RU2818783C2 - Gpr6 tetrahydropyridopyrazine modulators - Google Patents

Abstract

FIELD: pharmaceutics.

SUBSTANCE: invention relates to a compound of formula 1 or a pharmaceutically acceptable salt thereof, which are G-protein coupled receptor 6 (GPR6) modulators. Invention also relates to a pharmaceutical composition, a kit, a dosage form containing said compound, a method of treating using the same and using it for preparing a drug for treating a disease, disorder or condition associated with GPR6.

EFFECT: tetrahydropyridopyrazine GPR6 modulators are disclosed.

40 cl, 2 tbl, 1 dwg, 1 ex

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/520,430, filed June 15, 2017; US Provisional Patent Application No. 62/591,247, filed November 28, 2017; US Provisional Patent Application No. 62/649856, filed March 29, 2018; and US Provisional Patent Application No. 62/672261, filed May 16, 2018; the contents of each of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to tetrahydropyridopyrazine derivatives that are G protein-coupled receptor 6 (GPR6) modulators, pharmaceutical compositions containing them, and their use for the treatment of diseases, disorders and conditions associated with GPR6.

BACKGROUND OF THE ART

GPR6 is a member of the G protein-coupled receptor (GPCR) family of transmembrane receptors. GPR6 signaling occurs through the G protein (Gs) pathway. It is highly expressed in the central nervous system (CNS), particularly in medium spiny neurons (MSNs) in the striatum, and minimally expressed in peripheral tissues. The main targets of dopaminergic innervation of the striatum are in the SCN of the striatopallidal (indirect) and striatonigral (direct) output pathways. SSNs of direct output pathways express dopamine D1 receptors, while SSNs of indirect pathways express D2 receptors. GPR6 is abundant in striatal SSNs expressing the D2 receptor, in which GPR6 activity increases the level of the intracellular second messenger cAMP, which has a function opposite to D2 receptor signaling. Antagonism or inverse agonism of Gs-coupled GPR6 lowers cAMP levels in the SSN and thus provides a functional alternative to dopamine-mediated D2 receptor activation.

Published international patent application WO 2015/095728A1, the contents of which are incorporated herein by reference in their entirety, discloses several tetrahydropyridopyrazine derivatives that are GPR6 modulators. Said compounds include (S)-1-(2-(4-(2,4-difluorophenoxy)-piperidin-1-yl)-3-((tetrahydrofuran-3-yl)amino)-7,8-dihydropyrido[3 ,4-b]pyrazin-6(5H)-yl)ethan-1-one (“compound A”). Although Compound A is a potentially effective GPR6 modulator, it has a suboptimal safety margin associated with inhibition of hERG (human ether-a-go-go-related gene) activity. See, for example, X. Yao et al., British Journal of Pharmacology (2008) 154:1446-56. hERG inhibition is one of the factors associated with possible QT prolongation and cardiac arrhythmia.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a tetrahydropyridopyrazine derivative and pharmaceutical compositions containing the same. The tetrahydropyridopyrazine derivative is a GPR6 modulator and can be used to treat diseases, disorders and conditions associated with GPR6, including neurological disorders such as Parkinson's disease.

According to one aspect of the invention there is provided a compound of formula 1:

or a pharmaceutically acceptable salt thereof. Formula 1 shows the compound (R)-1-(2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-3-((tetrahydrofuran-3-yl)amino)-7,8-dihydropyrido[ 3,4-b]pyrazin-6(5H)-yl)ethan-1-one.

In certain embodiments, the compound or pharmaceutically acceptable salt thereof of Formula 1 has an enantiomeric purity corresponding to an enantiomeric excess (ee) of 20% or greater, 40% ee, 60% ee, 80% ee. , 90% e.i., 98% e.i., 99% e.i. or 100% e.i. In certain embodiments, the compound is present in free form.

According to a further aspect of the invention, there is provided a pharmaceutical composition that contains a compound of Formula 1 or a pharmaceutically acceptable salt thereof, such as those described herein; and a pharmaceutically acceptable excipient.

According to a further aspect of the invention, there is provided a pharmaceutical composition comprising a compound of Formula 1 or a pharmaceutically acceptable salt thereof, such as those described herein, for use as a drug. In certain embodiments, the pharmaceutical composition is for the treatment of Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression. In certain embodiments, the pharmaceutical composition further comprises amantadine. According to another aspect of the invention, a pharmaceutical composition is provided for use in the treatment of a disease, disorder or condition associated with GPR6.

In various embodiments of the invention described herein, a pharmaceutical composition is provided comprising a compound of Formula 1 or a pharmaceutically acceptable salt thereof, as described herein, and a pharmaceutically acceptable excipient. In certain embodiments, the pharmaceutical composition is for use as a drug. In certain embodiments, the pharmaceutical composition is used to treat a disease, disorder, or condition selected from the group consisting of: Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression.

According to a further aspect of the invention, there is provided the use of a compound of formula 1 or a pharmaceutically acceptable salt thereof for the preparation of a medicament for the treatment of a disease, disorder or condition associated with GPR6. In certain embodiments, the disease, disorder, or condition is selected from the group consisting of: Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety, and depression .

According to a further aspect of the invention, there is provided a method of treating a disease, disorder or condition associated with GPR6, comprising administering to a subject an effective amount of a compound of Formula 1 or a pharmaceutically acceptable salt thereof, such as those described herein. In certain embodiments, a compound of Formula 1 or a pharmaceutically acceptable salt thereof is administered orally.

According to another aspect of the invention, there is provided a method of treating a disease, disorder or condition in a subject, comprising administering to the subject an effective amount of a compound of formula 1 or a pharmaceutically acceptable salt thereof, wherein the disease, disorder or condition is selected from Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction , eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression.

In certain embodiments, a compound of Formula 1 or a pharmaceutically acceptable salt thereof administered in the method described herein is administered at a dose selected from the range of about 0.1 mg/kg to about 1.0 mg/kg or from about 0 .5 mg/kg to approximately 5.0 mg/kg. In certain embodiments, the compound or a pharmaceutically acceptable salt thereof is administered at a dose ranging from about 40 mg/kg to about 60 mg/kg. In certain embodiments, a compound of Formula 1 or a pharmaceutically acceptable salt thereof administered in the method described herein is administered at a dose selected from the group of ranges consisting of: from about 5 mg/kg to about 15 mg/kg, from about 10 mg/kg to about 20 mg/kg, from about 15 mg/kg to about 25 mg/kg, from about 20 to about 30 mg/kg, from about 25 mg/kg to about 35 mg/kg, from about 30 mg/kg to about 40 mg/kg, about 35 mg/kg to about 45 mg/kg, and about 45 mg/kg to about 55 mg/kg. In certain embodiments, the dose is selected from the group of ranges consisting of: about 30 mg/kg to about 40 mg/kg, about 35 mg/kg to about 45 mg/kg, about 40 mg/kg to about 50 mg/kg kg, from about 45 mg/kg to about 55 mg/kg, from about 50 mg/kg to about 60 mg/kg, from about 55 mg/kg to about 65 mg/kg, and from about 60 mg/kg to about 70 mg/kg. In certain embodiments, the dose may be about 50 mg/kg. In certain embodiments, the dose is greater than about 1 mg/kg. In certain embodiments, the dose is about 1 mg/kg. In certain embodiments, the dose is within a range selected from the group consisting of: about 50 mg/kg to about 100 mg/kg, about 100 mg/kg to about 150 mg/kg, about 150 mg/kg to about 200 mg/kg, from about 200 mg/kg to about 250 mg/kg, from about 250 mg/kg to about 350 mg/kg, from about 300 mg/kg to about 350 mg/kg, from about 350 mg/kg to about 400 mg/kg, from about 400 mg/kg to about 450 mg/kg, from about 450 mg/kg to about 500 mg/kg. In certain embodiments, the dose is about 500 mg/kg. Alternatively, the dose is less than 500 mg/kg.

In certain embodiments, the dose is 35 mg/kg. In certain embodiments, the dose is 36 mg/kg. In certain embodiments, the dose is 37 mg/kg. In certain embodiments, the dose is 38 mg/kg. In certain embodiments, the dose is 39 mg/kg. In certain embodiments, the dose is 40 mg/kg. In certain embodiments, the dose is 41 mg/kg. In certain embodiments, the dose is 42 mg/kg. In certain embodiments, the dose is 43 mg/kg. In certain embodiments, the dose is 44 mg/kg. In certain embodiments, the dose is 45 mg/kg. In certain embodiments, the dose is 46 mg/kg. In certain embodiments, the dose is 47 mg/kg. In certain embodiments, the dose is 48 mg/kg. In certain embodiments, the dose is 49 mg/kg. In certain embodiments, the dose is 50 mg/kg. In certain embodiments, the dose is 51 mg/kg. In certain embodiments, the dose is 52 mg/kg. In certain embodiments, the dose is 53 mg/kg. In certain embodiments, the dose is 54 mg/kg. In certain embodiments, the dose is 55 mg/kg. In certain embodiments, the dose is 56 mg/kg. In certain embodiments, the dose is 57 mg/kg. In certain embodiments, the dose is 58 mg/kg. In certain embodiments, the dose is 59 mg/kg. In certain embodiments, the dose is 60 mg/kg. In certain embodiments, the dose is 61 mg/kg. In certain embodiments, the dose is 62 mg/kg. In certain embodiments, the dose is 63 mg/kg. In certain embodiments, the dose is 64 mg/kg. In certain embodiments, the dose is 65 mg/kg. In certain embodiments, the administration step is performed orally.

According to a further aspect of the invention, there is provided a combination therapy comprising administering an effective amount of a pharmaceutical composition; and at least one additional pharmacologically active agent. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: levodopa, a DOPA decarboxylase inhibitor, a dopamine agonist, an anticholinergic agent, a selective monoamine oxidase B inhibitor, and a catechol-O-methyltransferase inhibitor. In other embodiments, the additional pharmacologically active agent is levodopa in combination with a DOPA decarboxylase inhibitor. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: carbidopa; benserazide; methyldopa; α-difluoromethyl-DOPA; 3',4',5,7-tetrahydroxy-8-methoxyisoflavone; apomorphine hydrochloride; bromocriptine; rotigotine; pramipexole; ropinirole; trihexylphenidyl; benztropine mesylate; safinamide; selegiline; rasagiline; entacapone; and tolcapone. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: beta-secretase inhibitors, gamma-secretase inhibitors, HMG-CoA reductase inhibitors, nonsteroidal anti-inflammatory drugs (NSAIDs). In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: apazone, aspirin, celecoxib, diclofenac (with or without misoprostol), diflunisal, etodolac, fenoprofen, flurbiprofen, ibuprofen, indomethacin, ketoprofen, meclofenamate sodium, mefenamic acid , meloxicam, nabumetone, naproxen, oxaprozin, phenylbutazone, piroxicam, choline and magnesium salicylates, salsalate and sulindac. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: donepezil, rivastigmine, memantine, and galantamine. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: sedatives, hypnotics, anxiolytics, antipsychotics, and tranquilizers. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: amitriptyline, amoxapine, aripiprazole, asenapine, bupropion, chlordiazepoxide, citalopram, chlorpromazine, clozapine, desipramine, desvenlafaxine, doxepin, duloxetine, escitalopram, fluoxetine, fluoxetine, haloperidol , iloperidone, imipramine, isoxarboxazid, lamotrigine, levomilnacipran, lurasidone, mirtazapine, nefazodone, nortriptyline, olanzapine, paliperidone, paroxetine, perphenazine, phenelzine, protriptyline, quetiapine, risperidone, safinamide, selegiline, tranylcypromine, , trazodone, trimipramine, venlafaxine, vilazodone , vortioxetine and ziprasidone. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: alprazolam, chlordiazepoxide, clobazepam, clonazepam, clorazepate, diazepam, estazolam, flurazepam, lorazepam, midazolam, oxazepam, prazepam, quazepam, temazepam and triazolam, hydroxyzine, eszopiclone, zaleplon , zolpidem and zopiclone and buspirone. In certain embodiments, the additional pharmacologically active agent is selected from the group consisting of: acetazolamide, carbamazepine, clobazam, clonazepam, eslicarbazepine acetate, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, nitrazepam, oxcarbazepine, perampanel, piracetam, phenobarbital, toina, pregabalin, primidone, retigabine, rufinamide, sodium valproate, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide.

In various embodiments, the present invention provides a method of treating Parkinson's disease in a subject, comprising: administering a pharmaceutical composition, as defined herein, to the subject. In some embodiments, administration of the pharmaceutical composition improves motor symptoms in a subject. In some embodiments, the administration step is administered orally.

