Vascular embolization agents and methods for their production and use

Abstract

The invention relates to agents and systems for vascular embolization in order to stop bleeding and reduce organ filling with blood and may be applied in cardiovascular and X-ray endovascular surgery. The invention further relates to method of preparation and uses thereof.

Description

[0001] VASCULAR EMBOLIZATION AGENTS AND METHODS FOR THEIR PRODUCTION

[0002] AND USE

[0003] FIELD OF INVENTION

[0004] The present invention relates to agents for vascular embolization and methods for their production and use in order to stop bleeding and reduce organ filling with blood, in particular for use in endovascular surgery, interventional radiology and oncology for target medicinal drug delivery (cytostatic, antimicrobial drugs, etc).

[0005] BACKGROUND ART

[0006] Bleeding disorders are a group of conditions in which there is a problem with the body's blood clotting process. These disorders can lead to heavy and prolonged bleeding after an injury or surgery. Bleeding can also begin on its own and may be difficult to stop.

[0007] Endovascular embolization is widely used in surgery and oncology to turn off the blood supply to the tumor, which makes it possible to reduce its size, slow down its development, facilitate surgical interventions and reduce blood loss during surgery to remove it (Gantsev et al., Kreativnaya khirurgiya i onkologiya. 2020;10(3):205-211; https: / / dot. org / 10.24060 / 2076- 3093-10-3-205-211; Karelin et al, 2008, Onkourologiya, (1): 18-20. (In Russ.; Zemlyansky et al., 2020, Andrologiya i genital'naya khirurgiya, 21(l):65-69 https: / / doi. org / 10.17650 / 2070- 9781-2020-21-1-65-69; Nersesyan et al., 2018, Opukholi golovy i shei., 8(l):28-37, https: / / doi. org / 10.17650 / 2222-1468-2018-8-1-28-37, Nartailakov et al., 2022, Khirurgicheskaya praktika, ( 1 ):33-37https: / / doi. org / 10.38181 / 2223-2427-2022-1-33-37).

[0008] Embolization is commonly used to treat acute hemorrhage (Loffroy et al, 2009, Curr. Vase. Pharmacol, 7, 250-263) and hepatocellular carcinoma (HCC) since hepatic tumors are mostly supplied by the arterial blood supply (Yamada et al., 1995, World J. Surg., 19, 795- 800, 10.1007 / BF00299773).

[0009] One of the main purposes of embolic agents is their use for stopping blood flow to a specific blood vessel in the treatment or prevention of a bleeding by intraluminal occlusion of arteries damaged by injury or other pathological process.

[0010] In oncological practice, embolization can be used to block the flow of blood to a tumour so the cancer cells die.

[0011] When the material used to block the blood supply also delivers chemotherapy drugs to the tumour, it is called chemoembolization. Transarterial chemoembolization (TACE) is a specific type of chemoembolization that blocks the hepatic artery to treat liver cancer (Wang et al, 2023, Theranostics, 13, 7, 2114-2139). In particular, the use of embolic agents for the treatment of parenchymatous organ tumors is known (Tam et al., 2011, European Journal of Pharmaceutical Sciences, 44, 1-2, 1-10).

[0012] Arterial intraorgan occlusion causes tumor ischemic necrosis, limits the possibility of viable tumor cells, as well as their decay products, entering the systemic circulation during tumor resection, reduces the likelihood of metastasis and lowers the body's intoxication. Often, such a treatment method is used as a palliative treatment since it is the only possible way to prolong life and improve condition of patients with locally advanced and generalized forms of tumor diseases.

[0013] The effectiveness of embolization directly depends on the choice of embolic material, which must meet certain requirements: be non-toxic, hydrophilic, and resistant to the external biological environment (Korsmeyer et al, 1983, Int J Pharm., 15(1):25- -35. https: / / doi. org / 10.1016 / 0378-5173(83)90064-9). The efficiency of arterial intraorgan occlusion therefore greatly depends on the quality of embolic agents used.

[0014] A known agent for vascular embolization is made of a material containing silicone rubber — low molecular weight poly dimethyl siloxane, tetraethoxysilane, tin octoate and fine tantalum powder (SU 1106509 A, 07.08.84). However, its drawback is its high viscosity which prevents its administration through thin catheters into small-vessels, for example, for treatment of profuse nose bleeds or hemoptysis.

