WO2018033525A1

WO2018033525A1 - Agonists or partial agonists of the histamine site of the nmda receptor for use in the treatment of central nervous system diseases

Info

Publication number: WO2018033525A1
Application number: PCT/EP2017/070637
Authority: WO
Inventors: Vincent ARMAND; Aude BURBAN-PREVOST; Raphaël FAUCARD; Jean-Michel Arrang
Original assignee: INSERM (Institut National de la Santé et de la Recherche Médicale); Universite Paris-Sud; Universite Paris Descartes
Priority date: 2016-08-16
Filing date: 2017-08-14
Publication date: 2018-02-22

Abstract

This invention relates to compounds that are agonists or partial agonists of the histamine site of the NMDA receptor, the method of preparation thereof and applications thereof.

Description

AGONISTS OR PARTIAL AGONISTS OF THE HISTAMINE SITE OF THE NMDA RECEPTOR FOR USE IN THE TREATMENT OF CENTRAL NERVOUS SYSTEM

DISEASES INTRODUCTION

The present invention relates to agonists or partial agonists of the histamine site of the NMDA receptor for use in the treatment of central nervous system diseases.

BACKGROUND OF THE INVENTION

Psychotic troubles are chronic and debilitating diseases with significant morbidity and mortality that often requires antipsychotic pharmacotherapy for life. Current therapy consists of neuroleptics with major anti-dopaminergic and anti-serotoninergic activity but may also act on other receptors such as histamine and noradrenaline receptors. In case of schizophrenia, these neuroleptics agents generally block dopamine receptors. Such agents are divided in two classes, i.e. typical antipsychotics and atypical antipsychotics.

For example, phenothiazines are typical antipsychotics and clozapine, olanzapine and risperidone are atypical antipsychotics.

It is well known from the prior art that typical neuroleptic agents induce extrapyramidal symptoms, which include rigidity, tremor, bradykinesia (slow movement) and bradyphrenia (slow thought), as well as tardive dyskinesia, acute dystonic reactions and akathisia. Furthermore, atypical neuroleptic agents induce both extrapyramidal symptoms and other side effects such as increase of body weight, mood disturbance, sexual dysfunction, sedation, orthostatic hypotension, hypersalivation, lowered seizure threshold and, in particular, agranulocytosis. Recent discoveries brought to light the link between schizophrenia and bipolar disorders with disturbance in GABA and glutamate transmission in the brain. Studies suggest that schizophrenia would be associated with ionotropic N-methyl-D-aspartate (NMDA) receptor dysfunction. Indeed, according to experimental researches, it has been found that NMDA receptor blockers such as phencyclidine (PCP) and MK-801 induce psychoses similar to that associated with schizophrenia. Since hypofunction of NMDA system is considered to have an important role in schizophrenia and schizophreniform psychosis (especially negative symptoms and cognitive dysfunction caused by phencyclidine are similar to schizophrenia), it is suggested that the NMDA inhibition would lead to diminished GABAergic tone and thus induce disinhibition of glutamatergic AMPA receptor resulting in excitotoxic neuronal damage and psychosis. NMDA receptor modulators, such as antagonists, agonists and partial agonists, have thus been the subject of several successive researches both for the treatment of psychotic diseases and for the treatment of central nervous diseases. For example, the NMDA receptor modulator memantine was developed for the treatment of Alzheimer's disease. The partial agonist agent D-cycloserine was revealed as having some antidepressant and anxiolytic activity in animal models and to improve mood, insomnia and appetite. Furthermore, agents targeting the NMDA receptor appeared to be involved in different stages of clinical development for the treatment of anxiety, depression, cognitive and motor disorders. NMDA receptor modulators have also been investigated as therapeutic agents for the treatment of neurological disorders such as stroke, epilepsy, pain and Parkinson's disease.

However, many of these compounds cause side effects and in particular adverse behavioral (psychotomimetic) effects and can produce neurotoxicity characterized by neuronal vacuolization, induction of heat-shock protein, neuronal/axonal degeneration and regional brain cell death.

NMDA receptors are composed of NR1, NR2 (A, B, C and D), and NR3 (A and B) subunits determining the functional properties of native NMDA receptors. Expression of the NR1 subunit alone does not produce a functional receptor and requires the co-expression of one or more NR2 subunits to form functional channels. To be activated, the NMDA receptor requires both the binding of glutamate and of glycine as a co-agonist. The glutamate binding site is found on the NR2 subunits whereas the glycine binding site is found on the NR1 and NR3 subunits.

Recent discoveries also identified a histamine site on NMDA receptors. Histamine has numerous functions in the brain and in particular modulates responses of the NMDA receptors of hippocampal neurons (Bekkers J. Science 1993). Williams demonstrated that histamine could directly act at a novel recognition site on the NMDA receptor and had a selective effect on responses mediated by NR1/NR2B receptors (Williams Mol Pharmacol 1994). Williams further showed that the effect of histamine was not blocked by classical histamine receptor antagonists. The effect of histamine on the NMDA receptor is mimicked by tele-methylhistamine and histamine does not bind to the polyamine site, but to a distinct entity, the so-called histamine site of the NMDA receptor (Burban A. J Pharmacol Exp Ther. 2010).

The problem solved by this invention is to provide compounds that can interfere with the NMDA receptor and in particular with the histamine site of the NMDA receptor. The inventors have surprisingly found that such compounds are able to treat NMDA receptor disorders and associated diseases, with a maximal response effect.