In various embodiments, the present invention provides a dosage form of a compound of Formula 1 or a pharmaceutically acceptable salt thereof for oral administration of the compound or a pharmaceutically acceptable salt thereof at a dosage selected from the group of ranges consisting of: about 0.1 mg/kg to about 1 mg/kg .0 mg/kg or from about 0.5 mg/kg to about 5.0 mg/kg. In certain embodiments, the compound or a pharmaceutically acceptable salt thereof is administered at a dose ranging from about 40 mg/kg to about 60 mg/kg. In certain embodiments, a compound of Formula 1 or a pharmaceutically acceptable salt thereof is administered at a dose selected from the group of ranges consisting of: about 5 mg/kg to about 15 mg/kg, about 10 mg/kg to about 20 mg/kg, from about 15 mg/kg to about 25 mg/kg, from about 20 to about 30 mg/kg, from about 25 mg/kg to about 35 mg/kg, from about 30 mg/kg to about 40 mg/kg, from about 35 mg/kg to about 45 mg/kg and from about 45 mg/kg to about 55 mg/kg. In certain embodiments, the dose is selected from the group of ranges consisting of: about 30 mg/kg to about 40 mg/kg, about 35 mg/kg to about 45 mg/kg, about 40 mg/kg to about 50 mg/kg kg, from about 45 mg/kg to about 55 mg/kg, from about 50 mg/kg to about 60 mg/kg, from about 55 mg/kg to about 65 mg/kg, and from about 60 mg/kg to about 70 mg/kg. In certain embodiments, the dose may be about 50 mg/kg. In certain embodiments, the dose is greater than about 1 mg/kg. In certain embodiments, the dose is about 1 mg/kg. In certain embodiments, the dose is in a range selected from the group consisting of: about 50 mg/kg to about 100 mg/kg, about 100 mg/kg to about 150 mg/kg, about 150 mg/kg to about 200 mg/kg, from about 200 mg/kg to about 250 mg/kg, from about 250 mg/kg to about 350 mg/kg, from about 300 mg/kg to about 350 mg/kg, from about 350 mg/kg to about 400 mg/kg, from about 400 mg/kg to about 450 mg/kg, from about 450 mg/kg to about 500 mg/kg. In certain embodiments, the dose is about 500 mg/kg. Alternatively, the dose is less than 500 mg/kg.

In certain embodiments, the dose is 35 mg/kg. In certain embodiments, the dose is 36 mg/kg. In certain embodiments, the dose is 37 mg/kg. In certain embodiments, the dose is 38 mg/kg. In certain embodiments, the dose is 39 mg/kg. In certain embodiments, the dose is 40 mg/kg. In certain embodiments, the dose is 41 mg/kg. In certain embodiments, the dose is 42 mg/kg. In certain embodiments, the dose is 43 mg/kg. In certain embodiments, the dose is 44 mg/kg. In certain embodiments, the dose is 45 mg/kg. In certain embodiments, the dose is 46 mg/kg. In certain embodiments, the dose is 47 mg/kg. In certain embodiments, the dose is 48 mg/kg. In certain embodiments, the dose is 49 mg/kg. In certain embodiments, the dose is 50 mg/kg. In certain embodiments, the dose is 51 mg/kg. In certain embodiments, the dose is 52 mg/kg. In certain embodiments, the dose is 53 mg/kg. In certain embodiments, the dose is 54 mg/kg. In certain embodiments, the dose is 55 mg/kg. In certain embodiments, the dose is 56 mg/kg. In certain embodiments, the dose is 57 mg/kg. In certain embodiments, the dose is 58 mg/kg. In certain embodiments, the dose is 59 mg/kg. In certain embodiments, the dose is 60 mg/kg. In certain embodiments, the dose is 61 mg/kg. In certain embodiments, the dose is 62 mg/kg. In certain embodiments, the dose is 63 mg/kg. In certain embodiments, the dose is 64 mg/kg. In certain embodiments, the dose is 65 mg/kg.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages will become apparent from the following description of specific embodiments of the invention illustrated in the accompanying drawings. The drawings are not necessarily to scale; rather, the emphasis is on illustrating the principles underlying the various embodiments of the invention.

Figure 1 is a graph showing the effect of treatment in a 6-hydroxydopamine (6-OHDA) model of Parkinson's disease.

DETAILED DESCRIPTION OF THE INVENTION

This application is related to WO 2015/095728, the contents of which are incorporated herein by reference in their entirety.

I. DEFINITIONS

Unless otherwise specified, the definitions below apply to the present invention.

“About” or “approximately” when used to describe a numerical variable being measured refers to the specified value of the variable and to all values of the variable within the experimental error for the given value or within ±10 percent of the specified value, whichever error is greater.

"Enantiomeric excess" or "e.i." refers to the excess of one enantiomer over another, expressed as a percentage of the whole, and is a measure of the enantiomeric (chiral) purity of a sample containing the enantiomer. For example, if a sample contains an excess of the R-enantiomer, then the e.i. can be defined using the expression

where A _R and A _S represent the amounts of R and S enantiomers in the sample.

"Combination therapy" refers to an approach for treating a disease, disorder or condition that includes one or more therapeutic agents. For example, therapeutic agents may include more than one (one) pharmaceutical composition or pharmaceutically active agent, or a combination thereof. The therapeutic agents may be administered simultaneously, sequentially, or in any order. They can be administered in different dosages, with different frequency of administration or in different ways, which are suitable. The molar ratio of therapeutic agents is not limited in any particular way.

“Motor symptoms” refers to the decrease in a subject's activity that occurs in a GPR6-related disease, disorder, or condition, such as Parkinson's disease.

“Substantially pure enantiomer” and its variants refer to the enantiomer that is present in the sample with 90% ee. or more.

“Pure enantiomer” and its variants refer to the enantiomer that is present in the sample at 98% ee. or more.

"Subject" refers to a mammal, including a human.

"Pharmaceutically acceptable" substances refer to substances that are suitable for administration to subjects.

“Treatment” refers to the reversal, amelioration, suppression of progression, or prevention of the disease, disorder, or condition to which that term refers, or the reversal, amelioration, suppression of progression, or prevention of one or more symptoms of a specified disease, disorder, or condition.

"Method of treatment" refers to the implementation of a "treatment" such as defined immediately above.

“Drug”, “drug substance”, “active pharmaceutical ingredient”, etc. refer to a compound (eg, a compound of Formula 1) that can be used to treat a subject in need of treatment.

An "effective amount" of a drug, a "therapeutically effective amount" of a drug, etc. refer to the amount of drug that can be used to treat a subject, and may depend on the body weight and age of the subject and the route of administration, among other factors.

“Excipient” refers to any diluent or excipient for a drug product.

"Pharmaceutical composition" refers to a combination of one or more drug substances and one or more excipients.

“Drug product”, “pharmaceutical dosage form”, “dosage form”, “final dosage form”, etc. refer to a pharmaceutical composition suitable for treating a subject in need of treatment, and may generally take the form of tablets, capsules, unit packets containing powder or granules, liquid solutions or suspensions, patches, films, etc.

“GPR6-related condition” and similar phrases refer to a disease, disorder, or condition of a subject in which modulation of GPR6, including antagonism or inverse agonism of GPR6, can provide therapeutic or prophylactic benefits.

The following abbreviations may be used in the description: Ac (acetyl); ACN (acetonitrile); AIBN (azo-bis-isobutyronitrile); API (active pharmaceutical ingredient); aq. (water); BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl); Boc (tert-butoxycarbonyl); Cbz (carbobenzyloxy); dba (dibenzylideneacetone); DCC (1,3-dicyclohexylcarbodiimide); DCE (1,1-dichloroethane); DCM (dichloromethane); DIPEA (N,N-diisopropylethylamine, Huenig's base); DMA (N,N-dimethylacetamide); DMAP (4-dimethylaminopyridine); DME (1,2-dimethoxyethane); DMF (N,N-dimethylformamide); DMSO (dimethyl sulfoxide); dppf (1,1′-bis(diphenylphosphino)ferrocene); DTT (dithiothreitol); EC ₅₀ (effective concentration providing half-maximal response); EDA (ethoxylated dodecyl alcohol, BRIJ® 35); EDC (N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide); EDTA (ethylenediaminetetraacetic acid); e.i. (enantiomeric excess); eq. (equivalents); Et (ethyl); Et ₃ N (triethylamine); EtOAc (ethyl acetate); EtOH (ethanol); HATU (2-(3H-[1,2,3]triazolo[4,5-b]pyridin-3-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (V)); HEPES (4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid); HOAc (acetic acid); HOBt (1H-benzo[d][1,2,3]triazol-1-ol); IC ₅₀ (concentration providing 50% inhibition); IPA (isopropanol); iPrOAc (isopropyl acetate); IPE (isopropyl ether); Ki (inhibition constant; the concentration of a competitive ligand in a competition assay at which it occupies 50% of the receptors in the absence of the test ligand); LDA (lithium diisopropylamide); LiHMDS (lithium bis(trimethylsilyl)amide); mCPBA (m-chloroperoxybenzoic acid); Me (methyl); MeOH (methanol); MTBE (methyl tert-butyl ether); T _pl (melting temperature); NaOt-Bu (sodium tert-butoxide); NMM (N-methylmorpholine); NMP (N-methyl-pyrrolidone); OTf (triflate); PE (petroleum ether); Ph (phenyl); pEC ₅₀ (-log ₁₀ (EC ₅₀ ), where EC ₅₀ is in units of molarity (M)); pIC ₅₀ (-log ₁₀ (IC ₅₀ ), where IC ₅₀ is in units of molarity (M)); Pr (drank); c-Pr (cyclopropyl), i-Pr (isopropyl); PTFE (polytetrafluoroethylene); CT (room temperature approximately 20°C to 25°C); T3P (2,4,6-tripropyl-1,3,5,2,4,6-trioxytriphosphinane 2,4,6-trioxide); TCEP (tris(2-carboxyethyl)phosphine); TFA (trifluoroacetic acid); TFUCA (2,2,2-trifluoroacetic acid anhydride); THF (tetrahydrofuran); TMEDA (N ¹ , N ¹ , N ² , N ² -tetramethylethane-1,2-diamine); TMS (trimethylsilyl); and Tris buffer (2-amino-2-hydroxymethylpropane-1,3-diol buffer).

II. COMPOSITIONS ACCORDING TO THE INVENTION

As described below, the present invention relates to a compound of Formula 1 and pharmaceutically acceptable salts thereof. The present invention also relates to materials and methods for preparing a compound of formula 1, to pharmaceutical compositions containing the same, and to the use of a compound of formula 1 and pharmaceutically acceptable salts thereof (optionally in combination with other pharmacologically active agents) for the treatment of diseases, disorders or conditions of the central nervous system, including Parkinson's disease, and other diseases, disorders or conditions associated with GPR6.

The compound of formula 1 can exist in the form of a salt, complex, solvate, hydrate and liquid crystal. Likewise, a salt of a compound of formula 1 may exist as a complex, solvate, hydrate or liquid crystal.

The compound of formula 1 can form a pharmaceutically acceptable salt. Such salts include acid addition salts (including diacids) and base salts. Pharmaceutically acceptable acid addition salts may include salts derived from inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid and phosphoric acids, as well as non-toxic salts derived from organic acids, such as aliphatic mono- and dicarboxylic acids, phenyl-substituted alkanoic acids, hydroxyalkanoic acids, alkanedioic acids, aromatic acids, aliphatic and aromatic sulfonic acids, etc. Said salts may include acetate, adipate, aspartate, benzoate, besylate, bicarbonate, carbonate, bisulfate, sulfate, borate, camsylate, citrate, cyclamate, edisylate, esylate, formate, fumarate, gluceptate, gluconate, glucuronate, hexafluorophosphate, solid, hydrochloride/ chloride, hydrobromide/bromide, hydroiodide/iodide, isethionate, lactate, malate, maleate, malonate, mesylate, methylsulfonate, naphthylate, 2-napsylate, nicotinate, nitrate, orotate, oxalate, palmitate, pamoate, phosphate, hydrogen phosphate, dihydrogen phosphate, pie lootamate, sugar, stearate, succinate, tannate, tartrate, tosylate, trifluoroacetate and xinofoate salts.

Pharmaceutically acceptable base salts may include salts derived from bases, including metal cations such as alkali or alkaline earth metal cations, as well as amines. Examples of suitable metal cations may include sodium, potassium, magnesium, calcium, zinc and aluminum. Examples of suitable amines may include arginine, N,N'-dibenzylethylenediamine, chloroprocaine, choline, diethylamine, diethanolamine, dicyclohexylamine, ethylenediamine, glycine, lysine, N-methylglucamine, olamine, 2-amino-2-hydroxymethylpropane-1,3-diol and procaine For a discussion of suitable acid and base addition salts, see S. M. Berge et al., J. Pharm. Sci. (1977) 66:1-19; also see Stahl and Wermuth, Handbook of Pharmaceutical Salts: Properties, Selection, and Use (2002); the contents of both of which are incorporated herein by reference in their entirety.

Pharmaceutically acceptable salts can be prepared in a variety of ways. For example, a compound of Formula 1 can be reacted with an appropriate acid or base to produce the desired salt. Alternatively, a precursor of a compound of Formula 1 may be reacted with an acid or base to remove acid- or base-labile protecting groups or to open a lactone or lactam group in the precursor. In addition, a salt of a compound of Formula 1 can be converted to another salt (or free form) by treatment with an appropriate acid or base or contacting an ion exchange resin. After the reaction, the salt can be isolated by filtration if it precipitates from solution, or by evaporation to isolate the salt. The degree of ionization of a salt can vary from completely ionized to practically non-ionized.

The compound of formula 1 can exist in a variety of solid states ranging from completely amorphous to completely crystalline. The term "amorphous" refers to a state of material in which there is no long-range order at the molecular level and, depending on temperature, the physical properties of a solid or liquid can appear. Typically, characteristic X-ray diffraction patterns cannot be obtained for such materials and, although they have the properties of a solid, they are more formally described as a liquid. When heated, the properties of a solid change to those of a liquid, which is characterized by a typical second-order phase transition (“glass transition”). The term "crystalline" refers to a solid phase in which the material has a regularly ordered internal structure at the molecular level and for which a characteristic X-ray diffraction pattern with pronounced peaks can be obtained. These materials, when heated sufficiently, also have the properties of a liquid, but the change in shape from solid to liquid is characterized by a typical first-order phase transition (“melting point”).

