Microspheres having a physiological active substance uniformly dispersed therein and sustained-release preparations containing the same

Abstract

The present application relates to microspheres having a physiologically active substance uniformly dispersed therein and sustained-release preparations containing the same. In the present application, microspheres are provided, which are microspheres having a physiologically active substance uniformly dispersed therein with a lactic acid / glycolic acid copolymer (PLGA) as a main component, characterized in that the average volume-based particle diameter of the microspheres is 1 μm or more and 150 μm or less, and no lump or pore of the physiologically active substance of 1.5 μm or more is present in the microspheres. The microspheres of the present application can appropriately control the initial release amount of the physiologically active substance and the release rate during the period thereafter, and continuously release the physiologically active substance in vivo for a certain period.

Description

[0001] This application is a divisional application of Chinese patent application No. 202080100594.7, filed on May 8, 2020, entitled “Microspheres uniformly dispersed with physiologically active substances and sustained-release formulations containing the same”. Technical Field

[0002] This invention relates to microspheres uniformly dispersed with physiologically active substances and sustained-release formulations containing them. In particular, this invention relates to microspheres uniformly dispersed with physiologically active substances, with lactic acid / glycolic acid copolymer (PLGA) as the main component, and sustained-release formulations containing them. Background Technology

[0003] Microspheres or nanospheres have recently attracted much attention as sustained-release formulations containing physiologically active substances, such as pharmaceuticals. Microspheres generally refer to formulations with a particle size of approximately 1 μm to 150 μm, while formulations smaller than 1 μm are called nanospheres. They can, for example, encapsulate physiologically active substances within biodegradable synthetic or natural polymers, enabling localized and sustained release of these substances, or they can target physiologically active substances to tissues.

[0004] In sustained-release microsphere formulations that slowly release physiologically active substances at a certain rate, such as formulations requiring appropriate control of biodegradable polymers, physiologically active substances, additives, and solvents, it is necessary to appropriately control the initial release amount and subsequent release rate of the physiologically active substances during a certain period in vivo to ensure their continuous release.

[0005] One of the important factors determining the release rate of this physiologically active substance is the type of biodegradable polymer. In particular, for the most widely used lactic acid-co-glycolide acid (PLGA), the rate of degradation in the body varies depending on its physicochemical properties, such as the ratio of lactic acid to glycolic acid as constituent components, molecular weight, and hydrophilicity. Therefore, the release period can be adjusted to the desired time (Patent Document 1).

[0006] Furthermore, to suppress abnormal initial release of physiologically active substances (initial burst) and control the release rate during the release period to a constant level, the particle size of the microspheres and the dispersion state of the physiologically active substances within the microspheres are involved. While the particle size of the microspheres presents a yield problem, it can be adjusted to the target particle size through operations such as filtration. However, the dispersion state of the physiologically active substances within the microspheres is only considered uniform and has not been confirmed.

[0007] PLGA microspheres can be manufactured using methods such as liquid drying, spray drying, spray freeze drying, drying using supercritical fluid processes, and double emulsification. Among these, the most commonly used method, when the bioactive substance is lipophilic, involves dissolving or dispersing PLGA and the bioactive substance in an organic solvent, mixing it with an aqueous solution containing polyvinyl alcohol (PVA) to emulsify it, and then removing the solvent from the emulsion—a liquid drying method.

[0008] Patent Document 1 discloses a method for manufacturing sustained-release microspheres containing biodegradable polymers such as PLGA and peptide drugs using spray drying, spray freeze-drying, or a drying method employing a supercritical fluid process. However, it does not describe the extent to which the particle size of the sustained-release microspheres fluctuates, whether the peptide drugs are uniformly dispersed in the sustained-release microspheres, or whether a uniform product can be obtained.

[0009] Patent Document 2 discloses a method for manufacturing PLGA microparticles using a liquid-drying method, comprising a mixed solvent consisting of a halogenated hydrocarbon and a non-aqueous mixed organic solvent with a drug solubility of 0.3% (W / V) or higher. Although the particle size (median particle size) of the microparticles obtained in Manufacturing Examples 1 and 2 is described as 14 and 16 μm, the dispersion state of the drug in the microparticles is not described.

[0010] Patent Document 3 discloses PLGA nanoparticles containing bioactive substances. These nanoparticles are primarily used for targeting specific tissues and are therefore nanoparticles of tens to hundreds of nm in size, capable of passing through the tiny pores of capillaries. However, Patent Document 3 does not describe microspheres larger than 1 μm, which are much larger than these nanoparticles. Furthermore, even using the technology in Patent Document 3, those skilled in the art cannot manufacture microspheres with a particle size larger than 1 μm.

[0011] Patent Document 4 discloses a formulation that releases leuprolide acetate, a luteinizing hormone-releasing hormone derivative, via subcutaneous injection for approximately one to several months. This formulation suffers from a very wide particle size distribution, ranging from 1 μm to 400 μm. Therefore, Patent Document 5 proposes a method for addressing this problem by using a double emulsification process to manufacture microspheres containing physiologically active substances encapsulated within a polymer carrier. However, regarding the leuprolide acetate-containing microspheres obtained in Examples 1-5, the dispersion state of the drug within the particles is not described.

[0012] Patent document 6 discloses microspheres that relieve chronic pain for at least 28 days (672 hours). These microspheres contain a biodegradable polymer and a local anesthetic (a physiologically active substance), with approximately 75% of the local anesthetic released up to approximately 72 hours, and approximately 80-90% released up to approximately 120 hours. This suggests that the distribution of the local anesthetic within the microspheres is uneven and biased towards the outer edges. According to... Figure 2 The SEM (scanning electron microscope) images of the cross-section of the microspheres described in the paper could not determine the dispersion state of the local anesthetic, but confirmed the presence of local anesthetic or pores larger than 1.5 μm.

