Subcutaneous implants comprising di(hetero)arylic acid ester derivatives of dihydrocannabidiol for the treatment of chronic neuropathic pain, and methods of preparation and use thereof

Abstract

This invention belongs to the field of biomedical technology, specifically relating to a subcutaneous implant containing a dihydrocannabidiol (DHC) di(hetero)carbamate derivative for treating chronic neuropathic pain, its preparation method, and its application. The implant has a reservoir-like structure comprising a hollow capsule made of a biodegradable polymer and poloxamer (terminated with hydroxyl groups) as a pore-forming agent, and a drug composition prepared by co-grinding PSF1-5 compounds and mannitol within the capsule. This invention successfully prepared an implant capable of stable drug release for more than four weeks by dual modification of the drug powder and the polymer capsule, combined with precision filling and heat-sealing processes. Animal experiments show that a single subcutaneous implantation of this implant produces a strong, long-lasting, and dose-dependent analgesic effect, with the PSF1 implant showing the best effect. This invention provides an efficient, safe, and long-acting drug delivery strategy for chronic neuropathic pain.

Description

Technical Field

[0001] This invention belongs to the field of biomedical technology, specifically relating to a subcutaneous implant containing a dihydrocannabidiol di(hetero)carbamate derivative for the treatment of chronic neuropathic pain, its preparation method, and its application. Background Technology

[0002] Chronic neuropathic pain is mostly caused by damage or dysfunction of the nervous system, characterized by hyperalgesia, abnormal pain, and persistent spontaneous pain. It is a protracted and difficult-to-cure condition, and conventional analgesics have limited efficacy. Long-term use can easily lead to drug resistance and organ damage, severely impacting patients' quality of life. Traditional oral and injectable analgesics have limited duration of action, require repeated administration, and exhibit significant fluctuations in blood drug concentrations, making them unsuitable for long-term, stable intervention for chronic pain. Subcutaneous implants, with their advantages of long-acting sustained release, convenient administration, stable efficacy, and fewer systemic adverse reactions, have become a superior form of administration for the long-term treatment of chronic pain.

[0003] Chronic neuropathic pain is pain directly caused by damage or disease of the somatic sensory nervous system. Clinically, it is mainly characterized by hyperalgesia, abnormal pain, and persistent spontaneous pain. Chronic neuropathic pain has a prolonged course, and conventional nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics have limited efficacy. Furthermore, long-term use can easily lead to drug resistance, drug addiction, gastrointestinal and liver and kidney damage, and other serious adverse reactions, severely reducing patients' quality of life.

[0004] Currently, clinical treatment of chronic neuropathic pain mainly relies on oral administration (such as gabapentin) or local injection. However, traditional administration methods have significant drawbacks: first, the duration of action is limited, requiring repeated and multiple doses to achieve sustained analgesia, leading to poor patient compliance; second, blood drug concentrations fluctuate significantly, making it difficult to meet the long-term, stable intervention requirements for chronic pain; and third, systemic administration easily leads to toxic side effects on non-target organs. Therefore, developing a novel analgesic agent that can achieve long-acting, stable, and safe intervention is a pressing technical challenge in this field.

[0005] Subdermal implants, as a type of long-acting sustained-release formulation, rely on the slow degradation of the carrier material or drug diffusion in the body to achieve continuous drug release for weeks or even months. This type of dosage form has advantages such as convenient administration, stable efficacy, and few systemic adverse reactions, making it particularly suitable for the management of chronic diseases requiring long-term medication. However, for chronic neuropathic pain, there are currently no mature subdermal implant products on the market, mainly due to the lack of active drugs that combine high analgesic activity, good stability, and long-lasting effect.

[0006] The applicant has previously developed a series of dihydrocannabidiol di(hetero)carbamate derivatives, namely PSF1-5, see patents CN116983265A (PSF2), CN116983266A (PSF4), CN116983267A (PSF3), CN116983263A (PSF1), and CN116983264A (PSF5). These patents confirm that PSF1-5, as a dihydrocannabidiol di(hetero)carbamate derivative, has a protective effect against oxidative damage to nerve cells and can alleviate insulin resistance. However, the aforementioned prior art does not disclose the analgesic effect of PSF1-5 in the specific disease model of chronic neuropathic pain, nor does it address the development and application of its long-acting formulation as a subcutaneous implant.

[0007] Therefore, developing a subcutaneous implant based on the aforementioned PSF series, clarifying its analgesic effect, dose-response relationship, and optimal variety in chronic neuropathic pain, designing a reservoir-type implant with stable structure, smooth drug release, and good biocompatibility, and solving process challenges such as drug filling, sealing, and sterilization are of great significance for filling the gap in this technical field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a subcutaneous implant containing a di(hetero)arylformate derivative of dihydrocannabidiol for the treatment of chronic neuropathic pain, which provides a single implantation and sustained analgesia for several weeks, while solving the preparation problem caused by the poor physical properties of the drug raw materials.

[0009] This invention also provides a simple and easy method for its preparation.

[0010] The present invention also provides its application in the preparation of medicaments for treating chronic neuropathic pain.

[0011] The subcutaneous implant containing a di(hetero)carbamate derivative of dihydrocannabidiol for treating chronic neuropathic pain, as described in this invention, comprises: a hollow capsule made of a polymer matrix; and a pharmaceutical composition sealed within the capsule; wherein the polymer matrix comprises a biodegradable polymer and a pore-forming agent; The pharmaceutical composition comprises an encapsulation system in which the active ingredient is a di(hetero)carbamate derivative of dihydrocannabidiol or a pharmaceutically acceptable salt thereof; and mannitol; The general structural formula of the di(hetero)arylformate derivative of dihydrocannabidiol is shown in Formula I below:

[0012] Formula I; Where R can be any of the following structures: (1); (2); (3); (4);

[0017] (5).