The compound of formula 1 may also exist in unsolvated and solvated forms. The term "solvate" describes a molecular complex containing a compound and one or more molecules of a pharmaceutically acceptable solvent (eg, ethanol). The term "hydrate" is a solvate in which the solvent is water. Pharmaceutically acceptable solvates include solvates in which the solvent may be substituted with isotopes (eg, D ₂ O, acetone-d ₆ , DMSO-d ₆ ).

The currently accepted classification system for solvates and hydrates of organic compounds distinguishes between island-type solvates and hydrates, channel solvates and hydrates, and coordination solvates and hydrates containing metal-ion bonds. See, for example, K. R. Morris (H. G. Brittain, ed.) Polymorphism in Pharmaceutical Solids (1995), the contents of which are incorporated herein by reference in their entirety. Island solvates and hydrates are forms in which solvent molecules (such as water) are isolated from direct contact with each other by molecules of an organic compound. In channel solvates, the solvent molecules are located in channels in the crystal lattice, in which they are adjacent to other solvent molecules. In coordination solvates, solvent molecules are bound to a metal ion.

If the solvent or water is tightly bound, then the complex has a well-defined stoichiometry, regardless of humidity. However, if the solvent or water is weakly bound, as in the case of channel solvates and hygroscopic compounds, then the water or solvent content depends on the humidity and drying conditions. In these cases, nonstoichiometric solvates are usually observed.

The compound of formula 1 may also exist as a multicomponent complex (other than salts and solvates) in which the compound (drug) and at least one other component are present in stoichiometric or non-stoichiometric amounts. Complexes of this type include clathrates (drug-host inclusion complexes) and mixed crystals. The latter are generally defined as crystalline complexes of neutral molecular components that are associated with each other through non-covalent interactions, but can also represent complexes of a neutral molecule with a salt. Mixed crystals can be obtained by melt crystallization, recrystallization from solvents, or by physically grinding the components together. See, for example, O. Almarsson and M. J. Zaworotko, Chem. Commun. (2004) 17:1889-1896, the contents of which are incorporated herein by reference in their entirety. For a general overview of multicomponent complexes, see J. K. Haleblian, J. Pharm. Sci. (1975) 64(8):1269-88, the contents of which are incorporated herein by reference in their entirety.

When exposed to suitable conditions, the compound of formula 1 can exist in a mesomorphic state (mesophase or liquid crystal). The mesomorphic state is between the true crystalline state and the true liquid state (melt or solution). Mesomorphism resulting from a change in temperature is called "thermotropic", while mesomorphism resulting from the addition of a second component such as water or another solvent is called "lyotropic". Compounds that can form lyotropic mesophases are called "amphiphilic" and include molecules containing a polar ionic moiety (such as -COOˉNa ⁺ , -COOˉK ⁺ , -SO ₃ ˉNa ⁺ ) or a polar nonionic moiety (such as -NˉN ⁺ (CH ₃ ) ₃ ). See, for example, N.H. Hartshorne and A. Stuart, Crystals and the Polarizing Microscope (4th ed., 1970), the contents of which are incorporated herein by reference in their entirety.

The compound of formula 1 may exist as polymorphs, may contain isotopic tags, may be formed by administration of a prodrug, or may form metabolites after administration.

“Prodrugs” refer to compounds having little or no pharmacological activity that can, through in vivo metabolism, undergo conversion to compounds having the desired pharmacological activity. Prodrugs can be prepared by replacing the appropriate functional groups present in pharmacologically active compounds with “pro-moieties” such as those described, for example, in H. Bundgaar, Design of Prodrugs (1985), the contents of which are incorporated herein in its entirety via link. Examples of prodrugs include ester, ether or amide derivatives of compounds of formula 1 containing carboxyl, hydroxy or amino functional groups, respectively. For additional discussion of prodrugs, see, for example, T. Higuchi and V. Stella, “Pro-drugs as Novel Delivery Systems,” ACS Symposium Series 14 (1975), and E. B. Roche, eds., Bioreversible Carriers in Drug Design (1987), the contents of each of which are incorporated herein by reference in their entirety.

"Metabolites" refer to compounds formed in vivo after administration of pharmacologically active compounds. Examples include hydroxymethyl, hydroxy, secondary amino, primary amino, phenolic and carboxyl derivatives of compounds of formula 1 containing methyl, alkoxy, tertiary amino, secondary amino, phenyl and amide groups, respectively.

The compounds of formula 1 may contain isotopic forms in which at least one atom is replaced by an atom having the same atomic number, the atomic mass of which differs from the atomic mass usually found in nature. Isotopes suitable for inclusion in the compound of formula 1 include, for example, isotopes of hydrogen such as ² H and ³ H; carbon isotopes such as ¹¹ C, ¹³ C and ¹⁴ C; nitrogen isotopes such as ¹³ N and ¹⁵ N; oxygen isotopes such as ¹⁵ O, ¹⁷ O and ¹⁸ O; and fluorine isotopes such as ¹⁸ F. The use of isotopic forms (eg, deuterated, ² H) may provide certain therapeutic benefits based on increased metabolic stability, such as increased in vivo half-life or reduced dosage requirements. In addition, certain isotopic forms of the disclosed compounds may include a radioactive isotope (eg, tritium ³ H, or ¹⁴ C), which can be used in drug and/or substrate tissue distribution studies. Substitution with positron-emitting isotopes such as ¹¹ C, ¹⁸ F, ¹⁵ O and ¹³ N can be used in positron emission tomography (PET) studies to study the extent of receptor occupancy by a substrate. Isotopically labeled compounds can be prepared by methods similar to those described in various sections of the invention, using an appropriate isotopically labeled reagent instead of an unlabeled reagent.

III. METHODS FOR OBTAINING THE COMPOSITION ACCORDING TO THE INVENTION

The compound of formula 1 can be prepared by the methods described below. Some diagrams and examples may omit detailed descriptions of traditional reactions, including oxidation, reduction, etc., separation methods (extraction, evaporation, precipitation, chromatography, filtration, powdering, crystallization, etc.) and analytical methods, which are known to those skilled in the field of organic chemistry. Detailed descriptions of these reactions and methods can be found in various works, including Richard Larock, Comprehensive Organic Transformations (1999), and the multi-volume series edited by Michael B. Smith and others, Compendium of Organic Synthetic Methods (1974 et seq.), the contents of each of which is incorporated herein by reference in its entirety. Starting materials and reagents can be obtained from commercial sources or by methods described in the literature. In some reaction schemes, by-products of chemical reactions may be omitted (for example, alcohol in the hydrolysis of an ester, CO ₂ in the decarboxylation of a diacid, etc.). Additionally, in some cases, the intermediates produced in the reaction can be used in subsequent steps without undergoing isolation or purification (ie, in situ).

In some reaction schemes and in the examples below, certain compounds can be prepared using protecting groups that prevent unwanted chemical reactions at sites that might otherwise react. Protecting groups can also be used to increase solubility or otherwise modify the physical properties of a compound. For a discussion of the strategy for using protecting groups, a description of materials and methods for introducing and removing protecting groups, and a summary of suitable protecting groups for commonly used functional groups, including amines, carboxylic acids, alcohols, ketones, aldehydes, etc., see TW Greene and P. G. Wuts; Protective Groups in Organic Chemistry; ^3rd edition; John Wiley & Sons, Inc.; New York (1999), and P. Kocienski, Protective Groups, Georg Thieme, Stuttgart (2000), the contents of each of which are incorporated herein in their entirety by reference.

In general, the chemical reactions described herein can be carried out using substantially stoichiometric amounts of reactants, although some reactions may be carried out more efficiently by using an excess of one or more reactants. In addition, many of the reactions described herein can be carried out at approximately room temperature (RT) and at ambient pressure, but are subject to reaction kinetics, yield, etc. some reactions can be carried out at elevated pressure or using elevated temperatures (eg, reverse condensation conditions) or reduced temperatures (eg, minus 78 °C to 0 °C). Any reference in the invention and claims to a stoichiometric range, temperature range, pH range, etc., whether the word "range" is used directly or not, also includes the specified endpoints.

Many chemical reactions can also use one or more compatible solvents, which can affect the reaction rate and yield. Depending on the nature of the reagents, one or more solvents may be polar protic solvents (including water), polar aprotic solvents, non-polar solvents, or some combination thereof. Typical solvents include saturated aliphatic hydrocarbons (eg, n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane); aromatic hydrocarbons (eg benzene, toluene, xylenes); halogenated hydrocarbons (eg methylene chloride, chloroform, carbon tetrachloride); aliphatic alcohols (e.g. methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol, 2-methylpropan-1-ol, butan-2-ol, 2-methylpropan-2-ol, pentane -1-ol, 3-methylbutan-1-ol, hexan-1-ol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2 -(2-butoxyethoxy)ethanol); ethers (e.g. diethyl ether, diisopropyl ether, dibutyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-methoxy-2-(2-methoxyethoxy)ethane, 1-ethoxy-2-(2-ethoxyethoxy) ethane, tetrahydrofuran, 1,4-dioxane); ketones (eg acetone, methyl ethyl ketone); esters (methyl acetate, ethyl acetate); nitrogen-containing solvents (eg formamide, N,N-dimethylformamide, acetonitrile, N-methylpyrrolidone, pyridine, quinoline, nitrobenzene); sulfur-containing solvents (eg carbon disulfide, dimethyl sulfoxide, tetrahydrothiophene-1,1-dioxide); and phosphorus-containing solvents (eg hexamethylphosphorus triamide).

IV. COMPOSITION AND INTRODUCTION

It is necessary to evaluate the biopharmaceutical properties of the compound of formula 1, including its pharmaceutically acceptable complexes, salts, solvates and hydrates, such as solubility and solution stability at different pH, permeability, etc., to select the appropriate dosage form and route of administration. The compound intended for pharmaceutical use can be administered as a crystalline or amorphous product, and can be prepared, for example, in the form of solid compressed forms, powders or films, by methods such as precipitation, crystallization, lyophilization, spray drying, evaporation drying, microwave drying or radiofrequency drying.

A compound of formula 1 can be administered alone or in combination with one or more pharmacologically active compounds. In general, one or more of these compounds is administered as a pharmaceutical composition together with one or more pharmaceutically acceptable excipients. The choice of excipients depends on the specific route of administration, the effect of the excipient on solubility and stability, and the nature of the dosage form, among other factors. Suitable pharmaceutical compositions and methods for their preparation can be found, for example, in A. R. Gennaro (ed.), Remington: The Science and Practice of Pharmacy (20th ed., 2000).

The compound of formula 1 can be administered orally. Oral administration may involve ingestion, in which case the compound enters the bloodstream through the gastrointestinal tract. Alternatively or in addition, oral administration may include transmucosal administration (eg, buccal, sublingual, supraglottic administration), whereby the compound enters the bloodstream through the oral mucosa.

Formulations suitable for oral administration, including solid, semi-solid and liquid systems such as tablets; soft or hard capsules containing dispersed materials consisting of many individual particles or nanoparticles, liquids or powders; lozenges, which may contain liquid filler; chewable lollipops; gels; rapidly dispersing dosage forms; films; vaginal suppositories; sprayable compounds; and buccal or mucoadhesive patches. Liquid formulations include suspensions, solutions, syrups and elixirs. These compositions may be used as fillers in soft or hard capsules (derived, for example, from gelatin or hydroxypropyl methylcellulose) and typically contain a carrier (for example, water, ethanol, polyethylene glycol, propylene glycol, methylcellulose or a suitable oil) and one or more emulsifiers , suspending agents, or both. Liquid formulations can also be prepared by redissolving a solid (for example, from a portion packet).

The compound of formula 1 can also be used in rapidly dissolving, rapidly disintegrating dosage forms, such as those described in Liang and Chen, Expert Opinion in Therapeutic Patents (2001) 11(6):981-986, the contents of which are incorporated herein in their entirety by links.

For tablet dosage forms, depending on the dose, the active pharmaceutical ingredient (API) may comprise from about 1 wt% to about 80 wt% of the dosage form, or more commonly from about 5 wt% to about 60 wt% of the dosage form. In addition to the API, tablets may include one or more disintegrants, binders, diluents, surfactants, glidants, lubricants, antioxidants, colorants, flavoring agents, preservatives and flavoring agents. Examples of disintegrants include sodium starch glycolate, sodium carboxymethylcellulose, calcium carboxymethylcellulose, croscarmellose sodium, crospovidone, polyvinylpyrrolidone, methylcellulose, microcrystalline cellulose, C _1-6 alkyl-substituted hydroxypropylcellulose, starch, pregelatinized starch and sodium alginate. In general, the disintegrant constitutes from about 1 wt.% to about 25 wt.% or from about 5 wt.% to about 20 wt.% of the dosage form.

Binders are generally used to impart cohesive properties to the tablet formulation. Suitable binders include microcrystalline cellulose, gelatin, sugars, polyethylene glycol, natural and synthetic gums, polyvinylpyrrolidone, pregelatinized starch, hydroxypropylcellulose and hydroxypropylmethylcellulose. The tablets may also contain diluents such as lactose (monohydrate, spray-dried monohydrate, anhydrous), mannitol, xylitol, dextrose, sucrose, sorbitol, microcrystalline cellulose, starch and dibasic calcium phosphate dihydrate.

