GB2315216A - Microemulsion preconcentrates comprising FK 506 - Google Patents

Abstract

A pharmaceutical composition for oral administration in the form of a microemulsion preconcentrate contains FK 506 in a carrier medium. The carrier medium comprises a hydrophilic phase, a lipophilic phase and surfactant. The compositions may be encapsulated in gelatin and are stable with improved absorption characteristics.

Description

GALENICAL FORMULATIONS This application is derived from application no. 9410252.2, the contents of which are incorporated herein by reference.

This invention relates to galenic formulations containing FK506. In particular this invention relales to galenic formulations which are in the form of micro-emulsions, micro-emulsion preconcentrates emulsion or emulsion-preconcenuate.

FK506 is a macrolide immunosuppressant that is produced by Strentomyces tsukubaensis No 9993. The structure of FK506 is given in the appendix to the Merck index, as item A5. Also a large number of related compounds which retain the basic structure and immunological properties of FK506 are also known. These compounds are described in a large number of publications, for example EP 184162, EP 315973, EP 323042, EP 423714, EP 427680, EP 465426, EP 474126, WO 91/13889, WO 91/19495, EP 484936, EP 532088, EP 532089, WO 93/5059 and the like. Little is known concerning the biopharmaceutical properties of such compounds. These compounds are termed collectively "FK506 compounds" in this specification.

It has now been surprisingly found that stable compositions containing FK 506 that offer high absorption efficiency. can be obtained by formulating the macrolide with certain carricr media.

Accordingly. this invention provides a pharmaceutical composition comprising FK 506 and a canier medium comprising a hydrophilic phase. a lipophilic phase and a surfactant.

In another aspect the invention provides a pharmaceutical composition which comprises FK 506 and a microemulsion preconcentrate carrier medium therefor which comprises i) a reaction product of castor oil and ethylene oxide, ii) a transesterification product of a vegetable oil and glycerol comprising predominantly linoleic acid or oleic acid mono-. di- and tri-glycerides, or a polyoxyalkylated vegetable oil.

iii) 1.2 propylene glycol and is) ethanol.

The phaimaceutical composition is stable and results in surprisingly high and consistent absorption efficiency when administered orally. Therefore the macrolide may be administered in lower doses, which alleviates toxicity problems. For example, in animal trials in which the pharmaceutical compositions are administered orally, the phaimaceutical compositions resulted in high bioavailabilities. Hence the pharmaceutical compositions have vely surprising properties which offer great advantages.

Preferably the composition is in the form of a "microemulsion preconcentrate". in particular of the type providing O/w (oil-in-waler) microemulsions. However the composition may be in the form of a microemulsion which additionally contains an aqueous phase; preferably water.

A "microemulsion preconcentrate" is defined in this specification as being a formulation which spontaneously fonns a microemulsion in an aqueous medium, for example, in water or in the gastric juices after oral application.

A "microemulsion" is a non-opaquc or substantially non-opaque colloidal dispersion that is formed spontaneously or substantially spontaneously when its components are brought into contact. A microemulsion is thermodynamically stable and contains dispersed particles of a size less than about 200() . Generally microemulsions compiise droplets or particles having a diameter of less than about 1500 ; typically from 30 to 1000 . Further characteristic can be found in Biitish patent application 2 222 770 A; the disclosure of which is incorporated herein by reference.

A "pharmaceutical composition" means a composition in which the individual components or ingredients are themselves pharmaceutically acceptable and, when a particular form of administration is foreseen, are suitable or acceptable for that form of administration.

The lipophilic phase may comprise 10 to 85 % by weight of the carrier medium; preferably 15 to 7() % hy weight more preferably 20 to 60 % by weight and even more preferably about 25 % by weight.

The surfactant may comprise 5 to 80 % by weight of the carrier medium; preferably 10 to 70 % by weight more preferably 20 to 60 % by weight and even more preferably about 40 Sc by weight.

The hydrophilic phase may comprise 10 to 50 % by weight of the canter medium: preferably 15 to 40 % by weight, more preferably 20 to 35 % by weight and even more preferably about 3() % by weight.

The FK 506 is preferably present in an amount of 1 to 15 So by weight of the composition; more preferably about 2 to 10 %.