[0018] Specifically, the di(hetero)carbamate derivatives of dihydrocannabidiol are any one of the following compounds:

[0019] PSF1: Dihydrocannabidiol diimidazocarbamate;

[0020] PSF2: Dihydrocannabidiol-2,6-dioxapiperazine carboxylate;

[0021] PSF3: dihydrocannabidioxanone dinicotinate;

[0022] PSF4: dihydrocannabidiol difuranose ester;

[0023] PSF5: Dihydrocannabidiol dibenzoate; all subsequent uses are abbreviated by number.

[0024] The porogen is poloxamer with terminal hydroxyl groups blocked. In a biodegradable polymer matrix, it can slowly form micropores in vivo, regulating the drug release rate.

[0025] The mass ratio of the biodegradable polymer to the hydroxyl-terminated poloxamer is 95:5 to 85:15, preferably 90:10.

[0026] The biodegradable polymer is preferably polycaprolactone (PCL).

[0027] The hollow capsule has a length of 0.75cm-4.5cm and a drug loading of 3mg-12mg. The hollow capsule is a tube with an outer diameter of 3.6mm and an inner diameter of 3mm.

[0028] The pharmaceutical composition is a co-milled mixture of a di(hetero)arylformate derivative of dihydrocannabidiol (DHC) or its pharmaceutically acceptable salt as the active ingredient, and mannitol. To improve the agglomeration problem of water-insoluble PSF1-5 powder, this process introduces pharmaceutical-grade mannitol for modification. Sterile mannitol powder is mixed and co-milled with micronized PSF1-5 powder. The hydrophilic properties and steric hindrance of mannitol encapsulate hydrophobic drug particles, significantly improving powder flowability and dispersion uniformity. Simultaneously, mannitol can dissolve in trace amounts in vivo, synergistically creating pores within the capsule pores to form loose drug release channels within the PCL pores, effectively preventing drug burst release and improving long-acting drug release stability.

[0029] The powder particle size D90 of the encapsulation system of the dihydrocannabidiol di(hetero)carbamate derivative or its pharmaceutically acceptable salt is ≤10 μm.

[0030] The method for preparing a subcutaneous implant containing a dihydrocannabidiol (DHC) di(hetero)carbamate derivative for treating chronic neuropathic pain, as described in this invention, includes the following steps: a) Ring-opening polymerization of a porogen and a biodegradable polymer monomer under the action of a catalyst is carried out to obtain a biodegradable polymer containing a porogen; b) The polymer obtained in step a) is extruded to prepare a hollow tube; c) A di(hetero)arcarbamate derivative of dihydrocannabidiol or a pharmaceutically acceptable salt thereof is encapsulated in mannitol and then co-ground to obtain a pharmaceutical composition. d) The pharmaceutical composition obtained in step c) is quantitatively filled into the hollow capsule prepared in step b); e) After filling the capsule with the drug, both ends are sealed by heat fusion to obtain the final product.

[0031] The preparation method of the PSF1-5 embedding system is as follows: 1) Prepare an aqueous solution of sodium alginate; 2) Prepare the zein-drug oil phase by adding oily PSF1-5 and dispersing it evenly to obtain the zein-drug oil phase; 3) Antisolvent precipitation: The above sodium alginate aqueous solution (antisolvent) is slowly added dropwise to the zein-drug oil phase under stirring; after the addition is completed, stirring is continued for 5 min to complete the particle self-assembly.

[0032] 4) Remove solvent; 5) Post-processing and freeze-drying: Filtration, freeze-drying, and pulverization were performed to obtain the PSF1-5 / zein / sodium alginate encapsulation system.

[0033] After filling, the two ends of the capsule are precisely heat-sealed, with strict control over the sealing temperature and time: sealing heating temperature: 180℃; Single-end heat-sealing and heat preservation time: 5s; total operation time for sealing both ends does not exceed 15s. While ensuring complete sealing and leak prevention, high temperature damage to drug activity and PCL structure is avoided. Defective products are removed after visual screening to obtain the initial implant.

[0034] The porogen mentioned in step a) is poloxamer with terminal hydroxyl groups blocked, prepared by reacting poloxamer with acetic anhydride. This is to eliminate the interference of active groups on the stability of PSF1-5.

[0035] The method also includes, after step e), terminal sterilization of the implanting agent using ethylene oxide.

[0036] The finished product undergoes low-temperature (40 ℃) sterilization with ethylene oxide to avoid drug inactivation and carrier deformation caused by high temperatures. After sterilization, residual ethylene oxide is thoroughly removed. Subsequently, it is individually sealed and packaged in a sterile and dust-free environment, labeled with product information, and stored in a light-proof, airtight, and dry place at room temperature.

[0037] This method creatively combines a series of process steps, including in-situ polymerization, precision extrusion, powder modification, quantitative filling, precise hot melt sealing, and low-temperature sterilization, to ensure the sterility, stability, and quality control of the product.

[0038] In clinical use, the finished product is aseptically implanted subcutaneously into the patient's abdomen or back using a specialized implantation device. Utilizing the synergistic effects of slow PCL degradation, poloxamer-induced pore channels, and mannitol-assisted stable release, it achieves a uniform and long-lasting sustained release of PSF1-5, providing long-term, stable analgesia with a single implantation.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention adopts a reservoir-type structure of "PCL / porogen capsule + drug / mannitol core". The slow degradation of the PCL capsule and the dissolution and poration of poloxamer constitute the first layer of sustained-release barrier; the loose channels formed by the slight dissolution of mannitol in the capsule constitute the second layer of stable-release mechanism. The two work synergistically to effectively avoid the burst release of the drug and achieve a stable, near-zero-order drug release for more than 28 days.

[0040] (2) In view of the problem of powder agglomeration that may exist in the PSF1-5 encapsulation system, the present invention significantly improves the physical properties of the powder by airflow micronization and co-grinding with mannitol, so that it has good flowability and dispersibility, and meets the process requirements of automated precision filling.