Tablets may also include surfactants such as sodium lauryl sulfate and polysorbate 80, and glidants such as silicon dioxide and talc. Surfactants, if present, may comprise from about 0.2% by weight to about 5% by weight of the tablet, and glidants may comprise from about 0.2% by weight to about 1% by weight of the tablet.

The tablets may also contain lubricants such as magnesium stearate, calcium stearate, zinc stearate, sodium stearyl fumarate, and mixtures of magnesium stearate and sodium lauryl sulfate. Lubricants may comprise from about 0.25 wt% to about 10 wt% or from about 0.5 wt% to about 3 wt% of the tablet.

The tablet mixtures can be compressed directly or using compression rollers to produce tablets. Alternatively, the tablet mixtures, or portions of the mixtures, may be wet, dry or melt granulated, melt frozen, or extruded prior to tablet production. If desired, one or more components may be brought to the desired size by sieving or grinding, or both, before mixing. The final dosage form may contain one or more layers and may be coated, uncoated, or encapsulated. Typical tablets may contain up to about 80 wt.% API, from about 10 wt.% to about 90 wt.% binder, from about 0 wt.% to about 85 wt.% diluent, from about 2 wt.% to about 10 wt.% disintegrant and from about 0.25 wt.% to about 10 wt.% lubricant. For a discussion of mixing, granulating, grinding, sieving, tableting, coating, and alternative methods for preparing medicinal products, see A. R. Gennaro (ed.), Remington: The Science and Practice of Pharmacy (20th ed., 2000); H. A. Lieberman et al. (Ed.), Pharmaceutical Dosage Forms: Tablets, Vol. 1-3 (2nd ed., 1990); and D. K. Parikh & C. K. Parikh, Handbook of Pharmaceutical Granulation Technology, Vol. 81 (1997), the contents of each of which are incorporated herein by reference in their entirety.

Oral films for human or veterinary use are soft, water-soluble or water-swellable thin film dosage forms that can dissolve rapidly or have mucoadhesive properties. In addition to the API, a typical film includes one or more film-forming polymers, binders, solvents, wetting agents, plasticizers, stabilizers or emulsifiers, viscosity modifying agents, and solvents. Other film ingredients may include antioxidants, colorants, flavoring agents and enhancers, preservatives, saliva stimulants, cooling agents, co-solvents (including oils), emollients, bulking agents, antifoaming agents, surfactants and flavor correctors. . Some components of the composition can perform more than one function.

In addition to administration requirements, the amount of API in the film may depend on its solubility. If the API is water soluble, it typically constitutes from about 1 wt.% to about 80 wt.% of the non-solvent components (solutes) in the film or from about 20 wt.% to about 50 wt.% dissolved substances in the film. The less soluble API may have a higher content in the composition, typically up to about 88 wt.% of the non-solvent components of the film.

The film-forming polymer may be selected from natural polysaccharides, proteins, or synthetic hydrocolloids and typically constitutes from about 0.01 wt.% to about 99 wt.% or from about 30 wt.% to about 80 wt.% of the film.

Film dosage forms are typically prepared by evaporation drying of thin aqueous films deposited on an easily peelable support or paper, which can be carried out in a drying oven or tunnel (eg, a combination coater-dryer), lyophilization equipment, or vacuum oven.

Suitable solid formulations for oral administration may include immediate release formulations and modified release formulations. Modified release formulations include delayed, sustained, pulsatile, controlled, targeted and programmed release formulations. For a general description of suitable modified release formulations, see US Pat. No. 6,106,864, the contents of which are incorporated herein by reference in their entirety. For a detailed description of other suitable release technologies, such as the use of high energy dispersions and osmotic and coated particles, see Verma et al, Pharmaceutical Technology On-line (2001) 25(2):1-14, the contents of which are incorporated herein at in its entirety by reference.

The compound of Formula 1 can also be administered directly into the bloodstream, into a muscle, or into an internal organ of a subject. Suitable routes of parenteral administration include intravenous, intraarterial, intraperitoneal, intrathecal, intraventricular, intraurethral, intrasternal, intracranial, intramuscular, intraarticular and subcutaneous administration. Suitable devices for parenteral administration include needle injection devices, including microneedle injection devices, needleless injection devices, and infusion devices.

Parenteral formulations are typically aqueous solutions that may contain excipients such as salts, carbohydrates and buffering agents (eg, pH from about 3 to about 9). For some applications, however, the compound of Formula 1 may be more effectively prepared as a sterile non-aqueous solution or in a dried form for use with a suitable vehicle, such as sterile pyrogen-free water. Parenteral formulations can be easily prepared under sterile conditions (eg, by lyophilization) by standard pharmaceutical methods.

The solubility of compounds used in the preparation of parenteral solutions can be increased by appropriate formulation methods, such as the addition of solubility enhancing agents. Formulations for parenteral administration may be formulated as immediate or modified release. Modified release formulations include delayed, sustained, pulsatile, controlled, targeted and programmed release formulations. Thus, the compound of formula 1 can be prepared as a suspension, solid, semi-solid or thixotropic liquid for administration as an implantable depot providing modified release of the active compound. Examples of these formulations include drug-eluting stents and semi-solid forms and suspensions containing poly(DL-lactic-glycolic) acid (PGLA) microspheres containing drug.

The compound of formula 1 can also be administered topically, intradermally or transdermally to the skin or mucosa. Typical formulations for this purpose include gels, hydrogels, lotions, solutions, creams, ointments, powders, dressings, foams, films, skin patches, implantable capsules, implants, sponges, fiber materials, bandages and microemulsions. Liposomes can also be used. Typical carriers include alcohol, water, mineral oil, liquid petrolatum, white petrolatum, glycerin, polyethylene glycol and propylene glycol. Topical formulations may also include penetration enhancers. See, for example, Finnin and Morgan, J. Pharm. Sci. 88(10):955-958 (1999), the contents of which are incorporated herein in their entirety by reference.

Other means for topical administration include delivery by electroporation, iontophoresis, phonophoresis, sonophoresis, and microneedle or needleless (eg, POWDERJECT™ and BIOJECT™) injection. Formulations for topical administration can be prepared with immediate or modified release, as described above.

The compound of formula 1 can also be administered intranasally or by inhalation, typically in the form of a dry powder, aerosol spray or nasal drops. The inhaler can be used to administer a dry powder containing the API alone, a powder mixture of the API and a diluent such as lactose, or particles containing a mixture of the API and a phospholipid such as phosphatidylcholine. The powder for intranasal use may include a bioadhesive agent, such as chitosan or cyclodextrin. A pressurized container, pump, nebulizer, aerosol inhaler, or nebulizer can be used to produce a nebulized aerosol from a solution or suspension containing the API, one or more agents for dispersing, dissolving, or prolonging the release of the API (e.g., EtOH with water or without), one or more solvents (for example, 1,1,1,2-tetrafluoroethane or 1,1,1,2,3,3,3-heptafluoropropane) that act as a propellant, and optionally a surfactant , such as sorbitan trioleate, oleic acid or oligolactic acid. An aerosol electrohydrodynamic inhaler can be used to produce a fine sprayed suspension.

Before use in a dry powder or suspension formulation, the drug product is typically crushed to a particle size suitable for delivery by inhalation (typically 90% of the particles by volume have a largest particle size of less than 5 microns). This may be achieved by any suitable comminution method, such as spiral jet milling, fluidized bed jet milling, supercritical fluid processing, high pressure homogenization, or spray drying.

Capsules, blisters and cartridges (made, for example, from gelatin or hydroxypropyl methylcellulose) for use in an inhaler or insufflator are prepared so that they can contain a powder mixture of the active compound, a suitable powder base such as lactose or starch, and a performance modifier such such as L-leucine, mannitol or magnesium stearate. Lactose may be anhydrous or a monohydrate. Other suitable excipients include dextran, glucose, maltose, sorbitol, xylitol, fructose, sucrose and trehalose.

A suitable solution formulation for use in an electrohydrodynamic aerosol inhaler to produce a fine atomized suspension may contain from about 1 μg to about 20 mg of API per activation of the device, and the volume released upon activation may be from about 1 μL to about 100 μL. A typical formulation may contain the compound of formula 1, propylene glycol, sterile water, EtOH and NaCl. Alternative solvents that can be used instead of propylene glycol include glycerin and polyethylene glycol.

Formulations for inhalation administration, intranasal administration, or both of these routes of administration can be prepared with the possibility of immediate or modified release, for example, using PGLA. Suitable flavoring agents such as menthol and levomenthol or sweeteners such as saccharin or sodium saccharinate may be added to formulations intended for inhalation/intranasal administration.

For dry powder and aerosol inhalers, the unit dose is determined by a valve that delivers the measured amount. Dosing units are typically configured to administer a metered dose or “spray” containing from about 10 μg to about 1000 μg of API. The total daily dose typically ranges from about 1 mg/kg to about 500 mg/kg and may be administered as a single dose or, more commonly, as separate doses throughout the day.

The active compounds can be administered rectally or intravaginally, for example, in the form of a suppository, pessary or enema. Cocoa butter is the traditional base for suppositories, but various alternatives can be used if necessary. Formulations for rectal or intravaginal administration may be formulated for immediate or modified release as described above.

The compound of Formula 1 can also be administered directly to the eyes or ears, typically as drops of a micronized suspension or solution in isotonic, pH-controlled sterile saline. Other formulations suitable for ocular and auricular administration include ointments, gels, biodegradable implants (eg, absorbable gel sponges, collagen), non-biodegradable implants (eg, silicone), implantable capsules, lenses, and dispersed or bubble systems such as niosomes or liposomes. The composition may include one or more polymers and a preservative such as benzalkonium chloride. Typical polymers include cross-linked polyacrylic acid, polyvinyl alcohol, hyaluronic acid, cellulose polymers (eg, hydroxypropyl methylcellulose, hydroxyethylcellulose, methylcellulose) and heteropolysaccharide polymers (eg, gellan gum). These compositions can also be delivered by iontophoresis. Formulations for ophthalmic or auricular administration may be formulated for immediate or modified release as described above.

To improve solubility, dissolution rate, flavor correction, bioavailability, or stability, the compound of Formula 1 can be combined with soluble macromolecular moieties, including cyclodextrin or derivatives thereof and polyethylene glycol-containing polymers. For example, API-cyclodextrin complexes are generally suitable for most dosage forms and routes of administration. Both inclusion complexes and non-inclusion complexes can be used. As an alternative to direct complexation with the API, cyclodextrin can be used as an auxiliary additive, i.e. as a carrier, diluent or solubility enhancer. Alpha, beta and gamma cyclodextrins are usually used for these tasks. See, for example, WO 91/11172, WO 94/02518 and WO 98/55148, each of which is incorporated herein by reference in its entirety.

As noted above, the compound of formula 1, including its pharmaceutically acceptable complexes, salts, solvates and hydrates, can be used in combination with one or more other pharmaceutically active compounds for the treatment of various diseases, disorders and conditions. In these cases, the active compounds may be combined in a single dosage form, as described above, or may be provided in the form of a kit that is suitable for co-administration of the compositions. The kit contains (1) two or more different pharmaceutical compositions, at least one of which contains a compound of formula 1; and (2) a device for separately storing two pharmaceutical compositions, such as a compartmented bottle or a compartmented foil pouch. An example of such a set is the well-known blister pack, which is used when packaging tablets or capsules. The kit is suitable for administering different types of dosage forms (eg, oral and parenteral) or for administering different pharmaceutical compositions at different dosage intervals or for selecting the relative doses of different pharmaceutical compositions. To improve patient compliance with the treatment regimen, the kit typically contains an administration guide and may be provided with a reminder sheet.

For administration to a human patient, the total daily dose of the compound of the invention will typically range from about 0.1 mg/kg to about 1.0 mg/kg or from about 0.5 mg/kg to about 5.0 mg/kg . In certain embodiments, the compound or a pharmaceutically acceptable salt thereof is administered at a dose ranging from about 40 mg/kg to about 60 mg/kg. In certain embodiments, a compound of Formula 1 or a pharmaceutically acceptable salt thereof administered in the method described herein is administered at a dose selected from the group of ranges consisting of: from about 5 mg/kg to about 15 mg/kg, from about 10 mg/kg to about 20 mg/kg, from about 15 mg/kg to about 25 mg/kg, from about 20 to about 30 mg/kg, from about 25 mg/kg to about 35 mg/kg, from about 30 mg/kg to about 40 mg/kg, about 35 mg/kg to about 45 mg/kg, and about 45 mg/kg to about 55 mg/kg. In certain embodiments, the dose is within a range selected from the group consisting of: about 30 mg/kg to about 40 mg/kg, about 35 mg/kg to about 45 mg/kg, about 40 mg/kg to about 50 mg/kg, about 45 mg/kg to about 55 mg/kg, about 50 mg/kg to about 60 mg/kg, about 55 mg/kg to about 65 mg/kg, and about 60 mg/kg up to approximately 70 mg/kg. In certain embodiments, the dose may be about 50 mg/kg. In certain embodiments, the dose is greater than about 1 mg/kg. In certain embodiments, the dose is about 1 mg/kg. In certain embodiments, the dose is in a range selected from the group consisting of: about 50 mg/kg to about 100 mg/kg, about 100 mg/kg to about 150 mg/kg, about 150 mg/kg to about 200 mg/kg, from about 200 mg/kg to about 250 mg/kg, from about 250 mg/kg to about 350 mg/kg, from about 300 mg/kg to about 350 mg/kg, from about 350 mg/kg to about 400 mg/kg, from about 400 mg/kg to about 450 mg/kg, from about 450 mg/kg to about 500 mg/kg. In certain embodiments, the dose is about 500 mg/kg. Alternatively, the dose is less than 500 mg/kg.

