WO2001012160A1 - Microparticles for pulmonary administration - Google Patents

Abstract

The invention concerns a biocompatible microparticle designed to be inhaled comprising at least an active principle and at least a layer coating said active particle which is the outer layer of said microparticle, said outer layer comprising at least a coating agent. The invention is characterised in that said microparticle has a mean diameter ranging between 1 νm and 30 νm, an apparent density ranging between 0.02 g/cm3 and 0.8 g/cm3 and it is obtainable by a method comprising essential steps which consist in bringing together a coating agent and an active principle and introducing a supercritical fluid, under agitation in a closed reactor.

Description

 "Microparticles for pulmonary administration"

The present invention relates to the field of microparticles intended to be administered by the pulmonary route.

A bibliographic study made it possible to demonstrate that a great deal of research relating to this technology has been carried out.

Aerosols for the release of therapeutic agents into the respiratory tract have been described, for example (Adjei, A. and Garren, J. Pharm. Res., 7: 565-569 (1990); and Zanen, P. and Lamm, JWJ Int. J. Pharm., 114: 111-115 (1995)). The respiratory tract includes the upper respiratory tract which includes the larynx and the oropharynx, and the lower respiratory tract including the trachea which continues in bifurcations: the bronchi and bronchioles. The terminal bronchioles are then divided into respiratory bronchioles which lead to the ultimate zone of the respiratory system, the pulmonary alveoli also called the deep lung (Gonda, I. "Aerosols for delivery of therapeutic and diagnostic agents to the respiratory tract," in Critical Reviews in Therapeutic Drug Carrier Systems, 6: 273-313 (1990)). The deep lung or the alveoli are the main target of therapeutic inhalation aerosols intended for the systemic route. Aerosols intended for inhalation have already been used for the treatment of local pulmonary disorders such as asthma and cystic fibrosis (Anderson et al., Am. Rev. Respir. Dis., 140: 1317-1324 (1989)) . In addition, they can be used for the systemic release of peptides and proteins (Patton and Platz, Advanced Drug Delivery Reviews, 8: 179-196 (1992)). However, a certain number of difficulties are encountered when it is desired to apply the drug release by the pulmonary route to the release of macromolecules. Among these difficulties are the denaturation of the protein during nebulization, a significant loss of the rate of drugs inhaled in the oropharynx (which often exceeds 80%), poor control of the deposition zone, poor reproducibility therapeutic results due to variations in respiratory models, too rapid absorption of drugs generating local toxic effects, and phagocytosis by macrophages of the lung.

The human lung can quickly eliminate or degrade hydrolysable products deposited in the form of aerosols, this phenomenon generally takes place over a period of between a few minutes and a few hours. In the upper pulmonary tract, the ciliated epithelium contributes to the “mucociliary escalator” phenomenon by which particles are entrained from the pulmonary tract to the mouth (Pavia, D. “Lung Mucociliary Clearance,” in Aérosols and the Lung: Clinical and Experimental Aspects, Clarke, SW and Pavia, D., Eds., Butterworths, London, 1984.; Anderson et al., Am. Rev. Respir. Dis., 140: 1317-1324 (1989)). In the deep lung, alveolar macrophages are able to phagocytose particles immediately after their deposition. Local and systemic inhalation therapies generally allow a controlled and relatively slow release of the active ingredient (Gonda, I., “Physico-chemical principles in aerosol delivery,” in: Topics in Pharmaceutical Sciences 1991, DJA Crommelin and KK Midha, Eds. , Stuttgart: Medpharm Scientific Publishers, pp. 95-117 (1992)). The slow release of the therapeutic aerosol can prolong the residence time of the drug administered in the pulmonary tract or in the acini and decrease the rate of entry of the drugs into the blood stream. Thus patient tolerance is increased by reducing the frequency of administration (Langer, R., Science, 249: 1527-1533 (1990); and Gonda, I. "Aerosols for delivery of therapeutic and diagnostic agents to the respiratory tract, In Critical Reviews in Therapeutic Drug Carrier Systems 6: 273-313 (1990)).

