Discovery of 1-[3-(4-bromo-2-methyl-2h-pyrazol-3-yl)-4-methoxyphenyl]-3-(2,4-difluorophenyl)urea (nelotanserin) and related 5-hydroxytryptamine2A inverse agonists for the treatment of insomnia

J Med Chem. 2010 Mar 11;53(5):1923-36. doi: 10.1021/jm9007328.


Insomnia affects a growing portion of the adult population in the U.S. Most current therapeutic approaches to insomnia primarily address sleep onset latency. Through the 5-hydroxytryptamine(2A) (5-HT(2A)) receptor, serotonin (5-HT) plays a role in the regulation of sleep architecture, and antagonists/inverse-agonists of 5-HT(2A) have been shown to enhance slow wave sleep (SWS). We describe here a series of 5-HT(2A) inverse-agonists that when dosed in rats, both consolidate the stages of NREM sleep, resulting in fewer awakenings, and increase a physiological measure of sleep intensity. These studies resulted in the discovery of 1-[3-(4-bromo-2-methyl-2H-pyrazol-3-yl)-4-methoxyphenyl]-3-(2,4-difluorophenyl)urea (Nelotanserin), a potent inverse-agonist of 5-HT(2A) that was advanced into clinical trials for the treatment of insomnia.

MeSH terms

  • Animals
  • Binding, Competitive
  • Inhibitory Concentration 50
  • Male
  • Phenylurea Compounds / chemical synthesis*
  • Phenylurea Compounds / pharmacokinetics
  • Phenylurea Compounds / pharmacology*
  • Pyrazoles / chemical synthesis*
  • Pyrazoles / pharmacokinetics
  • Pyrazoles / pharmacology*
  • Rats
  • Rats, Wistar
  • Receptor, Serotonin, 5-HT2A / metabolism
  • Receptor, Serotonin, 5-HT2C / metabolism
  • Serotonin / metabolism
  • Serotonin 5-HT2 Receptor Agonists*
  • Sleep / drug effects
  • Sleep Initiation and Maintenance Disorders / drug therapy*
  • Sleep Initiation and Maintenance Disorders / metabolism
  • Structure-Activity Relationship


  • Phenylurea Compounds
  • Pyrazoles
  • Receptor, Serotonin, 5-HT2A
  • Receptor, Serotonin, 5-HT2C
  • Serotonin 5-HT2 Receptor Agonists
  • Serotonin
  • nelotanserin