Method for manufacturing an injectable sustained-release formulation

Abstract

This application provides a method for producing a viscous liquid suspension or emulsion for controlled-release drug delivery, the composition comprising a lactate-based polymer with a weight-average molecular weight between 5,000 and 50,000 daltons, a biocompatible solvent, and a biologically active agent or its salt. The method includes weighing, mixing, and dissolving the ingredients, filtering the product, and degassing the product to produce a uniform formulation that can be accurately filled into a single, ready-to-use syringe.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 217,839, filed Jul. 2, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Technical Field The present invention relates to a method for obtaining an injectable biodegradable delivery system for the sustained release of bioactive substances. More particularly, the present invention relates to a method for producing a viscous liquid suspension or emulsion formulation containing a bioactive substance in a biodegradable polymer solution using a biocompatible solvent, which formulation can be accurately filled into a single ready - to - use syringe.

Background Art

[0003] Biocompatible and biodegradable polymers are increasingly being used as drug delivery carriers to sustainably or delay the release of bioactive substances and provide a long - acting therapeutic effect. This delivery system is available in various injectable depot formulations including solutions, suspensions, emulsions, solid implants, microspheres, microcapsules, and microparticles.

[0004] A sustained-release delivery system using biocompatible and biodegradable polymers is particularly beneficial for highly active drugs with short half-lives. Such delivery systems can reduce the frequency and pain of administration, improve patient compliance, enhance patient convenience, and lower costs. For many bioactive substances, especially hormones, controlled-release delivery systems are highly desirable because they need to be delivered continuously at a controlled rate over long periods. Such systems can be provided by incorporating the bioactive substance into a biodegradable and biocompatible polymer matrix. One approach involves dissolving the polymer in an organic solvent and then removing the solvent to mix it with the bioactive substance, which is then prepared in the form of microparticles, microspheres, microcapsules, microgranules, or solid implants. The bioactive substance is encapsulated within the solid polymer matrix. Several products have been successfully developed using biodegradable polymers in the form of microparticles and solid implants, such as LUPRON DEPOT, Trelstar, and Sandostatin LAR. While these products are effective, they have drawbacks and limitations, such as the large volume of suspension in the case of microparticles and the need for surgical insertion in the case of solid implants like Zoladex. These products are not very user-friendly for users and patients. Furthermore, the manufacturing methods for reproducibly producing sterile products are complex and costly. There is a strong need for compositions that can be easily manufactured and used.

[0005] Another approach involves dissolving biodegradable polymers and bioactive substances in a biocompatible solvent to provide a liquid or fluid composition. When the liquid composition is injected into the body, the solvent dissipates into the surrounding aqueous environment, and the polymer precipitates to form a solid or gel depot from which the bioactive substance is released over a long period. The following documents (Patent Documents 1-28) are considered representative in this field and are incorporated herein by reference. Despite some success, these methods are not entirely satisfactory for the numerous bioactive substances that would be effectively delivered by such approaches. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] U.S. Patent No. 8,173,148 [Patent Document 2] U.S. Patent No. 8,313,763 [Patent Document 3] U.S. Patent No. 6,565,874 [Patent Document 4] U.S. Patent No. 6,528,080 [Patent Document 5] U.S. Reissue Patent No. 37,950 [Patent Document 6] U.S. Patent No. 6,461,631 [Patent Document 7] U.S. Patent No. 6,395,293 [Patent Document 8] U.S. Patent No. 6,355,657 [Patent Document 9] U.S. Patent No. 6,261,583 [Patent Document 10] U.S. Patent No. 6,143,314 [Patent Document 11] U.S. Patent No. 5,990,194 [Patent Document 12] U.S. Patent No. 5,945,115 [Patent Document 13] U.S. Patent No. 5,792,469 [Patent Document 14] U.S. Patent No. 5,780,044 [Patent Document 15] U.S. Patent No. 5,759,563 [Patent Document 16] U.S. Patent No. 5,744,153 [Patent Document 17] U.S. Patent No. 5,739,176 [Patent Document 18] U.S. Patent No. 5,736,152 [Patent Document 19] U.S. Patent No. 5,733,950 [Patent Document 20] U.S. Patent No. 5,702,716 [Patent Document 21] U.S. Patent No. 5,681,873 [Patent Document 22] U.S. Patent No. 5,599,552 [Patent Document 23] U.S. Patent No. 5,487,897 [Patent Document 24] U.S. Patent No. 5,340,849 [Patent Document 25] U.S. Patent No. 5,324,519 [Patent Document 26] U.S. Patent No. 5,278,202 [Patent Document 27] U.S. Patent No. 5,278,201 [Patent Document 28] U.S. Patent No. 4,938,763 [Overview of the Initiative]

[0007] This application discloses a method for obtaining an injectable biodegradable delivery system for sustained release delivery of bioactive substances with improved properties. In formulations having a biodegradable polymer and a biocompatible solvent, by using salts of bioactive substances formed with strong acids, the stability of the formulation is improved, minimizing the generation of impurities associated with the bioactive substance and the undesirable premature degradation of the biodegradable polymer. This improvement in stability allows for an immediately usable formulation that can be stored in a single syringe. It can be directly injected into a patient to form a sustained release depot. However, since this type of formulation is unique, the manufacturing method for this type of formulation is not known. After mixing these materials, it was unexpectedly found that the resulting solution becomes a liquid suspension or emulsion having droplets of the bioactive substance suspended in the biodegradable polymer solution. The size of these droplets varies greatly depending on the manufacturing method, resulting in a non-uniform formulation. Furthermore, air bubbles are generated in the mixing method, and due to the high viscosity and elasticity of the formulation caused by the molecular weight of the polymer and the concentrations of the polymer and the bioactive substance in the formulation, it is difficult to remove them. Also, solubilization of the biodegradable polymer and the bioactive substance generates many micro air bubbles in the resulting viscous suspension or emulsion. In order to accurately measure the filling volume for accurate dosing, most of these air bubbles must be removed before filling the syringe. Therefore, there is a need to develop a method for manufacturing a uniform formulation capable of delivering a bioactive substance from a biodegradable polymer solution that can be immediately used and accurately filled into a single syringe.

[0008] It has been unexpectedly discovered that a formulation prepared by mixing a peptide salt of a strong acid and a biodegradable polymer in a biocompatible solvent is a liquid suspension or emulsion having droplets of a bioactive substance (bioactive substance-rich phase) suspended in a biodegradable polymer solution (polymer-rich continuous phase). These bioactive substance-rich droplets in the polymer solution continuous phase can have different sizes and size distributions depending on the manufacturing method. This variation in droplet size can lead to performance or stability issues with the formulation. Variation in the droplet size distribution can also lead to issues of non-uniformity and dosing inconsistencies. This formulation has a high viscosity and a large amount of air bubbles may be incorporated into the formulation during the manufacturing process, making it difficult to accurately fill into a syringe. Therefore, there is a need for a method of manufacturing this type of formulation that is uniform, stable, can be accurately filled into a single syringe, and is ready for immediate use.

[0009] This application discloses a method for manufacturing a sustained-release formulation that is uniform, stable, and can be filled into a single syringe. This application provides a method of combining a biodegradable polymer, a biocompatible solvent, and a bioactive substance and then degassing and / or filtering the resulting formulation in order to accurately fill the formulation into a syringe and make the syringe ready for immediate use. More specifically, this application discloses a method for manufacturing a single, syringe-ready formulation for the sustained-release delivery of a bioactive substance from a biodegradable polymer composition.

[0010] The method according to this application includes: a) combining a biodegradable polymer and a biocompatible solvent with a bioactive substance; b) degassing the formulation; and c) optionally, filtering the resulting formulation. This method provides a stable and uniform formulation that can be accurately pre-filled into a single syringe and is ready for immediate use.

[0011] The bioactive substances of this application may be in the form of peptides, prodrugs, or salts thereof that can provide biological, physiological, or therapeutic effects. The bioactive substances can be dissolved or suspended in biodegradable polymers and biocompatible solvents to form viscous liquid suspensions or emulsions having a viscosity greater than 10,000 centipoise (cPs). The viscosity may range from 10,000 to 100,000 cPs. Upon injection of the viscous liquid suspension, the bioactive substances are released over time by diffusion and degradation of the implant.

[0012] According to this application, biocompatible solvents can be selected from the group consisting of N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, methoxypolyethylene glycol, alkoxypolyethylene glycol, polyethylene glycol ester, glycoflore, glycerol formal, methyl acetate, ethyl acetate, methyl ethyl ketone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), tetrahydrofuran (THF), caprolactam, decyl methyl sulfoxide, benzyl alcohol, benzyl benzoate, ethyl benzoate, triacetin, diacetin, tributylline, triethyl citrate, tributyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, triethylglyceride, triethyl phosphate, diethyl phthalate, diethyl tartrate, ethyl lactate, propylene carbonate, ethylene carbonate, butyrolactone, and 1-dodecyl azacycloheptan-2-one, as well as combinations thereof.

[0013] According to this application, the biodegradable polymer may be a linear polymer, a branched polymer, or a mixture of the two. Preferably, the polymer is a lactate-based polymer. Lactate-based polymers include homopolymers of lactic acid or lactide monomers (poly(lactic acid) or polylactide, PLA) and copolymers of lactic acid (or lactide) with other monomers (e.g., glycolic acid, glycolide (poly(lactide-co-glycolide), PLG or PLGA)). The weight-average molecular weight of the polymer is typically 5,000 to 50,000. The acid value of the polymer is ideally less than 3 mgKOH / g, preferably less than 2 mgKOH / g, and more preferably less than 1 mgKOH / g.

[0014] When this polymer is formulated with a bioactive substance and a biocompatible solvent, it forms a stable suspension or emulsion that can be pre-filled into a single syringe. According to this application, an injectable composition for controlled-release drug delivery can be produced by a method comprising formulating and mixing raw materials, and then filtering and degassing the product, in order to precisely fill the formulation into a single, ready-to-use syringe.

[0015] According to this application, mixing, filtration, and degassing are carried out under nitrogen, argon, or dry air at room temperature and under controlled humidity of less than 60%, preferably less than 40%. The materials may be mixed in any order, but the mixing time may be minimized and the material aggregation may be prevented while maintaining the product temperature.

[0016] According to this application, the formulation is filtered by applying an inlet pressure of 1 bar to 10 bar and creating a suitable vacuum at the outlet. The vacuum level is -300 mbar to -1000 mbar. The average pore size of the filter is 10 to 150 μm, preferably 20 to 100 μm, and more preferably 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, and 80 μm. The filter can be made from a polymer such as polypropylene or Teflon, or from a metal such as aluminum or stainless steel. The filtration process can be performed before or after the degassing process. Degassing is performed under a final vacuum of 75% to 99.9% or a relative vacuum pressure of -300 mbar to -1000 mbar. Degassing can be performed in stages to minimize the expansion and expansion time of the product, which can affect the uniformity of the product due to viscosity changes during expansion. Degassing yields a product with almost no bubbles, or a product with only a minimal number of bubbles on the surface.

