In vitro pharmacology of fentanyl analogs at the human mu opioid receptor and their spectroscopic analysis

Abstract

Opioids are widely misused and account for almost half of overdose deaths in the United States. The cost in terms of lives, health care, and lost productivity is significant and has been declared a national crisis. Fentanyl is a highly potent mu opioid receptor (MOR) agonist and plays a significant role in the current opioid epidemic; fentanyl and its analogs (fentalogs) are increasingly becoming one of the biggest dangers in the opioid crisis. The availability of fentalogs in the illicit market is thought to play a significant role in the recent increase in opioid‐related deaths. Although there is both rodent homolog in vivo and in vitro data for some fentalogs, prior to this publication very little was known about the pharmacology of many of these illicit compounds at the human MOR (hMOR). Using gas chromatography–mass spectrometry, nuclear magnetic resonance spectroscopy, and in vitro assays, this study describes the spectral and pharmacological properties of 34 fentalogs. The reported spectra and chemical data will allow for easy identification of novel fentalogs in unknown or mixed samples. Taken together these data are useful for law enforcement and clinical workers as they will aid in the identification of fentalogs in unknown samples and can potentially be used to predict physiological effects after exposure.

Activation of the μ‐opioid receptor by alicyclic fentanyls: Changes from high potency full agonists to low potency partial agonists with increasing alicyclic substructure

“…To the best of our knowledge fentanyl, morphine, and buprenorphine have never been compared using an assay based on the aequorin system, but a few studies using human receptors have been conducted using other reporting systems. Lipinski et al 5 and Hassanien et al 23 reported binding affinities of fentanyl of 1.2 and 1.6 nM, respectively. Using a GTPγS binding assay, Olson et al 9 used the same cell line as in this study and determined the EC 50 values for morphine and buprenorphine to be 130 and < 0.1 nM, respectively with efficacies of 96% and 35% (compared with endomorphine‐2).…”

“…Using a GTPγS binding assay, Olson et al 9 used the same cell line as in this study and determined the EC 50 values for morphine and buprenorphine to be 130 and < 0.1 nM, respectively with efficacies of 96% and 35% (compared with endomorphine‐2). Also using a GTPγS binding assay, Hassanien et al 23 reported an EC 50 value of 32 nM for fentanyl, while the Drug Enforcement Administration reported EC 50 values of 32 nM and 17 nM for fentanyl and morphine, respectively. Using assays based on cAMP, Kuo et al 11 reported IC 50 values of 180, 0.2, and 1 nM for morphine, buprenorphine, and fentanyl, respectively, while Yu et al 10 reported EC 50 values of 5.3 and 0.02 nM for morphine and buprenorphine, respectively.…”

“…The binding affinity of cyclopropylfentanyl has been reported as 0.088, 1.2 0.77, and 2.4 nM in different assays 5,23,24 . In addition, Hassanien et al 23 reported the binding affinities for cyclobutyl‐ and cyclopentylfentanyl as 6.2 and 13 nM, respectively. Hassanien et al 23 also reported EC 50 values from their GTPγS binding assay as 55, 160, and 600 nM for cyclopropyl‐, cyclobutyl‐, and cyclopentylfentanyl, respectively.…”

“…The structure–activity relationships for fentanyl analogs have been investigated and reviewed 12,20–23 . The binding affinity of cyclopropylfentanyl has been reported as 0.088, 1.2 0.77, and 2.4 nM in different assays 5,23,24 . In addition, Hassanien et al 23 reported the binding affinities for cyclobutyl‐ and cyclopentylfentanyl as 6.2 and 13 nM, respectively.…”

“…In addition, Hassanien et al 23 reported the binding affinities for cyclobutyl‐ and cyclopentylfentanyl as 6.2 and 13 nM, respectively. Hassanien et al 23 also reported EC 50 values from their GTPγS binding assay as 55, 160, and 600 nM for cyclopropyl‐, cyclobutyl‐, and cyclopentylfentanyl, respectively. The corresponding efficacies were 75%, 61%, and 41% (compared with 10 μM [D‐Ala2, N‐MePhe4, Gly‐ol]‐enkephalin, DAMGO).…”