United States Patent:  6,045,828

Assignee:  Astra Aktiebolag (SE)

Filed:  March 20, 1996

A proliposome powder, said powder comprising in a single phase discrete particles of a biologically active component together with a lipid or mixture of lipids having a phase transition temperature of below 37^oC. and a process for the manufacture of a proliposome powder for inhalation.

DISCLOSURE OF THE INVENTION

The above object of the present invention is achieved in the provision according to the present invention of a proliposome powder, said powder comprising in a single phase discrete particles of a biologically active component together with a lipid or mixture of lipids having a phase transition temperature (T_c) of below 37^oC.

The powder is particularly suitable for administration by inhalation.

The single phase powder may alternately be described as comprising a homogeneous molecular mixture of a biologically active component and a lipid or mixture of lipids having a phase transition temperature of below 37^oC.

It will be understood from the terms "single phase" and "homogeneous molecular mixture" that there is no separate crystalline phase of either active component or lipid in the powder of the present invention.

The single phase powder can be inhaled directly and in situ, for example in the upper or lower respiratory system, will form liposomes in which a biologically active component is totally incorporated.

In general, any amphipathic lipid or mixture of lipids known to be suitable for preparing liposomes by known methods could be used in the present invention. The lipid or lipid mixture must have a phase-transition temperature below body temperature (37^oC.) in order for th product proliposome powder to be capable of hydration under physiological conditions (i.e. in order to be able to form liposomes in the respiratory system). Phase-transition temperatures for different lipid mixtures may be estimated easily, using well-established methods, for example DSC methods--see for example J. Suurkuusk et al., Biochemistry, vol. 15, no. 7, p. 1393 (1976). In general any natural or synthetic lipid or mixture of lipids having a phase transition temperature below 37^oC. is useful in the present invention.

As examples of potentially useful lipids may be mentioned natural and synthetic lipids such as natural and synthetic phosphoglycerolipids, sphingolipids, and digalactosylglycerolipids. Amongst natural lipids may be mentioned sphingolipids (SL) such as sphingomyelin (SM), ceramide and cerebroside; galactosylglycerolipids such as digalactosyldiacylglycerol (DGalDG); phosphoglycerolipids such as egg-yolk phosphatidylcholin (e-PC) and soya-bean phosphatidylcholin (s-PC); and lecithins such as egg-yolk lecithin (e-lecithin) and soya-bean lecithin (s-lecithin). Amongst synthetic lipids may be mentioned dimyristoyl phosphatidylcholin (DMPC), dipalmitoyl phosphatidylcholin (DPPC), distearoyl phosphatidylcholin (DSPC), dilauryl phosphatidylcholin (DLPC), 1-myristoyl-2-palmitoyl phosphatidylcholine (MPPC), 1-palmitoyl-2-myristoyl phosphatidylcholine (PMPC), and dioleoyl phosphatidycholin (DOPC). Amongst mixtures of lipids may be mentioned the following: SM/PC, SM/Cholesterol, ePC/Cholesterol, sPC/Cholesterol, PC/PS/Cholesterol, DMPC/DPPC, DMPC/DPPC/CH, DMPC/CH, DPPC/DOPC, DPPC/DOPC/CH, DLPC/DPPC, DLPC/DPPC/CH, DLPC/DMPC, DLPC/DMPC/CH, DOPC/DSPC, DPSM/DMSM, e-lecithin/Cholesterol and s-lecithin/Cholesterol. In addition to any of the above there may be included a charged lipid such as dimyristoyl phosphatidylglycerol (DMPG), diphospalmitoyl phosphatidylglycerol (DPPG), dimyristoyl phosphatidic acid (DMPA), dipalmitoyl phosphatidic acid (DPPA) or stearylamine (SA).

Lipids of particular interest in the present invention are DPPC and/or DMPC. A mixture of DPPC and DMPC containing at least 10% (w/w) DMPC is preferred, for example 10-50% DMPC. Especially preferred is a mixture of DPPC and DMPC containing in addition at least one charged lipid sich as DMPG, DPPG, DMPA or SA, for example in an amount of up to 5% (w/w). Other preferred mixtures include DPSM and DMSM optionally containing at least one charged lipid, and mixtures of cholesterol with either e-lecithin or s-lecithin, optionally containing at least one charged lipid, and having a T_c of less than 37^oC. Other mixtures can be selected easily by a person skilled in the art with reference for example to Gregor Cevc, Phospholipids Handbook, Marcel Dekker, New York (1993) pp 427-435.

