Granisetron sustained-release microsphere and preparation method therefor

Abstract

The present application discloses a granisetron sustained-release microsphere and a preparation method therefor. On the basis of the mass of the granisetron sustained-release microspheres being 100%, the content of granisetron or a pharmaceutically acceptable salt thereof is 3-12%, the content of a stabilizer is 1-25%, and the content of a biodegradable polymer is 65-96%. The biodegradable polymer is a poly(lactic-co-glycolic acid), and the stabilizer is a fatty acid. The granisetron sustained-release microsphere obtained by the present invention has a high drug loading capacity, a uniform particle size, a complete morphology and no adhesion, a smooth surface without obvious pores, and no risk of burst release or drug leakage, and can achieve sustained release in vitro for up to 5-7 days.

Description

A granisetron sustained-release microsphere and its preparation method Technical Field

[0001] This application belongs to the field of pharmaceutical formulation technology, and in particular relates to a granisetron sustained-release microsphere and its preparation method. Background Technology

[0002] Chemotherapy-induced nausea and vomiting (CINV) is nausea and vomiting caused by adverse reactions to chemotherapy drugs, resulting in subjective discomfort for patients. CINV involves the activation of various neurotransmitters, including serotonin (5-HT), dopamine, and neurokinin-1 (NK1), in the vagus nerve afferent pathway of the intestine and the vomiting center of the brain. CINV is one of the most common toxic side effects during chemotherapy. It not only affects patients' quality of life but can also lead to decreased treatment adherence, further impacting the effectiveness of chemotherapy; therefore, its importance cannot be ignored. Currently used antiemetic drugs include dopamine receptor antagonists, 5-HT3 receptor antagonists, and NK-1 receptor antagonists. For the prevention of nausea and vomiting induced by highly emetogenic chemotherapy (HEC), a three-drug combination regimen is used before chemotherapy, with the combination of a 5-HT3 receptor antagonist, dexamethasone, and an NK-1 receptor antagonist being the preferred choice. For the prevention of nausea and vomiting induced by moderately emetogenic chemotherapy (MEC), the standard dual-drug regimen of a 5-HT3 receptor antagonist combined with dexamethasone is used. For the prevention of nausea and vomiting caused by low-emetic regimens, a single antiemetic drug is recommended. 5-HT3 receptor antagonists, dexamethasone, dopamine receptor antagonists (such as metoclopramide), or chlorpromazine are recommended for the prevention of vomiting.

[0003] Granisetron's chemical name is 1-methyl-N-(9-methyl-9-azabicyclo[3,3,1]nonane-3-yl)-1H-indole-3-carboxamide, and its molecular formula is C2. 18 H 24 N4O, with a molecular weight of 312.41, is a first-generation 5-HT3 receptor antagonist with good preventive and therapeutic effects on nausea and vomiting induced by radiotherapy, chemotherapy, and surgery. Its pharmacological studies show that, compared with other 5-HT3 receptor antagonists, it has improved side effects and tolerability, a lower risk of drug interactions, and a longer duration of action. Its structural formula is as follows:

[0004] Granisetron hydrochloride was initially developed by Beecham in the mid-1980s. In 1991, a 3mg injection was available. It is available in South Africa. To date, granisetron hydrochloride injections and oral tablets are available in more than 40 countries and regions worldwide, including the US, UK, France, Japan, Germany, and Italy. However, traditional preventative measures for chemotherapy-induced nausea and vomiting mainly rely on short-acting intravenous formulations, which result in significant fluctuations in blood drug concentrations and require repeated administration, leading to poor patient compliance. In 2008, granisetron transdermal patches developed by Kyowa Hakko Kirin of Japan were approved by the FDA and subsequently by the EMA in 2012, under the brand name [Brand Name Missing]. A 3.1 mg release of granisetron every 24 hours over 7 days can be used to prevent nausea and vomiting in patients receiving moderately and / or highly emetogenic chemotherapy regimens lasting up to 5 days, but It is not suitable for acute CINV and has drawbacks such as easy dislodgement. In 2016, granisetron extended-release injection, developed by Heron Therapeutics, was approved by the FDA under the brand name [Brand Name Missing]. The Biochronomer polymer delivery system enables sustained release in vivo for up to 7 days, preventing acute and delayed nausea and vomiting associated with initial and repeated courses of moderately emetogenic chemotherapy (MEC) or combination chemotherapy regimens of anthracyclines and cyclophosphamide (AC). As an organic solvent system, it is highly irritating locally and prone to adverse reactions such as inflammation. Furthermore, after injection, it comes into contact with body fluids, and the drug may be released suddenly due to the influence of the solvent diffusion rate.

[0005] To improve the clinical application of granisetron for acute and delayed CINV, and to make its release more stable and its use safer, a granisetron sustained-release microsphere formulation is proposed. After in vivo injection, the granisetron microspheres will be slowly released over 7 days, resulting in stable blood drug concentrations, low irritation, and the ability to prevent acute and delayed nausea and vomiting caused by chemotherapy with a single dose, thereby reducing the frequency of medication use and improving patient adherence.

[0006] Chinese patent CN109718225A describes a granisetron sustained-release microsphere and its preparation method. This patent uses an O / W emulsification-solvent evaporation method to prepare the microspheres, with a D50 of 50–105 μm, and can achieve sustained release in vitro for one month. However, it does not disclose in vivo data to confirm the sustained-release effect. The encapsulation efficiency shown in the patent is low, only 45%–70%, posing a risk of burst release in vivo. Simultaneously, due to the low drug loading (approximately 0.89%–3%), the injection volume of microspheres needs to be increased to achieve a clinically effective dose, increasing the difficulty of administration. The larger microsphere particle size also easily causes local irritation. Microscopic images provided in the patent show that the microspheres are not perfectly round, with surface depressions and channels, posing risks to the stability and uniformity of drug release in vivo. Summary of the Invention

[0007] In response to the problems existing in the prior art, this application provides, in a first aspect, granisetron sustained-release microspheres, wherein, based on 100% by weight of granisetron sustained-release microspheres, the content of granisetron or its pharmaceutically acceptable salt is 3-12%, the content of stabilizer is 1-25%, and the content of biodegradable polymer is 65-96%, wherein the biodegradable polymer is polylactic acid-glycolic acid copolymer, and the stabilizer is fatty acid.

[0008] Furthermore, the stabilizer is selected from one or more of palmitic acid, octanoic acid, or oleic acid.

[0009] Furthermore, the polylactic acid-glycolic acid copolymer has a molecular weight of 3,000 to 40,000 Daltons, and the molar ratio of lactic acid to glycolic acid in the polylactic acid-glycolic acid copolymer is (50 to 75):(25 to 50).

