Inhibition of galectins with small molecules

Evidence that the galectin family of proteins plays crucial roles in cancer, inflammation, and immunity has accumulated over the last decade. The galectins have consequently emerged as interesting drug targets. A majority of galectin functions occurs by means of cross-linking glycoproteins and by doing so controlling glycoprotein cellular localization and residence times. The glycoprotein cross-linking occurs when galectin dimers or multimers, or galectins with two binding sites, bind galactose-containing glycans of the glycoproteins. Such galectin-glycan interactions have been successfully blocked with compounds having multivalent presentation of galactose, lactose, or N-acetyllactosamine, with peptides, and with small carbohydrate (galactose) derivatives. This review summarizes and analyzes attempts to develop efficient and selective small-molecule galectin inhibitors through derivatization of monosaccharides, mainly galactosides, with non-carbohydrate structures that protrude into subsites adjacent to the core-conserved galactose-recognizing site of the galectins.