SSTR4 AGONIST SALTS

Abstract

The present invention relates to specific salts of (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide, to pharmaceutical compositions comprising said salts, to methods of using said salts to treat physiological disorders, and to intermediates useful in the synthesis of the salts.

Claims

1. A compound of the formula: ##STR00013## or a hydrate thereof.

2. The compound of claim 1, wherein the compound is a hydrate.

3. The compound of claim 1, wherein the compound is a hydrate, wherein the water content at ambient temperature is in the range of 3% to 9% by weight.

4. The compound of claim 1, wherein the compound is: ##STR00014##

5. The compound of claim 4, wherein the compound is crystalline.

6. The compound of claim 1, wherein the compound is: ##STR00015##

7. A compound of the formula: ##STR00016##

8. The compound of claim 7, wherein the compound is crystalline.

9. A compound of the formula: ##STR00017##

10. The compound of claim 9, wherein the compound is crystalline.

11. The compound of claim 4, wherein the compound is crystalline and is characterized by an X-ray powder diffraction pattern using CuKα radiation comprising a peak at diffraction angle 2-theta 15.2°±0.2°, and one or more peaks selected from 10.6°±0.2° and 21.9°±0.2°.

12. The compound of claim 7, wherein the compound is crystalline and is characterized by an X-ray powder diffraction pattern using CuKα radiation comprising a peak at diffraction angle 2-theta 20.8°±0.2°, and one or more peaks selected from 10.3°±0.2°, 16.2°±0.2°, and 5.4°±0.2°.

13. The compound of claim 9, wherein the compound is crystalline and is characterized by an X-ray powder diffraction pattern using CuKα radiation comprising a peak at diffraction angle 2-theta 18.1°±0.2°, and one or more peaks selected from 4.9°±0.2° and 17.3°±0.2°.

14. A pharmaceutical composition comprising the compound of claim 1 and one or more pharmaceutically acceptable carriers, diluents, or excipients.

15. A method of treating pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 1.

16. A method of treating chronic back pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 1.

17. A method of treating neuropathic pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 1.

18. The method of claim 17, wherein the neuropathic pain is diabetic peripheral neuropathic pain.

19. A method of treating pain associated with osteoarthritis in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 1.

20. A method of treating pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 7.

21. A method of treating chronic back pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 7.

22. A method of treating neuropathic pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 7.

23. The method of claim 22, wherein the neuropathic pain is diabetic peripheral neuropathic pain.

24. A method of treating pain associated with osteoarthritis in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 7.

25. A method of treating pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 9.

26. A method of treating chronic back pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 9.

27. A method of treating neuropathic pain in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 9.

28. The method of claim 27, wherein the neuropathic pain is diabetic peripheral neuropathic pain.

29. A method of treating pain associated with osteoarthritis in a patient comprising administering to said patient in need of such treatment an effective amount of the compound of claim 9.

Description

EXAMPLE 1

Crystalline (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide L-tartrate sesquihydrate

[0045] ##STR00010##

[0046] (1S,5R)-(1α,5α,6α)-N-[1,1-Dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide L-tartrate (60 g, 136.5 mmol) is transferred into a 250 mL reactor vessel and THF/water 95:5 v/v is added to a volume of 225 mL. The mixture is heated to 60° C. and water is added in 1 mL aliquots to fully dissolve the starting material (total 8 mL of water). The reactor is allowed to cool naturally, and the mixture is allowed to stir at RT over the weekend. The resulting crystals are isolated by vacuum filtration and air-dried for several days. The resulting solid is sieved to give the title compound (42.3 g, 66%).