[0013] Patent Document 7 discloses core-shell structured microspheres, wherein the core contains solid aripiprazole, and the surface of the core is coated with a shell containing a biodegradable polymer. Thus, the microspheres in Patent Document 7 are not microspheres in which physiologically active substances are uniformly dispersed. Furthermore, according to... Figure 5 Electron microscope images of the cross-section obtained by cutting the microspheres obtained in the examples, as described in the document, confirmed that there were pores larger than 1.5 μm.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Application Publication No. 2005-035994

[0017] Patent Document 2: Japanese Patent Application Publication No. 2005-015476

[0018] Patent Document 3: Japanese Patent No. 4856752

[0019] Patent Document 4: Japanese Patent No. 2653255

[0020] Patent Document 5: Japanese Patent Application Publication No. 2014-224114

[0021] Patent Document 6: Japanese Patent Application Publication No. 2016-069378

[0022] Patent Document 7: Japanese Patent Publication No. 2010-531303 Summary of the Invention

[0023] The problem that the invention aims to solve

[0024] For biodegradable polymer microspheres with an average volumetric particle size of 1 μm to 150 μm, the release period cannot be achieved as designed if the distribution and porosity of the bioactive substances within the microspheres are not controlled. For example, if the bioactive substances are concentrated near the surface of the microspheres, a large amount of bioactive substances are released from the microspheres in the initial stage after administration, causing an initial burst of release. Conversely, if the bioactive substances are concentrated in the center of the microspheres, or in a core-shell configuration, sustained release from the initial stage is not possible. Furthermore, a uniform dispersion of the bioactive substances within the microparticles is desirable. Sustained release from the initial stage is impossible in a dispersion state where large amounts of bioactive substances are dispersed. Similarly, the same problem arises in the release of bioactive substances if porosity is not controlled.

[0025] Uniform dispersion of bioactive substances within microspheres is an essential condition for the sustained release of these substances within a living organism over a given period. Because microspheres differ significantly in size from nanoparticles, achieving homogenization is generally difficult. Therefore, it is crucial to confirm the dispersion state of the bioactive substances within the microspheres.

[0026] Figure 1 This is a microscopic photograph of Lipuan (registered trademark), a microencapsulated sustained-release formulation of LH-RH derivatives described in Patent Document 4, for injection at 1.88 mg (manufactured by Takeda Pharmaceutical Company Limited). This formulation contains various particles ranging from large to small, but a particle of approximately 35 μm was selected as representative. The cross-sectional SEM (scanning electron microscope) image of this particle is shown below. Figure 2 The SEM image of PLGA microparticles without physiologically active substances, as used in Reference Example 1, is compared with that of PLGA microparticles. Figure 3 In comparison, Figure 2 The study identified dispersed bioactive substances and pores, including a large number of bioactive substances larger than 2 μm in size. Elemental analysis using EDS (energy-dispersive X-ray spectroscopy) confirmed the presence of either the bioactive substances or the pores. The non-uniform dispersion of bioactive substances within these particles makes it impossible to properly control the release rate during the release process.

[0027] Therefore, the objective of this invention is to provide microspheres that can appropriately control the initial release amount of physiologically active substances and the release rate during the subsequent release period, thereby continuously releasing physiologically active substances in a living organism over a certain period of time.

[0028] Methods for solving problems

[0029] To solve the aforementioned problems, the inventors conducted in-depth research and surprisingly discovered that if the microspheres do not contain clumps or pores of physiologically active substances larger than 1.5 μm, the initial release amount of the physiologically active substances and the release rate during the subsequent release period can be appropriately controlled, allowing for the continuous release of physiologically active substances within the organism for a certain period, thus completing the present invention. That is, the present invention is as follows.

[0030] [1] The first aspect of the present invention is a microsphere, which is a microsphere in which a physiologically active substance is uniformly dispersed and the main component is a lactic acid / glycolic acid copolymer (PLGA), characterized in that the average volume reference particle size of the microsphere is more than 1 μm and less than 150 μm, and there are no blocks or pores of the physiologically active substance with a diameter of more than 1.5 μm in the microsphere.

[0031] [2] The second aspect of the present invention is the microsphere according to [1], wherein there are no blocks or pores of the physiologically active substance larger than 1.0 μm in the microsphere.

[0032] [3] The third aspect of the present invention is the microspheres according to [1] or [2], wherein the average volume reference particle size of the dispersed physiologically active substances is 5 nm to 500 nm.

[0033] [4] The fourth aspect of the present invention is microspheres according to any one of [1] to [3], wherein the physiologically active substance is an lipophilic physiologically active substance.

[0034] [5] The fifth aspect of the present invention is a sustained-release formulation containing microspheres according to any one of [1] to [4].

[0035] The effects of the invention

[0036] The microspheres of this invention allow for appropriate control of the initial release amount of physiologically active substances and the release rate during the subsequent release period, enabling the continuous release of physiologically active substances within a certain period of time in the body. Attached Figure Description

[0037] Figure 1 These are microscope photographs of Lipman (a registered trademark).

[0038] Figure 2 This is a SEM image of a cross-section of a Lipuan (registered trademark) particle of approximately 35 μm.

[0039] Figure 3 The image shown is a cross-sectional SEM image of the microspheres without physiologically active substances in Reference Example 1.

[0040] Figure 4 This is an SEM image of the cross-section of the microspheres in Example 1.

[0041] Figure 5 This is a SEM image of the cross-section of the microsphere in Comparative Example 2.

[0042] Figure 6 This is a SEM image of the cross-section of the microsphere in Comparative Example 3. Detailed Implementation

[0043] 1. Microspheres

[0044] The microspheres of this invention are microspheres in which physiologically active substances are uniformly dispersed, with lactic acid / glycolic acid copolymer (PLGA) as the main component. The microspheres are characterized by an average volumetric particle size of 1 μm or more and 150 μm or less, and the absence of clumps or pores of the physiologically active substances larger than 1.5 μm within the microspheres. Using the microspheres of this invention, the initial release amount of the physiologically active substances and the release rate during the subsequent release period can be appropriately controlled, allowing for the continuous release of physiologically active substances within the organism over a certain period. Furthermore, regarding the absence of clumps or pores of the physiologically active substances larger than 1.5 μm within the microspheres, "clumps" refers to large particles or aggregates of the physiologically active substances, "pores" refers to voids such as bubbles or grooves, and "1.5 μm or more" means that the maximum diameter is 1.5 μm or more in the case of a roughly spherical shape, the long side is 1.5 μm or more in the case of a rectangle, and the maximum length is 1.5 μm or more in the case of a needle-like shape.

[0045] <Observation of the cross-section of microspheres>

[0046] For example, the absence of clumps or pores larger than 1.5 μm or 1.0 μm in the microspheres can be confirmed by observing the cross-section of the microspheres using an electron microscope at a magnification that allows identification of the dispersed bioactive particles. Specifically, the microspheres are first frozen using liquid nitrogen. After freezing, a FIB (Focused Ion Beam) cross-section is prepared. That is, using an FIB device, a focused ion beam is irradiated onto the sample, cutting out the structure at the desired location inside the sample, thereby observing the cross-section of the microspheres. The preferred particle size of the dispersed bioactive particles is several tens to several hundred nm, but the entire cross-section of the microspheres is observed at an electron microscope magnification that allows identification of dispersed particles of this size. Typically, the electron microscope magnification is around 2500x to tens of thousands ofx or higher. Alternatively, in cases where a high magnification is not sufficient to observe the entire microsphere, the observed portions can be connected together to observe the whole. Although the composition varies depending on the bioactive elements, elemental analysis of the microsphere cross-section can be performed using an EDS (Energy Dispersive X-ray Spectrometer).

