LIPID AGGREGATE FORMING COMPOSITIONS AND THEIR USES

Abstract: Formulations are provided which contain at least one micelle forming monoacyl membrane lipid either alone or preferably in combination with one or more bilayer-forming diacyl membrane lipids. The compositions are characterised by the presence of an effective amount of the monoacyl component and a lipophilic component dissolved or dispersed in a hydrophilic medium in an amount effective to convert the composition into a liquid, gel or semi-solid which has the property of yielding dispersed lipid aggregates upon contact or further diluation with an aqueous medium. Particular liquid pharmaceutical compositions comprise: (a) a mixture of membrane lipids which comprises a micelle-forming lipid and preferably a bilayer-forming lipid; (b) a lipophilic component; (c) at least one hydrophilic medium to mobilise the lipids; and optionally (d) a biologically active compound. Other compositions comprise water in an amount which is effective to hydrate the lipid mixture, and a biologically active compound.

Description: LIPID AGGREGATE FORMING COMPOSITIONS AND THEIR USES FIELD OF THE INVENTION The present invention relates to compositions useful as carriers to transport biologically active materials in general. More specifically, it relates to novel phospholipid formulations of biologically active compounds having improved bio-availability, less variability, low toxicity and ease of use in enhancing penetration, either as liquids or gels for topical and oral applications in various forms . BACKGROUND The problem of bioavailability The ultimate goal in the delivery of active materials is efficacy, which can only be achieved when an optimal amount of biologically active compound is available on site, be it an organ, tissue or in the systemic circulation. Many biologically active compounds are drugs that have poor and variable absorption, resulting in lack of efficacy. In many cases this is due to physical factors such as high molecular weight, poor aqueous solubility, or biological factors manifested in low membrane permeability. Generally, absorption and the membrane permeability of biologically active compounds are strongly influenced by lipophilicity although polarity and H-bonding of the molecule may also play their part. The more lipophilic the compound, the more easily it partitions into biological membranes . The presence of lipophilic groups , however, lead to marked decrease in aqueous solubility and lower concentration at membrane surfaces . This , in turn, leads to lowered uptake and bioavailability. It is generally accepted that lipophilic compounds with molecular weights above about 600 have poor aqueous solubility. Poor absorption is not exclusive to lipophilic compounds . Some hydrophilic compounds e.g. peptides may also have low membrane permeability due to their polar nature and their large molecular size. There is as yet an unfulfilled requirement for safe and effective formulation approaches which enhance penetration and improve bioavailability and decrease variable absorption of poorly absorbed compounds without chemical modification of the active molecule . This applies to both lipophilic and hydrophilic compounds . Phospholipids and their use The use of phospholipids in the form of liposomes as vehicles for drug delivery is well established both in the patent and scientific literature . The limitations of the use of pre-formed liposome preparations has been extensively reviewed (see EP 01558441) and need not be recapitulated here. Many of these limitations can be overcome by the use of phospholipid mixtures in a hydrophilic medium, described as pro-liposome compositions to carry active compounds as first disclosed in EP 0158441. These latter compositions comprise blends of bilayer forming diacyl phospholipids , which on dilution with aqueous fluids formed closed vesicular structures with high entrapment of a biologically active compound. WO 88/06438 discloses similar compositions to the above, and claims desalted charged diacyl lipids in a non aqueous water miscible medium. EP 030577 discloses a method of preparing liposomes using mixtures of diacyl phospholipids dissolved or dispersed in a non-volatile hydrophilic mediu . Departing from the reliance on diacyl phospholipids to carry biologically active compounds, WO 98/58629 discloses substantially homogenous compositions for human administration comprising a biologically active lipophilic compound dissolved in or associated with at least one micelle-forming lipid β- - monoacyl phosphatidylcholine, or blends of monoacyl phosphatidylcholine with diacyl phosphatidylcholine . The compositions were shown to be surprisingly effective in solubilising and improving the bioavailability of compounds that have poor or variable absorption. EP 0256090 discloses the use of a specific monoacyl phospholipid species, namely monoacyl phosphatidyl- ethanolamine and a hydrophobic compound, in the form of a micellar suspension at a pH between 8.2 to 14, for intravenous and other injectable purposes. The use of dilute solutions containing 0.625% w/v MAPC which has 10 or more carbon groups in their fatty acid chain for enhancing the nasal delivery of insulin has also been reported in Pharm Res., Vol 11, No. 11, 1994 p 1623 - 1630. Present Invention An object of this invention is to improve the ability of compositions based on a monoacyl membrane lipids , preferably in combination with a diacyl membrane lipid, to deliver lipophilic and hydrophilic compounds. Another object of this invention is to reduce variable absorption of lipophilic and hydrophilic compounds . A further object of the invention is to enhance the penetration of active compounds in liquid or gel-like formulations . A further object of the invention is to provide a way of making dispersions of lipid aggregates in aqueous media that are stable, of small average particle size, can disperse hydrophilic or lipoplilic materials, and do not require large quantities of energy for their production . The present formulations contain