Lipid microcapsules preferably comprising a retinoid, and composition containing same, method for the production thereof, and use of same in dermatology

Lipid microcapsules are described that can include at least one irritant active substance, more specifically a retinoid, in a soluble form. Also described, are pharmaceutical compositions comprising the same, and methods for the production thereof. A method of using the composition to treat dermatological pathologies is also described.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a National Stage of PCT/EP2014/076658, filed Dec. 4, 2014, and designating the U.S. (published on Jun. 11, 2015, as WO 2015/082659 A1), which claims priority under 35 U.S.C. § 119 to French Patent Application No. 1362117, filed Dec. 4, 2013, each hereby expressly incorporated by reference in its entirety and each assigned to the assignee hereof.

The present invention relates to lipid microcapsules which have an oily internal phase and a non-polymeric shell obtained from at least one lipid compound chosen from amphiphilic lipids.

In particular, the invention relates to microcapsules comprising an irritant active ingredient and more particularly a retinoid compound, said irritant active ingredient being present in dissolved form in the microcapsules comprising an oily core.

The invention also relates to the primary emulsion composed of the microcapsules comprising an oily core, dispersed in an aqueous phase, and to the pharmaceutical composition comprising the primary emulsion in a pharmaceutically acceptable carrier.

The invention also relates to the process for preparing the primary emulsion, and the pharmaceutical composition comprising the lipid microcapsules. Finally, the invention relates to a composition for use thereof in the treatment of dermatological complaints, in particular acne.

Those skilled in the art know that the activity of certain pharmaceutical active ingredients is inseparable from a certain level of irritation. It is, however, essential to find compositions for maintaining the biological activity of the active ingredient while at the same time minimizing its irritant nature. Retinoids are active agents commonly used in dermatology, but the majority are known as being irritant active ingredients. It is therefore important, while maintaining the pharmaceutical activity, to improve the tolerance of this family of antiacne molecules.

The prior art discloses several formulation patents for improving the topical tolerance of irritant active ingredients, in particular in the case of retinoids, by adding anti-irritant compounds to the composition.

The Applicant has protected in patent FR 2 894 820 galenical formulations using anti-irritants such as allantoin or EDTA in combination with a particular retinoid, adapalene.

In patent application WO 2006/037552, the inventors add constituents to the formulation base such as interleukin-8 inhibitor to act on the irritation process.

In patent application WO 2005/079775, the inventors improve the tolerance of retinoids by adding idebenone or a derivative thereof.

Won et al., U.S. Pat. No. 5,955,109, incorporate a retinoid into porous microspheres (Microsponge®) to reduce the release of the retinoid into the layers of the skin, which gives rise to a decrease in the level of irritation by controlling the release kinetics of the active agent through the skin.

In patent application WO 2005/039532, the authors use a retinoid in an oil-in-water microemulsion for the purpose of improving the bioavailability. This microemulsion is composed of a phospholipid and of a sodium hyaluronate or modified hyaluronic acid.

Saurat et al. in patent FR 2 865 651 propose the combination of a retinoid with one or more hyaluronate fragments in a formulation for dermatological use in the case of treatments for which it will be necessary to improve the condition of the skin.

Cattaneo in patent US 2005/0281886 discloses chitosan microparticles and nanoparticles containing a retinoid. These microparticles and nanoparticles generated by a high-viscosity chitosan reduce the irritant effect of the retinoids.

There are in the prior art many encapsulation techniques which make it possible to obtain microcapsules.

The term “microencapsulation” defines all of the technologies which make it possible to obtain the preparation of individualized microparticles, consisting of a coating material containing an active material.

The terminology “microcapsules” implies entities of which the diameter is between 1 and 1000 μm. The term “nanocapsules” is reserved for capsules of which the size is less than 1 micron.

The substance encapsulated may be in the form of fine particles of divided solid, of a liquid, or of a gaseous compound. The microcapsule makes it possible to preserve the encapsulated substance in the form of a finely divided state, and to release it under the desired conditions.