Examples of compounds of the FK 506 class are those mentioned above. They include for example FK 506, ascomycin and other naturally occurring compounds. They include also synthetic analogues.

A preferred compound of the FK 506 class is disclosed in EP 427 680, e.g. Example 66a.

Other preferred compounds are disclosed in EP 465 426.

The hydrophilic phase may he selected from Transcutol (which has the foimula C2H5-[O- (CH2)2]2-OH). Glycofurol (also known as tetrahydrofurfuryl alcohol polyethylene glycol ether) and 1.2-propylene glycol, or mixtures thereof, and is preferably 1,2-propylene glycol. The hydrophilic phase may include further hydrophilic co-components. for example lower alkanols such as ethanol. These co-components will generally be present in partial replacement of other components of the hydrophilic phase. While Lhe use of ethanol in the compositions is not essential, it has becn found to be of particular advantage when the compositions are to be manufactured in soft gelatine, encapsulated form. This is because storage characteristics are improved in particular the risk of rapamycin precipitation following encapsulation procedures is reduced. Thus the shelf life stability may be extended by employing ethanol or some other such co-component as an additional ingredient of the hydrophilic phase. The ethanol may comprise 0 to 60 % by weight of the hydrophilic phase; preferably 20 to 55% by weight and more preferably about 40 to 50 iG by weight. Small quantities of liquid polyethylene glycols may also be included in the hydrophilic phase.

Preferred lipophilic phase components are medium chain fatty acid triglycerides. mixed mono-, di-, tri-glycel-ides. and transesterified ethoxylated vegetable oils.

Suitable medium chain fatty acid triglycerides are those known and commercially available under the trade names Miglyol, Captex, Myritol, Capmul, Captex. Neobee and Mazol; Mielyol 812 being the most preferred. These triglycerides are described in Fiedler, H. P. "Lexikon der Hilfsstoffe für Pharmazie, Kosmetik und angrenzende Gebiete", Editio Cantor, D-7960 Aulendorf. 3rd revised and expanded edition (1989), the contents of which are hereby incorporated by reference.

The mixed mono-, di-, tri-glycelides preferably comprise mixtures of C12-20 fatty acid mono-, di- and tri-glycerides. especially mixed C16-18 fatty acid mono-, di- and trielycerides. The fatty acid component of the mixed mono-, di- and tri-glycerides may comprise both saturated and unsaturated fatty acid residues. Preferably however they are predominantly comprised of unsaturated fatty acid residues; in particular C18 unsaturated fatty acid residues. Suitably the mixed mono-. di-, tri-glycerides comprise at least 60%, preferably at least 75%, more preferably at least 85% by weight of a C,8 unsaturated fatty acid (for example linolenic, linoleic and oleic acid) mono-. di- and tri-glycerides. Suitably the mixed mono-. di-, tri-elycerides comprise less than 20%, for example about 15% or 10% by weight or less, saturated fatty acid (for example palmitic and stearic acid) mono-, di- and tri-glycerides.

The mixed mono-, di-. tri-glycerides are preferably predominantly comprised of mono- and di-glycerides; for example mono- and di-glycerides comprise at least 50%, more preferably at least 70% based on the total weight of the lipophilic phase. More preferably, the mono- and di-glycerides comprise at Least 75% (for example about 80% or 85% by weight of the lipophilic phase.

Preferably the monoelycerides comprise from about 25 to about 50%. based on the total weight of the lipophilic phase. of the mixed mono-, di-, tri-glycerides. More preferably from about 30 to about 40% (for example 35 to 40%) monoglycerides are present.

Preferably the diglycerides comprise from about 30 to about 60%, based on the total weight of the lipophilic phase, of the mixed mono-, di-, tri-elycerides. More preferably from about 4() to about 55% (for example 48 to 50%) diglycerides are present.

The triglycerides suitahly comprise at least SCio but less than about 25 %, based on the total weight of the lipophilic phase, of the mixed mono-. di-, tri-glycerides. More preferably from about 7.5 to about 15% (for example from about 9 to 12%) triglycerides are present.

The mixed mono-. di-, tri-glycerides may be prepared by admixture of individual mono-, di- or tri-glycerides in appropriate relative proportion. Conveniently however they comprise transesterification products of vegetable oils, for example almond oil. ground nut oil, olive oil, peach oil, palm oil or, preferably, corn oil, sunflower oil or safliower oil and most preferably corn oil, will glycerol.

