Patent Description:
The compounds of the invention may be useful in the treatment of many disorders associated with P2X<NUM> receptors mechanisms, such as respiratory diseases including cough, asthma, idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD).

P2X receptors are cell surface ion channels activated by extracellular Adenosine <NUM>-TriPhosphate (ATP). P2X receptor family are trimeric assemblies composed of seven distinct subunit subtypes (P2X1-<NUM>) that assemble as homomeric and heteromeric channels. All subunits share a common topology containing intracellular termini, two transmembrane helices forming the ion channels and a large extracellular domain containing the ATP binding site. Homomeric P2X<NUM>, P2X<NUM>, P2X<NUM>, P2X<NUM>, P2X<NUM>, and P2X<NUM> channels and heteromeric P2X<NUM>/<NUM> and P2X<NUM>/<NUM> channels have been fully characterized following heterologous expression. P2X receptors are abundantly distributed, and functional responses are seen in neurons, glia, epithelia, endothelia, bone, muscle, and hemopoietic tissues. On smooth muscles, P2X receptors respond to ATP released from sympathetic motor nerves (e.g., in ejaculation). On sensory nerves, they are involved in the initiation of afferent signals in several viscera (e.g., bladder, intestine) and play a key role in sensing tissue-damaging and inflammatory stimuli. Paracrine roles for ATP signaling through P2X receptors are likely in neurohypophysis, ducted glands, airway epithelia, kidney, bone and hemopoietic tissues. All P2X receptors are non-selective cation channels permeable to Na+ and Ca+ ions and are activated by ATP; however, the pharmacology of the receptor subtypes varies with respect to sensitivity to ATP and to small molecules antagonists.

In humans, the P2X<NUM> receptor has been reported in heart and spinal cord at the mRNA level and in DRG, intestine (myenteric plexus neurons), urinary bladder (urothelium and suburothelium), and dental pulp at the protein level (<NPL>).

The neurophysiological role of P2X<NUM> receptors in sensory nerve function in the airways is similar to that mediating somatic nociception (<NPL>). This similarity has driven hypotheses concerning the involvement of P2X<NUM> receptors in the symptoms of airway dysfunction including cough and bronchial hyper-reactivity (Ford AP: In pursuit of P2X<NUM> antagonists: novel therapeutics for chronic pain and and afferent sensitization, Purinergic signal <NUM> (suppl <NUM>):<NUM>-<NUM>, <NUM>; <NPL>). P2X<NUM> subunits are also co-localized in many neurons, particularly within DRG, nodose ganglia, nucleus tractus solitarius, and taste buds (<NPL>).

P2X<NUM> antagonists have been proposed for the treatment of diabetic neuropathic pain (<NPL>).

P2X<NUM> and P2X<NUM>/<NUM> channels play an important role in the development of articular hyperalgesia of arthritic joints (<NPL>).

P2X<NUM> are also a potential target for therapeutic treatment of bladder pain. They were also proposed to be analgesic targets to treat ureteral colicky pain and to facilitate ureteral stone passage (<NPL>).

P2X<NUM> over-expression is involved in poor recurrence-free survival in hepatocellular carcinoma patients and identifies the P2X<NUM> as a potential therapeutic target (<NPL>).

It has been suggested that P2X<NUM> antagonists may improve recovery of erectile function (<NPL>).

ATP enhances citric acid-evoked and histamine-evoked cough in preclinical models, effects that can be attenuated by P2X<NUM> selective antagonists (<NPL>). In humans, local delivery of ATP initiates cough and bronchospasm (<NPL>).

The therapeutic promise of P2X<NUM> antagonists for the treatment of chronic cough was first recognized by Ford and Undem (<NPL>). P2X<NUM> are expressed by airway afferent nerves and mediate hypersensitivity of the cough reflex, which is dramatically reduced by the oral P2X<NUM> antagonist, AF-<NUM> (<NPL>).

ATP is a key neurotransmitter in the taste system, acting largely via P2X<NUM>/<NUM> heteromultimer receptors. Consequently, disruption of taste function may be an unintentional consequence of therapeutic trials of pain, chronic cough and other conditions using purinergic P2X<NUM> antagonists (<NPL>.

Various compounds have been described in the literature as P2X<NUM> and/or P2X<NUM>/<NUM> Inhibitors.

<CIT>) discloses the use of diaminopyrimidine P2X<NUM>/P2X<NUM>/<NUM> antagonists for the treatment of disorders including cough, chronic cough and urge to cough, including cough associated with a respiratory disease or disorder, administering an efficacious amount of the compound disclosed. However, phthalazine derivatives are not disclosed.

<CIT>), discloses the use of cromolyn or a pharmaceutically acceptable salt thereof and P2X<NUM> and/or a P2X<NUM>/<NUM> receptor antagonist as antitussive agent, for the treatment of lung diseases and conditions.

<CIT>), discloses <NUM>,<NUM>-thiazol-<NUM>-yl substituted benzamide compounds that inhibit P2X<NUM> receptor and to pharmaceutical compositions containing such compounds, and the use of compounds for the treatment of several disorders, including the respiratory diseases.

<CIT>), discloses purine derivatives compounds having a novel P2X<NUM> and/or P2X<NUM>/<NUM> receptor antagonizing effect.

<CIT>), discloses triazine derivatives compounds having a novel P2X<NUM> and/or P2X<NUM>/<NUM> receptor antagonizing effect.

<CIT>) relates to fused heterocyclic compounds of the class tetrahydropyrido[<NUM>,<NUM>-d]pyrimidines and pharmaceutical compositions comprising such compounds. Also provided are methods for preventing and/or treating several disorders, such as neurodegenerative disorders, pain, asthma, autoimmune disorders administering the disclosed comoounds.

<CIT>) discloses <NUM>-cyanophenyl fused heterocyclic compounds of the class tetrahydropyrido[<NUM>,<NUM>-d]pyrimidines and pharmaceutical compositions comprising such compounds.

<CIT>) discloses a series of benzamides substituted with phenyl or pyridyl which are stated to be useful for treatment of diseases associated with P2X purinergic receptors, and more particularly to P2X<NUM> receptor and/ or P2X<NUM>/<NUM> receptor antagonists. However, phthalazine derivatives are not disclosed.

<CIT>) relates to phenyl- and pyridyl-substituted benzamide compounds and pharmaceutical compositions comprising such compounds, but not thiazole-substituted benzamides, rendering said compounds different from the compounds of the present invention.

<CIT>) discloses tetrazole substituted arylamides compounds antagonists of P2X<NUM> and/or P2X<NUM>/<NUM> receptors, useful for the treatment of genitourinary, pain, gastrointestinal and respiratory diseases, conditions and disorders.

Despite the above cited prior art, there is still the need of novel phthalazine derivatives compounds for treatment of diseases associated with P2X<NUM> receptors in many therapeutic areas such as in particular the respiratory diseases, preferably having a selective action on the P2X<NUM> receptor to avoid the side effect on taste.

Of note, the state of the art does not describe or suggest phthalazine derivatives compounds of general formula (I) of the present invention which represent a solution to the aforementioned need.

The present invention refers to compounds of formula (I)
<CHM>
wherein.

In a second aspect, the invention refers to a pharmaceutical composition comprising a compound of formula (I) or pharmaceutically acceptable salt thereof, either alone or in combination with another one or more active ingredient, in admixture with one or more pharmaceutically acceptable carrier or excipient.