[0017] Specifically, according to one aspect of this application, a method for producing an injectable sustained-release formulation is: i. A compounding process carried out at 15-25°C and under controlled humidity of less than 60%, the compounding process comprising: a) introducing more than 70% of the total amount of NMP into a compounding container; and b) dividing the biodegradable polymer into multiple fractions, adding the first fraction of the biodegradable polymer to the compounding container, mixing the first fraction of the biodegradable polymer with the NMP in the compounding container until the first fraction of the biodegradable polymer is wet or dissolved, then introducing each of the remaining fractions of the biodegradable polymer separately and sequentially into the compounding container, until the newly added fraction of the biodegradable polymer is wet or dissolved before introducing the next fraction of the biodegradable polymer. The process includes: mixing until; a) after all fractions of the biodegradable polymer have dissolved or substantially dissolved, adding the LHRH agonist to the compounding container separately and sequentially in 1 to 20 fractions, and mixing the fractions of LHRH agonist with the NMP and biodegradable polymer in the compounding container until the LHRH agonist is wet or dissolved (where subsequent fractions of LHRH agonist (if any) are added after the LHRH agonist previously added to the compounding container has been wet or dissolved), and mixing the LHRH agonist with the NMP and biodegradable polymer in the compounding container to form a formulation; ii. A degassing process performed by four or more vacuum / venting cycles, in which a relative vacuum pressure between -300 mbar and -1000 mbar is applied to a compounding container or degassing container containing the formulation prepared in (i) above, the vacuum is maintained for a time between 5 minutes and 720 minutes, and the vacuum is released to allow ventilation (wherein the vacuum level maintained in each vacuum / venting cycle is the same as or stronger than the vacuum level maintained in at least the immediately preceding cycle), Includes.

[0018] The formulation may be a viscous suspension or emulsion of an LHRH agonist-rich phase (LHRH / NMP droplets) with a droplet diameter of less than 50 μm and a Dv50, suspended in a biodegradable polymer-rich continuous phase, and having a viscosity greater than 10,000 centipoise (cPs). The injectable sustained-release formulation may contain a luteinizing hormone-releasing hormone (LHRH) agonist or a salt thereof, N-methylpyrrolidone (NMP), and a biodegradable polymer. [Brief explanation of the drawing]

[0019] [Figure 1] This figure shows an image of a 50 mg leuprolide mesylate formulation obtained using an inverted confocal microscope, based on one embodiment of the present invention. [Figure 2] This is a flowchart illustrating a manufacturing method based on an embodiment of the present invention. [Figure 3] This figure shows the formulation of 8% leuprolide mesylate in 58% PLGA / NMP (IV=0.24, MW=19k) after reaching a vacuum pressure of -950mbar directly from -900mbar, according to one embodiment of the present invention. The black lines on the vial indicate the initial filling levels, which were 10%, 25%, 33%, 50%, and 67% from left to right, respectively. [Figure 4] This figure shows that the volume of the formulation under a vacuum of -980 mbar was approximately four times higher than when the formulation was at atmospheric pressure, indicating that a considerable amount of air bubbles remained in the formulation according to one embodiment of the present invention. [Figure 5] This image shows a leuprolide formulation prepared with incomplete mixing, under an inverted confocal microscope. Incomplete mixing results in a formulation that does not have a uniform particle size and can lead to phase separation. [Figure 6] This is an image of a prepared triptorelin formulation under an inverted confocal microscope, showing a triptorelin-rich phase having a droplet size of less than 20 μm suspended in a polymer-rich phase, according to one embodiment of the present invention. [Figure 7] This figure shows an image of goserelin sulfate API under an inverted confocal microscope, based on one embodiment of the present invention. [Modes for carrying out the invention]

[0020] This application provides a method for producing an injectable polymer formulation for sustained-release delivery of a bioactive substance. The injectable polymer composition of this application comprises a) a bioactive substance or a salt thereof, b) a biocompatible solvent, and c) a biodegradable homopolymer or copolymer. The injectable polymer composition can be pre-filled into a single syringe by a specific method of this application. The method includes weighing and mixing the raw materials, as well as filtering and degassing the product, so that the formulation can be accurately filled into a syringe to form a ready-to-use product kit.

[0021] The formulations of this application are in the form of a viscous liquid suspension or emulsion and move as a fluid so that they can be injected through a needle, cannula, tube, laparoscope, probe, or other delivery device. Upon administration to a subject, such injectable composition can form a depot in situ, from which controlled release of a bioactive substance can be sustained for a desired period, depending on the composition. The depot or implant may be solid, gel, paste, semi-solid, or viscous liquid. By appropriately selecting biodegradable polymers and other components, the sustained release period of the bioactive substance can be controlled over a period of several weeks to one year.

[0022] The injectable polymer compositions of this application may also include nonpolymer compounds and / or additives for controlling release, such as release rate regulators, pore-forming agents, plasticizers, organic solvents, encapsulating agents for encapsulating bioactive substances, thermal gelling agents, burst effect reducing materials, hydrogels, polyhydroxyl materials, leaching agents, tissue transporters, or other similar additives, or any combination thereof.

[0023] As used herein, the terms "a," "an," and "one" are to be interpreted as "one or more" and "at least one," respectively.

[0024] Where used herein, all numerical values ​​disclosed herein are approximations, regardless of whether the words “about” or “approximately” are used in the context of this application. Unless otherwise indicated, each numerical value means a range of ±10% of the value. For example, “about 100 mg” or “100 mg” includes any value between 90 and 110 mg.

[0025] As used herein, the term "room temperature" is defined as 15 to 25°C.

[0026] The terms “sustained-release or controlled-release delivery” as defined herein refer to the intended delivery of a bioactive substance in the body over a desired period of time after administration, preferably from at least a few days to one year.

[0027] The term "bioactive substance" means any substance having diagnostic and / or therapeutic properties, including, but not limited to, organic small molecules, inorganic small molecules, polymers, peptides, oligopeptides, proteins, or similar molecules such as enzymes, nucleotides, nucleosides, oligonucleotides, oligonucleotides, oligonucleosides, polynucleotides, polynucleotides, polynucleoacids, or chemical compounds. Non-limiting examples of therapeutic properties include antimetabolic properties, antifungal properties, anti-inflammatory properties, antitumor properties, anti-infective properties, antibiotic properties, nutritional properties, agonist properties, and antagonist properties.

[0028] The physiologically active substance of this application may be in the form of a free molecule, an organic or inorganic salt of a free molecule, may be complexed or covalently bonded with a carrier, may be a prodrug, or may be a polymorphic physiologically active substance (a physiologically active substance consisting of multiple units that are complexed or covalently bonded together).

[0029] As used herein, the term “peptide” has a general meaning that includes poly(amino acids) commonly referred to as “peptides,” “oligopeptides,” and “polypeptides” or “proteins,” and these terms are used interchangeably herein. The term also includes bioactive peptide analogs, derivatives, acylated derivatives, glycosylated derivatives, pegylated derivatives, fusion proteins, etc. The term “peptide” means any bioactive peptide having diagnostic and / or therapeutic properties, including but not limited to antimetabolic properties, antifungal properties, anti-inflammatory properties, antitumor properties, anti-infective properties, antibiotic properties, nutritional properties, agonist properties, and antagonist properties. The term also includes synthetic analogs of peptides, non-natural amino acids with basic functionality, or other forms in which basicity has been introduced.

[0030] Preferred peptides used herein include luteinizing hormone-releasing hormone (LHRH), and LHRH agonists such as leuprorelin or leuprolide, buserelin, gonadrelin, deslorerin, ferirelin, histrelin, lutrelin, goserelin, nafarelin, and triptorelin, as well as antagonists such as cetrorelix, enfuvirtide, thymosin α1, degarelix, and abarelix.

[0031] The bioactive substance used in this application may be the substance itself or a biocompatible organic salt. The acid used to form the biocompatible organic salt of the bioactive substance preferably has a pKa of less than 5. Suitable acids for this application are not limited to these, but include hydrochloric acid, hydrobromic acid, nitric acid, chromic acid, sulfuric acid, methanesulfonic acid, trifluromethanesulfonic acid, trichloroacetic acid, dichloroacetic acid, bromoacetic acid, chloroacetic acid, cyanoacetic acid, 2-chloropropanoic acid, 2-oxobutanoic acid, 2-chlorobutanoic acid, 4-cyanobutanoic acid, pamoic acid, perchloric acid, phosphoric acid, hydrogen iodide, acetic acid, 2,2-dichloroacetic acid, adipic acid, and Luginic acid, L-ascorbic acid, L-aspartic acid, benzenesulfonic acid, benzoic acid, 4-acetamidobenzoic acid, (+)-camphoric acid, (+)-camphor-10-sulfonic acid, capric acid, (decanoic acid), caproic acid (hexanoic acid), caprylic acid (octanoic acid), carbonic acid, cinnamic acid, citric acid, cyclic acid, decanoic acid, dodecyl sulfate, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-Hydro Roxy-ethanesulfonic acid, formic acid, fumaric acid, galactaric acid, gentisic acid, D-glucoheptonic acid, D-gluconic acid, D-glucuronic acid, glutamic acid, glutaric acid, 2-oxoglutaric acid, glycerophosphate, glycolic acid, hypric acid, isobutyric acid, DL-lactic acid, lactobionic acid, lauric acid, maleic acid, (-)-L-malic acid, malonic acid, DL-mandelic acid, gallic acid, naphthalene-1,5- The acid can be selected from the group consisting of disulfonic acid, naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, embonic acid, propionic acid, (-)-L-pyroglutamic acid, salicylic acid, 4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid, (+)-L-tartaric acid, thiocyanic acid, p-toluenesulfonic acid, and undecylenic acid. The selection of an appropriate acid is well known to those skilled in the art.

[0032] The term “strong acid” as defined herein means any acid with a pKa of less than 3, preferably less than 0. Suitable strong acids for this application may be selected from the group consisting of, but are not limited to, hydrochloric acid, hydrobromic acid, nitric acid, chromic acid, sulfuric acid, methanesulfonic acid, trifluromethanesulfonic acid, toluenesulfonic acid (p), trichloroacetic acid, dichloroacetic acid, bromoacetic acid, chloroacetic acid, cyanoacetic acid, 2-chloropropanoic acid, 2-oxobutanoic acid, 2-chlorobutanoic acid, 4-cyanobutanoic acid, pamoic acid, perchloric acid, phosphoric acid, hydrogen iodide, and the like.

[0033] The term “weak acid” as defined herein means any acid with a pKa greater than 3. Suitable weak acids for this application include, but are not limited to, 1-hydroxy-2-naphthoic acid, 2-oxoglutaric acid, 4-acetamidobenzoic acid, 4-aminosalicylic acid, acetic acid, adipic acid, ascorbic acid (L), aspartic acid (L), benzoic acid, camphoric acid (+), capric acid (decanoic acid), caproic acid (hexanoic acid), caprylic acid (octanoic acid), carbonic acid, cinnamic acid, citric acid, formic acid, fumaric acid, galactaric acid, gentisic acid, and glucoheptonic acid (D ), gluconic acid (D), glucuronic acid (D), glutamic acid, glutaric acid, glycolic acid, hypric acid, isobutyric acid, lactic acid (DL), lactobionic acid, lauric acid, maleic acid, malic acid (-L), malonic acid, mandelic acid (DL), oleic acid, oxalic acid, palmitic acid, propionic acid, pyroglutamic acid (-L), salicylic acid, sebacic acid, stearic acid, succinic acid, tartaric acid (+L), thiocyanic acid, undecylenic acid, etc. may be selected from the group.

