NL195027C - Process for preparing microparticles for slow release of water-soluble peptides and preparations thereof. - Google Patents

Description

1 195027

Process for the preparation of microparticles for slow release of water-soluble peptides

The invention relates to a method for preparing a microparticle containing a water-soluble peptide-containing drug in a biodegradable, biocompatible polymeric carrier, comprising the steps of: a) dissolving the polymeric carrier material in a suitable solvent, wherein the drug peptide is insoluble, b) adding and dispersing a solution of the drug peptide in a suitable solvent, which is not a solvent for the polymer in the solution of step a), c) adding a phase-inducing agent to the dispersion of step b) for inducing the formation of microparticles and d) adding a liquid to the mixture of step c), or adding the mixture of step c) to a liquid for curing and washing the microparticle, and e ) recovery of the microparticle.

Such a method is known from US-A-4,675,189. This document describes that after the microparticles are formed with LHRH analog decapeptides, they are cured by pouring into a suitable organic solvent, after filtration, the cured microparticles are washed several times with the organic solvent. Subsequently, washing is still carried out with water and with a solution containing non-ionic surfactant.

A disadvantage of this method is the cumbersome washing procedure that is required to obtain contaminated microparticles.

It has now been found that successive repeated washing with organic solvent, water and surfactant solution can be limited by applying a curing and washing step with an oil-in-water emulsion and a more consistent release of the drug over a period of time becomes possible.

As described in the preamble, the invention is therefore characterized in that an oil-in-water emulsion is used as the liquid in step d).

Peptide-containing drugs often exhibit poor bioavailability in the blood after oral or parenteral administration, for example due to their short biological half-lives caused by their metabolic instability. Orally or administered through the nose, they often exhibit poor resorption through the mucous membranes. A therapeutically relevant blood level over a long period of time is difficult to achieve.

The parenteral administration of peptide drugs as depot preparation in a biodegradable polymer, for example as microparticles or implants, has been proposed, with a delayed release after a residence time in the polymer protecting the peptide against enzymatic and hydrolytic influences of the biological media. can be released.

Although some parenteral depot preparations or peptide drugs are known in a polymer in the form of microparticles or an implant, satisfactory peptide release profiles are only obtained in practice in a few cases. Special measures must be taken to provide a continuous peptide release for a serum level of a therapeutically active drug and, if desired, to avoid excessive serum concentrations of the drug that cause undesirable pharmacological side reactions.

The release pattern of a peptide drug depends on numerous factors, for example, on the type of peptide and, for example, whether it is present in the free form or in another form thereof, e.g. in the salt form, which may affect its solubility in water. Another important factor is the choice of the polymer, from an extensive list of possibilities described in the literature.

Each polymer type has its characteristic biological decomposition rate. Free carboxyl groups can be formed which contribute to the pH value in the polymer and thus further influence the water solubility of the peptide and thus its release pattern.

Other factors influencing the release pattern of the depot preparation are the drug loading of its polymeric carrier, its mode of distribution into the polymer, the particle size and, in the case of an implant, moreover its shape. Furthermore, the place of the preparation in the body influences.

Polymer preparations with drugs intended to provide a sustained or delayed release of the drug are known in the art.

U.S. Pat. No. 3,773,919 discloses compositions from which the drug is released at a controlled rate, wherein the drug, e.g., a water-soluble peptide drug, is disclosed. dispersed in a solution of a biodegradable and biocompatible linear polylactice or polylaclide-co-glycolide polymer in a solvent. After coating the drug-containing particles with the polymer, the solvent is removed in the usual manner by drying. US-A-4,293,539 describes, inter alia, antibacterial preparations of a medicinal compound in a matrix of a copolymer of lactic acid and glycolic acid, as an injectable suspension whose particles are obtained by evaporating the solvent from a solution.

T. Chang, J. Bioeng., Vol. 1, pages 25-32, 1976 describe the sustained release of biological materials, enzymes and vaccines from microcapsules with polylactic acid as the semipermeable wall of the capsules.

Polymers and copolymers of lactic acid and glycolic acid as material for surgical applications and for pharmaceutical use in the delayed release and biological decomposition are described in US-A 4,076,798 and 4.1 18,470.

EP-A 0.203.031 describes a series of somatostatin octapeptide analogs, for example compound RC-160 of formula D-Phe-Cys-T yr-DT rp-Lys-Val-Cys-T rp-NH2 with a bridge between the -Cys sections.

