Screening for Galectin-3 Inhibitors from Synthetic Lacto-N-biose Libraries Using Microscale Affinity Chromatography Coupled to Mass Spectrometry

The synthesis and screening of two β-d-Galp-(1-3)-β-d-GlcpN (lacto-N-biose) disaccharide libraries are reported. Solution-phase synthetic modifications at the HO-2‘ and NH positions were performed in an effort to enhance the affinity toward galectin-3, a galactose-binding protein involved in tumor metastasis, apoptosis, and inflammation. The libraries were screened for galectin-3 binding by microscale frontal affinity chromatography coupled to mass spectrometry (FAC/MS) allowing for rapid ranking of the different inhibitors and the determination of the galectin-3 binding K d's. Compounds bearing a hydrophobic substituent on the NH group showed the highest affinity for the lectin. The N-naphthoyl derivative (K d = 10.6 μM) was the best inhibitor with a 7 times increased affinity as compared to the N-acetyl parent compound (K d = 73.3 μM).