at least one micelle forming monoacyl membrane lipid either alone or in combination with one or more bilayer-forming diacyl membrane lipids , preferably as a minor component . They are characterised by the inclusion in smaller amounts than the lipid components of a lipophilic or water-immiscible component (phase) which may be an oil and which may be in co-solution in a hydrophilic medium. The invention provides a composition for delivering a biologically active compound to a living organism. The composition is further characterised in that it also contains at least one hydrophilic component, preferably a combination of at least two, in an amount effective to render the composition into a clear liquid. Furthermore, the composition has the property of yielding discrete lipid aggregates with mean Z average diameter determined by photon correlation spectroscopy (PCS) below lOOOnm preferably below 500nm, upon contact or further dilution with an aqueous medium. It is predicted that the present compositions will improve the penetration and bioavailability of biologically active compounds for the following reasons . Firstly the compound, and particularly a lipophilic biologically active compound, is molecularly dispersed owing to the dispersing properties of the monoacyl component and hence is readily available for partition into biological membranes . Secondly the monoacyl component, and in particular monoacyl phospholipid, influences the fluidity of biological membranes and facilitates the transport of biologically active compounds across the membranes. The combined effects are predicted to result in improved bioavailability. The invention further provides a liquid pharmaceutical composition comprising: (a) a mixture of membrane lipids which comprises a micelle-forming membrane lipid and preferably a bilayer- forming membrane lipid; (b) at least one lipophilic medium; (c) at least one hydrophilic medium; and optionally (d) a biologically active compound. The formulation principles involved are of general applicability and it should be appreciated that the compositions described are ideally suited for a wide range of applications , externally and internally as a penetration enhancing carrier . The above compositions may be formulated so as to be flowable at room temperature . The composition may also optionally contain polymers which influence the dispersibility characteristics of the composition on exposure to water or aqueous solutions . Other excipients and stabilisers such as organic thickeners, antioxidants , flavourings, anti-microbial agents, buffering agents, colouring agents and sweetening agents may also be included. Similarly, membrane stabilisers such as cholesterol, dicetyl phosphate, stearyl amine and other charged amphipathic compounds may be added to the compositions to improve stability. The formulations exhibit remarkably good storage stability. They are normally liquid presentations at room temperature and may be used as such for topical or oral applications or filled into unit dosage forms e.g. soft gelatin capsules . Lipophilic drugs and other compounds can be solubilised in solutions of at least one monoacyl lipid (e.g. MAPC), preferably with diacyl lipids (e.g. PC) in a hydrophilic medium wherein a lipophilic component is also present. The reason for the use of such mixtures is three-fold. Firstly, such mixtures can solubilise much higher amounts of lipophilic bioactive compounds . Secondly, the presence of the monoacyl lipid influences the structure and size of the lipid aggregates formed on dilution with aqueous medium, and improves the stability of the aggregates. Thirdly, the bioavailability of biologically active compounds may be greatly improved because of better retention and penetration at the absorption surfaces due to the MAPC . On contact with water or other aqueous medium, or upon dilution in such media, the compositions have the potential to form discrete lipid aggregates with a Z average diameter below about lOOOnm, in most cases below 500nm and preferably below 200 nm. The lipid aggregates formed with the lipophilic phase are extremely efficient vectors for transporting biologically active compounds across a membrane. The invention further provides a process for dispersing a biologically active compound, which comprises : dispersing in a hydrophilic medium at least one micelle-forming membrane lipid and a biologically active compound to form an optically clear liquid, gel or semi- solid; and mixing the liquid, gel or semi-solid with aqueous medium to form lipid aggregates below 1000 nm dispersed in the aqueous medium, with the biologically active compound solution or stable dispersion. DESCRIPTION OF PREFERRED FEATURES The lipid component The compositions are a mixture of membrane lipid(s) , lipophilic component, hydrophilic medium and optionally a biologically active compound(s) . The membrane lipid component consists of one or more monoacyl membrane lipids preferably, but not necessarily, in association with one or more diacyl membrane lipids . The monoacyl lipid (s) is preferably the monoacyl derivative of a diacyl phospholipid, eg. monoacyl phosphatidylcholine (MAPC) , but it can also be the monoacyl derivative (s) of glycolipids , sphingolipids , or another micelle forming phospholipid. The lipids may be derived from natural plant, or animal or microbiological sources, synthesised or partially synthesised including polyethyleneglycol (PEG) derived monoacyl phospholipids, eg . pegalated monoacyl phosphatidylethanolamine . The diacyl lipid(s) is preferably a phospholipid because such compounds are readily available and tend to be easy to incorporate in the mix. Examples of phospholipids are phosphatidylcholine (PC) , phosphatidyl ethanolamine (PE) , phosphatidylglycerol (PG) , phosphatidylinositol (PI), phosphatidyl serine(PS), phosphatidic acid (PA) and spingomyelin. The acyl chain can either be unsaturated or saturated and can have 12 to 22, preferably 14 to 18 carbon atoms. Other membrane lipids such as glycolipids , ceramides , gangliosides and cerebrosides