US20080139662A1

US20080139662A1 - Use of Sphingosine-1-Phosphate (S1P) Receptor Agonists For the Treatment of Brain Degenerative Diseases

Info

Publication number: US20080139662A1
Application number: US10/583,106
Authority: US
Inventors: Volker Brinkmann; Nicole Kaneider; Christian J. Wiedermann
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-12-19
Filing date: 2004-12-17
Publication date: 2008-06-12
Also published as: CA2792467A1; PT1713459E; CN101791406B; CN1893934A; CA2545503C; AU2004298760B2; ES2348569T3; EP2213285B1; RU2379030C2; KR20060103354A; KR101342244B1; EP2213285A2; DE602004028286D1; ES2444717T3; MXPA06006924A; KR101232934B1; EP1713459A2; ATE474569T1; BRPI0417203A; CA2545503A1

Abstract

Disclosed is the use of sphingosine-1-phosphate (S1P) receptor agonists, preferably 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol, in the treatment of progressive dementia or brain degenerative diseases.

Description

The present invention relates to a new use for a sphingosine-1-phosphate (S1P) receptor agonist, particularly in the treatment of progressive dementia or brain degenerative diseases.
S1P receptor agonists are compounds which signal as agonists at one or more sphingosine-1 phosphate receptors, e.g. S1P1 to S1P8. Agonist binding to a S1P receptor may e.g. result in dissociation of intracellular heterotrimeric G-proteins into Gα-GTP and Gβγ-GTP, and/or increased phosphorylation of the agonist-occupied receptor and activation of downstream signaling pathways/kinases, or to internalization/desensitization of the receptors as a result of super-agonism and consequently an antagonism of receptor signaling by the natural ligand S1P.
The binding affinity of S1P receptor agonists to individual human S1P receptors may be determined in following assay:
S1P receptor agonist activities of compounds are tested on the human S1P receptors S1P₁, S1P₃, S1P₂, S1P₄and S1P₅. Functional receptor activation is assessed by quantifying compound induced GTP [γ-³⁵S] binding to membrane protein prepared from transfected CHO or RH7777 cells stably expressing the appropriate human S1P receptor. The assay technology used is SPA (scintillation proximity based assay). Briefly, DMSO dissolved compounds are serially diluted and added to SPA-bead (Amersham-Pharmacia) immobilised S1P receptor expressing membrane protein (10-20 μg/well) in the presence of 50 mM Hepes, 100 mM NaCl, 10 mM MgCl₂, 10 μM GDP, 0.1% fat free BSA and 0.2 nM GTP [γ-³⁵S] (1200 Ci/mmol). After incubation in 96 well microtiterplates at RT for 120 min, unbound GTP [γ-³⁵S] is separated by a centrifugation step. Luminescence of SPA beads triggered by membrane bound GTP [γ-³⁵S] is quantified with a TOPcount plate reader (Packard). EC₅₀s are calculated using standard curve fitting software. In this assay, the S1P receptor agonists preferably have a binding affinity to S1P receptor <50 nM.
Internalization and desensitization of S1P receptors is determined using e.g. Chinese hamster ovary (CHO) cells transfected with a myc-tagged human S1P receptor. Internationalization of the receptor as a results of stimulation by agonists is determined by FACS analysis using fluorescently labeled anti-myc antibodies.
Preferred S1P receptor agonists are e.g. compounds which in addition to their S1P binding properties also have accelerating lymphocyte homing properties, e.g. compounds which elicit a lymphopenia resulting from a re-distribution, preferably reversible, of lymphocytes from circulation to secondary lymphatic tissue, without evoking a generalized immunosuppression. Naïve cells are sequestered; CD4 and CD8 T-cells and B-cells from the blood are stimulated to migrate into lymph nodes (LN) and Peyer's patches (PP).
The lymphocyte homing property may be measured in following Blood Lymphocyte Depletion assay:
A S1P receptor agonist or the vehicle is administered orally by gavage to rats. Tail blood for hematological monitoring is obtained on day −1 to give the baseline individual values, and at 2, 6, 24, 48 and 72 hours after application. In this assay, the S1P receptor agonist depletes peripheral blood lymphocytes, e.g. by 50%, when administered at a dose of e.g. <20 mg/kg. Preferred S1P receptor agonists are further compounds which in addition to their S1P binding properties internalize/desensitize S1P receptors, thereby antagonizing inflammatory processes driven by lysophospholipids, including i.e. sphingosine 1-phosphate (S1P), sphingophosphorylcholine (SPC), lysophosphatidic acid (LPA), and others, on vasculature cells, e.g. endothelial cells. The internalization/desensitization capacity of compounds will be determined using CHO cells transfected with a human myc-tagged S1P receptor.
Examples of appropriate S1P receptor agonists are, for example
Compounds as Disclosed in EP627406A1, e.g. a Compound of Formula I
wherein R₁is a straight- or branched (C_12-22)carbon chain

- which may have in the chain a bond or a hetero atom selected from a double bond, a triple bond, O, S, NR₆, wherein R₆is H, alkyl, aralkyl, acyl or alkoxycarbonyl, and carbonyl, and/or
  - which may have as a substituent alkoxy, alkenyloxy, alkynyloxy, aralkyloxy, acyl, alkylamino, alkylthio, acylamino, alkoxycarbonyl, alkoxycarbonylamino, acyloxy, alkylcarbamoyl, nitro, halogen, amino, hydroxyimino, hydroxy or carboxy; or

R₁is

- a phenylalkyl wherein alkyl is a straight- or branched (C_6-20)carbon chain; or
- a phenylalkyl wherein alkyl is a straight- or branched (C_1-30)carbon chain wherein said phenylalkyl is substituted by
- a straight- or branched (C_6-20)carbon chain optionally substituted by halogen,
- a straight- or branched (C_6-20)alkoxy chain optionally substituted by halogen,
- a straight- or branched (C_6-20)alkenyloxy,
- phenylalkoxy, halophenylalkoxy, phenylalkoxyalkyl, phenoxyalkoxy or phenoxyalkyl,
- cycloalkylalkyl substituted by C_6-20alkyl,
- heteroarylalkyl substituted by C_6-20alkyl,
- heterocyclic C_6-20alkyl or
- heterocyclic alkyl substituted by C_2-20alkyl,
  and wherein
  the alkyl moiety may have
- in the carbon chain, a bond or a heteroatom selected from a double bond, a triple bond, O, S, sulfinyl, sulfonyl, or NR₆, wherein R₆is as defined above, and
- as a substituent alkoxy, alkenyloxy, alkynyloxy, aralkyloxy, acyl, alkylamino, alkylthio, acylamino, alkoxycarbonyl, alkoxycarbonylamino, acyloxy, alkylcarbamoyl, nitro, halogen, amino, hydroxy or carboxy, and
  each of R₂, R₃, R₄and R₅, independently, is H, C_1-4alkyl or acyl
  or a pharmaceutically acceptable salt thereof;