Among the drawbacks of dry powder formulations is the fact that powders of ultrafine particles have generally poor flow and nebulization properties, leading to aerosol fractions which are admitted into the respiratory system relatively slowly, these fractions of the inhaled aerosol are generally deposited in the mouth and throat (Gonda, I., in Topics in Pharmaceutical Sciences 1991, D. Crommelin and K. Midha, Editors, Stuttgart: Medpharm Scientific Publishers, 95-117 (1992)).

The main problem encountered with most aerosols is the particle aggregation generated by inter-particle interactions such as hydrophobic, electrostatic and capillary interactions. Effective therapy by inhalation of dry powder for both immediate and sustained release of therapeutic agents, both locally and systemically, requires the use of a powder with minimal aggregation which avoids or less to suspend the natural clearance mechanisms of the lung until the active ingredient is released. There is currently a demand for improved inhalation aerosols for the pulmonary release of therapeutic agents. Likewise there is currently a need for drug carriers which are capable of releasing the drug in an effective amount into the pulmonary tract or into the alveolar areas of the lungs. In addition, there is also a need for drug carriers which can be used as aerosols for inhalation which are biodegradable and which allow the drugs to be released in a controlled manner into the pulmonary tract and the alveolar zone of the lungs, likewise. There is a demand for particles for drug delivery to the lung which have improved nebulizing properties.

This research tends to show that it is difficult to prepare microparticles which meet the criteria imposed by their applications under effective conditions. In order to be sufficiently effective, these microparticles must not be damaged during administration, during their passage in nebulized form. The bioavailability of these microparticles must reach a sufficiently high value, or the bioavailability of the microparticles of the prior art generally does not exceed 50%, because of a low rate of deposition of the microparticles in the pulmonary alveolar regions. In addition, in order to maintain their effectiveness during pulmonary administration, the microparticles, once deposited in the alveoli, must be sufficiently stable in the mucosa of the surface of these alveoli.

Thus it may prove to be advantageous to prepare microparticles for immediate or delayed release, locally or systemically, however these microparticles generally have an outer layer whose thickness relative to the diameter of said particle is not negligible.

The microparticles according to the invention consist of a core containing the active material coated with a layer of coating agent deposited by the technique of supercritical fluid. This particular structure distinguishes them from the microparticles of the prior art which are matrix microspheres obtained by emulsion-solvent evaporation techniques, solvent extraction by aqueous phases or nebulization-drying of organic solution.

Consequently, the present invention relates to biocompatible microparticles intended to be inhaled comprising at least one active principle and at least one layer coating this active principle which is the outer layer of said microparticles, said outer layer containing at least one coating agent, said microparticles having an average diameter between 1 μm and 30 μm, an apparent density between 0.02 g / cm ³ and 0.8 g / cm ³ , and being capable of being obtained according to a process comprising the essential steps which are the setting in the presence of a coating agent with an active principle and the introduction of a supercritical fluid, with stirring in a closed reactor. These microparticles do not agglomerate when administered, and may possibly allow a prolonged release of the active principle. The microparticles according to the invention have a bioavailability greater than 60% and preferably greater than 80% thanks to an improvement in the rate of deposition of the particles in the alveolar pulmonary zones.

It has thus been demonstrated that the implementation of a process for preparing microparticles by a technique called supercritical fluid using, as coating agent, biocompatible materials judiciously chosen makes it possible to obtain microparticles of size controlled and which have a surface condition such that said microparticles do not agglomerate and are deposited in the alveolar pulmonary zones.

The biocompatible microparticles intended for inhalation according to the invention have an external layer comprising a coating agent which prevents the aggregation of these particles between them. The coverage rate of the surface of the particles is at least greater than 50%, preferably greater than 70%, more preferably still greater than 85%. The quality of this coating is essentially due to the technique of supercritical fluid.

Said method comprises two essential steps which are the placing in the presence of a coating agent with an active principle and the introduction of a supercritical fluid in order to ensure the coacervation of the coating agent.