In certain embodiments, the dose is 35 mg/kg. In certain embodiments, the dose is 36 mg/kg. In certain embodiments, the dose is 37 mg/kg. In certain embodiments, the dose is 38 mg/kg. In certain embodiments, the dose is 39 mg/kg. In certain embodiments, the dose is 40 mg/kg. In certain embodiments, the dose is 41 mg/kg. In certain embodiments, the dose is 42 mg/kg. In certain embodiments, the dose is 43 mg/kg. In certain embodiments, the dose is 44 mg/kg. In certain embodiments, the dose is 45 mg/kg. In certain embodiments, the dose is 46 mg/kg. In certain embodiments, the dose is 47 mg/kg. In certain embodiments, the dose is 48 mg/kg. In certain embodiments, the dose is 49 mg/kg. In certain embodiments, the dose is 50 mg/kg. In certain embodiments, the dose is 51 mg/kg. In certain embodiments, the dose is 52 mg/kg. In certain embodiments, the dose is 53 mg/kg. In certain embodiments, the dose is 54 mg/kg. In certain embodiments, the dose is 55 mg/kg. In certain embodiments, the dose is 56 mg/kg. In certain embodiments, the dose is 57 mg/kg. In certain embodiments, the dose is 58 mg/kg. In certain embodiments, the dose is 59 mg/kg. In certain embodiments, the dose is 60 mg/kg. In certain embodiments, the dose is 61 mg/kg. In certain embodiments, the dose is 62 mg/kg. In certain embodiments, the dose is 63 mg/kg. In certain embodiments, the dose is 64 mg/kg. In certain embodiments, the dose is 65 mg/kg. The total daily dose may be administered in one or more separate doses and may, at the discretion of the attending physician, be outside the typical ranges given above. Although the dosages indicated are for the average human subject weighing between about 60 kg and about 70 kg, the healthcare practitioner will be able to determine the appropriate dosage for a patient (e.g., a pediatric patient) whose weight falls outside the indicated body weight range. .

The compound of formula 1 can be used to treat diseases, disorders and conditions in which modulation of GPR6 is indicated. As noted above, antagonism or inverse agonism of Gs-coupled GPR6 provides a functional alternative to dopamine-mediated D2 receptor activation. Thus, compounds that modulate GPR6 activity may be suitable for the treatment of various neurological and psychiatric disorders, including mobility disorders such as Parkinson's disease, levodopa-induced dyskinesias and Huntington's disease, as well as drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy and depression. In certain embodiments, the compound of formula 1 improves the motor symptoms of a subject to cure Parkinson's disease. In certain embodiments, a compound of Formula 1 is used in combination therapy with amantadine to treat these disorders.

A pathological hallmark of Parkinson's disease is the loss of nerve cells in the substantia nigra. Degeneration of the nigrostriatal pathway results in decreased dopamine concentrations in the striatum, which clinically manifests as motor and non-motor symptoms. Many patients with Parkinson's disease are treated with levodopa, a prodrug of dopamine. Levodopa often causes severe side effects, including levodopa-induced dyskinesia (LID), impulse control disorders (ICD), psychotic symptoms, and sleep disturbances. LID is a progressive disease, and approximately 90% of patients with Parkinson's disease develop LID within 10 years. In mouse models of LID, irreversible changes occur in D1 receptor signaling in the SSN, including decreased desensitization that results in increased sensitivity in the forward pathway. Genetic inactivation of D1, but not D2, receptors eliminates LID in mice. However, blockade of D1 receptor signaling does not affect the effectiveness of levodopa against Parkinson's disease. The 6-OHDA model mimics many aspects of Parkinson's disease, including loss of dopamine neurotransmission and motor deficits.

The present compound can be used in combination with one or more other pharmacologically active compounds or therapies for the treatment of one or more diseases, disorders or conditions associated with GPR6. These combinations may provide significant therapeutic benefits, including reduced side effects, improved efficacy in treating underserved patient populations, or synergistic activity. For example, a compound of Formula 1, including pharmaceutically acceptable complexes, salts, solvates and hydrates thereof, can be administered simultaneously, sequentially or separately in combination with one or more compounds or therapies for the treatment of movement disorders, including Parkinson's disease. Said compounds include levodopa; DOPA decarboxylase inhibitors such as carbidopa, benserazide, methyldopa, α-difluoromethyl-DOPA, and 3',4',5,7-tetrahydroxy-8-methoxyisoflavone; dopamine agonists such as apomorphine hydrochloride, bromocriptine, rotigotine, pramipexole and ropinirole; amantadine; anticholinergics such as trihexyphenidyl and benztropine mesylate; selective monoamine oxidase B (MAO-B) inhibitors such as safinamide, selegiline and rasagiline; and catechol-O-methyltransferase (COMT) inhibitors such as entacapone and tolcapone.

In addition to drugs used to treat movement disorders, the compound of formula 1 can be used in combination with drugs used to treat Alzheimer's disease and other diseases, disorders and conditions affecting cognitive function. These drugs include beta-secretase inhibitors, gamma-secretase inhibitors, HMG-CoA reductase inhibitors, non-steroidal anti-inflammatory drugs (NSAIDs such as apazone, aspirin, celecoxib, diclofenac (with or without misoprostol), diflunisal, etodolac, fenoprofen , flurbiprofen, ibuprofen, indomethacin, ketoprofen, meclofenamate sodium, mefenamic acid, meloxicam, nabumetone, naproxen, oxaprozin, phenylbutazone, piroxicam, choline and magnesium salicylates, salsalate and sulindac), vitamin E and amyloid antibodies. Specific examples of compounds useful for the treatment of Alzheimer's disease include donepezil, rivastigmine, memantine and galantamine.

In addition or alternatively, the compound of formula 1 can be used in combination with sedatives, hypnotics, antipsychotics, antipsychotics, tranquilizers and other drugs used in the treatment of neurological or psychiatric diseases. For example, a compound of formula 1 can be used in combination with one or more agents for the treatment of depression (antidepressants) and/or schizophrenia (atypical or typical antipsychotics), including amitriptyline, amoxapine, aripiprazole, asenapine, bupropion, chlordiazepoxide, citalopram, chlorpromazine, clozapine, desipramine, desvenlafaxine, doxepin, duloxetine, escitalopram, fluoxetine, fluoxetine, fluphenazine, haloperidol, iloperidone, imipramine, isocarboxazid, lamotrigine, levomilnacipran, lurasidone, mirtazapine, nefazodone, nortriptyline, olanzapine, paliperidone, paroxetine, phenazine, phenelzine, protriptyline, quetiapine, risperidone, selegiline, sertraline, tranylcypromine, trazodone, trimipramine, venlafaxine, vilazodone and vortioxetine and ziprasidone.

Likewise, a compound of formula 1 can be used in combination with one or more agents for the treatment of anxiety (anxiolytics), including benzodiazepines (alprazolam, chlordiazepoxide, clobazepam, clonazepam, clonazepate, diazepam, estazolam, flurazepam, lorazepam, midazolam, oxazepam, prazepam, quazepam , temazepam and triazolam), antihistamines (hydroxyzine), agents other than benzodiazepines (eszopiclone, zaleplon, zolpidem and zopiclone), and buspirone.

The compound of formula 1 can also be used in combination with one or more agents for the treatment of epilepsy (antiepileptic or anticonvulsants), including acetazolamide, carbamazepine, clobazam, clonazepam, eslicarbazepine acetate, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, nitrazepam, oxcarbazepine, perampanel , piracetam, phenobarbital, phenytoin, pregabalin, primidone, retigabine, rufinamide, sodium valproate, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide.

BIOLOGICAL ACTIVITY

The activity of compounds as GPR6 modulators can be determined by various methods, including in vitro and in vivo methods.

I. In vitro cAMP inhibition (EC50)

This cell-based assay measures the ability of the test compounds to inhibit the constitutive activity of the cAMP receptor GPR6 expressed by CHO-K1 cells. CHO cells stably express the GPR6 receptor, the expression of which is controlled by a tetracycline-inducible element. Cells were grown in a medium containing F12K, 10% FBS, 1% penicillin/streptomycin, and 200 μg/ml hygromycin. GPR6 receptor was expressed for 20 hours using 2 μg/ml doxycycline (Sigma D9891) in growth medium. After doxycycline addition was completed, cells were seeded at a density of 450-750 cells per well into 96-well black tissue culture plates with half the volume (Costar) and placed in an incubator (37°C, 5% CO ₂ ) for 20 hours before cAMP analysis. .

The nutrient medium was removed from the cells and the cells were washed with 50 μl/well of Ringer's buffer (MgCl ₂ 0.047 mg/ml, NaH ₂ PO ₄ 0.18 mg/ml, Na ₂ HPO ₄ 0.1 mg/ml, KCl 0.34 mg/ml ml, NaHCO ₃ 1.26 mg/ml, D-glucose 1.8 mg/ml, NaCl 7 mg/ml; pH=7.4). The test compounds were suspended in DMSO, diluted with Ringer's buffer containing 0.5% fatty acid-free BSA and 300 μM 3-isobutyl-1-methylxanthine (IBMX), and incubated with the cells for 45 minutes at 37 °C and 5% CO ₂ . After incubation, cells were treated for 10 minutes at room temperature with a Eu-cAMP-labeled solution from the PerkinElmer LANCE® Ultra cAMP Assay Kit (TRF0263). The ULIGHT™-anti-cAMP solution from the LANCE® kit was then added and incubated on a shaker at room temperature for 1 hour before detection using homogeneous time-resolved fluorescence (HTRF) on a PerkinElmer EnVision plate analyzer. Curves were generated to determine EC ₅₀ using a four-parameter logistic equation using GraphPad Prism 5.03.

II. In vitro cAMP inhibition (IC50)

This cell-based assay also measures the ability of the compounds to inhibit the constitutive activity of the cAMP receptor GPR6 expressed by CHO-K1 cells. CHO cells stably express the GPR6 receptor, the expression of which is controlled by a tetracycline-inducible element. Cells were grown in a medium containing F12K, 10% FBS, 1% penicillin/streptomycin, and 200 μg/ml hygromycin. GPR6 receptor was expressed for 20 hours using 1 μg/ml doxycycline (Sigma D9891) in growth medium. After doxycycline addition was completed, cells were seeded at a density of 250–500 cells per well into black half-well clear-bottom plates (Costar) and placed in an incubator (37°C, 5% CO ₂ ) for 20 hours before cAMP analysis.

The nutrient medium was removed from the cells and the cells were washed with 50 μl of Ringer's buffer (MgCl ₂ 0.047 mg/ml, NaH ₂ PO ₄ 0.18 mg/ml, Na ₂ HPO ₄ 0.1 mg/ml, KCl 0.34 mg/ml, NaHCO ₃ 1.26 mg/ml, D-glucose 1.8 mg/ml, NaCl 7 mg/ml; pH=7.4). Compounds suspended in DMSO were diluted with Ringer's buffer containing 0.5% fatty acid-free BSA and incubated with cells for 45 minutes at 37°C and 5% CO ₂ . After incubation, cells were incubated for 10 minutes at room temperature with Eu-cAMP-labeled solution from the PerkinElmer LANCE® Ultra cAMP Assay Kit (TRF0264). The ULIGHT™-anti-cAMP solution from the LANCE® kit was then added and incubated on a shaker at room temperature for 1 hour before detection in HTRF mode on a BMG POLARSTAR® Omega plate analyzer. IC ₅₀ curves were generated using a four-parameter logistic equation using GraphPad Prism 5.03.

III. Competitive binding to GPR6 in vitro (Ki)

Filter-based competitive binding assays are used to study the binding characteristics of GPR6 inverse agonists. The method uses membranes obtained from CHO-K1 cells expressing human GPR6 cDNA under the influence of a doxycycline-inducible promoter. Study-ready preparations in DMSO in 96-well plates (651201, Greiner, USA) containing serially diluted test compounds (1 μl of test ligand/well) were prepared using liquid manipulators (5 μM, final maximum concentration in the study). Assay buffer (50 mM Tris, pH 7.4, 50 mM NaCl, 6 mM _MgCl2 , 0.1% fatty acid-free BSA, 1:100 proteinase inhibitor cocktail, Sigma USA) was added (39 µl/well) and mixed the plates on a plate shaker for 10 minutes. GPR6-specific ^3H radioligand was prepared in assay buffer and added to each well (40 μl, 2.4 nM final assay concentration).

To initiate binding reactions, 40 μl of whole membranes prepared from cells expressing human GPR6 receptors were added. Membrane preparations were prepared in assay buffer and added to wells to achieve a final assay concentration of 15 μg/well. The plates were capped, mixed for 30 seconds at 300 rpm, and incubated for 2 hours at room temperature. The reaction mixtures were then filtered through a FilterMate system (1450-421, FilterMate A, PerkinElmer, USA) and washed 5 times with buffer (50 mM Tris, pH 7.4, 50 mM NaCl, 6 mM MgCl ₂ , 0.1% BSA, not containing fatty acids) using the Tomtec HARVERSTER96™ tool. The filters were dried in the microwave. Scintillation sheets (1450-411, PerkinElmer, USA) were melted onto the filters and sealed before quantification of CPM/well using a MICROBETA® Trilux instrument (PerkinElmer, USA). Before use, soak the FilterMate system in 0.5% polyethyleneimine solution for 3 hours with gentle shaking, then air dry overnight. IC ₅₀ and Ki values were calculated using nonlinear regression analysis in Prism (GraphPad, USA). Kd values were determined in standard radioligand saturation experiments.