[0015] Another known agent used for vascular embolization is made of a polymeric material obtained from a solution containing oxane, carbonyl iron, chloroplatinic acid, oligohydridesiloxane and oligodimethyl siloxane, (RU 2073529, 20.02.1997) and is prepared directly before it is introduced into the vascular bed of the patient’s tumorous organ. When mixing the solution, spatially cross-linked polymer structures are formed that firmly retain carbonyl iron particles inside them. The presence of oligodimethylsiloxane, serving as a plasticizer, reduces the viscosity that dimethylmethyl polyvinylsiloxane had in the finished composition with preserving it in air for 20-25 minutes. Then, the viscosity of the composition rapidly increases with the formation of an elastic sponge-like polymer within 2 hours and occluding the affected organ from the systemic blood flow. However, due to the fact this agent is prepared immediately before surgery, any deviation from the stated parameters and manufacturing methods can result in unpredictable changes in obtained properties of the resulting agent. This constitutes a significant drawback for the use of this agent. Liquid embolic agents have attracted attention owing to their properties of deep vascular penetration and full occlusion of vasculature independent of thrombus formation, which relies on the patient's coagulation system Jiang et al., 2022, ChemPhysMater, 1(1), 39-50).

[0016] A particular vast class of biomedical polymers that are well suited for the creation of embolizing carriers are weakly cross-linked (porous) hydrogels based on the polymer 2- Hydroxy ethyl Methacrylate (polyHEMA). Embolic materials (EM) based on poly-HEMA are inert, hydrophilic, elastic and biostable (Koverzanova, 2012, Diagnosticheskaya i interventsionnaya radiologiya, 6(l):97-104). Pure liquid 2-PHEMA was used for arteriovenous malformations (AVMs) embolization made radiopaque with tungsten and even if needed to be improved has been proven to be feasible (Klisch et al., 2002, AJNRAm J Neuroradiol 23:422 429). Poly(NIPAAm-co-HEMA-acrylate) / poly(NIPAAm-co-cysteamine) blends, simultaneous physical and chemical gelling polymer system and have been described suitable for use as a liquid-to-solid embolic agent with use in vivo endovascular embolization for intracranial aneurysm (Karadeli, et al., 2023, Macromol. Biosci.2023, 230043).

[0017] However, there remain challenges in the development of embolic agents, such as the wide variety of clinical scenarios and desired outcomes. In oncology, only blocking the blood supply is less effective for tumor treatment, and embolic materials should have the ability to load chemotherapeutic drugs and release them at an appropriate rate (Jiang et al, 2022, supra).

[0018] However, the selective and targeted drug delivery is a major challenge for effective therapy of many diseases (Hoffman, 2008, J Control Release. 2008; 132(3): 153-163. https: / / doi.Org / 10.1016 / j.jconrel.2008.08.012; Luo, 2002, Curr Cancer Drug Targets, 2(3):209- 226. https: / / doi.org / 10.2174 / 1568009023333836).

[0019] An ideal drug delivery system should be chemically inert, not interact with drugs, easy to use, mechanically strong, and capable of delivering the required dose of drugs to the target organ over a certain period of time (Kharrison, 2011, Polymers in biology and medicine, subshare. Moscow: Nauchnyy mir, s.47-72). Modem polymer porous hydrogels meet these requirements, which can be used for drug delivery and such targeted administration of a chemotherapy drug makes it possible to achieve the required local concentration of the drug and exposure - a longer time of its action, which increases the effectiveness of treatment and minimizes undesirable side effects (Babaeva etal., 2017, Novosti. Mneniya. Obuchenie. 2017; 1(15): 16-21). However, the saturation of hydrogels with active principles varies significantly and depends on the mechanism involved in the loading of the hydrogels, which is determined, on one hand, by the physical characteristics (porosity) of the hydrogel, and on the other hand, by the presence in the active principle of active chemical groups allowing the chemical binding of active principle to the hydrogel. In the latter case, chemical bonding hinders the release of the drug into the tissue of the target organ, (de Baere et al., 2016, J Vase Interv Radiol., 27(9): 1425-1431').