It is clear from the following description, that these two steps are not necessarily carried out in the order announced.

The first process for preparing the microparticles according to the invention differs from the second process in that the coating agent is at no time in solution in the fluid in the liquid or supercritical state.

In fact, a first implementation of the method according to the invention comprises the following steps: suspending an active principle in a solution of at least one substantially polar coating agent in an organic solvent, said active principle being insoluble in the organic solvent, said substantially polar coating agent being insoluble in a fluid in the supercritical state, said organic solvent being soluble in a fluid in the supercritical state,

- bringing the suspension into contact with a fluid in the supercritical state, so as to desolvate in a controlled manner the substantially polar coating agent and ensure its coacervation,

- substantially extract the solvent by means of a fluid in the supercritical state and evacuate the supercritical fluid / solvent mixture, - recover the microparticles.

The fluid used for the implementation of this first process is preferably liquid CO ₂ or in the supercritical state. The organic solvent used for the implementation of this first process is generally chosen from the group consisting of ketones, alcohols and esters.

The supercritical fluid is brought into contact with the suspension of active principle containing the coating agent in solution is carried out by introduction of the supercritical fluid into an autoclave already containing the suspension. When the employee supercritical fluid is CO ₂ can be used CO ₂ in liquid form or directly to the CO ₂ in the supercritical state.

According to another variant, the suspension can also be brought into contact with liquid CO ₂ which will then pass to the supercritical state by increasing the pressure and / or the temperature in the autoclave in order to extract the solvent.

When choosing to use the liquid CO ₂ variant, the temperature is preferably chosen between 20 and 30 ° C and the pressure between 80 and 150 10 ⁵ Pa. When the supercritical CO ₂ variant is used, the temperature is generally chosen between 35 and 60 ° C, preferably between 35 and 50 ° C, and the pressure between 80 and 250 10 ⁵ Pa, preferably between 100 and 220 10 ⁵ Pa. The mass of organic solvent introduced into the autoclave represents at least 3%, preferably between 3.5% and 25% of the mass of the supercritical fluid or liquid used to cause the desolvation of the coating agent. The microparticles obtained by the implementation of this first process have an outer layer almost free of solvent, the amount of solvent in the outer layer is indeed less than 500 ppm.

The coating agents which can be used for the implementation of this first process are more particularly:

- biodegradable (co) polymers of α-hydroxycarboxylic acids, in particular homopolymers and copolymers of lactic and glycolic acids, and more particularly PLA (Poly-L-lactide) and PLGA (Poly-Lactic-co-Glycolic-Acid) ,

- amphiphilic block polymers of the poly lactic acid-polyethylene oxide type, - the biocompatible polymers of the polyethylene glycol, polyethylene oxide type,

- polyanhydrides, poly (ortho esters), poly-ε-caprolactones and their derivatives,

- poly (β-hydroxybutyrate), poly (hydroxyvalerate) and poly (β-hydroxybutyrate-hydroxyvalerate) copolymers,

- polyic acid,

- polyphosphazenes,

- block copolymers of polyethylene oxide-propylene polyoxide type, - poly (amino acids),

- polysaccharides, - phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with fatty acid chains from C12 to C18 (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, diphosphatidylcholines with fatty acid chains from C12 to C18 (DLPC, DMPC , DPPC, DSPC), diphosphatidyl ethanolamines with C12 to C18 fatty acid chains (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with C12 to C18 chains (DLPS, DMPS, DPPS, DSPS), and mixtures which would contain the phospholipids mentioned,

- fatty acid esters such as glyceryl stearates, glyceryl laurate, cetyl palmitate, or mixtures which contain these compounds,

- mixtures which would contain the compounds mentioned above.

The implementation of the second method according to the invention consists in suspending an active principle in a supercritical fluid containing at least one coating agent dissolved in it, then in modifying the pressure and / or temperature conditions of the medium to ensure the coacervation of the particles, by precipitation of the coating agent around the particles of active principle, that is to say ensuring the coacervation of the particles by physico-chemical modification of the medium.