EXAMPLE 2

Crystalline (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide citrate

[0047] ##STR00011##

[0048] (1S,5R)-(1α,5α,6α)-N-[1,1-Dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide (10.8 g, 33 mmol) is dissolved in absolute ethanol (200 mL) while stirring at 300 rpm at 60° C. This solution is filtered through a 0.65 μm nylon filter to yield a clear solution. The solution is stirred for 5 min upon which solid precipitation occurs. A solution of citric acid (7.06 g, 36 mmol) dissolved in absolute ethanol (60 mL) at 60° C. is prepared. The citric acid solution is added slowly at 60° C. The mixture is filtered through a 0.45 μm syringe filter maintained at 60° C. Heating is then terminated and the mixture is stirred at 500 rpm, gradually cooled to RT. Upon complete equilibration to RT, a very thick white slurry (cake) is obtained. The flask is rinsed with absolute ethanol (5×10 mL) to rinse the cake. The cake solid is isolated on a nylon membrane under vacuum, dried under nitrogen, then overnight at 70° C. under vacuum to give the title compound as a white solid (16.8 g, 98%).

EXAMPLE 3

Crystalline (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide L-malate

[0049] ##STR00012##

[0050] (1S,5R)-(1α,5α,6α)-N-[1,1-Dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide (25 g, 88 mmol) is added to 100 mL of isopropanol while stirring at ˜400 rpm. The sample is heated to 60° C. 14.6 mL of L-malic acid solution in water (109 mmol) is then added. A clear yellowish solution is formed. The solution is cooled to RT. Oiling is observed, so the phase separation is evaporated to dryness under nitrogen stream. The solid residue is suspended in acetone and water for a recrystallization at 55° C. The 25 g freebase equivalent material is recrystallized in 200 ml of acetone and 15 mL of water (total 215 mL solvent). The solid is isolated from the reactor vessel at RT using a Buchner funnel under reduced pressure. The white cake is rinsed with acetone and dried at 50° C. under vacuum to give the title compound (21 g, 57%).

X-Ray Powder Diffraction (XRPD) Method 1

[0051] The XRPD patterns of crystalline solids are obtained on a Bruker D8 Endeavor X-ray powder diffractometer, equipped with a CuKα (1.5418 Å) source and a Lynxeye™ detector, operating at 40 kV and 40 mA. The sample is scanned between 4 and 42 2θ°, with a step size of 0.009 2θ° and a scan rate of 0.5 seconds/step, and using 0.3° primary slit opening, and 3.9° PSD opening. The dry powder is packed on a quartz sample holder and a smooth surface is obtained using a glass slide. The crystal form diffraction patterns are collected at ambient temperature and relative humidity. Crystal peak positions are determined in MDI-Jade after whole pattern shifting based on an internal NIST 675 standard with peaks at 8.853 and 26.774 2θ°. It is well known in the crystallographic art that, for any given crystal form, the relative intensities of the diffraction peaks may vary due to preferred orientation resulting from factors such as crystal morphology and habit. Where the effects of preferred orientation are present, peak intensities are altered, but the characteristic peak positions of the polymorph are unchanged. See, e.g. The United States Pharmacopeia #23, National Formulary #18, pages 1843-1844, 1995. Furthermore, it is also well known in the crystallography art that for any given crystal form the angular peak positions may vary slightly. For example, peak positions can shift due to a variation in the temperature at which a sample is analyzed, sample displacement, or the presence or absence of an internal standard. In the present case, a peak position variability of ±0.2 2θ° is presumed to take into account these potential variations without hindering the unequivocal identification of the indicated crystal form. Confirmation of a crystal form may be made based on any unique combination of distinguishing peaks.

