PYRIDOPYRIMIDINE DERIVATIVES AND USE THEREOF IN THE TREATMENT OF ITCH AND ITCH RELATED DISORDERS

The present invention relates to uses of Vanilloid Receptor antagonists, e.g. the use of pyridine derivatives orf formula (I) in the treatment of itch and itch related disorders or diseases, and to pharmaceutical compositions for such uses.

International Patent Application Publication No. WO02/076946 describes certain pyridine derivatives and their medical uses.

In a first aspect the present invention provides the use of a compound of formula (I)

wherein

R ¹ and R ² together are -NH-C(SR ⁶ )=N-C(O)-, -NR ⁷ -C(R ⁸ )=N-C(O)-, -N=C(SR ⁹ )-NR ¹⁰ -C(O)-, - NR ¹¹ -X-NR ¹² C(O)-, -NH-X-NH-, -NH-X-N=C(R ¹³ )-, -NH-X-NH-CH ₂ -, -N=Z-NH-, -N=Z-NH- CH ₂ -, -N=Z-NH-C(O)- and -N=Z-N=C(R ¹⁴ )-- wherein X is C(O), C(S) or C(O)-C(O); Z is N or CR ¹⁵ , R ⁶ is C _r C ₄ alkyl; R ⁷ and R ⁸ are each independently hydrogen, CrC ₄ alkyl, C ₃ - C ₈ cycloalkyl or form together with the adjacent atoms a 5 or 6 membered heterocyclic ring; R ⁹ and R ¹⁰ together are C _r C ₄ alkylene; R ¹¹ is hydrogen; C _r C ₄ alkyl; C _r C ₄ alkyl substituted by C(O)OCi-C ₄ alkyl; or phenyl substituted by CrC ₄ alkyl; R ¹² is hydrogen, NH ₂ ; CrC ₄ alkyl; or phenyl substituted by C _r C ₄ alkyl; R ¹³ is hydrogen, halogen, NH ₂ or C ₁ -C ₄ BIkOXy; R ¹⁴ is hydrogen, hydroxy, halogen, NH ₂ , d-C ₄ alkyl or C _r C ₄ alkoxy; and R ¹⁵ is hydrogen, halogen, C _r C ₄ alkyl, C _r C ₄ alkoxy or SCH ₂ C(O)OC(CH ₃ ) ₃ ;

R ³ is hydrogen; OH; CN; d-Cealkyl; phenyl; or C(O)OC _r C ₄ alkyl;

R ⁴ is hydrogen; halogen; NH ₂ ; CN; C _r C ₆ alkyl; C _r C ₆ alkyl substituted by OH; phenyl; phenyl substituted by OH, halogen, d-C ₆ alkyl, C _r C ₆ haloalkyl or Ci-C ₆ alkoxy; benzyl; benzoyl substituted by OH; or C(O)OC ₁ -C ₆ alkyl; 5 or 6 membered aromatic or aliphatic heterocyclic ring;

R ⁵ is hydrogen; OH; NH ₂ ; halogen; d-C ₆ alkyl; d-C ₆ alkyl substituted by halobenzyl; C ₃ -C ₆ cycloalkyl; phenyl; pyridinyl; NHC _r C ₄ alkyl; or N=CHN(C _r C ₄ alkyl) ₂ ; in free base or acid addition salt form in the manufacture of a medicament for the treatment of itch or an itch related disorder or disease.

Compounds for use in the invention exist in free or salt, e.g. acid or base addition salt form. The invention is to be understood as including the use of compounds of formula (I) in free as well as in salt form, e.g. as trifluoroacetate or hydrochloride salt. Suitable pharmaceutically acceptable acid addition salts for pharmaceutical use in accordance with the invention include in particular the hydrochloride salt.

More particular examples for R ¹ and R ² include -NR ¹¹ C(O)NR ¹² C(O)-, -NHC(S)NHC(O)-, - NH-C(O)-NH-, -NH-C(S)-NH-, -NH-C(O)-C(O)-NH-, -NH-C(O)-N=C(CI)-, -NH-C(O)- N=C(OCH ₃ )-, -NH-C(O)-N=C(NH ₂ )-, -NH-C(O)-N=CH-, -NH-C(O)-NH-CH ₂ -, -NH-C(SCH ₃ )=N- C(O)-, -N=CH-NH-, -N=N-NH-, -N=CH-NH-CH ₂ -, -N=C[SCH ₂ C(O)OC(CH ₃ ) ₃ ]-NH-C(O)-, - N=CH-NH-C(O)-, -N=C(CI)-NH-C(O)-, -N=C(NH ₂ )-NH-C(0)-, -N=C(CH ₃ )-NH-C(0)-, - N=C(CI)-N=C(CI)-, -N=C(CI)-N=C(NH ₂ )-, -N=C(OCH ₃ )-N=C(OCH ₃ )-, -N=C(OCH ₃ )-N=C(NH ₂ )-