The microparticles obtained by microencapsulation may be in two types of distinct morphologies:

microspheres which are particles consisting of a continuous macromolecular or lipid network forming a matrix in which the active material is finely dispersed. The latter may be in the form of solid fine particles or else of droplets of solution;

microcapsules which are reservoir particles consisting of a core of liquid or solid active material, surrounded by a continuous solid shell of coating material.

The various microencapsulation methods can be categorized according to various criteria. Richard and Benoit, (Microencapsulation, 2000, Techniques de l'Ingénieur [Techniques of the Engineer], J2210, 1-20) propose four different ways to categorize encapsulation methods:the processes can be categorized according to whether or not organic solvent is used, some techniques, such as complex coacervation, using supercritical fluids,the nature of the dispersing medium can also be used as a basis for a categorization: it may be liquid (interfacial polycondensation, coacervation), gaseous (spray drying, fluidized bed coating), or in the supercritical state (phase separation),the family to which the compound used to obtain the capsule belongs may also make it possible to categorize the encapsulation modes: it is possible to use preformed polymers (coacervation), lipids (spray-congealing), or else monomers (interfacial polycondensation, polymerization in a dispersed medium),finally, a last categorization is based on the nature of the ingredient according to which the microencapsulation is carried out:physicochemical processes are distinguished from chemical and mechanical processes.

The various encapsulation methods are summarized in the table presented below according to the nature of the process (Finch and Bodmeier, 2005, Microencapsulation, Wiley-VCH verlag GmbH & Co, KGa, Weinheim10.1002/14356007.a16_575).

Since the mechanical processes make it possible to obtain only microspheres, microcapsules are generally obtained by means of physicochemical or chemical processes. These processes require the use of preformed coating agents such as polymers or monomers which, in situ via a specific polymerization mechanism, allow the formation of the coating material.

Solubility Data for Trifarotene in Various Oily Phases

The object of this preformulation study is to identify dissolving oily phases in which Trifarotene has a solubility of greater than 0.1% w/w and in which it is chemically stable.

The stability of the active agent was evaluated by liquid chromatography coupled to a UV detector (HPLC-UV).

AT Ambient Temperature

Following the results of this solubility and stability study, it is noted that propylene glycol monocaprylate, propylene glycol monolaurate, diisopropyl adipate, PPG-15 stearyl ether and macrogol oleate are suitable for dissolving Trifarotene.

Following these results, diisopropyl adipate and PPG-15 stearyl ether are preferred solvents for obtaining the desired concentrations of Trifarotene in the pharmaceutically acceptable carrier.

Compositions of Primary Emulsions a to G Containing the Placebo Lipid Microcapsules Before Dilution in a Pharmaceutically Acceptable Carrier

By using the preparation processes previously mentioned and according to the mode of dispersion of the hydrogenated lecithin as previously defined in the present description, lipid microcapsules were prepared with an oily core containing an oil or a mixture of oils.

The compositions of the primary emulsions A to G containing such microcapsules are therefore the following:

Compositions of Primary Emulsions A1 and B1 Containing the Lipid Microcapsules Comprising Trifarotene Before Dilution in a Pharmaceutically Acceptable Carrier

By using the processes previously mentioned and according to the hydrogenated lecithin dispersion mode as previously defined in the present description, lipid microcapsules were prepared and contain in the oily core Trifarotene dissolved in a solvent oil or a mixture of solvent oils.

The primary emulsions were prepared preferentially using, as solvent for the Trifarotene, either diisopropyl adipate or PPG-15 stearyl ether.

The compositions of the primary emulsions A1 and B1 are therefore the following:

Characterization of the Primary Emulsion of Composition A1 of Example 3, Containing Trifarotene, Obtained According to the Three Processes and with the Various Modes of Dispersion of the Hydrogenated Lecithin

The macroscopic observation is performed on the formulation in its original packaging.

Whatever the type of equipment, with the hydrogenated lecithin 100% dispersed in the fatty phase, the primary emulsions A1 obtained have the same appearance.

In particular, with the Magic Lab, the primary emulsions A1 obtained have the same appearance as the mode of dispersion of the hydrogenated lecithin either 100% in the aqueous phase or 100% in the oily phase.