Compounds as Disclosed in EP 1002792A1, e.g. a Compound of Formula II
wherein m is 1 to 9 and each of R′₂, R′₃, R′₄and R′₅, independently, is H, alkyl or acyl, or a pharmaceutically acceptable salt thereof;
Compounds as Disclosed in EP0778263 A1, e.g. a Compound of Formula III
wherein W is H; C_1-6alkyl, C_2-6alkenyl or C_2-6alkynyl; unsubstituted or by OH substituted phenyl; R″₄O(CH₂)_n; or C_1-6alkyl substituted by 1 to 3 substituents selected from the group consisting of halogen, C_3-8cycloalkyl, phenyl and phenyl substituted by OH;
X is H or unsubstituted or substituted straight chain alkyl having a number p of carbon atoms or unsubstituted or substituted straight chain alkoxy having a number (p−1) of carbon atoms, e.g. substituted by 1 to 3 substitutents selected from the group consisting of C_1-6alkyl, OH, C_1-6alkoxy, acyloxy, amino, C_1-6alkylamino, acylamino, oxo, haloC_1-6alkyl, halogen, unsubstituted phenyl and phenyl substituted by 1 to 3 substituents selected from the group consisting of C_1-6alkyl, OH, C_1-6alkoxy, acyl, acyloxy, amino, C_1-6alkylamino, acylamino, haloC_1-6alkyl and halogen; Y is H, C_1-6alkyl, OH, C_1-6alkoxy, acyl, acyloxy, amino, C_1-6alkylamino, acylamino, haloC_1-6alkyl or halogen, Z₂is a single bond or a straight chain alkylene having a number or carbon atoms of q,
each of p and q, independently, is an integer of 1 to 20, with the proviso of 6≦p+q≦23, m′ is 1, 2 or 3, n is 2 or 3,
each of R″₁, R″₂, R₁₃and R″₄, independently, is H, C_1-4alkyl or acyl,
or a pharmaceutically acceptable salt thereof,
Compounds as Disclosed in WO02/18395, e.g. a Compound of Formula IVa or IVb
wherein X_ais O, S, NR_1sor a group —(CH₂)_na—, which group is unsubstituted or substituted by 1 to 4 halogen; n_ais 1 or 2, R_1sis H or (C_1-4)alkyl, which alkyl is unsubstituted or substituted by halogen; R_1ais H, OH, (C_1-4)alkyl or O(C_1-4)alkyl wherein alkyl is unsubstituted or substituted by 1 to 3 halogen; R_1bis H, OH or (C_1-4)alkyl, wherein alkyl is unsubstituted or substituted by halogen; each R_2ais independently selected from H or (C_1-4)alkyl, which alkyl is unsubstituted or substituted by halogen; R_3ais H, OH, halogen or O(C_1-4)alkyl wherein alkyl is unsubstituted or substituted by halogen; and R_3bis H, OH, halogen, (C_1-4)alkyl wherein alkyl is unsubstituted or substituted by hydroxy, or O(C_1-4)alkyl wherein alkyl is unsubstituted or substituted by halogen; Y_ais —CH₂—, —C(O)—, —CH(OH)—, —C(═NOH)—, O or S, and R_4ais (C_4-14)alkyl or (C_4-14)alkenyl;
or a pharmaceutically acceptable salt or hydrate thereof;
Compounds as Disclosed in WO 02/076995, e.g. a Compound of Formula V
wherein

m_cis 1, 2 or 3;
X_cis O or a direct bond;
R_1cis H; C_1-6alkyl optionally substituted by OH, acyl, halogen, C_3-10cycloalkyl, phenyl or hydroxy-phenylene; C_2-6alkenyl; C_2-6alkynyl; or phenyl optionally substituted by OH;
R_2cis

- wherein R_5cis H or C_1-4alkyl optionally substituted by 1, 2 or 3 halogen atoms, and R_6cis H or C_1-4alkyl optionally substituted by halogen;
  each of R_3cand R_4c, independently, is H, C_1-4alkyl optionally substituted by halogen, or acyl, and
R_cis C_13-20alkyl which may optionally have in the chain an oxygen atom and which may optionally be substituted by nitro, halogen, amino, hydroxy or carboxy; or a residue of formula (a)

- wherein R_7cis H, C_1-4alkyl or C_1-4alkoxy, and R_8cis substituted C_1-20alkanoyl, phenylC_1-14alkyl wherein the C_1-14alkyl is optionally substituted by halogen or OH, cycloalkylC_1-14alkoxy or phenylC_1-14alkoxy wherein the cycloalkyl or phenyl ring is optionally substituted by halogen, C_1-4alkyl and/or C_1-4alkoxy, phenylC_1-14alkoxy-C_1-14alkyl, phenoxyC_1-14alkoxy or phenoxyC_1-14alkyl,
R_cbeing also a residue of formula (a) wherein R_8cis C_1-4alkoxy when R_1cis C_1-4alkyl, C_2-6alkenyl or C_2-6alkynyl,
or a compound of formula VI

wherein

n_xis 2, 3 or 4
R_1xis H; C_1-6alkyl optionally substituted by OH, acyl, halogen, cycloalkyl, phenyl or hydroxy-phenylene; C_2-6alkenyl; C₂alkynyl; or phenyl optionally substituted by OH;
R_2xis H, C_1-4alkyl or acyl
each of R_3xand R_4x, independently is H, C_1-4alkyl optionally substituted by halogen or acyl,
R_5xis H, C_1-4alkyl or C_1-4alkoxy, and
R_6xis C_1-20alkanoyl substituted by cycloalkyl; cyloalkylC_1-14alkoxy wherein the cycloalkyl ring is optionally substituted by halogen, C_1-4alkyl and/or C_1-4alkoxy; phenylC_1-14alkoxy wherein the phenyl ring is optionally substituted by halogen, C_1-4alkyl and/or C_1-4alkoxy,
R_6xbeing also C_4-14alkoxy when R_1xis C_2-4alkyl substituted by OH, or pentyloxy or hexyloxy when R_1xis C_1-4alkyl,
provided that R_6xis other than phenyl-butylenoxy when either R_5xis H or R_1xis methyl, or a pharmaceutically acceptable salt thereof;

