Background:

Pitolisant HCl (BF2.649; Ciproxidine) is a potent, novel, and selective nonimidazole inverse agonist at the recombinant human H3 receptor with a Ki value of 0.16 nM[1]. The histamine H3 receptor, a histamine autoreceptor, functions as a heteroreceptor that regulates the release of other neurotransmitters, making it an attractive drug target for a number of indications including cognition [2].

In vitro: BF2.649 behaved as a competitive antagonist with a Ki value of 0.16 nM. BF2.649 functioned as an inverse agonist with an EC50 value of 1.5 nM and an intrinsic activity about 50% higher than that of ciproxifan. Pitolisant in vitro potency was approximately 6 times lower at the rodent receptor [1].

In vivo: Pitolisant HCl was an oral bioavailable agonist. In mice, after oral and i.v. administrations of pitolisant HCl, the ratio of plasma areas under the curve was 84%. BF2.649 enhanced tele-methylhistamine levels in mouse brain, an index of histaminergic neuron activity in a dose dependent manner with an ED50 value of 1.6 mg/kg p.o. The response persisted after repeated administrations for 17 days [1]. Treatment with 20-, 40-, or 60-mg doses of pitolisant showed a statistically significant suppressive effect (standardized photosensitive response [SPR] reduction as measured with paired t-tests) in 9/14 (64%) patients of whom 6/14 (43%) showed abolition of the response to intermittent photic stimulation (IPS) [3]. BF2.649 showed significant inhibitory activity in several mouse models of schizophrenia [4].

参考文献:
[1] Ligneau X, Perrin D, Landais L, Camelin JC, Calmels TP, et al, BF2. 649 [1-{3-[3-(4-Chlorophenyl)propoxy]propyl}piperidine, hydrochloride], a nonimidazole inverse agonist/antagonist at the human histamine H3 receptor: Preclinical pharmacology. J Pharmacol Exp Ther.2007 Jan;320(1):365-75.
[2] T A Esbenshade, K E Browman, R S Bitner, M Strakhova, M D Cowart, J D Brioni The histamine H3 receptor: an attractive target for the treatment of cognitive disorders.  Br J Pharmacol. 2008 Jul; 154(6): 1166–1181.
[3] Kasteleijn-Nolst Trenité D, Parain D, Genton P, Masnou P, Schwartz JC, Hirsch E.  Efficacy of the histamine 3 receptor (H3R) antagonist pitolisant (formerly known as tiprolisant; BF2.649) in epilepsy: dose-dependent effects in the human photosensitivity model. Epilepsy Behav.2013 Jul;28(1):66-70.
[4] Ligneau X, Landais L, Perrin D, Piriou J, Uguen M, Denis E, Robert P, Parmentier R, Anaclet C, Lin JS, Burban A, Arrang JM,Schwartz JC.  Brain histamine and schizophrenia: potential therapeutic applications of H3-receptor inverse agonists studied with BF2.649. Biochem Pharmacol. 2007 Apr 15;73(8):1215-24. a