Characterization of the Particle Size Distribution of the Primary Emulsion of Composition A1 of Example 3, Containing Trifarotene, Obtained with the Magic Lab

In the following example, the primary emulsions A1 were prepared with the Magic Lab by dispersing the hydrogenated lecithin either 100% in the aqueous phase or 100% in the fatty phase.

The particle size distribution of the lipid microcapsules in the primary emulsion A1 was determined using a Mastersizer 3000 particle size analyzer (Malvern). The composition is prediluted before analysis (1 g in 9 g of purified water). Five successive measurements are carried out on the same preparation.

The particle size distribution by volume is presented by expressing D10, D50and D90:D10corresponds to the size of the particles below which is 10% of the sample,D50corresponds to the size of the particles below which is 50% of the sample,D90corresponds to the size of the particles below which is 90% of the sample.

The results obtained are as follows:

The data show that the lipid microcapsules obtained have a size greater than 1 micrometer.

Examples of Compositions of Gel Type According to the Invention Prepared from the Placebo Primary Emulsions of Compositions A to E of Example 2

In order to prepare compositions of gel type IGto XVIGaccording to the invention, various amounts of primary emulsions prepared according to example 2 were taken and diluted in a gel base.

To obtain a gel of 100 grams (gels IGand IVGto XVIG) comprising approximately 5% of encapsulated oil, 17.784 grams of the placebo primary emulsion of compositions respectively A, D and E of example 2 are added to the formulation.

To obtain a gel of 100 grams (gel IIG) comprising 10% of encapsulated oil, 35.855 grams of the placebo primary emulsion of composition B of example 2 are added to the formulation.

To obtain a gel of 100 grams (gel IIIG) comprising 20% of encapsulated oil, 71.71 grams of the placebo primary emulsion of composition C of example 2 are added to the formulation.

Examples of compositions of gel type obtained according to the invention are thus as follows:

Examples of Compositions of Gel Type According to the Invention Prepared from the Primary Emulsions of Example 3 Containing Trifarotene

In order to prepare compositions of gel type IG′ to IVG′ according to the invention, an amount of corresponding primary emulsion prepared according to example 3 was taken and diluted in a gel base.

To obtain a gel of 100 grams containing 0.01% of Trifarotene, contained in the presence of approximately 5% of solvent oil in the microcapsules, 17.784 grams of the primary emulsion A1 or B1 of example 3 are added to the formulation.

Examples of compositions of gel type obtained according to the invention are thus as follows:

Examples of Compositions of Formulations of Cream Type According to the Invention Prepared from the Placebo Primary Emulsions of Compositions A, D and E of Example 2

In order to prepare compositions of cream type according to the invention ICto IIIC, an amount of corresponding primary emulsion prepared according to example 2 was taken and integrated at a predetermined moment during the process for preparing a cream.

To obtain a cream of 100 grams comprising approximately 5% of encapsulated oil, 17.784 grams of the primary emulsion of compositions respectively A, D and E of example 2 are added to the formulation.

Examples of compositions of cream type ICto IIICobtained according to the invention are thus as follows:

Examples of Compositions of Formulations of Cream Type According to the Invention Prepared from the Primary Emulsions A1 and B1 of Example 3 Containing Trifarotene

In order to prepare compositions of cream type according to the invention I′Cto II′C, an amount of primary emulsion prepared according to example 3 was taken and integrated at a predetermined moment during the process for preparing a cream.

To obtain a cream of 100 grams containing 0.01% of Trifarotene, contained in the presence of approximately 5% of solvent oil in the microcapsules, 17.784 grams of the primary emulsion of composition A1 or B1 of example 3 are added to the formulation.

Examples of compositions of cream type obtained according to the invention are thus as follows:

Characterization of Composition IGof Example 7 of Gel Type According to the Invention, Prepared from Primary Emulsions Containing Trifarotene, Obtained According to the Three Processes

In the present example, the hydrogenated lecithin is 100% dispersed in the fatty phase.

Each test carried out is described below:The macroscopic observation is performed on the formulation in its original packaging.The microscopic observation is performed using an Axio.Scope A1 microscope (polarized light, objective ×20).The pH measurement is taken in the formulation.The viscosity measurement is performed using an apparatus of Brookfield RVDVII+ type. The measurements are performed after 1 min, in the original packaging.

