CRYSTALLINE SALT FORMS OF MESEMBRINE
20230312469 · 2023-10-05
Inventors
Cpc classification
C07C309/29
CHEMISTRY; METALLURGY
International classification
Abstract
The present invention relates to novel crystalline salt forms of mesembrine, also known as 3a-(3,4-dimethoxyphenyl)-octahydro-1-methy-6H-indol-6-one. Mesembrine has the chemical formula C.sub.17H.sub.23NO.sub.3. The invention further relates to the preparation of a novel crystalline salt of mesembrine and to the use of the mesembrine salt as a medicament. In one embodiment the novel crystalline salt form of mesembrine is mesembrine besylate salt.
Claims
1. A mesembrine salt, wherein the salt is mesembrine besylate; mesembrine phosphate; mesembrine tartrate; mesembrine fumarate and mesembrine succinate.
2. The mesembrine salt according to claim 1, wherein the salt is mesembrine besylate salt.
3. The mesembrine salt according to claim 1, wherein the salt is in a solid form.
4. The mesembrine salt according to claim 1, wherein the salt is in a crystalline form.
5. The mesembrine salt according to claim 2, characterized by an XRPD pattern of
6. The mesembrine salt according to claim 5, characterized by an XRPD pattern comprising peaks at about the positions as described in Table 3.10.
7. The mesembrine salt according to claim 2, characterized by an XRPD pattern of
8. The mesembrine salt according to claim 7, characterized by an XRPD pattern comprising peaks at about the positions as described in Table 3.13.
9. A crystalline form of mesembrine characterized by peaks in an XPRD pattern at 11.1±0.2, 12.7±0.2, 16.6±0.2, 23.8±0.2, and 24.6±0.2°2θ.
10. The crystalline form of mesembrine according to claim 9, further characterized by at least one peak selected from 9.2±0.2, 11.0±0.2, 13.5±0.2, 19.5±0.2, 20.7±0.2, and 21.2±0.2°2θ.
11. The crystalline form of mesembrine according to claim 9, wherein the crystalline form is characterized by peaks in a XRPD pattern at 9.2±0.2, 11.0±0.2, 11.1±0.2, 12.3±0.2, 12.7±0.2, 13.5±0.2, 15.4±0.2, 16.6±0.2, 18.5±0.2, 19.5±0.2, 19.8±0.2, 20.2±0.2, 20.7±0.2, 21.2±0.2, 21.6±0.2, 22.4±0.2, 22.9±0.2, 23.2±0.2, 23.8±0.2, 24.1±0.2, 24.6±0.2, 25.6±0.2, 26.2±0.2, 27.9±0.2, 28.3±0.2, 28.6±0.2, 29.3±0.2, 31.1±0.2, 32.4±0.2, 33.0±0.2, and 33.9±0.2°2θ.
12. A crystalline form of mesembrine characterized by peaks in an XPRD pattern at 11.0±0.2, 13.4±0.2, 15.1±0.2, 18.6±0.2, or 23.7±0.2°2θ.
13. The crystalline form of mesembrine according to claim 12, further characterized by at least one peak selected from 15.6±0.2, 16.1±0.2, 18.2±0.2, 21.3±0.2, or 25.1±0.2°2θ.
14. The crystalline form of mesembrine according to claim 12, wherein the crystalline form is characterized by peaks in a XRPD pattern at 3.2±0.2, 7.4±0.2, 9.3±0.2, 11.0±0.2, 11.6±0.2, 12.1±0.2, 12.6±0.2, 13.4±0.2, 14.5±0.2, 15.1 ±0.2, 15.6±0.2, 16.1±0.2, 16.8±0.2, 17.9±0.2, 18.2±0.2, 18.6±0.2, 18.8±0.2, 19.5±0.2, 19.8±0.2, 20.7±0.2, 21.3±0.2, 21.8±0.2, 22.4±0.2, 22.6±0.2, 22.7±0.2, 23.3±0.2, 23.7±0.2, 24.1±0.2, 24.3±0.2, 24.7±0.2, 25.1±0.2, 25.7±0.2, 26.3±0.2, 26.6±0.2, 27.0±0.2, 27.5±0.2, 28.0±0.2, 28.5±0.2, 29.0±0.2, 29.3±0.2, 29.5±0.2, 30.0±0.2, 30.7±0.2, 31.7±0.2, 32.1±0.2, 32.5±0.2, 33.1±0.2, 33.5±0.2, and 34.4±0.2°2θ.
15. A pharmaceutical comprising the mesembrine salt according to claim 1.
16. A pharmaceutical comprising the mesembrine salt according to claim 9.
17. A pharmaceutical comprising the mesembrine salt according to claim 12.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0110] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:
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DEFINITIONS
[0134] Various definitions are made throughout this document. Most words have the meaning that would be attributed to those words by one skilled in the art. Words specifically defined either below or elsewhere in this document have the meaning provided in the context of the present invention as a whole and as typically understood by those skilled in the art.
[0135] The term “substantially crystalline” means at least about 50% crystalline and ranging up to about 100% crystalline. The present invention provides a salt that is at least about 50% crystalline, at least about 60% crystalline, at least about 70% crystalline, at least about 80% crystalline, at least about 90% crystalline, at least about 95% crystalline, at least about 98% crystalline, or at least about 100% crystalline in form.
[0136] The degree or percentage of crystallinity may be determined by the skilled person using X-ray powder diffraction (XRPD). Other techniques, such as solid-state nuclear magnetic resonance (NMR), FT-IR, Raman spectroscopy, differential scanning calorimetry (DSC) and microcalorimetry, may also be used.
[0137] Crystalline forms of the salt of the invention may be in the form of a solvate, including but not limited to a hydrate (e.g., a monohydrate), or otherwise (e.g., in the form of an anhydrate).
[0138] “Subject,” “individual” or “patient” is used interchangeably herein and refers to a vertebrate, preferably a mammal. Mammals include, but are not limited to, murines, rodents, simians, humans, farm animals, sport animals and pets.
[0139] “Treating” or “treatment” of any disease or disorder refers, in some embodiments, to ameliorating the disease or disorder (i.e., arresting or reducing the development of the disease or at least one of the clinical symptoms thereof,). Treatment may also be considered to include preemptive or prophylactic administration to ameliorate, arrest or prevent the development of the disease or at least one of the clinical symptoms. Treatment can also refer to the lessening of the severity and/or the duration of one or more symptoms of a disease or disorder. In a further feature, the treatment rendered has lower potential for long term side effects over multiple years. In other embodiments “treating” or “treatment” refers to ameliorating at least one physical parameter, which may not be discernible by the patient. In yet other embodiments, “treating” or “treatment” refers to inhibiting the disease or disorder, either physically, (e.g., stabilization of a discernible symptom), physiologically, (e.g., stabilization of a physical parameter) or both. In yet other embodiments, “treating” or “treatment” refers to delaying the onset of the disease or disorder.
[0140] “Therapeutically effective amount” means the amount of a compound that, when administered to a patient for treating a disease, is sufficient to effect such treatment for the disease. The “therapeutically effective amount” will vary depending on the compound, the disease and its severity and the age, weight, adsorption, distribution, metabolism and excretion etc., of the patient to be treated.
[0141] “Vehicle” refers to a diluent, excipient or carrier with which a compound is administered to a subject. In some embodiments, the vehicle is pharmaceutically acceptable.
[0142] “Active ingredient” or “Active pharmaceutical ingredient” or “API” refers to the novel mesembrine salt of the invention.
[0143] Mesembrine is a chiral alkaloid with the CAS name: (3aS-cis)-3a-(3,4-Dimethoxyphenyl)octahydro-1-methyl-6H-indol-6-one. It occurs naturally at the cis-isomer but may also be synthesized as the trans-isomer or as a racemate. The structures below denote the structural configuration of mesembrine. The mesembrine of the present invention may occur as the cis-isomer, the trans-isomer or a racemate of the two.
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DETAILED DESCRIPTION OF THE INVENTION
[0144] The Examples below describe the phases of development of a highly soluble and characterized mesembrine salt of the present invention. The applicant has determined that mesembrine is poorly soluble in aqueous systems and as such means that the use of the compound as an active pharmaceutical ingredient in medicinal presentations is limited by its lack of solubility. A novel salt form has been produced which is both soluble and stable and as such is able to be used in the preparation of medicines and supplements.
[0145] Mesembrine can be isolated from extracts of S. tortuosum or can be synthesized chemically using the method described by Wang et al., 2016.
Example 1: Characterisation of Mesembrine
Materials and Methods
[0146] The mesembrine used in the following series of experiments was isolated from an extract of Sceletium tortuosum, the compound was characterized by several different methods in order to determine the purity of the starting material and to benchmark it against the subsequent salts that were to be formed.
[0147] HPLC analysis was carried out to determine the chemical purity of the mesembrine and to provide information on any impurities. The following conditions were use: [0148] Column: Waters Acquity BEH C18 1.7 μm 150 mm×2.1 mm [0149] Column Temperature: 33° C. [0150] Autosampler Temperature: 25° C. [0151] UV Wavelength: 280 nm [0152] Injection Volume: 5 μL [0153] Flow Rate: 0.29 mL/min [0154] Mobile Phase A: 0.1% NH4 in H2O [0155] Mobile Phase B: Methanol:Water 20:80% v/v [0156] Gradient Program:
TABLE-US-00003 Time (minutes) Mobile Phase A [%] Mobile Phase B [%] 0.00 80 20 2.0 80 20 4.0 60 40 6.0 50 50 9.0 50 50 14.0 10 90 17.0 10 90 17.1 80 20 23.0 80 20
[0157] .sup.1H and .sup.1H/.sup.13C NMR analysis were carried out in order to determine the chemical structure of the mesembrine used. NMR experiments were performed on a Bruker AVIIIHD spectrometer equipped with a DCH cryoprobe operating at 500.12 MHz for protons. Experiments were performed in deuterated DMSO, and each sample was prepared to ca. 10 mM concentration.