The possibility of the somatostatin to be encapsulated in a micro form with polylactide-co-glycolide polymer has been mentioned without further explanation of the method of encapsulation.

It is described in US-A-4,01,312 that a continuous release of an antimicrobial drug, for example the water-soluble polymyxin B, from a polylactide-co-glycolide matrix with a low molecular weight (lower than 2000) and a relatively high glycolide content in the form of an implantation obtained by dispersing the drug in a melt of the copolymer can be obtained if the implantation is inserted into the cow's nipple channel. The drug is released in a short period of time, due to the high glycolid content and the low molecular weight of the polymer, both of which stimulate rapid biological decomposition of the polymer and thus a corresponding rapid release of the drug. Moreover, a relatively high drug load contributes to a rapid release of the drug.

It is described in EP-B 58481 that continuous release of a water-soluble peptide from a polylactide polymer implantation is stimulated by reducing the molecular weight of at least a portion of the polymer molecules, by introducing glycolide units into the polymer molecule, by enhancement of the block polymer character of the polymer if polylactide-co-glycol molecules are used, by increasing the drug loading of the polymer matrix and by increasing the surface of the implant. A preparation of microparticles is not mentioned.

It is described in EP-B 92918 that a continuous release of peptides, preferably hydrophilic peptides, can be obtained over a long period of time if the peptide is incorporated into a conventional hydrophobic polymer matrix, for example of a polylactide that is more accessible to water. made by introducing into its molecule a hydrophilic moiety, e.g. from polyethylene-giycol, polyvinyl alcohol, dextran, polymethacrylamide. The hydrophilic contribution to the amphipatic polymer is given to all ethylene oxide groups in the case of a polyethylene glycol unit, by the free hydroxyl groups in the case of a polyvinyl alcohol unit or of a dextran unit and by the amide groups in the case of a polymethylacrylamide unit. Due to the presence of the hydrophilic unit in the polymer molecules, the implantation will acquire hydrogel properties after the absorption of water. According to the examples, solutions of polylactide and peptide were mixed and freeze-dried and then formed into implants or to a solution of the polylactide an aqueous peptide solution was added for the preparation of a stable water-in-oil dispersion, mono-capsules were produced by adding a non-solvent such as hexane. The particles formed were isolated, filtered and dried.

It is described in GB 2,145,422 B that a sustained release of different types of drugs, e.g. vitamins, enzymes, antibiotics and antigens, can be obtained over a prolonged period of time if the drug is inserted into an implant, e.g. of the size of microparticles made from a polymer of a polyol, for example glucose or mannitol, with one or more, preferably at least 3, polylactide ester groups. The polylactide ester groups preferably contain, for example, glycolide units. No peptides are mentioned. A preparation of 55 microcapsules consists of stirring solutions of active compound and polyol ester in buffered to pH = 7 aqueous phase with, for example, gelatin. The organic solvent is removed from the resulting emulsion. The resulting microcapsules are filtered or centrifuged, washed with, for example, 3 195027 a buffer and dried. It is further noted that NL-A 8802323 describes pharmaceutical preparations with water-insoluble peptide derivatives such as pamoates, tannates and stearates of water-soluble peptides. A long-term release is possible. For the preparation, the insoluble peptide derivative is dispersed on a solution of a copolymer of lactic acid and glycolic acid according to the explanation in an example. The solvent is evaporated. The resulting particles are extruded after drying, ground and used as an implant.

This invention also relates to preparations with a sustained release of microparticles from a medicament obtained by the method according to the invention, in particular from a hormonally active, water-soluble, somatostatin or a somatostatin analogue, such as octreotide, providing a satisfactory drug plasma level, and, for example, in a biologically decomposable, biocompatible, polymer, for example, in an encapsulating polymer matrix. The polymer matrix can be a synthetic or a natural polymer.

If desired, the sustained-release preparations may be in the form of an implant.

The drug peptides that can be used in the method according to the invention are water-soluble peptides.

The peptides that can be used in the methods and in the formulations of this invention can be a calcitonin such as salmon calcitonin, lypressin and naturally occurring somatostatin and synthetic analogs thereof.

The naturally occurring somatostatin is one of the recommended compounds and is a cyclic tetradecapeptide of the formula Ala-Gly-Cys-Lys-Asn-Phe-Phe-Phe-T rp

I I

Cys-Ser-Thr-Phe-Thr-Lys,

The somatostatin may, for example, exist in free form, salt form or in the form of complexes thereof.

