NEW AGENTS FOR TREATING NEUROGENIC INFLAMMATION AND NEUROPATHIC HYPERALGESIA RELATED DISORDERS

Abstract

The present invention relates to 4-phenetylamino-7H-pyrrolo[2,3-d]pyrimidine derivatives of the and solvates, hydrates and pharmaceutically acceptable salts thereof, processes for manufacturing of them, the use of them, as well as pharmaceutical N compositions containing at least one of them as pharmaceutically active agent(s) together with pharmaceutically acceptable carrier, excipient and/or diluents, especially for the prevention and/or treatment of acute neurogenic inflammation and/or neuropathic hyperalgesia. Said 4-phenetylamino-7H-pyrrolo[2,3-d]pyrimidine compounds have been identified as new drug candidates for the prevention and/or treatment of acute neurogenic inflammation and/or neuropathic hyperalgesia.

Claims

1. Compounds of general formula (I) and their solvates, hydrates and pharmaceutically acceptable salts: ##STR00064## wherein R1 is substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, RaRbN—(C1-4 alkyl), where Ra and Rb are independently from each other C1-4 alkyl; R2, R3 are independently from each other hydrogen or C1-4 alkyl; R4 is aryl optionally substituted with 1 to 3 substituent(s) selected independently from each other from the group of halogen, hydroxyl, alkoxy, —NH.sub.2, —NRcRd, where Rc and Rd are independently from each other C1-4 alkyl, isoindole-1,3-dione-2-yl, —NHCOR7, —NHSO.sub.2R7 and —NHCONHR7; R5 is hydrogen or hydroxyl; R6 is hydrogen or C1-4 alkyl; R7 is C1-4 alkyl, C1-4 alkyl-CO—C1-4 alkoxy, —NReRf, where Re and Rf are independently from each other C1-4 alkyl, or aryl optionally substituted with 1 to 3 substituent(s) selected independently from each other from the group of halogen, C1-4 alkyl, C1-4 alkoxy and trifluoromethyl; with the proviso that R1 is other than unsubstituted pyridinyl, unsubstituted furanyl or dimethoxyphenyl when R4 is dimethoxyphenyl, R2 is methyl, R3 is hydrogen or methyl, and R5 and R6 are hydrogen.

2. Compounds according to claim 1, wherein R1 is substituted or unsubstituted phenyl, furanyl, pyridinyl, thienyl, pyrimidinyl or piperazinyl, RaRbN—(C1-3 alkyl), where Ra and Rb are independently from each other C1-3 alkyl; R2, R3 are independently from each other hydrogen or C1-3 alkyl; R4 is phenyl optionally substituted with 1 to 3 substituent(s) selected independently from each other from the group of halogen, hydroxyl, alkoxy, —NH.sub.2, —NRcRd, where Rc and Rd are independently from each other C1-3 alkyl, isoindole-1,3-dione-2-yl, —NHCOR7, —NHSO.sub.2R7 and —NHCONHR7; R5 is hydrogen or hydroxyl; R6 is hydrogen or C1-3 alkyl; R7 is C1-3 alkyl, C1-3 alkyl-CO—C1-3 alkoxy, —NReRf, where Re and Rf are independently from each other C1-3 alkyl, or phenyl optionally substituted with 1 to 3 substituent(s) selected independently from each other from the group of halogen, C1-3 alkyl, C1-3 alkoxy and trifluoromethyl.

3. Compounds according to claim 1, wherein R1 is substituted or unsubstituted phenyl, furanyl, pyridinyl, thienyl, pyrimidinyl or piperazinyl, RaRbN—(C1-2 alkyl), where Ra and Rb are independently from each other C1-2 alkyl; R2, R3 are independently from each other hydrogen or C1-2 alkyl; R4 is phenyl optionally substituted with 1 to 2 substituent(s) selected independently from each other from the group of halogen, hydroxyl, alkoxy, —NH2, —NRcRd, where Rc and Rd are independently from each other C1-2 alkyl, isoindole-1,3-dione-2-yl, —NHCOR7, —NHSO.sub.2R7 and —NHCONHR7; R5 is hydrogen or hydroxyl; R6 is hydrogen or C1-2 alkyl; R7 is C1-2 alkyl, C1-2 alkyl-CO—C1-2 alkoxy, —NReRf, where Re and Rf are independently from each other C1-2 alkyl, or phenyl optionally substituted with 1 to 2 substituent(s) selected independently from each other from the group of halogen, C1-2 alkyl, C1-2 alkoxy and trifluoromethyl.

