CA2380883A1 - 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 µm and 30 µm, an apparent density ranging between 0.02 g/cm?3¿ and 0.8 g/cm?3¿ 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 s intended for administration by the pulmonary route.
A bibliographic study made it possible to highlight that a lot of research has been done on this technology.
Aerosols for the release of therapeutic agents in respiratory tracts have been described for example (Adjei, A. and Garren, J.
1o Pharm. Res., 7: 565-569 (1990); and Zanen, P. and Lamm, JWJ Int. J.
Pharm., 114: 111-115 (1995)). The airways include upper respiratory tract which includes the larynx and oropharynx, and the lower respiratory tract including the trachea which continues in bifurcations: the bronchi and bronchioles. Terminal bronchioles 1s then divide into respiratory bronchioles which lead to the area the respiratory system, the so-called pulmonary alveoli the deep lung (Gouda, 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)). Lung 2o deep or the alveoli are the main target of aerosols therapeutic by inhalation intended for the systemic route. Aerosols intended to be inhaled have already been used for the treatment of disorders local lungs such as asthma and cystic fibrosis (Anderson et al., Am. Rev. Breathe. Dis., 140: 1317-1324 (1989)). In addition, they can be 2s used for systemic release of peptides and proteins (Patton and Platz, Advanced Drug Delivery Reviews, 8: 179-196 (1992)). However we encounter a certain number of difficulties when we want to apply the pulmonary drug release upon release of macromolecules. Among these difficulties is the denaturation of the 3o protein during nebulization, a significant loss of the rate of drugs inhaled into the oropharynx (which often exceeds 80%), a poor control of the deposition area, poor reproducibility WO 01/12160

2 PCT / FR00 / 02282 therapeutic results due to variations in respiratory patterns, too rapid absorption of drugs generating toxic effects local, and phagocytosis by macrophages of the lung.
The human lung can quickly eliminate or degrade s hydrolysable products deposited in the form of aerosols, this phenomenon occurs generally takes place over a period of a few minutes and a few hours. In the upper pulmonary tract, the epithelium ciliate contributes to the “mucociliary escalator” phenomenon by which particles are entrained from the lungs to the mouth lo (Pavia, D. "Lung Mucociliary Clearance," in Aerosols and the Lung Clinicat and Experimental Aspects, Clarke, SW and Pavia, D., Eds., Butterworths, London, 1984.; Anderson et al., Am. Rev. Breathe. Say, 140 1317-1324 (1989)). In the deep lung the alveolar macrophages are able to phagocyte the particles immediately after their deposition.
ls Local and systemic inhalation therapies allow generally a controlled and relatively slow release of the principle active (Gonds, 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 20 slow release of the therapeutic aerosol can prolong the time of drug stay in the pulmonary tract or acini and decrease the rate of entry of drugs into the blood stream.
Thus patient tolerance is increased by reducing the frequency administrations (Langer, R., Science, 249: 1527-1533 (1990); and 2s Gonds, 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 that formulations of so dry powders, there are the fact that the powders of ultra-fines have flow and fogging properties generally bad, leading to aerosol fractions WO 01/12160

3 PCT / FR00 / 02282 which are admitted to the respiratory system relatively slow, these fractions of the inhaled aerosol generally settle in the mouth and throat (Gonds, I., in Topics in Pharmaceutical Sciences 1991, D. Crommelin and K. Midha, Editors, Stuttgart: Medpharm s Scientific Publishers, 95-117 (1992)).
The main problem with most aerosols is particle aggregation generated by inter-particle interactions such as than hydrophobic, electrostatic and capillary interactions. A
effective dry powder inhalation therapy for both release 1o immediate and sustained therapeutic agents, both at local level and systemic, requires the use of a powder with a minimum aggregation which makes it possible to avoid or at least suspend the natural clearance mechanisms of the lung until the active ingredient is released.
1s There is currently a demand for aerosols for inhalation enhancers for the pulmonary release of therapeutic agents. Of even there is currently a need for drug carriers which are capable of releasing the effective amount of the drug into the pathways pulmonary or in the alveolar areas of the lungs.