The acetate salt is a recommended salt for such preparations, especially for microparticles that lead to a reduced explosive drug release at the start.

The somatostatin are indicated for use in the treatment of diseases where long-term administration of the drug is to be taken into account, for example diseases with an etiology comprising or associated with an excess of GH secretion, for example treatment of acromegaly, for use in the treatment of gastrointestinal disorders, for example the treatment or prevention of stomach ulcers, enterocutane and pancreaticocutaneous fistulas, irritable gut syndrome, dumping syndrome, aqueous diarrhea syndrome, acute pancreatitis and gastroenteropathic endocrine tumors (for example vipomas, GRFomas, glucagonomas, insulinomas, gastrinomas and carcinomas) tumors), as well as bleeding in the gastrointestinal tract, breast cancer and complications associated with diabetes.

The polymeric carrier can be obtained from biocompatible and biologically decomposable polymers, such as linear polyesters, branched polyesters, which are linear chains that radiate from a polyol portion, e.g., glucose. Other esters are those of polylactic acid, polyglycolic acid, polyhydroxy-40 butyric acid, polycaprolactone, polyalkylene oxalate, polyalkylene glycol esters of acids from the Kreb's cycle, for example the citric acid cycle etc. and copolymers thereof.

The recommended polymers of this invention are the linear polyesters and the branched chain polyesters.

The linear polyesters can be prepared from the α-hydroxycarboxylic acids, for example lactic acid and glycolic acid, by condensation of the ctone dimers, see for example U.S. Pat. No. 3,773,919.

Linear polylactide co-glycolides, which are preferably used according to the invention, suitably have a molecular weight between 25,000 and 100,000 and a polydispersibility Mw / Mn of, for example, between 1.2 and 2.

The branched polyesters which are preferably used according to the invention can be obtained by using polyhydroxy compounds, for example polyol, for example glucose or mannitol, as initiator. These polyol esters are known and described in British Patent Specification GB 2,145,422 B. The polyol contains at least 3 hydroxyl groups and has a molecular weight of at most 20,000, with at least 1, preferably at least 2, for example an average of 3 of the hydroxyl groups of the 55 polyol in the form of ester groups, which contain poly-lactide or co-poly-lactide chains. Typically 0.2% glucose is used to initiate the polymerization. The structure of the branched polyester is star-shaped. The preferred polyester chains in the linear and star-shaped polymer compounds preferably used according to the invention are copolymers of the α-carboxylic acid portions, lactic acid and glycolic acid, or of the lactone dimers. The molar ratios of lactide: glycolide is about 75:25 to 25:75, for example 60:40 to 40:60, with 55:45 to 45:55, for example 55:45 to 50:50, being the most recommended.

The star-shaped polymers can be obtained by reacting a polyol with a lactide and preferably also a glycolide, at an elevated temperature and in the presence of a catalyst which makes a ring-opening polymerization feasible.

It has been found that an advantage of the star-shaped polymer in the compositions of the present invention is that its molecular weight can be relatively high, thereby imparting physical stability, e.g., a certain hardness, to implantations and microparticles, thereby giving them to sticking together is avoided, although relatively short polylactide chains are present, leading to a controllable biological decomposition rate of the polymer ranging from a few weeks to 1 or 2 months and to a corresponding, delayed release of the peptide, making a depot preparation thereof suitable, for example for a one-month issue.

The star-shaped polymers preferably have an average molecular weight Mw in the range of about 10,000 to 200,000, preferably 25,000 to 100,000, in particular 35,000 to 60,000, and a polydispersibility of, for example, 1.7 to 3.0, for example 2.0 to 2.5. The intrinsic viscosities of star-shaped polymers with Mw 35,000 and Mw 60,000 are 0.36 and 0.51 dl / g in chloroform, respectively.

A star-shaped polymer with an Mw 52,000 has a viscosity of 0.474 dl / g in chloroform.

The terms "microsphere, microcapsule and microparticle" are interchangeable with regard to the invention and indicate the encapsulation of the peptides by the polymer, preferably with the peptide divided by the polymer, which is then a matrix for the peptide. In that case, the term "microbol" or more general "microparticle" is preferably used.

Using the phase separation method of the present invention, the compositions of this invention can be prepared, for example, by dissolving the polymeric carrier material in a solvent that is not a solvent for the peptide, followed by addition and dispersion of a solution of the peptide in the polymer-solvent product. A phase inducer, e.g., a silicone fluid, is then added to induce encapsulation of the peptide by the polymer (cf. U.S. Patent No. 4,675,189).