can be used in place of, or partial place of, phospholipids. In practice, instead of blending pure fractions of the phospholipids to obtain the target ratios , enzyme modified lecithin (EML) , that have the required proportions of the diacyl to the monoacyl fractions are preferred. The term lecithin generally refers to mixtures of bilayer forming diacyl phospholipids substantially free from micelle forming monoacyl phospholipids . When present in purer commercial grades as a by-product during fractionation, the upper limit for monoacyl phospholipids is usually about 1% to 2% . The relative proportions of monoacyl to diacyl lipid can, however, be greatly enhanced by partial hydrolysis of one or more phospholipids e.g. lecithin. Hydrolysis can be chemical or by an enzyme (e.g. phospholipase A2) or by a micro- organism. The phospholipid mixtures which are classed as enzyme modified lecithins (EML) are freely used in foods without restrictions and provide no problems for oral use . Particularly preferred grades of EML used in this invention are refined by solvent extraction or are chromatographically fractionated, or both, free from residual phospholipase A2 activity. The degree of purification or refinement needed will be appropriate for a pharmaceutical grade material and for the degree of stability required for each particular end use. The methods of purification will be familiar to those skilled in the art. Commercial grades of such material may be obtained from Lucas Meyer GmbH . The membrane lipid/lipids employed in the present invention may be: MAPC Mixtures of PC, and MAPC EML obtained from phospholipase A2 enzyme hydrolysis • Blends of EML with pure PC or MAPC added to obtain the appropriate monoacyl content in the blend. The total weight of membrane lipid in the composition is usually between 20% to 80%, most preferably 40% to 60% , although lesser or greater amounts may be used without departing from the scope of the invention . The proportion of the micelle-forming monoacyl membrane lipid to diacyl membrane lipid by weight in this invention is preferably from 1:20 to 20:1, more preferably 1:10 to 10:1, most preferably 1:5 to 5:1 and still more preferably amounts of the monoacyl component greater than 1:1, or in some cases MAPC on its own may be employed. Preferably the amount of membrane lipid should be greater than the lipophilic content. Contrary to expectations , the lipophilic medium need not exist as stabilised, discrete oil droplets. Unexpectedly, lipid aggregate structures which may be vesicular or non vesicular are formed, depending on the mixture of monoacyl and diacyl lipids , even in the presence of substantial amounts (<10%) of lipophilic medium (oil) . The lipid aggregates formed with less than about 10% of the monoacyl component in the mixture, tend to be mostly vesicular structures whilst those with larger amounts of monoacyl tend to be non vesicular until typical micelles are obtained when the monoacyl content approaches 100%. The micelle forming lipid and the bilayer forming lipid may be in a mixture resulting from deacylation of a phospholipid by means of phospholipase A2. Particularly preferred blends are enzyme modified phospholipids and lecithin of the type used in the food industry containing 60 to 80 mole percent of total monoacyl lipid which includes other phospholipids in addition to PC. The hydrophilic medium The hydrophilic medium normally comprises 10% to 60% by weight, preferably 20% to 40%, of the overall composition, although in many cases amounts greater than 60% may be employed. It may be a C 1 - 5 alcohol eg. ethanol, isopropyl alcohol, propylene glycol, on its own or preferably, in combination with a second hydrophilic component e.g. glycerol, butylene glycol and less preferably polyethylene glycols with molecular weights up to about 1000. The term "hydrophilic medium" is taken to include water-miscible media such as ethoxydiglycol and tetraglycol . These are Cι-C 5 alkyl or tetrahydrofurfuryl di- or partial ethers of low molecular weight mono- or poly-oxy alkanediols eg diethylene glycol monoethyl ether and tetrahydrofurf ryl alcohol polyethylene glycol ether . It also includes partially water-miscible polar media such as propylene carbonate , propylene glycol diacetate , triacetin and dimethyl iso-sorbide. Compounds of this latter type are classified as water-soluble (Martindale, The Extra Pharmacoepia Edition 31) . The above is not an exclusive list, and most hydrophilic media may be used, providing they are pharmaceutically acceptable and can substantially dissolve/disperse the lipid. They could also be present in any combination . In some cases , water may also orm the second hydrophilic component. The preferred hydrophilic medium is chosen from an alkanol and at least one polyol . The preferred alkanol is ethanol , iso-propyl alcohol or n-propyl alcohol and the preferred polyol is glycerol, propylene glycol, butylene glycol . The nature of the active compound will to a large extent determine the amount and the type of hydrophilic medium used, as long as it is water miscible or water soluble within the definition . In some cases , ethanol or isopropyl alcohol, n-propyl alcohol or propylene glycol may be used on its own with water or a sugar solution as the second hydrophilic component, whilst in other cases a mixture comprising ethanol , butylene glycol , glycerol and propylene glycol may be preferred. In yet other cases, one or a combination of polyol , water miscible hydrophilic solvent eg . ethoxy diglycol , propylene glycol carbonate may be used in place of ethanol as the hydrophilic medium. The lipophilic component The lipophilic component in the composition normally comprises between 5% to 50%, preferably 10% to 30% by weight overall . The lipophilic component may be an organic material that is liquid at ambient temperatures, is immiscible with water, and has no surface-active or amphiphilic properties . It will not normally contain ionised groups. Preferably the lipophilic component is an oil and the amount present should be less