[0158] The infrared (IR) spectrum was additionally recorded in order to obtain a benchmark of the starting mesembrine material. The following conditions were used Infrared spectroscopy was carried out on a Bruker ALPHA P spectrometer. Sufficient material was placed onto the centre of the plate of the spectrometer and the spectra were obtained using the following parameters: [0159] Resolution: 4 cm−1 [0160] Background Scan Time: 16 scans [0161] Sample Scan Time: 16 scans [0162] Data Collection: 4000 to 400 cm−1 [0163] Result Spectrum: Transmittance [0164] Software: OPUS version 6
[0165] A Karl Fischer (KF) analysis was finally undertaken in order to determine the water content of the mesembrine sample used. The following conditions were used Solids were analysed either using a vaporizer method, or using an external dissolution method:
[0166] Vaporizer method: Approximately 10 mg of material was weighted into a 10 mL glass vial and tightly sealed with a screw cap. The water content of the samples was analysed using an InMotion KFoven Autosampler, at 150° C. The samples were run in duplicate, and an average moisture content reported.
TABLE-US-00004 Blank Oven Temperature 150° C. Source for Drift Determination Max. Start Drift 10 μg/min Carrier Gas Flow Rate 80 mL/min Transfer Tube Heating No Mix Time 60 s Stir Speed 45% Drift Termination 10 s (Delay Time) Max. Titration Time 600 s Sample Oven Temperature 150° C. Source for Drift Determination Max. start Drift 10 μg/min Carrier Gas Flow Rate 80 mL/min Mix Time 60 s Stir Speed 45% Drift Termination 10 s (Delay Time) Max. Titration Time 600 s
[0167] External Dissolution method: A known mass of the sample to be analysed was dissolved in a known mass of methanol. Prior to analysis being carried out, solvent blank measurements were carried out. Approximately 1 mL of methanol was injected into the titration cell of a Mettler Toledo C30 compact titrator, and the syringe back-weighed to determine the weight of methanol added.
[0168] For the sample analysis, approximately 1 mL of the solution was injected into the titration cell, and the syringe back-weighed and the weight of the added solution entered onto the instrument. Titration was initiated once complete dissolution was observed, and the water content was automatically calculated by the instrument. The measurement was carried out in duplicate and an average water content reported.
Results
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Conclusion
[0173] The characterization of mesembrine determined that the sample used for salt formation assessment was of an acceptable purity, matched the expected chemical structure for mesembrine and comprised an acceptable level of water.
[0174] The mesembrine sample was therefore suitable for use in additional experiments to assess the ability of salt formation.
Example 2: Solubility of Mesembrine
Materials and Methods
[0175] Approximately 360 mg of mesembrine was weighed out and dissolved in 5 mL of dichloromethane (DCM). After dissolution 278 μL of the solution was aliquoted into pre-tared vials, and the solvent allowed to evaporate at ambient conditions for 1 h. The vials were then dried at 20° C. under vacuum for ca. 22 h. After drying, the vials were back-weighed to determine the mass of mesembrine in each vial.
[0176] The miscibility study was carried out by adding aliquots of the desired solvent system to each vial. The following aliquot sizes were used: Aliquot numbers 1-10—20 μL; 11-16—50 μL; 17-19—200 μL; 20—750 μL.
[0177] In between additions the experiment was heated to 40° C. for ca. 5 minutes to facilitate miscibility/solubility. Additions were continued until miscibility was observed, or ca. 100 volumes (2 mL) had been added.
Results
[0178] Table 2.1 below details the approximate solvent miscibility/solubility of mesembrine in the 18 different solvents tested.
TABLE-US-00005 TABLE 2.1 Solubility of mesembrine in various solvents # Solvent/% v/v Miscibility/mg/mL 1 2-Methyl THF >845 2 1,4-Dioxane >850 3 2-Propanol (IPA) >870 4 Acetone >890 5 Acetonitrile >855 6 2-Propanol:Water (50:50) >870 7 DMSO >288 8 Ethanol >630 9 Ethyl acetate >445 10 Heptane <9 11 Isopropyl acetate >900 12 Methanol >455 13 Methyl ethyl ketone (MEK) >915 14 N-Methyl-2-pyrrolidone (NMP) >450 15 Tert-butyl methyl ether >465 16 Tetrahydrofuran (THF) >381 17 Toluene >455 18 Water <9
[0179] As can be seen in Table 2.1 mesembrine was very poorly soluble in heptane and water and had a reasonable solubility in ethanol and other organic solvents.
Conclusion
[0180] Many organic solvents are classed as toxic or carcinogenic and as such are not suitable for use as diluents in pharmaceutical compositions.
[0181] The low solubility of mesembrine in water means that the compound will be difficult to formulate into a pharmaceutical composition as only a small mass of the compound can be dissolved in water.
[0182] In a study determining the toxicity of Zembrin®, an extract of Sceletium tortusosum, which comprises ca.20% mesembrine, the no observed adverse effect level (NOAEL) was determined to be 420 mg extrapolated to a 70 kg human (Murbach et al., 2014).
[0183] Therefore, a dose of around 84 mg of mesembrine (20% of 420 mg) would require approximately 10 ml of water to form a miscible solution, this amount being far higher than the standard 00 capsule size used for medication delivery which has a fill volume of 0.9 ml.
Example 3: Primary Salt Formation Assessment
Materials and Methods
[0184] The primary salt formation was assessed using reactions with 12 counterions across six solvent systems. The various counterions were selected based on their pKa, and also as a result of their molecular weight, toxicity and diversity. The counterions and solvents used for the primary salt formation assessment are as detailed in Table 3.1 below.
TABLE-US-00006 TABLE 3.1 Counterions and solvent details Upper Merck Solvent Temp. # Counterions MW/g/mol pKa Class System/% v/v Limit/º C. 1 Hydrochloric acid 36.46 −6 1 THF 40 2 Sulfuric acid 98.08 −3 1 Ethyl acetate 3 p-Toluenesulfonic acid 172.2 −1.34 2 Ethanol 4 Methanesulfonic acid 96.10 −1.2 2 IPA:Water 50:50 5 Benzenesulfonic acid 158.18 0.7 2 MEK 6 Maleic acid 116.08 1.92; 6.23 1 Acetonitrile 7 Phosphoric acid 98.00 1.96; 7.12; 12.32 1 8 (+)-L-Tartaric acid 150.09 3.02; 4.36 1 9 Fumaric acid 116.08 3.03; 4.38 1 25 10 Citric acid 192.13 3.13; 4.76; 6.40 1 11 Succinic acid 118.09 4.21; 5.64 1 12 Benzoic acid 179.18 4.3 3
[0185] Stock solutions of mesembrine at 200 mg/mL were prepared in the desired solvent systems. Separately, 1.1 equivalents of counterion were dispensed (either weighed, or measured using an autopipette) into 72×2 mL vials and a stirrer bar added.
[0186] 100 μL of the appropriate solvent system was added to each vial to dissolve/suspend the counterion. 100 μL of the mesembrine stock solution in the correct solvent system was added to each vial, at the specified upper temperature limit.
[0187] The experiments were then temperature cycled between the upper temperature limit (specified in Table 3.1) and 5° C. at 0.1° C./min, with 1 h holds at the upper temperature limit, and 5° C. for ca. 72 h.
[0188] After temperature cycling, solids were isolated from experiments at 5° C., and analysed by XRPD. Any experiments which did not contain solids had anti-solvent addition carried out and were temperature cycled for a further ca. 24 h as above.
[0189] Solids were dried at 40° C. under vacuum for ca. 24 h, and then re-analysed by XRPD.
[0190] Solids were then stored at 40° C./75% RH for ca. 24 h, and then re-analysed by XRPD.
[0191] Potential salt forms were also analysed by TGA/DSC.
[0192] Additional experiments were carried out for selected counterions (numbers 2, 3, 4 and 6 from Table 3.1) had not yielded any solids of a potential salt of mesembrine from the initial set of salt formations. The upper temperature limit was decreased from 40° C. to 25° C. as degradation was noted in these during the initial experiments as detailed below and in Table 3.2.
[0193] A stock solution of mesembrine at 200 mg/mL was prepared in MEK. Separately, 1.1 equivalents of counterion were dispensed (either weighed, or measured using an autopipette) into 4×2 mL vials and a stirrer bar added.
[0194] 100 μL of MEK was added to each vial to dissolve/suspend the counterion. 100 μL of the mesembrine stock solution was added to each vial, at 25° C.
[0195] The experiments were then temperature cycled between 25° C. and 5° C. at 0.1° C./min, with 1 h holds at 25° C. and 5° C. for ca. 72 h. After temperature cycling, anti-solvent addition carried out in 100 μL aliquots, at 5° C. until a visual change was observed or 1 mL of heptane had been added.
[0196] The experiments were temperature cycled for a further ca. 24 h as above.
TABLE-US-00007 TABLE 3.2 Counterions and solvent details for additional salt formation assessment Solvent Upper MW/ Merck System/ Temp. # Counterions g/mol pKa Class % v/v Limit/º C. 1 p-Toluenesulfonic 172.2 −1.34 2 MEK 25 acid 2 Methanesulfonic 96.10 −1.2 2 acid 3 Maleic acid 116.08 1.92; 6.23 1 4 Sulfuric acid 98.08 −3 1
Results
[0197] The primary salt formation assessment from reactions with 12 counterions across six different solvent systems were determined. The results of the primary salt screen are summarized in Tables 3.3 to 3.5 below.