[0047] <PLGA>

[0048] PLGA is a lactic acid / glycolic acid copolymer having structural units derived from lactic acid and structural units derived from glycolic acid. PLGA may include other biodegradable polymers such as polylactide (PLA) and polyglycolide (PGA). The PLGA described in this specification is an example only and is not limited to the described substance.

[0049] The molar ratio (L:G) of the lactic acid-derived structural unit (L) to the glycolic acid-derived structural unit (G) in PLGA is not particularly limited and can be appropriately selected according to the purpose. It is preferably 1:99 to 99:1, more preferably 25:75 to 99:1, even more preferably 30:70 to 90:10, and particularly preferably 50:50 to 85:15.

[0050] The PLGA used in the microspheres of this invention can be manufactured, for example, by heating and polycondensing lactic acid and glycolic acid under weak reduced pressure using an ion exchange resin as a catalyst. In this case, lactide can also be used instead of lactic acid. PLGA can be a commercially available product. Commercially available products include, for example, those from Fujifilm and Hikari Pure Chemical Industries Co., Ltd., Taki Chemical Co., Ltd., EvonicRohm GmbH, Merck, Sigma-Aldrich, etc.

[0051] The PLGA content in the microspheres of the present invention is not particularly limited and can be appropriately selected according to the purpose. It is preferably 1% by mass or more, more preferably 30% by mass or more and 95% by mass or less, and particularly preferably 50% by mass or more and 90% by mass or less.

[0052] Microspheres

[0053] The microspheres of this invention contain PLGA and physiologically active substances. Further, depending on the requirements, they may contain dispersants and other components. Physiologically active substances, dispersants, and other components are dispersed within the matrix of the microspheres.

[0054] [Physiologically active substances]

[0055] There are no particular limitations on the physiologically active substances contained in the microspheres of the present invention, and they can be appropriately selected according to the purpose. For example, pharmaceutical compounds, functional food compounds, functional cosmetic compounds, etc., can be listed. Microspheres containing pharmaceutical compounds are suitable for use as sustained-release pharmaceutical preparations, for example. The physiologically active substances include either lipophilic or hydrophilic physiologically active substances. Lipophilic physiologically active substances are preferred examples. Lipophilic physiologically active substances refer to substances, for example, with a water / octanol partition coefficient of logP value of 3 or higher. Physiologically active substances not included in lipophilic physiologically active substances are classified as hydrophilic physiologically active substances. The water / octanol partition coefficient can be determined according to the flask shaking method of JIS Z7260-107 (2000). There are no particular limitations on the physiologically active substances as long as they are the substances desired for sustained-release preparations, and they can be appropriately selected according to the purpose. Physiologically active substances also include any form such as salts and hydrates.

[0056] The microspheres of the present invention do not contain any clumps or pores of physiologically active substances larger than 1.5 μm, and preferably, do not contain any clumps or pores of physiologically active substances larger than 1.0 μm. By adopting this structure, the initial release amount of the physiologically active substances and the release rate during subsequent release periods can be appropriately controlled, allowing for the continuous release of physiologically active substances within the organism over a certain period. The content of physiologically active substances relative to the total amount of microspheres can be controlled to ensure that there are no clumps or pores of physiologically active substances larger than 1.5 μm or larger in the microspheres. The preferred content of the physiologically active substances varies depending on the amount of physiologically active substances, and relative to the total amount of microspheres, for example, 0.01 to 2% by mass, preferably 0.1 to 1.5% by mass, and more preferably 0.2 to 1.2% by mass.

[0057] The average volume reference particle size of the dispersed physiologically active substance is preferably 5 nm to 500 nm, more preferably 10 nm to 400 nm, and even more preferably 20 nm to 200 nm.

[0058] [Dispersant]

[0059] To disperse physiologically active substances, dispersants can be used. Dispersants can be low molecular weight dispersants or high molecular weight dispersant polymers. Low molecular weight dispersants refer to compounds with a weight-average molecular weight of less than 15,000, while high molecular weight dispersant polymers refer to compounds with a weight-average molecular weight of more than 15,000, containing repeating covalent bonds between one or more monomers.

[0060] As low molecular weight dispersants, there are no particular restrictions as long as they are permissible dispersants in pharmaceutical compounds, functional food compounds, and functional cosmetic compounds; they can be selected appropriately according to the purpose. Specifically, lipids, sugars, cyclodextrins, amino acids, organic acids, and other components can be listed. They can be used alone or in combination of two or more.

[0061] As lipids, there are no particular restrictions, and appropriate choices can be made according to the purpose. Examples include medium-chain or long-chain monoglycerides, diglycerides or triglycerides, phospholipids, vegetable oils (such as soybean oil, avocado oil, squalene oil, sesame oil, olive oil, corn oil, rapeseed oil, safflower oil, sunflower seed oil, etc.), fish oil, flavoring oils, water-insoluble vitamins, fatty acids and their mixtures and derivatives. One type can be used alone, or two or more can be used in combination.

[0062] As sugars, there are no particular restrictions, and appropriate choices can be made according to the purpose. Examples include glucose, mannose, idole, galactose, fucose, ribose, xylose, lactose, sucrose, maltose, trehalose, maltodextrose, raffinose, maltotriose, acarbose, water-soluble cellulose, synthetic cellulose, sugar alcohols, glycerol, sorbitol, lactitol, maltitol, mannitol, xylitol, erythritol, or polyols, or their derivatives. One type can be used alone, or two or more can be used in combination.

[0063] As for other ingredients, there are no particular restrictions, and appropriate selections can be made according to the purpose, with preference given to ingredients that have been used in medicine in the past.

[0064] <Average volume reference particle size>

[0065] The average volumetric reference particle size of the microspheres of the present invention is 1 μm or more and 150 μm or less, preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 75 μm or less. The average volumetric reference particle size can be measured using a laser diffraction particle size distribution measuring device. In the present invention, if the average volumetric reference particle size exceeds 150 μm, the uneven dispersion of the physiologically active substances within the microspheres will cause initial burst problems, leading to easy aggregation and sedimentation, and making subsequent processing difficult. If it is less than 1 μm, the initial burst problem will be significant.