[0041] (3)The animal experiment results of the present invention confirm that a single subcutaneous implantation of the implant of the present invention can produce a strong and lasting analgesic effect in a chronic neuropathic pain model, and the drug effect can last for at least 28 days. Among them, the analgesic effect of the PSF1 implant at a dose of 30 mg / kg is particularly prominent, and can basically restore the pain threshold of rats to the normal level.

[0042] (4)By preparing implants of different lengths, the present invention can conveniently achieve precise drug delivery with different drug loadings, meeting the individualized treatment needs of different patients.

[0043] (5)The present invention provides a complete preparation process from raw material treatment to terminal sterilization. In particular, the selection of hydroxyl group blocking of poloxamer, hot melt sealing conditions and low-temperature ethylene oxide sterilization ensures the activity of the drug and the integrity of the carrier, and has good industrialization prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a graph of the measured data of the thermal withdrawal latency pain threshold of PSF1-5 at 30 mg / kg on the 28th day after surgery. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] To further elaborate on the technical means and effects adopted by the present invention, the following further illustrates the technical solution of the present invention in combination with the preferred embodiments of the present invention, but the present invention is not limited to the scope of the embodiments.

[0046] The processes, conditions, reagents, experimental methods, etc. for implementing the present invention, except for the specifically mentioned content below, are all common knowledge and well-known common sense in the art, and the present invention has no particularly restricted content. For the experimental methods without specific conditions noted in each embodiment, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0047] Unless otherwise specified, the meanings of all professional terms and scientific terms used in this specification are the same as those generally understood by those skilled in the technical field to which the present invention belongs. However, in case of conflict, this specification including the definitions shall prevail.

[0048] Experimental animals: Select 200 healthy SPF-grade SD rats, half male and half female, with a body weight of 280 - 320 g, provided by the Experimental Animal Center, and the animal license number: SCXK (Guangdong) 20230035. All rats are raised in a standard animal raising environment, with a temperature of 22 - 25 °C, a humidity of 50% - 60%, 12 h light and dark alternating illumination, free access to food and water, and the experiment is carried out after 1 week of adaptive feeding. The operation of experimental animals strictly follows the "Guidelines for Ethical Review of Experimental Animals" and complies with animal ethics norms.

[0049] The preparation method of the oily substance PSF1-5 is described in the following patent examples: PSF1: CN116983263A, PSF2: CN116983265A, PSF3: CN116983267A, PSF4: CN116983266A, PSF5: CN116983264A.

[0050] Preparation of PSF1-5 embedding system: Preparation of sodium alginate aqueous phase: Accurately weigh 2.00 g of pharmaceutical grade sodium alginate powder, sprinkle it into 90 mL of deionized water in small amounts several times to prevent clumping, stir magnetically at 300 rpm for 2 h at room temperature until no gel clumps are formed, seal and place in a 4 ℃ environment for low-temperature hydration for 12~16 h overnight, take it out the next day, warm it to room temperature for 30 min, add deionized water to make up to 100 mL, prepare a 2% (w / v) sodium alginate aqueous solution, and use 0.5 M HCl solution to accurately adjust the pH to 4.0±0.05 for later use; Preparation of the drug-loaded organic phase: Separately, 90 mL of anhydrous ethanol and 10 mL of deionized water were mixed to obtain a 90% (v / v) ethanol aqueous solution. 2.00 g of pharmaceutical-grade zein was accurately weighed and added in batches. The mixture was magnetically stirred at 400 rpm at room temperature for 2 h until the protein was completely swollen and dissolved, forming a 2% (w / v) homogeneous and transparent zein organic solution. 2.67 g of PSF1-5 with a purity ≥98% was accurately weighed and added to the above protein ethanol solution. After sealing in the dark, the mixture was continuously magnetically stirred at 400 rpm at room temperature for 1 h until no free oil droplets were visible to the naked eye and the system was a uniform pale yellow dispersion. The pH of the drug-loaded organic phase was adjusted to 4.0±0.05 using 0.5 M HCl solution. Take 100 mL of the drug-loaded organic phase. Measure 300 mL of a 2% sodium alginate aqueous solution (adjusted to pH 4.0) at a 1:3 organic phase to aqueous phase volume ratio and place it in a beaker. Under high-speed shear dispersion conditions of 10,000 rpm, rapidly add the drug-loaded organic phase to the aqueous phase in a thin stream (total addition time controlled within 1-2 min). The system immediately forms a milky white suspension of nascent composite particles. After all the organic phase has been added, reduce the stirring speed to 800-1000 rpm and continue stirring at room temperature for 10-15 min to allow sufficient electrostatic complexation between zein and sodium alginate. Then, transfer the entire suspension to a rotary evaporator flask, setting the water bath temperature to 45 ℃ and the vacuum degree to -0.06 to -0.08. Ethanol was removed by rotary distillation under reduced pressure at MPa. During operation, the vacuum should be slowly increased from low vacuum to prevent protein foaming and boiling. Distillation continued until no liquid was distilled from the condenser and the material had no irritating ethanol odor. After the alcohol removal was completed, the milky white granular suspension was collected. Trehalose, accounting for 5% of the total solids, was added as a freeze-drying protectant and stirred to dissolve and disperse evenly. The mixture was then dispensed into freeze-drying trays for freeze-drying (pre-freezing temperature ≤ -40 ℃, sublimation drying stage controlled below -20 ℃, and desorption drying stage gradually heated to room temperature). Finally, PSF1-5 zein-sodium alginate composite granular powder was obtained and stored in a sealed, light-proof, and dry place.