TABLE-US-00008 TABLE 3.3 Summary of damp XRPD analysis from primary formation assessment Ethyl IPA:Water Counterions THF Acetate Ethanol 50:50% v/v MEK MeCN Hydrochloric acid 1, C 1, PC 1, C — 1, C 1, C Sulfuric acid — — — — — — p-Toluenesulfonic acid — — — — — — Methanesulfonic acid — — — — — — Benzenesulfonic acid 1, C 1, C 1, C — 1, C 1, C Maleic acid — — — — — — Phosphoric acid 1, PC A 2, PC — 1, PC — (+)-L-Tartaric acid A U 1, PC — 1, PC 1, C Fumaric acid 1, PC 2, C 2, C — 1, PC 3, C Citric acid A U — — A A Succinic acid — U — — 1, C — Benzoic acid — — — — — — Key A Amorphous # Pattern number C Crystalline potential salt PC Poorly crystalline U Counterion (unreacted) — No solids
TABLE-US-00009 TABLE 3.4 Summary of dry XRPD analysis from primary formation assessment Ethyl IPA:Water Counterions THF Acetate Ethanol 50:50% v/v MEK MeCN Hydrochloric acid 1, C 1, PC 1, C — 1, C 1, C Sulfuric acid — — — — — — p-Toluenesulfonic acid — — — — — — Methanesulfonic acid — — — — — — Benzenesulfonic acid 1, C 1, C 1, C — 1, C 1, C Maleic acid — — — — — — Phosphoric acid 1, PC A 2, PC — 1, PC — (+)-L-Tartaric acid 1, PC U 1, PC — 1, PC 1, C Fumaric acid 1, PC 2, C 2, C — 1, PC 3, C Citric acid A U — — A A Succinic acid — U — — 1, C — Benzoic acid — — — — — — Key A Amorphous # Pattern number C Crystalline potential salt PC Poorly crystalline U Counterion (unreacted) — No solids
TABLE-US-00010 TABLE 3.5 Summary of 40° C./75% RH XRPD analysis from primary formation assessment Ethyl IPA:Water Counterions THF Acetate Ethanol 50:50% v/v MEK MeCN Hydrochloric acid 1, C A 1, C — 1, C 1, C Sulfuric acid — — — — — — p-Toluenesulfonic acid — — — — — — Methanesulfonic acid — — — — — — Benzenesulfonic acid 1, C 1, C 1, C — 1, C 1, PC Maleic acid — — — — — — Phosphoric acid 3, C 3, C 3, C — 3, C — (+)-L-Tartaric acid A A A — A 1, PC Fumaric acid 1, C 1, C 1*, C — ¼, C ¼, C Citric acid A A — — A A Succinic acid — U — — A — Benzoic acid — — — — — — Key A Amorphous # Pattern number C Crystalline potential salt PC Poorly crystalline U Counterion (unreacted) — No solids * Additional peaks
[0198] A summary of the properties of the hydrochloride, besylate and fumarate salts are reported in Table 3.6 below in addition to
TABLE-US-00011 TABLE 3.6 Summary of salt properties TGA/DSC Weight Loss/ Endothermic Exothermic HPLC wt % Events Events Solid (Temp/ (onset/peak)/ (onset/peak)/ Purity/ º C.) º C. º C. % area .sup.1H NMR Comments Hydrochloride Pattern 2.1 194/208 N/A 92.2 Ethanol 0.5 Anhydrous, high 1 (20-191) wt % potential melt, physically stable at 40° C./75% RH, solution degradation observed Besylate Pattern 1 1.1 138/149 N/A 91.5 Benzenesulfonic Anhydrous, (20-196) acid 1.3 equiv. physically stable Ethanol 0.37 at 40° C./75% RH, wt % solution degradation observed Phosphate Pattern 1 10.5 82/113 N/A 93.4 THF 2.3 wt % Likely solvate. (20-211) Physically unstable at 40° C./75% RH. Solution degradation observed. Phosphate Pattern 2 9.0 N/A N/A 92.7 Ethanol 1.6 Potential (20-201) wt % solvate/hydrate. Physically unstable at 40° C./75% RH Phosphate Pattern 3 1.7 103/113 167/171 N/A No residual Obtained from (20-119) 218/230 solvents exposure to 5.3 40° C./75% RH, (119-199) multiple weight 7.5 losses in TGA. (199- 300 Tartrate Pattern 1 2.3 126/141 N/A 91.7 Tartrate 1.1 Potentially hydrate (20-164) 171/192 equiv. or anhydrous. 35.9 No residual Deliquescence (164- solvents observed at 301) 40° C./75% RH. Solution degradation observed. Fumarate Pattern 1 4.3 143/153 N/A 90.4 Fumarate 1.5 Likely solvate. (20-168) equivalents Physically stable 31.2 THF 1.7 wt % at 40° C./75% RH, (168- from THF. 336) Fumarate Pattern 2 5.7 141/152 N/A 94.4 Fumarate 1.3 Likely solvate. (72-159) 200/205 equivalents Physically 31.1 Ethanol 2.9 unstable at (159- wt % 40° C./75% RH. 330) Solution degradation observed. Fumarate Pattern 3 2.9 139/147 N/A 96.9 Fumarate 1.4 Potentially (112-175) 186/207 equivalents anhydrous or 39.1 No residual hydrate. Physically (175- solvents unstable at 304) 40° C./75% RH. Fumarate Pattern 1/4 7.7 137/148 N/A 93.1 Fumarate 1.2 Obtained from (20-170) equivalents exposure to 30.6 No residual 40° C./75% RH. (170- solvents 303) Succinate Pattern 1 2.5 74/83 N/A 89.2 Succinate 1.9 Potentially (20-127) 152/161 equivalents anhydrous or 56.0 No residual hydrate. Low (127- solvents potential melt. 316) Physically unstable at 40° C./75% RH. Solution degradation observed.
[0199] As can be seen from the tables above no solids were isolated for the following counterions: sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, malic acid and benzoic acid. Additional experiments were performed on these counterions as described in the methodology section, however after temperature cycling and anti-solvent addition, no solids were observed.
[0200] The results from reactions with each acid where solids were formed are summarised in more detail below.
Hydrochloric Acid:
[0201] When hydrochloric acid was used, the following results and observations were obtained.
[0202] Solids of potential hydrochloride salt Pattern 1 were isolated from five solvent systems: THF, ethyl acetate, ethanol, MEK and acetonitrile. XRPD analysis indicated that hydrochloride salt Pattern 1 persisted after drying at 40° C. under vacuum and after storage at 40° C./75% RH as shown in
[0203] TG/DSC analysis of the solids of hydrochloride salt Pattern 1, isolated from ethyl acetate, showed a weight loss of 2.1 wt % between 20-191° C. One endothermic event was observed with an onset temperature of 194° C., and a peak temperature of 208° C. as shown in
[0204] The .sup.1H NMR spectrum of the solids of hydrochloride salt Pattern 1, isolated from ethanol, was consistent with the chemical structure of mesembrine, with an additional signal at 11.39 ppm, consistent with salt formation. The residual ethanol content was 0.5% wt as shown in
[0205] HPLC analysis on the dried solids from ethanol showed the chemical purity was 92.2% area (c.f.: the input purity was 91.2% area) as shown in
[0206] HPLC analysis on the filtered mother liquor from the experiment in ethyl acetate indicated the chemical purity was 40.3% area.
Benzenesulfonic Acid:
[0207] The results of the experiments with benzenesulfonic acid are summarized below.
[0208] Solids of potential besylate salt Pattern 1 were isolated from five solvent systems: THF, ethyl acetate, ethanol, MEK and acetonitrile. This XRPD pattern persisted after drying at 40° C. under vacuum, and after storage at 40° C./75% RH as shown in
[0209] TG/DSC analysis of dried solids of besylate salt Pattern 1, isolated from ethyl acetate, showed a weight loss of 1.1 wt % between 20-196° C. In the DSC thermogram, one endothermic event was observed with an onset temperature of 138° C., and a peak temperature of 149° C. as shown in
[0210] The .sup.1H NMR spectrum of solids of besylate salt Pattern 1, isolated from ethanol, was consistent with the structure of mesembrine, with an additional signal at 9.92 ppm, indicative with salt formation. Benzenesulfonic acid was also observed in the NMR spectrum, and the content was equal to 1.3 equivalents. A residual ethanol content of 0.37 wt % was observed as shown in
[0211] HPLC analysis of the dried solids from the experiment in MEK indicated a chemical purity of 91.46% area (c.f.: the input purity was 91.2% area) as shown in
[0212] HPLC analysis of the mother liquor from the experiment in ethyl acetate indicated a chemical purity of 44.21% area.
Phosphoric Acid:
[0213] The results of the experiments with phosphoric acid are summarized below.
[0214] Solids isolated from THF and MEK were poorly crystalline and labelled potential phosphate salt Pattern 1. After drying at 40° C. under vacuum solids of poorly crystalline phosphate Pattern 1 were maintained. After storage at 40° C./75% RH, the solids isolated from MEK had deliquesced but re-solidified out of the high humidity. For both materials, conversion to phosphate salt Pattern 3 was observed.
[0215] The solids isolated from the experiment in ethyl acetate were amorphous and remained amorphous after drying. After 24 h at 40° C./75% RH, conversion to phosphate Pattern 3 was observed.
[0216] The solids isolated from ethanol were poorly crystalline and labelled as potential phosphate salt Pattern 2. After drying at 40° C. under vacuum solids of poorly crystalline phosphate Pattern 2 were maintained, and after storage at 40° C./75% RH, conversion to phosphate salt Pattern 3 was observed.
[0217] HPLC analysis of the dried solids of phosphate salt Pattern 1, from THF, showed a chemical purity of 93.4% area. HPLC analysis of dried solids of phosphate salt Pattern 2, from ethanol, showed a chemical purity of 92.67% area.
[0218] The purity of the mother liquor from the experiment in MEK was 65.31% area.
[0219] TG/DSC analysis of solids of phosphate salt Pattern 1, from THF, showed a weight loss of 10.5 wt % between 20-211° C. In the DSC thermogram, one endothermic event was observed with an onset temperature of 82° C., and a peak temperature of 113° C.
[0220] The .sup.1H NMR spectrum of phosphate salt Pattern 1, isolated from THF, was consistent with the structure of mesembrine. A residual THF content of 2.3 wt % was observed. The 31P NMR analysis indicated a phosphate group was present in the material.
[0221] The TG/DSC analysis of solids of phosphate salt Pattern 2, from ethanol, showed a weight loss of 9.0 wt % between 20-201° C. In the DSC thermogram, no endothermic events were observed.
[0222] The .sup.1H NMR spectrum of phosphate salt Pattern 2, isolated from ethanol, was consistent with the structure of mesembrine. A residual ethanol content of 1.6 wt % was observed. The 31P NMR spectrum was consistent with the presence of a phosphate group within this material.
[0223] The TG/DSC analysis of solids of phosphate salt Pattern 3, obtained from THF after storage at 40° C./75% RH, showed a weight loss of 1.7 wt % between 20-119° C., followed by a second weight loss of 5.3 wt % between 119-199° C. a final weight loss of 7.5 wt % was observed between 199-300. In the DSC thermogram there was one endothermic event with an onset temperature of 103° C. and a peak temperature of 113° C. In the DSC thermogram there were also two exothermic events with onset temperatures of 167° C. and 218° C., and peak temperatures of 171° C. and 230° C.
[0224] The .sup.1H NMR spectrum of phosphate salt Pattern 3, isolated from MEK after storage at 40° C./75% RH was consistent with the structure of mesembrine. No residual solvent was detected. The 31P NMR spectrum indicated the presence of a phosphate group within the material.
(+)-L-Tartaric Acid:
[0225] The results of the experiments with (+)-L-tartaric acid are summarized below.
