Liposomes containing steroid esters

Claim 1

A process for the preparation of a pharmaceutical composition for administration primarily to the respiratory tract comprising liposomes in combination with a compound of the formula wherein Q is R 1 is a saturated or unsaturated, straight or branched alkyl group with 11-19 carbon atoms and R is H,-COCH 3 , -COC 2 H 5 , -CO(CH 2 ) 2 CH 3 o r -CO(CH 2 ) 3 CH 3 . The degree of inclosure of the steroid to the liposomes are enhanced by the esterification of the steroids in the 21-position. The steroid esters of the formula I are new and constitute a part of the invention. The preferred ester groups are moieties of The preferre steroid ester has the formula All budesonide esters can be obtained in two diastereomeric forms depending on the asymmetric carbon in position 20. The steroid esters are prepared by one of the following alternative methods. A. Reaction of a compound of the formula wherein Q has the definition given above, with a compound of the formula wherein R 1 has the definition given above. The esterification of the 21-hydroxy compound may be effected in known manner e.g. by reacting the parent 21-hydroxy steroid with an appropriate carboxylic acid, advantageously in the presence of trifluoroacetic anhydride and preferably in the presence of an acid catalyst e.g. p-toluenesulphonic acid. The reaction is advantageously effected in an organic solvent such as benzene or methylene chloride; the reaction being conveniently effected at a temperature of 20-100°C. B. Reaction of a compound of the formula wherein Q has the definition given above, with a compound of the formula wherein R 1 has the definition given above and X is a halogen atom, such as chlorine, bromine, iodine and fluorine, or the group wherein R 2 has the same definition as R . The parent 21-hydroxy compound may be treated with the appropriate carboxylic acid halide or anhydride, preferably in a solvent such as halogenated hydrocarbone e.g. methylene chloride and advantageously in the presence of a base such as triethylamine or pyridine, preferably at a low temperature e.g. -5 to +30°C. C. Reaction of a compound of the formula wherein Q has the definition given above and X 1 is a leaving group, with a compound of the formula wherein R 1 has the definition given above and A is a cation. A salt of the appropriate carboxylic acid, for example, an alkali metal e.g. lithium, sodium or potassium salt or a triethylammonium or tetrabutyl ammonium salt may be reacted with the appropriate alkylating agent of the formula Q-X 1 where Q is the same as above and X is a leaving group such as Cl, Br, I, mesylate or p-toluenesulphonate, preferably in a polar solvent such as acetone, methylethyl ketone or dimethyl formamide, conveniently at a temperature in the range 25-100°C. Preparation of the composition according to the invention The lecithins used in this invention have fatty acid chains of different lengths and therefore have different phase-transition temperatures. Examples of lecithins used are those derived from egg and soybean and synthetic lecithins like dimyristoyl phosphatidylcholine (DMPC), dipalmitoyl phosphatidylcholine (DPPC) and distearoyl phosphatidylcholine (DSPC). By manipulation of the structural lecithin stable carriers with variable biodegradable properties could be formulated. This would enable one to prolong the release of the entrapped steroid ester. The extent of the interaction of the steroid ester with e.g. dipalmitoylphosphatidylcholine (DPPC) vesicles is dependent on the ester chain length with increased interaction observed as the chain lengthens. The inclusion of cholesterol or cholesterol derivatives in liposome formulations has become very common due to its properties in increasing liposome stability. The initial stages of the preparation of liposomes according to the present invention may conveniently