SALTS OF N-(4-OXO-2-(1H-TETRAZOYL-5-YL)-4H-1-BENZOPYRAN-8-YL)-4-(4-PHENYLBUTOXY)BENZAMIDE

Abstract: The invention relates to novel formulations of benzopyran compounds having pharmacological activity, to compositions containing them and to their use in the treatment of certains disorders.

Description: SALTS OF N-(4-0X0-2( lH-TETRAZ0YL-5-YL)-4H-l-BENZ0PYRA -8-YL)-4-(4-PHENYL- BUTOXY)BENZAMIDE This invention relates to novel formulations of compounds having pharmacological activity, to compositions containing them and to their use in the treatment of certain disorders. N-[4-Oxo-2-( 1 H-tetrazol-5-y 1)-4H- 1 -benzopyran-8-yl]-4-(4- phenylbutoxy)benzamide, that is to say, the compound ofthe following structure: is known in the art as a compound which is useful as a leukotriene antagonist. In particular, the compound is disclosed in EPA 173 516 as being useful for the treatment of asthma. However this type of compound is relatively insoluble in many solvents commonly used in pharmaceutical formulations. This is clearly a disadvantage, since solubility can affect the bioavailability of any drug. There is therefore a need for novel formulations which overcome the above problems. It has been found that specific salts of the above compound are surprisingly soluble in certain organic solvents. The present invention therefore provides, in a first aspect, a compound of formula (I): (I) in the form of a salt characterised in that the salt is the sodium, potassium, ammonium calcium, Tris, triethanolamine, ethylenediamine or N-methyl glucamine salt. Preferred inorganic salts include the sodium and ammonium salts. These salts of the compound of formula (I) can be used in therapy, particularly for the treatment of asthma. Thus the invention also provides a salt as described herein, for use as a therapeutic substance, in particular for the treatment or prophylaxis of asthma. Salts ofthe invention can be formulated in standard pharmaceutical compositions. The present invention therefore provides a pharmaceutical composition, which comprises a salt as described herein and a pharmaceutically acceptable carrier or mixture of carriers. The salts ofthe invention show enhanced solubility in aqueous media when compared to the free acid. Therefore the carrier can be an aqueous based carrier. Advantageously, the salts of the invention can be formulated with one or more organic solvents, particularly solvents containing one or more hydroxy groups such as alcohol and glycol solvents. Preferred solvents include polyethylene glycols such as PEG 200 and PEG 400 as well as lower alcohols, in particular ethanol and n-propanol. Mixtures of two or more solvents can be used, including mixtures of alcohols or glycols in water. Particularly preferred compositions which exhibit excellent bioavailability are those containing the ammonium salt in PEG 400. In a particular embodiment of the invention the salts of the invention can be formulated with polyethylene glycols at elevated temperature and the mixture then cooled and used to fill gelatin capsules. Alternatively salts may be prepared in situ at the formulation stage from the parent compound of formula I and appropriate quantities ofa neutralising base such as ammonium carbonate or sodium carbonate. The invention further provides a method of treatment or prophylaxis of asthma, in mammals including humans, which comprises administering to the sufferer a therapeutically effective amount of a salt as described herein. In another aspect, the invention provides the use of a salt as described herein in the manufacture ofa medicament for the treatment or prophylaxis ofthe above disorders. A pharmaceutical composition ofthe invention, which may be prepared by admixture, suitably at ambient temperature and atmospheric pressure, is usually adapted for oral, parenteral or rectal administration and, as such, may be in the form of tablets, capsules, oral liquid preparations, powders, granules, lozenges, reconstitutable powders, injectable or infusable solutions or suspensions or suppositories. Orally administrable compositions are generally preferred, particularly capsules. Compositions for oral administration may be in unit dose form, and may contain conventional excipients known in the pharmaceutical art. Oral liquid preparations may be in the form of, for example, aqueous or oily suspension, solutions, emulsions, syrups or elixirs, or may be in the form ofa dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous vehicles (which may include edible oils), preservatives, and, if desired, conventional flavourings or colourants. For parenteral administration, fluid unit dosage