[0226] Solids of potential tartrate salt, Pattern 1, were isolated from ethanol and MEK, but were poorly crystalline, and from acetonitrile. After drying under vacuum, solids of tartrate salt Pattern 1 were maintained in solids from ethanol, MEK and acetonitrile. After exposing to 40 C/75% RH, the solids from ethanol and MEK had deliquesced and re-solidified on removal from the humidity chamber. These solids were amorphous. The solids from acetonitrile remained as tartrate salt Pattern 1, but with a decrease in crystallinity.
[0227] Solids of tartrate salt Pattern 1 were also observed in the solids isolated from THF, after drying at 40° C. under vacuum.
[0228] The solids of tartrate salt Pattern 1, isolated from THF, had a chemical purity of 91.70% area (c.f.: the input purity was 91.2% area) by HPLC.
[0229] The mother liquor for the experiment in acetonitrile had a chemical purity of 34.80% area.
[0230] TG/DSC analysis of solids of tartrate salt Pattern 1, from ethanol, showed a weight loss of 2.3 wt % between 20-164° C., followed by a second weight loss of 35.9 wt % between 164-301° C. Two endothermic events were observed in the DSC thermogram with onset temperatures of 126° C. and 171° C., and peak temperatures of 141° C. and 192° C.
[0231] The 1H NMR spectrum of solids of tartrate salt Pattern 1, isolated from acetonitrile, was consistent with the structure of mesembrine. Tartaric acid was observed, with a content equal to 1.1 equivalents. No residual acetonitrile was observed.
Fumaric Acid:
[0232] The results of the experiments with fumaric acid are summarized below.
[0233] Solids isolated from THF were poorly crystalline and labelled potential fumarate salt Pattern 1. After drying at 40° C. under vacuum this poorly crystalline Pattern 1 material persisted. After storage at 40° C./75% RH, an increase in crystallinity was observed, and the material remained Pattern 1.
[0234] Solids isolated from ethyl acetate were crystalline and labelled as potential fumarate salt Pattern 2. After drying at 40° C. under vacuum a mixture of fumarate Pattern 1 and Pattern 2 was observed by XRPD. After storage at 40° C./75% RH, conversion to fumarate salt Pattern 1 was observed.
[0235] Solids of fumarate salt Pattern 2 were also observed from ethanol, which persisted after drying. After exposure to 40° C./75% RH conversion to fumarate salt Pattern 1, with additional peaks, was observed.
[0236] Solids of poorly crystalline fumarate salt Pattern 1 were observed from MEK, and were maintained after drying at 40° C. under vacuum. Exposure to 40° C./75% RH resulted in conversion to a mixture of fumarate salt Pattern 1 and Pattern 4.
[0237] Solids isolated from acetonitrile were crystalline, and labelled as fumarate salt Pattern 3, and persisted after drying at 40° C. under vacuum. Exposure to 40° C./75% RH resulted in conversion to a mixture of fumarate salt Pattern 1 and Pattern 4.
[0238] XRPD of the salt Patterns 1, 2 and 3 are shown in
[0239] TG/DSC analysis showed the solids of fumarate salt Pattern 1, isolated from THF, showed a weight loss of 4.3 wt % between 20-168° C., followed by a second weight loss of 31.2 wt % between 168-336° C. One endothermic event was observed in the DSC thermogram with an onset temperature of 143° C. and a peak temperature of 153° C.
[0240] The .sup.1H NMR spectrum of fumarate salt Pattern 1, isolated from THF, was consistent with the structure of mesembrine. The fumaric acid content was equal to 1.5 equivalents (30.7 wt %). The residual THF content was 1.7 wt %.
[0241] TG/DSC analysis showed the solids of fumarate salt Pattern 2, isolated from ethanol, showed a weight loss of 5.7 wt % between 72-159° C., and a second weight loss of 31.1 wt % between 159-330° C. There were two endothermic events in the DSC thermogram with onset temperatures of 141° C., and 200° C., and peak temperatures of 152° C. and 205° C.
[0242] The .sup.1H NMR spectrum of fumarate salt Pattern 2, isolated from ethanol, was consistent with the structure of mesembrine. The fumaric acid content was equal to 1.3 equivalents (27.6 wt %). The residual ethanol content was 2.9 wt %.
[0243] TG/DSC analysis of solids of fumarate salt Pattern 3, isolated from acetonitrile, showed a weight loss of 2.9 wt % between 112-175° C., followed by a second weight loss of 39.1 wt % between 175-304° C. Two endothermic events were observed with onset temperatures of 139° C. and 186° C., and peak temperatures of 147° C. and 207° C.
[0244] The .sup.1H NMR spectrum of fumarate salt Pattern 3, isolated from acetonitrile, was consistent with the structure of mesembrine. The fumaric acid content was equal to 1.4 equivalents. No residual acetonitrile was observed.
[0245] The TG/DSC analysis of solids of a mixture of fumarate salt Pattern 1 and Pattern 4, isolated from acetonitrile after storage at 40° C./75% RH, showed a weight loss of 7.7 wt % between 20-170° C., and a second weight loss of 30.6 wt % between 170-303° C. In the DSC thermogram, one endothermic event was observed with an onset temperature of 137° C. and a peak temperature of 148° C.
[0246] The .sup.1H NMR spectrum of a mixture of fumarate salt Pattern 1+Pattern 4, isolated from MEK after exposure to 40° C./75% RH, was consistent with the chemical structure of mesembrine. The fumaric acid content was equal to 1.2 equivalents. No residual MEK was observed.
[0247] The TG/DSC for salt Patterns 1-3 are shown in
[0248] HPLC analysis showed a chemical purity of 90.36% area for the solids of fumarate salt Pattern 1, isolated from THF. The solids of fumarate salt Pattern 2, isolated from ethanol, had a chemical purity of 94.35% area. The solids of fumarate salt Pattern 3, isolated from acetonitrile, had a chemical purity of 96.47% area. The solids of a mixture of fumarate salt Pattern 1 and Pattern 4, isolated from MEK after exposure to 40° C./75% RH, was 93.1% area c.f.: the input purity was 91.2% area) as shown in
Succinic Acid:
[0249] The results of the experiments with succinic acid are summarized below.
[0250] The solids isolated from MEK were crystalline and labelled potential succinate salt Pattern 1. This pattern persisted after drying at 40° C. under vacuum, however after exposure to 40° C./75% RH, conversion to amorphous material was observed.
[0251] Solids of potential succinate salt Pattern 1 had a chemical purity of 89.2% area.
[0252] The TG/DSC analysis of potential succinate salt Pattern 1 showed a weight loss of 2.5 wt % between 20-127° C., followed by a second weight loss of 56.0 wt % between 127-316° C. In the DSC thermogram, two endothermic events were observed with onset (and peak) temperatures of 74° C. (83° C.), and 152° C. (161° C.).
[0253] The .sup.1H NMR analysis of potential succinate salt Pattern 1 was consistent with the chemical structure of mesembrine. A succinic acid content of 35.9 wt % (1.9 equivalents) was observed. No residual solvents were detected.
Conclusion
[0254] The data detailed above demonstrates that the salts formed using the counterions hydrochloric acid, benzenesulfonic acid and fumaric acid were crystalline, anhydrous solids with high potential melt temperatures and able to demonstrate physical stability.
[0255] As such these counterions were selected for a secondary salt formation assessment.
[0256] Table 3.1 details the pKa of the various counterions tested in the salt formation assessment. It is generally accepted that a difference of at least 2 pKa units between the acid and base are required for proton transfer, and as such the stronger the acid (lower pKa) the more likely a salt is to form. It was therefore surprising that apart from hydrochloric acid the stronger acids such as sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid were unable to form salts with mesembrine.
Example 4: Secondary Salt Formation Assessment
Materials and Methods
Hydrochloride Salt Pattern 1:
[0257] The following procedure was used for the scale-up of the Hydrochloride salt Pattern 1. Approximately 0.5 g of mesembrine was dissolved in 2.5 mL of ethanol. 1.1 equivalents of HCl (0.156 mL) were dissolved in 2.5 mL of ethanol, and added to the solution of mesembrine, at 25° C. (Initial concentration: 100 mg/mL).
[0258] The experiment was stirred for ca. 1 h, then cooled to 5° C. at 0.1° C./min. After ca. 18 h at 5° C., 200 μL was sub-sampled and centrifuged and the solids analysed by XRPD.
[0259] The solids were predominately amorphous, so the experiment was heated to 25° C. over 10 minutes, and 15 mL of heptane was added over 30 minutes. The experiment was then cooled to 5° C. at 0.1° C./minute and held at 5° C. After ca. 2 h at 5° C., 200 μL was sub-sampled and centrifuged and the solids analysed by XRPD. The mother liquor was biphasic.
[0260] The solids were poorly crystalline, so the experiment was temperature cycled between 25° C. and 5° C. at 0.1° C./min, with 1 h holds at 25° C. and 5° C., for ca. 18 h. At 5° C., the solids were isolated by Buchner filtration and analysed by XRPD. The solids were dried at 40° C. under vacuum for ca. 72 h and then further characterization carried out.
Besylate Salt Pattern 1:
[0261] The following procedure was used for the scale-up of the Besylate salt Pattern 1.
[0262] Approximately 0.5 g of mesembrine was dissolved in 2.5 mL of MEK. 1.1 equivalents of benzenesulfonic acid (306.78 mg) were dissolved in 2.5 mL of MEK, and added to the solution of mesembrine, at 25° C. (Concentration: 100 mg/mL).
[0263] The experiment was stirred for ca. 1.5 h. The experiment was then cooled to 5° C. at 0.1° C./minute and held at 5° C. for ca. 18 h. A sub-sample (200 μL) was taken and centrifuged, and the solids analysed by XRPD.
[0264] The solids were isolated by Buchner filtration and dried at 40° C. under vacuum for ca. 18 h before being characterized further.
Fumarate Salt Pattern 1+Pattern 4 (Mixture):
[0265] The following procedure was used for the scale-up of the fumarate salt Pattern 4.
[0266] Approximately 0.5 g of mesembrine was dissolved in 2.5 mL of MEK. 1.1 equivalents of fumaric acid (222 mg) were dissolved in 2.5 mL of MEK, and the solution of mesembrine was added to the fumaric acid, dropwise at 25° C. (Concentration: 100 mg/mL).