[0010] On the other hand, the present invention provides a method for preparing granisetron sustained-release microspheres, wherein granisetron or its pharmaceutically acceptable salt, a biodegradable polymer and a stabilizer are dissolved in an organic solvent to prepare an oil phase solution; under shear conditions, the oil phase solution is added to an aqueous phase to form an O / W type emulsion; the solvent in the emulsion is removed and dried to obtain granisetron sustained-release microspheres;

[0011] The oil phase comprises the following raw materials in parts by weight: 0.1 to 1.0 parts of granisetron or its pharmaceutically acceptable salt, 0.03 to 1.0 parts of stabilizer, and 1 to 5 parts of biodegradable polymer.

[0012] Further, the mass ratio of the granisetron or its pharmaceutically acceptable salt to the polylactic acid-glycolic acid copolymer is 1:(2-10).

[0013] Furthermore, it also includes the following steps: adjusting the pH value of the aqueous phase; the aqueous phase is an aqueous solution of polyvinyl alcohol.

[0014] Furthermore, the concentration of the polyvinyl alcohol aqueous solution is 0.05–1.2%.

[0015] Furthermore, the pH value of the aqueous phase is 6.0 to 10.0.

[0016] Furthermore, the shear rate of the emulsification is 3000 rpm / 2 min to 8000 rpm / 2 min.

[0017] Furthermore, the granisetron sustained-release microspheres obtained according to the above method have a drug loading of 3% to 10%, an encapsulation efficiency of ≥90%, a microsphere particle size of D50 of 5 to 30 μm, D10 of less than or equal to 10 μm, and D90 of 10 to 50 μm.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] (1) The granisetron sustained-release microspheres of the present invention have high drug loading, uniform particle size, complete morphology and no adhesion, and smooth surface without obvious pores under high encapsulation rate. These characteristics not only reduce the risk of burst release and drug leakage, but also enable sustained release in vitro for up to 5 to 7 days.

[0020] (2) Compared with commercially available granisetron hydrochloride injection, the microspheres of the present invention can slowly and persistently release the drug in vivo, achieving a sustained release effect of 5-7 days with a single dose. This not only reduces the number of injections but also lowers the incidence of adverse reactions and significantly improves patient compliance. Furthermore, in vivo pharmacokinetic experiments in beagle dogs show that the AUC of the granisetron sustained-release microspheres of the present invention is significantly lower than that of commercially available granisetron hydrochloride injection. 0-t The drugs were similar in their exposure levels in animals and were able to significantly reduce C. max , extend T max and t 1 / 2 These results fully demonstrate its significant sustained-release properties.

[0021] (3) In the in vivo pharmacokinetic experiment of beagle dogs, the microspheres of the present invention were easily dispersed after shaking in the accompanying solvent, and no needle blockage occurred. The needle passage was good, indicating that the microspheres obtained by the present invention had no obvious adhesion and clumping, and had good fluidity, which ensured the smooth administration of the drug.

[0022] (4) The granisetron sustained-release microspheres described in this invention not only have a simple composition, but also provide a simple and easy preparation method, making them suitable for large-scale industrial production. This not only reduces production costs, but also improves production efficiency and product quality.

[0023] In summary, this invention provides a safer, more effective, and patient-friendly drug delivery system for the clinical application of granisetron, which is expected to improve the patient's treatment experience and bring significant progress to the medical field. Attached Figure Description

[0024] Figure 1: Surface morphology of the microspheres obtained in Comparative Example 1.

[0025] Figure 2: Surface morphology of microspheres obtained in Examples 1, 2, and 3 (left: Example 1, left 2: Example 2, right: Example 3).

[0026] Figure 3: Surface morphology of microspheres obtained in Comparative Examples 2 and Examples 4-6 (Top left: Comparative Example 2, Top right: Example 4, Bottom left: Example 5, Bottom right: Example 6).

[0027] Figure 4: Surface morphology of microspheres obtained in Examples 7-8 and Example 23 (left: Example 7, left: Example 8, right: Example 23).

[0028] Figure 5: Surface morphology of microspheres obtained in Examples 13-17 and Comparative Example 3 (First row from left to right: Example 13, Example 14, Example 15; Second row from left to right: Example 16, Example 17, Comparative Example 3).

[0029] Figure 6: Semi-logarithmic curve of granisetron concentration in plasma after subcutaneous injection of commercially available granisetron hydrochloride injection in beagle dogs.

[0030] Figure 7: Semi-logarithmic curve of granisetron concentration in plasma after subcutaneous injection of different doses of granisetron sustained-release microspheres obtained in Example 14 in beagle dogs. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0032] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0034] Granisetron, as a first-generation 5-HT3 receptor antagonist, has good efficacy, but frequent dosing is required in clinical applications to achieve therapeutic concentrations. To overcome this limitation, granisetron is formulated into microspheres, allowing for slow drug release, thereby prolonging the duration of action, reducing fluctuations in blood drug concentration, improving efficacy and patient compliance, and reducing the risk of adverse reactions. However, due to the inherent properties of granisetron, such as the presence of basic groups that lead to the degradation of polylactic-co-glycolic acid copolymers, the prepared microspheres have rough and porous surfaces. These problems may affect the drug loading, encapsulation efficiency, and initial drug release rate of the microspheres. This invention addresses the problems of existing technologies by conducting in-depth research and exploration to obtain granisetron microspheres with more complete morphology and excellent properties. Specifically:

[0035] The granisetron sustained-release microspheres comprise, based on 100% by weight of the granisetron sustained-release microspheres, 3-12% granisetron or a pharmaceutically acceptable salt thereof, 1-25% stabilizer, and 65-96% biodegradable polymer. Preferably, the content of granisetron or a pharmaceutically acceptable salt thereof is 3-10%, the content of stabilizer is 1-20%, and the content of biodegradable polymer is 70-96%. More preferably, the content of granisetron or a pharmaceutically acceptable salt thereof is 5-9%, the content of stabilizer is 2-20%, and the content of biodegradable polymer is 71%-93%. Even more preferably, the content of granisetron or a pharmaceutically acceptable salt thereof is 5-9%, the content of stabilizer is 2-20%, and the content of biodegradable polymer is 74%-92%.

[0036] In one embodiment of the present invention, the biodegradable polymer is polylactic acid-glycolic acid copolymer (hereinafter referred to as "PLGA"), and the stabilizer is a fatty acid.

[0037] In one embodiment of the present invention, the stabilizer is selected from one or more of palmitic acid, octanoic acid, or oleic acid.

[0038] Pharmaceutically acceptable salts of granisetron may be selected from the following: hydrochloride, mesylate, citrate, nitrate, lactate, maleate, tartrate, phosphate, succinate, fumarate, and gluconate.