X-Ray Powder Diffraction (XRPD) Method 2

[0052] The XRPD patterns of crystalline solids are obtained on a Bruker D4 Endeavor X-ray powder diffractometer, equipped with a CuKα (1.5418 Å) source and a Vantec™ detector, operating at 35 kV and 50 mA. The sample is scanned between 4 and 40 2θ°, with a step size of 0.008 2θ° and a scan rate of 0.5 seconds/step, and using 1.0 mm divergence, 6.6 mm fixed anti-scatter, and 11.3 mm detector slits. The dry powder is packed on a quartz sample holder and a smooth surface is obtained using a glass slide. The crystal form diffraction patterns are collected at ambient temperature and relative humidity. Crystal peak positions are determined in MDI-Jade after whole pattern shifting based on an internal NIST 675 standard with peaks at 8.853 and 26.774 2θ°. It is well known in the crystallography art that, for any given crystal form, the relative intensities of the diffraction peaks may vary due to preferred orientation resulting from factors such as crystal morphology and habit. Where the effects of preferred orientation are present, peak intensities are altered, but the characteristic peak positions of the polymorph are unchanged. See, e.g. The United States Pharmacopeia #23, National Formulary #18, pages 1843-1844, 1995. Furthermore, it is also well known in the crystallography art that for any given crystal form the angular peak positions may vary slightly. For example, peak positions can shift due to a variation in the temperature at which a sample is analyzed, sample displacement, or the presence or absence of an internal standard. In the present case, a peak position variability of ±0.2 2θ° is presumed to take into account these potential variations without hindering the unequivocal identification of the indicated crystal form. Confirmation of a crystal form may be made based on any unique combination of distinguishing peaks.

XRPD of Example 1

[0053] XRPD method 1 was used for Example 1. A prepared sample of Example 1 is characterized by an XRPD pattern using CuKα radiation as comprising diffraction peaks (2-theta values) as described in Table 1 below, and in particular comprising a peak at diffraction angle 2-theta of 15.2° and one or more of peaks at 10.6° and 21.9°; with a tolerance for the diffraction angles of 0.2 degrees.

TABLE-US-00001 TABLE 1 X-ray powder diffraction peaks of Example 1 Example 1 Angle Relative Intensity Peak (°2-Theta) ± 0.2° (% of most intense peak) 1 8.2 9.6% 2 10.6 16.3% 3 12.6 11.1% 4 12.9 13.7% 5 13.5 18.9% 6 14.6 21.2% 7 15.0 39.0% 8 15.2 100.0% 9 15.8 26.4% 10 16.2 22.9% 11 16.5 8.5% 12 17.6 39.6% 13 17.9 30.5% 14 18.4 40.7% 15 18.6 21.2% 16 19.5 46.8% 17 20.7 15.0% 18 21.3 33.3% 19 21.9 77.4% 20 22.9 27.3%

XRPD of Example 2

[0054] XRPD method 2 was used for Example 2. A prepared sample of Example 2 is characterized by an XRPD pattern using CuKα radiation as comprising diffraction peaks (2-theta values) as described in Table 2 below, and in particular comprising a peak at diffraction angle 2-theta of 20.8° and one or more of peaks at 10.3°, 16.2° and 5.4°, with a tolerance for the diffraction angles of 0.2 degrees.

TABLE-US-00002 TABLE 2 X-ray powder diffraction peaks of Example 2 Example 2 Angle Relative Intensity Peak (°2-Theta) ± 0.2° (% of most intense peak) 1 5.4 53.70% 2 8.1 11.00% 3 9.1 9.70% 4 10.3 60.00% 5 16.2 56.40% 6 19.9 22.40% 7 20.8 100.00% 8 21.5 14.00% 9 22.1 21.10% 10 24.5 42.80%

XRPD of Example 3

[0055] XRPD method 2 was used for Example 3. A prepared sample of Example 3 is characterized by an XRPD pattern using CuKα radiation as comprising diffraction peaks (2-theta values) as described in Table 3 below, and in particular comprising a peak at diffraction angle 2-theta of 18.1° and one or more of peaks at 4.9° and 17.3°, with a tolerance for the diffraction angles of 0.2 degrees.