forms are prepared utilising a salt ofthe invention and a sterile vehicle. The salt, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions, the compound can be dissolved for injection and filter sterilised before filling into a suitable vial or ampoule and sealing. Advantageousiy, adjuvants such as a local anaesthetic, preservatives and buffering agents are dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution ofthe compound. The composition may contain from 0.1% to 99% by weight, preferably from 10 to 60% by weight, ofthe active material, depending on the method of administration. The dose ofthe compound used in the treatment of the aforementioned disorders will vary in the usual way with the seriousness ofthe disorders, the weight ofthe sufferer, and other similar factors. However, as a general guide suitable unit doses may be 0.05 to 300 mg, more suitably 5 to 75.0 mg; and such unit doses may be administered more than once a day, for example two or three times a day. The following Examples illustrate the invention. In the experimental section below, the term "Compound I" refers to the compound of formula (I) mentioned herein, i.e. N-[4-Oxo-2-(lH-tetrazol-5-yl)-4H-l-benzopyran-8- yl]-4-(4-phenylbutoxy)benzamide Example 1 Preparation of Inorganic Salts Compound 1 (lO.Og) was added to a stirred solution of anhydrous sodium acetate (1.7g) in methanol (500mL). The clear yellow solution obtained was reduced in volume by rotary evaporation to approximately 50mL and the sodium salt allowed to crystallise. The damp mass was filtered and dried at 50°C to give the sodium salt of Compound 1 (9.3g). The potassium and ammonium salts were prepared in a similar manner by using equimolar quantities of potassium and ammonium acetates. For the calcium salt the calcium acetate to Compound 1 molar ratio was 1 :2. Example 2 Preparation of Organic Salts Compound 1 (lO.Og) was added to a stirred solution of N-methyl glucamine (4.0g) in methanol (500mL). The clear solution obtained was reduced to approximately lOOmL by rotary evaporation and the salt allowed to crystallise. The damp mass was filtered and dried at 50°C to give the N-methyl glucamine salt of Compound 1 (7.6g). A further 1.7g of product was obtained by further concentration ofthe mother liquor. The tris (hydroxymethyl) aminomethane, triethanolamine and ethylene diamine salts were prepared in a similar manner using equimolar quantities of each base except for the ethylene diamine salt where the base to Compound 1 molar ratio was 1 :2. Characterisation of Salts The salts of Compound 1 were characterised by standard spectroscopic techniques and by measurement of physical parameters. A summary of representative physical properties is given in Table 1 Table 1 Physical Properties of Compound 1 Salts Salt Appearance DSC TGA mp Sodium cream 336°C exotherm 0.7% (wt. loss) 290°C-315°C 45°C-1 10°C decompose Potassium cream 290°C exotherm 4% (wt. loss) 256°C-270°C 30°C-115°C decompose Ammonium cream 242°C exotherm 8% (wt. loss) 205°C-234°C 92°C-130°C decompose Tris cream 99°C exotherm 4% (wt. loss) 70°C-95°C 68°C-96°C Triethanolamine cream 169°C exotherm 26% (wt. loss) 145°C-160°C 160°C-280°C Ethylenediamine yellow 134°C, 198°C 3% (wt. loss) 184°C-190°C exotherm 85°C-128°C Example 3 Representative Solubility Data Table 2 Solubility of Compound 1 Salts Expressed in g/l Solvent Salt Water Ethanol PEG 400 Sodium 0.04 >10 >10 Calcium 0.00 0.36 8.42 Ammonium 0.28 9.33 >10 Meglumine 0.34 3.06 9.20 Triethanolamine 0.33 3.91 >10 The aqueous solubility of Compound 1 free acid is less than 0.01 g/l. The salts display an improved aqueous solubility but the improvement is limited. In contrast, the salts are significantly and unexpectedly more soluble in less polar solvents such as alcohols and ethers. The pharmaceutically relevant solvents ethanol and PEG 400 can yield salt solutions with concentrations greater than lOg/1 in certain cases (see table 2). Example 4 In-situ Solubilisation Although the salts of Compound 1 are freely soluble in solvents such as ethanol further improvements have been observed when the salts are prepared in situ. Table 3 Solubility of Compound 1 in 50% Acetate Solution (0.1M) and 50% Ethanol Salt Solubility Potassium Acetate 12.2 Ammonium Acetate 1 1.5 Sodium Acetate 1 1.0 Calcium Acetate 0.4 In the presence of excess acetate the salts formed in situ are freely soluble even in an aqueous alcoholic medium with a water content of 50%. With lower water contents or in the absence of water the solubility can be improved further. For example when PEG 200 (30mL) sodium acetate (2.5g) and Compound 1 (7.4g) were triturated in a mortar