follow procedures described in the literature i.e. the components being dissolved in a solvent e.g. ethanol or chloroform which is then evaporated. The resulting lipid layer is then dispersed in the selected aqueous medium whereafter the solution is either shaken or sonicated. The liposomes of this invention preferably have a diameter of between 0.1 and 10 µm. In addition to the main liposome-forming lipid(s) which is usually phospholipid, other lipids (e.g. cholesterol or cholesterol stearate) in the amount of 0-40% w/w of the total lipids may be included to modify the structure of the liposome membrane. In optimizing the uptake of the liposome a third component providing a negative charge (e.g. phosphatidic acid) or a positive charge (e.g. stearylamine acetate or cetylpyridinium chloride) may be incorporated. A wide range of proportions of steroid ester to lipid during formation may be used depending on the lipid and the conditions used. Drying, freeze-drying or spray drying)of the liposomes in the presence of lactose can be used with a lactose content in the range of 0 to 95 % of the final composition. The composition according to the invention which is particularly preferred contains liposomes and budesonide-21-palmitate. The routes of administration involves powder aerosols, instillation, nebulization and pressurized aerosols. Working Examples Steroid esters The invention is further illustrated by the following examples to which it is not limited. All the mass spectra have been obtained by chemical ionization mass spectrometry (CH 4 -gas) and they are all in agreement with the molecular weights of the compounds. The purity of each compound has been determined on a HPLC (High Performance Liquid Chromatography) system using a µBondapak C 18 column (300 x 3.9 mm i.d.) with a flow rate of 1.0 ml/min and with ethanol/H 2 0 in ratio between 70:30 and 90:10 as the mobile phase. Example 1. Budesonide-21-palmitate (Method B) Budesonide (1 mmole) was dissolved in pyridine (20 ml). Palmitoyl chloride (2 mmole) was added at 0°C and then at ambient temperature overnight. While cooling the mixture with ice 2M hydrochloric acid was added until acidic reaction. The mixture was extracted with chloroform (3x50 ml). The organic phase was successively shaken with 5% sodium bicarbonate and water, dried (Na 2 S0 4 ) and evaporated. The raw material was purified by preparative thin layer chromatography (Silica gel; 3% EtOH: 97% CHCl 3 ). Yield: 40%. Purity: 95.5%. MS-CI (CH 4 ): MH + = 669, M + 29 = 697. Example 2. Budesonide-21-laurate (Method B) Reaction of budesonide (0.5 mmole) with lauryl chloride (0.25 ml) in pyridine (3 ml) according to Example 1 gave after preparative thin-layer chromatography (Silica gel; 3% EtOH: 97% CHC1 3 ) the title compound. Yield: 47%. MS-CI (CH 4 ): MH + = 613, M + + 29 = 641. Example 3. Budesonid-21-myristate (Method B) The myristoyl chloride was synthesized by refluxing myristic acid (7.0 g) and thionyl chloride (9 ml) in trichloroethylene (100 ml) for 3 hours. The solvent was then evaporated. Budesonide (2 mmole) and myristoyl chloride (2.4 mmole) in methylene chloride (40 ml) was treated with triethylamine (2.4 mmole) in methylene chloride (10 ml) for 2 hours at room temperature. Methylene chloride was added and the organic phase was successively treated with 1M HC1 and water (3 x 100 ml). Chromatography (Sephadex LH20; chloroform) after drying (Na 2 S0 4 ) and evaporation of the solvent gave the title compound in 65% yield. Purity: 98.2%. MS-CI (CH 4 ): MH + = 641; M + + 29 = 669. Example 3b. Budesonide-21-myristate (Method C) Budesonide-21-mesylate (0.5 mmole; prepared according to CA 57, 13842d (1962)), myristic acid (0.5 mmole) and triethylamine (0.5 mmole) in dimethylformamide (10 ml) was stirred for 2 hours at 50°C. The solvent was evaporated in vacuo and using the same work-up procedure as in method