Can Cysteine Protease Cross-Class Inhibitors Achieve Selectivity?

Area of Science:

• Biochemistry
• Medicinal Chemistry
• Drug Discovery

Background:

• Cysteine proteases are crucial therapeutic targets for diverse diseases, including parasitic infections and cancer.
• These enzymes share a common mechanism involving an encounter complex and nucleophilic attack by a catalytic cysteine residue.
• Modulating cysteine protease activity often involves covalent modification, presenting challenges in achieving selectivity and avoiding off-target effects.

Purpose of the Study:

• To explore strategies for achieving selectivity in small molecule inhibitors targeting cysteine proteases.
• To evaluate the potential of reversible versus irreversible covalent inhibitors in mitigating off-target effects.
• To discuss target- and ligand-based design approaches for cysteine protease inhibitors, including repurposing strategies.

Main Methods:

• Review of existing literature on cysteine protease inhibitors and their mechanisms of action.
• Analysis of target- and ligand-based drug design principles.
• Discussion of structure-activity relationships for inhibitors targeting cathepsins, cruzain, rhodesain, and falcipain-2.

Main Results:

• Covalent modification is a preferred method for modulating cysteine protease activity.
• Achieving selectivity remains a significant challenge due to the conserved catalytic mechanisms.
• Both reversible and irreversible covalent inhibitors present distinct advantages and disadvantages regarding selectivity and off-target effects.

Conclusions:

• Designing selective cysteine protease inhibitors requires careful consideration of the target enzyme's active site and the inhibitor's chemical properties.
• Repurposing inhibitors across different cysteine proteases is a viable strategy, but requires thorough validation.
• Further research into novel design strategies is needed to overcome selectivity challenges and develop safer, more effective therapeutics.