[0066] The microspheres of this invention allow for appropriate control of the initial release amount of physiologically active substances and the release rate during the subsequent release period, enabling the continuous release of physiologically active substances within a certain period of time in the body.

[0067] 2. Sustained-release formulations

[0068] Using the microspheres of this invention, sustained-release formulations containing microspheres can be prepared. With the sustained-release formulations of this invention, the initial release amount of physiologically active substances and the release rate during the subsequent release period can be appropriately controlled, allowing for the continuous release of physiologically active substances in vivo over a certain period, effectively demonstrating pharmacological effects.

[0069] The sustained-release formulation of the present invention can be administered directly to lesions such as muscles, subcutaneous tissue, blood vessels, organs, joint cavities, and tumors, either as an injection or implant, or as a transdermal agent. It can also be administered in various other formulation forms. For example, to formulate the sustained-release formulation of the present invention into an injection, it can be prepared as an aqueous suspension with dispersants (Tween 80, HCO-60, carboxymethyl cellulose, sodium alginate, etc.), preservatives (methylparaben, propylparaben, etc.), and isotonic agents (sodium chloride, mannitol, sorbitol, glucose, etc.), or dispersed with vegetable oils such as soybean oil, sesame oil, and corn oil to form an oily suspension, thereby producing a sustained-release injection.

[0070] 3. Manufacturing methods for microspheres

[0071] <Microsphere Manufacturing Process>

[0072] The method for manufacturing microspheres of the present invention includes at least a particle formation step, and may further include, as needed, a filtration and sterilization step, a good solvent removal step, and other steps.

[0073] [Particle Formation Process]

[0074] The particle formation process preferably uses a particle formation processing apparatus as described in Japanese Patent Application Publication No. 2009-132871 or Japanese Patent Application Publication No. 2011-189348, which performs particle formation processing between multiple processing surfaces that are arranged in a relatively close or distant manner and at least one of them rotates relative to the other. The particle formation process is carried out, for example, by continuously feeding a solution of PLGA and a physiologically active substance (obtained by dissolving or dispersing PLGA and a good solvent in PLGA) and a solution containing a poor solvent of PLGA into the particle formation apparatus described above, producing emulsified particles, and removing the good solvent from the produced particles to precipitate the microspheres of the present invention. Here, "dispersion" includes: dispersing the physiologically active substance in a solid state in a good solvent of PLGA; emulsifying the physiologically active substance in a good solvent of PLGA; forming a w / o type emulsion containing an aqueous solution of a hydrophilic physiologically active substance and a good solvent of PLGA, etc.

[0075] As for solutions containing PLGA and physiologically active substances, there are no particular restrictions as long as the solutions contain PLGA and physiologically active substances dissolved or dispersed in a good solvent for PLGA; appropriate solvents can be selected according to the purpose. Good solvents are not particularly limited and can be selected appropriately according to the purpose; examples include: halogenated aliphatic hydrocarbons, aliphatic esters, alcohols, ketones, ethers, acetonitrile, etc. Examples of halogenated aliphatic hydrocarbons include dichloromethane, chloroform, carbon tetrachloride, chloroethane, 2,2,2-trichloroethane, etc. Examples of aliphatic esters include ethyl acetate, propyl acetate, butyl acetate, etc. Examples of alcohols with low solubility in water include benzyl alcohol, phenyl alcohol, n-butanol, etc. Examples of ketones include ketones with 3 to 6 carbon atoms (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.). Examples of ethers include ethers with 2 to 6 carbon atoms (e.g., dimethyl ether, methyl ethyl ether, diethyl ether, etc.). From the perspective of the content of physiologically active substances and the purpose of preventing initial outbreaks, solvents with low solubility in water are preferred. Preferred solvents include halogenated aliphatic hydrocarbons, ketones, and mixtures thereof; more preferably, dichloromethane, acetone, and mixtures thereof are also preferred. Furthermore, one or more solvents can be used individually or in combination. Particle size can be controlled by changing the type and amount of solvent used.

[0076] A good solvent refers to a solvent with high solubility for PLGA, while a poor solvent refers to a solvent with low or no solubility for PLGA. Good and poor solvents are selected such that no clumps or pores larger than 1.5 μm of physiologically active substances are formed in the cross-section of the microspheres. Furthermore, good and poor solvents can be defined, for example, by the mass of PLGA that can be dissolved in 100 g of solvent at 25°C. In this invention, a good solvent is preferably one that dissolves 0.1 g or more of PLGA, more preferably 0.2 g or more, and even more preferably 0.5 g or more. A poor solvent is preferably one that dissolves only 0.05 g or less of PLGA, more preferably 0.02 g or less, and even more preferably 0.01 g or less. There are no particular limitations on the poor solvent; it can be appropriately selected according to the purpose, with water being preferred.

[0077] The PLGA content in the solution of PLGA and physiologically active substances can be varied depending on the good solvent, the particle size of the target microspheres, and to ensure that there are no clumps or pores of physiologically active substances larger than 1.5 μm in the cross-section of the microspheres. The PLGA content can be, for example, 1–30% by mass, preferably 3–20% by mass, and more preferably 5–15% by mass. The content of physiologically active substances in the PLGA solution can be appropriately varied depending on the purpose, pharmacological effect, etc., and to ensure that there are no clumps or pores of physiologically active substances larger than 1.5 μm in the cross-section of the microspheres.

[0078] To further ensure the stability of the manufactured microspheres, a stabilizer can be added to the unsuitable solvent. There are no particular limitations on the stabilizer, and it can be appropriately selected depending on the purpose. Examples include polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), lecithin, polysorbate 80, etc., with polyvinyl alcohol (PVA) being preferred. Furthermore, the concentration of the added stabilizer is preferably 0.01 to 20% by mass, more preferably 5% by mass or less. Preferred unsuitable solvents include, for example, aqueous solutions of PVA.

[0079] It is desirable to prepare solutions of PLGA and physiologically active substances, as well as solutions containing undesirable solvents, using apparatuses such as rotary dispersers that rotate stirrers of various shapes (rod-shaped, plate-shaped, propeller-shaped, etc.) within a tank, devices that include screens rotating relative to the stirrers, and rotary dispersers that apply shear force to the fluid to achieve homogeneous mixing. As a preferred example of a rotary disperser, the stirrer disclosed in Japanese Patent No. 5147091 can be used. To prevent the formation of clumps or pores of physiologically active substances larger than 1.5 μm in the cross-section of the microspheres, it is necessary to completely mix the PLGA solution with the undesirable solvent. To achieve complete mixing, homogenization at least at the molecular level is required.