[0034] Biocompatible organic salts of physiologically active substances can be prepared by simple acid-base titration or neutralization. Biocompatible organic salts of physiologically active substances can be prepared during their synthesis and purification methods. Alternatively, the salt can be prepared from the physiologically active substance in the form of a free base. The free base is dissolved in a suitable liquid medium. The solution of this physiologically active substance is mixed with a solution of acid, and the solvent is removed by suitable means such as filtration, precipitation, or freeze-drying to form a useful salt. If the physiologically active substance is in the form of a commonly available salt, different salts can be obtained using simple salt exchange or ion exchange methods, such as freeze-drying, precipitation, or other methods known in the art. For example, leuprolide acetate is dissolved in a suitable liquid medium, e.g., water. The solution of this peptide is mixed with an aqueous solution of a strong acid such as methanesulfonic acid. When leuprolide acetate and a strong acid such as methanesulfonic acid are dissolved in water, the peptide tends to bind with mesylate ions, as the stronger acid methanesulfonic acid substitutes the weaker acid carvoneacetic acid. The solvent and liberated acetic acid (or other weak but volatile carboxylic acids) may be removed under vacuum. The mixed solution is then freeze-dried to remove water and weak acid, forming the desired salt. If the bioactive substance is unstable at low pH, a biocompatible organic salt of the bioactive substance can be prepared by broad dialysis with very low concentrations of acid.

[0035] The polymer compositions of this application may contain bioactive substances in a range of 0.01 to 40% by weight. Generally, the optimal drug load depends on the desired release period and the potency of the bioactive substance. Clearly, lower potency bioactive substances and longer release periods may require higher levels of incorporation.

[0036] The biocompatible solvents of this application may be miscible or dispersible in aqueous liquids or body fluids. The term “dispersible” means that the solvent is partially soluble or miscible in water. A single solvent or a mixture of solvents may have a water solubility or miscibility of more than 0.1% by weight. Preferably, the solvent has a water solubility or miscibility of more than 3% by weight. More preferably, the solvent has a water solubility or miscibility of more than 7% by weight. A suitable biocompatible solvent can diffuse into a body fluid such that the liquid composition solidifies or becomes solid. Such solvents may be employed alone and / or in mixtures, and the suitability of such solvents can be easily determined by simple experiments.

[0037] Examples of biocompatible solvents, but not limited to these, include N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, methoxypolyethylene glycol, alkoxypolyethylene glycol, polyethylene glycol esters, glycoflore, glycerol formal, methyl acetate, ethyl acetate, methyl ethyl ketone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), caprolactam, decyl methyl sulfoxide, benzyl alcohol, benzyl benzoate, ethyl benzoate, triacetin, diacetin, tributylline, triethyl citrate, tributyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, triethylglyceride, triethyl phosphate, diethyl phthalate, diethyl tartrate, ethyl lactate, propylene carbonate, ethylene carbonate, butyrolactone, and 1-dodecyl azacycloheptan-2-one, as well as combinations thereof. Preferred biocompatible solvents include N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide (DMAC), glycoflore, glycerol formal, benzyl alcohol, benzyl benzoate, methoxypolyethylene glycol, alkoxypolyethylene glycol, polyethylene glycol ester, and isopropylidene glycol.

[0038] The solubility of biodegradable polymers in various organic solvents varies depending on the polymer's properties and its compatibility with the solvent. Therefore, the same polymer may not dissolve to the same degree in different solvents. For example, PLGA is far more soluble in N-methyl-2-pyrrolidone (NMP) than in triacetin. However, when a PLGA solution in NMP is brought into contact with an aqueous solution, NMP diffuses very rapidly due to its high water miscibility, forming a solid polymer matrix. While the rapid diffusion rate of the solvent may lead to rapid formation of a solid implant, it could also result in a high initial burst release. When a PLGA solution in triacetin is brought into contact with an aqueous solution, triacetin diffuses very slowly due to its low water miscibility. The slow diffusion rate of the solvent may mean that it takes a long time for the viscous liquid to transform into a solid matrix. There may be an optimal balance between solvent diffusion and polymer coagulation to encapsulate the peptide substance. Therefore, combining different solvents may be advantageous to obtain a desirable delivery system. By combining solvents with low and high water miscibility, it is possible to improve polymer solubility, alter the viscosity of the composition, optimize diffusion rates, and reduce initial burst release.

[0039] The polymer compositions of this application typically contain a biocompatible solvent in the range of 10% to 99% by weight. The viscosity of the polymer compositions of this application depends on the molecular weight of the polymer and biocompatible solvent used. The viscosity may be in the range of 10,000 to 100,000 cPs. Preferably, the concentration of the polymer in the composition is less than 70% by weight. More preferably, the concentration of the polymer in the composition is less than 60% by weight.

[0040] A polymer is a large molecule, or macromolecule, composed of numerous repeating subunits. Polymers range from familiar synthetic plastics like polystyrene to natural biopolymers that form the basis of biological structures and functions, such as DNA and proteins. Polymers, whether natural or synthetic, are made by the polymerization of numerous small molecules called monomers. Polymerization is a method of covalently bonding numerous small molecules known as monomers into chains or networks. Polymers, with their larger molecular weights compared to small molecules, exhibit unique physical properties such as toughness, viscoelasticity, and a tendency to form glassy and semi-crystalline structures rather than crystalline ones.

[0041] The term "biodegradable" refers to materials that gradually decompose, dissolve, hydrolyze, and / or erode in situ. Generally, "biodegradable polymer" as used herein refers to polymers that are hydrolyzed and / or bioeroded in situ, primarily by hydrolysis and / or enzymatic degradation.

[0042] As used herein, the term “biodegradable polymer” includes any biocompatible and / or biodegradable synthetic and natural polymers that can be used in vivo. Generally, the biodegradable polymers of this application may be linear polymers, branched or star-shaped polymers, or mixtures of linear and branched and / or star-shaped polymers. Preferably, the biodegradable polymers of this application are lactate-based polymers. As used herein, “lactate-based polymer” is a polymer that contains lactate units in the polymer.

[0043] Lactate-based polymers include any homopolymer / copolymer comprising lactate, lactic acid, or lactide monomer. Lactate-based polymers of this application include homopolymers of lactic acid or lactide monomers (poly(lactic acid) or polylactide, PLA), and copolymers of lactic acid (or lactide) with other monomers (e.g., glycolic acid (or glycolide) (poly(lactide-co-glycolide), PLG or PLGA)). Lactate-based polymers may have the same terminal group, such as an ester, hydroxyl, or carboxylic acid; i.e., all terminal groups may be the same. Lactate-based polymers may have mixed terminal groups of ester, hydroxyl, and / or carboxylic acid. Lactate-based polymers may have a diol core with terminal hydroxyl groups, as in the example disclosed in U.S. Patent No. 8,470,359. Similarly, lactate-based polymers may have a triol or polyol core, such as glucose, with terminal hydroxyl groups. Lactate-based polymers may have one terminal group having an ester and the other terminal group having a hydroxyl or carboxylic acid group. Lactate-based polymers may also have one terminal group having a hydroxyl and the other terminal group having a carboxylic acid or ester, or vice versa.

[0044] The lactate-based polymers of this application typically have a weight-average molecular weight of 5,000 to 50,000. These lactate-based polymers may be commercially available or prepared by known methods. The type, molecular weight, and amount of biodegradable polymers present in the composition may affect the length of time that the bioactive substance is released from the controlled-release implant. A higher lactide content in the polymer results in a longer degradation time. A higher molecular weight in the polymer also results in a longer degradation time.

[0045] The lactate-based polymers of this application also include block copolymers such as ABA block copolymers, BAB block copolymers, and / or AB block copolymers and / or branched copolymers. Preferred block copolymers are those in which block A comprises a lactate-based polymer and block B comprises polymers selected from polyglycolides, poly(lactide-co-glycolides), polyanhydrides, poly(orthoesters), polyetheresters, polycaprolactones, polyesteramides, poly(ε-caprolactone), poly(hydroxybutyric acid), and blends and copolymers thereof. Block B may also be polyethylene glycols such as methoxypolyethylene glycol or monofunctional derivatized polyethylene glycols. Some of these combinations form acceptable thermoreversible gels.

[0046] According to this application, lactate-based polymers have a weight-average molecular weight of 5,000-50,000, 5,000-45,000, 5,000-40,000, 5,000-35,000, 5,000-30,000, 5,000-25,000, 5,000-20,000, 5,000-15,000, 5,000-12,000, or 10,000-40,000, or 12,000-35,000, or 15,000-30,000 Daltons.

[0047] The pharmaceutical compositions of this application may contain a lactate-based polymer in an amount ranging from 5% to 75% by weight. The viscosity of the pharmaceutical compositions of this application depends on the molecular weight of the polymer and biocompatible solvent used. The viscosity may range from 10,000 to 100,000 cPs. Generally, when using the same solvent, higher molecular weight and concentration of the polymer result in higher viscosity. This is because it can affect the degassing of the formulation, and trapped air may be more difficult to remove from a higher viscosity formulation. Preferably, the concentration of the polymer in the composition is less than 70% by weight.

[0048] Lactate-based polymers such as poly(lactic acid) or poly(lactide) (PLA), and lactic acid and glycolic acid copolymers (PLGA) comprising poly(D,L-lactide-co-glycolide) and poly(L-lactide-co-glycolide) are preferably used in this application. The thermoplastic polyesters poly(D,L-lactide-co-glycolide) and poly(D,L-lactic acid-co-glycolic acid) can be used interchangeably, and PLGA is used as an abbreviation for both. PLGA has a monomer molar ratio of lactic acid to glycolic acid between about 50:50 and about 99:1, and a weight-average molecular weight between about 5,000 and about 50,000. PLGA preferably has a monomer molar ratio of lactic acid to glycolic acid of about 50:50 (40:60 to 60:40). PLGA more preferably has a lactic acid to glycolic acid monomer molar ratio of about 65:35 (55:45 to 75:25). PLGA more preferably has a lactic acid to glycolic acid monomer molar ratio of about 75:25 (65:35 to 85:15). PLGA more preferably has a lactic acid to glycolic acid monomer molar ratio of about 85:15 (75:25 to 95:5). PLGA most preferably has a lactic acid to glycolic acid monomer molar ratio of about 99:1. Biodegradable thermoplastic polyesters can be prepared using methods known in the art, such as polycondensation and ring-opening polymerization (e.g., U.S. Patents 4,443,330, 5,242,910, and 5,310,865, all incorporated herein by reference). Biodegradable polymers can also be purified to remove residual monomers and oligomers using methods known in the art, such as dissolving and reprecipitation of the polymer (e.g., U.S. Patent No. 4,810,775 and No. 5,585,460, which are incorporated herein by reference). The terminal groups of poly(DL-lactide-co-glycolide) may be hydroxyl, carboxyl, or ester, depending on the polymerization and terminal group modification methods. Suitable polymers may contain monofunctional alcohol or polyol residues. Examples of monofunctional alcohols are methanol, ethanol, or 1-dodecanol.The polyol may be a diol, triol, tetraol, pentaol, or hexaol, including ethylene glycol, 1,6-hexanediol, polyethylene glycol, glycerol, sugars, glucose, sucrose, sorbitol and other reducing sugars. Many suitable PLGAs are commercially available, and PLGAs of specific compositions can be readily prepared according to the prior art.

[0049] The method for producing such a formulation according to this application requires weighing and mixing of materials, filtering of the final product, and degassing of the final product in order to accurately fill the formulation into a single, ready-to-use syringe. Weighing, mixing, filtering, and degassing can be carried out in an isolator for controlling the local environment, in which the relative humidity can be set to 60% or less at room temperature under nitrogen, argon, or dry air. In a preferred embodiment of this application, the weighing, mixing, filtering, and degassing of the formulation are carried out at 15-25°C under nitrogen at a humidity of 60% or less, preferably 40% or less.