and pestle the sodium salt of Compound 1 formed in-situ was solubilised to a concentration greater than 200g/l. The scope of in-situ solubilisation in terms of solvent type and buffer concentration can be seen in Table 4. In these experiments the sodium salt of Compound 1 was prepared through the presence of varying concentrations of sodium phosphate buffer solution with 50% ofthe test solvent. Table 4 Solubility of Compound 1 in 50% solvent systems/50% sodium phosphate (pH7) at different molarities Solvent Solubility (mg/mL) Buffer Concentration 0.1M 0.25M 0.5M Methanol 2.2 1.1 0.9 Ethanol 16.2 N/T N/T n-Propanol 18.0 43.1 56.3 Propylene Glycol 1.7 0.7 0.5 Glycerol 0.2 0.05 0.04 PEG 400 20.5 23.7 26.6 THF 22.3 49.3 100.9 Glycofurol 19.5 N/T N/T N/T Not tested No value was obtained for those N/T samples because the solvents were immiscible with the buffer solution at those concentrations. Solubilities of organic salts of Compound 1 under similar conditions are summarised in Table 5. Table 5 Solubility of Compound 1 in 50% 0.1M salt solution (pH7)/50% Absolute Alcohol Salt Solubility (mg/mL) Tris 1.6 Triethanolamine 2.7 Ethylenediamine 1.7 The solubilities obtained are lower than those for the inorganic salts but can be improved significantly by increasing the pH ofthe solvent system. Example 5 Sample Formulations 1. In situ Salt Formation during Formula Preparation The parent acid of I (4.5 parts by weight) was triturated with anhydrous sodium acetate (1.8 parts by weight) in molten polyethylene glycol (50% by weight of PEG 4000 and PEG 400) sufficient to give a drug concentration of 150mg/mL. The liquid is added in lmL aliquots into capsules and the contents allowed to set on cooling. The ammonium or N-methylglucamine salts of Compound 1 were dissolved in PEG 400 sufficient to give an equivalent parent acid concentration of 5g/l. Example 6 Enhanced Bioavailability of Salt Forms Following oral administration of a PEG 400 solution ofthe N-methylglucamine salt plasma concentrations of Compound 1 were variable but showed evidence of enhanced absoφtion with the absolute bioavailability increasing approximately fourfold relative to the parent acid. The absolute bioavailability increased approximately tenfold upon similar oral administration ofa solution ofthe ammonium salt in PEG 400. The pharmacokinetic data (Table 6) indicated that the ammonium salt was reasonably well absorbed with an absolute bioavailability of approximately 7%. Table 6 Mean ± SD pharmacokinetic parameters for Compound 1 in plasma following administration to rats Route Compound CMAX TMAX (min) THALF AUC )-t or oo BA (%) (ng/mL) a (min) (ug min/mL) a IV Compound 1 23.2 ± 171063.4 ±26025.5 "* " 28.4 oral susp Free Acid 207.4 ± 57.2 22.6+14.9 b 36439.0 ±7316.6 0.80±0.16 c oral susp Meglumine 263.0 ±139.5 97.5 ± 66.2 b 59012.7 ±17096.3 1.29±0.37 c oral susp Ammonium 264.5 ± 64.06 150.5 ±34.1 b 66722.9 ±16472.6 1.46±0.36 c oral soln Meglumine 207.7 ±112.2 53.1±26.8 b 35290.4 ±11719.1 3.09±1.03 c oral soln Ammonium 548.5 ±165.7 53.1 ±29.8 b 81490.5± 23670.3 7.15 ±2.08 c a dose normalised to 3mg/kg for IV, 80mg/kg (acid eq.) for oral suspensions and 20mg/kg (acid eq.) for oral solutions. 5 D insufficient points in the terminal portion ofthe profile to determine a terminal rate constant. c bioavailability based on AUC )-t.

Claims: CLAIMS 1. A compound of formula (I): (I) in the form ofa salt characterised in that the salt is the sodium, potassium, ammonium calcium, Tris, triethanolamine, ethylenediamine or N-methyl glucamine salt. 2. A salt according to claim 1 which is the sodium salt. 3. A salt according to claim 1 which is the ammonium salt. 4. A pharmaceutical composition comprising a salt according to any one of claims 1 to 3 in association with one or more pharmaceutically acceptable carriers. 5. A composition according to claim 4 in which the carrier is a solvent containing one or more hydroxy groups or ether linkages. 6. A composition according to claim 4 or 5 in which the carrier is a lower alcohol. 7. A composition according to claim 4 or 5 in which the carrier is a polyethylene glygol. 8. A salt according to any one of claims 1 to 3 for use in therapy. 9. Use of a pharmaceutical composition according to any one of claims 4 to 7 for the treatment or prophylaxis of asthma.

Inventors: BANTON CHRISTOPHER JOHN, BUXTON PHILIP CHRISTOPHER, BANTON, CHRISTOPHER, JOHN, BUXTON, PHILIP, CHRISTOPHER
Applicants: BANTON CHRISTOPHER JOHN, BUXTON PHILIP CHRISTOPHER, SMITHKLINE BEECHAM PLC, BANTON, CHRISTOPHER, JOHN, BUXTON, PHILIP, CHRISTOPHER
Application year: 1996
Main classification: C07D405
IPC codes: A61K31, A61P11, C07D405