[0020] To date, there are no guidelines how to select an embolic agent and the selection of the embolic materials depends on the encountered anatomy, tortuosity and caliber of the arteries, the technique chosen (i.e. sandwich technique, proximal embolization) and operator’s confidence with the materials available since the known embolic agents have strengths but also weaknesses (lerardi et al., 2022, supra).

[0021] Therefore, there is a need to develop new agents and methods for vascular embolization with the formation of complete, reliable vascular occlusion that are the source of bleeding or supply blood to the tumor, resulting in its total necrosis and excluding the possibility of single viable tumor cells entering the systemic blood flow that would reduce the likelihood of tumor dissemination and subsequent metastasis.

[0022] SUMMARY OF THE INVENTION

[0023] A general object of this invention is to provide new agents and methods for efficient vascular embolization.

[0024] It is advantageous to provide a vascular embolization agent due to its increased elasticity that contributes to restoring original shape after possible deformations to which the agent is exposed when delivered through a catheter to embolization site.

[0025] It is also advantageous to provide a vascular embolization agent able to swell, thereby ensuring reliable obstruction of the embolized vessel.

[0026] It is also advantageous to provide a vascular embolization agent able to sorb blood components on the surface, increasing thrombocyte aggregation and facilitating the formation of thrombotic masses at the embolization site.

[0027] It is also advantageous to provide a vascular embolization agent able to hold a blood clot reinforced with a polymer porous mass, and over a long period of time it grows with connective tissue, providing a persistent occlusion effect that excludes recanalization of the vascular bed.

[0028] It is also advantageous to provide a vascular embolization agent suitable for both conventional embolization and targeted delivery of active water-soluble agents to tissue

[0029] An object of this invention is to provide a vascular embolization agent with advantageous selective embolization properties to deliver these agents to tissues and uses thereof. It is also advantageous to provide a method of preparation of vascular emboli that can be easily loaded with active agents through a process of physical absorption.

[0030] Another object of this invention is to provide a method of preparation of a vascular embolization system useful for conventional embolization and for chemoembolization.

[0031] It is also advantageous to provide a method of embolization which is suitable for vessels with a wide bed.

[0032] Another object of this invention is to provide method for embolization, said method comprising the use of a vascular emboli of the invention.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Fig- 1 illustrates the of macroporous structures formed during the polymeriation of HEMA as shown by electron microscopy as described under Example 1.

[0035] Fig- 2 shows embolization particles made of PolyHydroxyEthylMethAcrylate (pHEMA) as described in Example 1, 4. A. Spherical particles (Ex. l); B. Cylindrical particles (Ex.4).

[0036] Fig- 3 is an electrons microscopy image of an embolization system material (cylindrical emboli) prepared according to Example.

[0037] Fig. 4 represents the weight loss of spherical emboli at 50°C according to the invention versus time of drying as described in Example 6.

[0038] Fig. 5 shows eletron microscopy photographs of spherical emboli before drying (left) and after drying at 50°C (right) as described in Example 6.

[0039] Fig. 6. Shows the identification of doxorubicin release in stationary and non-stationary conditions; the initial content of DR in EM is 0.5 mg (red and black curves) as described in Example 7. 1 - stationary release conditions, 2 - non-stationary release conditions; the initial content of DR in EM is 0.25 mg (green and blue curves): 3 - stationary release conditions, 4 - non-stationary release conditions. Note: DR - doxorubicin.

[0040] Fig. 7 illustrates the status of a patient presenting arteriovenous dysplasia of the left half-face as a candidate for endovascular occlusion. A: Patient A., age 17 arteriovenous dysplasia; B-D: Angiograms of patient A prior to endovascular occlusion. B: selective angiogram of the right external carotid artery; the dilated and tortuous frontal branch of the facial artery is observed; C: arteriogram of the left carotid system; the external carotid artery is not contrasted - previously tied; filling of angiomatous tissue in the hard palate area occurs from the internal carotid artery system through collateral arteries; D: selective arteriogram of the thyrocervical trunk on the left; a markedly dilated and tortuous ascending neck artery is observed - the main source of blood supply to the angiomatous tissue.