than the lipid component . It may be a hydrocarbon, fatty acid ester or ether, or a mixture. Alternatively, it may be a volatile oil or a volatile silicone . Typical examples of preferred lipophilic components are ethyl oleate, isopropyl myristate, isopropyl palmitate, medium and long chain triglycerides , propylene glycol esters, volatile/essential oils, and mixtures thereof. Biologically active compounds The composition may further comprise at lease one biologically active compound which has lipophilic and/or hydrophilic properties . Preferably it is in solution in the composition but it may also be in dispersion. The compounds may have pharmaceutical , dietetic or cosmetic uses . Biologically active compounds which may be used with advantage are antioxidants , e.g. ubiquinone, tocopherols , carotenoids , and bioflavonoids . Other examples of therapeutic classes of compound, members of which may be carried in the invention to improve delivery are given below. Antibiotics, antidepressants, antidiabetics , anti- epileptics, antifungals, anti-gout, antihistamines , anti- malarials, antimigraines , antimuscarinics , anti- neoplasties, anti obesity agents, antiprotozoals, antipyretics, anti-virals, anxiolytic, sedatives, hypnotics and anti-psychotics , haemostatics , calcium regulating agents, cardiovascular, chelating agents antidotes, contrast media, corticosteroids, cough supressants/expectorants and mucolytics , dermatological agents, diagnostic agents, disinfectants and preservatives, dopaminergic agents, GI agents, general anaesthetics, genetic material, hypothalmic and pituitary hormones, lipid regulating agents, local anaesthetics, nutritional agents and vitamins, parasympathomimetics , prophylactic anti-asthma agents, prostaglandins , radio pharmaceuticals, resistance modifying agents, immunosuppressants, sex hormones, skeletal muscle relaxants, stimulants/anorectics, sympathomimetics , vaccines, immunoglobulins and antisera, xanthines . Preparation of compositions The compositions may be prepared by dissolving or dispersing the lipid, lipophilic component and the active compound (when present) in the hydrophilic medium to obtain a homogeneous solution. Alternatively, the active compound may be dissolved or suspended in the composition after preparation. Hydration of the compositions On contact with water or other aqueous medium or upon dilution, the compositions have the potential to hydrate to form a gel phase prior to forming discrete lipid aggregates. This may take place either in situ before use or in the GI tract after oral administration. Whilst in many cases , it is important for the biologically active compound to be in molecular dispersion in the lipid aggregates after dilution, in other instances, it may not be necessary for it to be substantially associated with the lipid aggregates . In such cases, the active compound may either be in solution or micro suspension in the aqueous medium. The term lipid aggregates is used here to describe vesicular and non-vesicular structures including liposomes , various species of mixed micelles , micelles , swollen micelles and oil droplets , either as single species or equilibrium mixtures. In some cases, a bi- continuous structure that consists of contiguous interpenetrating domains of both oil and water with neither one surrounding the other may be present, particularly when more than about 10% of lipophilic component is present and the monoacyl component in the phospholipid mixture is high . In preferred examples of the invention, the diluted forms of the compositions are clear to slightly opalescent solutions or dispersions of lipid aggregates . The aggregates are below 500nm Z average diameter . Dispersibility and the different types of aggregate structures formed also depend on a number of factors e.g. the relative amount and the type of diacyl to monoacyl lipid and hydrophilic medium, pH, temperature, viscosity and the presence of other components e.g. polymers and surfactants . The prior art on phospholipids , other than in the liposome literature described earlier, is mainly confined to small amounts of lecithin, usually in the order of 1%- 2% used as general emulsifiers and stabilisers for large amounts of oils , in parenteral nutrition and food processing. These do not cover the present invention which is concerned with the key role of monoacyl membrane lipids preferably in mixtures with diacyl membrane lipids , to form small lipid aggregates comprising a lipophilic phase, below 500nm. The compositions are particularly useful for carrying biologically active compounds for external and internal applications . The invention is also concerned with the property of monoacyl membrane lipids, particularly monoacyl phospholipids in combination with diacyl phospholipids , or enzyme modi ied lecithin (EML) , to enhance the delivery of poorly absorbed compounds . By varying the components present in the compositions , various lipid aggregate structures with high active- loading capacity may be obtained, further setting this invention apart from the prior art. It must be appreciated that spontaneous dispersion into lipid aggregates, or indeed the type of lipid aggregates formed on dilution, is not an essential feature of the invention. In some instances, it may be preferable to maintain the composition in the form of a structured gel, either on its own or inside a hydratable shell . The composition or its diluted/final dispersed form may also be suspended in an external milieu surrounding or in intimate contact with a tissue/organ, mucosal membrane , or skin, from which the active compound may diffuse out. Alternatively, the dispersed form of the composition may be obtained in situ by the addition of water or other aqueous medium prior to use, or the compositions may be administered in unit dosage form e.g. in gelatin capsules or the like. Additionally, the capsules may be enteric coated or protected so that dispersion mainly takes place in the contents of the small intestines or lower in the gastro-intestinal tract eg. colon. Enteric