2o In addition, there is also a need for drug carriers which can be used as aerosols for inhalation which are biodegradable and release drugs in a way controlled in the pulmonary tract and the alveolar zone of the lungs, similarly there is a demand for particles for the release of 2s drug in the pulmonary which have properties of improved nebulization.
This research suggests that it is difficult to prepare microparticles that meet the criteria imposed by their applications under effective conditions.
n / a In order to be sufficiently effective, these microparticles do not must not be damaged during administration, when passage in nebulized form. The bioavailability of these microparticles WO 01/12160 q. PCT / FR00 / 02282 must reach a sufficiently high value, and the bioavailability of microparticles of the prior art generally does not exceed 50%, at cause of low deposition rate of microparticles in regions alveolar lungs.
s In addition, in order to maintain their effectiveness during administration pulmonary, the microparticles once deposited in the alveoli, must be sufficiently stable in the mucous membrane of the overtace of these alveoli.
So it can be interesting to prepare microparticles to 1o immediate or delayed release, locally or systemically, however these microparticles generally have a layer external whose thickness relative to the diameter of said particle is not negligible.
The microparticles according to the invention consist of a heart 1s containing the active ingredient coated with a layer of coating agent deposited by the supercritical fluid technique. This structure distinguishes them from the microparticles of the prior art which are matrix microspheres obtained by emulsion techniques solvent evaporation, solvent extraction by aqueous phases 20 or nebulization-drying of organic solution.
The present invention therefore relates to microparticles.
biocompatible intended to be inhaled comprising at least one active ingredient and at least one layer coating this active ingredient which is the outer layer of said microparticles, said outer layer containing 2s at least one coating agent, said microparticles having a average diameter between 1 Nm and 30 Nm, an apparent density between 0.02 g / cm3 and 0.8 g / cm3, and being likely to be obtained according to a process comprising the essential steps which are the placing in the presence of a coating agent with an active principle and 30 introduction of a supercritical fluid, with stirring into a reactor closed.

WO 01/12160 g PCT / FR00 / 02282 These microparticles do not agglomerate when they are administered, and may possibly allow release active ingredient. The microparticles according to the invention have a bioavailability greater than 60% and preferably s greater than 80% thanks to an improvement in the deposition rate of particles in the alveolar pulmonary areas.
It has thus been demonstrated that the implementation of a process for preparing microparticles by a technique called the fluid supercritical using, as a coating agent, materials 1o judiciously chosen biocompatible products microparticles of controlled size and which have a surface state such that said microparticles do not agglomerate and deposit in alveolar pulmonary areas.
Biocompatible microparticles intended for inhalation according to 1s the invention have an outer layer comprising a coating agent which prevents the aggregation of these particles between them. The rate of coverage of the particle surface is at least more than 50%, preferably greater than 70%, more preferably still greater than 85%. The quality of this coating is mainly due to the technique 2o of the supercritical fluid.
Said method comprises two essential steps which are the setting 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 stages do not 2s are not necessarily carried out in the order announced.
The first process for preparing 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 state or so supercritical.
Indeed, a first implementation of the method according to the invention includes the following steps - suspend an active ingredient in a solution of at least at least one substantially polar coating agent in a solvent organic, said active principle being insoluble in organic solvent, s said substantially polar coating agent being insoluble in a fluid in the supercritical state, said organic solvent being soluble in a fluid in the state supercritical, - contact the suspension with a fluid in the state 1o supercritical, so as to desolvate in a controlled manner the agent coating substantially polar and ensuring its coacervation, - substantially extract the solvent using a the supercritical state and evacuate the fluid mixture supercritical / solvent, 1s - recover the microparticles.
The fluid used for the implementation of this first process is preferably C02 liquid 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, 20 alcohols and esters.
Bringing the supercritical fluid into contact with the suspension of active ingredient containing the coating agent in solution is carried out by introduction of the supercritical fluid into an autoclave already containing the suspension.
2s When the supercritical fluid used is COZ, it is possible to use C02 in liquid form or directly C02 in the supercritical state.