SUMMARY OF THE INVENTION

The present invention relates to a compound of general formula (I):

wherein:

n and m each independently represents an integer from 1 to 6, preferably from 2 to 4;

Ri represents -NH- or -NR_IA-;

wherein R_IA represents a phenyl-(Ci-C₄)alkyl group, (C3-C6)cycloalkyl group, -C(0)-0-R_1B or -COR_1B

wherein R_IB represents:

-a (C]-C₄)alkyl group, preferably an i-propyl or t-butyl group, or,

- a phenyl-(Ci-C₄)alkyl group;

A represents a group of formula (II) or (III):

or

(Π) (HI) wherein denotes a single or double bond;

R₂ represents a nitrogen atom or -NHR_2A;

wherein R_2A represents -C(0)H or -C(0)NHR_2B;

wherein R_2B represents a phenyl-(C]-C₄)alkyl group;

R3 represents =0 or -OH;

R4 represents an hydrogen atom, =0 or an amino group; and

R5 represents an hydrogen atom, a (C]-C₄)alkyl group, preferably a methyl group, or -C(0)H; or pharmaceutically acceptable salts or tautomeric forms thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One subject of the present invention is a compound of general formula (I):

wherein:

Ri represents -NH- or -NR]_A-;

wherein R_]A represents a phenyHCi-G alkyl group, (C3-C₆)cycloalkyl group, -C(0)-0-R_1B or -COR_1B

wherein R_IB represents:

-a (C]-C₄)alkyl group, preferably an i-propyl or t-butyl group, or,

- a phenyl-(Ci-C₄)alkyl group;

A represents a group of formula (II) or (III):

or ;

(II) (III) wherein denotes a single or double bond;

R₂ represents a nitrogen atom or -NHR_2A;

wherein R_2A represents -C(0)H or -C(0)NHR_2B;

wherein R_2B represents a phenyl-(Ci-C₄)alkyl group;

R3 represents =0 or -OH;

R₄ represents an hydrogen atom, =0 or an amino group; and

R5 represents an hydrogen atom, a (Ci-C₄)alkyl group, preferably a methyl group, or -C(0)H;

or pharmaceutically acceptable salts or tautomeric forms thereof. The expression "C₁-C₆ alkyl group" represents a linear or branched alkyl group having 1 to 6 carbons atoms. Examples of such alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl.

Preferred alkyl groups are C₁-C₄ alkyl groups. The expression "C₁-C₄ alkyl group" represents an alkyl having 1 to 4 carbons atoms. Examples of such C₁-C₄ alkyl groups include methyl, ethyl, butyl, propyl, t-butyl, i-butyl and i-propyl. The expression "C3-C₆ cycloalkyl group" represents a cyclic alkyl group having 3 to 6 carbons atoms. Examples of such cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

The term "phenyl-(Ci-C₄)alkyl group" in the present invention means a phenyl group linked to a C₁-C₄ alkylene group. By the term "(C₁-C₄) alkylene group", it is understood a linear or branched divalent hydrocarbon chain comprising from 1 to 4 carbon atoms.

The term "pharmaceutically acceptable salts" means salts that are pharmaceutically acceptable and that possess the desired pharmacological activity of the parent compound. Such salts include: acid addition salts formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like; or formed with organic acids such as acetic acid, benzenesulfonic acid, benzoic acid, camphorsulfonic acid, citric acid, ethanesulfonic acid, fumaric acid, glucoheptonic acid, gluconic acid, glutamic acid, glycolic acid, hydroxynaphtoic acid, 2- hydroxyethanesulfonic acid, lactic acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, muconic acid, 2- naphthalenesulfonic acid, propionic acid, salicylic acid, succinic acid, tartaric acid, p-toluenesulfonic acid, trimethylacetic acid, and the like; or salts formed when an acidic proton present in the parent compound either is replaced by a metal ion, e. g. an alkali metal ion, an alkaline earth ion, or an aluminum ion, or coordinates with an organic or inorganic base. Acceptable organic bases include diethanolamine, ethanolamine, N- methylglucamine, triethanolamine, tromethamine, and the like. Acceptable inorganic bases include aluminum hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate and sodium hydroxide.

The term "tautomeric forms" in the present invention refers to tautomers of nucleobases, i.e. constitutional isomers of nucleobases. In a particular embodiment, the groups of formula (III) are selected from the group consistin 2-benzoxazolinone, 3-methyl-2-benzoxazolinone, benzoxazole and 2-aminobenzoxazole.

In a particular embodiment, the compound of formula (I) is selected from the group consistin AAR1 to AARll.

Those compounds are described in Table 1 hereinafter.

AAR7 2-formylamino-5-(phenylbutylaminoethyl)- phenol

HO ^-^^^" N ^^^^^^

H

H CI

AAR8 l-(2-hydroxy-4-(2(4- phenylbutylamino)ethyl)phenyl)-3-(4- phenylbutyl)urea

AAR9 N-tert-butoxycarbonyl-6- phenylbutylaminoethyl-benzoxazole

AAR10 2-amino-6(phenylbutyl-N-tert- butoxycarbonyl-aminoethyl)benzoxazoline

H ₂ N^ J IT J]

AAR11 2-amino-6(phenylbutyl-N- 1 -oxo-2- phenylethyl-aminoethyl)-benzoxazole

H ₂ N— ^ j 1 L IJ o ^;ΊΊΊ^ ^

Table 1

The compound of formula (I) as previously defined is an agonist or partial agonist of the NMDA receptor.