4. Compounds according to claim 1, wherein R1 is substituted or unsubstituted phenyl, furanyl or pyridinyl, or Me.sub.2N-ethyl; R2, R3 are independently from each other hydrogen or methyl; R4 is phenyl optionally substituted with 1 to 2 substituent(s) selected independently from each other from the group of halogen, hydroxyl, methoxy, —NH.sub.2, —NMe.sub.2, isoindole-1,3-dione-2-yl, —NHCOR7, —NHSO.sub.2R7 and —NHCONHR7; R5 is hydrogen or hydroxyl; R6 is hydrogen or methyl; R7 is methyl, ethyl-CO-methoxy, —NEt.sub.2, or phenyl optionally substituted with 1 to 2 substituent(s) selected independently from each other from the group of halogen, methyl, methoxy and trifluoromethyl.

5. Compounds according to claim 1, wherein R1 is unsubstituted phenyl or furan-2-yl, 3-chloro-fenyl, 5-bromo-pyridine-3-yl or Me.sub.2N-ethyl; R2, R3 are independently from each other hydrogen or methyl; R4 is phenyl optionally substituted with 1 to 2 substituent(s) selected independently from each other from the group of halogen, hydroxyl, methoxy, —NH.sub.2, —NMe.sub.2, isoindole-1,3-dione-2-yl, —NHCOR7, —NHSO.sub.2R7 and —NHCONHR7; R5 is hydrogen or hydroxyl; R6 is hydrogen or methyl; R7 is methyl, ethyl-CO-methoxy, —NEt.sub.2, or phenyl optionally substituted with 1 to 2 substituent(s) selected independently from each other from the group of halogen, methyl, methoxy and trifluoromethyl.

6. Compounds according to claim 1, wherein R1 to R3, R5 and R6 are as defined above and R4 is phenyl, hidroxy-phenyl, amino-phenyl, dimethylamino-phenyl, methoxy-phenyl, dimethoxy-phenyl, chloro-phenyl, fluoro-phenyl, phenyl-isoindole-1,3 -dione, phenyl-acetamide, phenyl-3-(2,4-difluoro-phenyl)-urea, phenyl-benzamide, phenyl-3-trifluoromethyl-benzamide, phenyl-4-chloro-benzamide, phenyl-1,1-diethyl-urea, phenyl-methanesulfonamide, phenyl-2,4-difluoro-benzenesulfonamide, phenyl-succinamic acid methyl ester or phenyl-3-(3-trifluoromethyl-phenyl)-urea.

7. Compounds according to claim 1, selected from the group consisting of (7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)-[2-(4-methoxy-phenyl)-ethyl]-amine; [7-(3-Dimethylamino-propyl)-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl]-[2-(4-methoxy-phenyl)-ethyl]-amine; N-{4-[2-(7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-ylamino)-ethyl]-phenyl}-acetamide; N-(4-{2-[7(3 -Dimethylamino-propyl)-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-ylamino]-ethyl}-phenyl)-acetamide; (7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)-[2-(3-methoxy-phenyl)-ethyl]-amine; 3-[2-(7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-ylamino)-ethyl]-phenol; 4-[2-(7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-ylamino)-ethyl]-phenol; (7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)-[2-(3-chloro-phenyl)-ethyl]-amine; (7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)-[2-(3-fluoro-phenyl)-ethyl]-amine; [2-(4-Amino-phenyl)-ethyl]-(7-benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amine; (7-Benzyl-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)-[2-(4-dimethylamino-phenyl)-ethyl]-amine; and [2-(4-Amino-phenyl)-ethyl]-[7-(3-dimethylamino-propyl)-5,6-dimethyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl]-amine.

