H3 receptor ( Ki = 0.16 nM ); H3 receptor ( EC50 = 1.5 nM )

Pitolisant (BF2.649) exhibits competitive antagonistic (K_i = 0.16 nM) and inverse agonistic (EC50 = 1.5 nM) behaviors upon stimulation of guanosine 5′-O-(3-[³⁵S]thio)triphosphate binding to this receptor. Its intrinsic activity is approximately 50% greater than that of ciproxifan. Pitolisant has an IC50 value of 26.4±4.5 nM, which is sufficient to remove [¹²⁵I]iodoproxyfan binding from mouse brain cortical membranes. TaK_ing into account the K_d value of the radioligand (161±9 pM), the deduced K_i value for Pitolisant is 14±1 nM. Pitolisant, with an IC50 value of 4.2±0.2 nM, displaces [¹²⁵I]iodoproxyfan binding from the membranes of rat glioma C6 cells that express the human H₃ receptor stably. Pitolisant's calculated K_i value is 2.7±0.5 nM when the radioligand's K_d value of 50±4 pM is taken into account. With a Hill coefficient near unity and an IC50 value of 330±68 nM, pitolisant gradually reverses this response, resulting in a K_i value of 17±4 nM. Pitolisant reduces basal-specific [³⁵S]GTPγS binding to membranes in a dose-dependent manner; the maximal effect is equivalent to 75±1% of basal-specific binding, with an EC50 value of 1.5±0.1 nM[1].

The single dose of Olanzapine (2 mg/kg b.w.) given 30 minutes prior to a single dose of Pitolisantat (10 mg/kg) also has a significant impact on the immobility time in the FST. When the previously mentioned drug sequence is given to mice again, the length of immobility is statistically significantly longer than when it was measured in the FST control group. Furthermore, it lowered locomotor activity. The results of subchronic treatment, on the other hand, indicate that the administration of Pitolisant followed by that of Olanzapine equalized the locomotor activity in mice. This is in contrast to the level of motility in the control group, which receives only Pitolisant. Pitolisant was administered at a dose of 10 mg/kg b.w. for fifteen minutes, and Olanzapine at a dose of 2 mg/kg b.w. for four hours. More significantly, this combination of medications lowers immobility time in the forced swim test in mice to a level attained in the control group [one-way ANOVA; F_(3,20)=4.226,P=0.0181].[2] Pitolisant (10 mg/kg)-administered rats remained on the paired texture for 502±94 s during the conditioning phase; this value was not statistically different from controls, suggesting that Pitolisant did not support place preference[3].

There are assays for [³⁵S]GTPγS binding. Homogenized in an ice-cold buffer (50 mM Tris/HCl, pH 7.4), CHO-K1 cells that stably express the human H₃ receptor (~400 fmol/mg protein) are used. The final pellet is resuspended in 50 volumes of buffer after homogenates are centrifuged twice (20,000g for 10 min at 4°C). Membranes containing 550 μg of protein are pretreated with 1 U/mL of adenosine deaminase and then incubated at 25°C for 60 minutes with 0.1 nM [³⁵S] GTPηS and the medications to be examined in a final volume of 1 mL of assay buffer, which contains 10 μM GDP, 50 mM Tris/HCl, 50 mM NaCl, 5 mM MgCl2, and 0.02% bovine serum albumin at pH 7.4. Using 10 μM nonradioactive GTPγS, the nonspecific binding is ascertained. Filtration through GF/B glass fiber filters quickly and under vacuum ends incubations. Following an ice-cold water wash, liquid scintillation spectrometry is used to quantify the radioactivity trapped on the filters. The measure of competitive antagonism is the same as well. Essentially, membranes (10 μg of protein) from HEK-293 cells that stably express the human H₃ receptor (~600 fmol/mg protein) are preincubated with 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. This is done with mild stirring at room temperature (19–20°C) for 30 minutes before 0.1 nM [³⁵S]GTPηS (final volume 200 μL) is added. Nonradioactive GTPγS at a concentration of 10 μM is used to measure the nonspecific binding. On a Multiscreen MAFCOB50 microplate, incubations carried out in triplicate are terminated after 30 minutes by quick filtration under vacuum. Liquid scintillation spectrometry counts radioactivity that has become trapped on filters[1].