Compounds as Disclosed in WO02/06268AI, e.g. a Compound of Formula VII
wherein each of R_1dand R_2d, independently, is H or an amino-protecting group;
R_3dis hydrogen, a hydroxy-protecting group or a residue of formula
R_4dis lower alkyl;
n_dis an integer of 1 to 6;
X_dis ethylene, vinylene, ethynylene, a group having a formula -D-CH₂— (wherein D is carbonyl, —CH(OH)—, O, S or N), aryl or aryl substituted by up to three substitutents selected from group a as defined hereinafter;
Y_dis single bond, C_1-10alkylene, C_1-10alkylene which is substituted by up to three substitutents selected from groups a and b, C_1-10alkylene having O or S in the middle or end of the carbon chain, or C_1-10alkylene having O or S in the middle or end of the carbon chain which is substituted by up to three substituents selected from groups a and b;
R_5dis hydrogen, cycloalkyl, aryl, heterocycle, cycloalkyl substituted by up to three substituents selected from groups a and b, aryl substituted by up to three substituents selected from groups a and b, or heterocycle substituted by up to three substituents selected from groups a and b;
each of R_6dand R_7d, independently, is H or a substituent selected from group a;
each of R_8dand R_9d, independently, is H or C_1-4alkyl optionally substituted by halogen;
<group a> is halogen, lower alkyl, halogeno lower alkyl, lower alkoxy, lower alkylthio, carboxyl, lower alkoxycarbonyl, hydroxy, lower aliphatic acyl, amino, mono-lower alkylamino, di-lower alkylamino, lower aliphatic acylamino, cyano or nitro; and
<group b> is cycloalkyl, aryl, heterocycle, each being optionally substituted by up to three substituents selected from group a;
with the proviso that when R_5dis hydrogen, Y_dis a either a single bond or linear C_1-10alkylene, or a pharmacologically acceptable salt or ester thereof;
Compounds as Disclosed in JP-14316985 (JP2002316985), e.g. a Compound of Formula VIII:
wherein R_1e, R_2e, R_3e, R_4e, R_5e, R_6e, R_7e, n_e, X_eand Y_eare as disclosed in JP-14316985; or a pharmacologically acceptable salt or ester thereof;
Compounds as Disclosed in WO 03/29184 and WO 03/29205, e.g. compounds of formula IX
wherein X_fis O or S, and R_1f, R_2f, R_3fand n_fare as disclosed in WO 03/29184 and O3/29205, each of R_4fand R_5f, independently is H or a residue of formula
wherein each of R_8fand R_9f, independently, is H or C_1-4alkyl optionally substituted by halogen; e.g. 2-amino-2-[4-(3-benzyloxyphenoxy)-2-chlorophenyl]propyl-1,3-propane-diol or 2-amino-2-[4-(benzyloxyphenylthio)-2-chlorophenyl]propyl-1,3-propane-diol, or a pharmacological salt thereof;
Compounds as Disclosed in WO03/062252A1, e.g. a Compound of Formula X
wherein
Ar is phenyl or naphthyl; each of m_gand n_gindependently is 0 or 1; A is selected from COOH, PO₃H₂, PO₂H, SO₃H, PO(C_1-3alkyl)OH and 1H-tetrazol-5-yl; each of R_1gand R_2gindependently is H, halogen, OH, COOH or C_1-4alkyl optionally substituted by halogen; R_3gis H or C_1-4alkyl optionally substituted by halogen or OH; each R_4gindependently is halogen, or optionally halogen substituted C_1-4alkyl or C_1-3alkoxy; and each of R_gand M has one of the significances as indicated for B and C, respectively, in WO03/062252A1;
Compounds as Disclosed in WO 03/062248A2, e.g. a Compound of Formula XI
wherein Ar is phenyl or naphthyl; n is 2, 3 or 4; A is COOH, 1H-tetrazol-5-yl, PO₃H₂, PO₂H₂, —SO₃H or PO(R_5h)OH wherein R_5his selected from C_1-4alkyl, hydroxyC_1-4alkyl, phenyl, —CO—C_1-3alkoxy and —CH(OH)-phenyl wherein said phenyl or phenyl moiety is optionally substituted; each of R_1hand R_2hindependently is H, halogen, OH, COOH, or optionally halogeno substituted C_1-6alkyl or phenyl; R_3his H or C_1-4alkyl optionally substituted by halogen and/OH; each R_4hindependently is halogeno, OH, COOH, C_1-4alkyl, S(O)_{0,1 or2}C_1-3alkyl, C_1-3alkoxy, C_3-6cycloalkoxy, aryl or aralkoxy, wherein the alkyl portions may optionally be substituted by 1-3 halogens; and each of R_gand M has one of the significances as indicated for B and C, respectively, in WO03/062248A2;
Compounds as Disclosed in WO 04/026817, e.g. a Compound of Formula XII
wherein R_1jis halogen, trihalomethyl, C_1-4alkyl, C_1-4alkoxy, C_1-4alkylthio, aralkyl, or optionally substituted phenoxy or aralkyloxy, R_2jis H, halogen, trihalomethyl, C_1-4alkyl, C_1-4alkoxy, aralkyl or aralkyloxy, R_3jis H, halogen, trifluoromethyl, C_1-4alkyl, C_1-4alkoxy, C_1-4alkylthio or benzyloxy, R_4jis H, C_1-4alkyl, phenyl, benzyl optionally substituted, lower aliphatic acyl having 1 to 5 C or benzoyl optionally substituted, R_5jis H, monohalomethyl, C_1-4alkyl, C_1-4alkoxy, C_1-4alkylthio, hydroxyethyl, hydroxypropyl, phenyl, aralkyl, C_2-4alkenyl or C_2-4alkynyl, each of R_6jand R_7j, independently is H or C_1-4alkyl, X_jis O, S, SO or SO₂and n_jis 1, 2, 3 or 4, or a pharmaceutically acceptable salt thereof;
According to a further embodiment of the invention, a S1P receptor agonist for use in a combination of the invention may also be a selective S1P1 receptor, e.g. a compound which possesses a selectivity for the S1P1 receptor over the S1P3 receptor of at least 20 fold, e.g. 100, 500, 1000 or 2000 fold, as measured by the ratio of EC₅₀for the S1P1 receptor to the EC₅₀for the S1P3 receptor as evaluated in a ³⁵S-GTPγS binding assay, said compound having an EC₅₀for binding to the S1P1 receptor of 100 nM or less as evaluated by the ³⁵S-GTPγS binding assay. Representative S1P1 receptor agonists are e.g. the compounds listed in WO 03/061567, the contents of which being incorporated herein by reference, for instance a compound of formula
When the compounds of formulae I to XIV have one or more asymmetric centers in the molecule, the present invention is to be understood as embracing the various optical isomers, as well as racemates, diastereoisomers and mixtures thereof are embraced.
Compounds of formula III or IVb, when the carbon atom bearing the amino group is asymmetric, have preferably the R-configuration at this carbon atom.
The compounds of formulae I to XIV may exist in free or salt form. Examples of pharmaceutically acceptable salts of the compounds of the formulae I to XIII include salts with inorganic acids, such as hydrochloride, hydrobromide and sulfate, salts with organic acids, such as acetate, fumarate, maleate, benzoate, citrate, malate, methanesulfonate and benzenesulfonate salts, or, when appropriate, salts with metals such as sodium, potassium, calcium and aluminium, salts with amines, such as triethylamine and salts with dibasic amino acids, such as lysine. The compounds and salts of the combination of the present invention encompass hydrate and solvate forms.
In each case where citations of patent applications are given, the subject matter relating to the compounds is hereby incorporated into the present application by reference.
Acyl may be a residue R_y—CO— wherein R_yis C_1-6alkyl, C_3-6cycloalkyl, phenyl or phenyl-C_1-4alkyl. Unless otherwise stated, alkyl, alkoxy, alkenyl or alkynyl may be straight or branched.