8. Pharmaceutical composition comprising one or more compound(s) of general formula (I) according to claim 1 or their solvates, hydrates, pharmaceutically acceptable salts or mixtures thereof as active ingredient together with one or more pharmaceutical auxiliary material(s).

9. Compounds according to claim 1 for use in the treatment and/or prevention of acute neurogenic inflammation and/or neuropathic hyperalgesia.

10. Compounds or the pharmaceutical composition for use according to claim 9, wherein the neurogenic inflammation comprises rheumatoid arthritis, allergic contact dermatitis, psoriasis, asthma and inflammatory bowel diseases.

11. A method for treating neurogenic inflammation and/or neuropathic hyperalgesia, which method comprises administering to a mammal an amount of a compound according to claim 1, or a composition thereof, effective to treat said neurogenic inflammation and/or neuropathic hyperalgesia.

12. The method of claim 11 wherein the mammal suffers from rheumatoid arthritis, allergic contact dermatitis, psoriasis, asthma or inflammatory bowel diseases.

Description

BRIEF DESCRIPTION OF DRAWINGS:

[0153] FIG. 1 shows the schematic drawing of the isolated trachea perfusion system.

[0154] FIG. 2 depicts the schematic drawing describing the experimental protocol for the examination of acute neurogenic plasma protein leakage in the paw skin of the rat.

[0155] FIG. 3 depicts the schematic drawing describing the experimental protocol for the examination of plantar incision-induced hyperalgesia/allodynia.

[0156] FIGS. 4A and B depict the effect of BST compounds on electrically-evoked release of CGRP from isolated rat tracheae. Each column represents the mean+s.e.m. concentration of CGRP (A) measured in the incubation medium of the prestimulated, stimulated and poststimulated 8-min fractions and the (B) absolute peptide release values calculated by substracting the basal release measured in the first, prestimulated fraction from both the stimulated and poststimulated fractions and adding these data. In each group for compound testing n=5 experiments (5×2 tracheae), and in the control group n=15 experiments (15×2 tracheae). *P<0.05, **P<0.01 (vs. respective values of the control experiment; Student's t-test for unpaired comparison).

[0157] FIG. 5 illustrates the effect of BST compounds on 1% mustard oil-induced plasma protein extravasation in the acutely denervated hindpaw skin of the rat. In the control group the vehicle (MC) was applied p.o. in the same volume. Each column shows the mean±s.e.m. of n=8 rats; **<0.01, ***<0.001 vs. vehicle-treated control group (Student's t-test for unpaired comparison).

[0158] On FIG. 6 the effect of BST compounds is shown on plantar incision-evoked mechanical allodynia of the rat hindpaw. Allodynia is expressed as % change of the touch sensitivity threshold compared to the pre-operative values. Colums show the means+s.e.m. of n=8 rats in the BST compound-treated groups, and n=31 in the methylcellulose solvent-treated group; *p<0.05, vs. respective pre-dose values (Student's t-test for paired comparison).

[0159] FIG. 7 shows the effect of BST compounds on plantar incision-evoked thermal allodynia of the rat hindpaw. Heat allodynia is expressed as ° C. decrease of the thermonociceptive threshold compared to the pre-operative values. Colums show the means+s.e.m. of n=8 rats in the BST compound-treated groups, and n=31 in the methylcellulose solvent-treated group; *p<0.05, vs. respective pre-dose values (Student's t-test for paired comparison).

[0160] FIG. 8 shows the effect of BST compounds on sciatic nerve ligation-induced neuropathic mechanical allodynia. Allodynia is expressed as % change of the touch sensitivity threshold compared to the pre-operative values. Colums show the means+s.e.m. of n=8 rats in the BST compound-treated groups, and n=23 in the methylcellulose solvent-treated group. Neither of examined test compounds exerted significant inhibitory effect on the nerve ligation-induced mechanical allodynia (Student's t-test for paired comparison).

[0161] FIG. 9 displays the effect of BST compounds on plantar incision-evoked mechanical hyperalgesia of the rat hindpaw. Hyperalgesia is expressed as % change of the mechanonociceptive threshold compared to the pre-operative values. Colums show the means+s.e.m. of n=8 rats in the BST compound-treated groups, and n=23 in the methylcellulose solvent-treated group; **p<0.01, vs. respective pre-dose values (Student's t-test for paired comparison).