coating or resistance may be obtained by means of e.g. acrylic and methacrylic polymers , whilst site specific colonic delivery may be achieved by the additional use of amylose in the coating or in the formulation . On contact with the gastric or intestinal fluids , the contents of the capsule may also hydrate initially to form a gel . Where the active compound may not have sufficient storage stability in aqueous or hydrophilic medium, it may be added extemporaneously as a powder or suspension to the compositions in situ, to form a structured gel or a suspension of lipid aggregates for administration. Polymers Polymers may influence the dispersion characteristics of the compositions , which surprisingly affect lipid-drug association in this invention. This fact is of particular importance in liquid oral dosage forms . Examples of polymers that affect hydration properties include cellulose derivatives , acrylic and methacrylic polymers , polyglycolic acid, polyethylenes , polypropylenes , polyhydroxybutyrates , etc. Preferably, the polymer is soluble in the hydrophilic me ium or in the composition. Particularly preferred examples are acrylic and methacrylic polymers sold under the brand name Eudragit. Different grades with swelling properties that may be time or pH dependent are available, allowing for control of these parameters in the compositions . The facility to control the hydration, and release of a biologically active compound from a liquid formulation held inside a shell is an unexpected bonus . In some cases , water soluble polymers may also be used in those compositions that contain water . Examples of such polymers are the natural gums , hydroxy propyl methyl cellulose , modified starches , alginates , carboxy vinyl copolymer etc . The amount of polymer, where used, usually need not exceed 10% by weight of the composition, preferably up to 5% , most preferably between 0.5% to 3% . Surfactants The optional use of suitable surfactants need not be precluded. Suitable surfactants include nonionic, anionic, cationic and combinations thereof. Nonionic surfactants are preferred. In addition, other excipients and stabilisers such as inorganic thickeners, antioxidants, flavourings, anti-microbial agents, buffering agents , colouring agents and sweetening agents may be included. Other stabilising agents such as antioxidants and buffering agents may also be incorporated into the compositions as required to enhance the shelf life. Examples of antioxidants include: ascorbic acid, ascorbyl palmitate, butylated hydroxy anisole, butylated hydroxy toulene , α tocopherol or its derivatives . Stabilising agents or buffering agents should be incorporated at a level sufficient to maintain the pH of the composition within the range 4-8, preferably between 5 and 7. Methods of administration Although the invention is ideally suited for topical administration, it must be understood that the compositions may also be administered by oral administration. Topical formulations including creams, ointments, foams, gels, lotions, mousses, for skin and mucosal surfaces and transdermal patches are all within the claims of this invention, and may be easily formulated by those skilled in the art. By appropriate selection of suitable components and presentation concomitant with the route and type of application, the compositions may be given by parenteral administration or for tissue wash-out and irrigation purposes following surgical procedures . They may be used in pulmonary delivery, by inhalation in pressurised metered inhalers or by nebulisation after in situ reconstitution. Examples The invention will now be illustrated below, by way of example and not by way of limitation upon the scope and ambit. Although, enzyme modified lecithin with 30:60 PC:MAPC ratios are used in the examples, alternative blends with different ratios, e.g.80:20; 50:50 and as low as 20:80 may be used in its place. However, the lipid aggregates formed from compositions with less than about 50% of monoacyl components tend to be less transparent and more vesicular. Preferably, but not essentially, the proportion of MAPC should be higher than PC in the blends. The presence of aggregates of 1000 nm or smaller may be detected directly by an electron-micrograph (EM) or may be inferred from the absence of a tendency for the material to flocculate, settle out or sediment. A clear solution with opalescence indicates that the lipid aggregates present have average sizes about 200 nm or below. A clear solution without noticeable opalescence indicates that the lipid aggregates present have average sizes 100 nm or below. Example 1 50 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 25 parts of isopropyl myristate (IPM) and 5 parts of sodium diclofenac were dissolved in 20 parts of ethanol, 10 parts of propylene glycol and 10 parts of glycerol . The composition was heated at 50°C for 12 hours to produce a clear yellow solution . 0.500 g of this composition was diluted with 10 ml of deionised water to yield a clear opalescent dispersion. The Z average particle diameter of the dispersion in water was lOOnm measured in a Malvern Autosizer. Fig. 1 is a typical freeze-fracture electron micrograph showing discrete lipid aggregates. It is apparent from the figure that the aggregates are in the form of vesicles , and the size of the two largest vesicles is about 180 nm. The multi-layered structure is clearly shown in one of the vesicles , each of the layers shown being a lipid bilayer . This composition is suitable for topical application. Alternatively, the diclofenac may be added to the composition after preparation. Example 2 50 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 30 parts of ethyl oleate and 10 parts of vitamin E were dissolved in 17.5 parts of ethanol, 10 parts of propylene glycol and 5 parts of water . The composition was heated at 50°C for 12 hours to produce a clear yellow solution . 