[0080] The rotary disperser can operate intermittently or continuously. In the continuous operation, the supply and discharge of fluid to the mixing tank can be carried out continuously, or a continuous mixer can be used without a mixing tank. Known mixers and mixing methods can be used to appropriately control the mixing energy. It should be noted that the mixing energy is described in detail in the applicant's Japanese Patent Application Publication No. 04-114725. There are no particular limitations on the mixing method used in this invention; various shear-type, friction-type, high-pressure jet-type, ultrasonic-type, and other types of mixers, dissolvers, emulsifiers, dispersers, homogenizers, etc., can be used. As an example, one can list continuous emulsifiers such as Ultra-Turrax (manufactured by IKA), Polytron (manufactured by KINEMATICA), TK homogenizer (manufactured by PRIMIX), Ebara Milder (manufactured by Ebara Seisakusho), TK Homomic Line Flow (manufactured by PRIMIX), colloid mill (manufactured by Kobe Steel Environmental Solutions), THRASHER (manufactured by COKE Industries, Ltd.), Trigonal wet micro-pulverizer (manufactured by Mitsui Miike Chemical Machinery), Cavitron (manufactured by EUROTEC), and FineFlow Mill (manufactured by Pacific Machinery), as well as intermittent or continuous dual-purpose emulsifiers such as CLEARMIX (manufactured by M-Technique) and CLEARMIXDISSOLVER (manufactured by M-Technique). In addition, for mixing processes, it is desirable to use a mixer with high-speed rotating stirring blades, a screen on the outside of the stirring blades, and fluid discharged as a jet from the opening of the screen. In particular, it is desirable to use the CLEARMIX (manufactured by M-Technique) and CLEARMIX DISSOLVER (manufactured by M-Technique) mentioned above.

[0081] In the aforementioned particle processing apparatus, the particle size and particle size distribution of PLGA microparticles can be controlled by adjusting the contact surface pressure when the rotating processing surface stops. The inventors' experiments show that a contact surface pressure of 20 g / cm³ is preferably achieved. 2 ~250g / cm 2 When the contact surface pressure is below 20 g / cm 2 Under certain conditions, the film becomes unstable, and the particle size distribution widens. It is clear that if the contact surface pressure exceeds 250 g / cm³, the film becomes unstable. 2 Then, adjusting the target particle size becomes difficult. More preferably, 50 g / cm³ is listed. 2 ~200g / cm 2 More preferably, 80g / cm 2 ~150g / cm 2 .

[0082] It is preferable to prevent the aggregation of individual microspheres formed by the contact between the solution of PLGA and the physiologically active substance and the solution containing a poor solvent. As a method to prevent aggregation, it is preferable to pre-place the solution containing the poor solvent in the solution discharge recovery tank and slowly stir. Stirring further suppresses microsphere aggregation. For stirring, a rotary disperser is preferred, preferably a CLEARMIX DISSOLVER (manufactured by M-Technique). There are no particular limitations as long as the overall flow is slow. If the stirring is vigorous, the PLGA emulsion particles are broken down, the distribution width increases, and the dispersion state of the physiologically active substance may collapse.

[0083] When the physiologically active substance is lipophilic, the particle formation process can be appropriately performed according to the above description to manufacture microspheres. When the physiologically active substance is hydrophilic, the hydrophilic physiologically active substance can be dispersed in a good solvent of PLGA using, for example, a dispersant, and the particle formation process can be performed in the same way to manufacture microspheres.

[0084] Alternatively, when the physiologically active substance is a hydrophilic physiologically active substance, a w / o emulsion can be prepared by dissolving the hydrophilic physiologically active substance together with a desired stabilizer in an aqueous solvent such as water, and mixing it with a solution obtained by dissolving PLGA in a good solvent for PLGA. This w / o emulsion is then used as a solution of PLGA and the physiologically active substance, and the particle formation process described above is performed using the particle formation apparatus described above. In the preparation of the w / o emulsion, methods using intermittent oscillation, a mixer employing a propeller-type mixer or a turbine-type mixer, a colloid mill, a homogenizer, or an ultrasonic irradiation method can be used. Using the particle formation apparatus described above, a solution of PLGA and the physiologically active substance, which is the w / o emulsion, and a solution containing a poor solvent for PLGA are continuously added to produce emulsion particles as a w / o / w emulsion. The good solvent is removed from the produced particles, thereby causing the microspheres of the present invention to precipitate out. The microspheres can be used directly, or excipients (mannitol, sorbitol, lactose, glucose, etc.) can be added, and after redispersing, they can be freeze-dried or spray-dried to solidify. When using these solidified microspheres, a more stable sustained-release injection can be obtained by adding distilled water for injection or a suitable dispersion medium.

[0085] [Filtration and sterilization process]

[0086] As needed, prior to the particle formation process, it is preferable to sterilely filter the prepared solutions of PLGA and physiologically active substances, as well as solutions containing undesirable solvents. Solutions containing undesirable solvents can be sterilized by filtration using a hydrophilic filter, while solutions of PLGA and physiologically active substances can be sterilized by filtration using a hydrophobic filter. The pore size of the filter used for filtration is preferably 0.1 μm to 0.45 μm, more preferably 0.2 μm.

[0087] There are no particular limitations on the aforementioned sterilization filters; they can be appropriately selected depending on the purpose. For example, hydrophilic filters such as polyvinylidene fluoride (PVDF) and polyethersulfone can be used for sterilization filtration of solutions containing undesirable solvents. Hydrophobic filters such as polytetrafluoroethylene (PTFE) can be used for filtration and sterilization of solutions containing PLGA and physiologically active substances. The materials listed herein are not limited to those described herein; selection should be based on the drug's adsorption and the type of solvent.

[0088] [Good Solvent Removal Process]

[0089] In the good solvent removal process, the good solvent is removed from the emulsion particles containing PLGA and the physiologically active substance. Regarding the good solvent removal process, there are no particular limitations as long as the good solvent can be removed from the liquid containing the emulsion particles in a manner that does not create clumps or pores of physiologically active substance larger than 1.5 μm in the cross-section of the microspheres. The appropriate method can be selected according to the purpose. For example, methods such as evaporating the good solvent from the liquid by stirring and heating the liquid, flowing a gas such as nitrogen to the surface of the liquid, or depressurizing the liquid can be cited. In order to prevent the formation of clumps or pores of physiologically active substance larger than 1.5 μm or larger in the microspheres, rapid removal of the good solvent is preferred. The time for removing the good solvent can be, for example, 30 minutes to 12 hours, preferably 1 to 10 hours, and more preferably 2 to 8 hours.