In a third aspect, the invention provides a compound of formula (I) for the use as a medicament.

In a further aspect, the invention provides a compound of formula (I) for use in treatment of any disease wherein the P2X<NUM> receptors are involved.

In a further aspect, the invention refers to a compound of formula (I) for use in the prevention and/or treatment of respiratory diseases including cough, sub-acute or chronic cough, treatment-resistant cough, idiopathic chronic cough, post-viral cough, iatrogenic cough, asthma, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and cough associated with respiratory diseases such as COPD, asthma and bronchospasm.

Unless otherwise provided, the term compound of formula (I) comprises in its meaning stereoisomer, tautomer or pharmaceutically acceptable salt or solvate.

The term "pharmaceutically acceptable salts", as used herein, refers to derivatives of compounds of formula (I) wherein the parent compound is suitably modified by converting any of the free acid or basic group, if present, into the corresponding addition salt with any base or acid conventionally intended as being pharmaceutically acceptable.

Suitable examples of said salts may thus include mineral or organic acid addition salts of basic residues such as amino groups, as well as mineral or organic basic addition salts of acid residues such as carboxylic groups.

The term "halogen" or "halogen atoms" as used herein includes fluorine, chlorine, bromine, and iodine atom, preferably chlorine or fluorine.

The term "(Cx-Cy) alkyl" wherein x and y are integers, refers to a straight or branched chain alkyl radical having from x to y carbon atoms. Thus, when x is <NUM> and y is <NUM>, for example, the term includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl and n-hexyl.

As used herein, the term "(Cx-Cy)alkylene" wherein x and y are integers, refers to a Cx-Cyalkyl radical having in total two unsatisfied valencies, such as a divalent methylene radical.

The expressions "(Cx-Cy) haloalkyl" wherein x and y are integers, refer to the above defined "Cx-Cyalkyl" groups wherein one or more hydrogen atoms are replaced by one or more halogen atoms, which can be the same or different.

Examples of said "(Cx-Cy) haloalkyl" groups may thus include halogenated, poly-halogenated and fully halogenated alkyl groups wherein all of the hydrogen atoms are replaced by halogen atoms, e.g. trifluoromethyl or difluoro methyl, trifluoroethyl groups.

By way of analogy, the terms "(C<NUM>-C<NUM>) hydroxyalkyl" or "(C<NUM>-C<NUM>) aminoalkyl" refer to the above defined "(C<NUM>-C<NUM>) alkyl" groups wherein one or more hydrogen atoms are replaced by one or more hydroxy (OH) or amino group respectively. Examples include respectively hydroxymethyl, aminomethyl, dimethylaminopropyl and the like.

In the present description, unless otherwise provided, the aminoalkyl encompasses alkyl groups (i.e. "(C<NUM>-C<NUM>) alkyl" groups) substituted by one or more amino group (-NRARB). Thus, an example of aminoalkyl is a mono-aminoalkyl group such as RARBN-(C<NUM>-C<NUM>) alkyl.

The term "(Cx-Cy) cycloalkyl" wherein x and y are integers, refers to saturated cyclic hydrocarbon groups containing the indicated number of ring carbon atoms. Examples include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl.

The term "aryl" refers to mono cyclic carbon ring systems which have <NUM> ring atoms wherein the ring is aromatic. Examples of suitable aryl monocyclic ring systems include, for instance, phenyl.

The term "heteroaryl" refers to a mono- or bi-cyclic aromatic radical containing one or more heteroatoms selected from S, N and O, and includes radicals having two such monocyclic rings, or one such monocyclic ring and one monocyclic aryl ring, which are fused through a common bond. Examples of suitable <NUM>,<NUM>-membered heteroaryl are: are thienyl, furyl, pyrrolyl, imidazolyl, thiazolyl, isothiazolyl, pyrazolyl, oxazolyl, isoxazolyl, isothiazolyl, triazolyl, thiadiazolyl, oxadiazolyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, tetrazolyl and triazinyl.

The term "heterocyclyl" or "heterocyclic" relate to a saturated mono-, bi- or tricyclic non-aromatic radical containing one or more heteroatoms selected from S, N and O. In the case of bicyclic heterocyclic systems, included within the scope of the term are fused, spiro and bridged bicyclic systems.

The term "(Cx-Cy) heterocycloalkyl" wherein x and y are integers, refers to saturated or partially unsaturated monocyclic (Cx-Cy) cycloalkyl groups in which at least one ring carbon atom is replaced by at least one heteroatom (e.g. N, S or O) or may bear an -oxo (=O) substituent group. Said heterocycloalkyl (i.e. heterocyclic radical or group) may be further optionally substituted on the available positions in the ring, namely on a carbon atom, or on an heteroatom available for substitution. Substitution on a carbon atom includes spiro disubstitution as well as substitution on two adjacent carbon atoms, in both cases thus form additional condensed <NUM> to <NUM> membered heterocyclic ring. Examples of (Cx-Cy) heterocycloalkyl are represented by: pyrrolidinyl, imidazolidinyl, thiazolidinyl, piperazinyl, piperidinyl, morpholinyl, thiomorpholinyl, dihydro- or tetrahydro-pyridinyl, tetrahydrothiophenyl, azetidinyl, oxetanyl, tetrahydropyranyl, pyranyl, <NUM>- or <NUM>-pyranyl, dihydro- or tetrahydrofuranyl, dihydroisoxazolyl, pyrrolidin-<NUM>-one-yl, dihydropyrrolyl radicals and the like.

Specific examples of said heterocycle radicals are tetrahydrothiophene <NUM>,<NUM>-dioxide, <NUM>,<NUM>-difluoropyrrolidinyl, <NUM>-pyrrolidinyl, <NUM>-methyl-<NUM>-pyrrolidinyl, <NUM>-piperidinyl, <NUM>-piperazinyl, <NUM>-morpholinyl.

The expressions "Aryloxyl" and "Aryl (C<NUM>-C<NUM>) alkoxyl" likewise "heteroAryloxyl" and "Heteroaryl (C<NUM>-C<NUM>) alkoxyl" refer to Aryl or Heteroaryl groups attached through an oxygen bridge and chained Aryl-alkoxyl or HeteroAryl-alkoxyl groups. Examples of such groups are phenyloxy, benzyloxy and pyridinyloxy respectively.

The term "aryl (C<NUM>-C<NUM>) alkyl" refers to an aryl ring linked to a straight-chained or branched alkyl groups wherein the number of carbon atoms is from <NUM> to <NUM>, e.g. phenylmethyl (i.e. benzyl), phenylethyl or phenylpropyl.

The term (Cz-Ck)heterocycloalkyl-(Cx-Cy)alkyl wherein z and k are integers, refers to an heterocyclic ring linked to a straight-chained or branched alkyl groups having from x to y carbon atoms.

Likewise, the term "heteroaryl (Cx-Cy)alkyl" or "aryl (Cx-Cy)alkyl" refers to an heteroaryl or aryl ring linked to a straight-chained or branched alkyl groups having from x to y carbon atoms.

The expression "ring system" refers to mono- or bicyclic or polycyclic ring systems which may be saturated, partially unsaturated or unsaturated, such as aryl, (C<NUM>-C<NUM>) cycloalkyl, (C<NUM>-C<NUM>) heterocycloalkyl or heteroaryl.

