Structure-Guided Design, Synthesis, and Evaluation of Novel 6-Methoxyquinoline-4-carboxamide Derivatives as First-in-Class Nano-Molar B3GAT3 Inhibitors for the Treatment of Hepatocellular Carcinoma

Abstract Beta-1,3-glucuronosyltransferase (B3GAT3) is overexpressed in hepatocellular carcinoma (HCC) and correlates with poor prognosis, serving as a desirable anti-HCC target. Based on our micromolar lead TMLB-C16 (IC50 = 6.22−6.53 μM, KD = 3.96 μM), 60 novel derivatives were designed via systematic structure−activity relationship optimization. The optimized candidate TMLB-G9 is the first nanomolar B3GAT3 inhibitor bearing a 6-methoxyquinoline-4-carboxamide scaffold. It exhibits stronger B3GAT3 binding affinity (KD = 0.72 μM) than both TMLB-C16 and natural substrate UDP-GlcUA (KD = 1.32 μM). TMLB-G9 exhibits potent antiproliferative activity against Huh7 and Hep3B cells (IC50 = 0.31−0.36 μM) and broad-spectrum antitumor efficacy. It suppresses HCC colony formation, migration, and invasion, while inducing G0/G1 arrest and apoptosis. With good in vivo tolerance and safety, TMLB-G9 exhibited superior anti-HCC activity to TMLB-C16 in two HCC xenograft models. In conclusion, TMLB-G9 is a promising B3GAT3 inhibitor worthy of further development for HCC therapy.