[0090] [Other processes]

[0091] Other steps may include, for example, solvent composition preparation, classification, and particle washing. Typically, the classification process removes coarse and fine powders, but the particles manufactured in this invention generally do not require classification. However, for safety reasons, a classification process may be included.

[0092] The above manufacturing method can produce microspheres in which there are no blocks or pores of physiologically active substances larger than 1.5 μm in the cross-section of the microspheres.

[0093] Example

[0094] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments in any way.

[0095] (See Example 1 for reference)

[0096] In Reference Example 1, microspheres (PLGA microparticles) free of physiologically active substances were manufactured. Using the microspheres of Reference Example 1 as an indicator, the cross-sections of the microspheres of the Examples and Comparative Examples were observed by SEM images, thereby confirming the dispersion state of the physiologically active substances in the microspheres of the Examples and Comparative Examples as follows.

[0097] <Preparation of PLGA solution and PVA aqueous solution>

[0098] Dichloromethane (manufactured by Kanto Chemical) was added to the lactic acid / glycolic acid copolymer (Resomer RG504, manufactured by Evonik) at a concentration of 13% by mass, and dissolved using a high-speed rotary disperser CLEARMIX DISSOLVER (manufactured by M-Technique) to obtain a PLGA solution. The solution was then filtered through a 0.2 μm aeration filter. Filtering was performed using 62 (Merck manufactured). Polyvinyl alcohol (PVA, EG-40P, manufactured by Nippon Synthetic Chemical Industry) was added to ion-exchanged water at a concentration of 1.5% by mass, and dissolved using a high-speed rotary disperser CLEARMIX (M-Technique manufactured) to obtain an aqueous PVA solution. This solution was then filtered through a hydrophilic PVDF membrane filter (…). 47 (Merck manufactured) is filtered. An aqueous PVA solution is pre-placed in a tank for recovering PLGA emulsion particles and stirred to the extent that the liquid level shifts.

[0099] <Preparation of Microspheres (PLGA Microparticles)>

[0100] As a particle forming process, the prepared PLGA solution and PVA aqueous solution are mixed using the particle formation processing apparatus described in Japanese Patent Application Publication No. 2011-189348. Here, the particle formation processing apparatus described in Japanese Patent Application Publication No. 2011-189348 is the apparatus shown in Figure 25 of that publication, where the second inlet d20 is a concentric annular shape surrounding an opening at the center of the processing surface 2, which is a ring-shaped disk, and the diameter of the disk is 75 mm. Specifically, the prepared PVA aqueous solution is introduced into the processing surfaces 1 and 2 from the first inlet section d1 at a rate of 0.02 MPaG, 65 mL / min, and 30°C. While the processing section 10 is rotated at 2000 rpm, the prepared PLGA solution is introduced into the processing surfaces 1 and 2 from the second inlet section d2 at a rate of 0.65 MPaG, 20 mL / min, and 30°C. The PVA aqueous solution and PLGA solution are mixed in a forced film, and PLGA emulsion particles containing dichloromethane are produced in the processing surfaces 1 and 2. The fluid containing the PLGA emulsion particles in the processing surfaces 1 and 2 (hereinafter referred to as the PLGA emulsion particle dispersion) is discharged from the processing surfaces 1 and 2 of the particleization processing apparatus. The PLGA emulsion particle dispersion is recovered to a recovery tank via the outer shell 61 for capturing the discharged PLGA emulsion particle dispersion.

[0101] Next, as a desolventizing process, the above-mentioned effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while argon gas was injected onto the liquid surface. Dichloromethane was removed over 3.5 hours, yielding a suspension containing PLGA microparticles (PLGA microparticle suspension). The average volumetric reference particle size of the obtained PLGA microparticles was 34.0 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed. Figure 3 ).

[0102] like Figure 3 As shown, it was confirmed that there were no physiologically active substances or pores in the aforementioned FIB cross-section. Furthermore, it can be seen that the cross-section of the microspheres in Reference Example 1 can be used as an indicator in observing the cross-sections of the microspheres in the Examples and Comparative Examples.

[0103] (Example 1)

[0104] <Preparation of solutions of PLGA and physiologically active substances and aqueous solutions of PVA>

[0105] A solution of PLGA and the physiologically active substance was obtained by dissolving a lactic acid / glycolic acid copolymer (Resomer RG504, manufactured by Evonik) at 13% by mass and progesterone (manufactured by Fujifilm and Koichi Pharmaceuticals, for cell biochemistry) at 1.0% by mass in dichloromethane (manufactured by Kanto Chemical) using a high-speed rotary disperser, CLEARMIX DISSOLVER (manufactured by M-Technique). The solution was then filtered through a 0.2 μm aeration filter. 62 (Merck manufactured) was filtered. The PVA aqueous solution was prepared in the same manner as in Reference Example 1. The PVA aqueous solution was pre-placed in a tank containing emulsion particles for recovering PLGA and physiologically active substances, and stirred to the extent that the liquid surface moved.

[0106] <Preparation of Microspheres>

[0107] As a particle forming process, similar to Reference Example 1, the particle forming apparatus described in Japanese Patent Application Publication No. 2011-189348 was used to mix the prepared PLGA and physiologically active substance solution with the PVA aqueous solution. Specifically, the prepared PVA aqueous solution was introduced from the first inlet section d1 into the space between processing surfaces 1 and 2 at 0.02 MPaG, 65 mL / min, and 30°C. While the processing section 10 was rotated at 2000 rpm, the prepared PLGA and physiologically active substance solution was introduced from the second inlet section d2 into the space between processing surfaces 1 and 2 at 0.65 MPaG, 20 mL / min, and 30°C. The PVA aqueous solution and the PLGA and physiologically active substance solution were mixed in a forced film, and emulsion particles containing dichloromethane of PLGA and physiologically active substances were produced between processing surfaces 1 and 2. The fluid containing emulsion particles of PLGA and physiologically active substances (hereinafter referred to as the PLGA and physiologically active substance emulsion particle dispersion) between the processing surfaces 1 and 2 of the particle processing device is discharged. The PLGA and physiologically active substance emulsion particle dispersion is recovered to the recovery tank via the shell 61 for capturing the discharged PLGA and physiologically active substance emulsion particle dispersion.