IV. In vivo model of Parkinson's disease - haloperidol-induced catalepsy

Motor symptoms of Parkinson's disease include akinesia, bradykinesia, stiffness, tremors, and postural disturbances and are associated with loss of nigral dopaminergic cells and decreased dopamine levels in the striatum. Administration of haloperidol to rodents results in a transient condition similar to Parkinson's disease, which is reversed by administration of levodopa and other drugs that have been clinically approved for the treatment of Parkinson's disease. See Duty, S. & Jenner, P. Br. J. Pharmacol. 164:1357-1391 (2011), the contents of which are incorporated herein by reference in their entirety. Haloperidol acts as an antagonist of dopamine D2 receptors and, to a lesser extent, dopamine D1 receptors in medium spiny neurons, which include the indirect and direct pathways of the motor circuit, respectively. The resulting blockade of dopamine transmission in the striatum leads to impaired downstream firing of neurons in the basal ganglia circuits, which manifest as symptoms of muscle stiffness and catalepsy. It has been found that catalepsy reflects the clinical signs of Parkinson's disease, when patients note an inability to perform movements.

Male C57Bl6 mice weighing 25-35 g were used. Catalepsy was induced by subcutaneous (SC) administration of the dopamine receptor antagonist haloperidol (0.45 mg/kg) at least 30 minutes before testing the animals on a vertical grid. For this test, rats or mice were placed on the wire lid of a 25 cm × 43 cm Plexiglas cage placed at an angle of approximately 70 degrees relative to the laboratory bench. The subject was placed on the grid with all four legs abducted and extended (“frog position”). The use of such an unnatural posture is critical to the specific nature of this catalepsy study. The time interval from the moment the rat's paws were placed in this position until the first paw was completely removed (the time before the start of descent) was measured for no more than 120 seconds. For mice, the front paws were placed on a horizontal metal rod raised 2 inches (5 cm) relative to the Plexiglas platform and the time was noted, to a maximum of 30 seconds for each trial. The study was completed when the animal returned its front paws to the platform, or after 30 seconds. The test was repeated three times and the average of the three trials was reported as an index of catalepsy intensity. Animals were assessed 30 minutes after dosing and re-evaluated 60 or 90 minutes after dosing with haloperidol.

The efficacy of GPR6 modulators in reversing haloperidol-induced catalepsy was measured at 30 minutes, 60 minutes, and/or 90 minutes after subjects were administered 0.45 mg/kg i.p. (intraperitoneal injection) of haloperidol together with an investigational GPR6 modulator compound. The compound of formula 1 was administered at a dose ranging from 0.1 to 100 mg/kg (oral/po in 0.5% methylcellulose) together with haloperidol. The adenosine A2A antagonist SCH 420814 (preladenant) was administered at a dose of 3 mg/kg i.p. as a positive control.

V. Inhibition of human hERG by patch-clamp

An automated whole-cell voltage clamp system (QPATCH® 16) was used to record potassium currents leaving a single cell. The study used CHO-K1 cells (Chinese hamster ovary cells) stably transfected with human hERG cDNA. Cells were collected after trypsin treatment and maintained in serum-free medium at room temperature before analysis. Cells were washed and resuspended in extracellular solution, and then applied to areas for automated voltage clamping. The test solutions were prepared in an aqueous extracellular solution (137 mM NaCl, 4 mM KCl, 1.8 mM _CaCl2 , 1 mM _MgCl2 , 10 mM D(+)-glucose, 10 mM HEPES, pH adjusted to 7.4 with NaOH ) on the day of the voltage fixation study. The test compound at seven concentrations (0.03, 0.1, 0.3, 1, 3, 10 and 30 μM) was used to determine the _IC50 . The aqueous intracellular solution contained 130 mM KCl, 10 mM NaCl, 1 mM MgCl ₂ , 10 mM EGTA, 5 mM Mg-ATP, and 10 mM HEPES (pH adjusted to 7.2 with KOH).

After reaching the whole cell configuration, the cell was maintained at −80 mV. −40 mV pulses of 50 ms duration were delivered to measure the leakage current, which was subtracted from the trace current online. The cell was then depolarized to +20 mV for 2 s, after which a 1 s −40 mV pulse was delivered to detect hERG trace current. This pulse train was delivered every 5 seconds to monitor current amplitude. The study was carried out at room temperature. First, an extracellular solution (control) was used and the cell was stabilized in the solution for 5 minutes. The test compound was then applied to the same cell sequentially at low to high concentrations. The cells were incubated together with the compound at each concentration tested for 5 minutes. At the same time, the reference compound E-4031 (N-(4-(1-(2-(6-methylpyridin-2-yl)ethyl)piperidin-4-carbonyl)phenyl)methanesulfonamide) was tested at several concentrations to obtain the IC ₅₀ value . Percentage inhibition of the hERG channel was calculated by comparing the amplitude of the trace current before and after application of the compound (the difference in currents was normalized to the control).

EXAMPLES

The following examples are illustrative and non-limiting and represent specific embodiments of the present invention.

I. ¹ H nuclear magnetic resonance (NMR)

¹ H NMR spectra were obtained for many of the compounds shown in the following examples. Characteristic chemical shifts (δ) are reported in parts per million relative to the tetramethylsilane signal using traditional abbreviations for major peaks, including s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), and br. (wide). The following abbreviations are used to describe traditional solvents: CDCl ₃ (deuterated chloroform), DMSO-d ₆ (deuterated dimethyl sulfoxide), CD ₃ OD (deuterated methanol), CD ₃ CN (deuterated acetonitrile) and THF-d ₈ (deuterated tetrahydrofuran). Mass spectra (m/z for [M+H] ⁺ ) were obtained by electron sputter ionization mass spectrometry (ESI-MS) or atmospheric pressure chemical ionization (APCI-MS).

II. High performance liquid chromatography (HPLC)

Where indicated, the products obtained in certain preparation examples and examples were purified on a mass range activated HPLC system (eg pump: WATER™ 2525; MS: ZQ™; software: MASSLYNX™) by flash chromatography or preparative thin layer chromatography (TLC). Reverse phase chromatography was typically performed on a column (e.g. Phenomenex GEMINI™ 5 µm, C18, 30 mm × 150 mm; AXIA™, 5 µm, 30 mm × 75 mm) under acidic conditions (“acid mode”), eluting with mobile phases based on CH ₃ CN and water containing 0.035% and 0.05% trifluoroacetic acid (TFA), respectively, or under basic conditions (“basic mode”), eluting with mobile phases based on water and 20/80 (v/v ./vol.) mixtures of water/acetonitrile, each of which contained 10 mM NH ₄ HCO ₃ . Preparative TLC was usually carried out on silica gel 60 F ₂₅₄ plates. After isolation by chromatography, the solvent was removed and the product was obtained by drying in a centrifugal evaporator (eg, GeneVac™), rotary evaporator, vacuum flask, etc. Reactions under an inert atmosphere (eg, nitrogen) or a reactive atmosphere (eg, H ₂ ) are typically carried out at a pressure of about 1 atmosphere (14.7 psi).

III. Synthesis

PREPARATION EXAMPLE 1: (R)-2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-N-(tetrahydrofuran-3-yl)pyrido[3,4-b]pyrazin-3-amine

To a solution of 3-chloro-2-(4-(2,4-difluorophenoxy)piperidin-1-yl)pyrido[3,4-b]pyrazine (10 g, 26.5 mmol) in DMSO (50 ml) was added ( R)-tetrahydrofuran-3-amine (ArkPharm, AK-75910, lot no. WZG082316-PB01) (5.32 ml, 61.0 mmol). The solution was heated at 70 °C for 10 hours, then diluted with water (300 ml) and extracted with iPrOAc (300 ml). The aqueous phase was further extracted with iPrOAc (100 ml). Combine the organic layers, wash with saturated aqueous NH ₄ Cl (300 ml) and brine (200 ml), dry over MgSO ₄ , concentrate in vacuo and dry on a household vacuum pump to give a light yellow solid (11.4 g). Dissolve the solid in iPrOAc (55 ml) with stirring and heat to reflux temperature. Heptane (33 ml) was added slowly piecemeal while heating to prevent precipitation. The solution was then allowed to cool to 20 °C with stirring (approximately 400 rpm), during which time a precipitate formed. Slowly cool the mixture to ambient temperature and stir overnight. Collect the solid by vacuum filtration, wash with ice-cold 20% iPrOAc in heptane, dry by evacuating the filter cake for at least 30 minutes and collect to give the title compound as a light yellow solid (9.771 g, 86%). ¹ H NMR (500 MHz, DMSO-d ₆ ) δ ppm 1.84 - 1.96 (m, 2H), 2.01 - 2.16 (m, 3H), 2.20 - 2.31 (m, 1H), 3.22 - 3.31 (m, 2H), 3.64 - 3.80 (m, 4H), 3.85 - 3.93 (m, 1H), 4.00 (dd, J= 9.28, 6.35 Hz, 1H), 4.55 - 4.67 (m, 2H), 6.94 (d, J=5.86 Hz, 1H), 6.99 - 7.06 (m , 1H), 7.25 - 7.37 (m, 2H), 7.46 (d, J=5.37 Hz, 1H), 8.31 (d, J=5.37 Hz, 1H), 8 .79 (s, 1H); ESI-MS m/z [M+H] ⁺ 428.

PREPARATION EXAMPLE 2: (S)-2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-N-(tetrahydrofuran-3-yl)pyrido[3,4-b]pyrazin-3-amine

To a solution of 3-chloro-2-(4-(2,4-difluorophenoxy)piperidin-1-yl)pyrido[3,4-b]pyrazine (1.0 g, 2.65 mmol) in DMSO (5 ml) (S)-tetrahydrofuran-3-amine (AstaTech, cat. no. 37021) (0.578 ml, 6.64 mmol) was added. Heat the solution at 70 °C in a sealed microwave reactor tube for 22 hours, after which HPLC-MS analysis indicated completion of the reaction. The reaction mixture (5 ml) was diluted with water (150 ml) and extracted with iPrOAc (150 ml). The aqueous phase was further extracted with iPrOAc (50 ml). Combine the organic layers, wash with saturated aqueous NH ₄ Cl (150 ml) and brine (100 ml), dry over MgSO ₄ and concentrate in vacuo on CELITE®. Purify the crude product by column chromatography (30 g NH silica gel column), eluting with a gradient of 0 to 60% EtOAc in heptane to give the title compound as a white solid (1.05 g, 93%). ¹ H NMR (500 MHz, DMSO-d ₆ ) δ ppm 1.90 (td, J=8.54, 3.91 Hz, 2H), 2.01 - 2.16 (m, 3H), 2.20 - 2.31 (m, 1H), 3.21 - 3.32 (m, 2H), 3.63 - 3.80 (m, 4H), 3.89 (q, J=7.49 Hz, 1H ), 4.00 (dd, J=9.28, 6.35 Hz, 1H), 4.54 - 4.67 (m, 2H), 6.96 (d, J=6.35 Hz, 1H) , 7.00 - 7.08 (m, 1H), 7.26 - 7.39 (m, 2H), 7.46 (d, J=5.37 Hz, 1H), 8.31 (d, J =5.37 Hz, 1H), 8.79 (s, 1H); ESI-MS m/z [M+H] ⁺ 428.

EXAMPLE 1: (R)-1-(2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-3-((tetrahydrofuran-3-yl)amino)-7,8-dihydropyrido[3, 4-b]pyrazin-6(5H)-yl)ethan-1-one

Into a flask containing (R)-2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-N-(tetrahydrofuran-3-yl)pyrido[3,4-b]pyrazin-3-amine ( 16 g, 37.4 mmol) in HOAc (80 mL) and THF (80 mL), acetic anhydride (17.66 mL, 187 mmol) was added under nitrogen. Carbon-supported palladium (10%, Aldrich 205699-10G, lot no. MKBZ3284V) (3.19 g, 2.99 mmol) was added under nitrogen. The flask was attached to a balloon filled with hydrogen and evacuated eight times using a household vacuum pump and refilled with hydrogen. The reaction mixture was stirred under hydrogen for 40 hours and then filtered through a CELITE® pad, being careful not to allow the precipitate to dry out. Wash the flask and filter cake with EtOAc (48 ml), methanol (48 ml) and EtOAc (48 ml). Concentrate the filtrate in vacuo to remove THF, EtOAc and methanol (bath temperature less than or equal to 40 °C). Dilute the solution with heptane (480 mL) and reconcentrate in vacuo to remove HOAc by azeotropic distillation (bath temperature less than or equal to 45 °C). Place the residue in iPrOAc (320 ml), wash with 10 wt.% aqueous K ₂ CO ₃ (320 ml, 230 mmol) (pH 13 before rinse, pH 10 after rinse) and saline (240 ml, pH 7 after rinse), dried over MgSO ₄ , concentrated in vacuo and dried using a household vacuum pump for at least 1 hour to obtain a light yellow solid (16.71 g). Place the crude product in ethanol (84 ml) and heat in an oil bath with stirring. After the solids had dissolved, the solution was allowed to cool slowly in an oil bath while stirring, at which time a precipitate began to form and the solution became cloudy. The mixture was allowed to cool to ambient temperature in an oil bath and stirred overnight. The white solid after recrystallization was collected by vacuum filtration, washed with ice-cold ethanol and dried under high vacuum to give the title compound as a white solid (13.34 g, 75%). ¹ H NMR (500 MHz, DMSO-d ₆ ) δ ppm 1.81 - 2.00 (m, 3H), 2.02 - 2.12 (m, 5H), 2.14 - 2.24 (m, 1H), 2.60 (t, J=5.61 Hz, 1H), 2.72 (t, J=5.86 Hz, 1H), 2.84 - 2.96 (m, 2H), 3, 26 - 3.32 (m, 2H), 3.56 (dt, J=8.79, 5.13 Hz, 1H), 3.65 - 3.78 (m, 3H), 3.81 - 3, 94 (m, 2H), 4.33 - 4.47 (m, 3H), 4.52 (tt, J=8.18, 4.03 Hz, 1H), 5.91 (dd, J=13, 42, 6.10 Hz, 1H), 6.97 - 7.05 (m, 1H), 7.24 - 7.36 (m, 2H); ESI-MS m/z [M+H] ⁺ 474; _{Melting point} 150 °C (DSC peak); chiral purity (chiral column chromatography) greater than 98% ee.