According to another variant, one can also put the suspension in contact with liquid C02 which will then pass to the supercritical state by pressure and / or temperature increase in the autoclave so 3o to extract the solvent.
When choosing to use the liquid C02 variant, the temperature is preferably chosen between 20 and 30 ° C and the pressure between 80 and WO 01/12160 ~ PCT / FR00 / 02282 105 Pa. When the supercritical variant C02 is used, we choose generally the temperature between 35 and 60 ° C, preferably between 35 and 50 ° C, and the pressure between 80 and 250 105 Pa, preferably between 100 and 220 105 Pa.
s The mass of organic solvent introduced into the autoclave represents at least 3%, preferably between 3.5% and 25% of the mass supercritical or liquid fluid used to cause desolvation of the coating agent. The microparticles obtained by the use of this first process has an almost free outer layer 1o 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, 1s in particular homopolymers and copolymers of lactic acids and glycolics, and more particularly PLA (Poly-L-lactide) and PLGA (Poly-Lactic-co-Glycolic-Acid), - amphiphilic block polymers of poly lactic acid-polyoxide type ethylene, 20 - biocompatible polymers of polyethylene glycol, polyoxide type ethylene, - polyanhydrides, poly (ortho esters), poly- ~ -caprolactones and their derivatives, - poly (a-hydroxybutyrate), poly (hydroxyvalerate) and copolymers 2s poly (~ i-hydroxybutyrate-hydroxyvalerate), - polyic acid, - polyphosphazenes, - block copolymers of polyethylene oxide-polyoxide type propylene, so - polyamino acids), - polysaccharides, WO 01/12160 g PCT / FR00 / 02282 - 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, s DMPC, DPPC, DSPC), chain-linked diphosphatidyl ethanolamines fatty acids from C12 to C18 (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with chains from C12 to C18 (DLPS, DMPS, DPPS, DSPS), and the mixtures which would contain the phospholipids mentioned, - fatty acid esters such as glyceryl stearates, laurate 1o of glyceryl, cetyl palmitate, or mixtures which would contain these compounds, - mixtures which would contain the compounds mentioned above.
The implementation of the second method according to the invention consists 1s to put an active principle in suspension in a supercritical fluid containing at least one coating agent dissolved in it then at modify the pressure and / or temperature conditions of the medium to ensure the coacervation of the particles, by precipitation of the agent coating around the particles of active principle, that is to say ensuring the 2o 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, 2s DMPG, DPPG, DSPG), phosphatidylcholines, diphosphatidylcholines with fatty acid chains from C12 to C18 (DLPC, DMPC, DPPC, DSPC), chain-linked diphosphatidyl ethanolamines fatty acids from C12 to C18 (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with chains from C12 to C18 (DLPS, DMPS, DPPS, 3o DSPS), and the mixtures which would contain the phospholipids mentioned, - mono, di, triglycerides whose fatty acid chains go from C4 to C22, and the mixtures containing them, WO 01/12160 g PCT / FR00 / 02282 - mixtures of glycerides and polyethylene glycol esters, - cholesterol, fatty acid esters such as glyceryl stearates, laurate glyceryl, cetyl palmitate, s - the 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.
Coacervation (or aggregation) of a coating agent is caused 1o by physico-chemical modification of a medium containing a substance active in suspension in a solution of coating agent in a solvent, said solvent being a supercritical fluid.
The supercritical fluid preferentially used is C02 supercritical (C02SC), typical initial operating conditions 1s of this second process will be around 31 to 80 ° C and the pressures of 75 to 250 105 Pa, although higher values of either or both of the parameters, provided of course that higher values have no detrimental or degrading effect on the active ingredient during coating, or on the coating agents.
2o In addition, one can also choose other fluids used commonly as supercritical fluids. These include ethane, which becomes supercritical above 32 ° C and 48 105 Pa, the nitrogen dioxide, the critical point of which is 36 ° C. and 72 105 Pa, the propane whose critical point is 96 ° C and 42 105 Pa, trifluoromethane whose 2s critical point is 26 ° C and 47 105 Pa, and the chlorotrifluoromethane of which the critical point is 29 ° C and 39 105 Pa.
