1.Antagonism of supraspinal histamine H3 receptors modulates spinal neuronal activity in neuropathic rats.
McGaraughty S1, Chu KL, Cowart MD, Brioni JD. J Pharmacol Exp Ther. 2012 Oct;343(1):13-20. doi: 10.1124/jpet.112.194761. Epub 2012 Jun 22.
There is growing evidence supporting a role for histamine H(3) receptors in the modulation of pathological pain. To further our understanding of this modulation, we examined the effects of a selective H(3) receptor antagonist, 6-((3-cyclobutyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-yl)oxy)-N-methyl-3-pyridinecarboxamide (GSK189254), on spinal neuronal activity in neuropathic (L5 and L6 ligations) and sham rats. Systemic administration of GSK189254 (0.03-1 mg/kg i.v.) dose-dependently decreased both evoked (10-g von Frey hair for 15 s) and spontaneous firing of wide dynamic range (WDR) neurons in neuropathic, but not sham-operated, animals. The effects on spontaneous firing suggest that H(3) receptors may have a role in central sensitization and/or modulating non-evoked pain. Transection of the spinal cord (T9-T10) completely eliminated the effects (both evoked and spontaneous) of systemic GSK189254 (1 mg/kg, i.v.) on WDR neuronal firing in neuropathic rats, indicating that the descending modulatory system has an important role in the H(3)-related dampening of spinal neuronal activity.
2.Unexpectedly high affinity of a novel histamine H(3) receptor antagonist, GSK239512, in vivo in human brain, determined using PET.
Ashworth S1, Berges A, Rabiner EA, Wilson AA, Comley RA, Lai RY, Boardley R, Searle G, Gunn RN, Laruelle M, Cunningham VJ. Br J Pharmacol. 2014 Mar;171(5):1241-9. doi: 10.1111/bph.12505.
BACKGROUND AND PURPOSE: This study aimed to investigate the relationship between the plasma concentration (PK) of the novel histamine H3 receptor antagonist, GSK239512, and the brain occupancy of H(3) receptors (RO) in healthy human volunteers.
3.A new facile synthetic route to [11C]GSK189254, a selective PET radioligand for imaging of CNS histamine H3 receptor.
Wang M1, Gao M, Steele BL, Glick-Wilson BE, Brown-Proctor C, Shekhar A, Hutchins GD, Zheng QH. Bioorg Med Chem Lett. 2012 Jul 15;22(14):4713-8. doi: 10.1016/j.bmcl.2012.05.076. Epub 2012 May 26.
GSK189254 and its corresponding precursor GSK185071B were synthesized from 3-methoxyphenylacetic acid with 6-chloropyridine-3-carbolic acid or 6-chloronicotinamide in 8 and 7 steps with either 6% or 7% and either 14% or 16% yield, respectively. [(11)C]GSK189254 was prepared from GSK185071B with [(11)C]CH(3)OTf through N-[(11)C]methylation and isolated by HPLC combined with solid-phase extraction (SPE) in 50-60% radiochemical yield based on [(11)C]CO(2) and decay corrected to end of bombardment (EOB), with 370-740 GBq/μmol specific activity at EOB.
4.Identification of clinical candidates from the benzazepine class of histamine H3 receptor antagonists.
Wilson DM1, Apps J, Bailey N, Bamford MJ, Beresford IJ, Brackenborough K, Briggs MA, Brough S, Calver AR, Crook B, Davis RK, Davis RP, Davis S, Dean DK, Harris L, Heslop T, Holland V, Jeffrey P, Panchal TA, Parr CA, Quashie N, Schogger J, Sehmi SS, Stean Bioorg Med Chem Lett. 2013 Dec 15;23(24):6890-6. doi: 10.1016/j.bmcl.2013.09.090. Epub 2013 Oct 5.
This Letter describes the discovery of GSK189254 and GSK239512 that were progressed as clinical candidates to explore the potential of H3 receptor antagonists as novel therapies for the treatment of Alzheimer's disease and other dementias. By carefully controlling the physicochemical properties of the benzazepine series and through the implementation of an aggressive and innovative screening strategy that employed high throughput in vivo assays to efficiently triage compounds, the medicinal chemistry effort was able to rapidly progress the benzazepine class of H3 antagonists through to the identification of clinical candidates with robust in vivo efficacy and excellent developability properties.