When in the compounds of formula I the carbon chain as R₁is substituted, it is preferably substituted by halogen, nitro, amino, hydroxy or carboxy. When the carbon chain is interrupted by an optionally substituted phenylene, the carbon chain is preferably unsubstituted. When the phenylene moiety is substituted, it is preferably substituted by halogen, nitro, amino, methoxy, hydroxy or carboxy.
Preferred compounds of formula I are those wherein R₁is C_13-20alkyl, optionally substituted by nitro, halogen, amino, hydroxy or carboxy, and, more preferably those wherein R₁is phenylalkyl substituted by C_6-14-alkyl chain optionally substituted by halogen and the alkyl moiety is a C_1-6alkyl optionally substituted by hydroxy. More preferably, R₁is phenyl-C_1-6alkyl substituted on the phenyl by a straight or branched, preferably straight, C_6-14alkyl chain. The C_6-14alkyl chain may be in ortho, meta or para, preferably in para.
Preferably each of R₂to R₅is H.
A preferred compound of formula I is 2-amino-2-tetradecyl-1,3-propanediol. A particularly preferred S1P receptor agonist of formula I is FTY720, i.e. 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in free form or in a pharmaceutically acceptable salt form (referred to hereinafter as Compound A), e.g. the hydrochloride, as shown:
A preferred compound of formula II is the one wherein each of R′₂to R′₅is H and m is 4, i.e. 2-amino-2-{2-[4-(1-oxo-5-phenylpentyl)phenyl]ethyl}propane-1,3-diol, in free form or in pharmaceutically acceptable salt form (referred to hereinafter as Compound B), e.g the hydrochloride.
A preferred compound of formula III is the one wherein W is CH₃, each of R″₁to R″₃is H, Z₂is ethylene, X is heptyloxy and Y is H, i.e. 2-amino-4-(4-heptyloxyphenyl)-2-methyl-butanol, in free form or in pharmaceutically acceptable salt form (referred to hereinafter as Compound C), e.g. the hydrochloride. The R-enantiomer is particularly preferred.
A preferred compound of formula IVa is the FTY720-phosphate (R_2ais H, R_3ais OH, X_ais O, R_1aand R_1bare OH). A preferred compound of formula IVb is the Compound C-phosphate (R_2ais H, R_3bis OH, X_ais O, R_1aand R_1bare OH, Y_ais O and R_4ais heptyl). A preferred compound of formula V is Compound B-phosphate.
A preferred compound of formula V is phosphoric acid mono-[(R)-2-amino-2-methyl-4-(4-pentyloxy-phenyl)-butyl]ester.
A preferred compound of formula VIII is (2R)-2-amino-4-[3-(4-cyclohexyloxybutyl)-benzo[b]thien-6-yl]-2-methylbutan-1-ol.
Preferred compounds of formula XII are those wherein R_1jis CF₃or benzyloxy and R_6jis H
Compounds of formulae I to XIV have, on the basis of observed activity, e.g. as described in EP-A1-627,406, been found to be useful e.g. as immunosuppressants, e.g. in the treatment of acute allograft rejection or autoimmune disorders.
Brain degenerative diseases are becoming more common in developed nations as the population includes more and more older persons. There is no known cause for the diseases. It is not known why some people present as early as 30 or 40 years of age with dementia while others do not present until their late 70's or 80's. Alzheimer disease is a progressive degenerative disease of the brain characterized by the insidious onset of dementia. Impairment of memory, judgment, attention span, and problem solving skills are followed by global loss of cognitive abilities. There remains a medical need for agents which are effective in the treatment of such diseases and disorders, e.g. in reducing or preventing disease progression and/or alleviating the symptoms and/or improving quality of life. It has now been found that S1P receptor agonists have interesting properties which make them useful for treating progressive dementia and brain degeneration.
In accordance with the particular findings of the present invention, there is provided:
1.1 A method for treating progressive dementia or brain degeneration in a subject in need thereof, comprising administering to said subject a therapeutically effective amount of a sphingosine-1-phosphate (S1P) receptor agonist, e.g. a compound of formula I or a pharmaceutically acceptable salt thereof.
1.2 A method for treating β-amyloid-related inflammatory diseases or disorders in a subject in need thereof, comprising administering to said subject a therapeutically effective amount of a sphingosine-1-phosphate (S1P) receptor agonist, e.g. a compound of formula I or a pharmaceutically acceptable salt thereof.
Examples of such diseases and disorders are e.g. Alzheimer disease, amyloidosis, Lewy Body diseases, Multi-Infarct dementia, Pick's disease or cerebral atherosclerosis.
1.3 A method for reducing or inhibiting loss of cognitive abilities in a subject in need thereof, comprising administering to said subject a therapeutically effective amount of a sphingosine-1-phosphate (S1P) receptor agonist, e.g. a compound of formula I or a pharmaceutically acceptable salt thereof.
2. A sphingosine-1-phosphate (S1P) receptor agonist, e.g. a compound of formula I, or a pharmaceutically acceptable salt thereof for use in the preparation of a pharmaceutical composition for use in any method as defined under 1.1 to 1.3 above.
3. A pharmaceutical composition for use in any method as defined under 1.1 to 1.3 above comprising a sphingosine-1-phosphate (S1P) receptor agonist, e.g. a compound of formula I or a pharmaceutically acceptable salt thereof together with one or more pharmaceutically acceptable diluents or carriers therefor.
Preferably the progressive dementia or brain degeneration is other than senile dementia.
Utility of the sphingosine-1-phosphate (S1P) receptor agonists, e.g. a compound of formula I, in treating diseases as hereinabove specified, may be demonstrated in animal test methods as well as in clinic, for example in accordance with the methods hereinafter described.
A.1 Peripheral blood mononuclear cells are prepared from peripheral venous blood of healthy volunteers (anticoagulated with EDTA). After Lymphoprep® density gradient centrifugation, peripheral blood mononuclear cells are collected and washed three times with normal saline. Positive selection of monocytes is performed by adding MACS colloidal superparamagnetic microbeads conjugated with monoclonal anti-human CD14 antibodies to cooled, freshly prepared peripheral blood mononuclear cell preparations in MACS buffer (PBS with 5 mM EDTA and 0.5% bovine serum albumin) according to the manufacturer's instructions. Cells and microbeads are incubated for 15 min at 4-6° C. In the meantime the separation column is positioned in the MACS magnetic field and washed with MACS buffer at room temperature. The cells are washed with MACS buffer, resuspended, and loaded onto the top of the separation column. The eluent containing CD14 cells is withdrawn and after removal of the column from the magnet, trapped monocytes (CD14⁺) are eluted with the sixfold amount of cold MACS buffer, centrifuged, and resuspended in medium containing 0.5% BSA. By immunocytochemistry, preparations yield a purity of approximately 98%.