[0039] In this invention, the introduction of fatty acids significantly improves the surface morphology of granisetron sustained-release microspheres. This improvement may stem from the enhancing effect of fatty acids on the structural stability and compactness of the microspheres, thereby effectively reducing drug leakage during preparation and storage. Furthermore, the smooth surface structure of the microspheres also reduces drug surface adsorption, which is of great significance for reducing the risk of adverse reactions caused by burst release during clinical use.

[0040] In one embodiment of the present invention, the molecular weight of the PLGA is 3,000 to 40,000 Daltons, preferably 4,000 to 38,000 Daltons, more preferably 7,000 to 38,000 Daltons, and the molar ratio of lactic acid (hereinafter referred to as "LA") to glycolic acid (hereinafter referred to as "GA") is (50 to 75):(25 to 50), preferably 50:50.

[0041] This invention does not limit the type or method of PLGA use; it can be from any manufacturer and / or any model, and can also be used in combination. For example, PLGA with a LA to GA molar ratio of 50:50 can be mixed with PLGA with a molar ratio of 75:25. The mixing ratio can be 1:0.5, 1:1, 1:2, or any other ratio, as long as it meets the requirements for preparing granisetron sustained-release microspheres.

[0042] PLGA is a biodegradable polymer material copolymerized from lactic acid (LA) and glycolic acid (GA) monomers. The LA to GA ratio is a key factor affecting the release behavior of PLGA microspheres. Because the methyl groups in the LA molecule hinder the hydrolysis of ester bonds, a higher LA ratio in PLGA reduces its hydrophilicity, thus slowing down its degradation rate. Furthermore, the molecular weight of PLGA is also an important factor affecting microsphere quality. Lower molecular weight PLGA has shorter molecular chains, resulting in shorter degradation times and faster degradation rates. This is because lower molecular weight PLGA molecules have less physical entanglement, allowing for faster pore formation during hydration, thereby accelerating oligomer formation and shortening degradation time.

[0043] Therefore, the ratio of LA to GA and the molecular weight of PLGA have a significant impact on the drug loading, drug release kinetics and other related factors of granisetron sustained-release microspheres. This helps to regulate drug release, reduce the risk of adverse reactions caused by drug burst release, and improve patient compliance.

[0044] In one embodiment of the present invention, a method for preparing granisetron microspheres more suitable for use is provided. The specific preparation method is as follows: dissolving granisetron or its pharmaceutically acceptable salt, a biodegradable polymer, and a stabilizer in an organic solvent to prepare an oil phase solution; adding the oil phase solution to an aqueous phase under shear conditions to form an O / W type emulsion; removing the solvent from the emulsion and drying to obtain granisetron sustained-release microspheres;

[0045] The oil phase comprises, by weight, 0.1 to 1.0 parts of granisetron or a pharmaceutically acceptable salt thereof, 0.03 to 1.0 parts of stabilizer, and 1 to 5 parts of biodegradable polymer; preferably, 0.2 to 1.0 parts of granisetron or a pharmaceutically acceptable salt thereof, 0.04 to 0.55 parts of stabilizer, and 1.5 to 2.0 parts of biodegradable polymer.

[0046] In one embodiment of the present invention, the amount of fatty acids in the oil phase can be 1-20%, preferably 2-20%, for example 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] In one embodiment of the invention, the mass ratio of granisetron or its pharmaceutically acceptable salt (API) to PLGA is 1:(2-10), preferably 1:(2-7), and more preferably 1:(5-7), for example 1:5, 1:6 or 1:7, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] This invention does not limit the type of aqueous phase. The aqueous phase may contain other substances, such as surfactants, thickeners and stabilizers, electrolytes, pH adjusters and / or preservatives, as long as they can serve as a continuous phase in the oil-in-water emulsion, surrounding the oil droplets dispersed therein, so that the emulsion has good fluidity and uniformity. The substances in the aqueous phase can be arbitrarily selected from the above types.

[0049] The surfactant can be selected from common surfactants in the art, such as sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol, Tween 20, Tween 80, or polyoxyethylene ether.

[0050] The thickener and stabilizer can be selected from common thickeners and stabilizers in the art, such as polyvinyl alcohol, sodium carboxymethyl cellulose, xanthan gum, sodium alginate, and sodium polyacrylate.

[0051] The electrolyte can be selected from common electrolytes in the field, such as sodium chloride and sodium sulfate.

[0052] pH adjusters can be selected from common pH adjusters in this field, such as citric acid, 10% hydrochloric acid solution, 0.1M sodium hydroxide solution, or 20mM phosphate.

[0053] Preservatives can be selected from common preservatives in this field, such as parabens, potassium sorbate, and sodium benzoate.

[0054] In one embodiment of the present invention, the method further includes the following step: adjusting the pH value of the aqueous phase; wherein the aqueous phase is an aqueous solution of polyvinyl alcohol.

[0055] The aqueous phase described in this invention specifically refers to the external aqueous phase used in the formation of O / W emulsions (i.e., oil-in-water emulsions). pH adjustment of the aqueous phase can be performed at any stage of the microsphere preparation process, such as during the preparation of the aqueous solution, the emulsion preparation process, the removal of the emulsion, or even before microsphere formation.

[0056] The present invention does not limit the solvent used to adjust the pH. It can be citric acid, 10% hydrochloric acid solution, 0.1M sodium hydroxide solution or 20mM phosphate, as long as the predetermined pH value can be achieved.

[0057] In one embodiment of the present invention, the organic solvent may be a common organic solvent in the art, such as dichloromethane, ethyl acetate, N,N-dimethylformamide, tetrahydrofuran, acetone or isopropanol. The present invention does not limit the type of organic solvent, as long as it can fully dissolve the raw materials in the oil phase, is safe, and has good stability.

[0058] In one embodiment of the present invention, the concentration of the PVA solution is 0.05% to 1.2%, preferably 0.1% to 1%, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The PVA concentration refers to the mass of PVA contained in the aqueous phase, i.e., the mass-volume percentage concentration (w / v).

[0059] PVA, as a surfactant, helps in the formation and stability of emulsion droplets during oil-water phase mixing. PVA concentration has no significant effect on the morphology and quality of granisetron sustained-release microspheres.

[0060] In one embodiment of the present invention, the method for preparing the granisetron sustained-release microspheres includes the following steps:

[0061] (1) Preparation of oil phase: Add the active ingredient (API), PLGA and fatty acid to dichloromethane and stir until dissolved to prepare an oil phase solution.

[0062] (2) Aqueous phase preparation: The aqueous solution of polyvinyl alcohol is adjusted to a specific pH using phosphate solution to form an aqueous phase solution.

[0063] (3) Emulsification: Under high-speed shear conditions, the oil phase is added to the water phase to form a uniform O / W type emulsion.