TABLE-US-00003 TABLE 3 X-ray powder diffraction peaks of Example 3 Example 3 Angle Relative Intensity Peak (°2-Theta) ± 0.2° (% of most intense peak) 1 4.9 72.10% 2 14.9 100.00% 3 16.9 6.40% 4 17.3 11.00% 5 18.1 33.70% 6 19.3 10.90% 7 19.7 18.90% 8 20.6 17.70% 9 21.0 4.70% 10 23.9 15.00%

cAMP Assay

[0056] The activation of the SSTR4 receptor (G coupled) causes an inhibition of intracellular cAMP after stimulation with Forskolin, which can be quantifiable by use of a suitable assay Kit and an adequate plate reader. This technique is used to characterize pharmacological effects of the SSTR4 receptor agonists by use of hSSTR4 expressing H4 cells. The compound is dissolved and diluted in DMSO. The final test solution contains 1% DMSO. The cAMP standard (Lance™ cAMP 384 Kit; PerkinElmer, Cat# AD0264) is prepared in assay buffer (HBSS with 0.1% BSA, 5 mM HEPES, 0.5 M IBMX, pH 7.4) containing 1% DMSO and the cAMP standard curve is included at least on one plate. Cells are centrifuged and suspended in assay buffer (incl. 1:100 diluted Alexa Fluor® antibody). For the assay 5 μL of a cell suspension (approximately 5000 cells/well)-incl. Alexa Fluor® antibody (diluted 1:100) are added into a 384 well MTP microtiter plate excepting one row or column (depending on the plate layout), which is reserved for the standard curve. Then 2 μL of compound sample is added as concentration response curve (e.g., le-5 M to 6e-10 M), usually in triplicates. Each assay contains incubations with vehicle controls instead of compound as controls for non-inhibited cAMP generation (100% CTL; ‘high values’) and incubations with 1 μM Somatostatin as controls for full inhibition and background (0% CTL; ‘low values’). After approximately 10-15 min incubation time 3 μL Forskolin (dissolved in DMSO, final conc. 15 μM) is added. Then the plates are shaken briefly and incubated for 60 min at RT. After 60 min 10 μL of the detection mix is added into all wells followed by an additional incubation period of 1 h. The plates are read in a suitable plate reader. The analysis of the data is based on the “ratio” of the time-resolved fluorescence measurements of donor and acceptor fluorophore (Ex: 320 nm; Em1: 665 nm; Em2: 615 nm; ratio 665/615). From this ratio, cAMP concentrations are calculated from standard curve and the EC.sub.50 is estimated by least square curve fit program. The free base of Examples 1, 2 and 3 is tested essentially as described above.

TABLE-US-00004 TABLE 4 EC.sub.50 of Examples 1, 2 and 3 (free base) Example SSTR4 agonism EC.sub.50 (nM) 1, 2 and 3 (free base) 3.7

[0057] As shown in Table 4, Examples 1, 2 and 3, after being dissolved to their free base forms, are agonists of SSTR4.

Selectivity

[0058] In competition experiments, the test compound, which is not labeled, competes with the binding site of a labeled ligand. The displacement of the labeled ligand by the test compound leads to a decreased signal. For the binding experiments 200 μL of membrane homogenate from one of the following protein amounts is used: hSSTR1 (40 μg/well); hSSTR2 (25 μg/well); hSSTR3 (1.5 μg/well); hSSTR4 (0.5 μg/well); hSSTR5 (25 μg/well). The homogenate is incubated with 0.05 nM of radioligand ([3-125I-Tyr]-Somatostatin-(1-14)) in addition to increasing concentrations of a test compound or vehicle (100% binding) in a total volume of 250 μL using a Hepes buffer (10 mM, EDTA 1 mM, MgCl.sub.2 5 mM, pH 7.6, BSA 0.5%, Bacitracin 0.003%, DMSO 1%) for 180 min at RT. The incubation is terminated by filtration with ice cold NaCl 0.9% through polyethyleneimine treated (0.3%) grade GF/B glass fiber filters using a cell harvester. The protein-bound radioactivity is measured in a suitable reader. The non-specific binding is defined as radioactivity bound in the presence of 1 μM Somatostatin-14 during the incubation period. The analysis of the concentration-binding curves is performed by computer-assisted nonlinear least square curve fitting method using the model of one receptor binding site.