BIOLOGICAL EXAMPLE 1

[0162] Somatostatin sst.sub.4 Receptor-Coupled G-Protein Activation Assay

[0163] Experimental Model

[0164] [.sup.35S]GTPγS binding assay is a functional test determining agonist-induced and receptor-mediated G-protein activation which is based on the increase in guanine nucleotide exchange at G-proteins upon agonist stimulation. The interaction of a G protein-coupled receptor (GPCR) with the G protein is the first step in the transduction of the receptor binding signal to the activation of the second-messenger systems. We measured the level of [.sup.35S]-GTPγS bound to the α subunit of G proteins and determined the efficacy of the compounds. Compounds which elicited 200% [.sup.35S]GTPγS binding in nanomolar concentration were considered effective agonist. The examined compounds were added into the medium in 1 nM, 10 nM, 100 nM 1 μM and 10 μM concentrations.

[0165] Protocol and Investigational Technique

[0166] Membrane fractions were prepared from CHO cells stably expressing the sst.sub.4 receptor in Tris-EGTA buffer (50 mM Tris-HCl, 1 mM EGTA, 3 mM MgCl.sub.2, 100 mM NaCl, pH 7.4). These membrane fractions (˜10 μg of protein/sample) were incubated at 30° C. for 60 min in the same Tris-EGTA buffer containing [.sup.35S]GTPγS (0.05 nM) and increasing concentrations (10.sup.−9 to 10.sup.−5. M) of test compounds in the presence of 30 μM GDP in a final volume of 500 μl. Non-specific binding was determined in the presence of 10 μM unlabelled GTPγS. Total binding was measured in the absence of test compounds. To calculate the specific binding, non-specific binding was subtracted from total binding. The reaction was terminated by filtrating the samples through Whatman GF/B glass fiber filters. Using 48-well Slot Blot Manifold from Cleaver Scientific filters were washed three times with ice-cold 50 mM Tris-HCl buffer (pH 7.4). After drying for 60 min at 37° C., radioactivity was measured in scintillation liquid in a Packard Tri-Carb 2800 TR scintillation counter. Test compound-induced G-protein stimulation was given as percentage over the specific [.sup.35S]GTPγS binding observed in the absence of agonists.

[0167] Results:

[0168] Compounds which evoke 200% [.sup.35S]GTPγS binding in nanomolar concentration are considered effective agonist. We found 5 effective compounds among the examined 13 molecules in the G-protein activation experiments. Using 100 nM concentration activation reached 245.67%, 207.67%, 210.67%, 202.67% and 194.5% in cases of BST-1411(example 2), BST-1412(example 41), BST-1413(example 3), BST-1642(example 40), and BST-1658 (example 58), respectively, therefore, these compounds can be considered as effective sst.sub.4 receptor agonists.

BIOLOGICAL EXAMPLE 2

[0169] Electrical Field Stimulation-Induced Release of Calcitonin Gene-Related Peptide (CGRP) from Sensory Nerve Terminals of Isolated Rat Tracheae

[0170] Experimental Model

[0171] Rats were exsanguinated in deep anaesthesia (sodium thiopental, 50 mg/kg i.p.), then the whole trachea was removed and cleaned of fat and adhering connective tissues. Tracheae from two rats were placed into the same 1.8 ml organ bath to obtain sufficient amount of released peptide and perfused (1 ml/min) with pH- (7.2) controlled oxygenized Krebs solution for 60 minutes (equilibration period) at 37° C. temperature. After discontinuation of the flow, the solution was changed three times for 8 minutes to produce pre-stimulated, stimulated, post-stimulated fractions. Electrical field stimulation (40 V, 0.1 ms, 10 Hz for 120 s; 1200 pulses) was performed to elicit neurotransmitter release at the beginning of the second 8-minute period. Stimulation with 0.1 ms pulse width selectively activates very fast Na.sup.+ channels which are only present in the membrane of neural structures (Birmingham and Wilson, 1963; Coburn and Tomita 1973; Szolcsányi and Barthó, 1982), therefore it excites nerve endings without influencing other excitable cells in the tracheae such as smooth muscle cells. Therefore, this in vitro system is approprite to study the mechanism of sensory neuropeptide release and examine the effect of compounds acting directly at the sensory nerve terminals