[0108] Next, as a desolventizing process, the above-mentioned effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while argon gas was injected onto the liquid surface. Dichloromethane was removed over 3.5 hours, resulting in a suspension containing microspheres (microsphere suspension). The average volumetric reference particle size of the obtained microspheres was 35.5 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed. Figure 4 ).

[0109] like Figure 4As shown, it was confirmed that there were no blocks or pores of physiologically active substances larger than 1.5 μm in the above-mentioned FIB cross section, and the physiologically active substances were uniformly dispersed in the microspheres as particles of 0.1 μm to 0.22 μm.

[0110] (Example 2)

[0111] Similar to Example 1, as a particle formation step, an emulsion particle dispersion of PLGA and the physiologically active substance was prepared. Next, as a desolventizing step, the recovered effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while argon gas was flowing through it for 8 hours to remove dichloromethane, resulting in a suspension containing microspheres (microsphere suspension). The average volume-based particle size of the obtained microspheres was 35.3 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed.

[0112] Based on the observation of the SEM image, it was confirmed that there were no blocks or pores of physiologically active substances larger than 1.5 μm in the aforementioned FIB cross section, and that the physiologically active substances were uniformly dispersed in the microspheres as particles ranging from 0.1 μm to 0.55 μm.

[0113] (Comparative Example 1)

[0114] Similar to Example 1, as a particle formation step, an emulsion particle dispersion of PLGA and the physiologically active substance was prepared. Next, as a desolventizing step, the recovered effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while dichloromethane was removed from the atmosphere for 15 hours, yielding a suspension containing microspheres (microsphere suspension). The obtained microspheres had an average volume-based particle size of 35.4 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed.

[0115] Based on observations of the SEM image, blocks of physiologically active substances larger than 1.5 μm were confirmed in the aforementioned FIB cross-section. It was confirmed that the physiologically active substances were unevenly dispersed within the microspheres as particles ranging from 0.1 μm to 1.7 μm.

[0116] (Example 3)

[0117] A solution of PLGA and the physiologically active substance was obtained by dissolving a lactic acid / glycolic acid copolymer (Resomer RG504, manufactured by Evonik) at 13% by mass and probucol (manufactured by Fujifilm and Koichi Pharmaceutical, for biochemical purposes) at 0.75% by mass in dichloromethane (manufactured by Kanto Chemical) using a high-speed rotary disperser, CLEARMIX DISSOLVER (manufactured by M-Technique). The solution was then filtered through a 0.2 μm aeration filter. 62 (Merck manufactured) was filtered. The PVA aqueous solution was prepared in the same manner as in Reference Example 1. The PVA aqueous solution was pre-placed in a tank containing emulsion particles for recovering PLGA and physiologically active substances, and stirred to the extent that the liquid surface moved.

[0118] <Preparation of Microspheres>

[0119] As a particle forming process, similar to Reference Example 1, the particle forming apparatus described in Japanese Patent Application Publication No. 2011-189348 was used to mix the prepared PLGA and physiologically active substance solution with the PVA aqueous solution. Specifically, the prepared PVA aqueous solution was introduced from the first inlet section d1 into the space between processing surfaces 1 and 2 at 0.025 MPaG, 50 mL / min, and 30°C. While the processing section 10 was rotated at 1800 rpm, the prepared PLGA and physiologically active substance solution was introduced from the second inlet section d2 into the space between processing surfaces 1 and 2 at 0.6 MPaG, 16 mL / min, and 30°C. The PVA aqueous solution and the PLGA and physiologically active substance solution were mixed in a forced film, and emulsion particles containing dichloromethane of PLGA and physiologically active substances were produced between processing surfaces 1 and 2. The fluid containing emulsion particles of PLGA and physiologically active substances (hereinafter referred to as the PLGA and physiologically active substance emulsion particle dispersion) between the processing surfaces 1 and 2 of the particle processing device is discharged. The PLGA and physiologically active substance emulsion particle dispersion is recovered to the recovery tank via the shell 61 for capturing the discharged PLGA and physiologically active substance emulsion particle dispersion.

[0120] Next, as a desolventizing process, the above-mentioned effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while argon gas was injected onto the liquid surface to remove dichloromethane for 2.0 hours, resulting in a suspension containing microspheres (microsphere suspension). The average volumetric reference particle size of the obtained microspheres was 28.5 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed.

[0121] Based on the observation of SEM images, it was confirmed that there were no blocks or pores of physiologically active substances larger than 1.5 μm in the aforementioned FIB cross section, and that the physiologically active substances were uniformly dispersed in the microspheres as particles ranging from 0.3 μm to 0.7 μm.

[0122] (Example 4)

[0123] A solution of PLGA and the physiologically active substance was obtained by dissolving a lactic acid / glycolic acid copolymer (Resomer RG504, manufactured by Evonik) at 13% by mass and probucol (manufactured by Fujifilm and Koichi Pharmaceutical, for biochemical purposes) at 1.0% by mass, in dichloromethane (manufactured by Kanto Chemical). The solution was then dissolved using a high-speed rotary disperser, CLEARMIX DISSOLVER (manufactured by M-Technique). The solution was then filtered through a 0.2 μm aeration filter. The microspheres (manufactured by Merck, 62) were filtered. Then, the process was repeated in the same manner as in Example 3 to obtain a microsphere suspension. The average volumetric reference particle size of the obtained microspheres was 28.8 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared and SEM images were observed.

[0124] Based on observation of SEM images, it was confirmed that there were no blocks or pores of physiologically active substances larger than 1.5 μm in the aforementioned FIB cross section, and that the physiologically active substances were uniformly dispersed in the microspheres as particles ranging from 0.3 μm to 0.9 μm.

[0125] (Comparative Example 2)

[0126] A solution of PLGA and the physiologically active substance was obtained by dissolving a lactic acid / glycolic acid copolymer (Resomer RG504, manufactured by Evonik) at 13% by mass and probucol (manufactured by Fujifilm and Koichi Pharmaceutical, for biochemical purposes) at 2.0% by mass, in dichloromethane (manufactured by Kanto Chemical). The solution was then dissolved using a high-speed rotary disperser, CLEARMIX DISSOLVER (manufactured by M-Technique). The solution was then filtered through a 0.2 μm aeration filter. 62 (Merck manufactured) was filtered. The PVA aqueous solution was prepared in the same manner as in Reference Example 1. The PVA aqueous solution was pre-placed in a tank containing emulsion particles for recovering PLGA and physiologically active substances, and stirred to the extent that the liquid surface moved.