The term "NMDA receptor" refers to a specific type of glutamate receptor that is activated by N- methyl D-aspartate (NMDA). In the meaning of the present invention, this term may include naturally occurring NMDA receptors and modified forms thereof. The NMDA receptor can be from any source. Preferably the NMDA receptor is a mammalian NMDA receptor and even more preferably a human NMDA receptor.

By the term "receptor activity", it is understood the initiation of a pathway signalling and further activating biological processes.

By the term "NMDA receptor agonist", it is understood a natural or synthetic compound that binds to the NMDA receptor, activates said receptor for initiating a pathway signalling and further activating biological processes.

By the term "NMDA receptor partial agonist", it is understood drugs which never reach, in amplitude, 100 % of the response of the reference drug on the histamine site, such as histamine or tele-methylhistamine. By contrast, the term "NMDA receptor antagonist" means a natural or synthetic compound having the adverse biological effect of the agonist. The term "NMDA receptor partial antagonist" means a natural or synthetic compound having the adverse biological effect of the partial agonist.

The compound of formula (I) as previously defined is an agonist or partial agonist of the histamine site of the NMDA receptor.

The term "agonist or partial agonist of the histamine site of the NMDA receptor" refers to a natural or synthetic compound which binds to the histamine site of the NMDA receptor and which activates said histamine site activity.

The term "histamine site of the NMDA receptor" refers to the allosteric site of the NMDA receptor described by Williams K. (Mol Pharmacol. 1994 ), Bekkers J. (Science 1993), Vorobjev V.S. (Neuron 1993) and Burban A. (J Pharmacol Exp Ther. 2010).

By the term "histamine site activity", it is understood the initiation of a pathway signalling and further activating biological processes through the activation of the histamine site.

The agonistic or partial agonistic activity of a compound may be determined using various NMDA-induced responses such as the [3H]noradrenaline release induced by NMDA on rat hippocampal synaptosomes or the NMDA-induced currents in neurons.

The compounds and their properties are described in Table 2 hereinafter. Compound name ECso (nM) IA (in %)

AAR1 5.5 ± 0,9 40

AAR2 128±25 30

AAR3 207±35 50

AAR4 1540±120 30

AAR5 15+3 30

AAR7 30±10 40

AAR6 83±22 30

AAR8 25±5.4 50

AAR9 11+3 40

AAR11 25±5 40

Table 2: Properties of compounds of formula (I) on the histamine site of the NMDA receptor

The term "EC5₀" refers to the concentration of a drug which induces a response halfway between the baseline and the maximum effect, i.e. the concentration at which the effect is 50% of the maximum effect. It is commonly used as a measure of drug's potency.

The term "IA" refers to the intrinsic activity, i.e. the relative ability of a drug receptor complex to produce a maximum functional response. It relates to maximum percentage of activity of the drugs on the histamine site of the NMDA Receptor compared to 100 % of activity of the reference drug Histamine or tele-methylhistamine.

Preferably, the agonist or partial agonist of the histamine site of the NMDA receptor as previously defined is a compound selective for the histamine site of the NMDA receptor as compared with the other histamine receptors such as histamine HI receptor, histamine H2 receptor, histamine H3 receptor and histamine H4 receptor. Even more preferably, said compound is selective for the histamine site of the NMDA receptor as compared with the histamine HI receptor, histamine H2 receptor, histamine H3 receptor or histamine H4 receptor and is not acting or partially acting at dopamine D2 receptors.

By the term "selective for the histamine site of the NMDA receptor", it is understood that the affinity of the agonist or partial agonist of the NMDA receptor site is at least 10-fold, preferably 25-fold, more preferably 100-fold, and even more preferably 500-fold higher than the affinity for the other histamine receptors (HI, H2, H3 and H4).

In a particular embodiment, the compound of formula (I) as previously defined is an agonist or a partial agonist of the histamine site of the NDMA receptor. A partial agonist is a drug with an Intrinsic Activity lower than 95 % on the histamine site of the NDMA receptor.

The compounds of formula (I) as previously defined are able to activate the histamine site of the NMDA receptor, said compounds have an EC5₀ for the histamine site of the NMDA receptor in a nanomolar range with an intrinsic activity around 50%.

It is known from the prior art that NMDA receptor dysfunctions are involved in several major nervous system disorders. Indeed, both hyperactivity and hypofunction of NMDA receptors can contribute to pathophysiological disorders (Qiang Zhou). For example, recent studies established a link between cognitive disorders, e.g. Alzheimer's disease and Parkinson's disease, and the NMDA receptor dysfunction (A. Kumar 2015). It has also been demonstrated that such receptors are implicated in neurological diseases such as stroke, traumatic brain injury, dementia, and schizophrenia. Recent studies also put light on the fact that distinct subtypes of the NMDA receptor are differently involved in central nervous system diseases. In particular, the histamine site of the NMDA receptor may have a key role in several disorders. For example, the histamine site of the NMDA receptor has been suggested to be involved in Ischemia (Role of histamine and its receptors in cerebral ischemia, Wei-Wei Hu).

Without wishing to be bound by any theory, the inventors believe that enhancing NMDA receptor function will restore sensorimotor gating deficits observed in schizophrenia. Therefore, agonists of the NMDA receptor will be useful as anti-psychotic agents for the treatment of symptoms of this disease. Furthermore, the positive effects of agonists on LTP (long term potentiation) suggest that these compounds will also be useful for the treatment of cognitive deficits observed in schizophrenia or other psychiatric diseases. Taking into account the antinociceptive properties of NR₂B antagonists (Gogas, Cur. Opin Pharmacol. 2006, 6 : 68-74), the inventors believe that partial agonists or agonists of the NMDA receptor will be useful for the treatment of ischemia and/or neurodegenerative processes.