Such transesterification products are generally obtained by heating the selected vegetable oil with glycerol, at high temperature in the presence of an appropriate catalyst under an inert atmosphere with continuous agitation (for example in a stainless steel reactor) to effect trans-esterification or glycerolysis. In addition to their mono-, di- and tri-glyceride components. the transesterification products also generally comprise minor amounts of free glycerol. The amount of free glycerol present is preferably less than 10%, more preferably less than 5%, most preferably about I or 2% by weight based on the total weight of free glycerol plus mono-, di- and tri-glycerides.

Preferably some of the glycerol is first removed to give a "substantially glycerol free batch" when soft gelatine capsules are to be made.

Trans-esterification products of corn oil and glycerol provide paflicularly suitable mixed mono-, di-. and tri-glycerides An example of a suitable mixed glyceride product is the trans-esterification product commercially available under the trade name MAISINE. This product is comprised predominantly of linoleic and oleic acid mono-, di- and tri-glycerides together with minor amounts of palmitic and stearic acid mono-, di- and tii-glycerides (corn oil itself being complised of about 56% by weight linoleic acid, 30% oleic acid, about 10% palmitic and about 3% stearic acid constituents). The physical characteristics of MAISINE [available from the company Etablissements Gattefossé, of 36, Chemin de Genas, P.O.Box 603. 69804 Saint-Priest, Cedex (France)] are: up to 10% (typically 3.9 to 4.9% or, in "substantially glycerol free" batches, about 0.2%) free glycerol; about 35% (typically 30 to 40% or in "substantially glycerol free" batches, about 32 to 36%, for example about 36%) mono-glycerides; about 50% (or, in "substantially glycerol free" batches about 46 to 48%) di-glycerides; about 10% (or, in "substantially glycerol free" batches, about 12 to 15%) tri-glycerides; and about 1 1% flee oleic acid.

Further physical characteristics for MAISINE are: an acid value of maximum about 2, an iodine no. of about 85 to 105, a saponification no. of about 150 to 175 (Fiedler "Lexikon der Hilfsstoffe", 3rd revised and expanded edition (1989) Vol. 2, p.768). The fatty acid content for MAISINE is typically: about 11% palmitic acid; about 2.5% stearic acid; about 29'70 oleic acid; about 56% linoleic acid; and 1.5% other acids.

It is especially preferred that the mixed mono-, di-, and tri-glycerides are clear and remain clear for more than 20 days upon storage at temperatures of 20 C to 25 C. Also, a sample of the mixed mono-. di-, and tri-glycerides, which has been kept in a refrigerator at about between 2 and 8 C for 24 hours and then held at room temperature for 1 hour, should be clear.

Preferably the mono-, di-, tri-glycerides have a low saturated fatty acid content. Mixed mono-, di-. tri-glycerides meeting these requirements may be obtained from commercially available products by scparation technique as known in the art (for example freezing procedures coupled with separation technique such as centrifugation) to remove the saturated fatty acid components and enhance the unsaturated fatty acid component content. Typically the total saturated fatty acid component content will be less than 15Q. (for example < 10%, or < 5G;,) by weight based on the total weight of the lipophilic phase. A reduction of the content ot saturated fatty acid component in the mono-glyceiide fraction may be observed after being subjected to the separation technique. A suitable process is described in WO 93/()92 11.

The mixed mono-, di-, tri-glycerides thus preferably contain lesser quantities of saturated fatty acids (e.g. palmitic and stearic acids) and relatively greater quantities of unsaturated fatty acids (e.g. olcic and linoleic acids) than the starting material.

A suitable example of a mixed mono-, di-. tri-glyceride product containing lessor quantities of saturated fatty acids contains : 32 to 36% mono-glycerides, 45 to 55% di-glycerides and 12 to 20% tri-glycerides. by weight based on the total weight of the lipophilic phase. Further characteristics include the following:

Fatty acid content Methyl linoleate 53 to 63%.

(as determined as the methyl ester by Methyl oleate 24 to 34%.

chromatography) Methyl linolenate 0 to 3% Methyl arachate 0 to 3%.

Methyl palmitate 6 to 12%.