[0050] The mixing vessel can be any conventional mixer with an impeller, or a planetary mixer or a double planetary mixer. Mixing of the biodegradable polymer and biocompatible solvent can be performed before the addition of the bioactive substance. The biocompatible solvent can be added to the mixing or compounding vessel before the biodegradable polymer to minimize mixing time and prevent polymer aggregation. If the polymer aggregates, it becomes difficult to dissolve and requires a long mixing time to form a homogeneous solution. In addition, a longer mixing time leads to more bubbles in the solution and a higher expansion level under vacuum, thus increasing the degassing time.

[0051] In a preferred embodiment of this application, about 90% biocompatible solvent is added to a mixing vessel, followed by the addition of a biodegradable polymer. The biodegradable polymer may be added all at once, sequentially, or in separate fractions to allow for better mixing and prevent polymer aggregation. The biodegradable polymer may be added in equal fractions, more preferably about 35% of the total amount of polymer in the first step and mixed until substantially wet, then a second fraction of about 30% of the total is added and substantially wet, then a third fraction of about 25% of the total is added and substantially wet, and then a final fraction of about 10% is added. In any case, the polymer may be substantially wet before adding the next fraction. The polymer may be divided into up to 30 parts, preferably less than 20 parts, more preferably less than 10 parts, and most preferably less than 5 parts. The size of the polymer fractions may be such that they prevent powder aggregation, which can form larger aggregates. These aggregates may increase the overall mixing and dissolution time. Polymer powder aggregates can be broken up by simple mixing or sieving before being added to the solvent. Polymer powders with high bulk density take longer to dissolve. These powders can be further ground or sieved to shorten the dissolution time.

[0052] After dissolving the biodegradable polymer in a biocompatible solvent, the bioactive substance is added to the solution. The bioactive substance can be added all at once, but more preferably, it can be added in two or three or more fractions, up to 20 fractions, to promote wetting or dissolution of the bioactive substance and prevent the formation of aggregates. Similar to the addition of the polymer, the bioactive substance may be added to the solution without agglomerating, which can increase the overall dissolution and mixing time. Aggregates and clumps in the powder can be broken up by simple mixing or sieving before adding to the solution. The bioactive substance may be completely wetted before adding the next fraction. After the bioactive substance has been added, the remaining fraction (about 10% to 30%) of biocompatible solvent is added to wash the powder remaining in the compounding container into the formulation. Alternatively, the bioactive substance can be dissolved in about 10% to 30% of the total biocompatible solvent to facilitate mixing with the polymer solution. Solubilizing the bioactive substance before adding to the polymer solution reduces the generation of bubbles due to solubilization and results in a less viscous solution. The final composition of the formulation is mixed until all powders are completely solubilized. The resulting formulation is a fluid, viscous liquid suspension or emulsion containing many air bubbles. This formulation needs to be degassed before being accurately filled into ready-to-use syringes.

[0053] The mixing of biodegradable polymers and bioactive substances with biocompatible solvents can be carried out in any type of mixing vessel that ensures complete dissolution of the biodegradable polymers and bioactive substances. In one embodiment of this application, the mixing of the biodegradable polymer and biocompatible solvent is carried out in a mixing vessel having an impeller at a mixing speed of about 20 rpm to about 200 rpm. The mixing is carried out at a speed that maintains the temperature inside the mixing vessel at or near ambient temperature. The total mixing time is sufficient to ensure complete dissolution of the polymer. The mixing time is determined by the mixing speed, the bulk density of the polymer, the wetting properties of the powder, and the solubility of the powder in the solvent. The wetting properties of the polymer powder can be optimized by adding the powder in multiple fractions to prevent powder aggregation. Next, the bioactive substance is added to the mixture and mixed at a speed of about 20 rpm to about 200 rpm until completely dissolved. In another embodiment of this application, the mixing is carried out in a double planetary mixer with a helical impeller and a scraper to ensure complete dissolution of the biodegradable polymer followed by the bioactive substance. In this embodiment, the helical impeller is maintained at a speed of approximately 20 rpm to 100 rpm to maintain the temperature of the mixing vessel. Alternatively, if a higher speed is used, a jacketed vessel can be used to maintain the vessel temperature at 15 to 25°C.

[0054] According to this application, filtration can be performed before or after degassing. In one preferred embodiment of the present invention, compounding is carried out under vacuum in a double planetary mixer or similar container. During the mixing of each fraction of the biodegradable polymer and the bioactive substance, the compounding container of the double planetary mixer is placed under a relative vacuum pressure of -300 to -1000 mbar to remove air trapped during the mixing and solubilization process. This reduces the overall required degassing time, provided that the formulation is thoroughly mixed before degassing.

[0055] A vacuum is a pressure lower than Earth's atmospheric pressure (approximately 14.7 psi, or 10¹³ mBar). By definition, a perfect vacuum is a space from which all matter has been removed. This is an idealized description. Creating a vacuum pressure close to a "nearly no matter" state is difficult and costly. Industrial and experimental applications require a vacuum lower than a perfect vacuum. Therefore, it is useful to understand the units used to measure vacuum and how to convert between them. Vacuum pressure can be expressed in absolute and relative units, as shown in the table below (Industrial Specialties Mfg. & IS MED Specialties). Relative units are used for vacuum pressure in this application.

[0056] [Table 1]

[0057] [Table 2]

[0058] The formulations of this application are viscous liquid suspensions or emulsions. In certain embodiments, a biodegradable polymer is dissolved in a highly soluble biocompatible solvent (polymer-rich phase), and a bioactive substance is dissolved in a highly soluble biocompatible solvent (bioactive substance-rich phase). It was unexpectedly found that the polymer-rich phase is immiscible with the bioactive substance-rich phase. When the polymer-rich phase is mixed with the bioactive substance-rich phase, the resulting formulation is not a homogeneous solution, but rather a suspension or emulsion in which bioactive substance-rich droplets are suspended in a continuous polymer solution phase. In another embodiment, a biodegradable polymer is first dissolved in a biocompatible solvent, and then a bioactive substance powder is added, mixed, and dissolved. In this case as well, since bioactive substance-rich droplets are suspended in a continuous polymer solution phase, the resulting formulation is characterized as a suspension or emulsion.

[0059] In a preferred embodiment of the present invention, leuprolide mesylate is mixed with a PLA polymer solution in NMP. The formulation produced according to this application is a milky white, opaque, viscous, fluid composition characterized as leuprolide-rich phase droplets suspended in a PLA-rich continuous phase having a viscosity greater than 10,000 centipoise (cPs). The viscosity may range from 10,000 to 100,000 cPs depending on the final composition.

[0060] In another preferred embodiment of the present invention, leuprolide mesylate is mixed with a PLGA polymer solution in NMP. The formulation produced by this application is a milky white, opaque, viscous, fluid composition characterized as leuprolide-rich phase droplets suspended in a PLGA-rich continuous phase.

[0061] In yet another preferred embodiment of the present invention, triptorelin mesylate is mixed with a PLA or PLGA polymer solution in NMP. The formulations produced according to this application are milky white, opaque, viscous, fluid compositions characterized as triptorelin-rich phase droplets suspended in a polymer-rich continuous phase having a viscosity greater than 10,000 centipoise (cPs). The viscosity may range from 10,000 to 100,000 cPs depending on the final composition.

[0062] The size of these droplets can vary depending on the mixing method. The uniformity of the formulation depends on the size and size distribution of these droplets. To produce formulations with a more uniform distribution of leuprolid-rich or triptorelin-rich droplets, stainless steel meshes or filters are used to remove particulate matter such as foreign matter or polymer agglutinations from the formulation, and to control or narrow the distribution of droplet sizes in the formulation. The pore size is in the range of about 5 μm to about 150 μm, preferably in the range of about 10 μm to about 100 μm, more preferably in the range of about 20 μm to about 80 μm, and most preferably in the range of about 40 μm to about 60 μm.

[0063] Due to the high viscosity of the formulation, upstream pressure is required to push the formulation through the filter. In a preferred embodiment of the present invention, in addition to the inlet pressure, a vacuum is drawn downstream to help the formulation move through the filter. Preferably, the inlet pressure is 1 bar to 10 bar, and the outlet vacuum (relative) is approximately -300 mbar to -1000 mbar. In another preferred embodiment of the present invention, the leuprolid formulation exits the compounding container under a pressure of 1 to 3 bar and is filtered through a 40 μm stainless steel mesh to remove particulate matter such as foreign matter or polymer aggregates from the formulation and narrow the leuprolid-rich particle size distribution. A downstream vacuum pressure (relative) of -300 mbar to -1000 mbar is also used to help draw the formulation through the filter. Furthermore, the vacuum also helps in degassing the formulation in the receiving container. The stronger the vacuum used, the more bubbles can be removed from the formulation in the receiving container before the degassing method. This can reduce the overall degassing time. In a preferred embodiment of the present invention, the receiving container vacuum (relative) is set to approximately -700, -750, -800, -850, -900, -950, or -980 mbar to degas the formulation as it is filtered, thereby shortening the overall required degassing time.

[0064] The method of this application also describes a procedure for degassing a formulation. In addition to the mixing method of this application, gas or bubbles are trapped in the formulation by solubilization of polymers and bioactive substances. Because a large amount of such trapped bubbles are present in this high-viscosity formulation, it is not possible to accurately fill the formulation into a syringe. Bubbles can be compressed under pressure and expand when the pressure is released. This can lead to variations in filling weight accuracy. Therefore, the formulation needs to be degassed before filling. According to this application, the formulation can be degassed before or after the filtration step. Due to the high viscosity of such formulations in this application, a vacuum is required to remove the gas in an appropriate amount of time. The degassing time depends on the final vacuum pressure that can be achieved. The higher the vacuum pressure, the shorter the degassing time. However, if the vacuum pressure is too high, the trapped gas may be released rapidly, causing the formulation to foam in the degassing vessel and overflow the vessel. Also, applying a high vacuum pressure may cause the solvent to evaporate depending on the vapor pressure of the solvent. This loss of solvent will alter the overall composition of the formulation.

[0065] When the vacuum pressure (relative pressure) is set to approximately -900 mbar, the formulation expands and swells within the degassing container. Maintaining this vacuum pressure causes air bubbles to rise within the formulation, coalescing and bursting at the surface. To shorten the overall degassing time, the vacuum pressure can be increased after a certain period of time at approximately -900 mbar. While the polymer solution can be easily degassed by increasing the vacuum pressure (relative) from -900 mbar to -950 mbar, it was unexpectedly found that changing the vacuum pressure from -900 mbar to -950 mbar caused the formulation to expand to a much higher level within the degassing container than in the case of a polymer solution without bioactive substances, due to its higher viscosity.

[0066] By gradually adjusting the vacuum pressure (relative) from approximately -900 mbar to approximately -950 mbar while degassing a container filled 1 / 3 with a formulation containing 13% leuprolide mesylate in a polymer solution of 57.5% PLA in NMP (polymer molecular weight approximately 16,000 daltons), the formulation could be degassed without overflowing the degassing container. However, when using a degassing container filled 1 / 3 with a formulation containing 8% leuprolide mesylate and a polymer solution of 57.7% PLGA in NMP (polymer molecular weight approximately 19,800 daltons), it was unexpectedly found that the formulation overflowed the vacuum container when the vacuum pressure was changed from -900 mbar to -950 mbar. The type and molecular weight of the polymer significantly influence the selection of degassing parameters for proper degassing.