[0041] Fig- 8 illustrates the status of the patient of fig.7 after a treatment by endovascular occlusion according to the invention. A-B: Angiograms of patient A after endovascular occlusion; A: selective angiogram of the right external carotid artery; focal angiomatous tissue is not filled with a radiopaque substance due to lack of blood supply after embolization; B: selective arteriogram of the thyrocervical trunk on the left; the proximal segment of the neck ascending artery is observed, further, the arterial lumen and the vascular bed are occluded; C: Patient A., age 17 following three stages of X-ray endovascular occlusion with hydrogel microspheres and sclerotherapy as described in Example 1-3.

[0042] Fig. 9 presents selective angiograms of occipital arteries of the patient R prior to embolization; A: right occipital artery; B: left occipital artery.

[0043] Fig. 10 presents selective angiograms of occipital arteries of the patient R following embolization with cylindrical-shaped hydrogel emboli as described in Example 8; A: right occipital artery; B: left occipital artery.

[0044] Fig- 11 illustrates alternate embolization of the uterine arteries upon detection of utero-ovarian arterio-arterial anastomoses; A: preliminary arteriogram of the right uterine artery (outlined arrow) — retrograde injection with a radiopaque substance of the ipsilateral ovarian artery (white arrow) through utero-ovarian anastomoses is observed; B: preliminary arteriogram of the left uterine artery (outlined arrow) - retrograde injection with a radiopaque substance of the left ovarian artery (white arrow) through the utero-ovarian anastomoses is observed; C: after the use of emboli (cylinders) according to the invention retrograde contrast agent injection of the right ovarian artery ceases, embolization with emboli (spheres) according to the invention is performed as described in Example 8; D: after the use of emboli (cylinders) according to the invention, retrograde contrast agent injection of the left ovarian artery ceases, followed by embolization with emboli (spheres) according to the invention as described in Example 8. E: survey angiogram of the pelvic arteries prior to uterine artery embolization reveals hypertrophied uterine arteries supplying nodules of uterine leiomyoma in the uterine body; F: survey angiogram of the pelvic arteries after completion of separate combined embolization of uterine arteries - hyperplastic uterine arteries are not filled with a radiopaque substance.

[0045] Fig. 12 represents angiograms of a female patient D with uterine leiomyoma as described in Example 8: A: aortogram; the dilated and convoluted uterine arteries (conical arrows) and the dilated and tortuous ovarian artery (standard arrows) are visualized; B: selective arteriogram; through arterio-arterial anastomoses of type I, the dilated and tortuous left ovarian artery retrogradely contrasts (standard arrows).

[0046] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0047] The expression “emboli” in the context of the present invention refers to an embolization system according to the invention which is able to lodges in a blood vessel and blocks it.

[0048] The expression “embolization system” in the context of the present invention refers to hydrogel spherical or cylindrical cross-linked poly HEMA particles or a mixture thereof according to the invention useful as embolizing agents, in particular vascular embolization or chemoembolization.

[0049] The expression “porosity” in the context of the invention refers to the size of the pores in the hydrogel structure at room temperature under atmospheric pressure as measured by solvent replacement methods or as described in Foudazi et al., 2023, Langmuir, 39, 6, 2092-2111. Typically, the porosity of the hydrogel spherical or cylindrical cross-linked poly HEMA particles according to the invention have a porosity from about 76 to about 85%.

[0050] The expression “compressibility” in the context of the invention refers to the mechanic compressibility of a hydrogel structure at room temperature and under atmospheric pressure as confirmed visually when passing through a transparent tube with a lumen 30% smaller than the diameter of the embolus and expressed in the percentage of maximum volume decreased with the application of a mechanical constraint. Typically, the compressibility of the hydrogel spherical or cylindrical cross-linked poly HEMA particles according to the invention have a compressibility from about 20 to about 30.

[0051] The invention is based on the unexpected finding that embolic systems according to the invention based on the porous three-dimensional polymer poly-2 -hydroxyethyl methacrylate (poly-HEMA) can be prepared as spherical or cylindrical shape with high porosity.

[0052] Those spherical- and cylindrical-shaped embolic systems, due to their high porosity can be impregnated with any active water-soluble agents (e.g. doxorubicin) and loaded with those agents through a process of physical absorption that allows for delivery of these substances to the embolization site followed by prolonged release of the agents into surrounding tissues.