Chemotaxis Assay

Leukocyte migration is measured using a modified 48-blindwell microchemotaxis chamber equipped with 5 μm pore-sized nitrocellulose filters for monocyte chemotaxis. In some experiments cells are incubated for 20 min with GFX [500 nM], staurosporine [10 ng/mL], tyrphostin-23 [10 ng/mL], wortmannin [10 nM], cholera toxin [1 nM], DMS [20 pg/mL to 20 μg/mL] or pertussis toxin [1 nM]. For determination of Aβ's potency to affect monocyte chemotaxis toward fMLP, cells with Aβ [1 aM to 1 μM] are incubated for 20 min. After washing twice, 50 μl of cell suspension [1×10⁶cells/mL] is put into the upper compartment of the chemotaxis chamber and cells are allowed to migrate for 90 min toward fMLP. After these migration periods the filters are dehydrated, fixed and stained with haematoxylin-eosin. Migration depth is quantified by microscopy, the distance from the surface of the filter to the leading front of three cells being measured. Data are expressed as “chemotaxis index”, which is the ratio between the distance of directed and undirected migration.

Semiquantitative RT-PCR

Total RNA is isolated from 8×10⁶cells by phenol-chloroform-isoamylalcohol extraction (RNAClean™; Hybaid-AGS, Ulm, Germany). Reverse transcriptase reaction is performed on 1 μg of RNA using random hexamers reverse transcriptase (Gibco BRL, Life Technologies, Vienna, Austria). 10 μL of the reverse transcriptase reaction mixture is then subjected to 35 cycles of PCR in a 50 μL reaction mixture containing 1 pmol of sense and anti-sense primer pairs in a Perkin-Elmer thermocycler: 95° C.—30 sec (denaturation), 53° C.—60 sec (annealing), 72° C.—30 sec (extension). Hot Start Taq polymerase is from Qiagen Inc. (Valencia, Calif., USA). Primers (MWG Biotech, Ebersdorf, Germany) are designed to amplify about 400 bp coding sequences of the receptors. Primers are designed as follows: Sphingosine-1-phosphate receptor (S1PR) 1 sense: CTG TGA ACA ATG CAC TGG, anti-sense: CCT ACG TAC TCA ACA TAG CC. S1PR 3 sense: ATC TGC AGC TTC ATC GTC, anti-sense: AGA TTG AGG CAG TTC. S1PR 2 sense: ACC ACG CAC AGC ACA TAA TG, anti-sense: AAA CAG CAA GTT CCA CTC GG. S1PR 4 sense: TGA ACA TCA CGC TGA GTG, anti-sense: ATC ATC AGC ACC GTC TTC. S1PR 5 sense: GAA ATG CAG CCA AAG GTG, anti-sense: TT ATC ACC CAC AAG GTC CTT C. The PCR products are subjected to agarose gel analysis.

Results

Aβ- and Aβ Precursor Protein-Induced Chemotaxis.

To confirm that Aβ induces monocyte chemotaxis and to investigate whether Aβ precursor protein (Aβ-PP) is able to act comparably, monocytes are allowed to migrate toward different concentrations of Aβ [10 nmol/L to 1 μmol/L] or Aβ-PP [10 nmol/L to 1 μmol/L] for 90 min. Directed migration of monocytes is measured using a modified 48-blindwell microchemotaxis chamber equipped with 5 μm pore-sized nitrocellulose filters for monocyte chemotaxis. Migration depth is quantified by microscopy, measuring the distance from the surface of the filter to the leading front of three cells. Data are expressed as “chemotaxis index”, which is the ratio between the distance of directed and undirected migration. Mean distance of undirected migration was 57±4.5 μm. Results confirm that Aβ induces chemotaxis in human monocytes with a maximum response at 1 pmol/L. Aβ-PP induces chemotaxis in a concentration-dependent manner, with the maximal response also at 1 pM.

Inhibition of Aβ and Aβ-Precursor Protein-Induced Monocyte Migration by Neuropeptides.

To delineate whether monocyte attracting neuropeptides influence Aβ- and Aβ-PP-induced monocyte locomotion, cells are exposed to neuropeptides, e.g. bombesin, CGRP, SP, SN or VIP and chemotaxis toward Aβ and Aβ-PP is tested as described above. All neuropeptides inhibit chemotaxis concentration-dependently.