This second process involves the suspension, in a closed and stirred autoclave, of an active ingredient which is not soluble in the fluid 3o supercritical, said supercritical fluid containing a coating agent which is found in the state of solute.

The pressure and / or temperature are then changed so reducing the solubility of the coating agent in the fluid. So affinity of the coating agent for the active ingredient increases so that this coating is adsorbed around the active ingredient. Once this coating agent s deposited on the active ingredient, the autoclave is depressurized and the microparticles are recovered.
To implement this second method, the principle is placed active to be coated and the coating agent (s) in an autoclave equipped of an agitator, then pressurize the system by introducing into 1o the autoclave a fluid supplied under supercritical conditions. Then, we changes the temperature and / or pressure inside the autoclave by 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, they precipitate) and 1s the affinity of these agents for the surface of the active principle leads to their adsorption on this surface. A variant of this process is to place the coating agent in the autoclave before introducing the active principle therein or again by simultaneously introducing the active principle and a fluid into it likely to go into the supercritical state. The pressurization of 20 the autoclave to produce a state of supercritical fluid will then cause dissolving the coating agent 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 the 2s fluid likely to pass to the supercritical state. The coating agent is brought to the state of solute by increasing the temperature and pressure, then is transferred to the autoclave where the active ingredient is located.
This ensures the deposition of the coating agent in such a way that this agent follows the surface of the active ingredient.
3o The active principle can be in the form of a liquid which can thus form an emulsion in the supercritical fluid, of particles preformed solids, and in particular of microparticles possibly already coated for example with mono- or disaccharides. The speeds agitation can vary between 150 and 700 rpm for particles solids and between 600 and 1000 rpm when the active ingredient is a liquid.
s Such stirring ensures the suspension of the active principle in the supercritical fluid when it is introduced. Conditions supercritical are ensured by a change in temperature and / or pressure inside the autoclave. So when the fluid supercritical is C02, the temperature of the autoclave is between 10 35 and 80 ° C, preferably between 35 and 50 ° C, and the pressure is understood between 100 and 250 105 Pa, and preferably between 180 and 220 1 OS 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 200 105 Pa, and preferably between 1s 50 and 150 105 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 150 105 Pa.
The coating agent is introduced into the autoclave at the same time as 20 supercritical fluid or well before the introduction into the autoclave of the supercritical fluid. In any case to ensure good solubilization of the coating agent in the supercritical fluid, the system is maintained at equilibrium with stirring, the adequate concentration is established in principle active and coating agent depending on the desired microparticles and 2s leaves this balance under agitation for one hour. We then modulate temperature and pressure at a speed slow enough to completely transfer the coating agent (s) from the supercritical fluid on the surface of the active ingredient and the system is depressurized to isolate the microparticles that are removed from the autoclave.
n / a The microparticles according to the present invention have a diameter between 1 pm and 30 Nm, preferably between 1 pm and 15 Nm, and even more preferably between 2 Nm and 10 Nm and a bulk density between 0.02 g / cm3 and 0.8 g / cm3 and preferably between 0.05 g / cm3 and 0.4 g / cm3.
The mass ratio of active ingredient / coating agent of these microparticles is preferably between 95/5 and 5/95.
s In the case of controlled release microparticles, the amount of active ingredient is low compared to the coating agent, the mass ratio active ingredient / coating agent is then between 5/95 and 20/80, at otherwise in the case where the coating is intended to stabilize the particle, especially when the microparticle is immediate release, the report 1o mass active ingredient / coating agent is generally between 95/5 and 70/30 and preferably between 95/5 and 80/20.