[0053] Depending on the specific purpose aimed at achieving the task of embolization, these embolization systems can be used either separately or jointly. Furthermore, a joint use involves the sequential application of cylindrical poly-HEMA-based embolization systems, followed by the application of spherical-shaped poly-HEMA-based embolization systems. This combined use presents the unexpected advantage of when occlusion of the anastomosis by cylindrical emboli allows the use of spherical emboli to complete the procedure, which would not be possible otherwise.

[0054] According to a particular aspect, is provided a method for the preparation of cross-linked PHEMA particles of spherical shape, said method comprising the following steps (Table 1):

[0055] - Providing a polymerization initiating composition comprising sulfuric acid (SA), ammonium sulfate (AS) and potassium peroxodi sulfate (KPS) or ammonium persulfate (APS) in distilled degassed water at room temperature;

[0056] - Providing a dispersion medium comprising a solution of polyvinyl alcohol (PVA) in distilled degassed water prepared at a temperature of 90-95°C under intensive stirring;

[0057] - Providing a reaction mixture as a dispersed phase comprising 2-hydroxyethylmethacrylate (HEMA), a crosslinking agent (e.g. ethylene glycol dimethacrylate (EGDMA)), N,N,N',N'- tetramethylethylenediamine (TEMED) and a azoisobutyronitril (AIBN) as an internal polymerization initiator in a mixture of 1 -dodecanol and cyclohexanol;

[0058] - Adding sequentially the polymerization initiating composition to the dispersion medium, at a temperature from about 65-75°C under stirring at a speed of 80-90 rpm and, then the reaction mixture;

[0059] - Leaving the mixture at a temperature about 65-75°C under stirring at a speed of 80-90 rpm to let polymerization process to proceed until completion (e.g. for about 90-120 min);

[0060] Isolating the obtained polymer from the reaction mixture by filtration or by sedimentation (precipitation) of the resulting polymer product followed by treatment with distilled water to separate the low molecular weight fraction and auxiliary components.

[0061] According to a particular embodiment, the polymerization is achieved by suspension polymerization producing a spherical polymer material.

[0062] According to a particular embodiment, the polymerization is carried out for no more than 120 minutes at a temperature not exceeding 75 °C.

[0063] According to a particular embodiment, the polymerization initiating composition contains 1.5- 2 (wt.%) SA as a precipitant for the resulting polymer.

[0064] According to another particular embodiment, the polymerization initiating composition contains for example 0.35-1 (wt.%) APS or KPS as an external polymerization initiator. According to a particular embodiment, the polymerization initiating composition is obtained by mixing sulfuric acid (SA), potassium peroxodisulfate (KPS) or ammonium persulfate (APS) and ammonium sulfate (AS) in the following proportions (wt.%): 7.1-7.5, 2.6-3.2 and 13.7-151 (wt.%). Distilled water - the rest.

[0065] According to another particular embodiment, the dispersion medium is prepared by dissolving polyvinyl alcohol (PVA) in degassed water at a temperature of 92±3°C and stirring.

[0066] According to a particular embodiment, the molecular weight of PVA can be 80,000-140,000 g / mol, preferably 95,000-120,000, and the degree of hydrolysis can be from 85 to 99%, preferably 94-96%.

[0067] According to another particular embodiment, the reaction mixture contains 17-20, (wt.%) HEM A (e g. 18.2 wt.%).

[0068] According to another particular embodiment, the reaction mixture contains 0.4-0.7 (wt.%) EGDMA as a crosslinking agent.

[0069] According to another particular embodiment, the reaction mixture contains 1.4-2 (wt.%) N,N,N',N' -tetramethylethylenediamine (TEMED) as a polymerization co-initiator.

[0070] According to another particular embodiment, the reaction mixture contains 0.1-0.15 (wt.%) of a cross-linking agent such as azoisobutyronitril (AIBN) as an internal polymerization initiator.

[0071] According to another particular embodiment, the reaction mixture contains a mixture of 1.7- 1.9 (wt.%) 1-dodecanol and 24-26 (wt.%) cyclohexanol as a blowing agent and solvent, respectively.

[0072] According to another particular embodiment, in the polymerization mixture, suspension polymerization of a dispersed phase solution containing hydroxyethylmethacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), WA'A" -tetramethylethylenediamine (TEMED), azoisobutyronitril (AIBN), 1-dodecanol, cyclohexanol, suspended in a dispersed phase solution containing polyvinyl alcohol (PVA), ammonium persulfate (APS) or potassium persulphate (KPS), sulfuric acid, ammonium sulfate and distilled water is achieved.