[0051] I. Dosing Criteria In this study, the dosages administered to animals (5, 15, and 30 mg / kg) were calculated based on the actual net content of the pure active ingredient in PSF1-5, rather than the total weight of the composite particles including zein and sodium alginate. The "mg / kg" in the group designation is a standardized conversion based on the average rat body weight to the pure drug content in the implant, to ensure a dose-equivalent parallel comparison with the positive control CBD.

[0052] II. Properties of the Encapsulation System This encapsulation system (zein / sodium alginate) is a pharmaceutical sustained-release carrier material designed to achieve long-term sustained drug release (target release period of 28 days) and structural protection through a carrier framework. Encapsulating drugs with a carrier is the standard design logic for subcutaneous implantation of sustained-release formulations. If pure active pharmaceutical ingredients are implanted directly, they will be released suddenly within hours, which not only fails to achieve long-term analgesia but may also cause local toxic reactions.

[0053] III. Precise content of PSF1-5 in the encapsulation system After optimization of the feed ratio and verification using HPLC content determination methods, specifically, using the HLPC external standard method at a detection wavelength of 280 nm, the measured drug loading (n=3) was 38.2% ± 1.1%, with an inter-batch RSD of 2.9%. The actual drug loading of PSF1-5 in the lyophilized composite particles used in this invention is 38%. This drug loading level belongs to the high drug loading range in polymer-polysaccharide composite carrier systems, fully ensuring that sufficient drug is loaded within the limited capsule volume to achieve long-acting drug release.

[0054] Experimental instruments: thermal pain threshold detector, electronic balance, surgical microscope, sterile surgical instruments, subcutaneous implantation drug delivery device, etc.

[0055] The chronic sciatic nerve compression injury (CCI) model exhibits good stability and reproducibility, and its pathological characteristics closely resemble clinical peripheral nerve injury pain, making it a classic animal model for screening the efficacy of analgesics. PSF1-5 is a novel active peptide complex formulation with potential for anti-inflammatory, neuroprotective, and pain-modulating effects; however, the dose-response relationship, optimal efficacy, and long-term effects of this series of formulations for chronic neuropathic pain remain unclear. Therefore, this study constructed a rat CCI pain model to investigate the analgesic effects of different doses of subcutaneous PSF1-5 implants, compared the efficacy differences of five formulations, and clarified their mechanisms of action, aiming to develop safe and long-acting novel analgesics and provide experimental evidence for clinical intervention in chronic neuropathic pain.

[0056] Raw material pretreatment and aseptic preparation The PSF1-5 / zein / sodium alginate encapsulation system is micronized by airflow to control the powder particle size D90≤10 μm in order to improve dispersion and filling uniformity. The micronized material is then vacuum dried, irradiated and sterilized, and then aseptically sealed for later use.

[0057] Both caprolactone monomer and stannous octoate catalyst were sterile and depyrogenated.

[0058] Preparation of poloxamer with terminal hydroxyl groups blocked: Injection-grade poloxamer F68 was vacuum dried at 60 °C for 12 h to remove water, then dissolved under anhydrous pyridine nitrogen protection and heated. Anhydrous acetic anhydride was added at a molar ratio of 1:3 (poloxamer di-terminated hydroxyl groups to acetic anhydride) in an ice-water bath controlled at 0–5 °C, catalyzed with DMAP (DMAP added at 6% of the molar amount of poloxamer F68). After low-temperature dropwise addition, the temperature was raised to 25 °C and isothermal esterification was carried out for 16 h. The reaction endpoint was determined by the disappearance of the characteristic absorption peak of the hydroxyl groups as monitored by infrared spectroscopy. The system was quenched with water, extracted with dichloromethane, washed sequentially with dilute hydrochloric acid, saturated sodium bicarbonate, and purified water to remove impurities, dried with anhydrous sodium sulfate, and then the solvent was removed under reduced pressure. A waxy product was precipitated by cold anhydrous ethanol, filtered, washed with cold ethanol, vacuum dried at 45 °C for 24 h, pulverized, sieved, and sterilized by irradiation to obtain poloxamer with completely acetylated hydroxyl groups at both ends, which was used as a sustained-release pore-forming agent in hollow capsules for subcutaneous implants.

[0059] Poloxamer F68 (polyoxyethylene-polyoxypropylene block copolymer) has free hydroxyl groups at both ends. These free hydroxyl groups can undergo ester exchange with PSF1-5, accelerating drug degradation. Using acetic anhydride as an acetylation agent, the hydroxyl groups at both ends are esterified and capped under the catalysis of an organic base to generate poloxamer with double-terminated acetyl groups, retaining the hydrophilic pore-forming ability of poloxamer and eliminating interference from active hydroxyl groups.

[0060] General reaction formula: HO-(PEO-PPO-PEO)-OH+2(CH3CO)2O→CH3COO-(PEO-PPO-PEO)-OCOCH3+2CH3COOH.

[0061] Example The method for preparing the subcutaneous implant containing a dihydrocannabidiol di(hetero)carbamate derivative for treating chronic neuropathic pain comprises the following steps: a) The hydroxyl-blocked poloxamer F68 was mixed with caprolactone monomer at a mass ratio of 10:90, and 400 ppm stannous octoate was added as a catalyst. After the system was thoroughly deoxygenated by nitrogen, it was polymerized at 140℃ under nitrogen protection for 24 h to allow the monomer to fully polymerize and the pore-forming agent to be uniformly dispersed in the PCL matrix.

[0062] b) The polymer product is melt-extruded, water-cooled and granulated to obtain uniform modified PCL raw material, which is then extruded through a precision mold to prepare hollow PCL pipes with an outer diameter of 3.6 mm and an inner diameter of 3 mm. The pipes are uniformly cut into three specifications: 1.0 cm, 2.5 cm, and 4.5 cm. Qualified tubes with uniform size and no cracks or damage are selected and aseptically dried for later use.