Signaling Enzyme Inhibitors Affect Aβ-Induced Migration

Monocytes are incubated with several enzyme blockers. The protein kinase C inhibitor GFX, the tyrosine kinase inhibitor tyrphostin-23, and the phospholipase-3 inhibitor WTN are used first for blocking signaling enzymes; involvement of G proteins is then tested with PTX which is known to induce Gi proteins, and CTX which induces Gs proteins. After washing, chemotaxis experiments toward Aβ(1 pmol/l) and Aβ-PP (1 pmol/l) are performed. Data are expressed as chemotaxis index, which is the ratio between directed and random migration. Mean distance of random migration is 54±3.2 μm.

	TABLE 1

	Chemotaxis Index

Treatment	Aβ Mean (+/− SEM)	Aβ-PP Mean (+/− SEM)

Medium	1.786 (0.078)	1.639 (0.076)
GFX (500 nmol/l)	1.143 (0.08)	1.098 (0.10)
IBMX (10 ng/ml)	1.234 (0.06)	1.208 (0.09)
Tyrphostin-23	1.435 (0.04)	1.398 (0.07)
(10 ng/ml)
WTN (10 nmol/l)	1.023 (0.05)	1.115 (0.08)
CTX (1 nmol/l)	1.768 (0.10)	1.790 (0.13)
PTX (1 nmol/l)	1.098 (0.08)	1.123 (0.06)

N,N-dimethylsphingosine Inhibits Aβ- and Aβ-PP-Induced Monocyte Migration

Human monocytes are pre-treated with the selective sphingosine kinase inhibitor, DMS, at different concentrations (e.g. 100 fmol/l to 100 nmol/l). fMLP is used as a control attractant. Treatment with DMS inhibits Aβ- and Aβ-PP-induced chemotaxis, whereas fMLP-induced chemotaxis is not affected.

S1P Receptor Agonist Deactivates Migration of Human Monocytes Toward Aβ and Chemokines

Monocytes are incubated with DMS, Compound A or medium for 20 min. After washing, chemotaxis experiments toward Aβ [1 pmol/L] are performed. Data are expressed as chemotaxis index, which is the ratio between directed and random migration. Mean distance of random migration is 56±5.6 μm. DMS and a S1P receptor agonist alone inhibit the migration of the cells, whereas co-treatment with both restores the chemotactic effect of Aβ and Aβ-PP. Results with Compound A are as follows:
TABLE 2

Chemotaxis

Treatment Mean (+/− SEM)

Medium 1.825 (0.14)

DMS (2 ng/ml) 1.423 (0.18)

Compound A (2 ng/ml) 1.077 (0.18)

S1P Receptor mRNA Expression is Regulated by Aβ
After pretreatment with Compound A at various concentrations [20 pg/mL to 20 μg/mL] for 20 min, cells are washed and chemotaxis toward Aβ and Aβ-PP [1 pM] is tested as described above. Data are expressed as chemotaxis index, which is the ratio between directed and undirected migration of cells. After the incubation period, RT-PCR is performed and equal amounts of cDNA are subjected to agarose gel electrophoresis. Induction of S1PR 2 and S1PR 5 mRNA in Aβ-treated cells is observed.

B. Clinical Trial

The trial is carried out employing groups comprising 6 to 10 subjects identified as exhibiting mild to moderate Alzheimer dementia in accordance with parameters defined in DSM-III (Diagnostic and Statistical Manual of Mental Disorders, 3rd edition) and excluding subjects exhibiting severe cardiovascular disease, hypotension, severe endocrine disease, severe liver disease, renal insufficiency. The trial commences with an EEG and psychometric test at time 0. Subjects then receive placebo, or test medication administered as described below, and the EEG and psychometric tests are repeated 60, 120 and 180 minutes subsequent to administration. Psychometric tests employed include:

(i) The Selective Reminding Test/Buschke: “Selective Reminding for Analysis of Memory and Learning”, J. Verbal Learning and Verbal Behaviour 12, 543-550 (1973);

(ii) Measurement of Constructional Ability (Muratomo et al.: “Effect of Physiostigmin on Constructional and Memory Tasks in Alzheimer's disease”, Arch. Neurol. 36, 501-503 (1973); and
(iii) Memory of Geometric Figures (Benton revised visual retention test).
During the course of the trial, subjects receive either a placebo or a S1P receptor agonist, e.g. Compound A, at dosages of from ca. 0.25 to ca. 10 mg/p.o. administered once or in divided dosages 2 or 3×.
The following additional parameters are monitored:

- Haematology: R.B.C., HB, HCT, W.B.C, differential counts, sedimentation rate, blood glucose.
- Urine: Albumin, glucose.
- Serum: Alkaline phosphatase, ALT, AST, S-GT, S-bilirubin, S-T4, S-T3, S-TSH, creatinin.