[0064] (4) Curing: The solvent in the solution obtained in step (3) is removed by rotary evaporation at 30°C for 4 hours. Rotary evaporation speed: 100 rpm.

[0065] (5) Collecting microspheres: After the curing is completed, filter the microspheres to remove the aqueous solvent and wash the microspheres with deionized water. Collect the microspheres and freeze-dry them under vacuum to obtain the microspheres.

[0066] In one embodiment of the present invention, the freeze-drying is a process in which a substance containing water is first frozen into a solid state, and then the ice is directly sublimated into a gaseous state under vacuum conditions, thereby removing the water.

[0067] In one embodiment of the present invention, the pH value of the aqueous phase (hereinafter also referred to as "external aqueous phase pH value") is 6.0 to 10.0, preferably 6.0 to 9.0, such as 6.0, 7.0, 8.0 or 9.0, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0068] In the preparation of granisetron sustained-release microspheres, the pH of the external aqueous phase significantly affects the quality of the microspheres, especially before microsphere formation. When the pH of the external aqueous phase is low, granisetron has higher solubility in the aqueous phase under acidic conditions, causing the drug to diffuse from the oil phase to the aqueous phase during the emulsification process and the initial stage of solidification, which may reduce the drug loading of the microspheres. Conversely, when the pH is greater than 10, PLGA is more easily degraded under alkaline conditions, which affects the structural integrity of the microspheres as well as their drug loading and encapsulation efficiency.

[0069] Furthermore, pH also affects the degradation mechanism of PLGA molecules. Under neutral or slightly acidic conditions, PLGA degradation is random and accompanied by chain-end cleavage events. However, under strongly alkaline conditions, PLGA degradation is primarily determined by rapid chain-end cleavage. Therefore, maintaining an appropriate pH range is crucial for balancing the solubility of granisetron and the stability of PLGA, which helps ensure optimal drug loading and quality of granisetron sustained-release microspheres.

[0070] In one embodiment of the present invention, the emulsification shear rate can be from 3000 rpm / 2 min to 8000 rpm / 2 min, for example 3000 rpm / 2 min, 4000 rpm / 2 min, 5000 rpm / 2 min, 6000 rpm / 2 min, 7000 rpm / 2 min or 8000 rpm / 2 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0071] The shear rate during emulsification has a significant impact on the quality of granisetron sustained-release microspheres. A suitable shear rate promotes the formation of uniform and smaller droplets, resulting in microspheres of appropriate size.

[0072] In one embodiment of the present invention, the drug loading of the microspheres is 3% to 10%, preferably 5% to 9%, the encapsulation efficiency is ≥90%, the particle size D50 is 5 to 30 μm, D10 is less than or equal to 10 μm, and D90 is 10 to 50 μm.

[0073] Microsphere morphology and particle size: The morphology of microspheres is of great significance in the preparation process, as it directly affects the release behavior and stability of the microspheres. The ideal microsphere should be a round or elliptical solid with a full shape, and the particle size should be as uniform as possible, without forming large clumps, and without adhesion between microspheres.

[0074] The particle size and distribution of microspheres significantly affect drug release behavior. Uniformly sized microspheres provide more stable drug release characteristics, reduce inter-individual variability, and improve the predictability of therapeutic effects. The granisetron sustained-release microspheres obtained in this invention have a D50 of 5–30 μm, a D10 of ≤10 μm, and a D90 of 10–50 μm. The particle size distribution does not show significant broadening, indicating no adhesion between the microspheres.

[0075] Drug loading refers to the weight percentage of drug contained in a microsphere formulation. It is directly related to the efficacy and safety of the drug and is an important parameter for evaluating the effectiveness of microsphere formulations. A higher drug loading means that a single microsphere contains more drug, which may increase the drug release rate, but may also increase the risk of side effects. The granisetron sustained-release microspheres prepared in this invention have a drug loading of 3% to 10%, ensuring both drug efficacy and safety.

[0076] Encapsulation efficiency refers to the ratio of the amount of drug encapsulated in a microsphere formulation to the total amount of drug encapsulated and unencapsulated in the microsphere formulation. A high encapsulation efficiency means that more drug is successfully encapsulated inside the microspheres, which helps improve drug stability and controlled release. According to the "Guidelines for Microparticle Formulations" in the 2020 edition of the Chinese Pharmacopoeia, the encapsulation efficiency should generally not be less than 80%. The granisetron sustained-release microspheres prepared in this invention have an encapsulation efficiency of not less than 90%, which helps improve the stability of the formulation and the reliability of clinical applications.

[0077] Sustained-release formulations are preparations that continuously release drugs over a prolonged period to achieve a long-lasting effect. Compared to conventional formulations, sustained-release formulations can maintain effective blood drug concentrations for a longer time and reduce fluctuations in blood drug concentrations, thereby prolonging the duration of drug action, reducing adverse drug reactions, decreasing dosing frequency, and improving patient compliance. This formulation form is suitable for diseases requiring long-term maintenance of therapeutic effects. However, burst release is a key consideration in the development and evaluation of sustained-release formulations. During in vitro release tests, the drug adsorbed on the surface is rapidly released, a phenomenon known as the burst release effect. According to the "Guidelines for Microparticle Formulations" in the 2020 edition of the Chinese Pharmacopoeia, the release amount of microparticle formulations should be less than 40% within the first 0.5 hours. The granisetron sustained-release microspheres obtained in this invention release no more than 30% of the drug within 12 hours, preferably no more than 25%, which not only effectively avoids burst release but also maintains stable blood drug concentrations.

[0078] The determination and preparation methods of granisetron sustained-release microspheres in the embodiments and comparative examples of the present invention are as follows:

[0079] Methods for determining the drug loading and component content of granisetron sustained-release microspheres:

[0080] Weigh 20 mg of the preparation and place it in a 10 ml volumetric flask. Add an appropriate amount of acetonitrile and sonicate for 20 min. Make up to volume with acetonitrile, mix well, centrifuge at 8000 rpm, and collect the supernatant. Accurately measure 5 ml of the supernatant into a 25 ml volumetric flask and dilute to the mark with acetonitrile-water (20:80 v / v). Filter through a 0.45 μm filter membrane. Measure the peak area of ​​the filtrate using high performance liquid chromatography at a detection wavelength of 305 nm. Separately, accurately weigh an appropriate amount of the reference standard and determine it using the same method. Calculate the drug loading and the content of each component using the external standard method.