0.250 g of this composition was diluted with 10 ml of deionised water to yield a clear yellowish opalescent dispersion. From the appearance of the dispersion (which is influenced by particle size) , it was estimated that the dispersion contained particles of similar size to that produced in Example 1. The vitamin E had become homogeneously dispersed as was apparent from the even colour of the dispersion and showed no tendency to separate . Example 3 40 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 10 parts of Miglyol 810 and 5 parts of vitamin A propionate were dissolved in 20 parts of ethanol, 10 parts of propylene glycol and 5 parts of water. The composition was heated at 50°C for 12 hours to produce a clear yellow solution. 0.400 g of this solution was diluted with 10 ml of deionised water to yield a clear yellow dispersion of microscopic lipid aggregates . From the similarities of this composition to that of example 1 , it was inferred that the properties of the dispersion were the same, and again the vitamin A which is a difficult material to disperse had gone into a homogeneous stable dispersion. In place of a 30:60 lipid mixture, if an 80:20 blend of diacyl to monoacyl components is used, larger, more vesicular lipid aggregates are formed on dilution with water or other aqueous medium. Example 4 50 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 15 parts of Miglyol 812 (a medium chain triglyceride) and 5 parts of clotrimazole were dissolved in 10 parts of ethanol, 20 parts of propylene glycol and 10 parts of water. The composition was heated at 50°C for 12 hours to produce a clear yellow solution. 0.461 g of this composition was diluted with 10 ml of deionised water to produce a clear dispersion, whose properties were as described above . Clotrimazole is a drug that is normally difficult to disperse and tends to crystallize out, but in the dispersion produced in this example these tendencies did not appear and a homogeneous stable dispersion had been produced. Furthermore Miglyol normally tends to give a cloudy suspension with relatively large size particles using diacyl lipids, whereas enzyme modified lipid in the present example has produced a clear dispersion with small lipid aggregates . Example 5 25 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 25 parts of polysorbate 80, 15 parts of a Miglyol 812 and 5 parts of diclofenac (another poorly water-soluble material) were dissolved in 20 parts of propylene glycol and 5 parts of water . The composition was heated at 50°C for 12 hours to produce a clear yellow solution. 0.350 g of this composition was diluted with 10 ml of water to produce a clear colourless dispersion similar to that described in Example 1. Example 6 50 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 50 parts of lemon oil parts were dissolved in 20 parts of ethanol, 10 parts of propylene glycol and 5 parts of water. The composition was heated at 50°C for 12 hours to produce a clear yellow solution. 0.200 g of the composition was diluted with 10 ml of water to yield a clear colourless dispersion. Again effective dispersion of lemon oil in an aqueous medium (which is normally difficult to achieve) had been obtained, and the properties of the resulting dispersion were similar to those of the dispersion in Example 1. Example 7 50 parts of an enzyme modified lecithin (PC:MAPC weight ratio 30:60), 6.25 parts of a monocapric/caprate glyceride and 5 parts of indomethacin were dispersed in 35 parts of ethoxydiglycol , 40 parts of propylene glycol and 30 parts of ethanol .The composition was heated at 50°C to produce a clear yellow solution. 0.4085 g of this composition was diluted with 10 ml of deionised water whilst mixing for 30 seconds at 10,000 rpm using an IKA homogeniser. The resultant dispersion was a translucent opalescent yellow dispersion similar to those in the previous Examples . Example 8 50 parts of an enzyme modified lecithin (PC:MAPC weight ratio 20:80) and 15 parts of IPM were dispersed in 40 parts of butylene glycol and 20 parts of ethanol. The composition was heated at 50°C for 12 hours to produce a clear yellow solution . 0.5 g of this composition was added to 0.02 g of heparin (sodium salt) dissolved in 1.48 g of deionised water. The resultant preparation was a clear yellow solution . This Example shows the dispersion of a hydrohlilic biologically active compound, the properties of the dispersion produced being similar to those of the earlier examples . Example 9 2.5 parts of flurbiprofen , 25 parts of a membrane lipid blend (containing 10%w/w of MAPC, 50%w/w PC, 15%w/w PE and 27.5%w/w other membrane lipids, including charged phospholipids and glycolipids) and 25 parts of a mixture of mono/diglycerides were dissolved in 25 parts of ethanol, 12.5 parts of PG and 12.5 parts of glycerol at 50°C. The resultant preparation was a clear yellow liquid, which formed an opaque dispersion when diluted with water. It was inferred from the optical and settling properties that the mean diameter of the aggregates was about lμm or above, the aggregates being vesicular and having no observed tendency to settle out, flocculate or sediment on storage. Detrimental precipitation of the fluriprofen, which normally happens when organic liquids containing this drug are diluted with water, was not observed. Example 10 25 parts of membrane lipid (containing 7.5%w/w of MAPC, 50%w/w PC, 15%w/w PE and 27.5%w/w of other membrane lipids including charged phospholipids and glycolipids) and 25 parts of IPM were dissolved in 50 parts of ethoxydiglycol . This concentrate was diluted with 900 parts of water containing 10 parts of carbomer (a carboxyvinyl copolymer gelling agent) and 5 parts of vancomycin. The resultant formulation was an opaque yellow gel whose properties were similar to that of Example 9 and which was suitable for topical delivery. This example demonstrates the incorporation of hydrophilic drug into an aqueous medium with a stable dispersed lipid aggregates . It will be appreciated from the above examples that the compositions of the invention may provide an efficient, effective and non-toxic carrier for compounds that have poor bioavailability for a variety of routes of administration .