The active component preferably has a molecular structure which can be incorporated into the lipid bilayers, to aid encapsulation in the liposomes during hydration. An example of such is a fatty acid ester having a long hydrocarbon chain sufficient to act as hydrophobic anchor.

Suitable active components can be identified readily by a person skilled in the art and may include for example antiinflammatory and bronchorelaxing drugs as well as antihistamines, cyclooxygenase inhibitors, leukotriene synthesis inhibitors, leukotriene antagonists, phospholipase-A2 (PLA2) inhibitors, platelet aggregating factor (PAF) antagonists and prophylactics of asthma. Antiarrhythmic drugs, tranquilisers, cardiac glycosides, hormones, anti-hypertensive drugs, antidiabetic, antiparisitic and anticancer drugs, sedatives, analgesic drugs, antibiotics, antirheumatic drugs, immunotherapies, antifungal drugs, antihypotension drugs, vaccines, antiviral drugs, proteins, peptides and vitamins, may also be of interest.

Specifically, glucocorticosteroids such as budesonide, dexamethasone, bethamethasone, fluocinolone, flumethasone, triamcinolone acetonide, flunisolide, beclomethasone and 16, 17-acetals of pregnane derivatives and compounds derived therefrom; and .beta.-2 agonists such as terbutaline, salmeterol, salbutamol, formoterol, fenoterol, clenbuterol, procaterol, bitolterol, and broxaterol may be useful in the present invention. The active component may also be a mixture of pharmaceutically active substances; for example a mixture of a glucocortico-steroid with a bronchodilator such as formoterol, salmeterol, terbutaline or salbutamol, may be useful. For the avoidance cf doubt, where a reference to any active component is made herein, said reference is intended to include a reference to pharmaceutically acceptable esters, salts, and hydrates thereof.

Where the active component is a steroid it is preferably a steroid ester.

The active component is preferably a steroid, preferably a steroid which is esterified in the 21-position with a fatty acid of at least 8, for example at least 10 or at least 12 carbon atoms. The fatty acid may have, for example, up to 24 carbon atoms, for example up to 20 carbon atoms or up to 18 carbon atoms. More preferably, the active component is a steroid-21-palmitate, myristate, laurate, caprate, caprylate or stearate. The most preferred active component according to the invention is the compound (22R)-16.alpha.,17.alpha.-butylidenedioxy-6.alpha.,9.alpha.-difluoro-11.be ta.-hydroxy-21-palmitoyloxypregn-4-ene-3,20-dione, i.e., rofleponide palmitate.

Where the active component is an ester it must be hydrolysed to the active principal. Surprisingly, the single phase proliposome powder of the present invention facilitates the necessary hydrolysis in situ, whereas esters in the crystalline state will not be hydrolysed.

Where delivery by inhalation is desired, as much as possible of the proliposome powder of the present invention should consist of particles having a diameter of less than 10 microns, for example 0.01-10 microns or 0.1-6 microns, for example 0.1-5 microns, or agglomerates of said particles. Preferably at least 50% of the powder consists of particles within the desired size range. For example at least 60%, preferably at least 70%, more preferably at least 80% and most preferably at least 90% of the powder consists either of particles within the desired size range or of agglomerates of said particles.

The proliposome powders of the present invention need not contain other ingredients. However pharmaceutical compositions containing the powders of the present invention may also include other pharmaceutically acceptable additives such as pharmaceutically acceptable adjuvents, diluents and carriers. These may be added to the proliposome composition after any micronisation, or before any micronisation provided that the solvent has been completely removed. Any carrier is preferably a crystalline, hydrophilic substance. A preferred carrier is crystalline lactose monohydrate. Other suitable carriers include glucose, fructose, galactose, trehalose, sucrose, maltose, raffinose, maltitol, melezitose, stachyose, lactitol, palatinite, starch, xylitol, mannitol, myoinositol, and the like, and hydrates thereof, and amino acids, for example alanine, and betaine.

The amount of additives present in the formulation may vary over a very wide range. In some circumstances little or no additive may be required, whereas for example it is often preferable to dilute a powder with additive, in order to improve the powder properties for use in an inhaler. In the latter case, for example, at least 50%, for example at least 70% or at least 80% of the formulation may be made up of additives, the remainder being the proliposome powder. The percentage of additives may also be dependant on the potency of the biologically active compound and the optimal amount of powder for inhalation.

