Identification of C3b-Binding Small-Molecule Complement Inhibitors Using Cheminformatics.

Area of Science:

• Biochemistry
• Immunology
• Drug Discovery

Background:

• The complement system is a critical part of innate immunity, involving a cascade of proteins.
• Its dysregulation is linked to autoimmune, inflammatory, and degenerative diseases.
• Small-molecule inhibitors are underrepresented in complement-targeted therapeutics.

Purpose of the Study:

• To employ a cheminformatics approach for discovering novel small-molecule complement inhibitors.
• To identify compounds targeting the central complement component, C3b.
• To validate and characterize the inhibitory mechanism of identified compounds.

Main Methods:

• In silico screening of small molecules against C3b based on structural and functional data.
• Surface plasmon resonance (SPR) for validating C3b-binding compounds.
• Biochemical assays to assess inhibition of C3b binding and complement function.
• Mechanistic studies to determine the mode of action of inhibitors.

Main Results:

• Identified 45 small molecules predicted to bind C3b.
• Validated seven dose-dependent C3b-binding compounds using SPR.
• Demonstrated that several compounds interfere with C3b ligand binding.
• Identified cmp-5 as a complement inhibitor acting at C5 activation.

Conclusions:

• This study presents a successful cheminformatics-driven drug discovery strategy for complement inhibitors.
• Identified a novel class of C3b-binding small molecules with complement inhibitory potential.
• Demonstrated cmp-5 as a promising complement inhibitor targeting C5 activation.