The inventors have surprisingly found that compounds of formula (I) are able to activate the NMDA receptor, and in particular activate the histamine site of the NMDA receptor. Consequently, compounds of formula (I) as previously defined may be used to treat diseases associated with NMDA receptor dysfunctions and in particular dysfunctions of the histamine site of the NMDA receptor. Another object of the present invention is a compound of formula (I) as previously defined for use in a method for treatment of a human or an animal.

In one embodiment, the compound of formula (I) as previously defined is a compound for use in the treatment of a nervous system disease.

In a particular embodiment, the nervous system disease is selected from the group consisting of schizophrenia, mood and attention alterations, cognitive deficits in psychiatric pathologies, Alzheimer's disease, neuropathic pain, ischemia/stroke, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, human immunodeficiency virus (HIV) type 1 -associated dementia, depression, epilepsia and alcoholism.

According to another embodiment, the compound of formula (I) as previously defined is a compound for use in the treatment of a central nervous system disease. In a particular embodiment, the central nervous system disease is selected from the group consisting of schizophrenia, mood and attention alterations and cognitive deficits in psychiatric pathologies.

Another object of the present invention is a pharmaceutical composition comprising as active principle, the compound of formula (I) as previously defined and a pharmaceutically acceptable excipient.

The term "pharmaceutical composition" in the present invention refers to any composition comprising the compound of formula (I) of the invention and at least one pharmaceutically acceptable excipient. By the term "pharmaceutically acceptable excipient" herein, it is understood a carrier medium which does not interfere with the effectiveness of the biological activity of the active ingredient(s) and which is not excessively toxic to the host at the concentration at which it is administered. Said excipients are selected, depending on the pharmaceutical form and the desired method of administration, from the usual excipients known by a person skilled in the art. According to the present invention, compounds of formula (I) may be administered as a pharmaceutical composition in an effective amount by any of the accepted modes of administration, preferably by intra- venous or oral route.

By the term "effective amount" herein, it is understood any amount of the compound of formula (I) that is sufficient to fulfil its intended purpose(s), e.g., a desired biological or medicinal response in a cell, tissue, system or patient.

The term "patient" in the present invention refers to a human or another mammal (e.g., primate, mouse, rat, rabbit, dog, cat, horse, cow, pig, camel, and the like). Preferably, the patient is a human.

Suitable dosage ranges are typically around 10-20 mg/kg of body weight daily, depending upon numerous factors such as the severity of the disease to be treated, the age and relative health of the subject, the route and the form of administration. Another object of the present invention relates to a method for treating a nervous system disease or a central nervous system disease as defined previously comprising administering to a patient in need thereof an effective amount of the compound of formula (I) as defined previously, or of a pharmaceutical composition comprising said compound. The compound of formula (I) as previously defined may be administered alone or in combination with one or more other compounds of formula (I) or other drugs well known by a person skilled in the art. Such drugs may reduce side effects induced by the compounds of formula (I) or reinforce the activity of the compounds of formula (I).

Synthesis of 2-amino-6-phenylbutylaminoethyl-benzoxazole (AAR1)

[A]

In the experimental section below, the compound numbers refer to the reaction scheme.

Experimental Section:

Step-1: To a cold solution of Compound-1 (13.0 g, 59.6 mmol ) in DMF (130 mL) was added potassium carbonate (16.4 g, 119.2 mmol) and benzyl bromide (8.7 mL, 71.5 mmol). The resulting mixture was heated at 80 °C for 1 h. After completion reaction mixture was allowed to cool to room temperature and poured in ice water and extracted with diethyl ether (200 mL x 2). The combined organic layer was washed with brine solution, dried over anhydrous sodium sulfate, filtered and concentrated to afford Compound-2 (16.0 g, Yield: 88%) as a off white solid.

Step-2: A solution of Compound-2 (16.0 g, 0.051 mol), allyltributylstannane (20.0 g, 0.062 mol) in 1,4-Dioxane (160 mL) was bubbled with nitrogen for 15 min and then PdCl₂ (PPh₃)₂ (5 mol%) was added. The resulting mixture was heated at 100 °C for 16 h. After completion of reaction, reaction mass was allowed to cool to room temperature and diluted with ethyl acetate (250 mL) and water (250 mL). The layers were separated and aqueous layer was extracted with ethyl acetate (200 mL) and the combined organic layer was washed with brine solution, dried over anhydrous sodium sulfate, filtered and concentrated. The resulting crude product was purified by column