TABLE-US-00005 TABLE 5 Selectivity of Examples 1, 2 and 3 (free base) SSTR4 SSTR1 SSTR2 SSTR3 SSTR5 binding binding binding binding binding Example K.sub.i (nM) K.sub.i (nM) K.sub.i (nM) K.sub.i (nM) K.sub.i (nM) 1, 2 and 3 (free base) 39.9 >9148 >9603 >8618 >9863

[0059] As shown in Table 5, Examples 1, 2 and 3, after being dissolved to their free base forms, selectively bind to SSTR4 over SSSTR1, SSSTR2, SSSTR3 and SSSTR5.

Stability Study

[0060] Prototype tablets of (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2-[(3-methyl pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide (Tablet A), Example 1 (Tablet B) and Example 3 (Tablet C) were prepared with the formulations shown in Tables 6, 7 and 8 respectively.

TABLE-US-00006 TABLE 6 Formulation of Tablet A Material % w/w (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2- 50.00 [(3-methyl-2-pyridyl)oxy]ethyl]-3- azabicyclo[3.1.0]hexane-6-carboxamide Microcrystalline cellulose 42.00 Croscarmellose sodium 5.00 Sodium stearyl fumarate 3.00 Total 100

TABLE-US-00007 TABLE 7 Formulation of Tablet B Material % w/w Example 1 65.00 Microcrystalline cellulose 26.50 Croscarmellose sodium 5.00 Sodium stearyl fumarate 3.50 Total 100

TABLE-US-00008 TABLE 8 Formulation of Tablet C Material % w/w Example 3 65.00 Microcrystalline cellulose 26.50 Croscarmellose sodium 5.00 Sodium stearyl fumarate 3.50 Total 100

[0061] The tablets were subjected to stability testing according to ICH guidelines using accelerated storage conditions (40° C./75% RH) for 1, 2-, 4-, 8- and 12-week periods).

[0062] For chromatographic analysis, one tablet is dissolved in 50/50 mobile phase A/mobile phase B (see HPLC chromatography conditions below) to obtain a sample concentration of about 0.2 mg/mL as (1S,5R)-(1α,5α,6α)-N-[1,1-dimethyl-2-[(3-methyl-2-pyridyl)oxy]ethyl]-3-azabicyclo[3.1.0]hexane-6-carboxamide (free base). The sample is then analyzed by HPLC chromatography (XBridge™ BEH C18, 2.5 μm, 4.6 mm×75 mm I.D; mobile phase: A=H.sub.2O 99.9%+0.1% TFA, B=99.9% CH.sub.3CN+0.1% TFA; gradient: 0.0 min 5% B.fwdarw.12.1 min 70% B.fwdarw.13.0 min 95% B.fwdarw.16.0 min 95% B 16.1 min 5% B.fwdarw.20.0 min 5% B; flow rate: 1.5 mL/min; column temperature: 30° C.; detection: UV 220 nm; injection volume: 10 μL; autosampler temperature: ambient). Individual standard curves were prepared for each sample tested.

[0063] Table 9 shows the total related substances percentage (TRS) formed during the stability testing.

TABLE-US-00009 TABLE 9 Impurity profiles for Tablets A, B and C (storage conditions: 40° C./75% RH). Time Tablet A Tablet B Tablet C (weeks) TRS (%) TRS (%) TRS (%) 1 0.33 0.00 0.00 2 0.55 0.00 0.00 4 1.40 0.18 0.21 8 2.56 0.09 0.30 12 3.08 0.07 0.71

[0064] The results show that the L-tartrate salt (Example 1, Tablet B) and the L-malate salt (Example 3, Tablet C) possess improved stability in excipients under accelerated storage conditions compared to their respective free base. Furthermore, the results show that the L-tartrate salt (Example 1, Tablet B), possesses improved stability in excipients compared to the L-malate salt (Example 3, Tablet C).