E-64c-Hydrazide Based Cathepsin C Inhibitors: Optimizing the Interactions with the S1'-S2' Area

Area of Science:

• Biochemistry
• Pharmacology
• Immunology

Background:

• Neutrophil serine proteases (elastase, proteinase 3, cathepsin G) are activated by cathepsin C, contributing to inflammatory disorders like COPD.
• Cathepsin C inhibition presents a therapeutic strategy for neutrophil-driven inflammatory conditions.

Purpose of the Study:

• To optimize a covalent cathepsin C inhibitor for enhanced affinity and selectivity.
• To investigate the S1'-S2' area of the inhibitor for improved ligand binding.

Main Methods:

• Development of a covalent cathepsin C inhibitor based on E-64c-hydrazide.
• Combinatorial approach to explore the S1'-S2' binding region.
• Utilized U937 neutrophil precursor cell line for in vitro testing.

Main Results:

• Identified Nle-tryptamide as a superior ligand for the S1'-S2' area compared to Leu-isoamylamide.
• The optimized inhibitor effectively blocked intracellular cathepsin C activity in U937 cells.
• Demonstrated suppression of neutrophil elastase activation by the inhibitor.

Conclusions:

• A novel, optimized covalent cathepsin C inhibitor demonstrates potential for treating inflammatory diseases.
• The inhibitor successfully targets cathepsin C, reducing downstream activation of key neutrophil proteases.
• Further development of this inhibitor may offer a therapeutic avenue for COPD and related conditions.