[0067] In a preferred embodiment of the present invention, the filling level of the degassing vessel may be 10-50% to allow the formulation to expand as the pressure drops and air bubbles escape. More preferably, the filling level of the degassing vessel may be 15-35% to allow sufficient margin for the formulation to expand during degassing. Simply using a larger degassing vessel is not advantageous, as it not only takes up more space but also results in greater loss of formulation at the vessel walls, increasing manufacturing costs. The design of the degassing vessel is also important. Using a narrower vessel will result in the product filling the degassing vessel to a higher level, increasing the distance the air bubbles need to travel to degas the product. The larger the diameter of the degassing vessel, the lower the level of product inside the vessel, reducing the distance the air bubbles need to travel through the product bulk and shortening the overall degassing time. A suitable degassing vessel has a height-to-diameter ratio of 10:1-1:1, preferably 5:1-1:1.

[0068] In a preferred embodiment of the present invention for degassing a leuprolide formulation containing a PLGA polymer having a molecular weight of approximately 19,800 Daltons, the degassing container is filled to a level of approximately 33% of its total volume. After releasing the vacuum, it was unexpectedly found that when the same vacuum pressure was applied, the expansion level of the formulation was lower than at the start. Therefore, the degassing method is performed in stages to avoid overflow of the formulation from the container and to increase the vacuum pressure to shorten the overall degassing time. The initial vacuum pressure is set to approximately -900 mbar. After holding for 1 hour, the vacuum is released and a new vacuum pressure is set to approximately -920 mbar, and the formulation expands to approximately the same level as before. After holding this pressure for 1 hour, it is released. A new vacuum pressure is set to approximately -930 mbar. By repeating this method, the final vacuum pressure is reached without the product overflowing. When the vacuum is released, several large bubbles collapse and burst. Then, when the vacuum is drawn back up to the same pressure, the vacuum pressure is lower because there are fewer bubbles. The final pressure is kept considerably lower than the vapor pressure of the biocompatible solvent to prevent material loss and alteration of the final formulation's composition. In this way, increasing the vacuum pressure shortens the overall degassing time, and gradually increasing the vacuum pressure prevents overflow and loss. The degassed formulation can then be precisely filled into ready-to-use syringes.

[0069] Furthermore, it was unexpectedly found that degassing at longer intervals (vacuum intervals of 3 × 11 hours) resulted in heterogeneous bulk products. A gradient may be observed after long degassing times, with the concentration of bioactive substances being higher at the bottom of the degassing vessel and decreasing towards the top of the vessel, except for the area below the surface. Degassing causes the product to expand, reducing its overall viscosity. If the product remains at a low viscosity for an extended period, bioactive substance-rich droplets may migrate to the bottom of the filled container. Using shorter, more frequent degassing / aeration cycles can suppress the overall expansion of the formulation and reduce the time the formulation is expanded. This helps maintain a high viscosity of the product and prevents the occurrence of heterogeneity. Therefore, it is desirable to degas using multiple shorter vacuum / aeration cycles.

[0070] In certain embodiments, degassing is performed after all formulation mixing and filtration steps, if any. The degassing process is carried out by four or more vacuum / aeration cycles, applying a relative vacuum pressure between -300 mbar and -1000 mbar to a formulation or degassing vessel containing the prepared formulation, maintaining the vacuum for a time between 5 and 720 minutes, and then releasing the vacuum to allow aeration, wherein the vacuum level maintained in each vacuum / aeration cycle is at least the same as or stronger than the vacuum level maintained in the immediately preceding cycle. The vacuum target for the first vacuum / aeration cycle is set to -300, -400, -500, -600, -700, -800, or -900 mbar, depending on the viscosity of the formulation and the known potential expansion level under vacuum. The vacuum level maintained in each subsequent vacuum / aeration cycle is at least the same as or stronger than the vacuum level maintained in the immediately preceding cycle. The vacuum level maintained in the last or final vacuum / aeration cycle is preferably -950 mbar or higher.

[0071] In another embodiment, degassing is performed during the compounding process in each material introduction / mixing step. Approximately 90% of the total amount of biocompatible solvent is introduced into the compounding vessel. The biodegradable polymer is divided into two or more fractions. The first fraction of the biodegradable polymer is added to the compounding vessel containing the biocompatible solvent. A target vacuum between -300 and -1000 mbar, including -300, -400, -500, -600, -700, -800, or -900 mbar depending on the molecular weight of the biodegradable polymer, is applied to the compounding vessel before or during mixing. After mixing for 5 minutes to 2 hours, or until the biodegradable polymer is wet or substantially dissolved, the vacuum is released and the mixture is aerated. Subsequently, each subsequent fraction of the biodegradable polymer or LHRH agonist is introduced separately and sequentially into the compounding vessel after the previously added biodegradable polymer or LHRH agonist has become wet or substantially dissolved in the compounding vessel. A target vacuum between -300 and -1000 mbar, including -300, -400, -500, -600, -700, -800, or -900 mbar depending on the molecular weight of the biodegradable polymer, is applied to the compounding container before or during mixing. After mixing for 5 minutes to 2 hours, or until the biodegradable polymer is wet or substantially dissolved, the vacuum is released and the mixture is aerated. Subsequently, each subsequent fraction of the biodegradable polymer or LHRH agonist is introduced into the compounding container separately and sequentially, after the biodegradable polymer or LHRH agonist previously added to the compounding container has become wet or substantially dissolved. A target vacuum between -300 and -1000 mbar, including -300, -400, -500, -600, -700, -800, or -900 mbar depending on the molecular weight of the biodegradable polymer, is applied to the compounding container before or during mixing. After mixing for 5 minutes to 2 hours, or until the biodegradable polymer is wet or substantially dissolved, the vacuum is released and the mixture is aerated. The material introduction / vacuum / mixing / aeration process is repeated until all biodegradable polymers and LHRH agonists have been added and substantially dissolved, forming a substantially bubble-free, homogeneous formulation. The vacuum level maintained in each subsequent vacuum / aeration cycle is at least the same as or stronger than the vacuum level maintained in the immediately preceding cycle. The vacuum level maintained in the last or final vacuum / aeration cycle is preferably -950 mbar or higher.

[0072] To enable accurate filling into the syringe, the product does not need to be completely degassed. The bulk product needs to be substantially degassed to a degree sufficient to prevent the expansion of these bubbles after being extruded from the filling nozzle into the syringe. Due to the high viscosity of the product, a pressure of at least 1.0 bar is required in the filling tank to push the product into the pump and fill the syringe. The pressure drop from the filling nozzle to the syringe at ambient pressure can cause the product to expand if there are too many bubbles. Therefore, in a preferred embodiment of the present invention, the bulk product has few bubbles, and bubbles may still be visible on the surface of the product in the container.

[0073] In a preferred embodiment of the present invention, a method is provided for producing an injectable composition for controlled-release drug delivery by forming an economical, practical, and efficient controlled-release delivery system comprising a) a bioactive substance or a salt thereof, b) a biocompatible solvent, and c) a biodegradable polymer. The method comprises mixing the raw materials, and then filtering and degassing the product, which is carried out under a nitrogen atmosphere, at 15-25°C, and under controlled humidity of 60% or less, preferably 40% or less; filtration is carried out through a 40 μm stainless steel mesh with an inlet pressure of 1-2 bar and an outlet relative vacuum of -0.8 to -1.0 bar; and degassing is carried out under a relative vacuum of -300 mbar to -1000 mbar, with the initial vacuum pressure at the lower limit and gradually or stepwise increased to the final vacuum pressure to prevent overflow of the product and the formation of a concentration gradient, and to be completed in a reasonable time. The resulting formulation is a homogeneous liquid suspension or emulsion of bioactive substance-rich droplets suspended in a polymer-rich continuous phase, with minimal or no air bubble capture.

[0074] In another preferred embodiment of the present invention, a method is provided for producing an injectable composition for controlled-release drug delivery of leuprolide, the method comprising mixing raw materials, filtering the product, and degassing the product, these steps being carried out under a nitrogen, or argon, or dry air atmosphere, at 15–25°C and a controlled humidity of less than 40%, filtration being performed before or after the degassing step through a 40 μm stainless steel mesh with an inlet pressure of 1–10 bar and an outlet relative vacuum of -300–-1000 mbar, degassing being carried out stepwise under a relative vacuum of -300 mbar–-1000 mbar, and the degassing cycle time being no more than 5 consecutive hours before aeration and vacuum reset. The formulation can then optionally be mixed by slow rotation or mechanical mixing to ensure homogeneity.

[0075] In yet another preferred embodiment of the present invention, a method is provided for producing an injectable composition for controlled-release drug delivery of leuprolide, the method comprising adding raw materials in a double planetary mixer or similar mixer, and then degassing in the same vessel while mixing. Degassing is performed stepwise under a relative vacuum of -300 mbar to -980 mbar. Filtration is then performed through a 40 μm stainless steel mesh with an inlet pressure of 1 to 2 bar and an outlet relative vacuum of -0.8 to -1.0 bar. The resulting formulation is a homogeneous liquid suspension of leuprolide-rich droplets suspended in a polymer-rich continuous phase, with minimal or no air bubble capture. Preferably, the composition is readily injectable and can be packaged in a kit including the step of accurately filling syringes with the composition to make it ready for immediate use.

[0076] In a more preferred embodiment of the present invention, about 50% to 90% of a biocompatible solvent is added to a mixing vessel, followed by the addition of a biodegradable polymer. The biodegradable polymer can be added all at once, continuously, or in portions to allow for better mixing and prevent the polymer from agglomerating. After each addition of the polymer, the mixing vessel is closed and a vacuum is applied during mixing. This removes trapped air and prevents aeration during mixing. The biodegradable polymer can be added in equal or variable fractions. After the first fraction is added, the mixing vessel is closed, a vacuum is applied, mixing is carried out until the biodegradable polymer is substantially wet, mixing is stopped, the vacuum is released, and then the second fraction is added, the mixing vessel is closed, a vacuum is applied, mixing is carried out until the added fraction is substantially wet, mixing is stopped, the vacuum is released, and the process continues to the next step. This process is repeated until all fractions of the polymer have been added to the mixing vessel and dissolved. The polymer can be divided into up to 30 or more portions. The size of the polymer fractions may be determined to avoid the aggregation of powders that could form larger clumps. These clumps can increase the overall mixing and dissolution time. Polymer powder clumps can be broken up by simple mixing or sieving before being added to the solvent. Polymer powders with high bulk density take longer to dissolve. These powders can be further ground or sieved to shorten the dissolution time.

[0077] In a more preferred embodiment of the present invention, the biodegradable polymer can be continuously added through a material introduction port during mixing to enable better mixing and prevent polymer aggregation. Mixing and polymer introduction are performed under vacuum.

[0078] After dissolving the biodegradable polymer in a biocompatible solvent, the bioactive substance is added to the solution. The bioactive substance may be added all at once, or more preferably in two or three or more fractions, up to 20 fractions, to promote wetting or dissolution of the bioactive substance and prevent aggregation. Similar to the addition of the polymer, the bioactive substance may be added to the solution in such a way that no aggregates are present, which may result in longer overall dissolution and mixing times. After each fraction is added, the mixing vessel is closed, a vacuum is applied, and the mixture is continued until the fraction is substantially wet or dissolved, then mixing is stopped, the vacuum is released, and the process continues until all of the bioactive substance has been added. Aggregates or clumps in the powder can be broken up by simple mixing or sieving before being added to the solution. The bioactive substance may be substantially wetted before adding the next fraction. Once the bioactive substance has been added, the remaining fraction (approximately 10% to 30%) of the biocompatible solvent is added to wash the powder remaining in the mixing vessel into the formulation. Alternatively, the bioactive substance can be dissolved in approximately 10-30% of the total biocompatible solvent for easier mixing with the polymer solution. Solubilizing the bioactive substance before adding it to the polymer solution reduces the generation of bubbles due to solubilization in lower viscosity solutions. The final formulation is then mixed under vacuum until all powders are completely solubilized and most bubbles are removed. The resulting formulation is a fluid, viscous liquid suspension or emulsion with minimal bubbles.