14 chromatography (silica gel 230-400 mesh) by eluting with gradient of 0-5% ethyl acetate in hexane, product fractions were concentrated to afford Compound-3 (12.0 g, Yield: 86%) as a colorless liquid. Step-3: A solution of Compound-3 (12.0 g, 0.044 mol) in methanol (120 mL) and dichloromethane (120 mL) was purged with ozone gas for 2 h at -78°C. After the purging the excess of ozone gas was flushed with a stream of nitrogen for 15 min at -78°C. To this solution dimethyl sulfide (20 mL, 0.267 mol) was added at -78 °C and the reaction mixture was allowed stir at room temperature for 16 h. Reaction mixture was concentrated and the residue was diluted with dichloromethane (200 mL) and washed with water and brine solution. Organic layer was dried over anhydrous sodium sulphate, filtered and concentrated to afford Compound-4 (13.0 g) as a brown liquid. The crude product was used as such for the next reaction without further purification. Step-4: To a solution of crude Compound-4 (13.0 g, 0.047 mol) in dichloromethane (130 mL) was added Compound-5 (7.1 g, 0.047 mol) followed by acetic acid (0.28 mL, 0.0047 mol) at room temperature and solution was stirred for 2 h. To this mixture sodium triacetoxy borohydride (24.0 g, 0.117 mol) was added in portion at 0 °C and the resulting mixture was stirred for 16 h at room temperature. Reaction mixture was quenched with saturated aqueous sodium bicarbonate solution. The layers were separated; aqueous layer was extracted with dichloromethane (200 mL x 2). The combined organic layer was washed with brine solution and dried over anhydrous sodium sulfate, filtered and concentrated. The resulting crude product was purified by column chromatography (silica gel # 230-400 mesh) by eluting with gradient of 0-5% methanol in dichloromethane to afford the compound 6 (7.0 g, Yield :36% ) as a brown liquid.

Step-5: To a solution of Compound-6 (7.0 g, 0.017 mmol) in dichloromethane (140 mL) were added triethylamine (7.30 mL, 0.051 mol), DMAP (207 mg, 0.0017 mol) and tert-butoxycarbonyl (Boc)-anhydride (5.0 g, 0.020 mol) at 0 °C. The resulting mixture was stirred for 16 h at room temperature. The reaction mixture was diluted with water and layers were separated. Organic layer was washed with water and brine and dried over anhydrous sodium sulfate, filtered and concentrated. The crude product was purified by column chromatography (silica gel # 230-400 mesh) by eluting with gradient of 0-20% ethyl acetate in hexane to afford the Compound-7 (5.0 g, yield: 57%) as a yellow liquid. Step-6: To a solution of Compound-7 (5.0 g, 9.920 mmol) in methanol (100 mL) was added 15

10% Pd on Carbon (1.5 g, 50% moisture) and the solution was hydrogenated under the pressure of hydrogen balloon (-10 psi). After Completion, the reaction mixture was filtered through celite pad, and celite pad was washed with methanol, the filtrate was concentrated to afford Compound- 8 (3.8 g, crude) as a brown liquid which was used as such for the next reaction without further purification.

Step-7: To a solution of Compound-8 (3.8 g, 9.895 mmol) in methanol (38 mL) was added cyanogen bromide (4.1 g, 39.58 mmol) at 0 °C and the solution was stirred for 2 h at room temperature and then heated to 50 °C for 4 h. After completion, reaction mixture was concentrated under vacuum and the residue was quenched with aqueous sodium bicarbonate solution. The aqueous portion was extracted with ethyl acetate (150 mL x 2). The combined organic layer was washed with brine solution and dried over anhydrous sodium sulfate, filtered, concentrated. The crude product was purified by column chromatography (silica gel #230-400 mesh) by eluting with gradient of 0-5% methanol in dichloromethane to afford the compound-9 (3.8 g, Yield: 95%) as a brown liquid.

Step-8: To a solution of Compound-9 (3.8 g, 9.046 mmol) in Dichloromethane (40 mL) was added a solution of 20% HC1 in 1,4-dioxane (55 mL) at 0 °C. The solution was stirred for 4 h at room temperature. After completion, reaction mixture was concentrated to dryness and the residue was basified with saturated sodium bicarbonate solution. The solid precipitated was filtered off and washed with water and dried under vacuum. The solid obtained was stirred in diethyl ether (20 mL) and filtered off and washed with ether and dried under vacuum to afford the Compound- 10 (1.2 g, Yield: 44%) as a brown solid. Analytical data:

1H NMR (400 MHz, DMSO-d6): δ 7.28-7.25 (m, 4H), 7.19-7.15 (m, 4H), 7.09 (d, 1H, J=7.96 Hz), 6.93 (d, 1H, J=8.48 Hz), 2.87-2.86 (m, 2H), 2.80-2.78 (m, 2H), 2.71-2.67 (m, 2H), 2.58- 2.54 (m, 3H), 1.60-1.56 (m, 2H), 1.48-1.47 (m, 2H). The present invention will now be illustrated using the following examples and figures, which are given by way of illustration, and are in no way limiting. 16

BRIEF DESCRIPTION OF DRAWINGS

Figure. 1: Potentiation of NMDA-induced [3H]noradrenaline release effect by histaminergic ligands.

A) Effects of L-histidine, histamine, tele-methylhistamine (tele-MeHA), 3-methylhistamine (3- MeHA), and R-a-methylhistamine (R-a-MeHA) at 100 μΜ, on [3H]noradrenaline release induced by NMDA (200μΜ) and glycine (ΙμΜ) in rat hippocampal synaptosomes. Results are means ± SEM (Scanning Electron Microscopy) from 3-5 experiments run in duplicate and are expressed as dpm^g protein after deduction of spontaneous [³H]noradrenaline release. * p < 0.001 vs. control NMDA-induced release (one-way ANOVA, Student-Newman-Keuls post hoc). B) Histamine and te/e-MeHA (1 μΜ - 3 mM) induces a concentration dependent potentiation of NMDA (200μΜ)- induced release of [³H]noradrenaline (in presence of glycine ΙμΜ). Results are means ± SEM from 3-8 experiments run in duplicate and are expressed as dpm^ig protein after deduction of spontaneous and NMDA-induced [³H]noradrenaline release. C) Effects of NMDA receptor antagonists ifenprodil (■), MK-801 (o) or impromidine (·) and GABA A antagonist bicuculline (Δ) on [³H]noradrenaline release induced by te/e-MeHA (ΙΟΟμΜ). Results are means ± SEM from three experiments run in duplicate and are expressed as per cent of control te/e-MeHA effect after deduction of spontaneous and NMDA-induced [³H]noradrenaline release. Figure. 2: Effect of AARl on NMDA-induced [3H]noradrenaline release