The terms "group", "radical" or "fragment" or "substituent" are synonymous and are intended to indicate functional groups or fragments of molecules attachable to a bond or other fragments or molecules. Thus, as an example, a "heterocyclic radical" herein refers to a mono- or bi-cyclic saturated or partially saturated heterocyclic moiety (group, radical), preferably a <NUM> to <NUM> membered monocyclic radical, at least one further ring carbon atom in the said heterocyclic radical is optionally replaced by at least one further heteroatom independently selected from N, S or O and/or may bear an -oxo (=O) substituent group, said heterocyclic radical is further optionally including spiro disubstitution as well as substitution on two adjacent or vicinal atoms forming an additional <NUM> to <NUM> membered cyclic or heterocyclic, saturated, partially saturated or aromatic ring. Examples of said heterocycle radicals are <NUM>-pyrrolidinyl, <NUM>-piperidinyl, <NUM>-piperazinyl, <NUM>-morpholinyl and the like.

A dash ("-") that is not between two letters or symbols is meant to represent the point of attachment for a substituent. When graphically represented the point of attachment in a cyclic functional group is indicated with a dot ("•") localized in one of the available ring atom where the functional group is attachable to a bond or other fragment of molecules.

An oxo moiety is represented by (O) as an alternative to the other common representation, e.g. (=O). Thus, in terms of general formula, the carbonyl group is herein represented as -C(O)-, in general, the bracketed group is a lateral group, not included into the chain, and brackets are used, when deemed useful, to help disambiguating linear chemical formulas; e.g. the sulfonyl group -SO<NUM>- might be also represented as -S(O)<NUM>- to disambiguate e.g. with respect to the sulfinic group -S(O)O-.

Whenever basic amino or quaternary ammonium groups are present in the compounds of formula I, physiologically acceptable anions may be present, selected among chloride, bromide, iodide, trifluoroacetate, formate, sulfate, phosphate, methanesulfonate, nitrate, maleate, acetate, citrate, fumarate, tartrate, oxalate, succinate, benzoate, p-toluenesulfonate, pamoate and naphthalene disulfonate. Likewise, in the presence of acidic groups such as COOH groups, corresponding physiological cation salts may be present as well, for instance including alkaline or alkaline earth metal ions.

It will be apparent that compounds of formula (I) when contain one or more stereogenic center, may exist as optical stereoisomers.

Where the compounds according to the invention have at least one stereogenic center, they may accordingly exist as enantiomers. Where the compounds according to the invention possess two or more stereogenic centers, they may additionally exist as diastereoisomers. All such single enantiomers, diastereoisomers and mixtures thereof in any proportion are encompassed within the scope of the present invention. The absolute configuration (R) or (S) for carbon bearing a stereogenic center is assigned on the basis of Cahn-Ingold-Prelog nomenclature rules based on groups' priorities.

The invention further concerns the corresponding deuterated derivatives of compounds of formula (I).

All preferred groups or embodiments described above and herebelow for compounds of formula I may be combined among each other and apply as well mutatis mutandis.

As above indicated, the present invention refers to a series of compounds represented by the general formula (I) as herein below described in details, which are endowed with an antagonist property versus receptor P2X<NUM>.

Differently from similar compounds of the prior art, the compounds of formula (I) of the present invention are able to act as antagonist P2X<NUM> in a substantive and effective way, particularly appreciated by the skilled person when looking at a suitable and efficacious compounds useful for the treatment of respiratory disease, in particular chronic cough.

As indicated in the experimental part, the compounds of formula (I) have an activity as shown in Table <NUM>, wherein for each compound is reported the potency expressed as half maximal inhibitory concentration (pIC<NUM>) on receptors.

As further advantage, the compound of formula (I) have surprisingly been found to effectively and selectively inhibit mainly the P2X<NUM> receptor and said compounds are useful for the treatment of respiratory disease avoiding adverse effect, such as loss of taste response. In fact, as it can be appreciated in Table <NUM>, the compounds of formula (I) show a greater acitivity versus the receptor P2X<NUM> in comparison to the receptor P2X<NUM>/<NUM>.

Thus, in one aspect the present invention relates to a compound of general formula (I) as P2X<NUM> antagonist
<CHM>
wherein.

In a preferred embodiment Z is aryl or (<NUM>-<NUM> membered)-heteroaryl wherein the heteroaryl is selected from the group consisting of thiazole, pyridine, pyrimidine and pyrazole.

In a preferred embodiment R<NUM> is heteroaryl or (C<NUM>-C<NUM>)cycloalkyl- wherein the heteraaoryl is selected from the group consisting of pyridazine, pyrimidine and oxadiazole, and the (C<NUM>-C<NUM>)cycloalkyl- is cyclopropyl.

In a preferred embodiment, the invention refers to at least one of the compounds listed in the Table <NUM> below and pharmaceutical acceptable salts thereof.

In one preferred embodiment, the invention refers to a compound of formula (I), wherein Y and R<NUM> are H, represented by the formula Ia
<CHM>
wherein.

The compounds of formula (I) including all the compounds or at least one of the here above listed can be generally prepared according to the procedure outlined in detail in the Schemes shown below using generally known methods.

In one embodiment of the present invention, compound of formula (I) may be prepared according to SCHEME <NUM> from compound (II).

Compound (IV) may be prepared from Compound (II) by a two-step ring closure reaction mediated by the NBS/hydrazine system.

Alternatively, Compound (IV) may be prepared from Compound (III) by a four-step sequence ring closing reaction as briefly described in Scheme <NUM>.

Compound (VI) may be prepared from Compound (IV) by metal-catalyzed Miyaura borylation reaction.

Compound (V) may be prepared from Compound (IV) by a metal-catalyzed cross coupling reaction like Stille or Suzuki or similars as described in "<NPL> with a suitable reagent like (Reag.

Alternatively, Compound (V) may be prepared from Compound (VI) by a metal-catalyzed cross coupling reaction like Stille or Suzuki or similars as described in "<NPL> with a suitable reagent like (Reag.

Compound (VII) may be prepared from Compound (V) by a deoxyhalogenation reaction mediated by reagents like, for example, Phosphorous oxychloride.

Compound of formula (I) may be prepared from Compound (VII) by a reaction with a suitable amine (Reag. <NUM>) in the presence of a base like, for example TEA or DIPEA.

Some compounds of formula (I) may contain a protected hydroxyl or amino group which were then removed under well known procedures.

The compounds of the present invention have surprisingly been found to effectively inhibit P2X<NUM> receptor and said compounds are useful for the treatment of respiratory disease.

In one embodiment, representative compounds of formula (I) of the present invention have surprisingly been found to effectively and selectively inhibit P2X<NUM> receptor and said compounds are useful for the treatment of respiratory disease avoiding adverse effect, such as loss of taste response.

In a preferred embodiment, the compound of formula (I) are selective P2X<NUM> antagonist wherein the selective P2X<NUM> antagonist is at least <NUM>-fold selective for P2X<NUM> homomeric receptor antagonism versus P2X<NUM>/<NUM> heteromeric receptor antagonism.

In a further preferred embodiment, the selective P2X<NUM> antagonist is at least <NUM>-fold selective for P2X<NUM> homomeric receptor antagonism versus P2X<NUM>/<NUM> heteromeric receptor antagonism.

The present invention also provides a pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof in admixture with one or more pharmaceutically acceptable carrier or excipient, either alone or in combination with one or more further active ingredient.

In one aspect, the invention refers to a compound of formula (I) according to the invention for use as a medicament.

