AMG2850, a potent and selective TRPM8 antagonist, is not effective in rat models of inflammatory mechanical hypersensitivity and neuropathic tactile allodynia

Naunyn Schmiedebergs Arch Pharmacol. 2015 Apr;388(4):465-76. doi: 10.1007/s00210-015-1090-9. Epub 2015 Feb 10.

Abstract

TRPM8 has been implicated in pain and migraine based on dorsal root- and trigeminal ganglion-enriched expression, upregulation in preclinical models of pain, knockout mouse studies, and human genetics. Here, we evaluated the therapeutic potential in pain of AMG2850 ((R)-8-(4-(trifluoromethyl)phenyl)-N-((S)-1,1,1-trifluoropropan-2-yl)-5,6-dihydro-1,7-naphthyridine-7(8H)-carboxamide), a small molecule antagonist of TRPM8 by in vitro and in vivo characterization. AMG2850 is potent in vitro at rat TRPM8 (IC90 against icilin activation of 204 ± 28 nM), highly selective (>100-fold IC90 over TRPV1 and TRPA1 channels), and orally bioavailable (F po > 40 %). When tested in a skin-nerve preparation, AMG2850 blocked menthol-induced action potentials but not mechanical activation in C fibers. AMG2850 exhibited significant target coverage in vivo in a TRPM8-mediated icilin-induced wet-dog shake (WDS) model in rats (at 10 mg/kg p.o.). However, AMG2850 did not produce a significant therapeutic effect in rat models of inflammatory mechanical hypersensitivity or neuropathic tactile allodynia at doses up to 100 mg/kg. The lack of efficacy suggests that either TRPM8 does not play a role in mediating pain in these models or that a higher level of target coverage is required. The potential of TRPM8 antagonists as migraine therapeutics is yet to be determined.

MeSH terms

  • Action Potentials / drug effects
  • Animals
  • Behavior, Animal / drug effects
  • Blood Pressure / drug effects
  • Brain / metabolism
  • CHO Cells
  • Calcium / metabolism
  • Cold Temperature
  • Cricetinae
  • Cricetulus
  • Freund's Adjuvant
  • Humans
  • Hyperalgesia / drug therapy*
  • Male
  • Menthol / pharmacology
  • Mice, Inbred C57BL
  • Naphthyridines / pharmacology*
  • Naphthyridines / therapeutic use*
  • Pain / drug therapy
  • Pyrimidinones
  • Rats
  • Rats, Sprague-Dawley
  • Sciatic Nerve / injuries
  • TRPM Cation Channels / antagonists & inhibitors*

Substances

  • AMG2850
  • Naphthyridines
  • Pyrimidinones
  • TRPM Cation Channels
  • Trpm8 protein, rat
  • Menthol
  • Freund's Adjuvant
  • icilin
  • Calcium