title: Analgesic effects of a substituted N-triazole oxindole (TROX-1), a state-dependent, voltage-gated calcium channel 2 blocker.
abstract: Voltage-gated calcium channel (Ca(v))2.2 (N-type calcium channels) are key components in nociceptive transmission pathways. Ziconotide, a state-independent peptide inhibitor of Ca(v)2.2 channels, is efficacious in treating refractory pain but exhibits a narrow therapeutic window and must be administered intrathecally. We have discovered an N-triazole oxindole, (3R)-5-(3-chloro-4-fluorophenyl)-3-methyl-3-(pyrimidin-5-ylmethyl)-1-(1H-1,2,4-triazol-3-yl)-1,3-dihydro-2H-indol-2-one (TROX-1), as a small-molecule, state-dependent blocker of Ca(v)2 channels, and we investigated the therapeutic advantages of this compound for analgesia. TROX-1 preferentially inhibited potassium-triggered calcium influx through recombinant Ca(v)2.2 channels under depolarized conditions (IC(50) = 0.27 microM) compared with hyperpolarized conditions (IC(50) > 20 microM). In rat dorsal root ganglion (DRG) neurons, TROX-1 inhibited omega-conotoxin GVIA-sensitive calcium currents (Ca(v)2.2 channel currents), with greater potency under depolarized conditions (IC(50) = 0.4 microM) than under hyperpolarized conditions (IC(50) = 2.6 microM), indicating state-dependent Ca(v)2.2 channel block of native as well as recombinant channels. TROX-1 fully blocked calcium influx mediated by a mixture of Ca(v)2 channels in calcium imaging experiments in rat DRG neurons, indicating additional block of all Ca(v)2 family channels. TROX-1 reversed inflammatory-induced hyperalgesia with maximal effects equivalent to nonsteroidal anti-inflammatory drugs, and it reversed nerve injury-induced allodynia to the same extent as pregabalin and duloxetine. In contrast, no significant reversal of hyperalgesia was observed in Ca(v)2.2 gene-deleted mice. Mild impairment of motor function in the Rotarod test and cardiovascular functions were observed at 20- to 40-fold higher plasma concentrations than required for analgesic activities. TROX-1 demonstrates that an orally available state-dependent Ca(v)2 channel blocker may achieve a therapeutic window suitable for the treatment of chronic pain.
authors.affiliation: Department of Pharmacology,Merck Research Laboratories, Rahway, New Jersey 07065, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Abbadie
authors.forename: Owen B
authors.initials: OB
authors.lastname: McManus
authors.forename: Shu-Yu
authors.initials: SY
authors.lastname: Sun
authors.forename: Randal M
authors.initials: RM
authors.lastname: Bugianesi
authors.forename: Ge
authors.initials: G
authors.lastname: Dai
authors.forename: Rodolfo J
authors.initials: RJ
authors.lastname: Haedo
authors.forename: James B
authors.initials: JB
authors.lastname: Herrington
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Kaczorowski
authors.forename: McHardy M
authors.initials: MM
authors.lastname: Smith
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Swensen
authors.forename: Vivien A
authors.initials: VA
authors.lastname: Warren
authors.forename: Brande
authors.initials: B
authors.lastname: Williams
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Arneric
authors.forename: Cyrus
authors.initials: C
authors.lastname: Eduljee
authors.forename: Terrance P
authors.initials: TP
authors.lastname: Snutch
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Tringham
authors.forename: Nina
authors.initials: N
authors.lastname: Jochnowitz
authors.forename: Annie
authors.initials: A
authors.lastname: Liang
authors.forename: D
authors.initials: D
authors.lastname: Euan MacIntyre
authors.forename: Erin
authors.initials: E
authors.lastname: McGowan
authors.forename: Shruti
authors.initials: S
authors.lastname: Mistry
authors.forename: Valerie V
authors.initials: VV
authors.lastname: White
authors.forename: Scott B
authors.initials: SB
authors.lastname: Hoyt
authors.forename: Clare
authors.initials: C
authors.lastname: London
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Lyons
authors.forename: Patricia B
authors.initials: PB
authors.lastname: Bunting
authors.forename: Sylvia
authors.initials: S
authors.lastname: Volksdorf
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Duffy
mesh_terms: D000700:Analgesics / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D017704:Baroreflex / Q000187:drug effects; D001682:Biological Availability; D002121:Calcium Channel Blockers / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000502:physiology*; D020908:Calcium Channels, R-Type / Q000502:physiology; D027682:Cation Transport Proteins / Q000502:physiology; D002460:Cell Line; D004285:Dogs; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology; D006930:Hyperalgesia / Q000188:drug therapy; D007024:Hypotension, Orthostatic / Q000139:chemically induced; D007211:Indoles / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000188:drug therapy / Q000209:etiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D014230:Triazoles / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: C551468:5-(3-chloro-4-fluorophenyl)-3-methyl-3-(pyrimidin-5-ylmethyl)-1-(1H-1,2,4-triazol-3-yl)-1,3-dihydro-2H-indol-2-one; D000700:Analgesics; C500963:Cacna1b protein, mouse; C503279:Cacna1b protein, rat; C498917:Cacna1e protein, rat; D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D020908:Calcium Channels, R-Type; D027682:Cation Transport Proteins; D007211:Indoles; D014230:Triazoles