Coating agents for microparticles according to the invention advantageously belong to the following families - biodegradable (co) polymers of α-hydroxycarboxylic acids, 1s in particular homopolymers and copolymers of lactic acids and glycolics, and more particularly PLA (Poly-L-lactide) and PLGA (Poly-Lactic-co-Glycolic-Acid), - mono, di, triglycerides whose fatty acid chains go from C4 to C22, and the mixtures containing them, 20 - mixtures of glycerides and polyethylene glycol esters, - cholesterol, - amphiphilic block polymers of poly lactic acid-polyoxide type ethylene, - biocompatible polymers of polyethylene glycol, polyoxide type 2s of ethylene, - polyanhydrides, poly (ortho esters), poly-s-caprolactones and their derivatives, - poly (~ 3-hydroxybutyrate), poly (hydroxyvalerate) and copolymers poly (~ 3-hydroxybutyrate-hydroxyvalerate), 30 - polyic acid, - polyphosphazenes, - block copolymers of polyethylene oxide-polyoxide type propylene, - polyamino acids), - polysaccharides, s - 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), chain disphosphatidyl etanolamines 1o of fatty acids from C12 to C18 (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with chains from C12 to C18 (DLPS, DMPS, DPPS, DSPS), and the mixtures which would contain the phospholipids mentioned, - fatty acid esters such as glyceryl stearates, laurate glyceryl, cetyl palmitate, 1s - mixtures of at least two compounds chosen from derivatives greases cited above and such that they have suitable solubilities.
According to the coating agent, the solubility in supercritical fluids, and the coating conditions, we can thus implement the first or the second method described above.
2o said active ingredient can be in the form of a liquid, a solid powder or an inert porous solid particle comprising an active ingredient on its surface.
The active ingredients used are chosen from compounds very varied therapeutic and prophylactic. They are more 2s particularly chosen from proteins and peptides such as insulin, calcitonin, LH-RH hormone analogs, polysaccharides such as heparin, anti-asthmatics such as budesonide, beclometasone dipropionate and its active metabolite Beclometasone 17-monopropionate, beta-estradiol hormones, 3o testosterone, bronchodilators such as albuterol, agents cytotoxic, corticosteroids, antigens, DNA fragments Figure 1 is an electron microscopic photograph of a microparticle obtained according to Example 2.
Figure 2 is an electron microscopic photograph of microparticles obtained according to Example 3.
The examples which follow illustrate the invention without limiting its scope.
Example 1 1o This example illustrates the first method of implementing the invention.
80 mg of PLGA are dissolved in 80 ml of ethyl acetate. We suspends micronized insulin 400 mg in solution as well obtained at 250 rpm and the suspension is placed in an autoclave of 1s capacity 1.0 I. First, the pressure is increased to 100 105 Pa by introducing the liquid C02 while remaining at constant temperature 28 ° C.
The C02 in the liquid state mixes with the suspension allowing thus wetting insulin, and also ensuring precipitation 2o progressive coating agent.
We pass C02 to the supercritical state by increasing pressure gradually up to 150 105 Pa. Maintain jointly the temperature at 40 ° C. So we extract the acetate ethyl. We maintains these conditions for 15 minutes, then the mixture is discharged 2s CO 2 / ethyl acetate by decompressing up to 75 105 Pa in a separator by keeping the temperature above 35 ° C.
The ethyl acetate is recovered in this separator and the CO 2 returns in a tank.
The ethyl acetate is recovered and the successive cycles are repeated so of introduction of liquid C02, passing to the supercritical state and evacuation of C02 + ethyl acetate until complete elimination of ethyl acetate.

The decompression must be done by the gas phase in order to not to reconcentrate coating agent in the remaining ethyl acetate.
After the decompression phase, the operation can be repeated several times.
times by reintroducing C02 in order to find a pressure of 150 1 OS Pa s and a temperature of 40 ° C. Finally we depressurize and extract the C02 + solvent mixture then fresh C02 is reintroduced which is brought to the supercritical state in order to completely extract the solvent. Temperature in this case is generally between 35 and 45 ° C and the pressure between 180 and 220 105 Pa.
1o 250 mg of non-aggregated size microparticles are thus obtained average of 3 pm and comprising 80 to 90% by weight of insulin, which have improved fogging properties.
Example 2 1s This example illustrates the second method of implementing the invention.