Mice: The study makes use of adult female Albino Swiss mice weighing 20–22 g. A 1% Tween 80 suspension contains either olanzapine or pitolisant. An acute experiment begins 30 minutes before the compounds or vehicle are injected intraperitoneally (i.p.). Pitolisant and Olanzapine are given to the group that receives them 15 minutes apart. 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, Olanzapine-2 mg/kg b.w. to Olanzapine group, Pitolisant-10 mg/kg b.w. and Olanzapine after 15 min-2 mg/kg b.w. to Pitolisant+Olanzapine group) and at about 1:00 pm (Olanzapine group and Pitolisant+Olanzapine group). Rats: Male Wistar rats (220-300 g) receive vehicle (methylcellulose 1%, p.o.), Pitolisant (10 mg/kg, p.o.) or D-amphetamine (2.5 mg/kg, i.p. in saline). The nucleus accumbens is removed, weighed, frozen in liquid nitrogen, and kept at -80°C after they are beheaded ninety minutes later. A 0.4 N perchloric acid/2.7 mM EDTA solution in 1 mL is used to homogenize the tissues. HPLC coupled with electrochemical detection is used to analyze the supernatants following centrifugation (8000 rpm, 20 min, 4°C). Dihydroxyphenyl acetic acid (DOPAC), homovanillic acid (HVA), and dopamine (DA) tissue concentrations are measured, and the corresponding ratios (DOPAC/DA, HVA/DA) are computed.

Absorption, Distribution and Excretion
Pitolisant is rapidly and well absorbed following oral administration, resulting in the drug being 90% absorbed. In healthy individuals receiving an oral dose of 20 mg, the Cmax was approximately 30 ng/mL. Following oral administration of pitolisant 35.6 mg once daily, the mean steady state Cmax and AUC were 73 ng/mL and 812 ngxhr/mL, respectively. The Tmax was typically reached approximately 3 hours following administration. Following repeated dosing, the steady-state plasma concentration is achieved after 5-6 days of administration but the inter-individual variability in the time to reach steady-state is reported to be high. The absolute bioavailability of pitolisant has not been determined.
Following hepatic metabolism, about 63% of total elimination occurs via renal excretion into the urine as an inactive non-conjugated metabolite BP2.951 and a glycine conjugated metabolite. About 25% of the total dose administered is excreted through expired air as metabolites, and a small fraction (<3%) of drug can be recovered in faeces.
Following single and multiple oral dosing of pitolisant to healthy male adults at doses between 1 and 240 mg, the apparent volume of distribution (V/F) ranges from 1100 to 2825 L. Pitolisant is thought to be equally distributed between red blood cells and plasma. Following intravenous administration of pitolisant in rats and monkeys, the apparent Vd at steady-state was approximately 10-fold greater than total body water. Pitolisant crosses the blood-brain barrier and placenta, and was found in milk in rats.
The apparent oral clearance (CL/F) of pitolisant was 43.9 L/hr following a single dose of 35.6 mg. The clearance rate is expected to be lower with increasing age.

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Metabolism / Metabolites
Pitolisant is primarily metabolized by CYP2D6 and to a lesser extent by CYP3A4 in the liver. The major non-conjugated metabolites are BP2.941 (piperidine N-oxide) and BP2.951 (5-aminovaleric acid). Metabolites can further undergo conjugation with glycine or glucuronic acid, and oxidation to a minimal extent. Most metabolites of pitolisant do not retain considerable pharmacological activities. Several conjugated metabolites were also identified; the major conjugated inactive metabolite was a glycine conjugate of the acid metabolite of O-dealkylated desaturated pitolisant and a glucuronide of a ketone metabolite of monohydroxy desaturated pitolisant. Due to its extensive metabolism in the liver, the systemic exposure of pitolisant thus adverse events of the drug may be elevated in case of compromised liver function. The dosage adjustments for pitolisant is advised in patients with moderate hepatic impairment.