[0081] Drug loading = (Weight of drug contained in microspheres / Total weight of microspheres) * 100%

[0082] Method for determining the encapsulation efficiency of granisetron sustained-release microspheres:

[0083] Weigh 50 mg of the preparation and place it in a 100 ml volumetric flask. Accurately add 25 ml of 0.1 mol / L phosphate buffer. Place the flask in a shaking water bath at 25°C and shake at 100 rpm for 15 minutes. Remove the flask, filter it, and collect the filtrate. Detect the amount of free drug and further convert it into the drug encapsulation efficiency.

[0084] Encapsulation efficiency = (Weight of drug encapsulated in microspheres / Total amount of drug encapsulated and unencapsulated in microspheres) * 100%

[0085] In vitro release assay method for granisetron sustained-release microspheres:

[0086] Drug release was determined using the shaker method, with 3 ml of pH 7.4 PBS buffer as the release medium. The medium temperature was 37℃ ± 0.5℃, and the rotation speed was 100 rpm. 20 mg of the formulation was added to a centrifuge tube containing the release medium and placed in a water bath with constant temperature shaking. Each sample was tested in triplicate. All release medium (3 ml) was collected at 2 h, 12 h, 1 d, 2 d, 3 d, 4 d, 5 d, 6 d, and 7 d, and an equal volume of fresh medium at the same temperature was added. The sample was filtered through a 0.45 μm microporous membrane, and the peak area of ​​the filtrate was determined by high-performance liquid chromatography (HPLC) at a detection wavelength of 305 nm. A suitable amount of reference standard was accurately weighed and determined using the same method. The cumulative release rate was calculated using the external standard method and should meet the specified requirements.

[0087] Methods for determining the particle size and particle size distribution of granisetron sustained-release microspheres:

[0088] Weigh 200 mg of granisetron sustained-release microspheres and add 20 mL of 0.1% Tween 80 aqueous solution. Disperse the microspheres by ultrasonication at 200 W for 2 min. After dispersion, use a laser particle size diffractometer to determine the particle size and particle size distribution.

[0089] Microsphere particle size distribution data are expressed as the number of particles or percentage within each particle size range; at the same time, the span is used to represent the particle size distribution. The smaller the span, the narrower the distribution, that is, the more uniform the particle size.

[0090] Span = (D 90 -D 10 ) / D 50

[0091] In the formula D 10 D 50 D 90 These refer to the particle sizes corresponding to 10%, 50%, and 90% of the cumulative particle size distribution map, respectively.

[0092] The preparation process of granisetron sustained-release microspheres is as follows:

[0093] (1) Oil phase preparation: Add the active ingredient (API), PLGA and fatty acids to dichloromethane and stir until dissolved.

[0094] (2) Aqueous phase preparation: The aqueous solution of polyvinyl alcohol (PVA) was adjusted to a specific pH value using a phosphate solution.

[0095] (3) Emulsification: Under high-speed shear conditions, the oil phase is added to the water phase to form a uniform O / W type emulsion.

[0096] (4) Curing: The solvent in the solution obtained in step (3) is removed by rotary evaporation at 30°C for 4 hours. Rotary evaporation speed: 100 rpm.

[0097] (5) Collecting microspheres: After the microspheres have been cured, filter and wash them, collect them into a sample bottle, and freeze-dry them to obtain the microspheres.

[0098] The specific embodiments and comparative examples of the present invention are listed below, but the present invention is not limited to the following examples.

[0099] I. The formulation composition and process parameters are as follows, depending on the different fatty acids and dosages used:

[0100] The content of each component, drug loading, release rate, particle size distribution and appearance of granisetron microspheres obtained in Examples 1-6 and Comparative Examples 1-2 were determined.

[0101] 1. Results of component content, drug loading, and encapsulation efficiency of granisetron microspheres obtained in Examples 1-6 and Comparative Examples 1-2

[0102] The contents of each component in the obtained granisetron microspheres are as follows:

[0103] The drug loading and encapsulation efficiency are as follows:

[0104] Based on the drug loading and encapsulation efficiency results of Comparative Example 1 and Examples 1-3, it is evident that the encapsulation efficiency was significantly improved after using fatty acids, all reaching over 90%. However, the drug loading of the microspheres differed slightly; when palmitic acid was used as a stabilizer (Example 1), the drug loading was higher. Although the granisetron microspheres obtained without using fatty acids (as in Comparative Example 1) had a drug loading of 8.1%, the encapsulation efficiency was lower, at only 84%. The improved encapsulation efficiency indicates that there is less free drug in the microspheres, and more drug is successfully encapsulated within them. This has positive implications for reducing the risk of adverse reactions caused by drug burst release during clinical use.

[0105] Further comparison of fatty acid dosages revealed that, based on the drug loading and encapsulation results of Comparative Example 2, Example 1, and Examples 4-6, a dosage of palmitic acid of 2% to 20% could ensure an encapsulation rate of over 90% and a high drug loading level.

[0106] 2. The release rates (%) of granisetron microspheres obtained in Examples 1-6 and Comparative Examples 1-2 are as follows:

[0107] Based on the release results of Comparative Example 1 and Examples 1-3, it can be seen that the microspheres obtained in Comparative Example 1 have a significantly higher drug release in the first 12 hours, while the microspheres prepared using different fatty acids have a significantly lower drug release in the first 12 hours, and the subsequent release remains stable and unaffected. At the same time, the release rates of microspheres obtained from different fatty acids are similar, indicating that fatty acids can effectively inhibit the burst release of drugs and provide strong support for the stable control of drug release.

[0108] Meanwhile, based on the release rate results of Comparative Example 2, Example 1, and Examples 4-6, it can be seen that when the amount of palmitic acid is between 2% and 20% (as in Examples 1 and 4-6), the drug release rate of the microspheres in the initial stage can be maintained within a relatively ideal range. Furthermore, as time progresses, the drug release becomes more stable, which not only helps ensure the continuity of drug efficacy but also improves the safety of medication. However, when the amount of palmitic acid is 1% (as in Comparative Example 2), the release of the microspheres exceeds 30% within 12 hours, indicating an excessively rapid release rate.

[0109] 3. The particle size and particle size distribution of the granisetron sustained-release microspheres in Examples 1-6 and Comparative Examples 1-2 are as follows:

[0110] Based on the particle size and particle size distribution results of Comparative Example 1 and Examples 1-3, it can be seen that, compared with Comparative Example 1 which did not use fatty acids, the formulation that introduced fatty acid components not only had a smaller D50, but also a more concentrated particle size distribution range. At the same time, when the amount of palmitic acid was 2% to 20% (as in Examples 1, 4-6), the microspheres obtained had a smaller D50 and a more concentrated distribution range.