Methyl stearate 1 to 3% Relative Density 0.94 to 0.96 Hydroxyl Value 140 to 210 Iodine Value 110 to 20 Peroxide Value < 4.0 Free Glycerol < 1.0 Saponification no about 150 to 185 Acid value max. about 2 Mixed mono-. di-. tri-glycerides complying with these characteristics are referred to in this specification as "refined glycerol-transesterified corn oils". The "refined glycerol-transesterified corn oils" have the advantage of remaining stable for a long time.

The lipophilic phase may alternatively comprise suitable transeslelified ethoxylated vegetable oils such as those obtained by reacting various natural vegetable oils (for example, maize oil.

kernel oil, almond oil, ground nut oil, olive oil. soybean oil, sunflower oil. safllower oil and palm oil, or mixtures thereof) with polyethylene glycols that have an average molecular weight of from 200 to 800, in the presence of an appropriate catalyst. These procedures are known and an example is described in US Patent 3 288 824. Transesterified ethoxylated corn oil is particularly preferred.

Transesterified ethoxylated vegetable oils are known and are commercially available under the trade name LABRAFIL (H. Fiedler, loc cit, vol 2, page 707). Examples are LABRAFIL M 2125 CS (obtained from corn oil and having an acid number of less than about 2, a saponification number of 155 to 175, an HLB value of 3 to 4, and an iodine number of 90 to 110), and LABRAFIL M 1944 CS (obtained from kernel oil and having an acid number of about 2. a saponification number of 145 to 175 and an iodine number of 60 to 90).

LABRAFIL M 2130 CS (which is a transesterification product of a C12.18 glyceride and polyelhylene glycol and which has a melting point of about 35 to 40 C. an acid number of less than about 2, a saponification number of 185 to 200 and an iodine number of less than about 3) may also be used. The preferred transesterified ethoxylated vegetable oil is LABRAFIL M 2125 CS which can be obtained, for example, from Gatlefossé. Saint-Priest Cedex, France.

Examples of suitable surfactants are: i) reaction products of a natural or hydroeenated castor oil and ethylene oxide. The natural or hydrogenated castor oil may be reacted with ethylene oxide in a molar ralio of fiom about 1:35 to about 1:60, with optional removal of the polyethyleneglycol component trom the products. Various such surfactants are commercially available.

The polyethyleneglycol-hydrogenated castor oils available under the trade name CREMOPHOR are especially suitable. Particularly suitable are CREMOPHOR RH 40, which has a saponification number of about 50 to 60, an acid number less than about 1, a water content (Fisher) less than about 2%, an np60 of about 1.453 to 1.457 and an HLB of about 14 to 16; and CREMOPHOR RH 60, which has a saponification number of about 40 to 50, an acid number less than about 1, an iodine number of less than about 1, a water content (Fischer) of about 4.5 to 5.5%, an np25 of about 1.453 to 1.457 and an HLB of about 15 to 17. An especially preferred product of this class is CREMOPHOR RH4(). Also suitable are polyethyleneglycol castor oils such as that available under the trade name CREMOPHOR EL, which has a molecular weight (by steam osmometry) of about 1630, a saponification number of about 65 to 7(), an acid number of about 2, an iodine number of about 28 to 32 and an np25 of about 1.47 1.

Similar or identical products which may also be used are available under the trade names NIKKOL (e.g. NIKKOL HCO-40 and HCO-60), MAPEG (e.g. MAPEG CO-40h), INCROCAS (e.g. INCROCAS 40), and TAGAT (e.g. TAGAT RH 4O).

These surfactants are further described in Fiedler loc. cit..

ii) Polyoxyethylene-sorbitan-fatty acid esters, for example mono- and tli-laulyl. palmityl, stearyl and oleyl esters of the type known and commercially available under the trade name TWEEN (Fiedler, loc.cit. p.1300-1304) including the products TWEEN 20 [polyoxyethylene(20)sorbitanmonolaurate], 21 [polyoxyethylene(4)sorbitanmonolaurate] 40 [polyoxytehylene(20)sorbitanmonopalmitate] 60 [polyoxytehylene(20)sorbitanmonostearate], 65 [polyoxytehylene(20)sorbitantristearate], 80 [polyoxytehylene(20)sorbitanmonooleate], 81 [polyoxytehylene(5)sorbitanmonooleate], 85 [polyoxytehylene(20)sorbitantrioleate].