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Biological Half-Life
Pitolisant has a plasma half-life of 10-12 hours. After administration of a single dose of 35.6 mg, the median half-life of pitolisant was approximately 20 hours.

Hepatotoxicity
In placebo-controlled trials of pitolisant in patients with narcolepsy, minor serum aminotransferase elevations occurred in a small proportion of patients during therapy, but rates of enzyme elevations were similar to those in placebo recipients. In preregistration trials, there were no instances of clinically apparent liver injury or serum aminotransferase elevations with jaundice attributable to pitolisant. Since its approval in Europe in 2017 and the United States in 2020, there have been no publications describing clinically apparent liver injury due to pitolisant.
Likelihood score: E (unlikely cause of acute liver injury with jaundice).

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
No information is available on the clinical use of pitolisant during breastfeeding. However, amounts in breastmilk appear to be low and would not be expected to cause any adverse effects in breastfed infants. If pitolisant is required by the mother, it is not a reason to discontinue breastfeeding. Until more safety data are available, pitolisant should be used with careful infant monitoring during breastfeeding.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

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Protein Binding
The serum protein binding of pitolisant is approximately 91% to 96%. Pitolisant is mainly bound to serum albumin and alpha-1 glycoprotein.

[1]. 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]. H3 histamine receptor antagonist pitolisant reverses some subchronic disturbances induced by olanzapine in mice. Metab Brain Dis. 2016 Oct;31(5):1023-9.

[3]. Preclinical evaluation of the abuse potential of Pitolisant, a histamine H? receptor inverse agonist/antagonist compared with Modafinil. Br J Pharmacol. 2013 Jun;169(3):632-44.

Pharmacodynamics
Pitolisant promotes wakefulness in narcolepsy by enhancing histaminergic signalling in the central nervous system. It does not significantly bind to H1, H2, or H4 receptors. In patients with narcolepsy in presence or absence of cataplexy, treatment of pitolisant was associated with an improvement in the level and duration of wakefulness and daytime alertness assessed by objective measures of ability to sustain wakefulness (e.g. Maintenance of Wakefulness Test (MWT) and Epworth Sleepiness Scale (ESS) Scores) and attention (e.g. Sustained Attention to Response Task (SART)). Pitolisant also improved the frequency and severity of narcolepsy-associated cataplexy. Pitolisant acts as a blocker at hERG channels. In two QT studies, supra-therapeutic doses of pitolisant (3-6-times the therapeutic dose, that is 108 mg to 216 mg) produced mild to moderate prolongation of QTc interval (10-13 ms).

C17H26CLNO

295.8474

295.17

C, 69.02; H, 8.86; Cl, 11.98; N, 4.73; O, 5.41

362665-56-3

Pitolisant hydrochloride; 903576-44-3; Pitolisant oxalate; 362665-57-4

9948102

Colorless to light yellow liquid

4.103

0

2

8

20

235

0

ClC1C([H])=C([H])C(=C([H])C=1[H])C([H])([H])C([H])([H])C([H])([H])OC([H])([H])C([H])([H])C([H])([H])N1C([H])([H])C([H])([H])C([H])([H])C([H])([H])C1([H])[H]

NNACHAUCXXVJSP-UHFFFAOYSA-N

InChI=1S/C17H26ClNO/c18-17-9-7-16(8-10-17)6-4-14-20-15-5-13-19-11-2-1-3-12-19/h7-10H,1-6,11-15H2

1-[3-[3-(4-chlorophenyl)propoxy]propyl]piperidine

FUB-649; BF2649; FUB649; BF-2649; FUB 649; BF2.649; B F2649; Pitolisant; Tiprolisant; Pitolisant HCl; Pitolisant hydrochloride

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~66 mg/mL (~198.6 mM)
Water: ~66 mg/mL
Ethanol: ~66 mg/mL

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.45 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.45 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (8.45 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)