Subjects receiving a S1P receptor agonist, e.g. Compound A, in the above indicated dosages exhibit improved condition as evidenced by EEG results and the results of psychometric tests as compared with subjects receiving placebo.
Daily dosages required in practicing the method of the present invention when S1P receptor agonist is used will vary depending upon, for example, the compound used, the host, the mode of administration and the severity of the condition to be treated. A preferred daily dosage range is about from 0.1 to 100 mg as a single dose or in divided doses. Suitable daily dosages for patients are on the order of from e.g. 0.1 to 50 mg p.o. The S1P receptor agonist may be administered by any conventional route, in particular enterally, e.g. orally, e.g. in the form of tablets, capsules, drink solutions, nasally, pulmonary (by inhalation) or parenterally, e.g. in the form of injectable solutions or suspensions. Suitable unit dosage forms for oral administration comprise from ca. 0.1 to 30 mg, usually 0.25 to 30 mg S1P receptor agonist, e.g. Compound A, together with one or more pharmaceutically acceptable diluents or carriers therefor.
The S1P receptor agonist may be administered by any conventional route, in particular enterally, e.g. orally, for example in the form of solutions for drinking, tablets or capsules or parenterally, for example in the form of injectable solutions or suspensions, or topically. Pharmaceutical compositions comprising a S1P receptor agonist, e.g. a compound of formula I may be manufactured in conventional manner, e.g. as described in EP-A1-627,406 or in EP-A1-1,002,792.
The S1P receptor agonists may be administered as the sole ingredient or together with other drugs useful in the alleviation or treatment of brain degenerative diseases or progressive dementia, e.g. an AMPA receptor agonist, a noortropic agent, a painkiller or an anti-inflammatory agent.
The term “AMPA receptor antagonist” as used herein includes, but is not limited to an quinoxaline-dione aminoalkylphosphonate, e.g. as disclosed in WO 98/17672, or to further compounds such as EGIS 8332 (7-acetyl-5-(4-aminophenyl)-8,9-dihydro-8-methyl-7H-1,3-dioxolo[4,5-h][2,3]benzodiazepine-8-carbonitrile), GYKI 47261 4-(7-chloro-2-methyl-4H-3,10,10a-triaza-benzo[f]azulen-9-yl)-phenylamine), irampanel (BIIR 561; N,N-dimethyl-2-[2-(3-phenyl-1,2,4-oxadiazol-5-yl)phenoxy]ethanamine), KRP 199 (7-[4-[[[[(4-carboxyphenyl)-amino]carbonyl]oxy]methyl]-1H-imidazol-1-yl]-3,4-dihydro-3-oxo-6-(trifluoromethyl)-2-quinoxalinecarboxylic acid), NS 1209 (2-[[[5-[4-[(dimethylamino)-sulfonyl]phenyl]-1,2,6,7,8,9-hexahydro-8-methyl-2-oxo-3H-pyrrolo[3,2-h]isoquinolin-3-ylidene]amino]oxy]-4-hydroxybutanoic acid monosodium salt, e.g. prepared as described in WO 98/14447), topiramate (TOPAMAX, 2,3:4,5-bis-O-(1-methylethylidene)-beta-D-fructopyranose sulfamate, preparation, e.g. as described in U.S. Pat. No. 535,475) and talampanel (LY-300164, (R)-7-acetyl-5-(4-aminophenyl)-8,9-dihydro-8-methyl-7H-1,3-dioxolo[4,5-h][2,3]benzo-diazepine, preparation, e.g. as described in EP 492485), YM90K (6-imidazol-1-yl-7-nitro-1,4-dihydro-quinoxaline-2,3-dione), S-34730 (7-chloro-6-sulfamoyl-2-(1H)-quinolinone-3-phosphonic acid), Zonampanel (YM-872; (7-imidazol-1-yl-6-nitro-2,3-dioxo-3,4-dihydro-2H-quinoxalin-1-yl)-acetic acid), GYKI-52466 (4-(8-methyl-9H-1,3-dioxa-6,7-diaza-cyclohepta[f]inden-5-yl)-phenylamine), ZK-200775 (MPQX, (7-morpholin-4-yl-2,3-dioxo-6-trifluoromethyl-3,4-dihydro-2H-quinoxalin-1-ylmethyl)-phosphonic acid), CP-465022 (3-(2-chloro-phenyl)-2-[2-(6-diethylaminomethyl-pyridin-2-yl)-vinyl]-6-fluoro-3H-quinazolin-4-one), SYM-2189 (4-(4-amino-phenyl)-6-methoxy-1-methyl-1H-phthalazine-2-carboxylic acid propylamide), SYM-2206 (8-(4-amino-phenyl)-5-methyl-5H-[1,3]dioxolo[4,5-g]phthalazine-6-carboxylic acid propylamide, RPR-117824 ((4-oxo-2-phosphono-5,10-dihydro-4H-imidazo[1,2-a]indeno[1,2-e]pyrazin-9-yl)-acetic acid), LY-293558 (6-[2-(1H-tetrazol-5-yl)-ethyl]-decahydro-isoquinoline-3-carboxylic acid).
The term “nootropics” as used herein includes, but is not limited to nootropical plant extracts, calcium antagonists, cholinesterase inhibitors, dihydroergotoxin, nicergoline, piracetame, purine derivates, pyritinol, vincamine and vinpocetine. The term “nootropical plant extracts” as used herein includes, but is not limited to extracts from Ginkgo leafs. The term “calcium antagonists” as used herein includes, but is not limited to cinnarizine and nimodipine. The term “cholinesterase inhibitors” as used herein includes, but is not limited to donepezil hydrochloride, rivastigmine and galantamine hydrobromide. The term “purine derivates” as used herein includes, but is not limited, to pentifyllin. A painkiller as used herein includes, but is not limited, to ibuprofen. A suitable anti-inflammatory agent is e.g. a NSAIDs, e.g. naproxen.
Extracts from Ginkgo leafs can be administered, e.g., in the form as marketed, e.g. under the trademark Ginkodilat™ according to the information provided by the package insert. Cinnarizine can be administered, e.g., in the form as marketed, e.g. under the trademark Cinnarizin Forte-Ratiopharm™. Nimodipine can be administered, e.g., in the form as marketed, e.g. under the trademark Nimotop™. Donepezil hydrochloride can be administered, e.g., in the form as marketed, e.g. under the trademark Aricept™. Rivastigmine can be prepared as disclosed in U.S. Pat. No. 5,602,176. It can be administered, e.g., in the form as marketed, e.g. under the trademark Exelon™. Galantamine hydrobromide can be administered, e.g., in the form as marketed, e.g. under the trademark Reminyl™. Dihydroergotoxin can be administered, e.g., in the form as marketed, e.g. under the trademark Hydergin™. Nicergoline can be administered, e.g., in the form as marketed, e.g. under the trademark Sermion™. Piracetam can be administered, e.g., in the form as marketed, e.g. under the trademark Cerebrofortem. Pentifyllin can be administered, e.g., in the form as marketed, e.g. under the trademark Cosaldon™. Pyritinol can be administered, e.g., in the form as marketed, e.g. under the trademark Encephabol™. Vinpocetin can be administered, e.g., in the form as marketed, e.g. under the trademark Cavinton™.
The structure of the active ingredients identified by code nos., generic or trade names mentioned herein may be taken from the actual edition of the standard compendium “The Merck Index” or from databases, e.g. Patents International (e.g. IMS World Publications). The corresponding content thereof is hereby incorporated by reference. Any person skilled in the art is fully enabled to identify the active ingredients and, based on these references, likewise enabled to manufacture.
Where the S1P receptor agonists are administered in conjunction with other drugs, dosages of the co-administered compound will of course vary depending on the type of co-drug employed, on the specific drug employed, on the condition to be treated, and so forth. The terms “co-administration” or “combined administration” or the like as utilized herein are meant to encompass administration of the selected therapeutic agents to a single patient, and are intended to include treatment regimens in which the agents are not necessarily administered by the same route of administration or at the same time.
In accordance with the foregoing the present invention provides in a yet further aspect:

5. A pharmaceutical combination comprising a) a first agent which is a S1P receptor agonist, e.g. a compound of formula I, e.g. Compound A, or a pharmaceutically acceptable salt thereof, and b) a co-agent, e.g. a second drug agent as defined above.
6. A method as defined above comprising co-administration, e.g. concomitantly or in sequence, of a therapeutically effective amount of a S1P receptor agonist, e.g. a compound of formula I, e.g. Compound A, or a pharmaceutically acceptable salt thereof, and a second drug substance, e.g. as indicated above.