[0073] According to a particular embodiment, the dispersed phase of the reaction mixture comprises (wt.%): 2-hydroxyethylmethacrylate (HEMA) - 17.11-19.04 (preferably 17.9-18.4), ethylene glycol dimethacrylate (EGDMA) - 0.48-0.69 (preferably 0.52-0.63), azoisobutyronitril (AIBN) - 0.10-0.14 (preferably 0.11-0.13), N,N,N',N' -tetramethylethylenediamine (TEMED) - 1.43-1.90 (preferably 1.6-1.8), cyclohexanol - 24.71-25.10 (preferably 24.9-25.0) and 1- dodecanol - 1.73-1.90 (preferably 1.78-1.84).

[0074] According to another particular embodiment, the polymerization initiating composition for the obtaining of spherical particles has the following composition:

[0075] According to another particular embodiment, the preparation of the polymerization mixture involves heating 120-200 ml of polyvinyl alcohol solution (preferably 150 ml) (dispersion medium) in a reactor to 65-75°C (preferably 70°C) with constant stirring at an anchor stirrer speed of 75-90 rpm (preferably 82 rpm). Upon reaching the specified temperature, a solution of a polymerization initiating composition and then the dispersed phase of the reaction mixture are introduced into the reactor. The polymerization time is 90-120 minutes (preferably 100 minutes).

[0076] According to a particular embodiment, the isolated polymer is further subjected to an eightfold washing with distilled water while stirring and heating (e.g. 70-80 °C).

[0077] According to a particular embodiment, the isolated polymer is obtained as spherical-shaped polymer product and can be stored in distilled water in a sealed container at room temperature.

[0078] According to another particular aspect, is provided a method for the preparation of cross-linked PHEMA particles of cylindrical shape, said method comprising the following steps:

[0079] - providing a polymerization composition prepared by mixing 2-hydroxyethylmethacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), N,N,N',N' -tetramethylethylenediamine (TEMED), ammonium persulfate (APS) in distilled water under stirring;

[0080] - placing the polymerization composition in tubes (capillaries) made of sterile glass or an inert such as polyether ether ketone (PEEK);

[0081] - Leaving the polymerization composition at room temperature to let polymerization process to proceed for 30-40 minutes at room temperature; - removing the polymer from the tubes to isolate polymer threads having a diameter from 0.5 mm to 10 to 150 mm the length;

[0082] - subjecting the isolated polymer threads to a washing step with water to remove low molecular weight impurities.

[0083] Typically, the reaction tube is from about 12-15 cm long with an internal diameter from about 0.5 to about 2 mm.

[0084] The- polymer threads can be cut into emboli of 1 cm long.

[0085] A method for the preparation of cross-linked PHEMA particles of cylindrical shape according to the invention, wherein the composition comprises 0.35-0.45 (wt.%) APS.

[0086] A method for the preparation of cross-linked PHEMA particles of cylindrical shape according to the invention, wherein the composition comprises (wt.%): 1.4-2 (wt.%) EGDMA as a crosslinking agent

[0087] A method for the preparation of cross-linked PHEMA particles of cylindrical shape according to the invention, wherein the composition comprises (wt.%): 32-34 (wt.%) HEMA.

[0088] A method for the preparation of cross-linked PHEMA particles of cylindrical shape according to the invention, wherein the polymerization composition comprises (wt.%): HEMA - 32.9- 33.8, EGDMA - 1.43-2.0, TEMED - 2.05-2.14, APS - 0.39-0.42, the rest being water.

[0089] According to another particular embodiment, the polymerization composition for the obtaining of cylindrical particles has the following composition:

[0090] According to another particular embodiment, the reaction mixture for the obtaining of spherical particles comprises has the following composition: According to another particular embodiment, the polymerization composition for the obtaining of cylindrical particles comprises has the following composition:

[0091] According to another particular embodiment, the polymerization mixture is the following:

[0092] According to another particular embodiment, the polymerization mixture is the following:

[0093] According to a particular embodiment, is provided a cross-linked HEMA particle obtainable from a method according to the invention.

