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].

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].

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Administration of Pitolisant (10 mg/kg, i.p.) alone for 15 days did not significantly affect immobility time in the forced swim test (FST) in mice, indicating no intrinsic antidepressant-like or depressant-like effect.
Pitolisant (10 mg/kg, i.p.) alone did not affect locomotor activity in mice after single or 15-day administration.
When co-administered with olanzapine (2 mg/kg, i.p., twice daily) for 15 days, Pitolisant reversed the olanzapine-induced increase in immobility time in the FST, bringing it back to control levels.
Pitolisant co-administration also normalized the reduced locomotor activity caused by subchronic olanzapine treatment.
In spontaneous activity monitoring over 20 hours, Pitolisant alone did not alter the normal day/night activity pattern compared to the control group.
Co-administration of Pitolisant with olanzapine partially compensated for the olanzapine-induced reduction in spontaneous activity, particularly during the dark (active) phase.
Pitolisant (10 mg/kg, i.p., for 14 days) prevented the significant increase in serum triglyceride levels induced by subchronic olanzapine administration, bringing triglyceride levels back to control values.

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.

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Animals: Adult female Albino Swiss mice (20–22 g) were used.
Drug Formulation: Pitolisant was suspended in 1% Tween 80.
Dose: 10 mg/kg body weight.
Route: Intraperitoneal (i.p.) injection.
Treatment Schedule: In studies investigating the reversal of olanzapine effects, Pitolisant was administered 15 minutes prior to the first daily olanzapine injection (2 mg/kg, i.p.). This combined treatment was given twice daily (approximately 9:00 AM and 1:00 PM) for 14-15 consecutive days. Pitolisant was administered only with the morning olanzapine dose.
Control groups received the vehicle (1% Tween 80) or Pitolisant alone according to the same schedule.
Behavioral Tests: Forced swim test and locomotor activity were assessed on day 1 (acute) and day 15 (subchronic). Spontaneous activity was monitored continuously from day 14, 1:00 PM to day 15, 9:00 AM using an RFID system (TraffiCage).
Biochemical Analysis: On day 16, after 15 drug administration cycles, mice were euthanized, blood was collected, and serum triglyceride levels were measured using standard enzymatic spectrophotometric kits.

Absorption, Distribution and Excretion
Pitocris is rapidly and well absorbed after oral administration, with an absorption rate of up to 90%. In healthy subjects, after oral administration of 20 mg pitucris, the peak plasma concentration (Cmax) is approximately 30 ng/mL. After once-daily oral administration of 35.6 mg pitucris, the mean steady-state peak plasma concentration (Cmax) and area under the curve (AUC) are 73 ng/mL and 812 ng·hr/mL, respectively. The time to peak concentration (Tmax) is typically reached approximately 3 hours after administration. After repeated dosing, steady-state plasma concentrations are typically reached after 5–6 days, but significant inter-individual variability has been reported. The absolute bioavailability of pitucris has not been determined. After hepatic metabolism, approximately 63% of the total elimination is excreted in the urine via the kidneys as the inactive unconjugated metabolite BP2.951 and the glycine-conjugated metabolite. Approximately 25% of the total administered dose is excreted as metabolites via exhalation, and a small amount (<3%) of the drug is recovered in feces. The apparent volume of distribution (V/F) after single or multiple oral administrations of 1 to 240 mg pittorisa in healthy adult males ranges from 1100 to 2825 L. Pittorisa is considered to be uniformly distributed in erythrocytes and plasma. In rats and monkeys, the steady-state apparent volume of distribution after intravenous administration of pittorisa is approximately 10 times the total body fluid volume. Pittorisa crosses the blood-brain barrier and placenta and is found in rat milk. The apparent oral clearance (CL/F) after a single oral administration of 35.6 mg pittorisa is 43.9 L/hr. Clearance is expected to decrease with age. Metabolites/Metabolites: Pittorisa is primarily metabolized in the liver via CYP2D6, with a small amount metabolized via CYP3A4. The main unconjugated metabolites are BP2.941 (piperidine N-oxide) and BP2.951 (5-aminovaleric acid). These metabolites can further conjugate with glycine or glucuronic acid and undergo minor oxidation. Most metabolites of pittorisone do not retain significant pharmacological activity. In addition, several conjugated metabolites have been identified; the main conjugated inactive metabolites are the glycine conjugate of the O-dealkylated unsaturated pittorisone metabolite and the glucuronide of the monohydroxy unsaturated pittorisone metabolite. Because pittorisone is extensively metabolized in the liver, systemic exposure may increase in patients with impaired hepatic function, thereby increasing the incidence of adverse drug reactions. Dosage adjustment of pittorisone is recommended for patients with moderate hepatic impairment.