Claims: Claims : 1. A composition for delivering a biologically active compound to a living organism, said composition comprising at least one micelle-forming membrane lipid, characterised in that the composition contains at least one lipophilic and one hydrophilic component in an amount effective to render the composition into a homogeneous liquid, gel or semi-solid which has the property of yielding dispersed lipid aggregates below 1000 nm upon contact or further dilution with an aqueous medium. 2. The composition of claim 1 , wherein the micelle- forming lipid is a monoacyl derivative of a phospholipid, glycolipid, sphingolipid or pegalated phosphatidyl- ethanolamine . 3. The composition of claim 2 , wherein the micelle- forming lipid comprises monoacyl phosphatidyl choline . 4. The composition of claim 1 , 2 or 3 further comprising at least one bilayer-forming membrane lipid. 5. The composition of claim 4 , wherein the ratio of the micelle-forming lipid to the bilayer-forming lipid is in the range of 10:1 to 1:10. 6. The composition of claim 5, wherein the molar ratio of the micelle-forming lipid to the bilayer-forming lipid is in the range of 4:1 to 1:1. 7. The composition of claim 4 , 5 or 6 , wherein the bilayer-forming lipid is a neutral lipid. 8. The composition of any of claims 4-7, wherein the bilayer forming lipid comprises phosphatidyl ethanolamine , phosphatidyl glycerol , phosphatidyl inositol, phosphatidyl serine, sphingomyelin , glycolipid, or sphingolipid. 9. The composition of any of claims 4-7, wherein the bilayer-forming lipid comprises phosphatidyl choline . 10. The composition of claim 4, wherein the micelle forming lipid and the bilayer forming lipid are in a mixture resulting from deacylation of a phospholipid, or a blend of the deacylated phospholipid with pure micelle- forming lipid or membrane-forming lipid. 11. The composition of claim 10, wherein the mixture results from enzymatic deacylation of lecithin or another phospholipid and contains more than 2% by weight monoacyl phospholipid. 12. The composition of claim 10 or 11, wherein the enzyme modified lecithin or other phospholipid contains 60-80 mole % monoacyl lipid. 13. The composition of claim 10 , 11 or 12 , comprising a refined, enzyme modified lecithin or phospholipid that is substantially free from phospholipase A2. 14. The composition of claim 10, 11 or 12, comprising a refined, chromatographically fractionated enzyme modified lecithin or phospholipid that is substantially free from phospholipase A2. 15. The composition of any preceding claim, wherein the lipophilic component is a hydrocarbon, fatty acid ester or ether, a volatile oil, a volatile silicone or mixtures threreof . 16. The composition of any of claims 1 - 14, wherein the lipophilic component is ethyl oleate, isopropyl myristate, isopropyl palmitate, medium and long chain triglycerides , propylene glycol esters, lemon oil, and mixtures thereof . 17. The composition of any preceding claim, wherein the lipophilic component comprises between 5% and 50% by weight overall . 18. The composition of any of claims 1-16, wherein the lipophilic component comprises 10% to 30% by weight overall . 19. The composition of any preceding claim, wherein the hydrophilic medium comprises 5-90 wt % based on the total weight of the composition . 20. The composition of any of claims 1-19, wherein the hydrophilic medium comprises 20-80 wt % based on the weight of the composition. 21. The composition of any of claims 1-19, wherein the hydrophilic medium comprises 30-60 wt % based on the weight of the composition. 22. The composition of any preceding claim, wherein the hydrophilic medium comprises water or an aqueous liquid as a second component. 23. The composition of claim 22 , wherein the hydrophilic medium comprises a solution of a mono-saccharide or disaccharide sugar . 24. The composition of any preceding claim, wherein the hydrophilic medium comprises a Ci to C 5 alkanol . 25. The composition of claim 20, wherein the alkanol comprises ethanol . 26. The composition of any preceding claim, wherein the hydrophilic medium comprises a polyol . 27. The composition of claim 22, wherein the polyol is glycerol , propylene glycol , polyethylene glycol or a mixture of any of them. 28. The composition of any preceding claim, wherein the hydrophilic medium comprises a partially water-miscible polar material . 29. The composition of any preceding claim, wherein the partially water-miscible polar material is selected from any of dimethylisosorbide, ethoxyglycol , glycofurol, propylene carbonate, propylene glycol diacetate, and triacetin . 30. The composition of any preceding claim, wherein there is present at least 0.1 parts by weight of ethanol and 0.1 parts by weight of polyol per part by weight of lipid. 31. The composition of any preceding claim, further comprising an effective amount of a biologically active compound (other than the lipophilic compound) . 32. The composition of claim 27, comprising at least one biologically active compound belonging to any of the following classes : analgesics and anti-inflammatory agents, anthelmintics , antibiotics, antidepressants, antidiabetics , anti-epileptics, antifungals, anti-gout, a tihistamines, anti-malarials , antimigraines , antimuscarinics , anti-neoplasties, anti obesity agents, antiprotozoals, antipyretics, anti-virals, anxiolytic, sedatives, hypnotics and anti-psychotics , haemostatics, calcium regulating agents, cardiovascular, chelating agents antidotes, contrast media, corticosteroids, cough supressants/expectorants and mucolytics , dermatological agents, diagnostic agents, disinfectants and preservatives , dopaminergic agents , GI agents , general anaesthetics, genetic material, hypothalmic and pituitary hormones, lipid regulating agents, local anaesthetics, nutritional agents and vitamins , parasympathomimetics , prophylactic anti-asthma agents, prostaglandins , radio pharmaceuticals, resistance modifying agents, immunosuppressants, sex hormones, skeletal muscle relaxants, stimulants/anorectics, sympathomimetics , vaccines, immunoglobulins and antisera, and xanthines. 