affinity. Among the series, compound 19 showed the strongest TNKS1 inhibitory potency (IC50 = 40.6 nM) and >250-fold selectivity over PARP-1. Compound 21 emerged as the optimized lead, effectively suppressing SW480 CRC cell proliferation (IC50 = 6.7 μM) while maintaining a superior safety window (SI > 15) against normal NCM460 colonic epithelial cells. Mechanistically, compound 21 exerted its antitumor effects by significantly downregulating classic Wnt target genes (AXIN2, c-Myc), reversing the epithelial-mesenchymal transition (EMT), and irreversibly abolishing the long-term colony-forming capacity of CRC cells. In conclusion, compound 21 features a unique dual-pocket occupation mode and an outstanding efficacy-safety balance, providing a highly valuable structural template for developing next-generation, high-selectivity TNKS inhibitors for targeted CRC therapy.