Fluorescent mu selective opioid ligands from a mixture based cyclic peptide library.

Area of Science:

• Medicinal Chemistry
• Peptide Chemistry
• Neuroscience

Background:

• Cyclic peptides are valuable scaffolds for drug discovery due to their conformational rigidity and metabolic stability.
• The mu opioid receptor is a key target for pain management, but current therapeutics have limitations.

Purpose of the Study:

• To generate and screen a positional scanning cyclic peptide library to identify novel ligands for the mu opioid receptor.
• To synthesize and characterize high-affinity cyclic peptides targeting the mu opioid receptor.

Main Methods:

• A positional scanning cyclic peptide library was synthesized using a thioester scaffold, incorporating diverse L- and D-amino acids at variable positions.
• The library was screened using a binding assay against the mu opioid receptor.
• Hit compounds were further synthesized and characterized, including isomer analysis.

Main Results:

• Screening identified active amino acid combinations for mu opioid receptor binding.
• Two cyclic peptides demonstrated high binding affinities.
• The most potent cyclic peptide showed a side chain-to-tail isomer with a binding affinity of 14 nM, outperforming its head-to-tail isomer (39 nM).
• Both identified isomers exhibited selectivity for the mu-opioid receptor.

Conclusions:

• Positional scanning is an effective strategy for identifying potent cyclic peptide ligands.
• Novel cyclic peptides with high affinity and selectivity for the mu opioid receptor were discovered.
• The findings provide a basis for developing new analgesics with improved profiles.