Whatever the equipment used, Polytron, Magic Lab or sonication probe, the gels have the same characteristics.

Study of Stability of the Gels of Example 10 According to the Process Used

Each test carried out is described below:The macroscopic observation is performed on the formulation in its original packaging.The microscopic observation is performed using an Axio.Scope A1 microscope (polarized light, objective ×20).The pH measurement is taken in the formulation.The viscosity measurement is performed using an apparatus of Brookfield RVDVII+ type. The measurements are performed after 1 min, in the original packaging.The Trifarotene titer is verified by HPLC after preparation, the results at T0 are expressed as % of the theoretical real concentration, and the results at T3M are expressed as % of the concentration at T0.

Process by Magic Lab

Whatever the type of equipment, the gels containing the microcapsules are stable for 3 months at ambient temperature and at 40° C.

In this respect and in light of the results of examples 4 and 10, the process using the Magic Lab equipment will be preferentially be chosen in the examples to follow.

Characterization of Compositions IG, IVGand VGof Example 6 of Gel Type According to the Invention, Prepared from Placebo Primary Emulsions, Obtained According to Two Different Modes of Introduction of the Hydrogenated Lecithin

In the present examples, the equipment that was used for preparing the primary emulsions is the Magic Lab.

In this table, gel No. 1 corresponds to gels IG, IVGand VGof example 6, in which the lecithin was 100% dispersed in the aqueous phase.

In this table, gel No. 2 corresponds to gels IG, IVGand VGof example 6, in which the lecithin was 100% dispersed in the oily phase.

Depending on the oil used in the formulation, the hydrogenated lecithin dispersion mode can generate different characteristics.

FIGS. 1 and 2represent the images obtained under a microscope (objective 40 and magnification ×252) of the microcapsules in gels No. 1 and No. 2 respectively that were prepared from the primary emulsion D containing PPG-15 stearyl ether as oil (gels corresponding to gel IVGin example 6).

The microscopic observation of the microcapsules reveals that the microcapsules in gels No. 1 and No. 2 differ in terms of polydispersity and shape.

Indeed, it is observed that the microcapsules ofFIG. 1are uniform in size and in shape. On the other hand, those ofFIG. 2are more non-uniform, both in terms of size and in terms of shape. Thus, for a defined oil, the hydrogenated lecithin dispersion mode has an effect on the physical appearance of the microcapsules.

FIGS. 3 and 4represent the images obtained under a microscope (objective 40 and magnification ×252) of the microcapsules in gels No. 1 and No. 2 respectively that were prepared from the primary emulsion E containing capric/caprylic acid triglycerides as oil (gels corresponding to gel VGin example 6).

The microscopic observation of the microcapsules reveals that the microcapsules in gels No. 1 and No. 2 do not differ in terms of polydispersity and shape.

Thus, for another defined oil, the hydrogenated lecithin dispersion mode does not have an effect on the physical appearance of the microcapsules.

The observations therefore demonstrate that the conditions which result in a better production of microcapsules can be dependent on the hydrogenated lecithin dispersion mode according to the oil used.

In this respect, a hydrogenated lecithin dispersion mode may be preferred for each oil type.

In one preferred mode according to the invention, with acid esters and triglycerides, for instance diisopropyl adipate, as oily solvent, the preferred hydrogenated lecithin dispersion mode is 100% in the fatty phase.

In one preferred mode according to the invention, with polyethylene glycol ethers, for instance PPG-15 stearyl ether, as oily solvent, the preferred hydrogenated lecithin dispersion mode is 100% in the aqueous phase.