In a further aspect, the invention refers to the use of a compound of formula (I) of the invention, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of disorders associated with P2X<NUM> receptors mechanism, preferably for the treatment of respiratory diseases.

Preferably, the invention refers to a compound of formula (I) for use in the prevention and /or treatment of respiratory diseases, preferably cough, sub-acute or chronic cough, treatment-resistant cough, idiopathic chronic cough, post-viral cough, iatrogenic cough, asthma, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD) and cough associated with respiratory diseases such as COPD, asthma and bronchospasm.

More preferably, the invention refers to a compounds of formula (I) for use in the prevention and /or treatment of chronic cough and cough associated with respiratory diseases such as COPD, asthma and bronchospasm.

In a further preferred embodiment, the disorder is chronic cough.

The methods of treatment comprise administering a safe and effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof to a patient in need thereof. As used herein, "safe and effective amount" in reference to a compound of formula (I) or a pharmaceutically acceptable salt thereof or other pharmaceutically-active agent means an amount of the compound sufficient to treat the patient's condition but low enough to avoid serious side effects and it can nevertheless be routinely determined by the skilled artisan. The compounds of formula (I) or pharmaceutically acceptable salts thereof may be administered once or according to a dosing regimen wherein a number of doses are administered at varying intervals of time for a given period of time. Typical daily dosages may vary depending upon the particular route of administration chosen.

The invention also provides pharmaceutical compositions of compounds of formula (I) in admixture with one or more pharmaceutically acceptable carrier or excipient, for example those described in <NPL>, N.

Administration of the compounds of the invention and their pharmaceutical compositions may be accomplished according to patient needs, for example, orally, nasally, parenterally (subcutaneously, intravenously, intramuscularly, intrasternally and by infusion) and by inhalation.

Preferably the compounds of the present invention may be administered orally or by inhalation. More preferably the compounds of the present invention are administered orally.

Various solid oral dosage forms can be used for administering compounds of the invention including such solid forms as tablets, gelcaps, capsules, caplets, granules, lozenges and bulk powders. The compounds of the invention can be administered alone or combined with various pharmaceutically acceptable carriers, diluents (such as sucrose, mannitol, lactose, starches) and known excipients, including suspending agents, solubilizers, buffering agents, binders, disintegrants, preservatives, colorants, flavorants, lubricants and the like. Time release capsules, tablets and gels are also advantageous in administering the compounds of the invention.

Preferably the compounds of the invention are administered in forms of tablets.

Various liquid oral dosage forms can also be used for administering compounds of the invention, including aqueous and non-aqueous solutions, emulsions, suspensions, syrups, and elixirs. Such dosage forms can also contain suitable known inert diluents such as water and suitable known excipients such as preservatives, wetting agents, sweeteners, flavorants, as well as agents for emulsifying and/or suspending the compounds of the invention. The compounds of the invention may be injected, for example, intravenously, in the form of an isotonic sterile solution.

For the treatment of the diseases of the respiratory tract, the compounds according to the invention are preferably administered by inhalation.

Inhalable preparations include inhalable powders, propellant-containing metering aerosols or propellant-free inhalable formulations.

For administration as a dry powder, single- or multi-dose inhalers known from the prior art may be utilized. In that case the powder may be filled in gelatine, plastic or other capsules, cartridges or blister packs or in a reservoir.

A diluent or carrier chemically inert to the compounds of the invention, e.g. lactose or any other additive suitable for improving the respirable fraction may be added to the powdered compounds of the invention.

Inhalation aerosols containing propellant gas such as hydrofluoroalkanes may contain the compounds of the invention either in solution or in dispersed form. The propellant-driven formulations may also contain other ingredients such as co-solvents, stabilizers and optionally other excipients.

The propellant-free inhalable formulations comprising the compounds of the invention may be in form of solutions or suspensions in an aqueous, alcoholic or hydroalcoholic medium and they may be delivered by jet or ultrasonic nebulizers known from the prior art or by soft-mist nebulizers.

Preferably, the compound of the present invention are administered orally.

The compounds of the invention can be administered as the sole active agent or in combination with other pharmaceutical active ingredients.

Preferably, the compound of the present invention can be combined with therapeutic agents or active ingredients useful for the treatment of disease which are related to or mediated by P2X<NUM> receptor.

The dosages of the compounds of the invention depend upon a variety of factors including among others the particular disease to be treated, the severity of the symptoms, the route of administration, and the like.

The invention is also directed to a device comprising a pharmaceutical composition comprising a compound of formula (I) according to the invention, in form of a single- or multi-dose dry powder inhaler or a metered dose inhaler.

The various aspects of the invention described in this application are illustrated buy the following examples which are not meant to limit the invention in any way. following examples illustrate the invention.

The example testing experiments described herein serve to illustrate the present invention and the invention is not limited to the examples given.

Chemical names were generated using the Dotmatics software. In some cases generally accepted names of commercially available reagents were used in place of Dotmatics software generated names.

All reagents, for which the synthesis is not described in the experimental part, are either commercially available, or are known compounds or may be formed from known compounds by known methods by a person skilled in the art.

UPLC-MS was performed on a Waters DAD + Waters SQD2, single quadrapole UPLC-MS spectrometer using an Acquity UPLC BEH Shield RP18 <NUM> <NUM> × <NUM> (Plus guard cartridge), maintained at temp column being initially held at <NUM>% acetonitrile/water (with <NUM> ammonium bicarbonate in each mobile phase) for <NUM> minutes, followed by a linear gradient of <NUM>-<NUM>% within <NUM> minutes and then held at <NUM>% for <NUM> minutes (F = <NUM>/min).

UPLC-MS was performed on a Waters DAD + Waters SQD2, single quadrapole UPLC-MS spectrometer using an Acquity UPLC BEH Shield RP18 <NUM> <NUM> × <NUM> (Plus guard cartridge), maintained at temp column being initially held at <NUM>% Acetonitrile (Far UV grade) with <NUM>% (V/V) formic acid / Water (High purity via PureLab Option unit) with <NUM>% formic acid for <NUM> minutes, followed by a linear gradient of <NUM>-<NUM>% within <NUM> minutes and then held at <NUM>% for <NUM> minutes (F = <NUM>/min).

<NUM>H Nuclear magnetic resonance (NMR) spectroscopy was carried out using a Bruker or Varian instruments operating at <NUM> using the stated solvent at around RT unless otherwise stated. In all cases, NMR data were consistent with the proposed structures. Characteristic chemical shifts (δ) are given in parts-per-million using conventional abbreviations for designation of major peaks: e.g. s, singlet; d, doublet; t, triplet; q, quartet; dd, doublet of doublets; dt, doublet of triplets; m, multiplet; br, broad.

Preparative HPLC purification was performed by reverse phase HPLC using a Waters Fractionlynx preparative HPLC system (<NUM> pump, <NUM>/<NUM> UV/VIS detector, <NUM> liquid handler) or an equivalent HPLC system such as a Gilson Trilution UV directed system. The Waters <NUM> liquid handler acted as both auto-sampler and fraction collector. The columns used for the preparative purification of the compounds were a Waters Sunfire OBD Phenomenex Luna Phenyl Hexyl or Waters Xbridge Phenyl at <NUM> <NUM> × <NUM> or Waters CSH Phenyl Hexyl, <NUM> × <NUM>, <NUM> column. Appropriate focused gradients were selected based on acetonitrile and MeOH solvent systems under either acidic or basic conditions. The modifiers used under acidic/basic conditions were formic acid or trifluoroacetic acid (<NUM>% V/V) and ammonium bicarbonate (<NUM>) respectively. The purification was controlled by Waters Fractionlynx software through monitoring at <NUM>-<NUM>, and triggered a threshold collection value at <NUM> and, when using the Fractionlynx, the presence of target molecular ion as observed under API conditions. Collected fractions were analysed by LCMS (Waters Acquity systems with Waters SQD).