[0267] The experiment was stirred for ca. 1 h at 25° C. The experiment was then cooled to 5° C. at 0.1° C./min and held at 5° C. for ca. 18 h. A sub-sample (200 μL) was taken and centrifuged, and the solids analysed by XRPD.
[0268] The slurry was very thick, therefore an additional 2 mL of MEK was added to improve slurry mobility, and stirred for ca. 30 min. The solids were isolated by Buchner filtration and dried at 40° C. under vacuum for ca. 18 h. The solids were analysed by XRPD, and then transferred to 40° C./75% RH.
[0269] After 5 days at 40° C./75% RH the solids were removed and further characterized.
[0270] The solids were sub-sampled after 1, 2 and 5 days for XRPD analysis.
Re-Preparation of Fumarate Salt Pattern 4:
[0271] The following general procedure was used for the re-preparation of the fumarate salt Pattern 4.
[0272] Approximately 103 mg of mesembrine was weighed into a vial and dissolved 0.52 mL of MEK at 25° C. 1.1 equivalents of fumaric acid was suspended in 0.52 mL of MEK. The mesembrine solutions were added to the fumaric acid at 25° C. and stirred.
[0273] The experiments were stirred for 1.5 h at 25° C. and then was cooled to 5° C. and 0.1° C./min and held at 5° C. for ca. 18 h before isolation. The solids were isolated by centrifugation. Solids were isolated and dried at 40° C. under vacuum for ca. 24 h.
Results
Hydrochloride Salt Pattern 1:
[0274] Solids of hydrochloride salt Pattern 1 were isolated in a 48% yield, with a chemical purity of 90.5% area. KF indicated a water content of 0.4% w/w. CAD indicated a chloride content of 0.9 equivalents, indicating the material is a mono-hydrochloride salt.
[0275] The solids were faint beige (BE10) with respect to the Sigma Aldrich colour chart.
[0276] TG/DSC analysis showed a weight loss of 1.7 wt % between 20-160° C., followed by a weight loss of 21.7 wt % between 162-273° C. An endothermic event with an onset temperature of 188° C. and a peak temperature of 200° C. was observed.
[0277] DSC analysis showed an endothermic event with an onset temperature of 182° C. and a peak temperature of 197° C.
[0278] VT-XRPD analysis showed that solids of hydrochloride salt Pattern 1 persisted between 25-160° C. At 188 and above (to 205° C.), the material was amorphous, and remained amorphous after cooling. The solids appeared to have melted.
[0279] Polarized light microscopy (PLM) showed the material had no distinct morphology, with no apparent birefringence, see
[0280] An IR spectrum was recorded for reference.
[0281] The .sup.1H NMR spectrum was consistent with the formation of a salt of mesembrine. A residual ethanol content of 0.98 wt %, and a residual heptane content of 0.64 wt % was observed.
[0282] DVS analysis showed a water uptake of 5.4 wt % at 80% RH, and 25° C., indicating the material was hygroscopic. At 90% RH, the water uptake was 20.3 wt % indicating significant hygroscopicity above 80% RH. Solids of hydrochloride salt Pattern 1 were recovered from the DVS analysis.
[0283] VH-XRPD analysis showed that even after 12 h at 90% RH, the solids remained consistent with hydrochloride salt Pattern 1. No change in crystallinity was observed.
Besylate Salt Pattern 1:
[0284] Solids of besylate salt Pattern 1 were isolated in a 69% yield, with a chemical purity of 98.1% area. KF indicated a water content of 0.3% w/w.
[0285] The solids were faint beige (BE10) with respect to the Sigma Aldrich colour chart.
[0286] TG/DSC analysis showed a weight loss of 0.3 wt % prior to decomposition. In the DSC thermogram two endothermic events were observed with onset (and peak) temperatures of 131° C. (141° C.) and 151° C. (158° C.).
[0287] In the DSC, at a heating rate of 10° C./min, two overlapping endothermic events were observed in the first heat with onset (and peak) temperatures of 132° C. (141° C.) and 150° C. (158° C.). In the first cool a vitrification was observed with a mid-point half-height of 59° C., in the second heat a glass transition was observed with a mid-point half-height of 65° C. The DSC was repeated with a heating rate of 1° C./min which successfully resolved the endothermic events in the first heat, which were observed to have onset (and peak) temperatures of 129° C. (135° C.), and 151° C. (156° C.).
[0288] VT-XRPD analysis showed that solids of besylate salt Pattern 1 persisted between 25-150° C. At temperatures of 157° C. to 160° C., and after returning to 25° C., the material was amorphous, and appeared to have melted.
[0289] PLM indicated the material had no distinct morphology, with some birefringence, see
[0290] An IR spectrum was recorded for reference.
[0291] The .sup.1H NMR spectrum was consistent with the formation of a salt of mesembrine. The benzenesulfonic acid content was 1.1 equivalents, indicating the material is a mono-besylate salt.
[0292] DVS analysis showed that besylate salt Pattern 1 had a water uptake of 2.3 wt % at 80% RH and 25° C., indicating the material was hygroscopic. At 90% RH, the water uptake was 13 wt %, indicating significant hygroscopicity above 80% RH. Solids isolated at the end of the DVS analysis were consistent with besylate salt Pattern 1.
[0293] VH-XRPD analysis showed that even after 17 h at 90% RH, solids of besylate salt Pattern 1 persisted. There was no change in crystallinity during this analysis.
Fumarate Salt Pattern 1+Pattern 4 (Mixture):
[0294] Solids of a mixture of fumarate salt Pattern 1 and Pattern 4 were isolated in a 55% yield, with a chemical purity of 96.6% area. KF analysis indicated a water content of 4.0% w/w (ca. 1 equivalent water).
[0295] The solids were faint beige (BE10) with respect to the Sigma Aldrich colour chart.
[0296] TG/DSC analysis showed a weight loss of 3.4 wt % between 20-95° C., followed by second weight loss of 1.8 wt % between 95° C. and 162° C. In the DSC thermogram, two endothermic events were observed with onset (and peak) temperatures of 67° C. (80° C.), and 131° C. (154° C.).
[0297] In the DSC thermogram, two endothermic events were observed with onset (and peak) temperatures of 61° C. (75° C.), and 136° C. (152° C.).
[0298] VT-XRPD showed that between 25° C. and 90° C. a mixture of fumarate salt Pattern 1 and Pattern 4 persisted. At 130° C., the diffractogram was consistent with fumarate Pattern 4. At 154° C. and to 170° C., and after returning to ambient temperature the material was amorphous.
[0299] PLM showed the material had no distinct morphology, with limited birefringence, see
[0300] An IR spectrum was recorded for reference.
[0301] The .sup.1H NMR spectrum was consistent with the salt formation of mesembrine. The fumaric acid content was equal to 1.3 equivalents, indicating this material is a mono-fumarate salt. A residual MEK content of 0.74 wt % was observed.
[0302] DVS analysis showed that at 80% RH and 25° C., the water uptake was 0.7 wt %, indicating that the material is slightly hygroscopic. Between 0-20% RH, a water uptake of 2.1 wt % was observed, indicating that at ambient humidity's the material is likely hydrated. The solids isolated at the end of the analysis were consistent with a mixture of fumarate salt Pattern 1 and Pattern 4.
[0303] VH-XRPD showed that between 40% RH and 10% RH, the solids were consistent with a mixture of fumarate salt Pattern 1 and Pattern 4. At 0% RH, a new diffractogram was observed, labelled fumarate Pattern 5.
Re-Preparation of Fumarate Salt Pattern 4:
[0304] XRPD showed Pattern 4 without Pattern 1 present. DVS analysis on fumarate salt Pattern 4 showed a water uptake of 0.5 wt % at 80% RH, 25° C., indicating the material was slightly hygroscopic. HPLC indicated the chemical purity was 95.88% area.
Conclusion
[0305] Salts were successfully formed from all three counterions and analysed accordingly. The three salts demonstrated properties consistent with improved attributes consistent with the ability to produce enhanced pharmaceutical formulations.
Example 5: Salt Hydration Study
Materials and Methods
[0306] Approximately 20 mg of the hydrochloride (HCl), besylate and fumarate salts were weighed into 3×2 mL push cap vials. 0.05-0.1 mL of relevant solvent system was added to each vial, at 25° C.
[0307] Methanol/water solvent systems (99:1, 75:25, 33:67) of known water activity (a.sub.w 0.2, 0.5 and 0.8 respectively) were used. The experiment was stirred for ca. 24 h. After 24 h, any slurries were centrifuged, and the solids analysed by XRPD.
[0308] An additional hydration study was required in order to repeat the salt hydration studies, for the HCl salt and the besylate salt due to dissolution in the first set of experiments:
[0309] For each salt, approximately 10 mg was weighed into 4×2 mL vials and a stirrer bar added. 10 μL of each solvent system was added, at 25° C. The experiments were stirred for 24 h, and any solids recovered were then analysed by XRPD.
Results
[0310] The results of the hydration studies are summarized in Table 3.7 below.
[0311] Clear solutions were obtained for the experiments with hydrochloride salt Pattern 1, and besylate salt Pattern 1.
[0312] Additional experiments with hydrochloride salt Pattern 1 resulted in slurries persisting at a.sub.w 0.5 and 0.8. The isolated solids were consistent with hydrochloride salt Pattern 1.
[0313] Clear solutions were obtained from the additional experiments with besylate salt Pattern 1, indicating the solubility was >1000 mg/mL.
[0314] Slurries were maintained for the fumarate salt. The isolated solids were consistent with fumarate salt Pattern 4.
TABLE-US-00012 TABLE 3.7 Summary of Results from Hydration Studies Salt Concentration/mg/mL Water Activity/a.sub.w Observation XRPD Hydrochloride 200 0.2 Clear solution — Pattern 1 1000 — 200 0.5 Clear solution — 1000 Slurry 1, C 200 0.8 Clear solution 1000 Slurry 1, C Besylate 200 0.2 Clear solution — Pattern 1 1000 400 0.5 Clear solution — 1000 400 0.8 Clear solution — 1000 Fumarate 400 0.2 Thick slurry 4, C Pattern 1 + 4 400 0.5 Slurry 4, C 200 0.8 Thick slurry 4, C Key A Amorphous # Pattern number C Crystalline potential salt PC Poorly crystalline U Counterion (unreacted) — No solids
Conclusion
[0315] The besylate salt was highly soluble resulting in greater than 1000 mg/ml at all levels of water activity, providing evidence that this salt is highly suitable for development of a pharmaceutical composition.