[0063] c) Sterile mannitol powder and micronized PSF1-5 powder were mixed and ground together at a mass ratio of 1:2. The hydrophilic properties and steric hindrance of mannitol were used to encapsulate the hydrophobic drug particles, which significantly improved the flowability and dispersion uniformity of the powder, thus obtaining a drug composition.

[0064] d) In a Class A aseptic workbench, the uniform PSF1-5 compound powder modified with mannitol is quantitatively filled into PCL hollow capsules using a precision powder filling device. The filling is performed at a low, uniform speed to ensure a dense and uniform filling without any loose lumps. Different capsule lengths correspond to fixed drug loading capacities: approximately 6 mg for 1.0 cm, approximately 18 mg for 2.5 cm, and approximately 36 mg for 4.5 cm, catering to different long-acting dosing needs.

[0065] Based on an average SD rat weight of 300 g, the pure PSF1-5 content in each implantation unit for the low, medium, and high dose groups was designed to be 1.5 mg / vial, 4.5 mg / vial, and 9.0 mg / vial, respectively, corresponding to 5, 15, and 30 mg / kg. The corresponding capsule lengths for the three dose groups were 1.0, 2.5, and 4.5 cm, respectively, and the mixed powder filling volumes were 6.0, 18.0, and 36.0 mg / vial, respectively.

[0066] Based on the PSF1-5 loading (38%) in the encapsulation system and the 1:2 mass ratio of mannitol to the encapsulation system, the mass fraction of PSF1-5 in the mixed powder was calculated to be 25.3%. Therefore, the required mixed powder filling amounts for each dosage group were determined to be 6.0 mg, 18.0 mg, and 36.0 mg, respectively. Combining the inner diameter of the hollow capsule (3 mm) and the filling density (approximately 6 mg / cm³), the corresponding capsule lengths were determined to be 1.0 cm, 2.5 cm, and 4.5 cm, respectively.

[0067] Calculation method: Mannitol:PSF encapsulation system = 1:2 The drug loading of PSF1-5 in the encapsulation system is approximately 38%. Therefore, the final mass fraction of PSF1-5 in the mixed powder is: 38% × (2 / 3) = 25.3%. Low-dose group (5 mg / kg): Each implantation agent requires 300 g of pure drug × 5 mg / kg = 1.5 mg. Required mixed powder = 1.5 mg ÷ 25.3% ≈ 6 mg Corresponding cyst length = 1.0 cm Medium dose group (15 mg / kg): Each implantation agent requires 300 g of pure drug × 15 mg / kg = 4.5 mg. Required mixed powder = 4.5 mg ÷ 25.3% ≈ 18 mg Corresponding cyst length = 2.5 cm High-dose group (30 mg / kg): Each implantation agent requires 300 g of pure drug × 30 mg / kg = 9.0 mg. Required mixed powder = 9.0 mg ÷ 25.3% ≈ 36 mg The corresponding cyst length is 4.5 cm.

[0068] The CBD-positive control group was administered the drug via intraperitoneal injection daily at doses of 5, 15, and 30 mg / kg, calculated based on the actual body weight of the rats.

[0069] e) After filling, perform precise heat fusion sealing on both ends of the capsule tube, strictly controlling the sealing temperature and time (sealing heating temperature: 180℃; heat fusion sealing time for one end: 5s; total operation time for sealing both ends not exceeding 15s). While ensuring complete sealing and preventing leakage, avoid high temperature damage to drug activity and PCL structure. After visual screening, reject unqualified products to obtain the initial implant.

[0070] f) The finished product is sterilized with ethylene oxide at a low temperature (40°C) to avoid drug inactivation and carrier deformation caused by high temperature. After sterilization, residual ethylene oxide is thoroughly removed. Subsequently, it is individually sealed and packaged in a sterile and dust-free environment, labeled with product information, and stored in a light-proof, airtight, and dry place at room temperature.

[0071] I. Animal Model Construction and Grouping A chronic neuropathic pain model was established using the classic CCI model construction method: Rats were anesthetized with sodium pentobarbital via intraperitoneal injection, fixed in a prone position, and the right sciatic nerve was exposed. Four loose ligations were made along the mid-segment of the sciatic nerve using 4-0 silk sutures, spaced 1 mm apart. After ligation, the epineurium was slightly compressed, and blood supply was not completely blocked. The muscles and skin were sutured layer by layer, and routine disinfection and anti-infection measures were performed postoperatively. In the sham-operated group, only the sciatic nerve was exposed; no ligation was performed, but the rest of the surgical procedure was the same.

[0072] Rats that successfully developed the model were randomly divided into 18 intervention groups, with sham-operated group and model control group, 10 rats in each group. The groups were: sham-operated group, model control group, PSF1 (5 mg / kg, 15 mg / kg, 30 mg / kg), PSF2 (5 mg / kg, 15 mg / kg, 30 mg / kg), PSF3 (5 mg / kg, 15 mg / kg, 30 mg / kg), PSF4 (5 mg / kg, 15 mg / kg, 30 mg / kg), PSF5 (5 mg / kg, 15 mg / kg, 30 mg / kg), and CBD positive control group (5 mg / kg, 15 mg / kg, 30 mg / kg). Rats in each intervention group received the corresponding dose of PSF1-5 series subcutaneous implants immediately after surgery. The sham-operated group and model control group did not receive any drug intervention and were fed normally.

[0073] CBD reference standard: purity ≥99%, purchased externally. Administration method: Preparation method of traditional injection (CBD intraperitoneal injection solution): To establish a positive control to compare the long-acting sustained-release effect with the implant, this study also set up a traditional CBD injection intervention group, which was administered daily via intraperitoneal injection (ip) to simulate the efficacy characteristics of the traditional dosage form.

[0074] Preparation of CBD administration solution: Take CBD reference standard with a purity ≥99% and prepare three concentrations of drug solution (low, medium and high) using physiological saline containing 5% (v / v) DMSO and 5% (v / v) Tween-80 as solvent.