The diastereomeric separation of compounds was achieved by Supercritical Fluid Chromatography (SFC) using a Waters Thar Prep <NUM> preparative SFC system (P200 CO2 pump, <NUM> modifier pump, <NUM> UV/VIS detector, <NUM> liquid handler with Stacked Injection Module). The Waters <NUM> liquid handler acted as both auto-sampler and fraction collector. Appropriate isocratic methods were selected based on MeOH, EtOH or isopropanol solvent systems under un-modified or basic conditions. The standard SFC method used was modifier, CO2, <NUM>/min, <NUM> Bar backpressure, <NUM> column temperature. The modifier used under basic conditions was diethylamine (<NUM>% V/V). The modifier used under acidic conditions was either formic acid (<NUM>% V/V) or trifluoroacetic acid (<NUM>% V/V). The SFC purification was controlled by Waters Fractionlynx software through monitoring at <NUM>-<NUM> and triggered at a threshold collection value, typically <NUM>. Collected fractions were analysed by SFC (Waters/Thar SFC systems with Waters SQD). The fractions that contained the desired product were concentrated by vacuum centrifugation.

SFC-MS was performed on a Waters/Thar SFC systems with Waters SQD using a YMC Amylose-C column with a <NUM>% methyl alcohol/CO<NUM> (with <NUM>% diethylamine) isocratic run at <NUM>/min, <NUM> Bar backpressure, <NUM> column temperature.

SFC-MS was performed on a Waters/Thar SFC systems with Waters SQD using a YMC Cellulose-C column with a <NUM>% methyl alcohol/CO<NUM> (with <NUM>% diethylamine) isocratic run at <NUM>/min, <NUM> Bar backpressure, <NUM> column temperature.

SFC-MS was performed on a Waters/Thar SFC systems with Waters SQD using a Lux Cellulose-<NUM> column with a <NUM>% iso-propyl alcohol/CO<NUM> (with <NUM>% diethylamine) isocratic run at <NUM>/min, <NUM> Bar backpressure, <NUM> column temperature.

SFC-MS was performed on a Waters/Thar SFC systems with Waters SQD using a YMC Cellulose-C column with a <NUM>% iso-propyl alcohol/CO<NUM> (with <NUM>% diethylamine) isocratic run at <NUM>/min, <NUM> Bar backpressure, <NUM> column temperature.

<NUM>-Bromo-<NUM>-chloroisoquinoline (<NUM>, <NUM> mmol), potassium carbonate (<NUM>, <NUM> mmol) and <NUM>-methylpyridazin-<NUM>-yl)methanamine hydrochloride (<NUM>, <NUM> mmol) were dissolved in NMP (<NUM>). The reaction mixture was heated at <NUM> for <NUM> minutes in a microwave reactor. Saturated aqueous sodium chloride solution (<NUM>) was added and the crude was extracted with a mixture of chloroform / <NUM>-propanol (<NUM>:<NUM>) (<NUM> × <NUM>). The organic layer was dried over dried over MgSO4 and the solvent was removed in vacuo. The residue was purified by chromatography on silica eluting with - <NUM>-<NUM>% MeOH in DCM to give the title compound as an off-white solid (<NUM>, <NUM> %).

LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

A mixture of <NUM>-bromoisobenzofuran-<NUM>(<NUM>)-one (<NUM>, <NUM> mmol), N-bromosuccinimide (<NUM>, <NUM> mmol) and AIBN (<NUM>, <NUM> mmol) in <NUM>,<NUM>-dichloroethane (<NUM>) was heated at reflux for two hours, cooled to RT and evaporated. The residue was washed with water (<NUM>) and the resultant yellow gum heated in water (<NUM>) at reflux for three hours then cooled to RT. The precipitated solid was filtered, washed with water and air dried. The solid was dissolved in <NUM>-propanol (<NUM>) and <NUM>% hydrazine hydrate (<NUM>) was added. The resulting mixture was heated at reflux for <NUM>. The mixture was cooled, filtered, the solid was washed with water (<NUM>) and dried to afford the title compound as a colourless solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM>-<NUM> (m, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>).

Nitrogen gas was bubbled for <NUM> minutes through a mixture of <NUM>-bromophthalazin-<NUM>-ol (Intermediate <NUM>) (<NUM>, <NUM> mmol), <NUM>-fluorobenzeneboronic acid (<NUM>, <NUM> mmol), potassium carbonate (<NUM>, <NUM> mmol) in <NUM>,<NUM>-dioxane (<NUM>) / water (<NUM>) and Pd(dppf)Cl2 (<NUM>, <NUM> mmol). The mixture was heated at <NUM> for <NUM>. The mixture was cooled, diluted with EtOAc (<NUM>). The organic phase was separated, concentrated in vacuo and the residue was purified by chromatography on silica eluting with <NUM>-<NUM>% MeOH in DCM gradient to afford the title compound as a pale pink solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, CDCl3): δ <NUM> (s, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>).

Isopropyl magnesium chloride (<NUM>, <NUM> mmol, <NUM> in THF) was added dropwise to a stirred solution of methyl <NUM>-bromo-<NUM>-iodobenzoate (<NUM>, <NUM> mmol) in THF (<NUM>) at -<NUM> under nitrogen. The resulting mixture was stirred at <NUM> for <NUM> minutes under nitrogen atmosphere then anhydrous zinc bromide (<NUM>, <NUM> mmol) was added and the resulting precipitate was stirred for <NUM> minutes at <NUM>. Cyclopropanecarbonyl chloride (<NUM>, <NUM> mmol) and tetrakis(triphenylphosphine)palladium(<NUM>) (<NUM>, <NUM> mmol) were added and the mixture heated at <NUM> for <NUM> hours. The reaction mixture was cooled to RT and quenched by the addition of an aqueous saturated ammonium chloride solution (<NUM>). The resultant solution was extracted with Et2O (<NUM> × <NUM>). The organic layers were combined and washed with water, passed through a hydrophobic frit and the solvent was removed in vacuo to yield a yellow gum. To a solution of the residue in EtOH (<NUM>) was added hydrazine hydrate (<NUM>, <NUM> mmol) dropwise and the mixture was stirred at RT for <NUM> hours. The solvent was removed in vacuo, the residue was purified by chromatography on silica gel eluting with <NUM> - <NUM>% EtOAc in iso-hexane to afford the title compound as a pale yellow solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, CDCl3): δ <NUM> (br s, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

The following intermediates reported in the table below were prepared according to the procedure described for the preparation of <NUM>-bromo-<NUM>-cyclopropylphthalazin-<NUM>-ol.