Especially preferred products of this class are TWEEN 40 and TWEEN 80.

iii) Polyoxyethylene fatty acid esters, for example polyoxyethylene stearic acid esters of the type known and commercially available under the trade name MYRJ (Fiedler, loc. cit., 2, p.834-835). An especially preferred product of this class is MYRJ 52 having a D1 of about 1.1., a melting point of about 4() to 44 C, an HLB value of about 16.9., an acid value of about 0 to 1 and a saponilicalion no. of about 25 to 35.

iv) Polyoxyethylene-polyoxypropylene co-polymers and block co-polymers, for example of the type known and commercially available under the trade names PLURONIC.

EMKALYX and POLOXAMER (Fiedler, loc. cit., 9, p. 959). An especially preferred product of this class is PLURONIC F68, having a melting point of about 52 C and a molecular weight of about 6800 to 8975. A further preferred product of this class is POLOXAMER 188.

v) Dictylsulfosuccinate or di-[2-ethylhexyl]-succinate (Fiedler, loc. cit., j, p. 1()7-1()8).

vi) Phospholipida, in particular lecithins (Fiedler, loc. cit., 2, p. 943-944). Suitable lecithins include, in particular soya bean lecithins.

vii) Propylene glycol mono- and di-fatty acid esters such as propylene glycol dicaprylate (also known and commercially available under the trade name MIGLYOL 84()).

propylene glycol dilauratc, propylcne glycol hydroxystearate. propylene glycol isostearate, propylene glycol laurate, propylene glycol ricinoleate, propylene glycol stearate and so forth (Fiedler, loc. cit., 9, p. 808-809).

It will also he appreciated that the components of the carrier medium may contain unreacted starting matcrials, e.g. polyethylene glycol.

The surfactant selected preferably has an HLB of al least 10.

Preferably the relative proportion of hydrophilic phase component(s), the lipophilic phase and the surfactant lie within the "microcmulsion" region on a standard thee way plot. The compositions thus obtained are microemulsion preconcentrates of high stability that are capable, on addition to water, of providing micloemulsions having an average paiiicle size of < 1.5()()A and stable ovcr periods in excess ot 24 hours.

The micromulsion preconcentrate compositions show good stability characteristics as indicated by standard stability trials, for example having a shelf life stability of up to three yeas. and even longer.

Alternatively the components may be selected to provide an emulsion preconcentrate, The emulsion preconcentrate compositions also show good stability characteristics as indicated hy standard stability trials, for example having a shelf life stability of up to three years. and even longer.

The pharmaceutical composition may also include further additives or ingredients. for example antioxidants (such as ascorbyl palmitate, butyl hydroxy anisole (B HA), butyl hydroxy toluene (BHT) and tocopherols) and/or presel-vine agents. These additives or ingredients may comprise about 0.05 to 1% by weight of the total weight of the composition. The pharmaceutical composition may also include sweetening or flavoring agents in an amount of up to about 2.5or 5% by weight based on the total weight of the composition. Preferably the antioxidant is a-tocopherol (vitamin E).

The pharmaceutical composition may also include one or more other immunosuppressants such as. for example, a cyclocporin or if a rapamycin is present a FK 506 compound as described above. Cyclosporings comprise a class of cyclic, poly-N-methylated undecapeptides generally possessing immunosuppressive anti-inllammatoly, anti-viral and/or anti-parasitic activity, each to a greater or lesser degree. The first of the cyclosporins to be identified was the fungal metabolite Cyclosporin A, or Ciclosporine. and its structure is given in The Merck Index, 1 tth Edition; Merck & Co., Inc.; Rahway, New Jersey, USA (1989) under listing 2759. Later cyclosporins to be identified are cyclospolins B, C, D and G which are also listed in the Merck Index under listing 2759. A large number of synthetic analogs are also known and representative examples are disclosed in EP 296 122, EP 484 281 and GB 2222770. These compounds are termed collectively "cyclospoiins" in this specification.

The pharmaceutical composition exhibits especially advantageous properties when administered orally; for example in terms of consistcncy and high level of biovailability obtained in standard hioavailability uials, e.g. 2 to 4 limes higher than emulsions. These trials are performed in animals or healthy volunteers using HPLC or a specific or nonspecific monoclonal kit to determine the level of the macrolide in the blood.