The effect of the explosive release of the drug can be considerably reduced by ultrafine drug particles precipitating in situ preparation by adding a drug solution to the polymer solution, prior to phase separation.

The therapeutic duration of the release of the peptide can be extended by hardening the microparticles with an O / W emulsion of aqueous buffer heptane. The method known from the state of the art involves a hardening step after which no washing is carried out or which are washed with, for example, heptane and / or isopropanol (FR-A 2400950) and which will ultimately be followed by a separate, possibly containing, aqueous washing step too.

An oil-in-water type emulsion (= ° / w) is used for washing and curing the microspheres and for removing non-encapsulated peptide. The wash promotes removal of the non-encapsulated peptide from the surface of the microspheres. Removing the excess peptide from the microspheres reduces the initial drug explosion, which is characteristic of many conventional encapsulation preparations.

The emulsion also promotes the removal of residual polymer solvent and any silicone fluid.

The O / W emulsion can be prepared using an emulsifier, such as sorbitan monooleate (Span 80 ICI Corp.) or the like, to form a stable emulsion. The emulsion (aqueous phase) can be buffered with a buffer that is not harmful to the peptide and the polymer matrix material. The buffer can have a pH between 2 and 8, with a pH of 4 being recommended. The buffer can be prepared from acidic buffers, such as a phosphate buffer and acetate buffer.

The emulsion may contain dispersants, such as silicone oil, thereby avoiding aggregation of the dry particles of microcapsules due to static electricity and promoting the reduction of the residual solvent content.

A recommended emulsion may contain heptane, pH 4 formate buffer, silicone oil, and sorbitan monooleate.

Examples of the solvent for the polymer matrix material include methylene chloride, chloroform, benzene, and ethyl acetate. The peptide is preferably dissolved in an alcoholic solvent, for example methanol, which is miscible with the polymer solvent.

The phase inducers (coacervatives) are solvents that are miscible with the 19502727. polymer-drug mixture and which cause the embryonic microcapsules to form before curing; silicone oils are the recommended bag and inducers.

The O / W emulsion can be prepared in a conventional manner using heptane and hexane as an organic tase.

Suitably the compositions according to the invention are prepared or manufactured under aseptic conditions.

The compositions obtained according to the method according to the invention can be used in depot form, for example as injectable microspheres or implants.

They can be administered in a conventional manner, for example subcutaneously or by intramuscular injection, for example for indications known for the medicine contained therein.

The sustained-release preparations containing octreotide can be administered for all known indications of the octreotide or derivatives thereof, for example those described in GB 2,199,829 A, pages 89-96, as well as for acromegaly and breast cancer.

The microparticles obtainable according to the present invention may have a size ranging in diameter from 1 to 250 microns, preferably from 10 to 200, especially 10 to 130 microns, for example from 10 to 90 microns. Implants may, for example, have a size of 1 to 10 mm 3. The amount of peptide present in the composition depends on the desired daily dose being delivered and thus on the biological decomposition rate of the encapsulating polymer. The precise amount of peptide can be determined by bioavailability studies. The compositions may be peptide in an amount of at least 0.2, preferably 0.5 to 20% by weight, relative to the polymer matrix, preferably 2.0 to 10, in particular 3.0 to 6, weight%. %.

The release time of the peptide from the microparticle can be 1 to 2 weeks to about 2 months.

Suitably, the sustained-release preparation contains a somatostatin, e.g., octreotide, in a biologically decomposable, biocompatible, polymeric carrier which, administered subcutaneously at a dose of 10 mg of somatostatin per kg body weight of the animal to a rat, has a concentration of a somatostatin in the blood plasma of at least 0.3 ng / ml and preferably less than 20 ng / ml over a 30-day period or suitably a 60-day period.

It is also possible that the sustained-release preparation contains a somatostatin, for example octreotide, in a biologically decomposable, biocompatible, polymeric carrier which, intramuscularly administered to a rabbit at a dose of 5 mg / kg body weight, has a concentration of somatostatin of at least 0.3 ng / ml over a 50-day period and suitably a concentration of at most 20 ng / ml.