[0079] Alternatively, in another, more preferred embodiment of the present invention, about 70% to 90% of a biocompatible solvent is added to a mixing vessel, followed by the addition of a biodegradable polymer. The biodegradable polymer may be added all at once, sequentially, or in separate fractions to allow for better mixing and prevent the polymer from agglomerating. The biodegradable polymer may be added in the same or variable fractions. After the first fraction is added, mixing is initiated until the polymer is substantially wet or dissolved, then the second fraction is added and mixed until substantially wet or dissolved, and the process continues to the next step. This process is repeated until all fractions of the polymer have been added and dissolved. The polymer can be divided into up to 30 fractions. The size of the polymer fractions may be made to avoid agglomeration of powder that may form larger clumps. These clumps may increase the overall mixing and dissolution time. Agglomerations of polymer powder may be broken up by simple mixing or sieving before being added to the solvent. Polymer powders with high bulk density take longer to dissolve. These powders can be further ground or sieved to shorten the dissolution time.

[0080] In a more preferred embodiment of this application, approximately 70% to 90% of a biocompatible solvent is added to a mixing vessel, followed by the addition of a biodegradable polymer. The biodegradable polymer may be added all at once, continuously, or in separate fractions to allow for better mixing and prevent polymer aggregation. The biodegradable polymer may be added in the same or variable fractions. After adding the first fraction, mixing is started at a low mixing rate (20 rpm) to limit the introduction of air into the mixture until the polymer is substantially wet or dissolved, then the vacuum is set to the lower limit of the range (-300 mbar) to prevent product overflow, and the mixing rate is increased (60-90 rpm). The vacuum level can then be gradually increased to the upper limit range (-1000 mbar) to degas the solution. This process is repeated until all fractions of the polymer and bioactive substance have been added and dissolved. Surprisingly, the final formulation was found to be substantially bubble-free and homogeneous. This process solves the problem of formulation gradient or heterogeneity.

[0081] After dissolving the biodegradable polymer in a biocompatible solvent, the bioactive substance is added to the solution. The bioactive substance may be added all at once, or more preferably in two or three or more fractions, up to 20 fractions, to promote wetting or dissolution of the bioactive substance and prevent aggregation. Similar to the addition of the polymer, the bioactive substance may be added to the solution in such a way that no aggregates are present. After each fraction is added, the mixture is stirred until the polymer is substantially wet or dissolved, and the process continues to the next step until all of the bioactive substance has been added and dissolved. Aggregates or clumps in the powder can be broken up by simple mixing or sieving before being added to the solution. The bioactive substance may be substantially wetted before adding the next fraction. Once the bioactive substance has been added, the remaining fraction (about 10% to 30%) of the biocompatible solvent is added to wash the powder remaining in the compounding container into the formulation. Alternatively, the bioactive substance may be dissolved in about 10% to 30% of the total biocompatible solvent to facilitate mixing with the polymer solution. Solubilizing the physiologically active substance before adding it to the polymer solution reduces the generation of bubbles due to solubilization in lower viscosity solutions. The final formulation is then mixed under vacuum until all powders are completely solubilized and most bubbles are removed. The resulting formulation is a fluid, viscous liquid suspension or emulsion with minimal bubbles.

[0082] The formulation obtained above can be further filtered. Filtration is performed through a 40 μm stainless steel mesh at an inlet pressure of 1 to 10 bar and an outlet relative vacuum of -300 to -1000 mbar. The resulting formulation is a homogeneous liquid suspension or emulsion of bioactive substance-rich droplets suspended in a polymer-rich continuous phase, with minimal or no air bubble capture. Preferably, the composition is readily injectable and can be packaged in a kit including the step of accurately filling a syringe with the composition to make it ready for immediate use.

[0083] The composition in the kit is stable for a suitable period, preferably at least two years, to have an appropriate shelf life under controlled storage conditions. The composition is preferably injected into a target to form an implant in situ, from which the bioactive substance is released in therapeutically effective amounts over a desired period of time. [Examples]

[0084] The following examples illustrate compositions of this application. The examples are not intended to limit the present invention, but are provided to teach methods for producing useful controlled-release drug delivery compositions.

[0085] (Example 1: Preparation of viscous polymer solution) Under nitrogen, at a temperature of 15-25°C and a relative humidity of 60% or less, 749 g of NMP was added to a mixing vessel, followed by the addition of PLA polymer (Resomer R 202 S, IV 0.22, Evonik lot #R120600501) at a speed of 100 rpm using a double marine-style impeller. To aid in wetting the polymer powder and prevent aggregation, the polymer was added in 16 fractions. The first 15 fractions were all approximately the same amount, about 100 g. The last fraction was less than 100 g, resulting in a total polymer addition of 1508.5 g, which was a 68% polymer solution in NMP. The addition time for each polymer fraction ranged from approximately 5 to 40 minutes to ensure that the powder was substantially wet before adding the next aliquot. Due to the capture of a large amount of air bubbles, the polymer solution appeared opaque, making it difficult to determine whether complete dissolution of the polymer in NMP had been achieved. To ensure complete dissolution of the polymer, the dissolution was continued overnight.

[0086] Next, the solution was passed through a 40 μm stainless steel mesh to filter out particulate matter or polymer aggregates. The solution was passed through the mesh at a pressure of approximately 8 bar, and a downstream relative vacuum of approximately -1000 mbar was applied to facilitate the removal of the solution through the filter. It took approximately 30 minutes to pass the material from the mixing vessel through the filter to the receiving vessel. After filtration, the filter was examined, and no polymer aggregates were observed, indicating that the polymer was completely dissolved.

[0087] The polymer solution was placed in a degassing container and an initial vacuum of approximately -1000 mbar was applied. Due to the large amount of trapped air and the high viscosity of the product, the polymer solution began to foam. Lowering the vacuum level to approximately -300 mbar suppressed the foaming and prevented the solution from overflowing. After approximately 2.5 hours, the vacuum level was gradually increased to approximately -1000 mbar, and the solution was left under vacuum for more than 5 days to completely degass it.

[0088] Next, to assist with pump priming, a pressure of approximately 6 bar was applied to the filling tank, and the solution was filled into a 1 mL long syringe using a rotary piston pump (SV 122V, Optima). A filling weight of 370 mg ± 20 mg was achieved with a pump rotation speed of 2%, a dose setting of 0.32 mL, and a back absorption of 1.00 mm.

[0089] (Example 2: Filtration of viscous formulation) A stainless steel filter with a pore size of approximately 25 μm was used to filter a formulation containing 13.5% leuprolide mesylate in 57.5% PLA (Evonik Resomer R 202 S, IV 0.22) in an NMP solution. An inlet pressure of 2 bar was used, and a relative outlet vacuum of -800 mbar was employed. After filtration, the formulation was recovered, and the droplet size of the leuprolide-rich phase was analyzed. Figure 1 shows a representative image of the droplets in the formulation obtained using an inverted confocal microscope. All droplets were approximately 25 μm or smaller. This method allowed for obtaining droplets with a fairly uniform distribution.

[0090] (Example 3: Manufacture of a formulation containing leuprolide and PLA) A PLA polymer formulation containing leuprolide was prepared by the following method. The final formulation was approximately 13.5% leuprolide mesylate in approximately 57.5% PLA (Evonik Resomer R 202 S, IV 0.22) in an NMP solution. Mixing, filtration, and degassing were all performed under nitrogen, at a temperature of 15-25°C and a relative humidity of less than 40%. The molecular weight of the PLA was approximately 16,500 daltons. The polymer solution was prepared in the same manner as described in Example 1, with a slight modification of dividing the polymer into 4 fractions instead of 16. Approximately 330 g of NMP was added to a mixing vessel, followed by approximately 190.0 g of PLA polymer. The solution was mixed until all the polymer was substantially wet or dissolved. Next, approximately 124.3 g of PLA was added, and the solution was mixed again until all the polymer was substantially wet or dissolved. Next, approximately 124.0 g of PLA was added, and the solution was mixed again until all the polymer was substantially wet or dissolved. Finally, approximately 50 g of the remaining PLA was added, and the solution was mixed until a homogeneous solution was obtained. Next, 68.0 g of leuprolide mesylate was added to the solution, and the mixture was mixed until all of the leuprolide mesylate was substantially wet or dissolved. Then, 67.5 g of leuprolide mesylate was added, and the mixture was mixed until all of the leuprolide mesylate was substantially wet or dissolved. Finally, 37.4 g of NMP was used to wash away any material adhering to the side walls of the mixing vessel, and the formulation was mixed until a homogeneous suspension or emulsion was obtained.

[0091] Next, the obtained formulation was subjected to a 40 μm stainless steel filter using an upstream pressure of 2 bar and a downstream vacuum pressure of -0.8 bar. The formulation was filtered into a degassing (receiving) container. The filtrate volume was approximately 1 / 3 of the total volume of the container. Subsequently, the formulation was degassed at an initial vacuum pressure of -900 mbar. After about 12 hours, the vacuum pressure was set to -950 mbar. Contrary to expectations, the formulation overflowed from the degassing container and flowed into the vacuum line. This indicates that the volume of the formulation more than tripled under a vacuum of -950 mbar. The vacuum was released and the mixture was ventilated to the atmosphere. Then, vacuum was applied again and gradually increased, raising the vacuum pressure to -910 mbar for 2 hours and returning the vacuum to the atmosphere. Next, the vacuum pressure was increased to -930 mbar for 2 hours and again returning the vacuum to the atmosphere. Next, the vacuum pressure was increased to -940 mbar for 2 hours and again returning the vacuum to the atmosphere. Subsequently, the vacuum pressure was increased and set to -950 mbar for 12 hours, after which the vacuum was returned to the atmosphere. The resulting formulation was virtually bubble-free.

[0092] (Example 4: Manufacture of a leuprolide-containing preparation) Polymer formulations containing leuprolide were prepared by the following method. The final formulation was 8% leuprolide mesylate in 58% PLGA (8515 PLGA, Durect lot #A16-088, IV-0.24) in an NMP solution. Mixing, filtration, and degassing were all performed in an isolator under nitrogen, at a temperature of 15-25°C and a relative humidity of less than 40%. The molecular weight of PLGA was approximately 19,800 daltons, and the ratio of monomer lactic acid to glycolic acid was approximately 85:15 or between 80:20 and 90:10. The polymer solution was prepared in the same manner as described in Example 3, with a slight modification of dividing the polymer into four fractions. Approximately 90% NMP was added to a mixing vessel, followed by approximately 40% PLGA polymer. The solution was mixed until all the polymer was substantially wet or dissolved. Next, approximately 25% PLGA was added, and the solution was mixed again until all the polymer was substantially wet or dissolved. Next, approximately 25% of PLGA was added, and the solution was mixed again until all polymers were substantially wet or dissolved. Finally, all remaining PLGA, approximately 10%, was added, and the solution was mixed until a homogeneous solution was obtained. Then, approximately 50% of leuprolide mesylate was added to the solution, and the solution was mixed until all leuprolide mesylate was substantially wet or dissolved. Next, the remaining leuprolide mesylate fraction was added, and the contents were mixed until all leuprolide mesylate was substantially wet or dissolved. Then, the remaining approximately 10% of NMP was used to wash away any material adhering to the sides of the mixing vessel. Finally, the formulation was mixed further for at least 15 minutes until a homogeneous suspension or emulsion was obtained.