In a 0.3 I pressurizable and stirred autoclave fitted with an insert porous, 150 mg of bovine serum albumin (BSA) prepared by 2o atomization, and 600 mg of Gelucire ~ 50/02 in the form of shavings.
COZ is introduced into the autoclave, up to a pressure of 95 105 Pa for a temperature of 25 ° C. The C02 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 220 105 Pa; the C02 East 2s in the supercritical state and its density is 0.805 g / cm3.
The system is allowed to balance for one hour. We decrease then the autoclave temperature at 19 ° C for a period of 38 minutes starting from 50 ° C. The suspended phase in C02 supercritical thus transforms into a mixture of liquid and gaseous C02, The particles of active principle being in suspension in the liquid CO 2.
In then depressurizing to atmospheric pressure, BSA microparticles coated with Gelucire ~ 50/02.
250 mg of non-aggregated BSA particles of mean diameter equal to 10 Nm coated with a layer of gelucire ~ 50/02, s whose active ingredient / coating agent mass ratio is approximately 30/70.
These microparticles have improved nebulization properties.
Example 3 1o This example illustrates the second method of implementing the invention.
300 mg of pressurized and stirred autoclave are placed 300 mg ovalbumin (OVA) prepared by atomization, and 300 mg of Gelucire ~
50/13 in the form of chips.
/ s C02 is introduced into the autoclave, up to a pressure of 109 105 Pa for a temperature of 23 ° C. The C02 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 180 105 Pa, the C02 East in the supercritical state.
2o Let the system balance for an hour. We decrease then the autoclave temperature at 16 ° C for a period of 43 minutes starting from 35 ° C. The suspended phase in C02 supercritical thus transforms into a mixture of liquid and gaseous C02.
Then depressurizing to atmospheric pressure we get 2s of OVA microparticles coated with Gelucire ~ 50/13.
300 mg of non-aggregated OVA particles of average diameter equal to 9 ~ m coated with a layer of gelucire ~ 50/13, which have improved nebulization properties.

WO 01/12160 1 ~ PCT / FR00 / 02282 Example 4 This example illustrates the second method of implementing the invention.
s In a 0.3 I pressurizable autoclave fitted with a porous insert, 300 mg of beclomethasone dipropionate are placed in the form of loose powder prepared by atomization, and 50 mg of Dilauroyl Phosphatidyl Glycerol (DLPG).
COZ is introduced into the autoclave, up to a pressure of 98 10 105 Pa for a temperature of 23 ° C. The C02 is then in the state liquid.
Agitation is started, at 460 rpm. Then the autoclave is heated up to 60 ° C. The pressure is then 300 105 Pa, the C02 is at the supercritical state and its density is 0.830 g / cm3.
The system is allowed to balance for one hour. We decrease 1s then the temperature of the autoclave at 20 ° C for a period of 65 minutes. The suspended phase in supercritical C02 is transformed thus in a mixture of liquid and gaseous C02, the principle particles active being suspended in liquid C02. Then depressurizing up to atmospheric pressure, microparticles of 2 beclomethasone dipropionate coated with DLPG.
200 mg of non-aggregated particles of dipropionate are thus obtained.
beclomethasone with a diameter of 5 Nm coated with a layer of DLPG, whose active ingredient / coating agent mass ratio is about 90/10. These microparticles have properties of 2s improved nebulization.