, -N=CH-N=C(NH ₂ )-, -N=CH-N=CH-, ■

A 5 or 6 membered aromatic or aliphatic heterocyclic ring for R ⁴ may be e.g. but not limited to thiophenyl, furyl, imidazolyl, pyridinyl, pyrimidinyl, pyrrolidinyl, piperidinyl, piperizinyl and derivatives thereof (e.g. C ₁ -C ₄ BlKyI, OCrOC ₄ alkyl, halogenyl, etc.).

Alkyl groups in the compounds of formula (I) may be branched or straight chain.

In a compound of formula (I) the following significances are preferred independently, collectively or in any combination or sub-combination:

(a) R ¹ and R ² together are a divalent group -NHC(O)NHC(O)- or -NHC(S)NHC(O)-;

(b) R ³ is hydrogen;

(c) R ⁴ is phenyl; phenyl substituted by OH, halogen, e.g. chloride, fluoride, Ci-C ₆ alkyl, C ₁ - C ₆ haloalkyl or d-Cealkoxy; and

(d) R ⁵ is branched or un-branched Ci-C ₆ alkyl, e.g. isopropyl, tert. butyl or C ₃ -C ₆ cycloalkyl.

Also preferred are compounds of formula (I) wherein R ¹ and R ² together are -NH-C(S)-NH- C(O)-; R ³ is hydrogen; R ⁴ is phenyl; or phenyl substituted by halogen, e.g. by chloro, C ₁ - C ₄ alkyl, C ₁ -C ₄ haloalkyl or C _r C ₄ alkoxy; and R ⁵ is C _r C ₄ alkyl; or C ₃ -C ₆ cycloalkyl, e.g. tert.- butyl.

Most preferred the compound of formula (I) is 7-tert.-Butyl-6-(4-chloro-phenyl)-2-thioxo-2,3- dihydro-1.H.-pyrido[2,3-d.]pyrimidin-4-one.

The compounds of formula (I) may be prepared by the processes generally and specifically described in WO02/076946.

According to the present invention itch (= pruritus) or an itch related disorder or disease includes pruritoceptive itch (originating in the skin, including itching arising from or associated with inflammatory skin diseases, e.g. skin diseases responsive to corticosteroid treatment and/or calcineurin inhibitor treatment, e.g. Elidel, Protopic), neuropathic itch (due to a primary neurological disorder) and neurogenic itch (arising from neurophysiological dysfunction).

Examples for such disorders or diseases include, but are not limited to

Pruritic dermatoses, e.g. atopic dermatitis, psoriasis, urticaria, irritant/allergic contact eczema, prurigo nodularis, insect bites, scabies, Lichen ruber, dry skin (xerosis), pruritis ani, pruritus scroti, pruritus vulvae,

Pruritus due to

- metabolic disorders, including e.g. chronic renal disease, primary billiary cirrhosis, cholestasis, hepatic insufficieny, psychotropic medication

- endocrine disorders, including e.g. thyrotoxicosis, hypothyroidism, hyperparathyroidism, hyperphosphatemia, diabetes mellitus,

- granulocytic and infectious diseases (e.g. chicken pox, fungal infections, post-herpes zoster)

- malignant diseases, including e.g. lymphoma, leukemia, polycythemia, rubra vers,

- autoimmune diseases, including e.g. dermatitis herpetiformis, linear IgA syndrome, multiple sclerosis.

In a preferred aspect the disorder or disease is selected from the group consisting of itch and pruritic dermatoses, especially preferred from the group consisting of itch, atopic dermatitis and psoriasis.

For the above indications the appropriate dosage of the agents of invention will, of course, vary depending upon, for example, the host, the mode of administration and the nature and severity

of the condition being treated as well as the relative potency of the particular agent of invention employed. For example, the amount of active agent required may be determined on the basis of known in vitro and in vivo techniques, determining how long a particular active agent concentration in the blood plasma remains at an acceptable level for a therapeutic effect. In general, satisfactory results in animals are indicated to be obtained at daily dosages of from about 0.01 to about 20.0 mg/kg p.o. In humans, an indicated daily dosage is in the range of from about 0.7 to about 1400 mg/day p.o., e.g. from about 50 to 200 mg, conveniently administered once or in divided doses up to 4 x per day or in sustained release form. Oral dosage forms accordingly suitably comprise from about 0.2 or 2.0 to about 700 or 1400 mg agent of invention admixed with an appropriate pharmaceutically acceptable diluent or carrier therefore.