[0316] The hydrochloride salt was not soluble at higher concentrations and higher water activity levels. The fumarate did not produce a clear solution at any of the concentrations or water activity levels tested.
Example 6: PH Solubility Study
[0317] Materials and Methods
[0318] Approximately 20 mg of each salt was weighed into 3×2 mL push cap vials. 0.1 mL of buffer (Chloride pH 1.2; Acetate pH 4.5; Phosphate pH 6.8) was added to each vial, at 25° C. The experiment was stirred for ca. 24 h. After 2 h, the pH was measured and adjusted if required. After 24 h a final pH measurement was taken. Any slurries were centrifuged and the solids analysed by XRPD. The clear solutions/mother liquors were analysed by HPLC
Results
[0319] The results from the pH solubility study are summarized in Table 3.8:
[0320] High solubility (>96.75 mg/mL, with respect to mesembrine) was observed for hydrochloride salt Pattern 1 and besylate Pattern 1 across all pH ranges (1.2, 4.5, 6.8).
[0321] Solubility was 29.44 mg/mL for fumarate salt Pattern 1, at pH 1.2. Solids isolated from this experiment were consistent with fumaric acid.
[0322] Oiling was observed in the fumarate salt Pattern 1 experiment at pH 6.8.
TABLE-US-00013 TABLE 3.8 Summary of Results from pH Studies pH HPLC Target 2 h 2 h 24 h Final Purity/ Conc./ Salt PH measured adjusted measured pH Observation % area mg/mL XRPD Hydrochloride 1.2 1.2 1.25 n/a 1.48 Clear solution 97.09 >105 — Pattern 1 4.5 4.5 4.49 n/a 4.34 Clear solution 93.45 >146 — 6.8 6.8 5.67 6.74 6.54 Clear solution 92.87 >122 — Besylate 1.2 1.2 1.18 n/a 1.18 Clear solution 98.01 >172 — Pattern 1 4.5 4.5 5.55 4.55 3.72 Clear solution 98.02 >140 — 6.8 6.8 5.53 6.75 6.80 Clear solution 97.62 >97 — Fumarate 1.2 1.2 2.31 1.21 1.36 Slurry 96.31 29.44 U Pattern 1 + 4 4.5 4.5 3.28 4.49 4.53 Clear solution 96.07 >24 — 6.8 6.8 3.38 6.71 8.01 Oil 96.78 18.98 — Key A Amorphous # Pattern number C Crystalline potential salt PC Poorly crystalline U Counterion (unreacted) — No solids
Conclusion
[0323] The besylate salt and hydrochloride salts were highly soluble at all pH ranges, providing evidence that these salts would be suitable for development of a pharmaceutical composition.
[0324] The fumarate salt was only able to produce a clear solution at pH 4.5.
Example 7: Stability Study
Materials and Methods
[0325] A 1-week stability study was performed for hydrochloride salt Pattern 1, besylate salt Pattern 1, fumarate salt Pattern 1+4, and fumarate salt Pattern 4.
[0326] Approximately 5 mg of the salt was weighed into 3×2 mL push cap vials. The 2 mL vials were then each placed inside a 20 mL vial, with the lids on or off as required. The solids were placed under the required stability conditions for 1 week at the following three conditions: 40° C./75% RH (open); 80° C. (closed); Ambient light, temperature and humidity (open)
[0327] After 1-week, visual observations were noted, then the solids were analysed by XRPD and HPLC.
Results
[0328] The results from the 1-week stability studies are summarized in Table 3.9.
[0329] For hydrochloride salt Pattern 1, there was a slight increase in chemical purity observed from all stability conditions. Solids of hydrochloride salt Pattern 1 were isolated from all stability conditions.
[0330] For besylate salt Pattern 1, there was no decrease in chemical purity observed after 1 week at 40° C. /75% RH, or ambient conditions. A small decrease in chemical purity was observed after 1 week at 80° C. Solids of besylate salt Pattern 1 were isolated from all conditions.
[0331] For fumarate salt Pattern 1+4, there was a slight decrease in chemical purity observed after 1 week at 40° C./75% RH, and the solids were consistent with a mixture of fumarate salt Pattern 1 and Pattern 4. A decrease in chemical purity was observed after 1 week at 80° C., with conversion to novel fumarate salt Pattern 6. No significant decrease in chemical purity was observed after 1 week at ambient conditions, and the solids had a XRPD diffractogram consistent with a mixture of fumarate salt Pattern 1 and Pattern 4.
[0332] For fumarate salt Pattern 4, solids of fumarate salt Pattern 4 were recovered from all stability conditions. There was a slight increase in chemical purity after 1-week at all stability conditions.
TABLE-US-00014 TABLE 3.9 Summary of Results from 1-week stability study Stability HPLC/ Salt Condition Observation * % area XRPD Hydrochloride Input Faint beige solids (BE10) 90.5 1, C Pattern 1 40° C./75% RH (open) Light brown solids (BR8) 93.4 1, C 80° C. (closed) Light brown solids (BR8) 92.8 1, C Ambient light, temperature Faint beige solids (BE10) 91.5 1, C and humidity Besylate Input Faint beige solids (BE10) 98.1 1, C Pattern 1 40° C./75% RH (open) Light brown solids (BR8) 98.0 1, C 80° C. (closed) Faint beige solids (BE10) 96.7 1, C Ambient light, temperature Faint beige solids (BE10) 98.1 1, C and humidity Fumarate Input Faint beige solids (BE10) 96.6 1/4, C Pattern 1 + 4 40° C./75% RH (open) Faint beige solids (BE10 95.6 1/4, C 80° C. (closed) Light brown solids (BR8) 83.4 6, C Ambient light, temperature Faint beige solids (BE10 96.1 1/4, C and humidity Fumarate Input Faint beige solids (BE10) 95.9 4, C Pattern 4 40° C./75% RH (open) Faint beige solids (BE10) 96.4 4, C 80° C. (closed) Faint beige solids (BE10) 96.4 4, C Ambient light, temperature Faint beige solids (BE10) 96.4 4, C and humidity Key A Amorphous # Pattern number C Crystalline potential salt PC Poorly crystalline U Counterion (unreacted) — No solids * From the Sigma Aldrich colour chart
Conclusion
[0333] The besylate, hydrochloride and fumarate salt Pattern 4 were stable across all storage conditions, providing evidence that these salts would be suitable for development of a pharmaceutical composition.
[0334] The fumarate salt pattern 1 and 4 produced a novel salt type on storage at 80° C. was only able to produce a clear solution at pH 4.5.
Example 8: Scale-Up of Besylate Salt Pattern 1
Materials and Methods
[0335] A scale-up of the Besylate salt Pattern 1 was undertaken in order to fully characterise the salt of this form and to undertake a polymorph screen. An anti-solvent addition step was carried out to maximise the yield:
[0336] Approximately 4.5 g of mesembrine was weighed out and dissolved in 27.7 mL of MEK, and transferred to a 100 mL vessel at 25° C. Next 1.1 equivalents (2.79 g) of benzenesulfonic acid was weighed out and dissolved in 17.7 mL of MEK.
[0337] The stock solution of benzenesulfonic acid was added dropwise into the vessel, and the experiment stirred for 1 h at 25° C.
[0338] The experiment was cooled to 5° C. at 0.1° C./min. At 5° C., 15 mL of heptane was added over 3.3 h. The final solvent system was: MEK:heptane 75:25% v/v.
[0339] The experiment was then stirred at 5° C. for ca. 12 h. Crusting was observed on the walls of the vessel, and this was manually re-introduced into the slurry.
[0340] The solids were isolated by Buchner filtration and washed with 5 mL of MEK:heptane 75:25% v/v.
[0341] Prior to isolation, a sub-sample of solids was taken by centrifugation for XRPD analysis. The solids were dried at 40° C. under vacuum for ca. 29 h and used for further analysis and polymorph screening.
[0342] The besylate salt was then lyophilised to prepare amorphous material using the following procedure.
[0343] Approximately 50 mg of besylate salt Pattern 1 was weighed into a 2 mL push cap vial. The solids were dissolved in 0.5 mL of water, and then frozen at −20° C. Once frozen, the material was lyophilized. The isolated solids were then analysed by XRPD, TGA/DSC and HPLC.
Results
[0344] An XRPD of the solids from the scale-up experiment was prepared as detailed in
TABLE-US-00015 TABLE 3.10 XRPD Peaks for Besylate Salt Pattern 1 Pos. Height FWHM d-spacing Rel. [° 2θ ] [cts] Left [° 2θ] [Å] Int. [%] 9.2289 699.40 0.0895 9.58280 43.47 11.0523 643.46 0.0512 8.00559 39.99 11.1405 761.35 0.0768 7.94241 47.32 12.2729 481.42 0.0895 7.21196 29.92 12.7303 1215.72 0.1023 6.95387 75.56 13.4672 684.26 0.1151 6.57500 42.53 15.4051 286.37 0.1023 5.75196 17.80 16.6247 950.78 0.1023 5.33263 59.09 18.5019 121.96 0.1023 4.79562 7.58 19.5198 651.77 0.1151 4.54778 40.51 19.7897 242.77 0.0768 4.48634 15.09 20.2578 240.37 0.1023 4.38373 14.94 20.6618 756.89 0.1023 4.29892 47.04 21.1937 670.33 0.1407 4.19221 41.66 21.5953 542.41 0.1023 4.11516 33.71 22.3994 126.07 0.1535 3.96921 7.84 22.8769 212.17 0.0768 3.88744 13.19 23.2193 390.41 0.0640 3.83088 24.26 23.7753 881.90 0.1279 3.74253 54.81 24.1351 372.81 0.0768 3.68755 23.17 24.6446 1608.97 0.1279 3.61245 100.00 25.6285 243.78 0.1151 3.47596 15.15 26.1758 202.33 0.1279 3.40451 12.58 27.9112 140.83 0.1279 3.19666 8.75 28.3172 287.92 0.0895 3.15174 17.89 28.6091 117.85 0.1535 3.12024 7.32 29.2966 84.22 0.1791 3.04857 5.23 31.1585 113.96 0.1535 2.87052 7.08 32.4190 24.17 0.2047 2.76173 1.50 32.9906 98.16 0.1023 2.71517 6.10 33.8751 115.38 0.1279 2.64627 7.17
[0345] The solids were isolated with an 80% yield. The isolated solids had a chemical purity of 96.4% area, by HPLC.