[0075] The specific preparation method is as follows: Accurately weigh the required amount of CBD reference standard, first dissolve it in DMSO to prepare a stock solution, then add Tween-80 and physiological saline sequentially to make the final solution contain 5% (v / v) DMSO and 5% (v / v) Tween-80. The dosage volume is calculated at 10 mL / kg, and the concentrations for each dose group are designed as follows: low dose group 0.5 mg / mL (corresponding to 5 mg / kg), medium dose group 1.5 mg / mL (corresponding to 15 mg / kg), and high dose group 3.0 mg / mL (corresponding to 30 mg / kg). After preparation, filter through a 0.22 μm microporous membrane for sterilization and use immediately. The model control group rats are intraperitoneally injected daily with an equal volume of blank solvent (physiological saline containing 5% DMSO and 5% Tween-80) as a solvent control.

[0076] Dosage regimen: Rats in each group were administered the drug via intraperitoneal injection once daily at 9:00 AM after surgery for 28 consecutive days. The dosage was adjusted in real time based on the weekly weight of the rats.

[0077] II. Detection Indicators and Methods The pain threshold in rats was assessed using the thermal paw retraction latency method, performed at 7, 14, 21, and 28 days post-surgery. Before testing, rats were placed on the thermal pain threshold detector platform for 30 minutes to acclimatize. The infrared heat source of the instrument was adjusted and focused on the sole of the rat's right hind paw. The time from irradiation to paw retraction was recorded as the thermal paw retraction latency. To avoid tissue burns, the maximum testing time was set to 30 seconds. Each group of rats was tested three times, with a 5-minute interval between each test. The average value was taken as the final result; a higher value indicated a higher pain threshold and less pain.

[0078] III. Experimental Results Experimental data were analyzed using SPSS software for one-way ANOVA. Pairwise comparisons between groups were performed using the LSD-t test, and P < 0.05 was considered statistically significant.

[0079] Changes in the latency period of heat-induced paw retraction in rats at different time points in each group The results of the thermal paw retraction latency at different time points after surgery in each group of rats are shown in Table 1. In the sham-operated group, the thermal paw retraction latency remained stable at 18.2±2.0 ~ 18.5±2.1 s at each time point, without significant fluctuations, indicating normal neuropathic pain. In the model control group, the thermal paw retraction latency was significantly lower than that in the sham-operated group at each time point (P<0.05), with values ​​stable at 6.8±1.5 ~ 7.3±1.5 s, suggesting successful establishment of the CCI model and the presence of stable chronic neuropathic hyperalgesia in the rats.

[0080] The latency period of heat-induced paw shrinkage in rats in all PSF1-5 formulation intervention groups and the CBD-positive control group was significantly longer than that in the model control group, showing a clear dose-dependent effect: for the same formulation, the 30 mg / kg dose group had the best analgesic effect, followed by 15 mg / kg, and the 5 mg / kg dose had the weakest effect. Looking at the longitudinal time dimension, the pain threshold in rats in each intervention group reached its peak at 14 days post-surgery, and slightly decreased at 21 and 28 days, but remained significantly higher than that in the model control group, confirming that the PSF subcutaneous implant has a long-lasting analgesic effect, and that the CBD multiple-dose regimen can also maintain basic analgesia within the 28-day observation period.

[0081] Table 1. Results of heat-induced paw retraction latency in rats at different time points in each group. (Mean x ± standard deviation s, sample size n = 10, dosages are based on pure PSF and pure CBD active ingredients)

[0082] The data on the pain threshold during the latency period of heat-induced foot contraction 28 days postoperatively, measured with 30 mg / kg PSF1-5 and 30 mg / kg CBD, are shown in the figure below. Figure 1 As shown in the figure. Combining the trend charts of the thermal shrinkage latency of the five PSF preparations and the CBD positive control group at various time points after surgery at a dose of 30 mg / kg with quantitative data, it can be seen that the analgesic effects of each PSF preparation and the CBD positive control group showed obvious dose dependence. The overall effect was that the high dose was the most effective, followed by the medium dose, and the low dose was the weakest. Moreover, the efficacy showed a trend of first increasing and then slightly decreasing with the postoperative time, reaching the peak analgesia on day 14 after surgery, and maintaining a stable analgesic effect until day 28 after surgery, which has good long-acting sustained-release characteristics. Under the same dose conditions, there were significant differences in the analgesic effects of the five preparations. The overall analgesic effect was ranked as PSF1>PSF5>PSF2≈PSF4≈PSF3≈CBD. Among them, the 30 mg / kg PSF1 preparation had the most outstanding analgesic effect, and the pain threshold of rats was closest to that of the normal sham-operated group. It also had the best long-term stability. The analgesic effects of the three preparations PSF2, PSF3, and PSF4 were similar to those of CBD at the same dose, but relatively weaker.

[0083] Chronic neuropathic pain is mainly caused by peripheral nerve injury leading to neuroinflammation and sensitization of pain pathways. Conventional oral and injectable analgesics suffer from problems such as short duration of action, large fluctuations in efficacy, the need for repeated administration, and significant side effects with long-term use, making it difficult to achieve long-term stable analgesia. In this experiment, CBD required continuous and repeated administration to maintain analgesia for 28 days, resulting in high dosing frequency and poor clinical compliance. Compared with traditional administration methods, subcutaneous implanted sustained-release formulations can achieve local continuous drug release, maintain stable in vivo drug concentrations, and act on pain modulation pathways for a long time, making them more suitable for the long-term treatment needs of chronic neuropathic pain. This study used a stable and reproducible CCI rat model to evaluate the efficacy of the drug. The results confirmed that all PSF1-5 subcutaneous implants had significant anti-neuropathic pain activity, exhibiting good dose-dependent analgesic effects within the dose range of 5-30 mg / kg. The higher the dose, the stronger the analgesic effect. The efficacy of each formulation reached its peak 14 days after surgery and maintained effective analgesia until 28 days after surgery, fully demonstrating the application advantages of long-acting sustained release of subcutaneous implants. Compared with CBD, which requires frequent administration, it has significant advantages in use.