[0111] 4. Surface morphology of granisetron sustained-release microspheres obtained in Examples 1-6 and Comparative Examples 1-2:

[0112] The surface morphology of the microspheres was observed using scanning electron microscopy. Figure 1 shows the surface morphology of the microspheres in Comparative Example 1 without fatty acids as stabilizers. The microspheres in Comparative Example 1 exhibit irregular depressions, are predominantly elliptical in shape, and have noticeable pores. These characteristics may affect the stability of the microspheres and the drug encapsulation efficiency. The surface morphology of Examples 1-3 is shown in Figure 2. Microspheres prepared using different fatty acids as stabilizers all have smooth surfaces and round shapes. The surface morphology of Comparative Example 2 and Examples 4-6 is shown in Figure 3. When using low concentrations (1%, Comparative Example 2) of palmitic acid as a stabilizer, the microsphere morphology is significantly improved, but some microspheres are still not round and have rough surfaces. Microspheres prepared using 2%–20% palmitic acid as a stabilizer all have smooth surfaces and round shapes.

[0113] In summary, the introduction of fatty acids had a positive impact on the preparation of granisetron sustained-release microspheres. The addition of fatty acids significantly improved the performance of the microspheres in terms of appearance, particle size distribution, encapsulation efficiency, drug loading, and release rate. In particular, when the amount of fatty acids was controlled within the range of 2% to 20%, the granisetron sustained-release microspheres exhibited excellent quality and efficacy. This range of fatty acid content not only ensured the physical properties of the microspheres, such as a perfectly spherical shape and uniform particle size distribution, but also prevented significant widening of the particle size distribution, and the microspheres did not stick together, exhibiting good flowability. Furthermore, the introduction of fatty acids significantly improved the encapsulation efficiency, thereby ensuring the continuous and stable release of the drug.

[0114] II. Using different PLGA models and different APIs: PLGA ratios, PLGA information is as follows:

[0115] 1. The formulation composition and process parameters of Examples 7-12 and Example 23 are as follows:

[0116] The content of each component, drug loading, release rate, particle size distribution and appearance of granisetron microspheres obtained in Examples 7-12 and Example 23 were determined.

[0117] 1. Results of the content, drug loading, and percentage of each component of granisetron microspheres obtained in Examples 1, 7-12, and 23.

[0118] The contents of each component in the obtained granisetron microspheres are as follows:

[0119] The drug loading and encapsulation efficiency are as follows:

[0120] As can be seen from the drug loading and encapsulation efficiency of the microspheres in Examples 23, 1, and 7-8, the ratio of LA to GA in the PLGA polymer has a significant impact on the drug loading. Examples 1 and 23 used PLGA materials with similar molecular weights. Under the same conditions, when the ratio of LA to GA in the PLGA was 75:25 (Example 23), the drug loading of the prepared microspheres was 4.3%, slightly lower than in the other examples. In contrast, the ratio of LA to GA in the PLGA polymer used in Examples 1 and 7-8 was 50:50, and the drug loading of the prepared microspheres was 6.2%–7.1%.

[0121] Based on the drug loading results of Examples 9-12, it can be seen that, under the same conditions, when the API:PLGA ratio is 1:10 to 1:2 (as in Examples 9-12), the obtained microspheres can achieve a high drug loading with a high encapsulation efficiency. When the API:PLGA ratio is 1:10 (Example 12), the drug loading of the microspheres is slightly lower, but still reaches 5.5%. When the API:PLGA ratio is 1:7 to 1:2 (as in Examples 9-11), the drug loading of the obtained microspheres is even higher, at 7.9% to 8.9%.

[0122] 2. The release rate (%) of granisetron microspheres obtained in Examples 1, 7-12 and 23 are as follows:

[0123] Analysis of the release results from Examples 23, 1, and 7-8 shows that the molecular weight of the PLGA polymer and the ratio of LA to GA significantly affect the release behavior. Examples 1 and 23 used PLGA materials with similar molecular weights, but the results showed that when the LA to GA ratio in the PLGA was 75:25 (Example 23), the prepared microspheres exhibited a slower release characteristic in in vitro experiments, releasing approximately 50% of the drug within 7 days. However, when the LA to GA ratio in the PLGA was 50:50 (Example 1), the release of the prepared microspheres in in vitro experiments was more ideal, reaching 87.1% within 7 days.

[0124] Further investigation into the effect of PLGA molecular weight revealed that the ratio of LA to GA in the PLGA used in Examples 1 and 7-8 was 50:50. The results showed that the prepared microspheres all met the requirement of slow release within 7 days. Therefore, a 50:50 ratio of LA to GA in the PLGA can effectively ensure the slow and effective release of the microspheres within 7 days, while a 75:25 ratio of LA to GA in the PLGA can achieve an even slower release of the microspheres.

[0125] These results indicate that the molecular weight of PLGA and the ratio of LA to GA are key factors affecting the release behavior of microspheres. Optimizing these two parameters can significantly improve the sustained-release effect of microspheres, ensuring stable and long-lasting drug release in vivo.

[0126] Analysis of the release results in Examples 9-12 shows that when the API:PLGA ratio is 1:10 to 1:2, the release behavior of the resulting microspheres is slow but effective. API:PLGA ratios within this range ensure continuous and stable drug release in vivo, thereby improving therapeutic efficacy and patient safety.

[0127] 3. The particle size and particle size distribution of the granisetron sustained-release microspheres obtained in Examples 1, 7-12 and 23 are as follows:

[0128] Based on the above particle size and particle size distribution results, it can be seen that the characteristics of PLGA polymer and the change in API:PLGA ratio have little impact on the particle size and particle size distribution results, and the D50 is small and the distribution is relatively concentrated.

[0129] 4. Surface morphology of granisetron sustained-release microspheres obtained in Examples 1, 7-8 and 23:

[0130] The surface morphology of the microspheres was observed using a scanning electron microscope. The surface morphology of the microspheres in Example 1 is shown in Figure 2. Figure 4 shows the surface morphology of the microspheres obtained using different PLGAs in Examples 23 and 7-8. It can be seen that the surface of the microspheres is smooth, the morphology is more rounded, and the surface structure is more uniform.

[0131] In summary, the granisetron sustained-release microspheres prepared using PLGA with different properties exhibit excellent performance in several key quality attributes, including uniform spherical appearance, concentrated particle size distribution, high encapsulation efficiency, and high drug loading. Differences in the ratio of LA to GA and their molecular weight both lead to variations in release rate. These characteristics collectively ensure the superior quality and efficacy of the granisetron sustained-release microspheres, thus providing patients with a more reliable and effective treatment option.

[0132] The ratio of API to PLGA is equally important. When the ratio is between 1:10 and 1:2, the prepared microspheres not only have higher encapsulation efficiency and drug loading, but also exhibit slow and efficient release behavior. This ratio range ensures sustained and stable drug release in vivo, thereby improving therapeutic efficacy and patient safety.

