A Selective Galactose–Coumarin-Derived Galectin‑3 Inhibitor Demonstrates Involvement of Galectin-3-glycan Interactions in a Pulmonary Fibrosis Model

Synthesis of doubly 3-O-coumarylmethyl-substituted thiodigalactosides from bis-3-O-propargyl-thiodigalactoside resulted in highly selective and high affinity galectin-3 inhibitors. Mutant studies, structural analysis, and molecular modeling revealed that the coumaryl substituents stack onto arginine side chains. One inhibitor displayed efficacy in a murine model of bleomycin-induced lung fibrosis similar to that of a known nonselective galectin-1/galectin-3 inhibitor, which strongly suggests that blocking galectin-3 glycan recognition is an important antifibrotic drug target.