AARl on NMDA induced-[3H]noradrenaline release in hippocampal synaptosome of rats and mice. AARl acts as is a partial agonist of the histamine site of the NMDA receptor (intrinsic activity = 40 %) with a nanomolar potency (EC₅₀ = 4nM). Figure 3. Effect of AARl on NMDA-induced currents in single hippocampal neurons.

AARl used alone induces a concentration dependent potentiation of NMDA-induced release of [³H]noradrenaline. In the presence of the full agonist te/e-MeHA (300μΜ), AARl tended to decrease NMDA-induced release of [³H]noradrenaline. AARl therefore acts as a partial agonist with an intrinsic activity of 40 %. Results are means ± SEM from 3-5 experiments run in duplicate and are expressed as dprn^g protein after deduction of spontaneous and NMDA-induced [³H]noradrenaline release.

AARl potentiated NMDA currents (50μΜ) with a pharmacological profile similar to that of the histamine site of the NMDA receptor. AARl increased the NMDA current of 29 +- 7 %, n = 12. 17

Figure 4 Mean of the prepulse inhibition effect of clozapine and AAR1

p<0,05, **p<0,01 and p<0,001 compared Solvent/Saline group

a p<0,05, b p<0,01 and c p<0,001 compared with Solvent/MK-801 group Figure 5 Startle during the prepulse inhibition test ; effect of clozapine and AAR1

**p<0,01 compared with animal receiving solvent

EXAMPLES EXEMPLE 1: characterization of agonist or antagonist activities

Agonist or antagonist activities can be characterized on various NMDA-induced responses such as the [3H]noradrenaline released induced by NMDA on rat hippocampal synaptosomes or NMDA- induced currents. [3H]noradrenaline release assay

Previous studies have established that the activation of presynaptic NMDA receptors, located upon noradrenergic nerve endings, induce [3H]noradrenaline release induced by NMDA on rat hippocampal synaptosomes. Synaptosomes are prepared according to Gray and Whittaker (Pittaluga et al., 1992) with minor modifications. Adult male Wistar rats, weighting 200-250g, are killed by decapitation. The hippocampus is then rapidly removed and homogenized (Teflon-glass Poter, 12 up-down strokes) in 40 volumes of ice-cold 0.32M sucrose.

After a first centrifugation, (lOmin, 1000 x g), synaptosomes are isolated from supernatant by a second centrifugation (12000 x g for 20 min). The synaptosomal pellet is gently suspended in a physiological medium having the following composition (mM): NaCl, 120; KC1, 0.8; KH2P04, 1.2; CaC12, 1.3; MgS04, 1,2; NaHC03, 27.5; glucose, 10; ascorbic acid, 0.06; EDTA, 0.03; (aeration with 95% 02 and 5% C02); pH 7.4. Synaptosomes are then suspended in this same medium in the require volume of assay buffer.

Synaptosomes are then incubated for 1 hour at 37°C in a rotary water bath and in an atmosphere of 95% 02 and 5% C02 with [3H]noradrenaline (final concentration 30nM, GE Healthcare, Buckingamshire, UK). During this incubation, Synaptosomes are loaded with the labelled neurotransmitter. Then, the labelling of Synaptosomes is followed by 4 washes with an Mg2+-free medium pre warmed at 37°C.

Synaptosomes are distributed in identical aliquots (200μg of protein) in a final volume of 500 μΕ and incubated with NMDA (200μΜ), glycine (ΙμΜ) and drugs to test in the presence of thioperamide and an H3 receptor antagonist to prevent the action of the heteroreceptor H3 in the 18 system. After 3 minutes of incubation at 37°C, reaction is stopped by immersion of tubes in ice- cold water, immediately followed by a centrifugation (14 000 x g, 10 sec). The amount of radioactivity released into each supernatant is finally determined by liquid scintillation using a β counter.

In rat hippocampal synaptosomes, histamine strongly potentiates NMDA-induced [3H]noradrenaline release (Figure 1A). This response displays a pharmacological profile clearly distinct from that of the previously characterized HI, H2 and H3 receptors, but similar to the preliminary pharmacology established in electrophysiology on the native (Bekkers, 1993; Vorobjev et al., 1993) or the recombinant NMDA-R (Williams, 1994) (Figure 1A).

Hippocampal [3H]noradrenaline release induced by NMDA was enhanced up to four fold and in a concentration dependent manner by histamine (Fig. IB). The profile of this response contained several signatures of the histamine-mediated effect at neuronal or recombinant NMDARs. It was reproduced by tele-methylhistamine (Figure IB), the metabolite of histamine in brain. It was NR2B selective, being sensitive to micromolar concentrations of ifenprodil and it was antagonised by impromidine, an antagonist/inverse agonist of histamine on NMDA currents (Figure 1C).