The coating agents which can be used for the implementation of this second process are more particularly:

- phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with fatty acid chains from C12 to C18 (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, diphosphatidylcholines with fatty acid chains from C12 to C18 (DLPC, DMPC , DPPC, DSPC), diphosphatidyl ethanolamines with C12 to C18 fatty acid chains (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with C12 to C18 chains (DLPS, DMPS, DPPS, DSPS), and mixtures which would contain the phospholipids mentioned,

- mono, di, triglycerides whose fatty acid chains go from C4 to C22, and mixtures containing them, - mixtures of glycerides and polyethylene glycol esters,

- cholesterol,

- fatty acid esters such as glyceryl stearates, glyceryl laurate, cetyl palmitate, - mixtures which would contain the compounds mentioned above.

Biodegradable or bioerodible polymers soluble in a supercritical fluid can also be used in this second process.

The coacervation (or aggregation) of a coating agent is caused by physicochemical modification of a medium containing an active substance in suspension in a solution of coating agent in a solvent, said solvent being a supercritical fluid.

The supercritical fluid preferentially used is supercritical CO ₂ (CO ₂ SC), the initial operating conditions typical of this second process will be approximately 31 to 80 ° C. and the pressures from 75 to 250 10 ⁵ Pa, although the higher values of either or both of the two parameters may be used, provided of course that the higher values have no harmful or degrading effect on the active ingredient during coating, nor on the coating agents. Furthermore, one can also choose other fluids commonly used as supercritical fluids. These include ethane, which becomes supercritical above 32 ° C and 48 10 ⁵ Pa, nitrogen dioxide whose critical point is 36 ° C and 72 10 ⁵ Pa, propane whose critical point is of 96 ° C and 42 10 ⁵ Pa, trifluoromethane whose critical point is 26 ° C and 47 10 ⁵ Pa, and chlorotrifluoromethane whose critical point is 29 ° C and 39 10 ⁵ Pa.

This second method involves suspending, in a closed and stirred autoclave, an active principle which is not soluble in the supercritical fluid, said supercritical fluid containing a coating agent which is in the solute state. The pressure and / or the temperature are then modified so as to reduce the solubility of the coating agent in the fluid. Thus, the affinity of the coating agent for the active principle increases so that this coating is adsorbed around the active principle. Once this coating agent is deposited on the active ingredient, the autoclave is depressurized and the microparticles are recovered.

To implement this second process, the active ingredient to be coated and the coating agent (s) are placed in an autoclave equipped with an agitator, then the system is pressurized by introducing a fluid into the autoclave under supercritical conditions. Then, the temperature and / or pressure inside the autoclave is modified in a controlled and regulated manner so as to gradually reduce the solubility of the coating agent (s). When the solubility of this or these coating agents in the supercritical fluid decreases, it (s) precipitates (s) and the affinity of these agents for the surface of the active principle leads to their adsorption on this surface. A variant of this process consists in placing the coating agent in the autoclave before introducing the active principle therein or by simultaneously introducing therein the active principle and a fluid capable of passing to the supercritical state. Pressurizing the autoclave to produce a state of supercritical fluid will then cause the coating agent to dissolve in said supercritical fluid.

According to another variant of the process, the active principle is placed in an autoclave equipped with an agitator, the coating agent is placed in a second autoclave equipped with an agitator into which is introduced the fluid capable of passing to the supercritical state . The coating agent is brought into the solute state by increasing the temperature and the pressure, then is transferred to the autoclave where the active principle is located.

This ensures the deposition of the coating agent so that this agent follows the surface of the active ingredient. The active principle can be in the form of a liquid which can thus form an emulsion in the supercritical fluid, of preformed solid particles, and in particular of microparticles possibly already coated for example with mono- or disaccharides. The stirring speeds can vary between 150 and 700 rpm for solid particles and between 600 and 1000 rpm when the active principle is a liquid. Such stirring ensures the suspension of the active principle in the supercritical fluid when the latter is introduced. The supercritical conditions are ensured by a modification of the temperature and / or the pressure inside the autoclave. Thus, when the supercritical fluid is CO ₂ , the temperature of the autoclave is between 35 and 80 ° C, preferably between 35 and 50 ° C, and the pressure is between 100 and 250 10 ⁵ Pa, and preferably between 180 and 220 10 ⁵ Pa.