Nitrogen was bubbled for <NUM> minutes through a suspension of <NUM>-bromo-<NUM>-cyclopropylphthalazin-<NUM>-ol (Intermediate <NUM>) (<NUM>, <NUM> mmol), <NUM>-fluorophenyl boronic acid (<NUM>, <NUM> mmol), potassium carbonate (<NUM>, <NUM> mmol), Pd(dppf)Cl2 (<NUM>, <NUM> mmol) in <NUM>,<NUM>-dioxane (<NUM>) and water (<NUM>). The resulting mixture was stirred at <NUM> for <NUM> hours. The reaction mixture was cooled to RT. Water (<NUM>) was added and the reaction was extracted with EtOAc (<NUM> × <NUM>). The combined organic phases were passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by chromatography on silica gel eluting with <NUM> - <NUM>% MeOH in DCM to afford the title compound as a beige solid (<NUM>, <NUM>%). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

A mixture of <NUM>-cyclopropyl-<NUM>-(<NUM>-fluorophenyl)phthalazin-<NUM>-ol (<NUM>, <NUM> mmol), phosphorus(V) oxychloride (<NUM>, <NUM> mmol) and <NUM>,<NUM> dichloroethane (<NUM>) was heated at <NUM> under nitrogen atmosphere for <NUM> hours. The reaction was cooled to RT and concentrated in vacuo. The residue was partitioned between water and DCM. The combined organic phases were washed with saturated aqueous sodium hydrogen carbonate solution, passed through a hydrophobic frit and the solvent was removed in vacuo to afford the title compound as a brown solid (<NUM>, <NUM>%).

The following intermediates reported in the table below were prepared according to the procedure described for the preparation of <NUM>-chloro-<NUM>-cyclopropyl-<NUM>-(<NUM>-fluorophenyl)phthalazine above.

Nitrogen gas was bubbled through a mixture of <NUM>-bromo-<NUM>-((tetrahydro-<NUM>-pyran-<NUM>-yl)methyl)phthalazin-<NUM>-ol (Intermediate <NUM>) (<NUM>, <NUM> mmol), bis(neopentyl glycolato) diboron (<NUM>, <NUM> mmol), Pd(dppf)Cl2 (<NUM>, <NUM> mmol) and potassium acetate (<NUM>, <NUM> mmol) in dioxane (<NUM>). The mixture was heated at <NUM> for <NUM> hours. The reaction mixture was cooled and taken on to the next step as a dioxane solution without further purification. Aqueous cesium carbonate solution (<NUM>, <NUM> mmol) in water (<NUM>) and <NUM>-bromo-<NUM>-methylthiazole (<NUM>, <NUM> mmol) were added. The resulting mixture was heated at <NUM> for an additional <NUM> hours. The reaction mixture was cooled, filtered through Celite® and the filter cake was washed with EtOAc (<NUM> × <NUM>). The combined organic phases were passed through a hydrophobic frit and the solvent was removed in vacuo. The residue was purified by chromatography on silica gel eluting with <NUM>-<NUM>% <NUM>:<NUM> EtOAc/EtOH in cyclohexane to afford the title compound as a beige solid (<NUM>, <NUM>% over <NUM> steps).

A mixture of <NUM>-(<NUM>-methylthiazol-<NUM>-yl)-<NUM>-((tetrahydro-<NUM>-pyran-<NUM>-yl)methyl)phthalazin-<NUM>-ol (<NUM>, <NUM> mmol), phosphorus(V) oxychloride (<NUM>, <NUM> mmol) and <NUM>,<NUM> dichloroethane (<NUM>) was heated at <NUM> under nitrogen for <NUM> hours. The reaction mixture was cooled to RT and concentrated in vacuo. The resulting residue was partitioned between water and DCM. The combined organic phases were washed with saturated aqueous sodium hydrogen carbonate solution, passed through a hydrophobic frit and the solvent was removed in vacuo to afford the title compound as a pale brown solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, CDCl<NUM>): δ <NUM> (s, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (s, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>).

A mixture of <NUM>-chloro-<NUM>-(<NUM>-methylpyrimidin-<NUM>-yl)-<NUM>-(tetrahydro-<NUM>-pyran-<NUM>-yl)phthalazine (Intermediate <NUM>) (<NUM>, <NUM> mmol) and (<NUM>-methylpyridazin-<NUM>-yl)methanamine hydrochloride (<NUM>, <NUM> mmol) in chloroform (<NUM>) was heated in a sealed tube under nitrogen for <NUM> hours at <NUM>. The mixture was cooled to RT, diluted with EtOAc (<NUM>) and washed with a saturated aqueous sodium chloride solution. The organic phase was passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by preparative HPLC to afford the title compound as an off-white solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM> (s, <NUM>), <NUM> (s, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (s, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

A mixture of <NUM>-(<NUM>-fluorophenyl)phthalazin-<NUM>-ol (intermediate <NUM>) (<NUM>, <NUM> mmol) and phosphorous oxychloride (<NUM>, <NUM> mmol) in <NUM>,<NUM>-dichloroethane (<NUM>) was heated at <NUM> for <NUM>. The cooled mixture was diluted with DCM (<NUM>), cooled in ice and treated with saturated NaHCO<NUM> (<NUM>). The phases were separated, and the aqueous phase was extracted with DCM (<NUM> × <NUM>). Combined organic phases were dried on MgSO<NUM> and the solvent removed in vacuo. The resultant brown solid triturated with Et<NUM>O (<NUM> × <NUM>) and dried to afford a yellow coloured solid (<NUM>). <NUM> of this solid was treated with cyclopropylmethylamine (<NUM>, <NUM> mmol) and heated at <NUM> in a capped microwave vial for <NUM>. The solvent was removed in vacuo and the residue purified by preparative HPLC to afford N-(cyclopropylmethyl)-<NUM>-(<NUM>-fluorophenyl)phthalazin-<NUM>-amine as an off white solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

The following compound was obtained using the same procedure used for the preparation of N-(cyclopropylmethyl)-<NUM>-(<NUM>-fluorophenyl)phthalazin-<NUM>-amine.

A mixture of <NUM>-chloro-<NUM>-cyclopropyl-<NUM>-(<NUM>-fluorophenyl)phthalazine (Intermediate <NUM>) (<NUM>, <NUM> mmol) and (R)-<NUM>-(<NUM>-(trifluoromethyl)pyrimidin-<NUM>-yl)ethan-<NUM>-amine (<NUM>, <NUM> mmol) was heated in a sealed tube under nitrogen for <NUM> hours at <NUM>. The resulting reaction was cooled to RT, diluted with EtOAc (<NUM>), washed with saturated aqueous sodium chloride solution. The organic phase was collected, passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by preparative HPLC to afford the title compound as an off-white solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM> (s, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

The following compound reported in the table below were prepared according to the procedure described for the preparation of (R)-<NUM>-cyclopropyl-<NUM>-(<NUM>-fluorophenyl)-N-(<NUM>-(<NUM>-(trifluoromethyl)pyrimidin-<NUM>-yl)ethyl)phthalazin-<NUM>-amine above.