Study of Stability of Gels No. 1 and No. 2 of Example 12 According to the Oil Used (Compositions IVGand VGof Example 6) and According to the Hydrogenated Lecithin Introduction Mode

Gel No. 1: Dispersion in Aqueous Phase from Composition IVGof Example 6 (PPG-15 Stearyl Ether

Gel No. 2: Dispersion in Fatty Phase from Composition IVGof Example 6 (PPG-15 Stearyl Ether

Gel No. 1: Dispersion in Aqueous Phase from Composition VGof Example 6 (Capric/Caprylic Acid Triglycerides

Gel No. 2: Dispersion in Fatty Phase from Composition VGof Example 6 (Capric/Caprylic Acid Triglycerides

FIGS. 5 and 6represent the images obtained under a microscope (objective 40 and magnification ×252) of the microcapsules in gels No. 1 and No. 2 that were prepared from the compositions IVGcontaining PPG-15 stearyl ether as oil after 6 months of storage at a temperature of 40° C.

Microscopic observation of the microcapsules in gels No. 1 and No. 2 proves to be significant regarding the stability of the microcapsules according to the hydrogenated lecithin dispersion mode.

With 100% dispersion of the hydrogenated lecithin in the fatty phase, the microcapsules are very non-uniform in size and are deformed (FIG. 6).

With 100% dispersion of the hydrogenated lecithin in the aqueous phase, the microcapsules are more uniform and more even in size (FIG. 5).

The observations therefore demonstrate that the conditions which result in better stability of the capsules over time are 100% dispersion of the hydrogenated lecithin in the aqueous phase, in the case of the use of PPG-15 stearyl ether.

FIGS. 7 and 8show the images obtained under a microscope (objective 40 and magnification ×252) of the microcapsules containing capric/caprylic acid triglycerides after 6 months of storage at a temperature of 40° C.

The microcapsules are as a whole uniform and even in size, after 6 months of stability at 40° C. (FIGS. 7 and 8).

The observations therefore demonstrate that the conditions which result in stability of the capsules over time can occur with a 100% dispersion of the hydrogenated lecithin in the aqueous phase or a 100% dispersion in the fatty phase, in the case of the use of capric/caprylic acid triglycerides.

In this respect and in the light of the results of examples 12 and 13, a hydrogenated lecithin dispersion mode may be all the more justified for each oil type.

Characterization of Compositions IG′ and IIG′ of Example 7 of Gel Type According to the Invention, Prepared from Primary Emulsions and Containing Trifarotene, Obtained According to the Preferred Hydrogenated Lecithin Introduction Mode According to the Oil Used

In the present examples, the equipment that was used for preparing the primary emulsions is the Magic Lab.

The preferred dispersion mode for the hydrogenated lecithin with diisopropyl adipate is 100% in the fatty phase.

The preferred dispersion mode for the hydrogenated lecithin with PPG-15 stearyl ether is 100% in the aqueous phase.

By way of example, Gel No. IG′ is represented inFIG. 9. It was characterized by scanning electron microscopy after cryofracture according to the following protocol:Freezing in liquid nitrogen and under vacuumMechanical fractureSublimation (20 minutes at −95° C.)Metallization (platinum) in order to amplify the secondary electronsObservation by scanning electron microscopy using an MEB Quanta 250 FEG from FEI

Study of Stability of the Gels of Example 14 According to the Oil Used and According to the Hydrogenated Lecithin Introduction Mode

Dispersion in Fatty Phase Gel Obtained from Composition IG′ of Example 7 (Diisopropyl Adipate

Dispersion in Aqueous Phase Gel Obtained from Composition IIG′ of Example 7 (PPG-15 Stearyl Ether

The results show that gels are obtained which are stable at three months at ambient temperature and at 40° C. in the presence of an active ingredient, namely Trifarotene.

Characterization of Compositions of Gel Type Prepared from Placebo Primary Emulsions of Composition A of Example 2

In the present examples, the equipment that was used for preparing the primary emulsions is the Magic Lab.

The preferred dispersion mode for the hydrogenated lecithin with diisopropyl adipate is 100% in the fatty phase.

Study of Stability of the Gels of Example 16

The results show that the gels are stable at one month or three months at ambient temperature or at a temperature of 40° C., whatever the nature of the thickener used.

Characterization of Compositions IIIG′ and IVG′ of Example 7 of Gel Type According to the Invention, Prepared from Primary Emulsions and Containing Trifarotene, Obtained According to the Preferred Hydrogenated Lecithin Dispersion Mode According to the Oil Used

In the present examples, the equipment that was used for preparing the primary emulsions is the Magic Lab.