Pharmacokinetic parameters, for example absorption and blood levels, also become surprisingly more predictable and problems in administration with erratic absorption may be eliminated or reduced. Additionally the pharmaceutical composition is effective wilh inside materials for example bile salts, present in the eastro-intestinal tract. That is. the phalmaceutical composition is fully dispersible in aqueous systems comprising such natural tensides and is thus capable of providing microemulsion systems in situ which are stable and do not exhibit precipitation of the active ingredient or other disruption of fine particulate structure. The function of the pharmaceutical composition upon oral administration remains substantially independent of and/or unimpaired by the relative presence or absence of bile salts at any particul macrolide to be used in the clinical tests are as given above while those for the cyclosporin may be in the range of 25 mg to 1000 mg per day and those for a FK506 compound may be 2.5 mg to 18)()() mg per day for a 75 kg adult.

The optimal dosage of macrolide to he administered to a particular patient must he considered carefully by the treating physician as individual response to and metabolism of the rapamycin compound may vary. It may be advisable to monitor the blood serum levels of the rapamycin compound hy radioimmunoassay, monoclonal antibody assay. or other appropriate conventional means. Dosages of the macrolide will generally range from 2.5 mg to 1()()() mo per day for a 75 kilogram adult. preferably 25 mg to 500 mg, with the optimal dosage being approximately 50 to 100 mg per day. Satisfactory results are obtained by administering about 75 mg per day for example in the form of two capsules, one containing 50 mg and one containing 25 mg; or three capsules each containing 25 me. If a cyclosporin or FK506 compound is included in the pharmaceutical composition, the cyclospoiin dosage may be 25 to 10()0 mg per day (preferably 50 me to 500 mg) and the FK 506 compound dosage may be 2.5 mg to 1000 me per day (preferably 10 me to 25() mg).

The pharmaceutical compositions are particularly useful for the following conditions: a) The treatment and prevention of organ or tissue transplant rejection for example for the treatment of the recipients of heart, lung, combined heart-lung, liver, kidney, pancreatic. skin or comeal transplants. The pharmaceutical compositions are also indicated for the prevention of graft-versus-host disease, such as sometimes occurs following hone manow transplantation.

b) The treatment and prevention of autoimmune disease and of inflammatory conditions, in particular inflammatory conditions with an actiology including an autoimmune component such as arthritis (for example rheumatoid arthritis, arthritis chronica progrediente and arthritis deformans) and rheumatic diseases. Specific autoimmune discascs for which the pharmaceutical compositions may be employed include, autoimmune hematological disorders (including e.g. hemolytic anemia, aplastic anemia, pure red cell anemia and idiopathic thrombocytopenia), systemic lupus erythematosus, polychondritis, sclerodoma. Wegener granulomatosis, dermatomyositis, chronic active hepatitis, myasthenia gravis, psoriasis, Steven-Johnson syndrome, idiopathic sprue, autoimmune inflammatory bowel disease (including e.g. ulcerative colitis and Crohn's disease) endocrine ophthalmopathy. Graves disease, sarcoidosis. multiple sclerosis, primary billialy cirrhosis, juvenile diabetes (diabetes mellitus type I), uveitis (anterior and posterior), keratoconjunctivitis sicca and vernal keratoconj uncti vitis, interstitial lung fibrosis, psoriatic arthritis, glomerulonephritis (with and without nephrotic syndrome. e.g. including idiopathic nephrotic syndrome or minimal change nephropathy) and juvenile dermatomyositis.

c) The treatment and prevention of asthma.

d) The treatment of multi-drug resistance (MDR). The rapamycin compounds suppress P-elycoproteins (Pgp), which are the membrane transport molecules associated with MDR. MDR is particularly problematic in cancer patients and AIDS patients who will not respond to conventional chemotherapy because the medication is pumped out of the cells by Pop. The pharmaceutical compositions are therefore useful for enhancing the eflicacy of other chemotherapeutic agents in the treatment and control of multidrug resistant conditions such as multidrug resistant cancer or multidrug resistant AIDS.

The rapamycin compounds also exhibit anti-tumour and antifungal activity and hence the pharmaceutical compositions can be used as anti-tumour and anti-fungal agents.