[0093] Next, the obtained formulation was passed through a 40 μm stainless steel filter using an upstream pressure of 2 bar and a downstream vacuum pressure of -0.8 bar, and supplied to a degassing (receiving) container. The formulation occupied approximately 1 / 3 of the total volume of the receiving degassing container. Subsequently, the formulation was degassed at an initial pressure of -900 mbar. After a certain period, the vacuum pressure was set to -950 mbar. Contrary to expectations, the formulation overflowed the degassing container and flowed into the vacuum line.

[0094] As shown in Figure 2, a change in the degassing method is necessary to degas the formulation without overflow. In this experiment, the vacuum pressure was set to -900 mbar and held for 1 hour. Then, the vacuum was released and air was allowed to vent, causing some bubbles to burst. The vacuum pressure was reset to -920 mbar and held again for 1 hour. Then, the vacuum was released and air was allowed to vent, causing some bubbles to burst. The vacuum was reset to -930 mbar and held for 1 hour. Then, the pressure was released and air was allowed to vent, causing some bubbles to burst. The vacuum was reset to -940 mbar and held for 1 hour. Then, the vacuum was released and air was allowed to vent, causing some bubbles to burst. The vacuum was reset to -950 mbar. The bubble level rose again, but there was no overflow. In this way, the formulation can be degassed at a pressure of -950 mbar without overflow, similar to Example 3. This procedure can be repeated, and the vacuum pressure between each cycle can be gradually increased as needed.

[0095] (Example 5: Degassing of a formulation containing leuprolide and PLGA) A formulation containing 8% leuprolide mesylate was prepared in 58% PLGA in NMP solution. The molecular weight of PLGA was approximately 19,800 daltons (intrinsic viscosity 0.24), and the ratio of monomer lactic acid to glycolic acid was approximately 85:15 (80:20~90:10). The formulation was degassed. The formulation was added to different 4 mL vials and filled to 10%, 25%, 33%, 50%, and 67% of the vial's volume. The vacuum pressure was then set to -900 mbar. The volume of the formulation increased slightly as bubbles in the formulation expanded under vacuum. The vacuum pressure was then set to -950 mbar. Figure 3 shows the formulation in the vials at -950 mbar. The 67% filled vial overflowed. The 50% filled vial swelled above the vial level. The 10%, 25%, and 33% filled vials all approximately doubled in volume due to bubble expansion, but remained within the vials. Thus, based on the specific characteristics of the formulation, there is a specific range of filling levels that can be used at a specific vacuum pressure. Since the size of the degassing vessel is limited, the degassing pressure must be adjusted so that the formulation is degassed in a reasonable amount of time without overflowing. The appropriate vacuum for degassing is in the range of -300 to -1000 mbar, depending on the viscosity of the formulation and the size of the degassing vessel.

[0096] (Example 6: Degassing of viscous formulation) During mixing to solubilize polymers and bioactive substances, air bubbles are trapped in the formulation. To accurately fill syringes with the formulation, the bulk formulation needs to be largely degassed. In one experiment, a formulation of 8% leuprolide mesylate in 58% PLGA (IV=0.24) in NMP solution was filled to half the level of a container. The container was then subjected to a vacuum of -900 mbar. The size of the air bubbles in the formulation increased, and the formulation level rose to near the top of the container. After 1 hour at -900 mbar, the vacuum was increased to -950 mbar. The formulation then foamed and spilled over the sides of the container.

[0097] In another experiment, the vacuum pressure was set to -900 mbar. The size of the bubbles in the formulation increased, and the formulation level rose to near the top of the container. After 1 hour, the vacuum was released, and the bubble level decreased. The vacuum was reset to -920 mbar and held for another hour. Then the pressure was released, and the bubble level decreased. The vacuum was then reset to -930 mbar and held for another hour. Then the pressure was released, and the bubble level decreased. The vacuum was then reset to -940 mbar and held for another hour. Then the vacuum was released, and the bubble level decreased. The vacuum was then reset to -950 mbar. The bubble level rose again, but there was no overflow. In this way, the formulation can be degassed at a pressure of -950 mbar without overflowing. This procedure can be repeated, and the vacuum pressure between each cycle can be gradually increased as needed.

[0098] (Example 7: Vacuum pressure range) To determine the optimal vacuum range, vacuum pressure levels were tested. Higher vacuum pressures resulted in faster degassing, but excessively high vacuum pressures could remove the solvent. A 50% PLGA / NMP solution was placed in a 20 mL glass vial under continuous vacuum. It was subjected to a vacuum pressure of -10¹³.0 mbar, and the weight of the polymer solution was measured after a specified time. Table 3 shows the weight change over time, reflecting the loss of NMP due to vacuum pressures lower than the vapor pressure of NMP (approximately 0.3 mmHg (or relative vacuum of -10¹².9 mbar)).

[0099] [Table 3]

[0100] A weak vacuum can be used to reduce solvent loss from the formulation, but it must still be high enough to remove trapped bubbles.

[0101] The formulation degassed in Example 6 was weighed before and after degassing. The weight change was only 0.3%. This is because the vacuum level used was considerably lower than the vapor pressure of NMP. Therefore, a vacuum range was obtained in which the formulation could be degassed without overflowing the container or removing the solvent from the composition.

[0102] (Example 8: Gradient Formation) A formulation of leuprolide mesylate in PLA (Evonik Resomer Select 100 DL 2E-P (purified Resomer R 202S), IV 0.22) / NMP solution was prepared and then divided into 10 mL syringes, which were back-connected to empty 10 mL syringes to allow product expansion. The syringes were placed under a vacuum of -950 mbar for 3 days to completely degass. One control syringe was placed under atmospheric pressure without degassing. The leuprolide content of the samples was measured in the upper and lower fractions. The results showed that the mean concentration of leuprolide in the upper fraction was 10.7%, while the mean concentration in the lower fraction was 11.6%. The leuprolide concentration in the control was 11.4% in the upper fraction and 11.5% in the lower fraction. Thus, contrary to expectations, the degassing method using a continuous vacuum of -950 mbar created a concentration gradient in the lower part of the container, with a much higher concentration of leuprolide than in the upper part.

[0103] (Example 9: Degassing by cycle) A formulation containing approximately 10% leuprolide mesylate in approximately 58% PLA (Evonik Resomer Select 100 DL 2E-P, IV 0.22) in an NMP solution was added to a 50 mL test tube up to the label level of 15 mL. The tube was placed under a vacuum of -950 mbar and the level was increased to more than double (32 mL). One container was kept at -950 mbar, and the other container was vented to atmospheric pressure after 1 hour. It was then returned to a vacuum of -950 mbar. This vacuum / vent cycle was repeated a total of 6 times. After 3 cycles (3 hours), the expansion level had decreased to approximately 17 mL, while the container without cycles still exceeded 20 mL even after 15 hours. The formulation that was continuously degassed took more than 22 hours to degas, while the formulation that underwent 6 vacuum / vent cycles took 10 hours to degas. The leuprolide content at the top and bottom of this container was analyzed. Contrary to expectations, the measurements at the top, middle, and bottom were very similar, and no gradient formation due to the vacuum / aeration degassing cycle was observed. On the other hand, the formulation subjected to continuous degassing showed a gradient similar to that of Example 8 described above.

[0104] By using a vacuum / aeration cycle, not only was the degassing time reduced, but the time spent on high levels of expansion (decrease in formulation viscosity) was also unexpectedly reduced, resulting in the prevention of leuprolide redistribution. This is important for maintaining the uniformity of the formulation during the degassing process.

[0105] (Example 10: Filtration) After compounding the leuprolide mesylate formulation in a PLA / NMP solution, half of the formulation was passed through a filter with an average pore size of 100 μm at -950 mbar, and the remaining half was completely degassed by placing it directly under a vacuum of -950 mbar. After filtration, the formulation was returned to atmospheric pressure and completely degassed under a vacuum of -950 mbar. It was found that the formulation before filtration was degassed in half the time compared to the unfiltered sample. The leuprolide content of the samples was also measured. The filtered sample showed a leuprolide concentration of 11.1% in the upper fraction and 11.2% in the lower fraction, while the unfiltered sample showed a leuprolide concentration of 10.5% in the upper fraction and 11.2% in the lower fraction. Thus, the filtration step adds another degassing cycle that helps shorten the degassing time and reduce the formation of a leuprolide gradient.

[0106] (Example 11: Filling after filtration under high vacuum pressure) The formulations prepared after mixing in previous examples contain trapped air or bubbles. These bubbles can be compressed under pressure and expanded under vacuum. Large bubbles can be compressed during filling before entering the pump and expand after passing through the pump due to the release of pressure. Excessive expansion of the product can cause dripping at the tip of the filling needle, leading to contamination of the outside of the syringe and variations in filling weight. Therefore, an appropriate degree of degassing is necessary. To determine the acceptable degree of degassing for accurate filling, the following experiment was conducted.

[0107] 7.5 mL of the leuprolide formulation described in Example 8 was packed into one 50 mL centrifuge tube. The tube was placed in a vacuum chamber and vacuumed to -950 mbar. The product expanded to approximately 18 mL of the labeled volume. When the vacuum was further reduced to -980 mbar, the product expanded beyond the 50 mL labeled volume. Therefore, from the initial level to -950 mbar, the product expanded to approximately 2.5 times its original size. From the initial level to -980 mbar, it expanded to more than 7 times its original size.

[0108] To remove some large air bubbles during filtration, the upstream pressure was kept at atmospheric pressure and the downstream vacuum pressure was set to -980 mbar. Approximately 450 g of the formulation was filtered for about 110 minutes. After stopping the vacuum, the volume had decreased by approximately four times, indicating that many air bubbles were still trapped in the formulation (Figure 4). However, the large air bubbles appeared to have been removed. After stopping the vacuum, almost no visible air bubbles were observed in the bulk product, except for a small number of tiny bubbles on the surface. This level of degassing may be sufficient for use without further degassing before filling syringes.

[0109] Over 650 syringes were filled using a semi-automatic filling machine equipped with a rotary piston pump at an inlet pressure of 1.5 bar and a speed of 10 cycles / min. The weight of 148 syringes filled within this range was measured. Table 4 shows the average filled weight by standard deviation and relative standard deviation. The filling was as accurate as when the formulation was completely degassed, with a relative standard deviation (RSD) of less than 1%. Thus, slow filtration under a stronger vacuum downstream can save considerable time in the manufacturing process and enable accurate filling without completely degassing the formulation. The bulk can be largely degassed to the extent that some remaining bubbles are visible on the surface. These results demonstrate that under a vacuum pressure of -980 mbar, the product expands to less than four times its original size, and no further degassing is necessary to achieve accurate filling unless there are large, visible bubbles.

[0110] [Table 4]

[0111] (Example 12: Degassing during mixing) A polymer solution in NMP was prepared using a Ross Mixers double planetary mixer (DPM-Qt). First, 80% NMP was added to the mixing vessel. Then, 25% PLA was added through the side port while using the HV impeller at 10 RPM. After the addition, the rotation speed was increased to 30 RPM. Mixing was stopped, another 25% of the polymer was added, and mixing was resumed at 30 RPM. After 3 minutes, the powder was completely wetted, so mixing was stopped and the next polymer was added. Mixing was resumed for a further 2 minutes to wet the powder. Then, mixing was stopped and another portion of the polymer was added to the mixer. This addition was incorporated in about 1 minute. Mixing was stopped again for the final addition of polymer. After mixing for a further 1 minute at 30 RPM, the vacuum was reduced to approximately -1000 mbar. After 3 minutes, the product was inspected and most of the material had dissolved. Mixing was resumed under vacuum, but the compounding container was sealed after the vacuum reached the target of -1000 mbar to prevent loss of NMP. After another 8.5 minutes, the remaining 50 g of NMP was added. Mixing and vacuum were then resumed. After a total of 1 hour, the container was opened, yielding approximately 550 g of a clear, homogeneous solution. The final polymer solution was essentially bubble-free.

