Chondroitin 4-Sulfate Disaccharide-Based Inhibitors of Cathepsin S

Cathepsin S (Cat S) is a cysteine protease involved in several human diseases (i.e., autoimmune, inflammatory and cardiovascular disorders, cancer, and psoriasis) and is an important target in drug development. Emerging evidence highlights the potential of inhibiting Cat S by glycosaminoglycans, particularly chondroitin sulfates (CSs), as a promising therapeutic strategy. Given the limited and heterogeneous GAG materials from animal sources, a series of synthetic biotinylated non- or sulfated chondroitin oligomers were synthesized and assessed for their ability to inhibit Cat S. The biotinylated disaccharide C4S displayed in vitro potent inhibitory activity toward Cat S with IC50 value in the micromolar range and showed selectivity over cathepsins K and L. Molecular modeling studies suggested that only C4S dp2 but not C6S, C4,6S or non-sulfated chondroitin binds selectively to the active site of Cat S. In addition, a synthetic multivalent C4S dp2 glycosylated BSA was shown to be more efficient towards Cat S inhibition (nanomolar range) than the monovalent parent C4S dp2. Our findings also indicated that this new neoglycoconjugate displayed selectivity for Cat S vs. cysteine cathepsins expressed by differentiated THP-1 cells. This study reports a new approach for designing selective and potent inhibitors of Cat S using multivalent C4S derivatives as a molecular scaffold.