When the supercritical fluid is ethane, the temperature of the autoclave is between 35 and 80 ° C, preferably between 35 and 50 ° C, and the pressure is between 50 and 200 10 ⁵ Pa, and preferably between 50 and 150 10 ⁵ Pa.

When the fluid is propane, the temperature of the autoclave is between 45 and 80 ° C, preferably between 55 and 65 ° C, and the pressure is between 40 and 150 10 ⁵ Pa.

The coating agent is introduced into the autoclave at the same time as the supercritical fluid or else before the introduction into the autoclave of the supercritical fluid. In all cases to ensure good solubilization of the coating agent in the supercritical fluid, the system is kept in equilibrium with stirring, the appropriate concentration of active principle and coating agent is established as a function of the desired microparticles and the this balance under stirring for one hour. The temperature and the pressure are then modulated at a speed slow enough to completely transfer the coating agent (s) from the supercritical fluid to the surface of the active principle and the system is depressurized to isolate the microparticles which are removed from the autoclave. The microparticles according to the present invention have a diameter between 1 μm and 30 μm, preferably between 1 μm and 15 μm, and even more preferably between 2 μm and 10 μm and a bulk density between 0.02 g / cm ³ and 0.8 g / cm ³ and preferably between 0.05 g / cm ³ and 0.4 g / cm ³ .

The active ingredient / coating agent mass ratio of these microparticles is preferably between 95/5 and 5/95. In the case of controlled release microparticles, the amount of active principle is low compared to the coating agent, the mass ratio of active principle / coating agent is then between 5/95 and 20/80, on the contrary in the case where the coating is intended to stabilize the particle, in particular when the microparticle is in immediate release, the mass ratio active ingredient / coating agent is generally between 95/5 and 70/30 and preferably between 95/5 and 80/20.

The coating agents for microparticles according to the invention advantageously belong to the following families:

- biodegradable (co) polymers of hydroxycarboxylic acids, in particular homopolymers and copolymers of lactic and glycolic acids, and more particularly PLA (Poly-L-lactide) and PLGA (Poly-Lactic-co-Glycolic-Acid),

- mono, di, triglycerides with fatty acid chains ranging from C4 to C22, and mixtures containing them, - mixtures of glycerides and polyethylene glycol esters,

- cholesterol,

- amphiphilic block polymers of poly lactic acid-polyethylene oxide type,

- biocompatible polymers of polyethylene glycol, polyethylene oxide type,

- polyanhydrides, poly (ortho esters), poly-ε-caprolactones and their derivatives,

- poly (β-hydroxybutyrate), poly (hydroxyvalerate) and poly (β-hydroxybutyrate-hydroxyvalerate) copolymers, - polyicic acid,

- polyphosphazenes, - block copolymers of the polyethylene oxide-propylene polyoxide type,

- poly (amino acids),

- polysaccharides, - phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with fatty acid chains from C12 to C18 (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, diphosphatidylcholines with fatty acid chains from C12 to C18 (DLPC, DMPC, DPPC, DSPC), disphosphatidyl etanolamines with C12 to C18 fatty acid chains (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with C12 to C18 chains (DLPS, DMPS, DPPS, DSPS ), and the mixtures which would contain the phospholipids mentioned,

- fatty acid esters such as glyceryl stearates, glyceryl laurate, cetyl palmitate, - mixtures of at least two compounds chosen from the fatty derivatives mentioned above and such that they have suitable solubilities . Depending on the coating agent, the solubility in supercritical fluids, and the coating conditions, it will thus be possible to implement the first or the second method described above. Said active principle can be in the form of a liquid, a solid powder or an inert porous solid particle comprising on its surface an active principle.

