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
Protocol
Kinase experiment: | [35S]GTPγS binding assays are performed. CHO-K1 cells stably expressing the human H3 receptor (~400 fmol/mg protein) are homogenized in ice-cold buffer (50 mM Tris/HCl, pH 7.4). Homogenates are centrifuged twice (20,000g for 10 min at 4°C), and the final pellet is resuspended in 50 volumes of buffer. Membranes (550 μg of protein) are pretreated with adenosine deaminase (1 U/mL) and incubated for 60 min at 25°C with 0.1 nM [35S]GTPγS and the drugs to be tested in a final volume of 1 mL of assay buffer (50 mM Tris/HCl, 50 mM NaCl, 5 mM MgCl2, 10 μM GDP, and 0.02% bovine serum albumin, pH 7.4). The nonspecific binding is determined using 10 μM nonradioactive GTPγS. Incubations are stopped by rapid filtration under vacuum through GF/B glass fiber filters. After washing with ice-cold water, the radioactivity trapped on filters is counted by liquid scintillation spectrometry. A similar assay is used to assess competitive antagonism. In brief, membranes (10 μg of protein) of HEK-293 cells stably expressing the human H3 receptor (~600 fmol/mg protein) are preincubated in presence of Pitolisant in the buffer (50 mM Tris/HCl, pH 7.4, 10 mM MgCl2, 100 mM NaCl, and 10 μM GDP) in a 96-well microplate under gentle agitation at room temperature (19-20°C) for 30 min before the addition of 0.1 nM [35S]GTPγS (final volume 200 μL). The nonspecific binding is determined using a 10 μM concentration of nonradioactive GTPγS. After 30 min, incubations performed in triplicate are stopped by rapid filtration under vacuum on a Multiscreen MAFCOB50 microplate. Radioactivity trapped on filters is counted by liquid scintillation spectrometry[1]. |
Animal experiment: | Mice[2] Adult female Albino Swiss mice weighing 20-22 g are used in the study. LY170053 or Pitolisant are suspended in 1 % Tween 80. The compounds or vehicle are administered intraperitoneally (i.p.) 30 min prior to the acute experiment. In the Pitolisant+LY170053 group, Pitolisant is administered 15 min before LY170053. Subchronic treatment is done at about 9:00 am (0.2 mL Tween to control group, Pitolisant-10 mg/kg b.w. to Pitolisant group, LY170053-2 mg/kg b.w. to LY170053 group, Pitolisant-10 mg/kg b.w. and LY170053 after 15 min-2 mg/kg b.w. to Pitolisant+LY170053 group) and at about 1:00 pm (LY170053 group and Pitolisant+LY170053 group).Rats[3] Male Wistar rats (220-300 g) receive vehicle (methylcellulose 1%, p.o.), and Pitolisant (10 mg/kg, p.o.). Ninety minutes later, they are killed by decapitation and nucleus accumbens are dissected out, weighed, frozen in liquid nitrogen and stored at -80°C. Tissues are homogenized in 1 mL of a 0.4 N perchloric acid/2.7 mM EDTA solution. After centrifugation (8000 rpm, 20 min, 4°C), supernatants are analysed by HPLC coupled to electrochemical detection. |
参考文献: [1]. Ligneau X, 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]. Dudek M, et al. H3 histamine receptor antagonist pitolisant reverses some subchronic disturbances induced by LY170053 in mice. Metab Brain Dis. 2016 Oct;31(5):1023-9.
[3]. Uguen M, et al. Preclinical evaluation of the abuse potential of Pitolisant, a histamine H receptor inverse agonist/antagonist compared with CRL 40476. Br J Pharmacol. 2013 Jun;169(3):632-44. |
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