S1P receptor agonists are well tolerated at dosages required for use in accordance with the present invention. For example, Compound A has an acute LD₅₀>10 mg/kg p.o. in rats and monkeys.

Claims

1-3. (canceled)

4. A pharmaceutical composition for use in treating progressive dementia or brain degeneration, R-amyloid-related inflammatory diseases or disorders or for reducing or inhibiting loss of cognitive abilities comprising a sphingosine-1-phosphate (S1P) receptor agonist or a pharmaceutically acceptable salt thereof together with one or more pharmaceutically acceptable diluents or carriers therefore.

5. A pharmaceutical combination comprising a) a first agent which is a S1P receptor agonist or a pharmaceutically acceptable salt thereof and b) a co-agent useful in the alleviation or treatment of brain degenerative diseases or progressive dementia.

6. A combination according to claim 5, wherein co-agent b) is selected from an AMPA receptor agonist, a noortropic or anti-inflammatory agent or a painkiller.

7. A method for treating progressive dementia or brain degeneration or β-amyloid-related inflammatory diseases or disorders or for reducing or inhibiting loss of cognitive abilities in a subject in need thereof, comprising administering to said subject a therapeutically effective amount of a sphingosine-1-phosphate (S1P) receptor agonist or a pharmaceutically acceptable salt thereof.

8. A method according to claim 7 comprising co-administration, e.g. concomitantly or in sequence, of b) a co-agent useful in the alleviation or treatment of brain degenerative diseases or progressive dementia.

9. A composition, according to claim 4, wherein the S1P receptor agonist is compound of formula I

wherein R₁is straight- or branched (C_12-22)carbon chain

which may have in the claim a bond or a hetero atom selected from a double bond, a triple bond, O, S, NR₆, wherein R₆is H, alkyl, aralkyl, acyl or alkoxycarbonyl, and carbonyl, and/or

which may have as a substituent alkoxy, alkenyloxy, alkynyloxy, aralkyloxy, acyl, alkylamino, alkylthio, acylamino, alkoxycarbonyl, alkoxycarbonylamino, acyloxy, alkylcarbamoyl, nitro, halogen, amino, hydroxyimino, hydroxyl or carboxy; or

R₁is

a phenylalkyl wherein alkyl is a straight- or branched (C_6-20)carbon chain; or

a phenylalkyl wherein alkyl is a straight- or branched (C_1-30)carbon chain wherein said phenylalkyl is substituted by

a straight- or branched (C_6-20)carbon chain optionally substituted by halogen,

a straight- or branched (C_6-20)alkoxy chain optionally substituted by halogen,

a straight- or branched (C_6-20)alkenyloxy,

phenylalkoxy, halophenylalkoxy, phenylalkoxyalkyl, phenoxyalkoxy or phenoxyalkyl,

cycloalkylalkyl substituted by C_6-20alkyl,

heteroarylalkyl substituted by C_6-20alkyl,

heterocyclic C_6-20alkyl or

heterocyclic alkyl substituted by C_6-20alkyl,

and wherein

the alkyl moiety may have

in the carbon chain, a bond or a heteroatom selected from a double bond, a triple bond, O, S, sulfinyl, sulfonyl, or NR₆, wherein R₆is as defined above, and

as a substituent alkoxy, alkenyloxy, alkynyloxy, aralkyloxy, acyl, alkylamino, alkylthio, acylamino, alkoxycarbonyl, alkoxycarbonylamino, acyloxy, alkylcarbamoyl, nitro, halogen, amino, hydroxyl or carboxy, and

each of R₂, R₃, R₄and R₅, independently, is H, C_1-4alkyl or acyl

or a pharmaceutically acceptable salt thereof.

10. A composition, according to claim 9, wherein the S1P receptor agonist is 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in free form or in a pharmaceutically acceptable salt form.

11. A combination according to claim 5, wherein the S1P receptor agonist is compound of formula I

wherein R₁is straight- or branched (C_12-22)carbon chain

which may have in the cain a bond or a hetero atom selected from a double bond, a triple bond, O, S, NR₆, wherein R₆is H, alkyl, aralkyl, acyl or alkoxycarbonyl, and carbonyl, and/or

R₁is

a phenylalkyl wherein alkyl is a straight- or branched (C_6-20)carbon chain; or

a straight- or branched (C_6-20)carbon chain optionally substituted by halogen,

a straight- or branched (C_6-20)alkoxy chain optionally substituted by halogen,

a straight- or branched (C_6-20)alkenyloxy,

cycloalkylalkyl substituted by C_6-20alkyl,

heteroarylalkyl substituted by C_6-20alkyl,

heterocyclic C_6-20alkyl or

heterocyclic alkyl substituted by C_6-20alkyl,

and wherein

the alkyl moiety may have

each of R₂, R₃, R₄and R₅, independently, is H, C_1-4alkyl or acyl

or a pharmaceutically acceptable salt thereof.

12. A method according to claim 7, wherein the S1P receptor agonist is compound of formula I

wherein R₁is straight- or branched (C_12-22)carbon chain

R₁is

a phenylalkyl wherein alkyl is a straight- or branched (C_6-20)carbon chain; or

a straight- or branched (C_6-20)carbon chain optionally substituted by halogen,

a straight- or branched (C_6-20)alkoxy chain optionally substituted by halogen,

a straight- or branched (C_6-20)alkenyloxy,

cycloalkylalkyl substituted by C_6-20alkyl,

heteroarylalkyl substituted by C_6-20alkyl,

heterocyclic C_6-20alkyl or

heterocyclic alkyl substituted by C_6-20alkyl,

and wherein

the alkyl moiety may have

each of R₂, R₃, R₄and R₅, independently, is H, C_1-4alkyl or acyl

or a pharmaceutically acceptable salt thereof.

13. A combination according to claim 11, wherein the S1P receptor agonist is 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in free form or in a pharmaceutically acceptable salt form.

14. A method according to claim 12, wherein the S1P receptor agonist is 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in free form or in a pharmaceutically acceptable salt form.