Preferably the compositions comprising a compound of formula (I) are provided in a form useful for the topical or local application such as e.g. in the form of a cream, an ointment, a gel, a solution, a semi-solid formulation or a solid or semi-liquid dispersion form.

In a preferred aspect a compound of formula (I) is used for the topical treatment or itch and inflammatory dermatoses associated with itch, e.g. atopic dermatitis.

Examples for compositions comprising the agents of invention include, e.g. a solid dispersion, an aqueous solution, e.g. containing a solubilising agent, e.g. cyclodextrin, a microemulsion and a suspension of, e.g. a micronized hydrochloride salt of a compound of formula (I) in, e.g. aqueous methyl cellulose in the range of from 0.1 to 1 %, e.g. 0.5 %. The composition may be buffered to, e.g. a pH in the range of from 3.5 to 9.5, e.g. to pH 4.5, by a suitable buffer, e.g. malic acid.

In a preferred aspect, the invention provides a method for the topical treatment of itch or an itch related disorder or disease, e.g. comprising administration to a patient an effective amount of a compound of formula (I) in free base or acid addition salt form, as described above.

In accordance with the foregoing the present invention also provides:

(1 ) A compound of formula (I) for use of treating itch or an itch related disorder or disease, e.g. such as described above.

(2) Use of a pharmaceutical composition comprising a compound of formula (I) in free base or pharmaceutically acceptable acid addition salt form as active ingredient together with a pharmaceutically acceptable diluent or carrier therefore, in the treatment of itch or an itch related disorder or disease.

Treatment as used herein includes therapeutic treatment and prevention.

(3) A combination comprising a therapeutically effective amount of a compound of formula (I) in free base or pharmaceutically acceptable acid addition salt form and a second drug substance, said second drug substance being for example for use in the treatment of itch or an itch related disorder or disease, for the use in the treatment of itch or an itch related disorder or disease.

The second drug may be selected from ingredients which are known as being itch-reducers, such as e.g. campher, menthol, phenol, pramoxine, diphenylhydramine, caine anesthetics, e.g. benzocaine, cortisone, hydrocortisone or corticosteroids, or it may be an antiinflammatory agent such as e.g. Elidel ^® , Protopic ^® , diclofenac, ibuprofen, indomethacin, nabumetone, ketoprofen, naproxen, piroxicam, sulindac, etodolac, meloxicam, rofecoxib, celecoxib, etoricoxib, parecoxib, valdecoxib and tilicoxib.

The preferred compound of formula (I) is the 7-tert.-butyl-6-(4-chlorophenyl)-2-thioxo-2,3- dihydro-1.H-pyrido[2,3-.d.]-pyrimidin-4-one (example 2 of WO02/076946).

The following compounds, disclosed specifically in WO02/076946, are of use in the present invention:

6-benzyl-7-isopropyl-1.H.-pyrido[2,3-.d.]pyrimidine-2,4-d ione;

7-tert.-butyl-6-(4-chlorophenyl)-2-thioxo-2,3-dihydro-1.H .-pyrido[2,3-.d.]-pyrimidin-4-one;

Compounds of formula (I) wherein R ¹ and R ² together are -NR ¹¹ -C(O)-NR ¹² -C(O)- and R ³ is hydrogen as follows:

Compounds of formula (I) wherein R ¹ and R ² together are -NH-C(S)-NH-C(O)- and R ³ is hydrogen as follows:

Compounds of formula (I) as follows:

Description of the Figures:

Figure 1: The TEST COMPOUND inhibits concentration-dependently capsaicin-induced skin inflammation and scratching: % inhibition vs. vehicle-treated animals, shown are the mean values of groups (see also note to Table 1).