Where an additive, for example a carrier is present, the entire composition may be in the form of particles of a size within the respirable particle size range. Alternatively the carrier may comprise coarser particles, of for example mass median diameter greater than 20 microns, or it may comprise agglomerates of the smaller particles, the agglomerates having a mass median diameter of for example greater than 20 microns, so that in either case an ordered mixture of proliposome and carrier is formed.

A further object of the present invention is the provision of a process for the preparation of the proliposome powder of the present invention, i.e. a process which yields the proliposome powder in a single phase.

Accordingly, the present invention also provides a process for the preparation of a proliposome powder for inhalation, comprising dissolving a lipid or mixture of lipids and a lipophilic biologically active component in a solvent, said lipid or mixture of lipids having a phase transition temperature below 37^oC.; obtaining a crystalline solvent matrix and a single lipid phase in its glassy state by freezing the solution, said freezing being carried out at a temperature below the phase transition temperature of the lipid phase; and evaporating the frozen solvent at a temperature below the phase transition temperature of the lipid phase.

Freezing of the solution and solvent evaporation may be effected by conventional methods, for example in a conventional freeze-drier. For example the solution of lipids and biologically active component may be poured onto the shelves of a freeze-drier and the temperature lowered to freeze the solution. Solvent evaporation may then be achieved for example by lowering the pressure in the freeze-drying chamber; the resulting powder may be scraped from the shelves of the chamber and optionally passed through a sieve.

The freeze-dried powder may if necessary be subjected to further processing in order to obtain particles within the respirable particle size range; for example the freeze-dried powder may be micronised to give respirable particles, for example using an air jet mill.

The freezing of the solution of biologically active component and lipids is carried out in a manner which produces a single lipid phase in the frozen solvent matrix. The production of a single lipid phase is controlled by the final temperature and the rate of freezing of the solution; the optimum rate of freezing of any particular solution will be somewhere between the time necessary for crystallisation of the solvent in question and the time necessary for crystallisation of the lipids and active component and may be determined by a person skilled in the art, simply by trial and error. The optimal final temperature should be 10-20^oC. below the glass transition temperature of the lipid phase. For example a powder X-ray method may be used to monitor crystallinity and a differential scanning calorimeter may be used for monitoring the degree of incorporation of biologically active component into the liposomes after hydration.

The solvent must have the capacity to dissolve the lipids and the biologically active component completely since it is essential that all the components are in solution prior to freezing in order to avoid precipitation or phase-separation which will give rise to a powder with more than one phase. In addition the solvent should be toxicologically acceptable, have an appropriate freezing point and preferably a high vapour pressure. The solvent may be for example an organic solvent, for example an alcohol, or a mixture of aqueous and organic solvents. The preferred solvent for use in the present invention is tertiary butanol.

The powder may optionally be agglomerated into small spheres, in order to control the cohesiveness of the powder. The spheres should preferably be not larger than 1 mm in diameter; spheres larger than this may be removed for example by sieving. Any agglomerates should be friable, so that they may easily be deagglomerated for example in a powder inhaler.

The proliposome powder of the present invention is useful for the local or systemic treatment of diseases and may be administered for example via the upper and lower respiratory tract, including by the nasal route. As such the present invention also provides said proliposome powder for use in therapy; the use of the proliposome powder in the manufacture of a medicament for the treatment of diseases via the respiratory tract; and a method for the treatment of a patient in need of therapy, comprising administering to said patient a therapeutically effective amount of the proliposome powder of the present invention.

For example the proliposome powder of the present invention may be used in the treatment of inflammatory diseases in the respiratory tract, for example asthma, rhinitis, alveolitis, bronchiolitis and bronchitis.

Administration to the respiratory tract may be effected for example using a dry powder inhaler or a pressurised aerosol inhaler.

Suitable dry powder inhalers include dose inhalers, for example the single dose inhaler known by the trade mark Monohaler.RTM. and multi-dose inhalers, for example a multi-dose, breath-actuated dry powder inhaler such as the inhaler known by the trade mark Turbuhaler.RTM..

While the proliposome powder of the present invention is particularly adapted for administration by inhalation, it may also be included in formulations adapted for other forms of delivery. For example oral, topical and injectable formulations may be prepared, for use in the treatment of for example inflammatory joint diseases, for example arthritis, skin diseases, and intestinal bowel diseases.

Claim 1 of 70 Claims

1. A pharmaceutical composition comprising a proliposome powder and a crystalline and hydrophilic pharmaceutically acceptable carrier, said proliposome powder comprising discrete particles consisting of a single phase comprising (1) a biologically active component and (2) a lipid or mixture of lipids having a phase transition temperature of below 37^oC.

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