[0172] Protocol

[0173] Tracheae excised from 80 male and 80 female Wistar rats (250-380 g) were used altogether in this series of studies, 50-50% females and males were used in all experimental groups. There were 14 groups: 13 for the examined compounds containing 5 experiments performed paralelly in 5 perfusion systems to provide n=5 data per group (10 tracheae per group) and a control group composed of 3 separate experiments done at the beginning, the middle and the end of the total period (n=15, 30 tracheae). The whole data set was obtained in blocks, the total study was perfomed on 8 experimental days during 4 weeks (2 days per week, Tuesdays and Wednesdays; two groups every occassion). Krebs solution was used in the prestimulated fraction for determining the basal CGRP outflow. During the stimulated and poststimulated fractions the incubation medium contained the examined compound in 500 nM concentration.

[0174] Investigational Technique: Measurement of CGRP Concentration by Radioimmunoassay

[0175] CGRP concentration was determined from 400-400 μl samples of the organ bath solutions by means of a selective and sensitive radioimmunoassay method developed in our laboratories and described in details in several previous papers (Nemeth et al. 1998, 1999, 2006; Helyes et al., 1997, 2001, 2006; Borzsei et al., 2008). The released amount of the peptides was calculated as fmol peptide per mg wet tissue (trachea). The absolute EFS-induced CGRP outflow in each experiment was calculated by taking off the basal release measured in the first (pre-stimulated) fraction from the second and third 8-min fractions and then adding these values. The detection limits of the RIA assay was 0.2 fmol/tube.

[0176] Results:

[0177] In the control experiments the release of CGRP increased from 0.19±0.03 fmol/mg to 0.67±0.09 fmol/mg wet tissue and 0.34±0.04 fmol/mg wet tissue, in the second and third 8-min fractions, respectively, as a result of the electrical field stimulation. The absolute release in response to this stimulation after taking off the basal release from the second and third fractions was 0.76±0.17 fmol/mg. Addition of 500 nM of 5 of the 13 examined BST compounds—BST-1411(example 2), BST-1412(example 41), BST-1415(example 51), BST-1642(example 40) and BST-1701 (example 12)- to the stimulated and post-stimulated fractions significantly inhibited the stimulation-evoked CGRP release by about 60-80%. The greatest effects of 79.55% and 72.5% inhibitions on the absolute release were obtained with BST-1415 and BST-1411, respectively (see FIGS. 4A and B).

BIOLOGICAL EXAMPLE 3

[0178] Mustard Oil-Induced Acute Neurogenic Inflammation in the Paw Skin of the Rat

[0179] Experimental Model

[0180] Deep anaesthesia was performed with sodium-thiopental (50 mg/kg i.p.). Both hindlegs of the rats were acutely denervated (the sciatic and the saphenous nerves were cut 30 min before the induction of inflammation) to avoid the influence of reflex mechanisms. Inflammation in the dorsal skin of the hindpaws was evoked by topical application of 1% mustard oil dissolved in paraffin oil. This compound selectively activates capsaicin-sensitive peptidergic fibres through the TRPA1 ion channel, therefore induces acute inflammatory reaction with exclusively neurogenic mechanisms via the release of pro-inflammatory sensory neuropeptides, such as substance P and CGRP. Extravasation of plasma albumin was measured by the Evans blue leakage method (see FIG. 2). Evans blue (50 mg/kg) which binds to plasma albumine, was injected i.v. and neurogenic inflammation was induced 5 min later. Rats were executed by exsanguination 20 min after mustard oil application. The extravasated dye in the paw skin was extracted with formamide for 72 h at room temperature for spectrophotometric determination at 620 nm. The amount of the accumulated Evans blue, which quantitatively correlates with the intensity of plasma extravasation, was expressed as μg dye/g wet skin (Helyes et at, 1997, 2001, 2006; Borzsei et al., 2008).