In the EXAMPLES the following abbreviations are used: ACD allergic contact dermatitis

DNFB dinitrofluorobenzene

PD model pharmacodynamic model

EXAMPLES:

Example 1 : Capsaicin-induced irritant contact dermatitis

Capsaicin is applied at 0.1% in volumes of 15 μl to both sides of the right auricles of rats. Test animals are simultaneously treated with capsaicin and the TEST COMPOUND (= compound of example 2 of WO02/076946), both prepared in the same vehicle (mixture of ethanol/acetone/dimethylacetamide). Control animals are treated with capsaicin alone. The animals are observed clinically for ear reddening, scratching, and ear swelling for 40 minutes after challenge. Ear reddening is scored with 0 (not present), 1 (mild), 2 (pronounced) and 3 (severe). Scratching is recorded by counting scratching bouts with right or left hind limb for 40 minutes after the challenge. Ear swelling is determined by differences in left and right ear thickness before challenge and 40 minutes after the challenge. In the first series of studies the minimal effective concentration is evaluated (Table 1 ).

Few minutes after the challenge with 0.1 % capsaicin reddening and swelling of the treated auricles and scratching bouts are observed in almost all animals. The clinical signs persist for 30 to 40 minutes. Simultaneous application of the TEST COMPOUND inhibits the symptoms concentration-dependently. Scratching bouts are reduced by 79 -76% with 0.5 and 1.0% of the TEST COMPOUND (see Figure 1). Reddening and swelling are similarly inhibited. No inhibition of scratching is observed with 0.25% of the TEST COMPOUND. The reference compound hydrocortisone inhibits scratching by 85% at the clinically used concentration of 1.0%.

As shown in TABLE 1 below, the topical use of the TEST COMPOUND inhibits redness, scratching and swelling in capsaicin-induced skin irritation in rats in a concentration dependent way.

TABLE 1 :

Treatment Test animals Control animals

Redness Scratching Swelling Redness Scratching Swelling

TEST 1.3 ± 0.5 16 ± 11 0.04 ± 3.0 ± 0.0 68 ± 25 0.23 ± 0.09

_***

COMPOUND [1 ± 1] 0.05 [2 ± 1]

1.0%

TEST 1.5 ± 0.6 ^*" 12 ± 9.3 ^** 0.07 ± 2.8 ± 0.4 57 ± 29 0.23 ± 0.08

COMPOUND [0] 0.04 ^*** [1 ± 1]

0.5%

TEST 2.7 ± 0.5 ^ns 46 ± 25 ^ns 0.19 ± 2.8 ± 0.4 53 ± 21 0.13 ± 0.04

COMPOUND [1 ± 1] 0.07 [1 ± 1]

0. 25%

Hydrocortisone 1.2 ± 0.4 ^*" 9 ± 7 0.11 ± 2.8 ± 0.4 62 ± 31 0.29 ± 0.09

1.0%

[1 ± 1] 0.09* [ 1± 1]

Note: In test animals the TEST COMPOUND is simultaneously applied with 0.1% capsaicin. Up to 40 minutes after the challenge, reddening, scratching (counting bouts) and swelling are examined in TEST COMPOUND-treated and vehicle-treated animals. Hydrocortisone is used as a reference compound. Figures in [ ] are number of scratch bouts with the left hind leg (not related to capsaicin); groups of 6 animals are used; ^* : p <0.05, ^*** : p< 0.001 vs controls (ANOVA/Holm Sidak)

Example 2: DNFB-induced allergic contact dermatitis in pigs

Further activity of the TEST COMPOUND is tested in a swine model. The latter PD model is used to evaluate skin permeability of the TEST COMPOUND in vivo under skin conditions which are similar to the human situation. Challenge reactions in young, DNFB-sensitized domestic pigs are elicited on contralateral test sites of the dorsolateral back. The formulations (verum or placebo) are applied contralateral^ to 2 test sites in each animal 0.5 and 6 hours after the challenge. The test sites are clinically examined 24 hours after the challenge when inflammation peakes. The changes are scored on a scale from 0 to 4 for extent and intensity of redness and infiltration allowing a combined maximal score of 12 per designated site. The TEST COMPOUND is compared with hydrocortisone and betamethasone (Table 2). The latter reference compounds are applied as drug substances and prepared in ethanol / propylene glycol at the clinically used concentrations. Marketed formulations are not used because the corresponding placebos are not available to us.