Patch-clamp on primary neuronal cultures of rat hippocampus

Patch clamp experiments was performed according to Vorobjev in primary cultures of rat hippocampus (Vorobjev VS., 1993).

AAR1 potentiated NMDA currents (50μΜ) with a pharmacological profile similar to that of the histamine site of the NMDA receptor. AAR1 increased the NMDA current of 29 +- 7 %, n = 12 (figure 3).

EXEMPLE 2: Effect of AAR1 on the histamine modulatory site of the NMDAR on prepulse inhibition deficits induced by MK-801, an NMDA receptor antagonist: a comparison with clozapine effects

Goal:

Screen the antipsychotic potential of agonists of the histamine modulatory site of the NMDA receptor using a mice model recognized to mimic sensorimotor gating deficits observed in 80- 90% of schizophrenic patients. The capacity of the AAR1 agonist of the histamine modulatory site of the NMDA receptor, to counteract MK-801 -induced prepulse inhibition deficits in mice were evaluated and compared to the effects of clozapine, an atypical antipsychotic. 19

Methods

Animals

Male Swiss mice (21-24 g) from Janvier Labs (Le Genest-St-Isle, France) were used. Animals were housed (six animals per cage) under a 12-h light-dark cycle (lights on at 7:00 A.M.) in a temperature (21±3°C) and humidity (45±5%)-controlled environment with free access to food and water.

Animals were used for the experiments at least after 5 days of habituation to laboratory conditions. All procedures were performed in conformity with National and European legislation on animal experimentation. The ethical committee of Ile-de-France approved all behavioural procedures (CEEA Paris Descartes Comite 34).

PPI of startle reflex

Startle reactivity was measured using SR-LAB startle chambers (San Diego Instruments, San Diego, CA, USA). The animal enclosures consisted of a Plexiglas restraint cylinder (3.7 cm diameter) fixed on a platform connected to a piezoelectric accelerometer that detected movement within the cylinder. Above the cylinder was a speaker capable of producing noise up to 120 dB attached to programmable audio controls. The animal enclosure was located in an illuminated, ventilated, and sound-attenuated chamber. After 5 min of habituation to the background noise (68 dB) in the startle chamber, startle stimulus trials of 120 dB intensity and 40 ms duration were applied, either alone or preceded by 100 ms with a prepulse of an intensity of 72, 76, 80, or 84 dB and 20 ms duration. Prepulse alone trials of 72, 76, 80, or 84 dB were also presented, as were trials containing no stimulus at all. A total of ten trials of each type were presented in a pseudorandom order, with the inter-trial interval varying in a random fashion from 8 to 22 s. Extra ten pulse alone trials were presented in blocks at the beginning of each test session to scale down the initial startle response to a stable stage. The percentage of PPI induced by each prepulse intensity was calculated as: 100((SP-SPP)/SP) with SP being the average startle amplitude following the startle pulses and SPP being the average startle response following the combination of a certain prepulse and the startle pulse.

Analysis of Data

PPI data were analyzed using a 3-factor ANOVA (Drug treatment x MK-801status x prepulse intensity) with repeated measurements on factor prepulse intensity, followed when appropriate by separate 2-factor ANOVA or by the Fisher's PLSD post-hoc test. Startle amplitude data were 20 analyzed by a 2-factor ANOVA (Drug treatment x MK-801 status) followed when appropriate by post-hoc comparisons (Fisher's PLSD test).

Drugs

MK-801 from Sigma Aldrich (St. Louis, MO, USA) was dissolved in NaCl 0.9%. Clozapine (Gift from Novartis, Switzerland) and AARl were solubilized in DMSO and diluted in distilled water (final concentration of DMSO, 5%). All drugs were administrated via the intraperitoneal (i.p.) route in a volume of 10 ml/kg, MK-801 (0.3 mg kg) was administrated 30 min prior to testing. AARl Agonist of the histamine modulatory site of the NMDA receptor (3 and 10 mg/kg) and Clozapine (1 and 3 mg/kg) were administrated 15 min before MK-801.

Results:

Prepulse inhibition (see figure 4)

MK-801 induced significant PPI deficits, and these effects were opposed by some of the pretreatments tested. A 3 -way ANOVA of PPI revealed a significant effect of MK-801 [F(l,185)=56.55, p<0.0001], a significant effect of pretreatment [F(5,185)=4, p<0.01] and a significant interaction MK-801 x pretreatment [F(5, 185)=2.77, p<0.05] indicating that some of the pretreatments had different effects in saline and MK-801 exposed animals. Post-hoc comparisons revealed no significant effect of pretreatments on PPI in saline-exposed animals whatever the prepulse intensity. In contrast, in MK-801 -exposed mice, PPI was significantly greater in animals pretreated with Clozapine (1 and 3 mg/kg) and AARl (10 mg/kg) as compared with animals pretreated with solvent (p<0.05, p<0.001 and p<0.01 respectively).

The overall analysis also revealed a significant effect of prepulse intensity [F(3,555)=279, p<0.001], a significant interaction of MK-801 x prepulse intensity [F(3,555)=28.1, p<0.001] and no other 2- or 3-way interactions.