[0181] Protocol

[0182] One hundred and thirty four (134) Wistar rats of both sexes (70 males and 64 females; 220-350 g) kept in the Animal House of the University of Pecs in a temperature-controlled room and provided with a 12-hour light-dark cycle, standard rat chow and water ad libitum were studied in this experimental series. They were divided into 14 experimental groups: 13 for the examined compounds and one vehicle-treated control group, all of them were composed of both males and females equally. The study was undertaken in blocks with 10-14 rats per occasion, the whole data set was obtained during 14 days. The examined compound suspended in methylcellulose (100 μg/kg; 0.2 ml/100 g from the 50 μg/ml solutions) was administered p.o. 60 min before the induction of the inflammation by mustard oil smearing. Rats in the control group were treated with the same volume of the methylcellulose vehicle, there were 3-4 controls every experimental day.

[0183] Investigational Technique: Measurement of Evans Blue Accumulation in the Paw Skin

[0184] Extravasation of plasma albumin in the dorsal skin of the hindpaws was measured by the Evans blue leakage method. Evans blue (50 mg/kg) which binds to plasma albumine was injected i.v. and acute neurogenic inflammation was induced 5 min later with 1% mustard oil smearing. Rats were exsanguinated 20 min after mustard oil application in deep anaesthesia. The skin of the hindpaws was removed, their weight was measured and the extravasated dye was extracted with formamide at room temperature during 72 h for photometric determination at 620 nm. The amount of the accumulated Evans blue, which quantitatively correlates with the intensity of plasma extravasation, was expressed as μg dye/g wet tissue (Szolcsanyi and Bartho 1981; Helyes et al., 1997, 2001, 2006).

[0185] Results:

[0186] In control, vehicle-treated rats, topical application of 1% mustard oil induced 136.7±10.9 μg/g wet tissue Evans blue accumulation in the dorsal skin of the hindpaw within 20 min. Oral pretreatment with 100 μg/kg BST-1413(example 3), BST-1642(example 40), BST-1684(example 39), BST-1686(example 43), BST-1693(example 1), BST-1694(example 62), BST-1701(example 12), significantly inhibited this acute neurogenic inflammatory response by about 40-70%, the greatest inhibitory effects of 70.4% was observed with BST-1693 (example 1)(FIG. 5).

BIOLOGICAL EXAMPLE 4

[0187] Plantar Incision-Induced Mechanical Allodynia and Thermal Hyperalgesia (Postoperative Pain Model)

[0188] Experimental Model

[0189] Rats were anaesthesized with sodium-pentobarbital (Euthasol, 40 mg/kg i.p.) and a 1 cm longitudinal incision was made through the skin, fascia and muscle of the plantar aspect of the hindpaw. Significant decrease of both the thermonociceptive and mechanonociceptive thresholds (heat and mechanical allodynia) of the paw develops 1 day after this procedure. This technique has been shown to be a reliable model to understand mechanisms of peripheral and central sensitization caused by surgery and to investigate new therapies for postoperative pain in humans (Brennan et al. 1996; Furedi et al. 2009).

[0190] Protocol

[0191] One hundred and forty five (145) female Wistar rats (150-250 g) kept in the Animal House of the University of Pecs in a temperature-controlled room provided with a 12-hour light-dark cycle, standard rat chow and water ad libitum were used in this experimental series. They were brought to the air-conditioned laboratory the day before the experiment started. Throughout the total study the same assistant handled all the animals. They were habituated to the measurement's conditions prior to the study by performing two conditioning threshold measurements, the results of which were not included in the final analysis. The observer was blind to the drug treatment of the animals. Touch sensitivity was measured with a dynamic plantar aesthesiometer (DPA) and the thermonociceptive threshold was determined with an increasing temperature water-bath (ITWB) on the same rats (see below). After conditioning, 3 control mechanonociceptive and one control thermonociceptive threshold measurements were done on 3 consecutive days prior to the incision. Rats were then anaesthesized with sodium-pentobarbital and a 1 cm longitudinal incision was made through the skin, fascia and muscle of the plantar aspect of the left hindpaw. One day after this procedure, pre-dose control measurements with both the DPA and the ITWB were performed. Test compounds were administered p.o. and post-dose touch sensitivity and thermonociceptive thresholds were measured 60 min later. The means of the 3-3 mechanonociceptive and 2-2 thermonociceptive measurements performed consecutively on both the injured (ipsilateral) and non-injured (contralateral) paws were used for analysis.