[0084] There are significant differences in the analgesic effects between the five PSF preparations and the positive control CBD. The overall analgesic effect is the best with PSF1, followed by PSF5. The analgesic effects of PSF2, PSF3, and PSF4 are relatively mild and similar to each other, and are comparable to the analgesic activity of CBD at the same dose. This difference in drug efficacy may be related to the different molecular structures, targeting abilities, and in vivo metabolic characteristics of each preparation. This study innovatively verified the intervention effect of the PSF series of polypeptide composite preparations on chronic neuropathic pain, completed a parallel comparison of drug efficacy with CBD as the positive control, screened out the optimal acting preparation and dosing regimen, and provided experimental support for the development of new long-acting analgesic preparations.

[0085] The subcutaneous implants of PSF1, PSF2, PSF3, PSF4, and PSF5 can effectively relieve the chronic neuropathic pain caused by chronic constriction injury of the sciatic nerve in rats. The analgesic effect has a significant dose-dependence, and the intervention effect is the best at the high dose (30 mg / kg). Among the five preparations, PSF1 has the best analgesic effect and long-acting property, significantly superior to CBD at the same dose; PSF5 is the second, and the analgesic effects of PSF2, PSF3, and PSF4 are relatively weak, comparable to the analgesic activity of CBD at the same dose. The subcutaneous implants of PSF1-5 have the advantages of long-acting, safe, and stable analgesia, and can be used as new candidate intervention preparations for chronic neuropathic pain. Among them, the high-dose PSF1 preparation has better analgesic activity than the prototype CBD and has the highest clinical transformation and application value.

[0086] Experimental example: Evaluation of non-addiction of the active ingredients PSF1-5 of the present invention To evaluate the drug addiction of the active ingredients PSF1-5 of the present invention, the present invention conducted a conditioned place preference (CPP) experiment to evaluate its psychological dependence, and evaluated its physical dependence after withdrawal through an open field test (OFT) and an elevated plus maze test (EPM).

[0087] 1. Experimental materials and methods 1.1 Experimental animals SPF-grade male Kunming mice, 6-8 weeks old, weighing 25-30 g, were purchased from Beijing Speywood Biotechnology Co., Ltd. [Production License No.: SCXK (Beijing) 2024-0001]. The animals were housed in an SPF-grade animal room at a temperature of 22-25 °C, with a 12 h light / 12 h dark cycle, and free access to food and water. All animal experiments followed the relevant regulations of the Experimental Animal Ethics Committee.

[0088] 1.2 Drugs and reagents Each component of PSF1-5 (purity ≥ 98%, provided by the Institute of Agro-Products Processing, Chinese Academy of Agricultural Sciences); morphine hydrochloride injection (commercial specification, positive control drug); normal saline; DMSO (dimethyl sulfoxide, pharmaceutical grade); 75% alcohol.

[0089] Before administration, each of the PSF1, PSF2, PSF3, PSF4 and PSF5 components was dissolved in DMSO to prepare a stock solution. Before use, each solution was diluted with physiological saline to the required concentration (final DMSO concentration ≤ 5%) and administered via intraperitoneal injection.

[0090] 1.3 Main Instruments Conditional location preference box, open field test box, elevated cross maze and VisuTrack animal behavior video analysis software (Shanghai Xinruan Information Technology Co., Ltd.).

[0091] 1.4 Experimental grouping and dosing regimen Mice were randomly divided into the following groups, with 10 mice in each group: First batch: blank control group (physiological saline), solvent control group (5% DMSO), positive control group (morphine 3mg / kg), PSF1 group (10mg / kg), PSF5 group (10mg / kg).

[0092] The second batch consisted of: blank control group (physiological saline), solvent control group (5% DMSO), positive control group (morphine 3 mg / kg), PSF2 group (20 mg / kg), PSF3 group (20 mg / kg), and PSF4 group (20 mg / kg).

[0093] All medications were administered via intraperitoneal injection.

[0094] 2. Experimental Procedure 2.1 Conditional Place Preference (CPP) Experiment The experiment consisted of three phases: pre-test (3 days), training (12 days, drug-environment pairing), and post-test (1 day). The changes in the time mice spent in the drug-accompanied box before and after training (CPP score) were compared among the groups.

[0095] The training phase lasted for 12 days (days 1 to 12). A partition was inserted, and training was alternated between medication-accompanied and non-medication-accompanied boxes, 6 times each. On medication-accompanied box training days (days 1, 3, 5, 7, 9, and 11): Mice in each drug-treated group were intraperitoneally injected with the corresponding drug 30 minutes before training (PSF1-5 groups and the solvent control group were injected with the corresponding drug or 5% DMSO saline solution; the positive control group was injected with morphine; and the blank control group was injected with saline solution). After 30 minutes, the mice were placed in the medication-accompanied box and left for 35 minutes before being removed. On non-medication-accompanied box training days (days 2, 4, 6, 8, 10, and 12): Mice in all groups were not given any medication and were directly placed in the non-medication-accompanied box, left for 35 minutes, and then removed.

[0096] 2.2 Withdrawal Behavioral Experiments On days 7 and 8 after CPP training, the open field test (OFT) and elevated cross maze test (EPM) were conducted to evaluate voluntary activities and anxiety-like behaviors after drug withdrawal.

[0097] OFT metrics: total distance traveled, number of times entering the central zone, time spent in the central zone, average speed, and number of supporting stands.

[0098] EPM metrics: number of times the arm is opened and the dwell time in the arm.