The active ingredients used are chosen from a wide variety of therapeutic and prophylactic compounds. They are more particularly chosen from proteins and peptides such as insulin, calcitonin, analogs of the hormone LH-RH, polysaccharides such as heparin, anti-asthmatics such as budesonide, dipropionate of beclometasone and its active metabolite

Beclometasone 17-monopropionate, beta-estradiol hormones, testosterone, bronchodilators such as albuterol, cytotoxic agents, corticosteroids, antigens, DNA fragments FIG. 1 is a photograph by electron microscopy of a microparticle obtained according to example 2.

FIG. 2 is a photograph by electron microscopy of microparticles obtained according to example 3. The examples which follow illustrate the invention without limiting its scope.

Example 1

This example illustrates the first method of implementing the invention.

80 mg of PLGA are dissolved in 80 ml of ethyl acetate. 400 mg of micronized insulin is suspended in the solution thus obtained at 250 rpm and the suspension is placed in an autoclave of capacity 1.0 I. Firstly, the pressure is increased to 100 10 ⁵

Pa by introducing the liquid CO ₂ while remaining at a constant temperature of 28 ° C.

The CO ₂ in the liquid state mixes with the suspension thus making it possible to wet the insulin, and also making it possible to ensure the progressive precipitation of the coating agent.

The CO ₂ is passed to the supercritical state by gradually increasing the pressure to 150 10 ⁵ Pa. The temperature is jointly maintained at 40 ° C. Thus, ethyl acetate is extracted. These conditions are maintained for 15 minutes, then the CO ₂ / ethyl acetate mixture is removed by decompressing up to 75 × 10 ⁵ Pa in a separator while maintaining the temperature at a value greater than 35 ° C.

The ethyl acetate is recovered in this separator and the CO ₂ returns to a tank.

The ethyl acetate is recovered and the successive cycles of introduction of liquid CO ₂ , transition to the supercritical state and evacuation of CO ₂ + ethyl acetate are repeated until complete elimination of the acetate ethyl. The decompression is necessarily done by the gas phase so as not to reconcentrate coating agent in the remaining ethyl acetate. After the decompression phase, the operation can be repeated several times by reintroducing CO _{2 in} order to find a pressure of 150 10 ⁵ Pa and a temperature of 40 ° C. Finally, we depressurize and extract the CO ₂ + solvent mixture and then reintroduce fresh CO ₂ which is brought to the supercritical state in order to completely extract the solvent. The temperature in this case is generally between 35 and 45 ° C. and the pressure between 180 and 220 × 10 ⁵ Pa. This gives 250 mg of non-aggregated microparticles with an average size of 3 μm and comprising 80 to 90% by weight of insulin, which have improved nebulizing properties.

Example 2

This example illustrates the second method of implementing the invention.

In a pressurizable and stirred autoclave of 0.3 I having a porous insert is placed 150 mg of bovine serum albumin (BSA) prepared by atomisation, and 600 mg Gelucire ^® 50/02 form of chips.

CO ₂ is introduced into the autoclave, up to a pressure of 95 10 ⁵ Pa at a temperature of 25 ° C. The CO ₂ is then in the liquid state.

Stirring is started, and fixed at 460 rpm. Then the autoclave is heated to 50 ° C. The pressure is then 220 10 ⁵ Pa; CO ₂ is in the supercritical state and its density is 0.805 g / cm ³ .

The system is allowed to balance for one hour. Is then reduced the temperature of the autoclave at 19 ° C for 38 minutes duration, starting 50 ^C C. The slurry phase in supercritical CO ₂ is thus transformed into a mixture of CO ₂ gas and liquid, the particles active ingredient being suspended in liquid CO ₂ . In depressurizing then to the atmospheric pressure is obtained BSA coated microparticles Gelucire ^® 50/02.

Thus obtaining 250 mg of non-aggregated particles of BSA mean diameter of 10 microns coated with a layer of Gelucire ^® 50/02, the weight ratio active ingredient / coating agent is about 30/70. These microparticles have improved nebulization properties.

