Ketoamide-based inhibitors of cysteine protease, cathepsin K: P3 modifications

Area of Science:

• Biochemistry
• Pharmacology
• Medicinal Chemistry

Background:

• Osteoporosis is a skeletal fragility disease.
• Cathepsin K (a lysosomal cysteine protease) drives osteoclast bone resorption.
• Inhibiting cathepsin K offers a potential therapeutic strategy for osteoporosis.

Purpose of the Study:

• To investigate the S3 subsite's spatial tolerance using sterically demanding P3 substituents.
• To identify novel cathepsin K inhibitors with improved potency and selectivity.

Main Methods:

• Synthesis and evaluation of various P3 substituents, including sulfur and oxygen-linked heterocycles.
• Testing inhibitor potency against cathepsin K.
• Assessing selectivity against other cathepsin proteases.

Main Results:

• Sterically demanding P3 substituents were well-tolerated at the S3 subsite.
• Novel inhibitors demonstrating potent cathepsin K inhibition were discovered.
• Several compounds exhibited good selectivity ratios against other cathepsins.

Conclusions:

• The S3 subsite accommodates significant steric bulk, enabling the design of potent and selective cathepsin K inhibitors.
• Modifications at the P3 position are a viable strategy for optimizing drug-like properties in osteoporosis therapeutics.
• These findings advance the development of novel treatments for osteoporosis by targeting bone resorption pathways.