B gave after chromatography the title compound, identical with the compound isolated in method B. Example 3c. Budesonide-21-myristate (Method A) Budesonide (1 mmole), myristic acid (1 mmole) and p-toluenesulfonic acid (5 mg) were refluxed in benzene (30 ml) for 5 hours. The organic phase was successively shaken with 5% sodium bicarbonate and water, dried (Na 2 S0 4 ) and evaporated. Purification by preparative thin-layer chromatography gave the title compound, identical with the compound isolated in method B. Example 4. Budesonide-21-stearate (Method B) Reaction of budesonide (1 mmole) with stearoyl chloride (1.0 ml) in pyridine (6 ml) according to Example 1 gave after preparative thin-layer chromatography (Silica gel; 3% EtOH: 97% CHC1 3 ) the title compound. Yield: 74%. MS-CI (CH 4 ): MH + = 697; M + + 29 = 725. Example 5. Budesonide-21-oleate (Method B) Reaction of budesonide (1.16 mmole) and oleoyl chloride (1.4 mmole) in methylene chloride (50 ml) with triethylamine (1.4 mmole) in methylene chloride (5 ml) 2 hours at room temperature gave after work-up (example 3) and chromatography (Silica gel; hexane-acetone (80:20)) the title compound in 22% yield. Purity: 98.7%. MS-CI (CH 4 ): MH + = 695; M + + 29 = 723. Example 6. Betamethasone-21-laurate (Method B) Reaction of betamethasone (2 mmole) and lauryl chloride (2.4 mmole) in dimethylformamide (20 ml) with triethylamine (2.4 mmole) in dimethylformamide (5 ml) for 2 hours at room temperature gave after evaporation of dimethylformamide and work-up (example 3) and chromatography (Silica gel; hexane-acetone (60:40)) the title compound in 22% yield. Purity: 92.7%. MS-CI (CH 4 ): MH + = 575; M + + 29 = 603. Example 7. Betamethasone-21-myristate (Method B) Reaction of betamethasone (2 mmole) and myristoyl chloride (2.4 mmole) in methylene chloride (40 ml) and dimethylformamide (5 ml) with triethylamine (2.4 mmole) in methylene chloride (10 ml) for 2 hours at room temperature gave after evaporation of dimethylformamide and work-up (example 3) and chromatography (Silica gel; hexane-acetone (70:30)) the title compound in 29% yield. Purity: 97%. MS-CI (CH 4 ): MH + = 603; M + + 29 = 631. Example 8. Betamethasone-21-palmitate (Method B) Reaction of betamethasone (0.5 mmole) with palmitoyl chloride (1.0 mmole) in pyridine (10 ml) according to Example 1 gave after preparative thin-layer chromatography (Silica gel 3%; EtOH: 97% CHC1 3 ) the title compound. Yield: 33%. MS-CI (CH 4 ): MH + = 631; M + + 29 = 659. Example 9. Betamethasone-21-oleate (Method B) Reaction of betamethasone (2 mmole) and oleoyl chloride (3 mmole) in dimethylformamide (20 ml) with triethylamine (3 mmole) in dimethylformamide (5 ml) for 2 hours at room temperature gave after evaporation of dimethylformamide and work-up (example 3) and chromatography (Sephadex LH20; chloroform) the title compound. Purity: 96.7%. MS-CI (CH 4 ): MH + = 657; M + + 29 = 685. Example 10. Betamethasone-21-laurate-17-valerate (Method B) Reaction of betamethasone-17-valerate (2 mmole) and lauroyl chloride (2.4 mmole) in methylene chloride (90 ml) with triethylamine (2.4 mmole) in methylene chloride (10 ml) for 2 hours at room temperature gave after work-up (example 3) and chromatography (Sephadex LH20; chloroform) the title compound in 62% yield. Purity: 97.8%. MS-CI (CH 4 ): MH + = 659; M + + 29 = 687. Example 11. Betamethasone-21-myristate-17-valerate Reaction of betamethasone-17-valerate (2 mmole) and myristoyl chloride (2.4 mmole) in methylene chloride (90 ml) with triethylamine (2.4 mmole) in methylene chloride (10 ml) for 2 hours at room temperature gave after work-up (example 3) and chromatography (Sephadex LH20; chloroform) the title compound in 62% yield. Purity: 95.5%. MS-CI (CH 4 ): MH + = 687; M + + 29 = 715. Example 12. Betamethasone-21-palmitate-17-valerate Reaction of betamethasone-17-valerate (1 mmole) and palmitoyl chloride (1.2 mmole) in methylene chloride (50 ml) with triethylamine-(1.2 mmole) in methylene chloride (10 ml) for 2 hours at room temperature gave after work-up (example 3) and chromatography (Sephadex LH20; chloroform) the title compound in 63% yield. Purity: 95.9%. MS-CI (CH 4 ): MH + = 715; M + + 29 = 743. Example 13. Betamethasone-21-stearate-17-valerate (Method B) Reaction of betamethasone-17-valerate (2 mmole) and stearyl chloride (2.4 mmole) in methylene chloride (90 ml) with triethylamine (2.4 mmole) in methylene chloride (10 ml) for 2 hours at room temperature gave after work-up (example 3) and chromatography (Sephadex LH-20; chloroform:heptane:ethanol (20:20:1)) the title compound in 59% yield. Purity: 92%. MS-CI (CH 4 ): MH + = 743; M + + 29 = 771. Example 14. Flumethasone-21-laurate (Method B) Reaction of flumethasone (1.0 mmole) and lauroyl chloride (1.5 mmole) in dimethylformamide (5 ml) and methylene chloride (40 ml) with triethylamine (1.5 mmole) in methylene chloride for 2 hours at room temperature gave after evaporation of dimethylformamide and work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 64% yield. Purity: 97.7%. MS-CI (CH 4 ): MH + = 593; M + + 29 = 621. Example 15. Flumethasone-21-palmitate (Method B) Reaction of flumethasone (0.5 mmole) with palmitoyl chloride (1.0 mmole) in pyridine (10 ml) according to Example 1 have after preparative thin-layer chromatography (Silica gel; 3% EtOH: 97% CHC1 3 ) the title compound. Yield: 38%. Purity: 98.5%. MS-CI (CH 4 ): MH + = 649; M + + 29 = 677. Example 16. Flumethasone-21-stearate (Method B) Reaction of flumethasone (1.0 mmole) and stearoyl chloride (1.5 mmole) in dimethylformamide (5 ml) and methylene chloride (40 ml) with triethylamine (1.5 mmole) in methylene chloride (10 ml) gave after evaporation of dimethylformamide and work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 38% yield. Purity: 90%. MS-CI (CH 4 ): MH + = 677. Example 17. Flumethasone-21-oleate (Method B) Reaction of flumethaosne (1.0 mmole) and oleoyl chloride (1.5 mmole) in dimethylformamide (5 ml) and methylene chloride (40 ml) with triethylamine (1.5 mmole) in methylene chloride (10 ml) gave after evaporation of dimethylformamide and work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 12% yield. Purity: 98.2%. MS-CI (CH 4 ): MH + = 675; M + + 29 = 703. Example 18. Flumethasone-21-laurate-17-propionate (Method B) Reaction of flumethasone-17-propionate (1 mmole) and lauroyl chloride (1.5 mmole) in methylene chloride (40 ml) with triethylamine (1.5 mmole) in methylene chloride (10 ml) gave after work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 33% yield. Purity: 94.4%. MS-CI (CH 4 ): MH + = 649; M + + 29 = 677. Example 19. Flumethasone-21-myristate-17-propionate (Method B) Reaction of flumethasone-17-propionate (1 mmole) and myristoyl chloride (1.7 mmole) in methylene chloride (40 ml) with triethylamine (1.7 mmole) in methylene chloride (10 ml) gave after work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 55% yield. Purity: 96.7%. MS-CI (CH 4 ): MH + = 677. Example 20. Flumethasone-21-palmitate-17-propionate (Method B) Reaction of flumethasone-17-propionate (2.8 mmole) and palmitoyl chloride (3.3 mmole) in methylene chloride (150 ml) with triethylamine (3.3 mmole) in methylene chloride (10 ml) gave after work-up (example 3) and chromatography (Sephadex LH20; chloroform) the title compound in 14% yield. Purity: 98.8%. MS-CI (CH 4 ): MH + = 705; M + + 29 = 733. Example 21. Flumethasone-17-propionate-21-stearate (Method B) Reaction of flumethasone-17-propionate (1.0 mmole) and stearoyl chloride (1.5 mmole) in methylene chloride (40 ml) with triethylamine (1.5 mmole) in methylene chloride (10 ml) gave after work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 44% yield. Purity: 95%. MS-CI (CH 4 ): MH + = 733; M + + 29 = 761. Example 22. Flunisolide-21-laurate (Method B) Reaction of flunisolide (0.5 mmole) and lauroyl chloride (0.64 mmole) in methylene chloride (20 ml) with triethylamine (0.64 mmole) in methylene chloride (5 ml) gave after work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 65% yield. Purity: 97.6%. MS-CI (CH 4 ): MH + = 612; M + + 29 = 645. Example 23. Flunisolide-21-myristate (Method B) Reaction of flunisolide (0.5 mmole) and myristoyl chloride (0.65 mmole) in methylene chloride (20 ml) with triethylamine (0.65 mmole) in methylene chloride (5 ml) gave after work-up (example 3) and chromatography (Silica gel; hexane:acetone (60:40)) the title compound in 54% yield. Purity: 98.5%. MS-CI (CH 4 ): MH + = 645; M + + 29 = 673. Example 24. Flunisolide-21-palmitate (Method B) Reaction of flunisolide (433 mg), palmitoyl chloride (400 mg) and triethylamine (500 mg) in methylene chloride (8 ml) for 2 hours at room temperature gave after work-up (example 3) and preparative thin-layer chromatography (Silica gel; chloroform) the title compound in 29% yield. Purity: 98.5%. MS-CI (CH 4 ): MH + = 673; M + + 29 = 701. Example 25. Flunisolide-21-stearate (Method B) Reaction of flunisolide (0.46 mmole) and stearoyl chloride (0.7 mmole) in methylene chloride (40 ml) with triethylamine (0.7 mmole) in methylene chloride (10 ml) gave after work-up (example 3) and chromatography (Silica gel; hexane:acetone (70:30)) the title compound in 53% yield. Purity: 92%. MS-CI (CH 4 ): MH + = 701; M + + 29 = 729. Example 26. Beclomethasone-21-palmitate-17-propionate (Method B) Reaction of beclomethasone-17-propionate (40 mg), palmitoyl chloride (100 mg) and triethylamine (50 mg) in methylene chloride (5 ml) for 2 hours at room temperature gave after work-up (example 3) and preparative thin-layer chromatography (Silica gel; 3% EtOH: 97% CHC1 3 ) the title compound in 54% yield. MS-CI (CH 4 ): MH + = 703. Example 27. Dexamethasone-21-palmitate-17-propionate (Method B) Reaction of dexamethasone-17-propionate (4 mmole) and palmitoyl chloride (8 mmole) in methylene chloride (100 ml) with triethylamine (8 mmole) in methylene chloride (30 ml) for 2 hours at room temperature gave after work-up (example 3) and chromatography (Sephadex LH20; heptane: chloroform:ethanol (20:20:1)) the title compound in 25% yield. Purity: 96%. MS-CI (CH 4 ): MH + - 687; M + + 29 = 715. Compositions Example 1. Preparation of a formulation for instillation Synthetic dipalmitoylphosphatidylcholine (45 mg), cholesterol (2.25 mg) and budesomde-21-palmitate (4.5 mg) are mixed in a glass tube. All components are dissolved in chloroform. Most of the solvent is evaporated by the use of N 2 and then under reduced pressure, which forms a thin film of the lipid components on the surface of the glass tube. An aqueous solution (0.9% NaCl) is added to the lipids. Formation of the liposomes is performed at a temperature above the phase transition temperature of the lipids. The liposomes are formed by shaking or sonication of the solution with the probe of a sonicator. The resulting suspension contains liposomes ranging from very small vesicles to 2 pm in size. Example 2. Preparation of a formulation for inhalation The preparation of the liposomes is performed according to Example 1, where the aqueous solution contains 10% lactose. The ratio between lactose and lipid is 10:1. The liposome suspension is frozen on dry ice and lyophilized. The dry product is micronized resulting in particles with a mass mean aerodynamic diameter (MMAD) of about 2 pm. Biological Tests Anti-inflammator effect Intratracheal instillation of Sephadex beads into rats leads to bronchial and also to alveolar inflammation. This provokes interstitial lung edema, which increases the lung weight, and the inflammation can be graded as the increase of the lung weight compared to a saline- instilled control group. The lung edema formation can be counteracted by pretreatment