Melanocortin 1 Receptor Agonists Based on a Bivalent, Bicyclic Peptide Framework

Area of Science:

• Medicinal Chemistry
• Peptide Design
• Pharmacology

Background:

• Melanocortin receptors (MCRs) are implicated in various physiological processes.
• Developing selective MCR ligands is crucial for therapeutic applications.
• Sunflower trypsin inhibitor 1 (SFTI-1) serves as a novel scaffold for peptide ligand design.

Purpose of the Study:

• To design and synthesize novel bivalent melanocortin receptor ligands.
• To evaluate the potency and selectivity of these ligands at human MCRs (hMCRs).
• To explore the structure-activity relationships of SFTI-1-based bivalent ligands.

Main Methods:

• Peptide synthesis and modification of SFTI-1 scaffold.
• In vitro binding assays to determine receptor affinity (Ki).
• Functional assays to measure agonist activity (pEC50, EC50).

Main Results:

• Novel bivalent ligands based on SFTI-1 were successfully designed.
• Compound 6 demonstrated high picomolar agonist activity at hMC1R (pEC50 > 10.3).
• Compound 6 exhibited >30-fold selectivity for hMC1R over other hMCR subtypes (hMC3R, hMC4R, hMC5R).

Conclusions:

• Bivalent SFTI-1-based ligands represent a promising class of potent and selective hMC1R agonists.
• The incorporation of pharmacophores into the SFTI-1 scaffold significantly enhanced agonist activity.
• Structural modeling provides insights into ligand-receptor interactions for future drug development.