[0133] III. The formulation composition and process parameters are as follows when using different external aqueous phase pH:

[0134] The content of each component, drug loading, release rate, particle size distribution and appearance of the granisetron microspheres obtained in Examples 13-17 and Comparative Example 3 were determined.

[0135] 1. The content of each component, drug loading, and encapsulation efficiency of the granisetron microspheres obtained in Examples 1, 13-17, and Comparative Example 3 are as follows:

[0136] The contents of each component in the obtained granisetron microspheres are as follows:

[0137] The drug loading and encapsulation efficiency are as follows:

[0138] Based on the drug loading and encapsulation efficiency results of Comparative Example 3, Example 1, and Examples 13-17, it can be seen that within the external aqueous phase pH range of 6.0-10.0, the encapsulation efficiency exceeded 90%, and the drug loading reached 5.5% or higher. There is a certain positive correlation between the drug loading and pH value; within a certain range, the drug loading of the microspheres increases accordingly with increasing pH. However, when the pH value is 11 (as in Comparative Example 3), it may be because PLGA is easily degraded under alkaline conditions, leading to a decrease in both the drug loading and encapsulation efficiency of the microspheres.

[0139] 2. The release rate (%) of granisetron microspheres obtained in Examples 1, 13-17 and Comparative Example 3 is as follows:

[0140] Based on the release rate results of Comparative Example 3, Example 1, and Examples 13-17, it can be seen that when the external aqueous phase has a pH of 6.0-10.0 (as in Examples 1 and 13-17), the release rate of the microspheres is similar, with a release rate of less than 30% within 12 hours. When the external aqueous phase has a pH of 6.0-9.0, the release rate of the microspheres is less than 25% within 12 hours. When the external aqueous phase has a pH of 10.0, the release of the microspheres accelerates within 12 hours, but is still below 30%. When the external aqueous phase has a pH of 11.0 (as in Comparative Example 3), the release rate of the microspheres is relatively fast.

[0141] 3. The particle size and particle size distribution of the granisetron sustained-release microspheres obtained in Examples 1, 13-17 and Comparative Example 3 are as follows:

[0142] Based on the particle size and particle size distribution results of Comparative Example 3, Example 1, and Examples 13-17, it can be seen that the pH value of the external aqueous phase does not affect the particle size of the microspheres, and the D50 is relatively small and the distribution is relatively concentrated.

[0143] 4. Surface morphology of granisetron sustained-release microspheres obtained in Examples 13-17 and Comparative Example 3:

[0144] The surface morphology of Comparative Example 3 and Examples 13-17 is shown in Figure 5. The microspheres prepared using solutions with pH values ​​of 6.0-10.0 (Examples 13-17) all had smooth surfaces, round shapes, and no pores, which is beneficial for maintaining the integrity and stability of the microspheres. However, the microspheres prepared using a solution with a pH value of 11.0 (Comparative Example 3) had small pores. This structural change is likely the direct cause of the accelerated release rate of the microspheres under this condition.

[0145] In summary, the pH value of the external aqueous phase is a key factor affecting the drug loading, encapsulation efficiency, and drug release behavior of PLGA microspheres. In formulation processes, precise pH control is crucial for optimizing microsphere performance and ensuring efficient drug delivery. Furthermore, maintaining a suitable pH range helps preserve the physical integrity of the microspheres, preventing the formation of surface pores due to excessively rapid material degradation.

[0146] IV. Microspheres were prepared using different emulsification speeds. The formulation composition and process parameters are as follows:

[0147] The content of each component, drug loading, release rate, particle size distribution and appearance of the granisetron microspheres obtained in Examples 18 and 19 were determined.

[0148] 1. Results of the content, drug loading, and percentage of each component of the granisetron microspheres obtained in Examples 11, 18, and 19

[0149] The contents of each component in the obtained granisetron microspheres are as follows:

[0150] The drug loading and encapsulation efficiency are as follows:

[0151] 2. The release rates (%) of granisetron microspheres obtained in Examples 11, 18, and 19 are as follows:

[0152] 3. The particle size and particle size distribution of the granisetron sustained-release microspheres obtained in Examples 11, 18, and 19 are as follows:

[0153] According to the research data from Examples 11, 18, and 19, the drug loading of microspheres during emulsification preparation showed a negative correlation with shear rotation speed. When the emulsification speed increased from 3000 rpm / 2 min to 8000 rpm / 2 min, the drug loading of the microspheres decreased slightly, but still remained within the ideal range of 7.0% to 8.9%. This drug loading level indicates that although increasing the shear rotation speed has some impact on the drug loading, the microspheres can still maintain a high drug loading within this speed range.

[0154] Regarding drug release, the release rate of microspheres increases with increasing shear rotation speed. This is because microspheres prepared at high shear rotation speeds have smaller particle sizes, which in turn accelerates the release rate of drug molecules.

[0155] Furthermore, particle size distribution analysis showed that the overall particle size distribution of the microspheres tended to decrease with increasing shear rotation speed. Particle size is a key factor affecting the release rate of microspheres; the reduction in particle size leads to an increase in the specific surface area of ​​the microspheres, which may accelerate the diffusion rate of drug molecules from the interior of the microspheres to the external environment, thereby increasing the release rate.

[0156] In summary, controlling the shear rotation speed plays a crucial role in regulating the drug loading, particle size, and drug release characteristics of microspheres. By optimizing the shear rotation speed during emulsification, the physical properties of microspheres can be precisely controlled, thereby achieving accurate control over drug release behavior. This is of great significance for developing efficient and stable drug delivery systems.

[0157] V. Microspheres were prepared using different PVA concentrations. The formulation composition and process parameters are as follows:

[0158] The content of each component, drug loading, release rate, particle size distribution and appearance of the granisetron microspheres obtained in Examples 20-22 were determined.

[0159] 1. Content of each component, drug loading, and encapsulation efficiency of granisetron microspheres obtained in Examples 16, 20-22

[0160] The contents of each component in the obtained granisetron microspheres are as follows:

[0161] The drug loading and encapsulation efficiency are as follows:

[0162] 2. The particle size and particle size distribution of the granisetron sustained-release microspheres obtained in Examples 20-22 are as follows:

[0163] Based on the drug loading, particle size, and particle size distribution results in Examples 16, 20-22, it can be seen that the PVA concentration has no effect on the drug loading and particle size of the microspheres. When the PVA concentration is between 0.1% and 1.0%, the drug loading and particle size distribution of the obtained microspheres remain in a relatively ideal state.