Example 3

This example illustrates the second method of implementing the invention.

In a pressurizable and stirred autoclave of 1 I, 300 mg is placed ovalbumin (OVA) prepared by atomisation, and 300 mg Gelucire ^®

50/13 in the form of chips. CO ₂ is introduced into the autoclave, up to a pressure of 109

10 ⁵ Pa for a temperature of 23 ° C. The CO is then in the liquid state.

The stirring is started, and fixed at 340 rpm. Then the autoclave is heated to 35 ° C. The pressure is then 180 10 ⁵ Pa, the CO ₂ is in the supercritical state. The system is allowed to balance for one hour. The temperature of the autoclave is then lowered to 16 ° C. for a period of 43 minutes starting from 35 ° C. The phase suspended in supercritical CO ₂ is thus transformed into a mixture of liquid and gaseous CO ₂ .

Then depressurizing to atmospheric pressure, OVA microparticles coated with Gélucire ^® 50/13 are obtained.

Thus obtaining 300 mg of non-aggregated particles of OVA with an average diameter equal to 9 microns coated with a layer of Gelucire ^® 50/13, which have improved fogging properties. Example 4

This example illustrates the second method of implementing the invention. 300 mg of beclomethasone dipropionate in the form of a loose powder prepared by atomization and 50 mg of Dilauroyl Phosphatidyl Glycerol (DLPG) are placed in a 0.3 I pressurizable autoclave fitted with a porous insert.

CO ₂ is introduced into the autoclave, up to a pressure of 98 10 ⁵ Pa for a temperature of 23 ° C. The CO ₂ is then in the liquid state.

Agitation is started, at 460 rpm. Then the autoclave is heated to 60 ° C. The pressure is then 300 10 ⁵ Pa, the CO ₂ is in the supercritical state and its density is 0.830 g / cm ³ .

The system is allowed to balance for one hour. The temperature of the autoclave is then lowered to 20 ° C for a period of 65 minutes. The phase in suspension in supercritical CO ₂ thus transforms into a mixture of liquid and gaseous CO ₂ , the particles of active principle being in suspension in liquid CO ₂ . By then depressurizing to atmospheric pressure, microparticles of beclomethasone dipropionate coated with DLPG are obtained.

200 mg of non-aggregated beclomethasone dipropionate particles with a diameter of 5 μm are thus obtained, coated with a layer of

DLPG, whose active ingredient / coating agent mass ratio is approximately 90/10. These microparticles have improved nebulization properties.