Claims (10)

1. Biocompatible microparticle intended to be inhaled comprising at least one active principle and at least one coating layer this active principle which is the outer layer of said microparticle, said outer layer containing at least one coating agent, characterized in that that said microparticle has an average diameter of between 1 µm and 30 µm, an apparent density between 0.02 g/cm3 and 0.8 g/cm3 and that it is capable of being obtained according to a process comprising the essential steps which are the bringing together of a coating agent with an active principle and the introduction of a supercritical fluid, under stirring in a closed reactor. 2. Microparticles according to claim 1, characterized in that that they have an average diameter of between 1 µm and 15 µm, and even more preferably between 2 μm and 10 μm, an apparent density between 0.05 g/cm3 and 0.4 g/cm3, and in that the mass ratio active principle/coating agent 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 ingredient in a solution of at least least one substantially polar coating agent in a solvent organic, 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 state supercritical, - bringing the suspension into contact with a fluid in the state supercritical, so as to desolvate the agent in a controlled manner substantially polar coating and ensuring its coacervation, - substantially extract the solvent by means of a fluid to 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 placing an active principle in suspension in a supercritical fluid containing at least one agent encapsulant dissolved in it and then ensuring the coacervation of the particles, by physico-chemical modification of the environment. 5. Microparticle according to claim 3, characterized in that the coating agent is selected from the group formed by - biodegradable (co)polymers of .alpha.-hydroxycarboxylic acids, in particular homopolymers and copolymers of lactic acids and glycolics, and more particularly PLA (Poly-L-lactide) and PLGA (Poly-Lactic-co-Glycolic-Acid), - amphiphilic block polymers of the polylactic acid-polyoxide type ethylene, - biocompatible polymers such as polyethylene glycol, polyoxide ethylene, - polyanhydrides, poly(ortho esters), poly-.epsilon.-caprolactones and their derivatives, - poly (.beta.-hydroxybutyrate), poly(hydroxyvalerate) and copolymers poly(.beta.-hydroxybutyrate-hydroxyvalerate), - malic polyacid, - polyphosphazenes, - block copolymers of the polyethylene oxide-polyethylene oxide type propylene, - poly(amino acids), - polysaccharides, - phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with C12 to C18 fatty acid chains (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, C12 to C18 fatty acid chain diphosphatidylcholines (DLPC, DMPC, DPPC, DSPC), chain diphosphatidyl ethanolamines fatty acids from C12 to C18 (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with chains from C12 to C18 (DLPS, DMPS, DPPS, DSPS), and the mixtures which would contain the cited phospholipids, - fatty acid esters such as glyceryl stearates, laurate glyceryl, 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 selected from the group formed by - phospholipids such as phosphatidyl glycerols, diphosphatidyl glycerols with C12 to C18 fatty acid chains (DLPG, DMPG, DPPG, DSPG), phosphatidylcholines, C12 to C18 fatty acid chain diphosphatidylcholines (DLPC, DMPC, DPPC, DSPC), chain diphosphatidyl ethanolamines fatty acids from C12 to C18 (DLPE, DMPE, DPPE, DSPE), diphosphatidyl serines with chains from C12 to C18 (DLPS, DMPS, DPPS, DSPS), and the mixtures which would contain the cited phospholipids, - mono, di, triglycerides whose fatty acid chains range from C4 to C22, and mixtures containing them, - mixtures of glycerides and polyethylene glycol esters, - cholesterol, - fatty acid esters such as glyceryl stearates, laurate glyceryl, cetyl palmitate, - biodegradable or bioerodible polymers soluble in a fluid supercritical, - 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 the proteins and peptides such as insulin, calcitonin, analogues of the LH-RH hormone, polysaccharides such as heparin, anti-asthmatics such as budesonide, beclometasone dipropionate and its active metabolite beclometasone 17-monopropionate, hormones beta-estradiol, testosterone, bronchodilators such as albuterol, cytotoxic agents, corticosteroids, antigens, DNA fragments 8. Microparticle according to claim 2 characterized in that the microparticle is immediate release and the mass ratio active principle/coating agent of this particle is between 95/5 and 80/20. 9. Process for preparing microparticles intended to be inhaled and comprising the following steps:
- suspending an active ingredient in a solution of at least least one substantially polar coating agent in a solvent organic, 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 state supercritical, - bringing the suspension into contact with a fluid in the state supercritical, so as to desolvate the agent in a controlled manner substantially polar coating and ensuring its coacervation, - substantially extract the solvent by means of a fluid to the supercritical state and evacuate the fluid mixture supercritical/solvent, - recover the microparticles. 10. Process for preparing microparticles intended to be inhaled which consists in placing, under agitation in a closed reactor, a active ingredient suspended in a supercritical fluid containing at least least one coating agent dissolved therein and then ensuring the coacervation of particles, by physico-chemical modification of the medium.