[0346] The theoretical yield, based on losses to mother liquor and wash liquors, was 99%. The mother liquor and wash liquor concentrations were 0.3 mg/mL.
[0347]
Conclusion
[0348] The mesembrine besylate salt Pattern 1 was fully characterised by the XRPD analysis demonstrating a novel form of mesembrine salt with superior properties which are able to be lyophilised to produce an amorphous material suitable for use in the preparation of pharmaceutical compositions.
Example 9: Solubility Screen for Mesembrine Besylate Salt
Materials and Methods
[0349] The amorphous besylate salt prepared in Example 8 was used in a solubility screen as follows:
[0350] Known volume aliquots of solvent system were added to each vial, with heating at 40° C. between each addition for ca. 5 minutes. Addition of solvents was continued until either dissolution was observed, or until 100 volumes (ca. 1 mL) had been added.
[0351] After the solvent addition was complete, the experiments were stirred at 40° C. for ca. 16 h. Slurries were stirred at 40° C. and clear solutions were left to evaporate at 40° C., at ambient pressure for ca. 24 h. The solids were isolated by centrifuge filtration and were analysed by XRPD.
[0352] Clear solutions were left to evaporate at 40° C. under vacuum, for ca. 72 h. Any solids isolated were analysed by XRPD.
Results
[0353] The results of the solubility screen are summarized in Table 3.11 below.
TABLE-US-00016 TABLE 3.11 Solubility screen of amorphous besylate salt No. Solvent System/% v/v Solubility/mg/mL XRPD 1 1,4-Dioxane <10 A 2 1-Butanol <10 A 3 1-Propanol ca.31 1, C 4 2-Ethoxyethanol ca.44 1, PC 5 2-Methyl THF <10 1, C 6 2-Propanol <10 1, C 7 2-Propanol:Water (50:50) >500 n/a 8 2-Propanol:Water (75:25) ca.167 n/a 9 Acetone <10 1, C 10 Acetone:Water (90:10) >500 1, PC 11 Acetonitrile >500 A 12 Anisole <10 A 13 Butyl Acetate <10 A 14 Dichloromethane (DCM) ca.250 n/a 15 Diisopropyl ether <10 n/a 16 Dimethylsulfoxide (DMSO) >500 n/a 17 Ethanol ca.44 1, C 18 Ethanol:Water (50:50) >500 n/a 19 Ethanol:Water (90:10) >500 1, PC 20 Ethyl Acetate <10 1, C 21 Heptane <10 n/a 22 Isopropyl Acetate <10 1, PC 23 Methanol >500 n/a 24 Methylethyl Ketone (MEK) <10 1, PC 25 Methylisobutyl Ketone (MiBK) <10 A 26 N,N-Dimethylacetamide (DMA) >500 2, C 27 N,N-Dimethylformamide (DMF) ca.250 1, C 28 N-Methylpyrrolidone (NMP) >500 n/a 29 tert-Butylmethyl Ether (tBME) <10 n/a 30 Tetrahydrofuran (THF) <10 A 31 Toluene <10 A 32 Water >500 n/a Key A Amorphous 1 Besylate salt Pattern 1 C Crystalline salt 2 Besylate salt Pattern 2 PC Poorly crystalline
[0354] The solubility screen demonstrated that in addition to the besylate salt pattern 1 an additional salt pattern 2 was formed in DMA.
Conclusion
[0355] The amorphous material is soluble in many solvent systems and is capable of forming an additional polymorph described as besylate salt pattern 2.
Example 10: Polymorph Screen for Mesembrine Besylate Salt
Materials and Methods
[0356] The amorphous besylate salt prepared in Example 8 was used as the input for this set of experiments.
[0357] Approximately 1.25 g of besylate salt was weighed and dissolved in 17.5 mL of water. The solution was split across 25×2 mL vials and frozen. The frozen material was lyophilized for ca. 24 h. The isolated solids were dried at 20° C. under vacuum for ca. 24 h. The dried solids were analysed by XRPD.
[0358] Solvent was added to each vial to obtain a slurry. If dissolution was observed more amorphous material was added to try and produce a slurry.
[0359] The experiments were temperature cycled between 30° C. and 5° C. at 0.1° C./min with 1 h holds at 30° C. and 5° C., for 48 h. After 48 h, solids were isolated from slurries at 30° C. by centrifuge filtration and analysed by XRPD. The solids were then dried at 40° C. under vacuum for 18 h. The clear solutions were cooled to 5° C. over 10 minutes and held for 30 minutes to attempt to induce precipitation.
Results
[0360] The results of the solubility screen are summarized in Table 3.12 below.
TABLE-US-00017 TABLE 3.12 Polymorph screen of amorphous besylate salt Observation at XRPD No. Solvent System/% v/v end of experiment (damp) 1 1,4-Dioxane Slurry 1, C 2 1-Butanol Clear solution — 3 1-Propanol Slurry 2, C 4 2-Ethoxyethanol Slurry 2, C 5 2-Methyl THF Slurry 1 + 2, C 6 2-Propanol Slurry 2, C 7 2-Propanol:Water (75:25) Clear solution — 8 Acetone Slurry 1 + 2, C 9 Acetonitrile:Ethyl acetate (50:50) Slurry 2, C 10 Anisole Slurry 1 + 2, C 11 Dichloromethane (DCM) Slurry 2, C 12 DCM:tBME (50:50) Slurry 2, C 13 DMSO:Ethyl acetate (50:40) Clear solution — 14 Ethanol Clear solution — 15 Ethanol:Water (95:5) Slurry 2, C 16 Ethyl acetate Slurry 1, C 17 Isopropyl Acetate Slurry 1 + 2, C 18 Methanol:Ethyl acetate (50:50) Clear solution — 19 Methylethyl Ketone (MEK) Slurry 1, C 20 Methylisobutyl Ketone (MiBK) Slurry 1 + 2, C 21 NMP:tBME (50:50) Slurry 2, C 22 Tetrahydrofuran (THF) Slurry 1, C 23 Toluene Solids on vial base 2, C 24 Water Clear solution — Key — No solids 1 Besylate salt Pattern 1 C Crystalline salt 2 Besylate salt Pattern 2
[0361] As shown, many of the solvent systems were able to produce either of the polymorphs besylate salt pattern 1 or besylate salt pattern 2. Furthermore, some systems produced a mixture of both salt patterns.
[0362] The novel polymorph besylate salt pattern 2 was further characterised by XRPD as shown in
TABLE-US-00018 TABLE 3.13 XRPD Peaks for Besylate Salt Pattern 2 Pos. Height FWHM d-spacing Rel. [° 2θ] [cts] Left [° 2θ] [Å] Int. [%] 3.2456 58.55 0.6140 27.22259 1.10 7.4271 684.03 0.0768 11.90295 12.88 9.3019 1717.10 0.0895 9.50775 32.34 10.9620 2816.81 0.0895 8.07130 53.06 11.5879 1065.97 0.0768 7.63675 20.08 12.0804 494.59 0.0640 7.32648 9.32 12.5619 1305.28 0.0768 7.04670 24.59 13.4046 5309.08 0.0895 6.60552 100.00 14.5243 135.29 0.1023 6.09873 2.55 15.1300 2692.72 0.1023 5.85592 50.72 15.6466 2424.16 0.0895 5.66374 45.66 16.0986 2570.30 0.1023 5.50572 48.41 16.7575 1253.30 0.0895 5.29069 23.61 17.8837 528.70 0.0895 4.95996 9.96 18.1790 2068.20 0.1023 4.88006 38.96 18.6461 2663.26 0.0895 4.75884 50.16 18.8174 1606.35 0.0895 4.71591 30.26 19.5339 314.34 0.0768 4.54452 5.92 19.7767 438.54 0.0895 4.48928 8.26 20.7293 291.48 0.0895 4.28508 5.49 21.3589 2518.45 0.1151 4.16015 47.44 21.7748 573.67 0.0895 4.08164 10.81 22.3767 1835.92 0.1023 3.97319 34.58 22.5713 656.22 0.0512 3.93937 12.36 22.7318 843.79 0.0768 3.91192 15.89 23.2719 506.24 0.1023 3.82234 9.54 23.7453 4139.90 0.1151 3.74719 77.98 24.1138 719.19 0.1023 3.69076 13.55 24.2892 374.86 0.0895 3.66451 7.06 24.7259 1014.59 0.0895 3.60077 19.11 25.0993 2369.88 0.1023 3.54804 44.64 25.6893 456.57 0.1279 3.46787 8.60 26.2905 586.92 0.0624 3.38711 11.06 26.3404 538.09 0.0468 3.38921 10.14 26.6066 757.13 0.1248 3.34759 14.26 26.9884 521.57 0.1092 3.30108 9.82 27.5335 113.88 0.1872 3.23696 2.15 28.0252 1249.17 0.1404 3.18128 23.53 28.4998 96.44 0.0936 3.12937 1.82 28.9700 692.95 0.1560 3.07964 13.05 29.2870 191.82 0.1248 3.04702 3.61 29.5248 138.56 0.1560 3.02302 2.61 30.0582 97.15 0.1092 2.97058 1.83 30.6912 98.55 0.1248 2.91073 1.86 31.6949 208.95 0.1560 2.82081 3.94 32.0814 219.67 0.0780 2.78770 4.14 32.5443 243.64 0.1404 2.74910 4.59 33.0909 289.14 0.0624 2.70493 5.45 33.4658 66.36 0.1248 2.67548 1.25 34.4144 241.94 0.1872 2.60388 4.56
Conclusion
[0363] The amorphous material is capable of forming two different forms; characterized as besylate salt pattern 1 and besylate salt pattern 2.
Example 11: Pharmacokinetic Analysis of Mesembrine Besylate Salt
Materials and Methods
[0364] The amorphous besylate salt prepared in Example 8 was used in addition to mesembrine free base in this example to determine the pharmacokinetic (PK) characteristics of the two.
[0365] Groups of 18 male C57BI/6J mice (weighing between 20 and 30 g) received a single administration of test compound (10 mg/kg; i.p.) in methylcellulose (0.5% w/v) at a nominal concentration of 1.0 ng/mL.
[0366] Three mice from each dose group were subject to cardiac puncture under general anaesthesia at 0.25, 0.50, 1.00, 1.50, 2.00 and 4.00 hrs post-dose and plasma samples generated for application of standard LC-MS/MS bioanalytical methods.