In a further aspect the invention also provides a process for the production of a pharmaceutical composition as defined above. which process comprises bringing (1) a hydrophilic phase: (2) a lipophilic phase; and (3) a surfactant into intimate admixture and adding the compound of the macrolide class. When required, the composition may he compounded into unit dosage form, for example filing the composition into gelatine capsules.

Optionally further components or additives, in particular a hydrophilic phase co-component, for example ethanol. may he mixed with components (1), (2) and (3) or with or alter addition of macrolide.

The composition may be combined with sufficient water or sufficient of an aqueous solvent medium such that a microemulsion or emulsion is obtained.

The contents of all the references refened to above especially the exemplified compounds are hereby incorporated hy reference. and each of the exemplified compounds may be used as a macrolide in the examples listed below.

The following examples illustrate compositions in unit dosage form, suitable for use, for example in the prevention of transplant rejection or for the treatment of autoimmune disease, on administration of from 1 to 5 unit dosaees/day. The examples are described with particular reference to rapamycin (claimed in the parent application referred to above) but equivalent compositions may he obtained employing any other macrolide.

EXAMPLE 1: Refined glycerol-transesterified corn oil is prepared as follows: Substanlially-glycerol free glycerol-transesterified corn oil is slowly cooled to a temperature of +20 C and kept at this temperature for one night. The corn oil is centiifuged at an acceleration of 12 000 G and at a flow rate of 103 kg/h in a continuous flow centritbge to give a liquid phase (62 ke/h) and a sediment-containing phase (41 ke/h). The liquid phase is slowly coolcd to +8 C and kept at this temperature for one night. The liquid phase is then centrifuged at an acceleration of 12 000 G and at a flow rate of 112 kg/h to give a liquid phase (76.2 kg/h) and a sediment-containing phase (35.8 kg/h). The liquid phase is "refined glycerol-transesterified corn oil". Alternatively an improved product may be obtained by effecting the centrifugation in three steps. e.g. at +200C, +10 C and +5 C.

The process is characterised by a slight percentage reduction in the mono-glyceride component in the refined glycerol transesterified corn oil as compared to the starting material (e.g. 35.6% compared to 38.3%).

EXAMPLE 2: The refined glycerol-transesterified corn oil obtained as described in Example I is used in the preparation of the following oral unit dosage form

COMPONENT QUANTITY (mg/capsule) Rapamycin 20.0 1) Ethanol 75.0 2) 1,2-propylene glycol 81.0 3) refined oil 121.5 3) Cremophor RH40 202.5 Total 500.0 The rapamycin is suspended in (1) with stirring at room temperature and (2), (3) and (4) are added to the obtained solution while stirring. The obtained mixture is lillcd into size 0 hard gelatine capsules and scaled using the Quali-Seal technique.

EXAMPLE 3: Pharmokinetics Two formulations prepared as set out in Example 2 are used:

Formulation Component Amount % A Tween 80 41.5% Maisine 24.9% Propylene glycol 16.6% Ethanol 15.0% Rapamycin 2.0% B Cremophor RH40 41.5% Maisine 24.9% Propylene glycol 16.6% Ethanol 15.0% Rapamycin 2.0% Formulation A is an emulsion preconcentrate and formulation B is a microemulsion preconcentrate. 6 male Wistar rats of mean body weight of 300 g are used per form. One day before treatment, food is withdrawn from the rats but the rats are permitted free access to water. The rats are then anesthetized hy intraperitoneal injection of 2 x 1 ml 20% urethane and a permanent catheter is inserted into the right vena jugularis to permit blood sampling.

500ml/animal of the formulation is administered by gastric intubation 20 hours after the surgery. A total dose of l() mg of drug per animal is administered. Blood samples of 0.7 ml are taken from the jugular catheter of each animal 15 minutes before drug administration and thcn 0.17, ().5. 1. 1.5, 2. 3. 5 and 8 hours after drug administration. The samples are kept in heparinized tubes and are analysed by means of ELISA using microtitre plates coated with rapamycin specilic anlihodics. The animals are killcd immediately after taking the last blood samples. The results are given in the following table:

Form AUC (0-8 CV Cmax- CV tmax CV hrs) [ng.h/ml] | [%] | [ng/ml] | [%] | [hrs] | [%] A 11951 44 2671 42 3.8 29 B 13826 13 3405 30 4.0 35 *) n = 5; +) n = 2 due to difficulties with blood sampling.