[0127] <Preparation of Microspheres>

[0128] As a particle forming process, similar to Reference Example 1, the particle forming apparatus described in Japanese Patent Application Publication No. 2011-189348 was used to mix the prepared PLGA and physiologically active substance solution with the PVA aqueous solution. Specifically, the prepared PVA aqueous solution was introduced from the first inlet section d1 into the space between processing surfaces 1 and 2 at 0.025 MPaG, 50 mL / min, and 30°C. While the processing section 10 was rotated at 1800 rpm, the prepared PLGA and physiologically active substance solution was introduced from the second inlet section d2 into the space between processing surfaces 1 and 2 at 0.6 MPaG, 16 mL / min, and 30°C. The PVA aqueous solution and the PLGA and physiologically active substance solution were mixed in a forced film, and emulsion particles containing dichloromethane of PLGA and physiologically active substances were produced between processing surfaces 1 and 2. The fluid containing emulsion particles of PLGA and physiologically active substances (hereinafter referred to as the PLGA and physiologically active substance emulsion particle dispersion) between the processing surfaces 1 and 2 of the particle processing device is discharged. The PLGA and physiologically active substance emulsion particle dispersion is recovered to the recovery tank via the shell 61 for capturing the discharged PLGA and physiologically active substance emulsion particle dispersion.

[0129] Next, as a desolventizing process, the above-mentioned effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while argon gas was injected onto the liquid surface to remove dichloromethane for 2.0 hours, resulting in a suspension containing microspheres (microsphere suspension). The average volumetric reference particle size of the obtained microspheres was 28.9 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed. Figure 5 ).

[0130] like Figure 5 As shown, blocks of physiologically active substances larger than 1.5 μm were confirmed in the aforementioned FIB cross-section. It was confirmed that the physiologically active substances were unevenly dispersed in the microspheres as particles ranging from 0.1 μm to 1.6 μm.

[0131] (Comparative Example 3)

[0132] As part of the particle formation process, similar to Example 4, the emulsion particle dispersion of PLGA and the physiologically active substance was recovered into a recovery tank. Next, as a desolventizing process, the recovered effluent was stirred at a circumferential speed of 4.7 m / s using a CLEARMIX DISSOLVER (manufactured by M-Technique) while dichloromethane was removed from the atmosphere for 36 hours, yielding a suspension containing microspheres (microsphere suspension). The average volumetric reference particle size of the obtained microspheres was 28.6 μm. After freezing representative particles with liquid nitrogen, FIB cross-sections were prepared, and SEM images were observed. Figure 6 ).

[0133] like Figure 6 As shown, blocks of physiologically active substances larger than 1.5 μm were confirmed in the aforementioned FIB cross-section. It was confirmed that the physiologically active substances were unevenly dispersed in the microspheres as particles ranging from 2.0 μm to 4.3 μm, particularly abundant in the surface layer (the outermost shell of the microspheres).

[0134] A portion of the preparation conditions for the microspheres of Examples 1-4 and Comparative Examples 1-3, and the particle size of the prepared microspheres are shown in Tables 1 and 2.

[0135] [Table 1]

[0136]

[0137] As shown in Table 1, the particle size of the physiologically active substances varied with drying conditions and drying time in Examples 1, 2, and Comparative Example 1. Specifically, the particle size of the physiologically active substances was 0.1–0.22 μm in Example 1, which was dried for 3.5 hours under argon jet conditions, but increased to 0.1–0.55 μm in Example 2, which was dried for 8 hours under argon flow conditions. The particles in Comparative Example 1, which was dried for 15 hours under atmospheric conditions, were larger, ranging from 0.1 to 1.7 μm, with some exceeding 1.5 μm. Thus, by controlling the drying conditions and drying time, it is possible to manufacture the microspheres of the present invention, in which there are no clumps or pores of the aforementioned physiologically active substances larger than 1.5 μm within the microspheres.

[0138] [Table 2]

[0139]

[0140] As shown in Table 2, the particle size of the physiologically active substances varied with the content of the physiologically active substances in Examples 3, 4, and Comparative Example 2. Specifically, the particle size was 0.3–0.7 μm in Example 3 (0.75% by mass) but increased to 0.3–0.9 μm in Example 4 (1.0% by mass), and further increased to 0.1–1.6 μm in Comparative Example 2 (2.0% by mass), with particles exceeding 1.5 μm. Additionally, the particle size was larger in Comparative Example 3 (dried for 36 hours under atmospheric conditions), ranging from 2.0 to 4.3 μm, with particles exceeding 1.5 μm. Thus, by controlling the content of the physiologically active substances, it is possible to manufacture the microspheres of the present invention in which there are no clumps or pores of the aforementioned physiologically active substances larger than 1.5 μm within the microspheres.

[0141] Industrial availability

[0142] According to the present invention, microspheres can be provided that can appropriately control the initial release amount of physiologically active substances and the release rate during the subsequent release period, so as to continuously release physiologically active substances in a living organism for a certain period of time.

Claims

1. Microspheres, which are microspheres with a uniform dispersion of physiologically active substances and lactic acid / glycolic acid copolymer (PLGA) as the main component, characterized in that, The microspheres are manufactured by a method comprising the following steps: continuously feeding a solution of PLGA and the physiologically active substance obtained by dissolving or dispersing PLGA and the physiologically active substance in a good solvent of PLGA into a particle formation device, thereby producing emulsion particles; removing the good solvent from the produced emulsion particles, thereby causing the microspheres to precipitate. The content of the physiologically active substance in the solution of PLGA and the physiologically active substance is 0.1% to 1.5% by mass. The average volumetric reference particle size of the microspheres is greater than 1 μm and less than 150 μm. There are no blocks or pores of the physiologically active substance larger than 1.5 μm in the microspheres.

2. The microspheres according to claim 1, wherein, There are no blocks or pores of the physiologically active substance larger than 1.0 μm in the microspheres.

3. The microspheres according to claim 1, wherein, The average volume-based particle size of the dispersed physiologically active substances is 5 nm to 500 nm.

4. The microspheres according to claim 1, wherein, The physiologically active substance is a lipophilic physiologically active substance.

5. The microspheres according to claim 1, wherein, In the manufacturing method, a good solvent is removed by blowing air onto the surface of the liquid containing the emulsion particles.

6. A sustained-release formulation comprising microspheres according to any one of claims 1 to 5.

Images