MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate], a derivative of the indole alkaloid mitragynine: a novel dual-acting mu- and kappa-opioid agonist with potent antinociceptive and weak rewarding effects in mice

Neuropharmacology. 2008 Aug;55(2):154-65. doi: 10.1016/j.neuropharm.2008.05.003. Epub 2008 May 9.


Mitragynine is a major indole alkaloid isolated from the Thai medicinal plant Mitragyna speciosa that has opium-like properties, although its chemical structure is quite different from that of morphine. We attempted to develop novel analgesics derived from mitragynine, and thus synthesized the ethylene glycol-bridged and C10-fluorinated derivative of mitragynine, MGM-9 [(E)-methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo[2,3-a]quinolizin-2-yl)-3-methoxyacrylate]. We hypothesized that a dual-acting mu- and kappa-opioid agonist could produce potent antinociceptive effects with fewer rewarding effects compared with mu agonists. In this study, MGM-9 exhibited high affinity for mu- and kappa-opioid receptors with Ki values of 7.3 and 18 nM, respectively. MGM-9 showed a potent opioid agonistic effect, and its effects were meditated by mu- and kappa-opioid receptor mechanisms in in vitro assays. Subcutaneous and oral administration of MGM-9 produced potent antinociceptive effects in mouse tail-flick, hot-plate, and writhing tests. When administered orally, the antinociceptive effect of MGM-9 was seven to 22 times more potent than that of morphine. The antinociceptive effects of MGM-9 were mediated by both mu- and kappa-opioid receptors. Subcutaneous administration of MGM-9 twice daily for 5 days led to antinociceptive tolerance. In the gastrointestinal transit study, MGM-9 inhibited gastrointestinal transit, but its effect was weaker than that of morphine at equi-antinociceptive doses. Furthermore, MGM-9 induced less hyperlocomotion and fewer rewarding effects than morphine. The rewarding effect of MGM-9 was blocked by a mu antagonist and enhanced by a kappa antagonist. Taken together, the results suggest that MGM-9 is a promising novel analgesic that has a stronger antinociceptive effect and weaker adverse effects than morphine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics, Opioid / pharmacology
  • Analysis of Variance
  • Animals
  • Behavior, Animal / drug effects
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Drug Administration Routes
  • Drug Tolerance
  • Gastrointestinal Transit / drug effects
  • Guinea Pigs
  • Male
  • Mice
  • Morphine / therapeutic use
  • Morphine Derivatives / therapeutic use
  • Pain / classification
  • Pain / drug therapy*
  • Pain / etiology
  • Pain Measurement / drug effects
  • Pain Threshold / drug effects*
  • Protein Binding / drug effects
  • Reaction Time / drug effects
  • Receptors, Opioid, kappa / agonists*
  • Receptors, Opioid, mu / agonists*
  • Reward*
  • Secologanin Tryptamine Alkaloids / chemistry
  • Secologanin Tryptamine Alkaloids / pharmacology*
  • Secologanin Tryptamine Alkaloids / therapeutic use
  • Time Factors


  • Analgesics, Opioid
  • Morphine Derivatives
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu
  • Secologanin Tryptamine Alkaloids
  • methyl 2-(3-ethyl-7a,12a-(epoxyethanoxy)-9-fluoro-1,2,3,4,6,7,12,12b-octahydro-8-methoxyindolo(2,3-a)quinolizin-2-yl)-3-methoxyacrylate
  • Morphine
  • mitragynine