0_ Phase separation method

Rabbit 5 mg somatostatin / kg, intramuscular delay (0-42 days) 76% average plasma level (cp, ideal) (0-42 days) 4 ng / ml AUC (0-42 days) 170 ng / mlxdays 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2

The invention thus provides somatostatin, preferably octreotide and octreotide analogous compositions, having the following 3 properties: 1. a delay of at least 70%, preferably at least 74%, for example at least 75%, 80%, 5 88% or at least 89% over a period of 0 to 42 or 43 days, and / or 6 2. an average plasma level (Cp ideal) of 2.5-6.5, preferably 4-6.5 ng / ml during a period 7 from 0 to 42 days, in rats, if 10 mg of somatostatin is administered subcutaneously and / or an average plasma level of 3.5-6.5, for example 4-6.5 ng / ml over a period of 0 to 42 or 43 days 9 in a rabbit if 5 mg of somatostatin is administered intramuscularly, and / or 3. an AUC over a period of 0 to 42 days of at least 160, preferably from 170-230 11

ng / ml x days for a rat, if 10 mg of somatostatin is administered subcutaneously and / or an AUC

12 for a period of 0 to 42 or 43 days of at least 160, preferably of 180-275, for example 13 of 200 to 275 ng / ml x days for a rabbit, if 5 mg of somatostatin is administered intramuscularly.

15

For the quantitative characterization of the above-described sustained-release preparations 16, use is made of the method of surface deviation (AD) of F. Nimmerfall and J. Rosenthaler; Internal. J. Pharmaceut. 32, 1-6 (1986). Briefly, according to the AD method, the surface deviations of the experimental plasma profile of an ideal profile that a constant average plasma level (= 195027)

Cp (ideal) obtained by converting the experimental area under the plasma mirror time curve (AUC) into a rectangle with the same area calculated. The percentage of delay is calculated from the percentage surface deviation (indicated by AUC) as follows:% delay = 100 x (1 - AD / AUC).

According to this method the complete plasma profile is determined during a preselected time period characterized by a single number index.

In Proc. natl. Acad.Sci.USA 85 (1988) 5688-5692 in Figure 4 is a plasma mirror profile of the octapeptide analogous to somatostatin of formula * * D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-N H2 in rats.

However, a clear comparison cannot be made with the plasma level values of the compositions according to the invention in rats, as mentioned above, since the described plasma level profile is based on a different administration method (intramuscular injection) and, more importantly, the loading level of the microcapsutes (between 2 and 6%) and the dosage amount for administration (25 to 50 mg portions of microcapsules for 30 days, although determinations were made for at least 45 days) are not accurately indicated. In addition, the type of poly (DI-lactide-coglycolide) used is not precisely described.

The following examples illustrate the invention.

The Mw of the polymers is the average molecular weight determined according to GLPC using polystyrene as standard.

EXAMPLE 1

1 g of poly (D, L-lactide-co-glycolide) (50/50 molar, Mw 45,000; polydispersity ca. 1.7) was dissolved in 15 ml of methylene chloride with magnetic stirring, after which 75 mg of octreotide acetate were dissolved in 0.5 ml of methanol. Then 15 ml of silicone oil (Dow 360 Medical Fluid 1000 cs brand) (silicone fluid) was added to the polymer peptide mixture. The resulting mixture was added to a stirred emulsion containing 400 ml of n-heptane, 100 ml of pH 4 phosphate buffer, 40 ml of Dow 360 Medical Fluid, 350 cs and 2 ml of Span 80 (emulsifier). Stirring was then continued for a minimum of 10 minutes. The resulting microparticles were recovered by filtration under reduced pressure and were dried overnight in a vacuum oven. The yield was about 90% of microparticles with a size of 10-40 microns.

The microparticles were suspended in a carrier and administered intramuscularly at a dose of 4 mg octreotide to New Zealand rabbits. Blood samples were taken periodically with plasma levels of 0.5 to 1.0 ng / ml measured for 30 days, measured by radioimmunoassay (RIA) analysis.

EXAMPLE 2

1 g of poly (DL-lactide-co-glycolide) glucose (Mw = 45,000) (55/45 molar) obtained according to the method of British Patent Specification 2,145,422 B, polydispersibility of 1.7 prepared from 0.2 was dissolved (40% glucose) with magnetic stirring in 25 ml of ethyl acetate, after which 75 mg of octreotide dissolved in 3 ml of methanol were added. Then 25 ml of silicone oil (Dow 360 Medical Fluid brand, 1000 cs) was added to the polymer peptide mixture. The resulting mixture was added to the emulsion described in Example 1. The mixture was then stirred for a minimum of 10 minutes. The resulting microparticles were recovered by vacuum filtration and dried overnight in a vacuum oven. The yield was greater than 45 80% microparticles in the range of 10-40 microns.