Claims

1. Biocompatible microparticle intended to be inhaled comprising at least one active principle and at least one layer coating this active principle which is the outer layer of said microparticle, said outer layer containing at least one coating agent, characterized in that said microparticle mean diameter between 1 μm and 30 μm, an apparent density between 0.02 g / cm ³ and 0.8 g / cm ³ and that it is capable of being obtained according to a process comprising the essential steps which are the bringing together a coating agent with an active principle and the introduction of a supercritical fluid, with stirring in a closed reactor. 2. Microparticles according to claim 1, characterized in that they have an average diameter between 1 μm and 15 μm, and even more preferably between 2 μm and 10 μm, an apparent density between 0.05 g / cm ³ and 0.4 g / cm ³ , and in that the active ingredient / coating agent mass ratio of this particle is between 95/5 and 5/95. 3. Microparticle according to claim 1 or 2 capable of being obtained by a process comprising the following steps: suspending an active principle in a solution of at least one substantially polar coating agent in an organic solvent, said active principle being insoluble in the organic solvent, said substantially polar coating agent being insoluble in a fluid in the supercritical state, said organic solvent being soluble in a fluid in the supercritical state, - bringing the suspension into contact with a fluid in the supercritical state, so as to desolvate in a controlled manner the substantially polar coating agent and ensure its coacervation, - substantially extract the solvent by means of a fluid in the supercritical state and evacuate the SC fluid / solvent mixture, - recover the microparticles. 4. Microparticle according to claim 1 or 2, capable of being obtained by a process which consists in suspending an active principle in a supercritical fluid containing at least one coating agent dissolved in it then in ensuring the coacervation of the particles, by physico-chemical modification of the medium. 5. Microparticle according to claim 3, characterized in that the coating agent is chosen from the group formed by - biodegradable (co) polymers of α-hydroxycarboxylic acids, in particular homopolymers and copolymers of lactic and glycolic acids, and more particularly PLA (Poly-L-lactide) and PLGA (Poly-Lactic-co-Glycolic-Acid) , - amphiphilic block polymers of poly lactic acid-polyethylene oxide type, - biocompatible polymers of polyethylene glycol, polyethylene oxide type, - polyanhydrides, poly (ortho esters), poly-ε-caprolactones and their derivatives, - poly (β-hydroxybutyrate), poly (hydroxyvalerate) and poly (β-hydroxybutyrate-hydroxyvalerate) copolymers, - polyic acid, - polyphosphazenes, - block copolymers of the polyethylene oxide-propylene polyoxide type, - poly (amino acids), - polysaccharides, - phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with fatty acid chains from C12 to C18 (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, diphosphatidylcholines with fatty acid chains from C12 to C18 (DLPC, DMPC , DPPC, DSPC), diphosphatidyl ethanolamines with C12 to C18 fatty acid chains (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with C12 to C18 chains (DLPS, DMPS, DPPS, DSPS), and mixtures which would contain the phospholipids mentioned, - fatty acid esters such as glyceryl stearates, glyceryl laurate, cetyl palmitate, or mixtures which contain these compounds, - mixtures which would contain the compounds mentioned above. 6. Microparticle according to claim 4, characterized in that the coating agent is chosen from the group formed by - phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with fatty acid chains from C12 to C18 (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, diphosphatidylcholines with fatty acid chains from C12 to C18 (DLPC, DMPC , DPPC, DSPC), diphosphatidyl ethanolamines with C12 to C18 fatty acid chains (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with C12 to C18 chains (DLPS, DMPS, DPPS, DSPS), and mixtures which would contain the phospholipids mentioned, - mono, di, triglycerides whose fatty acid chains go from C4 to C22, and mixtures containing them, - mixtures of glycerides and polyethylene glycol esters, - cholesterol, - fatty acid esters such as glyceryl stearates, glyceryl laurate, cetyl palmitate, - biodegradable or bioerodible polymers soluble in a supercritical fluid, - mixtures which would contain the compounds mentioned above. 7. Microparticle according to one of claims 1 to 6, characterized in that the active principle is chosen from the group formed by proteins and peptides such as insulin, calcitonin, analogues of the hormone LH-RH , polysaccharides such as heparin, anti-asthmatics such as budesonide, beclometasone dipropionate and its active metabolite beclometasone 17-monopropionate, beta-estradiol hormones, testosterone, bronchodilators such as albuterol, agents cytotoxics, corticosteroids, antigens, DNA fragments. 8. Microparticle according to claim 2 characterized in that the microparticle is immediate release and that the mass ratio active ingredient / coating agent of this particle is between 95/5 and 80/20. 9. A method of preparing microparticles intended to be inhaled and comprising the following steps: suspending an active principle in a solution of at least one substantially polar coating agent in an organic solvent, said active principle being insoluble in the organic solvent, said substantially polar coating agent being insoluble in a fluid in the supercritical state, said organic solvent being soluble in a fluid in the supercritical state, - bringing the suspension into contact with a fluid in the supercritical state, so as to desolvate in a controlled manner the substantially polar coating agent and ensure its coacervation, - substantially extract the solvent by means of a fluid in the supercritical state and evacuate the supercritical fluid / solvent mixture, - recover the microparticles. 10. A process for the preparation of microparticles intended to be inhaled which consists in placing, with stirring in a closed reactor, an active principle in suspension in a supercritical fluid containing at least one coating agent dissolved in it and then ensuring the coacervation of the particles , by physico-chemical modification of the medium.