The preferred dispersion mode for the hydrogenated lecithin with diisopropyl adipate is 100% dispersion in the fatty phase.

The preferred dispersion mode for the hydrogenated lecithin with PPG-15 stearyl ether is 100% dispersion in the aqueous phase.

Study of Stability of the Gels of Example 18

The results show that the gels containing an active ingredient, namely Trifarotene, are stable at three months at ambient temperature or at a temperature of 40° C. for various gel formulations.

Characterization of Compositions IIGand IIIGof Example 6 of Gel Type According to the Invention, Prepared from Placebo Primary Emulsions of Compositions B and C of Example 2

In the present examples, the equipment that was used for preparing the primary emulsions is the Magic Lab.

The preferred dispersion mode for the hydrogenated lecithin with the diisopropyl adipate is 100% dispersion in the oily phase.

In the table, gel No. 1 corresponds to gel IIGin which the diisopropyl adipate was dispersed in the fatty phase and to gel IIIGin which the diisopropyl adipate was dispersed in the fatty phase.

Study of Stability of the Gels of Example 20

Composition IIG

The results show that the gels obtained are stable at one month at ambient temperature or a temperature of 40° C., whatever the diisopropyl adipate content.

Characterization of Compositions ICand IIICof Example 9 of Cream Type According to the Invention, Prepared from Primary Emulsions and Containing Trifarotene, Obtained According to the Preferred Hydrogenated Phosphatidylcholine Introduction Mode According to the Oil Used

In the present examples, the equipment that was used for preparing the primary emulsions is the Magic Lab.

The preferred dispersion mode for the hydrogenated lecithin with diisopropyl adipate is 100% dispersion in the fatty phase.

The preferred dispersion mode for the hydrogenated lecithin with PPG-15 stearyl ether is 100% dispersion in the aqueous phase.

Study of Stability of the Creams of Example 20

Study of In Vitro Skin Penetration of Trifarotene Encapsulated in Microcapsules According to Example 14, Dispersed in a Gel

Conditions of the Study:

In this study, the formulations were applied for 16 hours to the surface of the skin. At the end of the application, the Trifarotene is quantified in the various skin compartments: stratum corneum, epidermis, dermis and receiving liquid according to a validated bioanalysis method performed by positive electrospray ionization tandem mass spectrometry, using a Xevo machine (Waters). The quantification limit for Trifarotene is 1 ng/ml. The LC/MS/MS conditions developed made it possible to detect up to 0.1% of the dose applied in each of the compartments (dose not absorbed, stratum, epidermis, dermis and receiving liquid).

The details of the cutaneous application are given in the table below:

ApplicationApplication~2 mg/cm2Amount of active agent applied142~241 ng/cm2Number of cells per formulation6Number of donors per3formulationExposure time16 h

The two formulations tested have the same composition as composition IG′ of example 7 and were produced with the Magic Lab.

Only the hydrogenated phosphatidyl choline introduction mode differentiates the two gels.

The formula of the reference gel is as follows:

The results presented inFIG. 10show the amount penetrated as a percentage of the dose applied (% dose applied) according to the various skin compartments.

The total penetration of Trifarotene from the various gels containing encapsulated Trifarotene is less than the reference in which the Trifarotene is dissolved but not encapsulated.

For the reference comprising Trifarotene, the amount penetrated is about 4.86%.

For the gels containing the microcapsules, the amount penetrated ranges from 3.17% to 3.25%.

The total penetration of the encapsulated Trifarotene is similar whatever the phosphatidylcholine dispersion mode:

With 100% dispersion in the oily phase, the total amount penetrated is: 3.25±1.00%.

With 100% dispersion in the aqueous phase, the total amount penetrated is: 3.17±1.38%.

The epidermal and dermal tissue distribution of Trifarotene is similar whether or not it is encapsulated.

With the microcapsules, the tissue distribution of Trifarotene is similar whatever the hydrogenated phosphatidylcholine dispersion mode.

Thus, the encapsulation of Trifarotene decreases the amount penetrated at the level of the stratum corneum without however modifying the tissue distribution of said Trifarotene.