The microparticles were suspended in a carrier and administered intramuscularly at a dose of 4 mg octreotide to white New Zealand rabbits. Blood samples were taken periodically to show that plasma levels were between 0.5 and 2 ng / ml for 21 days, measured with RIA. 1 2 3 4 5 6 EXAMPLE 3 2

A solution of 1.5 g of octreotide acetate in 20 ml of methanol was added with stirring to a solution of 18.5 g of poly (D, L-lactide-co-glycolide) glucose (50:50 molar, molecular weight 45,000) in 500 ml of 4 methylene chloride. Phase separation was performed by adding 500 ml of Dow 360 Medical Fluid 5 (1000 cs) and 800 ml of Dow 360 Medical Fluid (350 cs) to the peptide polymer suspension. The resulting mixture was added to a stirred emulsion consisting of 1800 ml of n-heptane, 2000 ml of sterile water and 40 ml of Span 80. After stirring for 10 minutes, the microspheres were collected by filtration under reduced pressure.

Claims (3)

7 195027. Half of the product was dried in a vacuum oven at 37 ° C. The level of residual methylene chloride was 1.2%. The other half of the product was washed by stirring with 1000 ml of ethanol containing 1 mg of Span 80. After stirring for 1 hour, the ethanol was decanted and the microparticles were stirred for 1 hour with 1000 ml of n-heptane containing 1 ml of Span 80. After stirring for 1 hour, the microparticles were collected by filtration under reduced pressure and dried overnight at 37 ° C in a vacuum oven. The residual methylene chloride level of the microparticles washed in this way was lowered from 1.2% to 0.12%. The combined yield of the product was 18.2 g (91%) of microparticles containing 5.6% octreotide, with an average diameter of 24 microns and 1.5% residual heptane. The microparticles were suspended in a carrier and administered intramuscularly at a dose of 5 mg / kg dose of octreotide to white rabbits. Blood samples were taken periodically, showing that plasma levels were between 0.3 and 7.7 ng / ml for 49 days, measured with RIA. EXAMPLE 4 A solution of 1 g of poly (D, L-lactide co-glycolide) (50:50) molar, molecular weight 36,100) in 20 ml of methylene chloride was added with stirring to a solution of 100 mg of calcitonin in 1.5 ml of methanol . The phase separation was performed by adding 20 ml of silicone fluid (Dow 360 Medical Fluid, 1000 cs). The resulting mixture was added to a stirred emulsion consisting of 100 ml of pH 4 phosphate buffer, 400 ml of n-heptane, 4 ml of Span 80 and 40 ml of silicone fluid (Dow 360 Medical Fluid. 1000 cs). After stirring for 10 minutes, the microspheres were collected by filtration under reduced pressure and dried overnight at 37 ° C in a vacuum oven. The yield was 1.1 g of microspheres containing 5.9% calcitonin. COMPARATIVE EXAMPLE A solution of 9.9 g of poly (D.L-lactide-co-glycolide) (50:50) molar, Mw = 44,300) in 140 ml of methylene chloride was added to 100 mg of lypressin. The dispersion was magnetically stirred for one hour before 140 ml of silicone fluid (Dow 360 Medical Fluid, 1000 cs) and 2.5 ml of Span 80 were added. The mixture was added to 2000 ml of heptane and stirred for 10 minutes. The resulting microcapsules were collected by filtration under reduced pressure, washed three times with heptane and dried for 10 minutes with suction. Half of the sample was washed by stirring in water for 10 minutes and the other half was not washed. Both samples were dried overnight in a vacuum oven at 30 ° C. The total yield was 10.65 g of microcapsules. Analysis of the washed sample was 0.5% lypressin and 0.6% for the sample that had not been washed with water. A method for preparing a microparticle containing a water-soluble peptide drug in a biodegradable, biocompatible polymeric carrier, comprising the steps of: a) dissolving the polymeric carrier material in a suitable solvent in which the drug peptide is insoluble is, b) adding and dispersing a solution of the drug peptide in a suitable solvent, which is not a solvent for the polymer in the solution of step a), 45 c) adding a phase inducing agent to the dispersion of step b) for the inducing the formation of microparticles, d) adding a liquid to the mixture of step c), or adding the mixture of step c) to a liquid for curing and washing the microparticle, and e) recovering the microparticle, 50 characterized in that the liquid is an oil-in-water emulsion.