10-Ketonaltrexone and 10-ketooxymorphone

Area of Science:

• Pharmacology
• Medicinal Chemistry
• Neuroscience

Background:

• Opioid receptor selectivity is crucial for developing effective analgesics with reduced side effects.
• Ethylketocyclazocine exhibits greater kappa/mu selectivity compared to cyclazocine.
• Understanding structure-activity relationships of opioid ligands informs drug design.

Purpose of the Study:

• To synthesize and evaluate the opioid receptor binding affinity and functional potency of 10-ketonaltrexone and 10-ketooxymorphone.
• To determine the impact of a 10-keto group modification on opioid receptor interactions.
• To compare the pharmacological profiles of modified compounds with their parent analogs.

Main Methods:

• Synthesis of 10-ketonaltrexone and 10-ketooxymorphone from naltrexone 3-methyl ether and oxycodone.
• In vitro brain binding assays to assess affinity for mu, kappa, and delta opioid receptors.
• In vitro bioassays using guinea pig ileum and mouse vas deferens preparations to evaluate functional potency.

Main Results:

• 10-Ketonaltrexone and 10-ketooxymorphone exhibited significantly lower potency at mu-opioid receptors compared to naltrexone and oxymorphone.
• These modified compounds demonstrated minimal affinity for kappa and delta opioid receptors.
• The introduction of the 10-keto group substantially diminished overall opioid effects across all tested receptor subtypes.

Conclusions:

• The 10-keto group modification in naltrexone and oxymorphone leads to a significant reduction in opioid activity.
• These findings suggest that the 10-keto moiety negatively impacts ligand binding and/or efficacy at mu, kappa, and delta opioid receptors.
• This structural modification could be a strategy to develop opioid ligands with altered receptor interaction profiles.