[0094] According to a particular embodiment, the cross-linked HEMA polymer particles according to the invention have a porosity from about 76% to about 85% and a compressibility from about 20% to about 30% and have a size from about 100 to about 1’200 pm.

[0095] According to a particular embodiment, the obtained polymer particles are spherical. According to another particular embodiment, the obtained polymer particles are cylindrical and have a size from about 100 to about 1’000 pm.

[0096] According to another particular embodiment, is provided an embolization system comprising at least one cross-linked poly HEMA particle according to the invention.

[0097] According to another particular embodiment, an embolization system according to the invention further comprises active agent of interest loaded on the particle through physical interaction without the formation of chemical bonds.

[0098] According to another particular embodiment, the active agent is a water-soluble active agent.

[0099] According to another particular embodiment, the active agent is an anti-cancer agent such as doxorubicin.

[0100] According to another particular aspect, is provided an embolization system comprising at least one cross-linked poly HEMA particle of the invention for use in the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization, wherein said particle has a porosity from about 76% to about 85% and a compressibility from about 20% to about 30% and has a size from about 100 to about 1’200 pm, diameter from 500 to 1000 pm and length 1 cm.

[0101] According to another particular aspect, is provided a use of at least one cross-linked poly HEMA particle of the invention for the preparation of an embolization system for the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization.

[0102] According to another particular aspect, is provided a method for the ex-vivo preparation of an embolization system comprising an active water-soluble agent, said method comprising:

[0103] - Providing at least one cross-linked poly HEMA particle of the invention;

[0104] Contacting said at least one cross-linked poly HEMA particle with said water soluble active agent in an aqueous solution;

[0105] Incubating the obtained mixture with said active agent to reach dynamic equilibrium of absorption (at least for 1 hour);

[0106] Isolating the particle impregnated with the active agent.

[0107] Particles, loaded with drug, can be stored in the refrigerator for 2-4 hours at a temperature of 2-8°C.

[0108] For example, saturation with doxorubicin was carried out in 0.9% isotonic sodium chloride solution at a temperature of 25°C for 1.5-2.5 hours. According to the further particular embodiment, the particles are mixed with a contrast media just before injection into the vessel.

[0109] According to another particular aspect, impregnation of the particle with the active agent is achieved through physical interaction without the formation of chemical bonds.

[0110] According to another particular aspect, saturation of the particle with the active agent is achieved within about 1 to about 4 h.

[0111] According to another particular aspect, the isolating the particle impregnated with the active agent can be advantageously used as a chemoembolization agent. In particular, 80-100% desorption of the absorbed water-based active agent can be achieved in vivo.

[0112] According to another particular aspect is provided an embolization system for use in the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization.

[0113] According to a particular aspect, is provided a method for the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization, said method comprising placing at least one cross-linked poly HEMA particle or embolization system according to the invention into an artery.

[0114] According to a particular aspect, is provided a method for the treatment or prevention of a bleeding disorder, for vascular embolization, in particular chemoembolization, said method comprising placing at least one cylindrical embolization system according to the invention in a collateral vessel and at least one spherical embolization system in a main target vessel for achieving both conventional embolization and targeted delivery of active water-soluble agents to the side of implantation of the spherical and cylindrical embolization systems.

[0115] According to a more particular aspect, is provided a method for the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization in a subject in need thereof, said method comprising placing at least one cross-linked poly HEMA particle according to claims 15 or 16 or an embolization system according to claims 18 to 19 into an artery of said subject.

[0116] According to a more particular aspect, is provided a method for the treatment or prevention of a bleeding disorder, for vascular embolization, in particular chemoembolization in a patient in need thereof, said method comprising placing at least one cylindrical embolization system according to claim 15 or 16 in a collateral vessel and at least one spherical embolization system claims 18 to 19 in a main target vessel for achieving both conventional embolization and targeted delivery of active water-soluble agents to the side of implantation of the spherical and cylindrical embolization systems in said subject.

[0117] According to a particular embodiment, vascular embolization is used in the treatment of a disorder selected from a, an acute hemorrhage, a solid tumor cancer such as hepatocellular carcinoma (HCC) or other hypervascular tumors.