33. The composition of claim 27, wherein the biologically active compound is a lipophilic compound. 34. The composition of claim 27, wherein the biologically active compound is a hydrophilic compound. 35. The composition of any of claims 27-30, wherein the biologically active compound is in solution. 36. The composition of any of claims 27-30, wherein the biologically active compound is in suspension. 37. The composition of claim 27 , wherein the biologically active compound is a water-soluble peptide. 38. The composition of claim 39, wherein the peptide is heparin . 39. The composition of any preceding claim, further comprising a polymer. 40. The composition of claim 41 , wherein the polymer is one or more selected from cellulose derivatives, acrylic and methacrylic polymers, polyglycolic acid, polyethylenes , polypropylenes , and polyhydroxybutyrates . 41. The composition of claim 41 or 41, wherein the polymer comprises 0.5-10 wt % based on the weight of the composition . 42. The composition of claim 43 , further comprising a surfactant. 43. The composition of claim 44, wherein the surfactant is non-ionic. 44. The composition of claim 45, wherein the surfactant is an ethoxylated derivatised fatty acid and/or a polyglyceryl ester . 45. The composition of any preceding claim, further comprising at least one material selected from preservatives, flavourings, organic thickeners, antioxidants, flavourings, anti-microbial agents, buffering agents , colouring agents and sweetening agents . 46. The composition of any preceding claim, which is a liquid. 47. The composition of any of claims 1-47, which is a gel. 48. The composition of any of claims 1-47, which is a semi-solid. 49. The composition of any of claims 1 to 47, which is mobile at room temperature . 50. The composition of any of claims 1-47, which is mobile at an elevated temperature . 51. The composition of any preceding claim, which is for topical application . 52. The composition of any preceding claim, which is a lotion, cream or gel. 53. The composition of any preceding claim in unit dosage form. 54. The composition of claim 54 filled into soft gelatin capsules . 55. The composition of claim 54 filled into hard gelatine capsules . 56. The composition of any of claims 1-54, wherein the powder or suspension of a bioactive compound is added to the lipid composition in situ, to form a structured gel or a suspension of lipid aggregates for administration. 57. The composition of any preceding claim, which has the property of yielding dispersed lipid aggregates below 500 nm upon contact or further dilution with an aqueous medium. 58. The composition of any preceding claim, which has the property of yielding dispersed lipid aggregates below 200 nm upon contact or further dilution with an aqueous medium 59. A liquid pharmaceutical composition comprising: (a) a mixture of membrane lipids which comprises firstly a micelle-forming lipid and secondly a bilayer- forming lipid; (b) a lipophilic component (b) ethanol in an amount effective to mobilise the lipids ; and (c) a polyol in an amount effective to maintain the lipids in solution at room temperature . 60. A liquid pharmaceutical composition comprising: (a) a mixture of membrane lipids which comprises firstly a micelle-forming lipid and secondly a bilayer- forming lipid; (b) a lipophilic component (c) water in an amount which is effective to hydrate the lipid mixture; and (c) a biologically active compound. 61. A method of forming lipid aggregates below lOOOnm which comprises adding water in situ and/or in vivo to a composition according to any preceding claim. 62. Use of the composition of any of claims 1-60 for oral, pulmonary, topical, mucosal and tissue irrigation, to enhance penetration of the biologically active compound compared to the drug alone . 63. Use of the composition of any of claims 1-60 for oral, pulmonary, topical, mucosal and tissue irrigation, to enhance penetration and bioavailability of the biologically active compound compared to the drug alone . 64. A process for dispersing a biologically active compound, which comprises: dispersing in a hydrophilic medium at least one micelle-forming membrane lipid and a biologically active compound to form an optically clear liquid, gel or semi- solid; and mixing the liquid, gel or semi-solid with aqueous medium to form lipid aggregates below 1000 nm dispersed in the aqueous medium, with the biologically active compound solution or stable dispersion. 65. The process of claim 64, wherein the aqueous medium comprises a Ci to C 5 alkanol and a polyol 66. The process of claim 65, wherein the alkanol comprises ethanol and the polyol is glycerol, propylene glycol, polyethylene glycol or a mixture of any of them. 67. The process of 64, 65 or 66, wherein there is dispersed an effective amount of a biologically active compound other than the lipophilic compound.

Inventors: LEIGH MATHEW LOUIS STEVEN, LEIGH STEVEN, LEIGH, MATHEW, LOUIS, STEVEN, LEIGH, STEVEN
Applicants: LEIGH MATHEW LOUIS STEVEN, LEIGH STEVEN, PHARES PHARMACEUTICALS RESEARC, LEIGH, MATHEW, LOUIS, STEVEN, LEIGH, STEVEN, PHARES PHARMACEUTICALS RESEARCH N.V.
Application year: 2000
Main classification: A61K9
IPC codes: A61K9, A61K47