[0112] (Example 13: Degassing during mixing) A polymer solution in NMP was prepared using a Ross Mixers double planetary mixer (DPM-2). First, 405 g of NMP (90% of the total) was added to the mixing vessel. 180 g of polyvinylpyrrolidone (PVP K30, average molecular weight 50 k) (40% of the total) was added, and mixing was initiated using an HV impeller equipped with a bottom crossbar and scraper. The mixer was operated at 20 RPM. After 5 minutes, 112.5 g of PVP (25% of the total) was added to the mixing vessel. After another 5 minutes, another 112.5 g of PVP was added to the mixing vessel. After another 5 minutes, the remaining 45 g of PVP was added to the mixing vessel. After another 5 minutes, the remaining NMP (45 g) was added. After a total of 40 minutes of mixing, a vacuum was applied to approximately -800 mbar. The volume of the material increased. After a few minutes, the vacuum level was increased to approximately -950 mbar. After another 40 minutes, when the container was opened, the product appeared semi-transparent, with only a few bubbles remaining, and there were no undispersed aggregates. The product looked very uniform and smooth.

[0113] (Example 14: Degassing during mixing of leuprolide formulations) In a 6L compounding container, 90% NMP (1017.9g) was initially added, followed by the first fraction of PLA (Evonik Resomer R 202 S, IV 0.22). The PLA was divided into four fractions of 40%, 25%, 25%, and 10% of the total PLA amount (1529.2g). Mixing was initiated, and a vacuum was drawn to approximately -300mbar, maintaining this level during mixing. Mixing continued for approximately 30 minutes. After that, the vacuum was released to stop mixing, and the next fraction of PLA was added. The same process was repeated four times until all fractions of PLA had been added and mixed. Leuprolide mesylate was divided into three fractions of approximately 33% each. The first fraction of leuprolide mesylate was then added to the container, and mixing was initiated. Once the desired mixing rate was reached, a vacuum was drawn to approximately -300mbar, maintaining this level during mixing. Mixing was continued for approximately 15 minutes. Then, the vacuum was released, mixing stopped, and the next fraction of leuprolide mesylate was added. The same process was repeated three times until all fractions of leuprolide mesylate had been added and mixed. The vacuum was then gradually increased to -950 mbar through at least four vacuum and aeration cycles, while continuing to mix, until a final vacuum pressure of at least -950 mbar was reached. The final formulation was a viscous emulsion with very few bubbles remaining.

[0114] Next, the obtained formulation was filtered using a stainless steel mesh with an average pore size of 40 μm to narrow the distribution of leuprolide / NMP droplet sizes and remove potential particulate matter or polymer aggregates from the formulation. Filtration was performed under an inlet pressure of 2 bar and an outlet vacuum pressure of -800 mbar. The obtained formulation was a viscous liquid suspension of leuprolide-rich droplets suspended in a PLA-rich continuous phase with a viscosity exceeding 10,000 centipoise (cPs). The suspension showed virtually no visible bubbles smaller than 5 mm in diameter on the surface of the formulation at atmospheric pressure.

[0115] (Example 15: Effect of mixing time on the uniformity of drug products) In a compounding container, NMP was introduced first, followed by the introduction of PLA in several fractions until PLA was obtained in an NMP solution. Next, leuprolide mesylate was added to the PLA in the NMP solution. The solution was mixed for different times, and the leuprolide / NMP droplet size was analyzed. To determine the droplet size, the formulation was injected into an Ibidi 2-well microinsert on a glass slide, and analyzed using an inverted multiphoton confocal scanning microscope set to a laser of 745 nm and a detector of 436-684 nm. Droplet images were taken at a depth of 10 μm from the slide surface to avoid the effect of surface tension on the droplets. The images were collected and processed using ImageJ software, and the droplet area was calculated. Table 5 below shows the droplet sizes of these formulations. Droplet size and variability (RSD) decreased with increasing mixing time.

[0116] [Table 5]

[0117] If the mixing time is not sufficiently long, larger and more unstable droplet sizes may be present, potentially leading to phase separation of the formulation. These larger droplet sizes can be observed using an inverted confocal microscope, which can measure droplet size and distribution. Figure 5 shows a confocal image of a formulation that was not completely mixed, where the droplet size was larger and the suspension was heterogeneous. Therefore, sufficient mixing time is necessary to obtain a uniform and homogeneous formulation.

[0118] (Example 16: Degassing during mixing of triptorelin preparations) A predetermined amount of N-methylpyrrolidone and PLA or PLGA were introduced into a compounding vessel and mixed under vacuum to avoid the formation of bubbles. After the polymer was completely dissolved, a predetermined amount of triptoreline mesylate was added and thoroughly mixed under vacuum until completely dissolved, forming a viscous suspension with no trapped bubbles or a few small, visible trapped bubbles less than 5 mm in diameter under atmospheric pressure. Next, the suspension was filtered using a stainless steel mesh of 20–100 μm size to narrow the droplet size distribution and remove potential particulate matter or polymer aggregates in the formulation. Filtration was performed at an inlet pressure of 2 bar and an outlet vacuum pressure of -920 mbar. The resulting formulation was a viscous liquid suspension of triptoreline-rich droplets suspended in a PLA-rich or PLGA-rich continuous phase with a viscosity of over 10,000 centipoise (cPs), as shown in Figure 6. The suspension showed only a few trapped bubbles less than 5 mm in diameter on the surface of the product under atmospheric pressure. A single, ready-to-use syringe is manufactured by filling the syringe tip with the formulation to a desired volume. Alternatively, a single, ready-to-use syringe is manufactured by filling the syringe barrel to a desired volume according to the process described in claim 1.

[0119] (Example 17: Degassing during mixing of goserelin preparations) A predetermined amount of N-methylpyrrolidone and PLA or PLGA were introduced into a compounding container and mixed under vacuum to avoid the formation of bubbles. After the polymer was completely dissolved, a predetermined amount of goserelin sulfate was added and mixed thoroughly under vacuum until completely wet, forming a viscous suspension with no trapped bubbles or a few small, visible trapped bubbles less than 5 mm in diameter under atmospheric pressure. The resulting formulation was a viscous suspension of goserelin sulfate solid particles suspended in a PLA or PLGA solution in NMP with a viscosity of over 10,000 centipoise (cPs), as shown in Figure 7. The suspension showed only a few trapped bubbles less than 5 mm in diameter on the surface of the product under atmospheric pressure. The formulation was filled into a syringe to the desired volume from the tip or barrel side to produce a single ready-to-use syringe.

[0120] Those skilled in the art will understand that modifications can be made to the embodiments described above without departing from the broader concept of the invention. Therefore, it will be understood that the present invention is not limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as defined by the specific description.

Claims

1. A method for producing an injectable sustained-release formulation, wherein the injectable sustained-release formulation comprises leuprolide mesylate or triptorelin mesylate, N-methylpyrrolidone (NMP), and a biodegradable polymer, and the method is as follows: (i) A compounding process carried out at 15 to 25°C and under controlled humidity of less than 60%, the compounding process comprising: a) introducing 70% or more of the total amount of NMP into a compounding container; b) dividing the biodegradable polymer into a plurality of fractions, adding a first fraction of the biodegradable polymer to the compounding container, mixing the first fraction of the biodegradable polymer with the NMP in the compounding container until the first fraction of the biodegradable polymer is wet or dissolved, then introducing each of the remaining fractions of the biodegradable polymer separately and sequentially into the compounding container, mixing until the newly added fraction of the biodegradable polymer is wet or dissolved before introducing the next fraction of the biodegradable polymer; and c) until all of the fractions of the biodegradable polymer are dissolved or substantially dissolved. The process includes: dissolving in , then separately adding 1 to 20 fractions of leuprolide mesylate or triptorelin mesylate to the compounding container; mixing the fractions of leuprolide mesylate or triptorelin mesylate with NMP and a biodegradable polymer in the compounding container until the leuprolide mesylate or triptorelin mesylate is wet or dissolved (where, after the leuprolide mesylate or triptorelin mesylate previously added to the compounding container is wet or dissolved, subsequent fractions of leuprolide mesylate or triptorelin mesylate may be added as desired); and mixing the leuprolide mesylate or triptorelin mesylate with NMP and a biodegradable polymer in the compounding container to form the formulation; (ii) A degassing step performed by four or more vacuum / venting cycles, in which a relative vacuum pressure between -300 mbar and -1000 mbar is applied to the mixing container or degassing container containing the formulation prepared in (i) above, the vacuum is maintained for a time between 5 minutes and 720 minutes, and the vacuum is released to allow ventilation (wherein the vacuum level maintained in each vacuum / venting cycle is the same as or stronger than the vacuum level maintained in at least the immediately preceding cycle), Includes, The formulation is a viscous suspension or emulsion of leuprolide mesylate or triptoreline mesylate-rich phase (LHRH / NMP droplets) having a droplet diameter of less than 50 μm and a Dv50, suspended in a biodegradable polymer-rich continuous phase, and having a viscosity greater than 10,000 centipoise (cPs), and the method.

2. After introducing the last fraction of leuprolide mesylate or triptorelin mesylate, the formulation is further mixed for at least 15 minutes to obtain LHRH / NMP droplets in the formulation having a droplet size of Dv50 ≤ 25 μm with RSD ≤ 100%. The method according to feature 1.

3. The biodegradable polymer is selected from the group consisting of homopolymer polylactic acid (PLA), copolymer poly(lactic acid-coglycolic acid) (PLGA), and combinations thereof, wherein the lactide:glycolide (or lactic acid:glycolic acid) ratio of the copolymer is 50:50 to 99:1, and the PLGA or PLA polymer has a molecular weight of 5,000 to 50,000 daltons. The method according to claim 1, characterized by the features described above.

4. The aforementioned blending process is carried out at a temperature of 15 to 25°C and under controlled humidity of 40% or less. The method according to feature 1.

5. 70-90% of the total NMP is initially introduced into the compounding container, and the remaining 10-30% is introduced after the addition of all the biodegradable polymers and leuprolide mesylate or triptorelin mesylate. The method according to feature 1.

6. Leuprolide mesylate or triptorelin mesylate is added to the compounding container all at once and dissolved. The method according to claim 1, characterized by the features described above.

7. Leuprolide mesylate or triptorelin mesylate is added to the compounding container in two or more separate fractions and dissolved sequentially, and the subsequent fraction of leuprolide mesylate or triptorelin mesylate is added after the leuprolide mesylate or triptorelin mesylate previously added to the compounding container has dissolved. The method according to claim 1, characterized by the features described above.

8. The process further includes performing a filtration step using a filter having an average pore size in the range of 20 μm to 100 μm under an inlet pressure of 1 bar to 10 bar and an outlet relative vacuum pressure of -300 mbar to -1000 mbar, wherein the filtration is performed before the degassing step. The method according to claim 1, characterized by the features described above.

9. The filter has an average pore size of 40 μm, and the filtration is performed under an inlet pressure of 1.8 to 2.0 bar and an outlet relative vacuum pressure of -700 mbar to -950 mbar. The method according to feature 8.

10. The suspension or emulsion is substantially free of air bubbles and homogeneous. The method according to feature 1.

11. Leuprolide mesylate or triptorelin mesylate is triptorelin mesylate, and the biodegradable polymer is PLA or PLGA. The method according to claim 1, characterized by the features described above.

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