Tile results indicate that rapamycin is well absorbed.

Example 4: Comparison Formulations A and B are compared to a formulation comprising 38.6% corn oil, 41.6% Labrafil M21/25C. 17.8% ethanol and 2% rapamycin (formulation C). The same procedure as used in example 3 is used except that the animals each receive a total dose of 0.5 me of drug.

The results are given in the following table:

Form AUC (0-8 CV Cmax CV tmax CV hrs) [ng.h/ml] [%] [ng/ml] [%] [hrs] [%] A 105.8 28 31.22 35 1.6 51 B 96.6 32 36.13 60 0.4 30 C 36.2 31 7.83 27 3.0 78 ) n = 4; The results indicate that formulations A and B provide much better pharmacokinelic properties than formulation C.

EXAMPLE 5: An active compound of the FK 5()6 class or rapamycin class e.g. compound A is made up into a microemulsion preconcentrate having the following composition by weight 2% active compound 44% Cremophor RH40 26.4% corn-oil mono-, di-, tri-glycerides, 17.6% 1.2 propylene glycol and 109 ethanol.

EXAMPLE 6: An active compound of the FK 506 class is made up into a microemulsion preconcentrate having the following composition by weight 2% active compound 449 Cremophor RH4() 26.49 corn-oil mono-. di-. tri-glycerides. 17.6% 1,2 propylene glycol and 10% ethanol.

Claims (15)

1. A pharmaceutical composition for oral administration which is a microemulsion preconcentrate comprising FK506 as active ingredient in a carrier medium which complies i) a hydrophilic component, ii) a lipophilic component, and iii) a surfactant.

the relative proportion of the FK506 compound and components i). ii) and iii) being such that on dilution with water, a microemulsion having an average particle size of < 1.500 A is spontaneously formed.

2. A composition as claimed in claim 1 wherein the hydrophilic component is selected from Transcutanol, Glycofurol and 1,2-propylene glycol or mixtures thereof.

3. A composition as claimed in claim I or 2 wherein the hydrophilic component includes further hydrophilic co-components selected from lower alkanols.

4. A composition as claimed in claim 3 wherein the hydrophilic co-component is ethanol.

5. A composition according to any preceding claim in which the lipophilic component is selected from medium chain fatty acid trigylcerides, mixed mono-, di-. tri-glycerides, and transesterified ethoxylated vegetable oil.

6. A composition as claimed in claim in any preceding claim wherein the surfactant is selected from polyethyleneglycol-hydrogenated castor oils, polyoxyethylene-sorbitan fatty acid esters, polyoxyethylene fatty acid esters, or polyoxyethylene-polyoxypropylene co-polymers and hlock co-polymers.

7. A composition as claimed in claim 6 wherein the surfactant is polyoxyethylene sorbitan monolaurale, a polyoxyethylene sorbilan monopaimitate, polyoxyethylene sorbiian stearate or a polyoxyethylene sorbitan oleate.

8. A composition as claimed in any preceding claim in which the lipophilic component comprises 10 to 85% hy weight of the carrier medium.

9. A composition as claimed in any preceding claim in which the surfactant comprises 5 to 80% hy weight of the canier medium.

10. A composition as claimed in any preceding claim in which the hydrophilic component.

and co-components if present, comprises 10 to 50% by weight of the carrier medium.

11. A composition as claimed in any preceding claim in which FK 5()6 is present in an amount of 1 to 15 % by weight of the composition.

I 2 A composition as claimed in any preceding claim in a soft gelatine encapsulated form.

13. A pharmaceutical composition according to claim 1 wherein the carrier medium comprises i) 1.2-propylene glycol, i) a transesterification product of a vegetable oil and glycerol comprising predominantly linoleic acid or oleic acid, mono-, di-, and tri-glycerides or a polyoxyalkylated vegetable oil, iii) a reaction product of a castor oil and ethylene oxide, and iv) ethanol.

14. A composition according to claim I substantially as described in Lhis specification with reference to any one of the Examples.

15. Use of a microemulsion preconcentrate as defined in any preceding claim in the preparation of medicament suitable for oral administration.