[0192] The examined compound suspended in methylcellulose (100 μg/kg; 0.2 ml/100 g from the 50 μg/ml solutions) was administered p.o. 60 min before the measurements. Rats in the control group were treated with the same volume of the methylcellulose vehicle. There were 8 rats in all the 13 test compond groups. Separate solvent-treated control groups were used for each experimental block (n=2-5), but only one contracted control group (n=31) was used for the statistical analysis after completing the study.

[0193] Investigational Techniques

[0194] a) Touch sensitivity of the plantar surface of the paw was measured with the Ugo Basile Dynamic Plantar Aesthesiometer (DPA; 37400, Comerio, Italy), which is an electronic von Frey device. The rats move about freely in one of the two compartments of the enclosure positioned on the metal mesh surface. Following acclimation after cessation of exploratory behaviour, the operator places the touch stimulator unit under the animal's paw, using the adjustable angled-minor to position the filament below the target area of the paw. After pressing the “start” key an electrodynamic actuator of proprietary design lifts a straight metal filament, which touches the plantar surface and begins to exert an increasing upward force at a preset rate of application until a stop signal (when the animal removes the paw) is attained. The paw withdrawal threshold is numerically shown in grams on the digital screen (Helyes et al. 2004). Since this touch stimulus is not painful on the intact paw, its decrease after the incision expressed in percentage compared to the preoperation control values is considered to be mechanical allodynia.

[0195] b) The thermonociceptive threshold of the paw was determined with an increasing temperature water bath developed and validated in our laboratories in cooperation with Experimetria Ltd. (Budapest, Hungary). The equipment is suitable for the determination of the behavioural noxious heat threshold of rats defined as the lowest temperature at which the animal withdraws its hindpaw immersed into the water bath. The equipment consists of a tap water-filled container and a controlling unit. The cylindric plastic container (120 mm inner diameter, 140 mm height) is equipped with a built-in heating unit in its bottom that provides a homogenous and fast increase in the water temperature. The controlling unit has a 30° C. starting temperature, heating rate and a display continuously showing the actual bath temperature measured by a thermocouple at the middle position 35 mm below the water level. Heating can be interrupted by a foot switch and the corresponding bath temperature remains on the display to be recorded. After each measurement, the water bath is cooled back to the starting temperature by pumping cold water into the container controlled by a feedback mechanism while the excess water is drained through a spillway (Bölcskei et al. 2007). A starting temperature of 30° C. and a heating rate of 24° C./min was employed and the cut-off temperature was set to 53° C. Rats were lightly restrained and held in an upright position above the water bath allowing free movement of the hindlimbs. One of the hindpaws was immersed into the water and the heating process was started afterwards. At the moment when the animal withdrew its paw, heating was immeditely stopped by the foot switch and the corresponding temperature was recorded as the noxious heat threshold of the examined paw. Two control threshold masurements separated by a 30 min interval were performed for the same paw of each animal and the mean of the two values was used for analysis. The significant drop of the thermonociceptive threshold after the incision is considered as heat allodynia (see FIG. 3).

[0196] Results:

[0197] Plantar incision evoked 27.43-41.97% mechanical allodynia, which was significantly reduced by two BST compounds (BST1415 (example 51) and BST1658 (example 58)). BST1415 (example 51) caused 63%, BST1658 example 58) evoked 64.7% decrease of mechanical allodynia measured by dynamic plantar aesthesiometry (FIG. 4). Plantar incision also elicited 6-8° C. decrease of the heat threshold which effect was signicantly inhibited by BST-1413. This compound had 18.2% effectiveness (FIGS. 6 and 7).