[0099] 2.3 Statistical Analysis Experimental data are expressed as mean ± standard deviation (Mean ± SD). One-way ANOVA was used for comparisons among multiple groups; LSD method was used for pairwise comparisons when variances were homogeneous, and Dunnett's T3 method was used when variances were unequal. Paired t-tests were used to compare pre-test and post-test CPP scores. A p-value < 0.05 was considered statistically significant. GraphPad Prism 9.0 was used as the statistical software.

[0100] 3. Experimental Results 3.1 Results of the CPP experiment (evaluation of psychological dependence) The results are shown in Table 2. The positive control group (morphine) mice showed a significantly higher post-test CPP score than the pre-test (P<0.001), indicating a clear conditional position preference. However, the post-test CPP scores of all PSF1-5 groups showed no significant difference compared to the pre-test (P>0.05), and were comparable to the blank control group and the solvent control group. These results indicate that none of the components of PSF1-5 induces psychological dependence.

[0101] Table 2: Comparison of CPP scores before and after the test in each group of mice (s, Mean±SD, n=10)

[0102] 3.2 Results of the withdrawal behavior experiment (evaluation of physical dependence) Open field test (OFT) results (Table 3): The total range of motion and central area activity of mice in the morphine withdrawal group were significantly reduced, while the number of times they supported themselves on their feet was significantly increased (P<0.05), exhibiting typical anxiety-like behavior. There were no significant differences in any behavioral indicators of mice in the PSF1-5 groups compared with the blank control group (P>0.05).

[0103] Table 3: Comparison of Open Field Test (OFT) Results among Different Groups of Mice (Mean±SD, n=10)

[0104] The results of the elevated cross maze (EPM) test (Table 4) showed that the morphine withdrawal group had significantly less time spent in the open arm and fewer entries than the blank control group (P<0.05). There were no significant differences between the PSF1-5 groups and the blank control group (P>0.05).

[0105] Table 4: Comparison of Elevated Cross Maze (EPM) results among different groups of mice (Mean±SD, n=10)

[0106] In summary, the active ingredients PSF1-5 involved in this invention do not induce psychological dependence in the conditional position preference test, do not cause anxiety-like behavior after withdrawal, and do not induce physical dependence. These results strongly demonstrate that the PSF1-5 series of compounds do not have addictive potential and possess the good safety profile required for use as a chronic pain treatment drug.

Claims

1. A subcutaneous implant containing a dihydrocannabidiol (DHC) di(hetero)carbamate derivative for the treatment of chronic neuropathic pain, characterized in that, It comprises: a hollow capsule made of a polymer matrix; and a pharmaceutical composition sealed within the capsule; wherein the polymer matrix comprises a biodegradable polymer and a pore-forming agent; The pharmaceutical composition comprises an encapsulation system in which the active ingredient is a di(hetero)carbamate derivative of dihydrocannabidiol or a pharmaceutically acceptable salt thereof; and mannitol; The general structural formula of the di(hetero)arylformate derivative of dihydrocannabidiol is shown in Formula I below: Formula I; Where R can be any of the following structures: （1）； （2）； （3）； （4）； （5）。 2. Subcutaneous implant for the treatment of chronic neuropathic pain comprising a di(hetero)arylate derivative of dihydrocannabidiol according to claim 1, characterized in that, The porogen is poloxamer with its terminal hydroxyl groups blocked.

3. Subcutaneous implant for the treatment of chronic neuropathic pain comprising a di(hetero)arylate derivative of dihydrocannabidiol according to claim 2, characterized in that, The biodegradable polymer and the hydroxyl-terminated poloxamer are in a mass ratio of 95:5 to 85:

15.

4. Subcutaneous implant for the treatment of chronic neuropathic pain comprising a di(hetero)arylate derivative of dihydrocannabidiol according to claim 1, characterized by the fact that, The hollow capsule has a length of 0.75cm-4.5cm and a drug loading of 3mg-12mg.

5. The subcutaneous implant containing a dihydrocannabidiol di(hetero)carbamate derivative for treating chronic neuropathic pain according to claim 1, characterized in that, The pharmaceutical composition is a co-milled mixture of a dihydrocannabidiol di(hetero)carbamate derivative or a pharmaceutically acceptable salt thereof encapsulation system and mannitol.

6. Subcutaneous implant for the treatment of chronic neuropathic pain comprising a di(hetero)arylate derivative of dihydrocannabidiol according to claim 1, characterized by the fact that, The powder particle size D90 of the encapsulation system of the dihydrocannabidiol di(hetero)carbamate derivative or its pharmaceutically acceptable salt is ≤10 μm.

7. A method for the preparation of a subcutaneous implant containing a di(hetero)arylate derivative of dihydrocannabidiol for the treatment of chronic neuropathic pain according to any of claims 1 to 6, characterized in that, Includes the following steps: a) Ring-opening polymerization of a porogen and a biodegradable polymer monomer under the action of a catalyst is carried out to obtain a biodegradable polymer containing a porogen; b) The polymer obtained in step a) is extruded to prepare a hollow capsule; c) A di(hetero)aryl ester derivative of dihydrocannabidiol or a pharmaceutically acceptable salt thereof is encapsulated in a system with mannitol and then co-ground to obtain a pharmaceutical composition; d) The pharmaceutical composition obtained in step c) is quantitatively filled into the hollow capsule prepared in step b); e) After filling the capsule with the drug, both ends are sealed by heat fusion to obtain the final product.

8. The method of claim 7, wherein the subdermal implant is prepared by, The porogen mentioned in step a) is poloxamer with its terminal hydroxyl groups blocked, prepared by reacting poloxamer with acetic anhydride.

9. The method of claim 7 or 8, wherein the subdermal implant is prepared by, The method also includes, after step e), terminal sterilization of the implanting agent using ethylene oxide.

10. Use of a subcutaneous implant according to any one of claims 1 to 6, characterized in that, Used to prepare drugs for treating chronic neuropathic pain.

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