[0164] VI. Comparison of effects with commercially available formulations

[0165] Example 24: Pharmacokinetic Study of Granisetron Microspheres in Beagle Dogs

[0166] A two-formulation, single-dose, parallel experimental design was adopted, using a commercially available formulation ( (3mL:3mg; Manufacturer: Ningbo Tianheng Pharmaceutical Co., Ltd., Fu'an Pharmaceutical Group; Batch No.: 220611A03) was used as the control formulation, and granisetron sustained-release microspheres from Example 14 were used as the test formulation. Eighteen healthy male beagle dogs aged 6-8 months were randomly divided into two groups of 6 each, with half males and half females. They were fasted for 12 hours before administration, but were allowed free access to water during this period.

[0167] The commercially available formulation is a single intravenous injection of 3 mg. Venous blood samples are collected before administration (0 h) (time is based on the start of the injection) and at 3 min, 6 min (immediately after the injection), 15 min, 30 min, 45 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, and 24 h after administration.

[0168] In Example 14, 3 mg of granisetron sustained-release microspheres were injected subcutaneously. Venous blood samples were collected at 0 h and at 5 min, 15 min, 30 min, 45 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h (1d), 48 h (2d), 72 h (3d), 96 h (4d), 120 h (5d), and 144 h (6d) after administration.

[0169] In Example 14, 10 mg of granisetron sustained-release microspheres were injected subcutaneously. Venous blood samples were collected at 0 h and at 5 min, 15 min, 30 min, 45 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h (1d), 48 h (2d), 72 h (3d), 96 h (4d), 120 h (5d), 144 h (6d), 168 h (7d), and 192 h (8d) after administration.

[0170] In Example 14, 30 mg of granisetron sustained-release microspheres were injected subcutaneously. Venous blood samples were collected at 0 h and at 5 min, 15 min, 30 min, 45 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h (1d), 48 h (2d), 72 h (3d), 96 h (4d), 120 h (5d), 144 h (6d), 168 h (7d), and 192 h (8d) after administration.

[0171] The granisetron sustained-release microspheres in Example 14 were easily dispersed by shaking in the accompanying solvent (a special solvent formulated from sodium carboxymethyl cellulose, mannitol, and polysorbate, used to disperse the microspheres before clinical administration), without agglomeration or needle clogging.

[0172] Place the blood sample in a heparinized centrifuge tube, centrifuge at 4000 rpm for 10 min, collect the supernatant plasma, and store at -70℃ for analysis.

[0173] The plasma concentration-time curves of granisetron in beagle dogs for the commercially available formulation and in Example 11 are shown in Figures 6 and 7, and the pharmacokinetic parameters are shown in the table below.

[0174] ①T max The median of the report

[0175] Comparative pharmacokinetic studies in beagle dogs showed that, compared with granisetron hydrochloride injection... In comparison, after a single subcutaneous injection of the same dose of 3 mg granisetron microspheres into beagle dogs, the plasma C60 of granisetron was significantly lower. max (Maximum blood drug concentration) decreased by approximately 16-fold, t 1 / 2 The half-life was extended by about 12 times. As can be seen from the drug-time curves in Figures 6 and 7, Example 14 significantly prolonged the time to reach the minimum detection limit. After 96 hours of subcutaneous injection, the blood drug concentration decreased to the minimum detection limit, indicating that granisetron microspheres significantly prolonged the drug action time and had a significant sustained-release effect.

[0176] In addition, the peak time of Granstron microspheres (T) max The duration of action was significantly longer than that of commercially available formulations, and the maximum plasma concentration (C) was also significantly increased. max The AUC was significantly reduced, and the AUC was similar, indicating that after subcutaneous injection of granisetron microspheres, the drug exposure in the body was comparable, which could maintain a more stable blood drug concentration, reduce drug concentration fluctuations, and improve the safety and efficacy of drug therapy.

[0177] Multiple dose comparison: As shown in Figure 7, within the dose range of 3 mg to 30 mg, the AUC of beagle dogs... 0-t and C max The drug release is essentially linear, and granisetron microspheres can continuously release the drug for approximately 7 days. This allows granisetron microspheres to be administered only once a week, effectively solving the problem of traditional granisetron requiring multiple dosings.

[0178] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. Granisetron sustained release microspheres characterized in that, Based on 100% by weight of granisetron sustained-release microspheres, the content of granisetron or its pharmaceutically acceptable salt is 3-12%, the content of stabilizer is 1-25%, and the content of biodegradable polymer is 65-96%; the biodegradable polymer is polylactic acid-glycolic acid copolymer, and the stabilizer is fatty acid.

2. Granisetron sustained release microspheres according to claim 1, characterized in that, The stabilizer is selected from one or more of palmitic acid, octanoic acid, or oleic acid.

3. Granisetron sustained release microspheres according to claim 2, wherein The polylactic acid-glycolic acid copolymer has a molecular weight of 3,000 to 40,000 Daltons, and the molar ratio of lactic acid to glycolic acid in the polylactic acid-glycolic acid copolymer is (50 to 75):(25 to 50).

4. A process for the preparation of granisetron sustained release microspheres according to any one of claims 1 to 3, characterized in that, Granisetron or its pharmaceutically acceptable salts, biodegradable polymers, and stabilizers are dissolved in an organic solvent to prepare an oil phase solution; under shear conditions, the oil phase solution is added to an aqueous phase to form an O / W emulsion. The solvent in the emulsion was removed, and after drying, granisetron sustained-release microspheres were obtained. The oil phase comprises, by weight, 0.1 to 1.0 parts of granisetron or a pharmaceutically acceptable salt thereof, 0.03 to 1.0 parts of stabilizer, and 1 to 5 parts of biodegradable polymer.

5. The method of claim 4, wherein the granisetron sustained release microspheres are prepared by the steps of: The mass ratio of the granisetron or its pharmaceutically acceptable salt to the polylactic acid-glycolic acid copolymer is 1:(2-10).

6. The method of claim 4 or 5, wherein the granisetron sustained release microspheres are prepared by the steps of: It also includes the following steps: adjusting the pH value of the aqueous phase; the aqueous phase is an aqueous solution of polyvinyl alcohol.

7. The method of claim 6, wherein the granisetron sustained release microspheres are prepared by the steps of: The concentration of the polyvinyl alcohol aqueous solution is 0.05% to 1.2%.

8. The method of claim 7, wherein the granisetron sustained release microspheres are prepared by the steps of: The pH value of the aqueous phase is 6.0 to 10.

0.

9. The method of claim 8, wherein the granisetron sustained release microspheres are prepared by the steps of: The emulsification shear rate is 3000 rpm / 2 min to 8000 rpm / 2 min.

10. Granisetron sustained release microspheres obtainable by the process according to any one of claims 4 to 9, characterized in that The drug loading of the microspheres is 3% to 10%, the encapsulation efficiency is ≥90%, the microsphere particle size D50 is 5 to 30 μm, D10 is less than or equal to 10 μm, and D90 is 10 to 50 μm.

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