Startle Amplitude (see figure 5)

MK-801 induced significant PPI deficits, and these effects were opposed by some of the pretreatments tested. A 2-way ANOVA of startle amplitude revealed that MK-801 induced a significant increase of startle amplitude [F(l,185)=83, p<0.0001]. The absence of significant interaction MK-801 x pretreatment [F(5,185)=2.18, p<0.05] indicated that the impact of MK-801 was similar whatever the pretreatment drug tested. In addition, a significant effect of pretreatment [F(5,185)=2.6, p<0.05] was also observed. The post-hoc analysis revealed that 21 globally, clozapine 3 mg/kg decrease startle amplitude in both MK-801 and saline exposed animals (p<0.01).

Conclusion

AARl (10 mg/kg) displays an anti-psychotic-like activity as shown by its significant effect in the prepulse inhibition test.

22

REFERENCES:

Throughout this application, various references describe the state of the art to which this invention pertains. The disclosures of these references are hereby incorporated by reference into the present disclosure.

Bekkers, J.M. (1993). Enhancement by histamine of NMDA-mediated synaptic transmission in the hippocampus. Science 261, 104-106. Burban A, Faucard R, Armand V, Bayard C, Vorobiev W, Arrang JM,

"Histamine potentiates N-Methyl-D-Aspartate receptors by interacting with an allosteric site distinct from the polyamine-binding site" Journal of Pharmacology and Experimental Therapeutics 2010 Mar; 332(3):912-21. Pittaluga, A., Garrone, B., and Raiteri, M. (1992). Presynaptic glycine-dependent NMDA receptors mediate enhancement of the release of [3H]NA from noradrenergic terminals of rat hippocampus. Pharmacol Res 25 Suppl 1, 113-114.

Vorobjev, V.S., Sharonova, I.N., Walsh, I.B., and Haas, H.L. (1993). Histamine potentiates N- methyl-D-aspartate responses in acutely isolated hippocampal neurons. Neuron 11, 837-844.

Williams, K. (1994). Subunit-specific potentiation of recombinant N-methyl-D-aspartate receptors by histamine. Mol Pharmacol 46, 531-541. Qiang Zhou (2013). NMDA receptors in nervous system diseases. Neuropharmacology Volume 74, November 2013, Pages 69-75.

Ashok Kumar et al. (2015). NMDA Receptor Function During Senescence: Implication on Cognitive Performance. Front Neurosci 2015; 9:473.

Wei-Wei Hu (2012). Role of histamine and its receptors in cerebral ischemia. ACS Chem. Neurosci., 2012, 3 (4), pp 238-247.

Gogas, K.R. (2006). Glutamate-based therapeutic approaches: NR2B receptor antagonists. Cur. Opin Pharmacol. 2006, 6 : 68-74.

Claims

23 CLAIMS

1. A compound of general formula (I):

wherein:

n and m each independently represents an integer from 1 to 6, preferably from 2 to 4; Ri represents -NH- or -NR_IA-;

wherein R_]A represents a phenyl-(C]-C4)alkyl group, (C3-C₆)cycloalkyl group, -C(0)-0-R_1B or -COR_1B

wherein R_IB represents:

-a (Q-G alkyl group, preferably an i-propyl or t- butyl group, or,

- a phenyl-(Ci-C4)alkyl group;

A represents a group of formula (II) or (III):

(Π) (HI) wherein denotes a single or double bond;

R₂ represents a nitrogen atom or -NHR_2A;

wherein R_2A represents -C(0)H or -C(0)NHR_2B;

wherein R_2B represents a phenyl-(Ci-C4)alkyl group;

R3 represents =0 or -OH;

R4 represents an hydrogen atom, =0 or an amino group; and

R5 represents an hydrogen atom, a (Ci-C4)alkyl group, preferably a methyl group, or -C(0)H;

or pharmaceutically acceptable salts or tautomeric forms thereof. 24

The compound as claimed in claim 1, wherein the groups of formula (III) are selected from the group consisting of 2-benzoxazolinone, 3-methyl-2-benzoxazolinone, benzoxazole and 2-aminobenzoxazole.

The compound as claimed in claim 1 or 2, which is selected from the group consisting of: 2-amino-6-phenylbutylaminoethyl-benzoxazole, 6-(phenylbutylaminoethyl)benzoxazolin-

2- one, 6-(N-benzyl-phenylbutyl-aminoethyl)benzoxazolin-2-one, 6-(phenylbutyl-N-tert- butoxycarbonyl-aminoethyl)benzoxazolin-2-one, 6-(2-(3- phenylpropylamino)ethyl)benzo[d]oxazol-2(3H)-one, 6-(2-((4-phenylbutyl)amino)ethyl)-

3- methylbenzo[d]oxazol-2-one, 2-formylamino-5-(phenylbutylaminoethyl)-phenol, l-(2- hydroxy-4-(2(4-phenylbutylamino)ethyl)phenyl)-3-(4-phenylbutyl)urea, N-tert- butoxycarbonyl-6-phenylbutylaminoethyl-benzoxazole, 2-amino-6(-phenylbutyl-N-tert- butoxycarbonyl-aminoethyl)benzoxazoline, 2-amino-6(phenylbutyl-N-l-oxo-2- phenylethyl-aminoethyl)-benzoxazole.

The compound as claimed in anyone of claims 1 to 3, for use in a method for the treatment of a human or an animal.

The compound as claimed in anyone of claims 1 to 3, for use in the treatment of a central nervous system disease.

The compound as claimed in claim 5, wherein the central nervous system disease is selected from the group consisting of schizophrenia, mood and attention alterations and cognitive deficits in psychiatric pathologies.

A pharmaceutical composition comprising the compound as claimed in anyone of claims 1 to 3 and a pharmaceutically acceptable excipient.