COMPOUND A: (S)-1-(2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-3-((tetrahydrofuran-3-yl)amino)-7,8-dihydropyrido[3, 4-b]pyrazin-6(5H)-yl)ethan-1-one

Into a flask containing (S)-2-(4-(2,4-difluorophenoxy)piperidin-1-yl)-N-(tetrahydrofuran-3-yl)pyrido[3,4-b]pyrazin-3-amine ( 1.05 g, 2.456 mmol) in HOAc (5 mL) and THF (5 mL), acetic anhydride (1.159 mL, 12.28 mmol) was added under nitrogen. Carbon-supported palladium (10%, Aldrich 205699-10G, lot no. MKBZ3284V) (0.523 g, 0.491 mmol) was added under nitrogen. The flask was attached to a balloon filled with hydrogen and evacuated eight times using a household vacuum pump and refilled with hydrogen. Stir the reaction mixture under a hydrogen atmosphere for 18 hours and then filter through a Celite® pad, being careful not to allow the precipitate to dry out. Wash the flask and filter cake with EtOAc (20 ml), methanol (20 ml) and EtOAc (20 ml) and concentrate the filtrate in vacuo on a CELITE®. Purify the crude product by column chromatography (120 g NH silica gel column, size 200), eluting with a gradient of 0 to 60% EtOAc in heptane to give a white solid (1.0 g). Place the white solid in ethanol (5 ml) and heat to 80 °C in an oil bath with stirring. Once the solids had dissolved, the heat source was removed and the solution was allowed to cool slowly in an oil bath to 20 °C with stirring. The mixture was stirred for 3 days at room temperature. The solids were collected by vacuum filtration, washed with ice-cold ethanol, and dried under high vacuum to give the title compound as a white solid (848 mg, 72.9%). ¹ H NMR (500 MHz, DMSO-d ₆ ) δ ppm 1.82 - 2.00 (m, 3H), 2.02 - 2.12 (m, 5H), 2.13 - 2.24 (m, 1H), 2.60 (t, J=5.86 Hz, 1H), 2.72 (t, J=5.86 Hz, 1H), 2.83 - 2.96 (m, 2H), 3, 24 - 3.32 (m, 2H), 3.56 (dt, J=8.79, 5.25 Hz, 1H), 3.66 - 3.77 (m, 3H), 3.81 - 3, 94 (m, 2H), 4.33 - 4.47 (m, 3H), 4.52 (tt, J=8.08, 3.87 Hz, 1H), 5.93 (dd, J=13, 30, 6.22 Hz, 1H), 6.98 - 7.06 (m, 1H), 7.24 - 7.35 (m, 2H); ESI-MS m/z [M+H] ⁺ 474; _{Melting point} 149 °C (DSC peak); chiral purity (chiral column chromatography) greater than 98% ee.

IV. In vitro cAMP inhibition study (EC ₅₀ )

Table 1 shows the bioassay data (in vitro cAMP inhibition) of Compound of Formula 1 (Example 1) and Compound A, which were tested in a cell-based assay that measured the ability of the test compounds to inhibit the constitutive activity of the cAMP receptor GPR6 expressed by CHO-K1 cells (indicated as pEC ₅₀ ). The study was described herein under the title “In vitro cAMP inhibition (EC ₅₀ ).”

Table 1. Inhibition of the constitutive activity of the cAMP receptor GPR6 in vitro

Compound pEC ₅₀ Formula 1 7.2 Compound A 7.2

Additional analysis was performed to determine the IC ₅₀ of the compounds in the study described herein under the title “In Vitro Inhibition of cAMP (IC ₅₀ ).”

V. In vitro cAMP inhibition study (IC ₅₀ )

Table 2 shows the inhibition constants (Ki) determined in the GPR6 competitive binding assay and the IC ₅₀ values determined in the hERG functional assay for the compound of formula 1 (Example 1) and compound A. As described above, the Ki for each compound was determined in a competitive binding study in a filtration format using membranes derived from CHO-K1 cells expressing human GPR6 cDNA; The IC ₅₀ for each compound was determined in a functional hERG assay using an automated whole cell voltage clamp system and CHO-K1 cells transfected with human hERG cDNA.

The data shown in Table 2 indicate that compound of formula 1 is a significantly less potent hERG inhibitor than compound A. If 50% GPR6 occupancy is assumed at maximum free compound (drug) concentration, then the ratio (hERG IC ₅₀ )/ The Ki given in Table 2 can be considered as a safety margin for free drug (“SM-free”) as defined in the literature (see X. Yao et al., British Journal of Pharmacology (2008) 154:1446 -56, 50, the contents of which are incorporated herein in their entirety by reference). If we compare the safety reserves, the compound of formula 1 has an improved SM-free value. to move on to the in vivo research stage. SM-free value less than 300 is considered suitable for advancing to in vivo studies, as defined by Yao et al on page 1452 (“evidence suggests that an SM-free value of 300 or more may indicate that compound does not have the potential to prolong the QTc interval").

Table 2. Competitive binding of GPR6 (Ki) and hERG inhibition (IC ₅₀ )

Compound Ki (nM) IC ₅₀ (nM) (hERG IC ₅₀ )/Ki Formula 1 5.5 1970 358 Compound A 6.0 505 84

The ability of the compound of formula 1 (Example 1) and compound A to relieve haloperidol-induced catalepsy was also analyzed. The compounds were studied according to the study described herein under the title "In Vivo Model of Parkinson's Disease - Haloperidol-Induced Catalepsy."

VI. Treatment in a rat model of 6-hydroxydopamine (6-OHDA)

Compounds that improve motor performance are being considered as possible therapies for Parkinson's disease. Rats in the 6-OHDA model of Parkinson's disease received bilateral injections of 6-OHDA into the striatum with coordinates along the anterior-posterior axis (AP): medial-lateral axis (ML): superior-inferior axis (DV), 1±3, - 5 mm relative to bregma under anesthesia. The locomotor activity of rats was examined after at least 28 days. The animals were allowed to habituate for 30 minutes in boxes to measure locomotor activity before administration of the compound of formula 1 (example 1) or vehicle (control).

Locomotor activity was measured in an open area covered with a grid of infrared rays. Animal beam interruption analysis was performed using AMLOGGER activity tracking software. The compound of Formula 1 (Example 1) provided a dose-dependent improvement in locomotor activity at both dosages (5 mg/kg and 10 mg/kg) compared to vehicle-treated rats (control) after 50 minutes, as shown in Figure 1. A significant increase in activity was observed in rats administered the 10 mg/kg dose. The data obtained indicate that the compound of Formula 1 (Example 1) can effectively relieve symptoms in patients with Parkinson's disease.

VII. The effect of the compound of formula 1 (example 1) on the cardiovascular system, determined by telemetry

The possible cardiovascular effects of the compound of Formula 1 (Example 1) were studied in awake Beagle dogs (Marsahall BioResources, North Rose, NY) at least 8 months old and weighing 7-15 kg. Beagles were implanted with telemetry devices in DSI PHYSIOTEL® Digital L21 transmitter implants according to the appropriate standard operating procedures of Charles River Laboratories, Montreal, QC (TB 12-04-06). Electrodes for measuring biopotential were placed in a modified II electrode configuration. The minimum acceptable acclimatization period between the arrival of the animal and the start of surgical implantation of telemetry devices was 6 days to acclimate the animals to laboratory conditions. The minimum acceptable recovery period between surgery and the start of treatment was 4 weeks. Target animal housing conditions included temperatures ranging from 17°C to 23°C with 30-70% humidity and a 12-hour day/12-hour cycle with the exception of designated procedures.

Animals may be housed in groups in stainless steel cages equipped with automatic water valves as described in the Manual for the Care and Care of Laboratory Animals ( ^8th ed., National Academies Press, 2111), the contents of which are incorporated herein in their entirety. by reference, except during administration and monitoring periods when animals were caged individually.

For 7 days after surgical implantation of DSI PHYSIOTEL® Digital L21 digital transmitters, animals were given feed supplements that included 1 can of AID Prescription Diet food along with 300 g of PMI NUTRITION® International Certified Canine Chow No. 5007 for 3 days and 1 can of AID Prescription Diet food with 300 g of international certified dog food PMI NUTRITION® International Certified Canine Chow No. 5007 for 4 days. On the day of administration, access to food was provided at least 5 hours before administration, access was provided for 1 hour, and then food was removed at least 4 hours before administration. Meat treats were unavailable after food was removed for 4 hours before administration. Feed, if left, was returned after mortality/morbidity monitoring was completed on the day of administration and left overnight. Supplemental food was offered to animals as needed according to clinical signs or other changes.

Tap water after treatment with reverse osmosis and ultraviolet radiation was provided freely to each animal through an automatic water supply system, with the exception of designated procedures. If necessary, drinking bowls were provided. Water analysis was carried out periodically, and the results of these analyzes were available at the studied installations. No impurities that could obviously interfere with the research objectives were noted in the water.

Before administration, ECG, LVP, blood pressure, and body temperature data were obtained using the Data Sciences International (DSI) PONEMAH™ system for at least 24 hours to assess cardiovascular parameters and ECG signal quality. An ECG was recorded for a minimum of 30 seconds and sent to a cardiologist for qualitative assessment. Only animals with normal hematology/clinical chemistry parameters and normal hemodynamic/ECG parameters were selected for the study.

Animals were allowed to acclimate to the forced oral gavage procedure for at least 3 days before dosing the formulation. Cage water/tap water was administered via an oral gavage using a disposable catheter attached to a plastic syringe at a volume of 5 mL/kg. The administered formulations were mixed in the room in which the animals were kept for at least 30 minutes before administration and continuously during dosing.

A single dose of vehicle (control), which contained 2% lecithin and 0.5% methylcellulose in ULTRAPURE™ water (Charles River Laboratories, Montreal, QC), or test compound at 30, 100, and 300 mg/kg was administered via oral gavage. The vehicle was prepared for each series of experiments and stored in a refrigerator at 4 °C on a mixer plate without access to light and used as needed. Remove the vehicle from the refrigerator and stir for at least 30 minutes at room temperature before administration and continuously during administration. The injected formulations were stored in a refrigerator at 4°C on a mixer plate without access to light and used as needed. Remove the administration formulations from the refrigerator, stir for at least 30 minutes at room temperature before administration and continuously during administration.

Each of four male dogs was administered a dose of vehicle and three dosages of a compound of Formula 1 (Example 1) with an interval of 7 days between doses. Parameters monitored included: heart rate as determined by blood pressure, left ventricular pressure (LVP), and electrocardiogram waveforms; LVP (peak systolic and end systolic LVP and maximum positive/negative dP/dt values); electrocardiogram (PR interval (PR), RR error (RR"), QRS complex (QRS), QT and QTcv intervals calculated using the van de Water equation QTcv=QT-87(60/HR-1)); and body temperature .

ECG segments were marked using ECG Pattern Recognition software. For each animal, a library was collected from representative runs obtained both during the day and at night and used during monitoring to ensure proper labeling for quantification, according to the appropriate SOPs of Charles River Laboratories, Montreal, QC. Any data that exceeded electrophysiological norms for this species were excluded from further analysis.

During each telemetry study on administration days, the ECG was assessed twice before each dose (at least 30 minutes apart) and approximately 1 (±5 minutes), 2, 4, 6, 8, 10, 12, 15, 18, and 23 (±15 minutes) hours after dosing. For each time point, assessment was performed for a minimum of 30 seconds. Qualitative evaluation of all signals was performed to detect arrhythmias or conduction disturbances or other P-QRS-T signal abnormalities. Blood samples were collected from the jugular vein on an empty stomach after chow was stopped overnight (for clinical chemistry parameters).

Beagles administered the compound of Formula 1 (Example 1) showed no changes in arterial blood pressure, contractility, or P-R interval duration, QRS complex, or QT interval compared to the results obtained with vehicle administration.

EQUIVALENTS AND VOLUME

Those skilled in the art will be able to recognize or identify, without going beyond normal experimental work, many equivalents to the specific embodiments of the invention described herein. It is intended that the scope of the present invention not be limited by the above description, but rather be as described in the appended claims.