with glucocorticoids, preferably by local administration as intratracheal instillation or as inhalation. Ideally an anti-inflammatory action should be obtained only at the site of glucocorticoid application in the lung, but not in the rest of the body as this in long term treatment can lead to therapy limiting systemic side effects. The differentiation between glucocorticoid actions in the treated lung region and outside this area can be tested in the following way. Sprague Dawley rats (225 g) were slightly anaesthetized with ether and the glucocorticoid test preparation (in liposomes suspended in saline) in a volume of 0.5 ml/kg was instilled into just the left lung lobe. Two h later a suspension of Sephadex (5 mg/kg in a volume of 1 mg/kg) was instilled in the trachea well above the bifurcation so that the suspension reached both the left and right lung lobes. Twenty h later the rats were killed and the left and right lung lobes dissected out and weighed separately. Also the spleen weight and the body weight gain over the 20 h were determined. Control groups got vehicle instead of glucocorticoid preparation and saline instead of Sephadex suspension to determine the weight of non-drug treated Sephadex edema and the normal lung weight as well as the normal spleen weight and body weight gain. As stated above an ideal glucocorticoid preparation should have a very high glucocorticoid activity at the site of application in lung, but with low activity outside this area. Therefore, in the selected model an optimal preparation should more or less completely block the edema in the locally pretreated left lung lobe, but have much less activity in the right lung half and no significant inhibitory action on the spleen weight and the body weight gain. It has been considered more important to search for a high degree of separation between the local activity (exemplified with the left lung) to the other activities than to search for a high absolute potency (high activity per mg drug) for the action in the left lung. In the test protocol used, doses were selected leading to a more or less complete block of the edema in the left lung and at these dose levels the extent of the other activities was estimated. At the selected dose 7-9 rats were tested in parallel. Mean ± s.e.m. was calculated and compared with Student's t-test to the results of the corresponding Sephadex control group. The results of the comparative studies are given in Table 1. The pharmacological profile of the new compounds was compared to that of budesonide (selected as a conventional glucocorticoid having some local activity as judged in skin tests) and to those of budesonide-21- valerate, dexamethasone-21-palmitate, fluocinolone acetonide-21-palmitate and hydrocortisone-21-palmitate (representing compounds outside the scope of the invention). Budesonide, budesonide-21-valerate and hydrocortisone-21-palmitate did not fulfil the requirement of a very high local activity (only up to 38% reduction of edema in left lung). Dexamethasone-21-palmitate and fluocinolone-21-palmitate completely blocked the left lung edema, but this was coupled to as high activity in the other lung half as well as to significant reduction of body weight gain and to spleen (Table 1). Thus, none of the tested preparations falling outside the scope of the invention had selective glucocorticoid activity for the site of application in lung. The preparations of the new compounds of the invention had a much more selective activity for the application site in lung. They all more or less completely blocked the edema of the left lung (minimum 87 % protection for beclomethasone-21-palmitate-17-propionate). This was surprisingly coupled to only a low or moderate protective activity in the other lung (maximally about 45% protection) and to no statistically significant reduction of body weight gain or spleen. Table 1.