[0367] Quantification of compound concentration was derived from reference calibration data. Pharmacokinetic data were derived from serial plasma concentrations.
Results
[0368] Table 4 details the PK parameters measured using either the mesembrine besylate salt or the free base mesembrine.
[0369]
TABLE-US-00019 TABLE 4 Summary of PK parameters C.sub.max T.sub.max AUC.sub.0-inf t.sub.1/2 Compound (ng/mL) (hr) (ng .Math. hr/mL) (hr) Mesembrine 400 0.25 290 0.454 free base Mesembrine 451 0.25 392 0.615 besylate salt
[0370] Both mesembrine besylate salt and free base demonstrated a short T.sub.max at only 15 minutes, however the half-life of the besylate salt was substantially longer for the besylate salt form of mesembrine than the free base. Here it was seen that the besylate salt had a half-life of 36.9 minutes whereas the free base was 27.2 minutes, a difference of almost 10 minutes.
[0371] Different C.sub.max and AUCs were also found for the two forms of mesembrine. The C.sub.max and AUC were both found to be larger in the mesembrine besylate salt than in the free base. With respect to the AUC the mesembrine besylate salt produced an AUC of over 100 ng.hr/mL greater than that produced by the mesembrine free base.
[0372] Table 5 below details the blood:plasma ratio and the blood:brain ratios observed in both the mesembrine besylate salt and the free base in a separate cohort of satellite animals dosed in the same way but sacrificed at t=0.25 h to obtain brain samples.
TABLE-US-00020 TABLE 5 Summary of mean ratios Plasma Brain Mean Mean concen- concen- blood:plasma blood:brain tration tration Compound ratio ratio (ng/ml) (ng/g) Mesembrine 0.895 0.357 317 1292 free base Mesembrine 1.023 0.395 417 814 besylate salt
[0373] As detailed above, plasma concentrations of besylate salt are greater than those observed with free base, consistent with the observations described in Table 4. Moreover, higher brain exposure was observed in the animals dosed with besylate salt when compared to free base. The mesembrine besylate salt resulted in a higher mean blood to plasma ratio than the free base. Such a difference infers that the salt form is able to enter the plasma at a greater concentration than the free base.
Conclusion
[0374] The ability of the mesembrine besylate salt to preferentially improve the PK properties of the mesembrine free salt demonstrates the importance of using the salt form of mesembrine in pharmaceutical preparations.
[0375] The improvement of PK properties demonstrated by the besylate salt form of mesembrine will enable more of the active to be absorbed and as such a smaller dose of drug can be given. Advantages of this includes a lower cost of active ingredient due to a smaller amount being required to obtain the same effect and also potentially fewer side effects for the patient due to a lower dose of drug being required.
Overall Conclusion
[0376] The Examples 1 to 10 presented above demonstrate that alternative salt forms of mesembrine can be formed using various counterions. The HCl salt is known in the art however there are distinct problems with this salt form as it is only able to solubilise to form a clear solution at relatively low concentrations of mesembrine. This physicochemical property renders the hydrochloride salt unsuitable for development of a pharmaceutical as only low doses of mesembrine could be delivered.
[0377] However, the besylate salt was found to be highly soluble resulting in a solubility of greater than 1000 mg/ml, providing evidence that this salt is highly suitable for development of a pharmaceutical composition.
[0378] Such a finding is surprising as often salts formed from benzenesulfonic acid are rarely found as being of use in active pharmaceutical ingredients. Hydrochloride salts are the most commonly found pharmaceutical salts and are found in approximately 15.5% of all approved medicinal compounds. Sodium and sulphate salts are also found in 9% and 4% of all medicinal compounds respectively.
[0379] The finding that a besylate salt was the most soluble and stable salt in comparison to the hydrochloride and fumarate salts was additionally surprising given the relatively high pKa of benzenesulfonic acid, particularly in comparison to hydrochloric acid. As described in Example 3, a weak acid is unlikely to form a suitable salt due to the inability to complete the proton transfer.
[0380] In the formulation of drug compositions, it is important for the active pharmaceutical ingredient (API) to be in a form in which it can be conveniently handled and processed. This is of importance, not only from the point of view of obtaining a commercially viable manufacturing process, but also from the point of view of subsequent manufacture of pharmaceutical formulations (e.g., oral dosage forms such as tablets) comprising the active pharmaceutical ingredient.
[0381] In the manufacture of oral drug compositions, it is important that a reliable, reproducible and constant plasma concentration profile of the active pharmaceutical ingredient is provided following administration to a patient.
[0382] Chemical stability, solid state stability, and the shelf life of the active pharmaceutical ingredient are also very important factors in the consideration of the form to use for preparation of the pharmaceutical.
[0383] Amorphous materials, such as mesembrine, are typically more difficult to handle and to formulate and are often unstable. Therefore, the mesembrine besylate salt provides a form which can be used in the manufacture of commercially viable and pharmaceutically acceptable drug compositions, as it has been shown to occur as a substantially crystalline and stable form, which is highly soluble.
[0384] Furthermore, the data presented in Example 11 demonstrates that the besylate salt of the invention was able to produce preferential pharmacokinetic properties than mesembrine free base.
Numbered Embldiments
[0385] 1. A mesembrine salt, wherein the salt is taken from the group consisting of mesembrine besylate; mesembrine phosphate; mesembrine tartrate; mesembrine fumarate and mesembrine succinate.
[0386] 2. A mesembrine salt according to embodiment 1, wherein the salt is mesembrine besylate salt.
[0387] 3. A mesembrine salt according to embodiment 1 or embodiment 2, wherein the salt is in a solid form.
[0388] 4. A mesembrine salt according to any of the preceding embodiments, wherein the salt is in a crystalline form.
[0389] 5. A mesembrine salt according to embodiment 2, characterized by an XRPD pattern substantially similar to
[0390] 6. A mesembrine salt according to embodiment 5, characterized by an XRPD pattern comprising peaks at about the positions as described in Table 3.10.
[0391] 7. A mesembrine salt according to embodiment 2, characterized by an XRPD pattern substantially similar to
[0392] 8. A mesembrine salt according to embodiment 7, characterized by an XRPD pattern comprising peaks at about the positions as described in Table 3.13.
[0393] 9. A mesembrine salt according to embodiment 4, wherein the crystalline form is characterized by peaks in an XPRD pattern at 11.1±0.2, 12.7±0.2, 16.6±0.2, 23.8±0.2, and 24.6±0.2°2θ.
[0394] 10. The mesembrine salt according to embodiment 9, further characterized by at least one peak selected from 9.2±0.2, 11.0±0.2, 13.5±0.2, 19.5±0.2, 20.7±0.2, and 21.2±0.2°2θ.
[0395] 11. The mesembrine salt according to embodiment 4, wherein the crystalline form is characterized by peaks in a XRPD pattern at 9.2±0.2, 11.0±0.2, 11.1±0.2, 12.3±0.2, 12.7±0.2, 13.5±0.2, 15.4±0.2, 16.6±0.2, 18.5±0.2, 19.5±0.2, 19.8±0.2, 20.2±0.2, 20.7±0.2, 21.2±0.2, 21.6±0.2, 22.4±0.2, 22.9±0.2, 23.2±0.2, 23.8±0.2, 24.1±0.2, 24.6±0.2, 25.6±0.2, 26.2±0.2, 27.9±0.2, 28.3±0.2, 28.6±0.2, 29.3±0.2, 31.1±0.2, 32.4±0.2, 33.0±0.2, and 33.9±0.2°2θ.
[0396] 12. The mesembrine salt according to embodiment 4, wherein the crystalline form is characterized by peaks in a XPRD pattern at 11.0±0.2, 13.4±0.2, 15.1±0.2, 18.6±0.2, or 23.7±0.2°2θ.
[0397] 13. The mesembrine salt according to embodiment 12, further characterized by at least one peak selected from 15.6±0.2, 16.1±0.2, 18.2±0.2, 21.3±0.2, or 25.1±0.2°2θ.
[0398] 14. The mesembrine salt according to embodiment 4, wherein the crystalline form is characterized by peaks in a XRPD pattern at 3.2±0.2, 7.4±0.2, 9.3±0.2, 11.0±0.2, 11.6±0.2, 12.1±0.2, 12.6±0.2, 13.4±0.2, 14.5±0.2, 15.1 ±0.2, 15.6±0.2, 16.1±0.2, 16.8±0.2, 17.9±0.2, 18.2±0.2, 18.6±0.2, 18.8±0.2, 19.5±0.2, 19.8±0.2, 20.7±0.2, 21.3±0.2, 21.8±0.2, 22.4±0.2, 22.6±0.2, 22.7±0.2, 23.3±0.2, 23.7±0.2, 24.1±0.2, 24.3±0.2, 24.7±0.2, 25.1±0.2, 25.7±0.2, 26.3±0.2, 26.6±0.2, 27.0±0.2, 27.5±0.2, 28.0±0.2, 28.5±0.2, 29.0±0.2, 29.3±0.2, 29.5±0.2, 30.0±0.2, 30.7±0.2, 31.7±0.2, 32.1±0.2, 32.5±0.2, 33.1±0.2, 33.5±0.2, and 34.4±0.2°2θ.
[0399] 15. A process for the preparation of a mesembrine salt comprising the steps of: [0400] a) Dissolving mesembrine in a solvent; [0401] b) Addition of the appropriate counterion to the mesembrine solution under temperature cycling conditions; and [0402] c) Isolation of solids comprising the mesembrine salt.
[0403] 16. A process according to claim 15, wherein the counterion of step b) is benzenesulfonic acid.
[0404] 17. A pharmaceutical preparation comprising a mesembrine salt, wherein the salt is taken from the group consisting of mesembrine besylate; mesembrine phosphate; mesembrine tartrate; mesembrine fumarate and mesembrine succinate.
[0405] 18. A pharmaceutical preparation according to embodiment 17, wherein the salt is mesembrine besylate.
[0406] 19. A pharmaceutical preparation according to either embodiment 17 or claim 18, wherein the preparation produces an elevated blood level of mesembrine of between 80% and 125% compared to those obtained with a pharmaceutical preparation not comprising a salt form of mesembrine.
[0407] 20. A mesembrine salt for use in the treatment of a disease, wherein the salt is taken from the group consisting of mesembrine besylate; mesembrine phosphate; mesembrine tartrate; mesembrine fumarate and mesembrine succinate.
[0408] 21. A mesembrine salt for use according to embodiment 20, wherein the salt is mesembrine besylate.