In the claims, the singular forms (corresponding to the English "a", "an" and "the") may mean one or more than one, unless otherwise indicated or unless otherwise obvious from the context. Conditions in claims or descriptions that include "or" between one or more elements of a group are considered to be satisfied if one, more than one, or all of the elements of the group are present, apply or otherwise relate to the product or method, unless otherwise specified or unless otherwise obvious from the context. The invention includes embodiments in which exactly one element of the group is present, used or otherwise related to a given product or method. The invention includes embodiments in which more than one or all of the elements of a group are present, used or otherwise related to a given product or method.

It should also be noted that the term “comprising” is considered open-ended and allows, but does not require, the inclusion of additional elements or steps. When the term “comprising” is used herein, the term “consisting of” is also included and described.

End values are included in the range descriptions. In addition, it should be understood that unless otherwise indicated or unless otherwise obvious from the context and based on the general knowledge available to those skilled in the art, values expressed as ranges may imply any specific value or subrange within the stated ranges in various embodiments of the invention to the nearest tenth of a unit of the lower limit of the range, unless the context clearly indicates otherwise.

In addition, it should be understood that any specific embodiment of the present invention that relates to the prior art may be expressly excluded from any one or more claims. Since such embodiments are considered known to those skilled in the art, they may be excluded even if such exclusion is not expressly expressed herein. Any particular embodiment of the compositions of the invention (e.g., any antibiotic, therapeutic or active ingredient; any method of preparation; any method of administration; etc.) may be excluded from any one or more claims for any reason, regardless of whether whether it is prior art or not.

It should be understood that the language used is descriptive and not limiting, and changes may be made to the appended claims without departing from the true scope and spirit of the invention in its more general aspects.

Although the present invention has been described in some detail and in detail by means of several embodiments, it is not intended that it should be limited to any specific details or embodiments indicated or to any particular embodiment, but should be considered in light of the appended claims. so that the broadest possible interpretation of the stated claims, taking into account the prior art, is provided and thereby effectively describes the intended scope of the invention. The present invention is further illustrated by non-limiting examples provided herein.

Claims (77)

1. Compound of formula 1 or a pharmaceutically acceptable salt thereof. 2. A compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to an enantiomeric excess (e.i.) of 20% or more. 3. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 40% or more. 4. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 60% or more. 5. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 80% or more. 6. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 90% or more. 7. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 98% or more. 8. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 99% or more. 9. The compound or pharmaceutically acceptable salt according to claim 1, having an enantiomeric purity corresponding to the ee. 100%. 10. A compound or pharmaceutically acceptable salt according to any one of paragraphs. 1-9, characterized in that the specified compound is present in free form. 11. A compound or pharmaceutically acceptable salt according to any one of paragraphs. 1-10 for use as a medicine. 12. A compound or pharmaceutically acceptable salt according to any one of paragraphs. 1-11 for use in the treatment of a disease, disorder or condition associated with GPR6. 13. A compound or pharmaceutically acceptable salt according to any one of paragraphs. 1-12 for use in treatment: (i) a disease, disorder or condition selected from the group consisting of Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression; and/or (ii) Parkinson's disease; and/or (iii) Parkinson's disease in the subject, characterized in that the treatment improves motor symptoms in the subject; and/or (iv) non-motor clinical manifestations of Parkinson's disease. 14. A compound or pharmaceutically acceptable salt according to any one of paragraphs. 1-13, characterized in that said compound or pharmaceutically acceptable salt is intended for: (i) administration at a dose ranging from 0.5 to 5.0 mg/kg; and/or (ii) oral administration. 15. Pharmaceutical composition having GPR6 modulator activity and containing: (a) an effective amount of a compound or pharmaceutically acceptable salt according to any one of claims. 1-14; And (b) a pharmaceutically acceptable excipient. 16. Pharmaceutical composition according to claim 15 for use as a medicine. 17. The pharmaceutical composition according to claim 15 or 16 for use in the treatment of a disease, disorder or condition associated with GPR6. 18. Pharmaceutical composition according to any one of paragraphs. 15-17 for use in treatment: (i) a disease, disorder or condition selected from the group consisting of Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression; and/or (ii) Parkinson's disease; and/or (iii) Parkinson's disease in a subject, characterized in that the treatment improves motor symptoms in the subject; and/or (iv) non-motor clinical manifestations of Parkinson's disease. 19. Pharmaceutical composition according to any one of paragraphs. 15-18, characterized in that said compound or pharmaceutically acceptable salt is intended for: (i) administration at a dose ranging from 0.5 to 5.0 mg/kg; and/or (ii) oral administration. 20. Pharmaceutical composition according to any one of paragraphs. 15-19, further containing at least one additional pharmacologically active agent. 21. The pharmaceutical composition according to claim 20, characterized in that said additional pharmacologically active agent is selected from the group consisting of levodopa, a DOPA decarboxylase inhibitor, a dopamine agonist, an anticholinergic agent, a selective monoamine oxidase B inhibitor and a catechol-O-methyltransferase inhibitor. 22. The pharmaceutical composition according to claim 21, characterized in that said additional pharmacologically active agent is selected from: (a) amantadine; and/or (b) levodopa in combination with a DOPA decarboxylase inhibitor; and/or (c) a group consisting of carbidopa; benserazide; methyldopa; α-difluoromethyl-DOPA; 3',4',5,7-tetrahydroxy-8-methoxyisoflavone; apomorphine hydrochloride; bromocriptine; rotigotine; pramipexole; ropinirole; trihexylphenidyl; benztropine mesylate; safinamide; selegiline; rasagiline; entacapone; and tolcapone; and/or (d) the group consisting of beta-secretase inhibitors, gamma-secretase inhibitors, HMG-CoA reductase inhibitors, non-steroidal anti-inflammatory drugs (NSAIDs); and/or (E) groups consisting of an apason, aspirin, coxiba, diclofenac (together with or without a mizrostol), diplunizal, ethodolaca, phenoprofen, flurbprofen, ibuprofen, indomethacin, ketoprofen, meklofenamate of sodium, mephenamic acid, meloxicama, nabometeone, ok Saprozina , phenylbutazone, piroxicam, choline and magnesium salicylates, salsalate and sulindac; and/or (f) the group consisting of donepezil, rivastigmine, memantine and galantamine; and/or (g) the group consisting of sedatives, hypnotics, anxiolytics, antipsychotics and tranquilizers; and/or (h) the group consisting of amitriptyline, amoxapine, aripiprazole, asenapine, bupropion, chlordiazepoxide, citalopram, chlorpromazine, clozapine, desipramine, desvenlafaxine, doxepin, duloxetine, escitalopram, fluoxetine, fluphenazine, haloperidol, iloperidone, imipramine, sazide, lamotrigine, levomilnacipran , lurasidone, mirtazapine, nefazodone, nortriptyline, olanzapine, paliperidone, paroxetine, perphenazine, phenelzine, protriptyline, quetiapine, risperidone, safinamide, selegiline, sertraline, tranylcypromine, trazodone, trimipramine, venlafaxine, vilazodone, vortioxetine and ziprasidone; and/or (i) the group consisting of alprazolam, chlordiazepoxide, clobazepam, clonazepam, clorazepate, diazepam, estazolam, flurazepam, lorazepam, midazolam, oxazepam, prazepam, quazepam, temazepam and triazolam, hydroxyzine, eszopiclone, zaleplon, ema, zopiclone and buspirone; and/or (j) the group consisting of acetazolamide, carbamazepine, clobazam, clonazepam, eslicarbazepine acetate, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, nitrazepam, oxcarbazepine, perampanel, piracetam, phenobarbital, phenytoin, pregabalin, retigabine, rufinamide, sodium valproate , stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. 23. A kit having GPR6 modulator activity, wherein the kit is suitable for the treatment of Parkinson's disease and contains a pharmaceutical composition according to any one of claims. 15-19 and a pharmaceutical composition containing at least one additional pharmacologically active agent selected from the group consisting of levodopa, a DOPA decarboxylase inhibitor, a dopamine agonist, an anticholinergic agent, a selective monoamine oxidase B inhibitor and a catechol-O-methyltransferase inhibitor. 24. The kit according to claim 23, characterized in that said kit is suitable for administering a pharmaceutical composition according to any one of claims. 15-19 and a pharmaceutical composition containing at least one additional pharmacologically active agent simultaneously, sequentially or separately. 25. The kit according to claim 23 or 24, characterized in that said additional pharmacologically active agent is selected from: (a) amantadine; and/or (b) levodopa in combination with a DOPA decarboxylase inhibitor; and/or (c) a group consisting of carbidopa; benserazide; methyldopa; α-difluoromethyl-DOPA; 3',4',5,7-tetrahydroxy-8-methoxyisoflavone; apomorphine hydrochloride; bromocriptine; rotigotine; pramipexole; ropinirole; trihexylphenidyl; benztropine mesylate; safinamide; selegiline; rasagiline; entacapone; and tolcapone; and/or (d) the group consisting of beta-secretase inhibitors, gamma-secretase inhibitors, HMG-CoA reductase inhibitors, non-steroidal anti-inflammatory drugs (NSAIDs); and/or (E) groups consisting of an apason, aspirin, coxiba, diclofenac (together with or without a mizrostol), diplunizal, ethodolaca, phenoprofen, flurbprofen, ibuprofen, indomethacin, ketoprofen, meklofenamate of sodium, mephenamic acid, meloxicama, nabometeone, ok Saprozina , phenylbutazone, piroxicam, choline and magnesium salicylates, salsalate and sulindac; and/or (f) the group consisting of donepezil, rivastigmine, memantine and galantamine; and/or (g) the group consisting of sedatives, hypnotics, anxiolytics, antipsychotics and tranquilizers; and/or (h) the group consisting of amitriptyline, amoxapine, aripiprazole, asenapine, bupropion, chlordiazepoxide, citalopram, chlorpromazine, clozapine, desipramine, desvenlafaxine, doxepin, duloxetine, escitalopram, fluoxetine, fluphenazine, haloperidol, iloperidone, imipramine, sazide, lamotrigine, levomilnacipran , lurasidone, mirtazapine, nefazodone, nortriptyline, olanzapine, paliperidone, paroxetine, perphenazine, phenelzine, protriptyline, quetiapine, risperidone, safinamide, selegiline, sertraline, tranylcypromine, trazodone, trimipramine, venlafaxine, vilazodone, vortioxetine and ziprasidone; and/or (i) the group consisting of alprazolam, chlordiazepoxide, clobazepam, clonazepam, clorazepate, diazepam, estazolam, flurazepam, lorazepam, midazolam, oxazepam, prazepam, quazepam, temazepam and triazolam, hydroxyzine, eszopiclone, zaleplon, ema, zopiclone and buspirone; and/or (j) the group consisting of acetazolamide, carbamazepine, clobazam, clonazepam, eslicarbazepine acetate, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, nitrazepam, oxcarbazepine, perampanel, piracetam, phenobarbital, phenytoin, pregabalin, retigabine, rufinamide, sodium valproate , stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. 26. A dosage form having GPR6 modulator activity and containing an effective amount of a compound or pharmaceutically acceptable salt according to any one of claims. 1-14 and a pharmaceutically acceptable excipient, wherein the dosage form is for oral administration of the compound or a pharmaceutically acceptable salt thereof at a dose ranging from 0.5 to 5.0 mg/kg. 27. A method of treating a disease, disorder or condition associated with GPR6 in a subject, comprising administering to the subject an effective amount of a compound or pharmaceutically acceptable salt according to any one of claims. 1-14, or a pharmaceutical composition according to any one of paragraphs. 15-22, or set according to any one of paragraphs. 23-25, or the dosage form according to clause 26. 28. The method according to claim 27, characterized in that said disease, disorder or condition is selected from the group consisting of Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression. 29. The method of claim 27, wherein said disease, disorder or condition is Parkinson's disease. 30. The method of claim 29, wherein the treatment improves motor symptoms in the subject. 31. The method of claim 27, wherein said disease, disorder or condition is a non-motor clinical manifestation of Parkinson's disease. 32. The method of claim 27, wherein said compound or pharmaceutically acceptable salt is intended to be administered at a dose in the range of 0.5 to 5.0 mg/kg. 33. The method according to claim 27, characterized in that said compound or pharmaceutically acceptable salt is intended for oral administration. 34. Use of a compound or pharmaceutically acceptable salt according to any one of paragraphs. 1-14 or a pharmaceutical composition according to any one of paragraphs. 15-22, or set according to any one of paragraphs. 23-25, or the dosage form of claim 26 for the preparation of a medicament for treating a disease, disorder or condition associated with GPR6. 35. Use according to claim 34, characterized in that said disease, disorder or condition is selected from the group consisting of Parkinson's disease, levodopa-induced dyskinesias, Huntington's disease, drug addiction, eating disorders, cognitive impairment, schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, anxiety and depression. 36. The use of claim 34, wherein said disease, disorder or condition is Parkinson's disease. 37. The use of claim 36, wherein the treatment improves motor symptoms in the subject. 38. The use of claim 34, wherein said disease, disorder or condition is a non-motor clinical manifestation of Parkinson's disease. 39. Use according to claim 34, wherein the compound or pharmaceutically acceptable salt is intended to be administered at a dose in the range of 0.5 to 5.0 mg/kg. 40. Use according to claim 34, characterized in that the compound or pharmaceutically acceptable salt is intended for oral administration.

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