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.
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.
Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Josai International University, 1 Gumyo, Togane, Chiba 283-8555, Japan. kenjiro@jiu.ac.jp
Kenjiro
K
Matsumoto
Hiromitsu
H
Takayama
Minoru
M
Narita
Atsushi
A
Nakamura
Masami
M
Suzuki
Tsutomu
T
Suzuki
Toshihiko
T
Murayama
Sumphan
S
Wongseripipatana
Kaori
K
Misawa
Mariko
M
Kitajima
Kimihito
K
Tashima
Syunji
S
Horie
D000701:Analgesics, Opioid / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes; D004361:Drug Tolerance; D005772:Gastrointestinal Transit / Q000187:drug effects; D006168:Guinea Pigs; D008297:Male; D051379:Mice; D009020:Morphine / Q000627:therapeutic use; D009022:Morphine Derivatives / Q000627:therapeutic use; D010146:Pain / Q000145:classification / Q000188:drug therapy* / Q000209:etiology; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects*; D011485:Protein Binding / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D017450:Receptors, Opioid, mu / Q000819:agonists*; D012201:Reward; D046948:Secologanin Tryptamine Alkaloids / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D013997:Time Factors
D000701:Analgesics, Opioid; D009022:Morphine Derivatives; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D046948:Secologanin Tryptamine Alkaloids; C533093: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; D009020:Morphine; C001801:mitragynine