Nitrogen gas was bubbled for <NUM> minutes through a mixture of <NUM>-bromo-<NUM>-(tetrahydro-<NUM>H-pyran-<NUM>-yl)phthalazin-<NUM>-ol (intermediate <NUM>) (<NUM>, <NUM> mmol), bis(neopentyl glycolato) diboron (<NUM>, <NUM> mmol), Pd(dppf)Cl<NUM> (<NUM>, <NUM> mmol) and potassium acetate (<NUM>, <NUM> mmol) in dioxane (<NUM>). The mixture was heated at <NUM> for <NUM> hours. The reaction mixture was cooled and taken on to the next step as a dioxane solution without further purification. To this solution was added aqueous cesium carbonate (<NUM>, <NUM> mmol, <NUM>) and <NUM>-bromo-<NUM>-fluoropyridine (<NUM>, <NUM> mmol). The resulting mixture was heated at <NUM> for <NUM> hours. The reaction was cooled, filtered through Celite® and the filter cake washed with EtOAc (<NUM> × <NUM>). The organic phases were combined, passed through a hydrophobic frit and the solvent was removed in vacuo. The residue was purified by chromatography on silica gel eluting with <NUM>-<NUM>% <NUM>:<NUM> EtOAc/EtOH in cyclohexane to afford the title compound as a pale orange solid (<NUM>, <NUM>% over <NUM> steps).

<NUM>H NMR (<NUM>, CDCl<NUM>): δ <NUM> (s, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>).

A mixture of <NUM>-(<NUM>-fluoropyridin-<NUM>-yl)-<NUM>-(tetrahydro-<NUM>-pyran-<NUM>-yl)phthalazin-<NUM>-ol (<NUM>, <NUM> mmol), phosphorus(V) oxychloride (<NUM>, <NUM> mmol) and <NUM>,<NUM> dichloroethane (<NUM>) was heated at <NUM> under nitrogen for <NUM> hours. The reaction was cooled to RT and the solvent was removed in vacuo. The residue was partitioned between water and DCM. The aqueous phase was extracted with dichloromethane (<NUM> × <NUM>). The organic phases were combined, washed with an aqueous saturated sodium hydrogen carbonate solution, passed through a hydrophobic frit. The solvent was removed in vacuo to give the title compound (<NUM>, <NUM>%) as a pale brown solid, which was taken on to the next step without further purification.

A mixture of <NUM>-Chloro-<NUM>-(<NUM>-fluoropyridin-<NUM>-yl)-<NUM>-(tetrahydro-<NUM>-pyran-<NUM>-yl)phthalazine (<NUM>, <NUM> mmol), <NUM>-methyl-<NUM>,<NUM>,<NUM>-oxadiazol-<NUM>-yl)methanamine. hydrochloride (<NUM>, <NUM> mmol) in chloroform (<NUM>) and Et<NUM>N ( <NUM>, <NUM> mmol) were heated in a sealed tube under nitrogen for <NUM> hours at <NUM>.

The resulting mixture was cooled to RT, diluted with EtOAc (<NUM>) and washed with saturated aqueous sodium chloride. The organic phases were passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by preparative HPLC to afford the title compound as an off-white solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

The following compounds reported in the table below were prepared according to the procedure described for the preparation of <NUM>-(<NUM>-Fluoro-<NUM>-pyridyl)-N-[(<NUM>-methyl-<NUM>,<NUM>,<NUM>-oxadiazol-<NUM>-yl)methyl]-<NUM>-tetrahydropyran-<NUM>-yl-phthalazin-<NUM>-amine:.

The following compounds reported in the table below were prepared according to the procedure described for the preparation of <NUM>-(<NUM>-Fluoro-<NUM>-pyridyl)-N-[(<NUM>-methyl-<NUM>,<NUM>,<NUM>-oxadiazol-<NUM>-yl)methyl]-<NUM>-tetrahydropyran-<NUM>-yl-phthalazin-<NUM>-amine. The single isomers were obtained by chiral preparative SFC purification of the corresponding racemic mixture.

Nitrogen gas was bubbled for <NUM> minutes through a mixture of <NUM>-bromo-phthalazin-<NUM>-ol (<NUM>, <NUM> mmol) (Intermediate <NUM>) and <NUM>-methyl-<NUM>-(tributylstannyl)thiazole (<NUM>, <NUM> mmol) in anhydrous <NUM>,<NUM>-dioxane (<NUM>) and anhydrous toluene (<NUM>). Tetrakis(triphenylphosphine) palladium (<NUM> (<NUM>, <NUM> mmol) was added. The mixture was heated in microwave reactor at <NUM> for <NUM> hours, cooled, diluted with DCM and the solvent was removed in vacuo. The residue was purified by chromatography on silica gel eluting with <NUM> - <NUM>% MeOH in DCM to afford the title compound as a colourless solid (<NUM>, <NUM>%).

A mixture of <NUM>-(<NUM>-methylthiazol-<NUM>-yl)phthalazin-<NUM>-ol (<NUM>, <NUM> mmol) and phosphorus(V) oxychloride (<NUM>) in <NUM>,<NUM>-dichloroethane (<NUM>) was heated at <NUM> for <NUM> hours. The mixture was cooled, diluted with DCM (<NUM>) and washed with cold saturated sodium hydrogen carbonate (<NUM>). The organic phase was separated, and the aqueous layer extracted with DCM (<NUM>). The combined organic phases were dried on MgSO<NUM>, filtered and the solvent was removed in vacuo. The residue was added to (<NUM>-methylpyridazin-<NUM>-yl)methanamine and the mixture was heated at <NUM> for <NUM> hours and then allowed to cool. The solvent was removed in vacuo and the residue was purified by reverse phase preparative HPLC to afford the title compound as a pale brown solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM>-<NUM> (m, <NUM>), <NUM> (s, <NUM>), <NUM> (t, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (s, <NUM>), <NUM> (d, J = <NUM>, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

<NUM>-(<NUM>-Chloro-<NUM>-((tetrahydro-<NUM>H-pyran-<NUM>-yl)methyl)phthalazin-<NUM>-yl)-<NUM>-methylthiazole (<NUM>, <NUM> mmol) (Intermediate <NUM>) and (<NUM>-(trifluoromethyl)-<NUM>,<NUM>,<NUM>-oxadiazol-<NUM>-yl) methanamine hydrochloride (<NUM>, <NUM> mmol) in DIPEA (<NUM>, <NUM> mmol) and <NUM>,<NUM>-dioxane (<NUM>) were heated in a microwave reactor at <NUM> for <NUM> hours. The resulting mixture was cooled to RT, diluted with EtOAc (<NUM>) and washed with a saturated aqueous sodium chloride solution. The organic phases were passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by preparative HPLC to afford the title compound as an off white solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (dd, J = <NUM>, <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM>-<NUM> (m, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

The following compound reported in the table below was prepared according to the procedure described for the preparation of <NUM>-(<NUM>-Methylthiazol-<NUM>-yl)-<NUM>-((tetrahydro-<NUM>H-pyran-<NUM>-yl)methyl)-N-((<NUM>-(trifluoromethyl)-<NUM>,<NUM>,<NUM>-oxadiazol-<NUM>-yl)methyl)phthalazin-<NUM>-amine.