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Biological Half-Life
The plasma half-life of pittorisone is 10–12 hours. After a single dose of 35.6 mg, the median half-life of pittorisone is approximately 20 hours. The study indicated that, compared to taking either drug alone, concurrent administration of pitotrigine and olanzapine in healthy volunteers did not significantly alter the plasma concentrations of either drug.

Hepatotoxicity
In placebo-controlled trials of pitolisan in patients with narcolepsy, a small number of patients experienced mild elevations in serum transaminases during treatment, but the incidence of these elevations was similar to that in the placebo group. No clinically significant liver injury or elevated serum transaminases with jaundice was observed with pitolisan in pre-registration trials. Since its approval in Europe in 2017 and in the United States in 2020, no clinically significant liver injury caused by pitolisan has been reported in the literature. Probability score: E (Unlikely a cause of acute liver injury with jaundice). Pregnancy and Lactation Effects ◉ Overview of Use During Lactation There is currently no information regarding the clinical use of pitolisan during lactation. However, the levels in breast milk appear to be very low, and no adverse effects are expected on breastfed infants. If a mother needs to use pitolisan, this is not a reason to discontinue breastfeeding. Infants should be closely monitored during breastfeeding while using pitolisan until more safety data are available.
◉ Effects on breastfed infants
No published information found as of the revision date.
◉ Effects on lactation and breast milk
No published information found as of the revision date.

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Protein binding
Pittorisamine's serum protein binding rate is approximately 91% to 96%. Pitorisamine primarily binds to serum albumin and α-1 glycoprotein.

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According to the cited literature, at the dose used (10 mg/kg, intraperitoneal injection), pitorisamine has been reported to be active, but no adverse reactions were observed. This study itself did not observe any significant toxicity or behavioral or triglyceride level changes in mice treated with pittorisamine alone.

[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
Pitolisan promotes wakefulness in patients with narcolepsy by enhancing histaminergic signaling in the central nervous system. Its binding to H1, H2, or H4 receptors is not significant. In patients with narcolepsy, with or without cataplexy, pitolisan treatment was associated with improvements in wakefulness levels and duration, as well as daytime alertness, assessed by objective measures of sustained wakefulness (e.g., Maintenance of Wakefulness Test (MWT) and Epworth Sleepiness Scale (ESS) scores) and attention (e.g., Sustained Attention Response Task (SART)). Pitolisan also improved the frequency and severity of narcolepsy-related cataplexy. Pitolisan acts as an hERG channel blocker. In two QT interval studies, supertherapeutic doses of pitolisan (3–6 times the therapeutic dose, i.e., 108 mg to 216 mg) resulted in a mild to moderate prolongation of the QTc interval (10–13 ms).
Pittorisone is a selective inverse agonist/antagonist of histamine H₃ receptors (H₃Rs). H₃ receptors are presynaptic autoreceptors that inhibit histamine synthesis/release; they are also heteroreceptors that inhibit the release of other neurotransmitters such as serotonin, norepinephrine, and acetylcholine. The mechanism proposed in this study is that pittorisone increases histaminergic (and possibly other neurotransmitter) tone in the brain by blocking H₃Rs, which may counteract the sedation, depressive-like behavior, and metabolic disturbances caused by…
. Olanzapine works by blocking H₁ receptors. This study suggests that pittorisone holds promise as an adjunct therapy to counteract certain behavioral (sedation, depressive-like symptoms) and metabolic (elevated triglycerides) side effects that occur during the initial treatment of atypical antipsychotics (olanzapine).

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.)