pKa of opioid ligands as a discriminating factor for side effects
- The non-selective activation of central and peripheral opioid receptors is a major shortcoming of currently available opioids. Targeting peripheral opioid receptors is a promising strategy to preclude side effects. Recently, we showed that fentanyl-derived μ-opioid receptor (MOR) agonists with reduced acid dissociation constants (pKa) due to introducing single fluorine atoms produced injury-restricted antinociception in rat models of inflammatory, postoperative and neuropathic pain. Here, we report that a new double-fluorinated compound (FF6) and fentanyl show similar pKa, MOR affinity and [35S]-GTPγS binding at low and physiological pH values. In vivo, FF6 produced antinociception in injured and non-injured tissue, and induced sedation and constipation. The comparison of several fentanyl derivatives revealed a correlation between pKa values and pH-dependent MOR activation, antinociception and side effects. An opioid ligand's pKa value may be used as discriminating factor to design safer analgesics.
Author: | Giovanna Del Vecchio, Dominika Labuz, Julia Temp, Viola Seitz, Michael Kloner, Roger Negrete, Antonio Rodriguez-Gaztelumendi, Marcus Weber, Halina Machelska, Christoph Stein |
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Document Type: | Article |
Parent Title (English): | Scientific Reports |
Volume: | 9 |
First Page: | 19344 |
Year of first publication: | 2019 |
DOI: | https://doi.org/10.1038/s41598-019-55886-1 |