Nitrogen was bubbled for <NUM> minutes through a suspension of <NUM>-bromo-<NUM>-cyclopropylphthalazin-<NUM>-ol (Intermediate <NUM>) (<NUM>, <NUM> mmol), <NUM>-methyl-<NUM>-(<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>-dioxaborolan-<NUM>-yl)-<NUM>H-pyrazole (<NUM>, <NUM> mmol), cesium carbonate (<NUM>, <NUM> mmol), Pd(dppf)Cl<NUM> (<NUM>, <NUM> mmol) in <NUM>,<NUM>-dioxane (<NUM>) and water (<NUM>). The resulting mixture was stirred at <NUM> for <NUM> hours. The reaction mixture was cooled to RT. The reaction was partitioned between water (<NUM>) and EtOAc (<NUM>). The aqueous layer was extracted with EtOAc (<NUM> × <NUM>). The organic phases were combined, passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by chromatography on silica gel eluting with <NUM> - <NUM>% MeOH in DCM to afford the title compound as a beige solid (<NUM>, <NUM>%). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

A mixture of <NUM>-cyclopropyl-<NUM>-(<NUM>-methyl-<NUM>H-pyrazol-<NUM>-yl)phthalazin-<NUM>-ol (<NUM>, <NUM> mmol), phosphorus(V) oxychloride (<NUM>, <NUM> mmol) and <NUM>,<NUM> dichloroethane (<NUM>) was heated at <NUM> under nitrogen for <NUM> hours. The reaction was cooled to RT and concentrated in vacuo. The residue was then partitioned between water and DCM. The aqueous layer was extracted with DCM (<NUM> × <NUM>). The combined organic phases were washed with a saturated aqueous sodium hydrogen carbonate solution, passed through a hydrophobic frit and the solvent was removed in vacuo to afford the title compound as a brown solid (<NUM>, <NUM>%).

A mixture of <NUM>-chloro-<NUM>-cyclopropyl-<NUM>-(<NUM>-methyl-<NUM>H-pyrazol-<NUM>-yl)phthalazine (<NUM>, <NUM> mmol) and neat <NUM>-(<NUM>-methylpyridazin-<NUM>-yl)ethan-<NUM>-amine hydrochloride (<NUM>, <NUM> mmol) was heated in a sealed tube under nitrogen for <NUM> days at <NUM>. The resulting residue was cooled to RT, diluted with EtOAc (<NUM>), washed with saturated aqueous sodium chloride solution. The organic phase was passed through a hydrophobic frit and the solvent was removed in vacuo. The resulting residue was purified by preparative HPLC to afford the title compound as an off-white solid (<NUM>, <NUM>%).

<NUM>H NMR (<NUM>, DMSO): δ <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (s, <NUM>), <NUM> (s, <NUM>), <NUM>-<NUM> (m, <NUM>), <NUM> (d, J = <NUM>, <NUM>), <NUM>-<NUM> (m, <NUM>). LCMS (Method <NUM>): [MH+] = <NUM> at <NUM>.

The following compound reported in the table below was prepared according to the procedure described for the preparation of <NUM>-cyclopropyl-<NUM>-(<NUM>-methyl-<NUM>-pyrazol-<NUM>-yl)-N-(<NUM>-(<NUM>-methyl pyridazin-<NUM>-yl)ethyl)phthalazin-<NUM>-amine.

The following compound reported in the table below were obtained as single isomers by chiral preparative SFC purification of the racemic mixture hereinabove described.

In vitro Electrophysiology Assay for P2X<NUM>.

Cells expressing P2X<NUM> receptors were grown according to standard practice and maintained at <NUM> in a <NUM>% humidified CO<NUM> atmosphere. The cells were seeded into T175 flask <NUM> days prior to the day of the assay and dissociated from the flasks using TrypLE when grown to confluence of <NUM>-<NUM>%. The dissociated cells were resuspended in serum free media at a cell density of <NUM>×<NUM><NUM> cells/ml and loaded onto the Sophion Qube automated patch-clamp system. The extracellular assay buffer contained <NUM> NaCl, <NUM> KCl, <NUM> CaCl<NUM>, <NUM> MgCl<NUM>, <NUM> HEPES, and <NUM> glucose at pH <NUM>. The intracellular assay solution contained <NUM> CsF, <NUM> NaCl, <NUM> EGTA, <NUM> HEPES at pH <NUM>. Agonist stock solutions were prepared in H<NUM>O and diluted in bath solution prior to use. All antagonists were prepared as <NUM> stock solutions in DMSO and diluted in bath solution prior to use. All experiments were performed under the whole-cell patch clamp configuration at room temperature with <NUM> individual cells being voltage clamped at -<NUM> mV simultaneously on the Sophion Qube instrument. Two baseline responses were established with the application of α,β-MeATP (<NUM>), with the subsequent agonist applications being washed out using extracellular assay buffer containing <NUM> U/ml apyrase. Following the second agonist application, antagonist was incubated in the absence of α,β-MeATP for <NUM> minutes. After antagonist preincubation, <NUM> α,β-MeATP and antagonist were co-administered to determine the inhibitory effect of the antagonist. One concentration of an antagonist was assessed against a single cell, with different concentrations of the antagonist applied to other cells on the <NUM> recording substrate. The control P2X<NUM> current amplitude was taken from the peak current amplitude from the second agonist response prior to preincubation with antagonist. The peak P2X<NUM> current amplitude in the presence of antagonist was used to calculate the inhibitory effect at each concentration of the antagonist according to the following equation: <MAT>.

Concentration-response curves were constructed from ten different concentrations with each concentration of antagonist tested on at least two individual cells. The concentration of the antagonist to inhibit P2X<NUM> current by <NUM>% (IC<NUM>) was determined by fitting the data with the following equation: <MAT>.

Where 'a' is minimum response, 'b' is maximum response, 'c' is IC<NUM> and 'd' is Hill slope.

The results for individual compounds are provided below in Table <NUM> and are expressed as range of activity.

wherein the compounds are classified in term of potency with respect to their inhibitory activity on P2X<NUM> according to the following classification criterion: <MAT> <MAT>.

In vitro Electrophysiology Assay for P2X<NUM>/<NUM>.

Representative compounds of the present invention have been also tested for P2X<NUM>/<NUM> receptor.

The same assay protocol was used for the P2X<NUM>/<NUM> assay as the P2X<NUM> assay with two modifications: <NUM>) <NUM> ATP was used as the agonist; and <NUM>) the mean current amplitude was measured seven seconds after the application of agonist.

The results of Table <NUM> indicate that representative compounds of the present invention are selective P2X<NUM> antagonist.

wherein the compounds are classified in term of potency with respect to their inhibitory activity on P2X<NUM> or P2X<NUM>/<NUM> isoforms according to the following classification criterion: <MAT> <MAT> <MAT>.

The activity of comparative Example A as has been tested in the in vitro assay for the determination of activity on P2X<NUM> receptor as described above.

Differently from the compounds of formula (I) of the present invention, the comparative Example A do not show a proper inhibitory activity on P2X<NUM>, in fact the activity on receptor P2X<NUM> expressed as pIC<NUM> is < <NUM>.

Claim 1:
A compound of formula (I)
<CHM>
wherein
Z is selected from the group consisting of (<NUM>-<NUM> membered)-heteroaryl and aryl, wherein any of such heteroaryl and aryl may be optionally substituted by one or more groups selected from (C<NUM>-C<NUM>)alkyl- and halo;
R<NUM> is H or (C<NUM>-C<NUM>)alkyl;
R<NUM> is selected from the group consisting of heteroaryl and (C<NUM>-C<NUM>)cycloalkyl-, wherein any of such heteroaryl may be optionally substituted by one or more groups selected from (C<NUM>-C<NUM>)alkyl, (C<NUM>-C<NUM>)haloalkyl and halo;
R<NUM> is H or (C<NUM>-C<NUM>)alkyl;
Y is selected from the group consisting of H, (C<NUM>-C<NUM>)alkyl-, (C<NUM>-C<NUM>)cycloalkyl-, (C<NUM>-C<NUM>)heterocycloalkyl, (C<NUM>-C<NUM>)heterocycloalkyl-(C<NUM>-C<NUM>)alkyl-.