BIOLOGICAL EXAMPLE 5

[0198] Neuropathic Mechanical Hyperalgesia and Allodynia Induced by Partial Tight Ligation of the Sciatic Nerve (Traumatic Mononeuropathy Model)

[0199] Experimental Model (Seltzer-Operation)

[0200] Wistar rats were anaesthetised with sodium-pentobarbital (Euthasol, 50 mg/kg i.p.). The common sciatic nerve was exposed unilaterally on the right side high in the thigh and ⅓-½ of the nerve trunk was carefully separated and tightly ligated using a siliconised silk suture (Ethicone 9-0). Then the wound was closed and the animals were allowed to survive for 7 days (Seltzer et al., 1990). During this period, signs of spontaneous pain (holding the legs in elevated position), mechanical hyperalgesia and allodynia developed.

[0201] Mechanonociceptive threshold of the hindpaws was measured with analgesimetry (Randall-Sellitto test) and touch sensitivity of the plantar surface with dynamic plantar aesthesiometry on the same animals. Hyperalgesia (decrease of the mechanonociceptive threshold) and allodynia (decrease of touch sensitivity) were expressed in % compared to the initial pre-operation control values. Significant decrease of the mechanonociceptive thresholds, as well as touch sensitivity thresholds developed 7 days after the surgery (Szolcsanyi et al. 2003; Sandor et al. 2006).

[0202] Protocol

[0203] One hundred and twenty seven (127) Wistar rats of both sexes (50 males and 77 females; 180-350 g) were used in the experiments. kept in the Animal House of the University of Pecs in a temperature-controlled room and provided with a 12-hour light-dark cycle, standard rat chow and water ad libitum were studied in this experimental series. They were divided into 14 experimental groups: 13 for the examined compounds and one vehicle-treated control group, all of them were composed of both males and females equally. Animals were brought to the air-conditioned laboratory the day before the study started. Throughout all the experiments the same assistant handled all the animals and they were habituated to the measurement's conditions by performing two conditioning measurements, the results of which were not included in the final analysis. The observer was blind to the drug treatment of the animals. Three control threshold measurements were made on three consecutive days prior to the nerve ligation. Seven days after the surgery pre-dose control measurements were done first with the DPA and then with the analgesimeter. Test compounds were administered p.o. and post-dose threshold measurements with both pices of equipment were performed 60 min later. Three consecutive measurements were executed on both paws and the means of these 3-3 values were used for analysis.

[0204] The examined compounds suspended in methylcellulose (100 μg/kg; 0.2 ml/100 g from the 50 μg/ml solutions) were administered p.o. Rats in the control group were treated with the same volume of the vehicle. There were 8 rats in all test compound groups. Solvent-treated control rats were investigated in every experimental block (n=2-8), but only one contracted control group (n=23) was used for the statistics. Allodynia (DPA) and hyperalgesia (Randall-Sellitto) were expressed in % values compared to the respective values before drug treatment on the same day.

[0205] Investigational Techniques

[0206] a) Touch sensitivity of the plantar surface of the paw was measured with the Ugo Basile Dynamic Plantar Aesthesiometer (37400, Comerio, Italy), as described above. Since this stimulus is not painful on the intact rat paw, its decrease after the surgery is considered to be mechanical allodynia.

[0207] b) The mechanonociceptive thresholds of the hindpaw was measured with the Ugo Basile Analgesimeter (7210, Comerio, Italy; Randall-Selitto test). Continuously increasing pressure was applied on the paw of conscious rats with a cone-shaped plastic pusher. The threshold force which elicited withdrawal was read on an analog scale calibrated in grams. This pressure is slightly painful on the intact rat paw, therefore, its decrease after nerve ligation is called mechanical hyperalgesia according to the terminology of the International Association for the Study of Pain.

[0208] Results:

[0209] Partial sciatic nerve-ligation (Seltzer operation) evoked 34.91-45.79% mechanical allodynia measured by dynamic plantar aesthesiometry, which was not significantly altered by any examined BST compounds (FIG. 8). This operation also exerted 24.25-37.36% mechanical hyperalgesia measured by analgesimetry (Randall-Sellitto test), and despite the allodynia, it was significantly reduced by BST-1659(example 4) and BST-1684(example 39) by 46% and 31%, respectively (FIG. 9).