Table 2: Clinical efficacy of the TEST COMPOUND against acute ACD in domestic pigs

Clinical scores

Treatment Verum-treated sites Placebo-treated % Inhibition vs sites placebo

TEST COMPOUND 3.5 ± 0.9 (16) 5.7 ± 1.1 (16) 36 ± 19 ^""

3O mM

TEST COMPOUND 3.6 ± 1 .4 (14) 6.2 ± 1.8 (14) 41 ± 13 ^"*

1O mM (0.35%)

TEST COMPOUND 3 mM 3.8 ± 1 •6 (12) 6.1 ± 2.0 (12) 38 ± 14 ^"*

TEST COMPOUND 1 mM 4.9 ± 1 .0 (14) 5.9 ± 1.1(14) 17 ± 15 ^*

Hydrocortisone 1.0% 4.3 ± 1 .5 (14) 5.5 ± 1.3 (14) 24 ± 15 ^***

Betamethasone 0.1% 3.6 ± 1 .0 (8) 6.0 ± 1.0 88) 40 ± 11 ^"*

Note: First, on day 1 , domestic pigs weighing 12-15kg, are sensitized by epicutaneous administration of 500 μl of 10% DNFB, distributed evenly to both auricles and groins. Then, on day 10, challenge is performed by administration of 15 μl of a 1% DNFB solution to each of test sites (2cm diameter), arranged in 4 craniocaudal lines on both sides of the back of each animal. For compound evaluation the test site is treated 0.5 hours and 6 hours after DNFB challenge with experimental formulations containing the TEST COMPOUND at 10 to 1 mM. The contralateral left sites are treated similarly with the vehicle. Test sites are clinically examined 24 hours after the DNFB challenge, at the peak of the inflammatory response. Changes (reddening and infiltration) are scored on a scale from 0 to 4, allowing a combined maximal score of 10 per designated site. The clinical score in untreated test sites are 7.9 ± 1.4 (indicating some anti-inflammatory effect of the placebo (vehicle)). Mean values ± SD, +: figures in ( ) are numbers of test sites; ^*** : p > 0.001 , ns: not statistically significant vs placebo (ANOVA/Dunnet -test)

Clinical signs of ACD in test sites treated with the experimental clinical service form of the TEST COMPOUND are inhibited by 36 - 41% with > 3 mM formulations. The activity plateaues in the tested concentration range from 3 to 30 mM. This PD finding indicates bioavailability of the TEST COMPOUND in the skin after epicutaneous application of the clinical service form. In comparison with topical corticosteroids, the TEST COMPOUND inhibits skin inflammation as potently as betamethasone at 0.1% and is superior to 1.0% hydrocortisone at 10 mM (p<0.01) and 3 mM (p<0.05). It has alos been found that the TEST COMPOUND is as effective as Elidel 1% cream in this model.

Summary and conclusions of the topical administration studies in dermatitis models

Topical application of capsaicin to ears of rats induces scratching, skin reddening and swelling. These symptoms are concentration-dependently inhibited, indicating that topical application of the TEST COMPOUND interferes with capsaicin-induced VR1/TPVR1 activation in the skin (see Figure 1 ).

Example 3: Skin penetration in vitro

Penetration of the TEST COMPOUND into the skin and permeation through the skin is tested in vitro in static Franz-type diffusion cells at 32° for 48 hours. Thawed samples of human dorsal cadaver skin cut to 700 μm thickness are used. The TEST COMPOUND is applied epicutaneously as solution in propylene glycol. Samples of 100 μl are taken from the receptor reservoir 6 times for analysis and replaced by fresh receptor fluid (phosphate buffered saline/ fetal calf serum 2:1). Drug analysis is performed with receptor samples and specimens of the exposed skin (at the end of the experiment), from which the stratum corneum had been removed by 20 strippings with an adhesive tape. The weighed skin samples are homogenized in 0.2 M ammonium phosphate buffer (pH 7.0). The homogenates are extracted with ethyl acetate and processed for HPLC analysis. Concentrations in the receptor fluid and in the skin extracts are calculated using appropriate calibration curves. The data are shown in Table 3.

Table 3: Penetration / permeation of the TEST COMPOUND using human skin in vitro

Test article Skin concentration Skin permeation rate μg /g ng/ml/hr ng/cm^/hr

TEST COMPOUND, 1 % in propylene glycol 45 ± 14 49 ± 15 112 ± 34

Note: Mean ± standard deviation of triplicate determinations are given

The TEST COMPOUND exhibits a favorable skin penetration profile. For comparison, 1% hydrocortisone in propylene glycol results in skin concentrations of 47 ± 6 μg/g and permeation rates of 23 + 1 ng/cm ² /hour [Schmook, et al 2001]. The amount of the TEST COMPOUND penetrating into skin layers below the stratum corneum is much higher than the in vitro active concentrations which are in the 2 digit nanomolar concentrations.