[0118] According to a particular aspect is provided:

[0119] - a polymerization composition for obtaining a vascular embolization agent containing 2- hydroxyethylmethacrylate, ethylene glycol dimethacrylate, N,N,N',N'- tetramethylethylenediamine, azoisobutyronitril, 1-dodecanol, cyclohexanol, suspended in a dispersed phase solution containing polyvinyl alcohol of various molecular weights and degrees of hydrolysis such as for example M.w. 95,000-120,000 and a degree of hydrolysis of 96% to achieve the retention of droplets of the dispersed phase in the dispersion medium and regulate the particle size, and initiating agent containing a mixture of ammonium persulfate or potassium persulphate, ammonium sulfate, sulfuric acid and distilled water, where all components are taken in sufficient quantities.

[0120] - a method for the production of a spherical-shaped vascular embolization agent from a polymer composition according to the invention, characterized in that the ingredients of the solutions are taken in the following content, in wt. %, and potassium persulphate (KPS) or ammonium persulfate (APS) is used as an initiating agent: a method for the production of a cylindrical-shaped vascular embolization agent from a polymer composition as described above, characterized in that the ingredients of the solutions are taken in the following content, wt. %, and ammonium persulfate (APS) is used as an initiating agent:

[0121] - a method for the production of a spherical-shaped vascular embolization agent as described above, characterized in that the diameter distribution (vol. %) is: 100-200 pm (2±1%), 200- 300 pm (5±2%), 300-400 pm (6±2%), 900-1,000 pm (4±2%), 400-500 pm (20±2%), 500- 600 pm (19±2%), 600-700 pm (17±2%), 700-800 pm (14±2%), 800-900 pm (9±2%), 1,000- 1,100 pm (2±1%), 1,100-1,200 pm (2±1%).

[0122] - a method for the production of a spherical-shaped vascular embolization agent as described above, characterized in that the diameter distribution (vol. %) is: 100-200 pm (1±1%), 200- 300 pm (5±2%), 300-400 pm (6±2%), 400-500 pm (24±2%), 500-600 pm (20±2%), 600- 700 pm (16±2%), 700-800 pm (12±2%), 800-900 pm (9±2%), 900-1,000 pm (4±2%), 1,000- 1,100 pm (2±1%), 1,100-1,200 pm (1±1%).

[0123] - a method for the production of a spherical-shaped vascular embolization agent as described above, characterized in that the diameter distribution (vol. %) is: 100-200 pm (2±1%), 200- 300 pm (3±2%), 300-400 pm (3±2%), 400-500 pm (16±2%), 500-600 pm (20±2%), 600- 700 pm (22±2%), 700-800 pm (17±2%), 800-900 pm (9±2%), (3±2%), 900-1,000 pm (3±2%), 1,000-1,100 pm (2±1%), 1,100-1,200 pm (2±1%).

[0124] - a method for the production of a spherical-shaped vascular embolization agent as described above comprising suspension polymerization of a dispersed phase solution containing 2- hydroxyethylmethacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), A,A,A',7V- tetramethylethylenediamine (TEMED), azoisobutyronitril (AIBN), 1 -dodecanol, cyclohexanol, suspended in a dispersed phase solution containing polyvinyl alcohol (PVA), water, and initiating agent containing a mixture of ammonium persulfate (APS) or potassium persulphate (KPS), sulfuric acid and ammonium sulfate for 90-120 minutes at a temperature not exceeding 65-75°C; filtering the obtained polymer product; eightfold washing of the filtrate with distilled water while stirring and heating up to 70- 80 degrees Celsius; fractionation of the obtained suspension; washing the obtained fractions with acetone in the Soxhlet apparatus and flushing in distilled water at a temperature of 80-90°C; sterilization of the obtained fractions.

[0125] - a spherical- or cylindrical-shaped vascular embolization agent obtained from a polymer composition as described above, using the method as described above, with a diameter ranging from 100 to 1,200 pm for spherical shape and 0.5 to 0.6 mm in diameter 10 mm long for cylindrical shape.

[0126] - a vascular embolization agent made from a polymeric material, in the form of a cylinder, obtained by polymerization using a solution containing 2-hydroxyethylmethacrylate, ethylene glycol dimethacrylate, N,N,N',N' - tetramethylethylenediamine, ammonium persulfate and distilled water, for 30-40 minutes at room temperature.

[0127] - a vascular embolization agent made from a polymeric material, in the form of a cylinder, according the invention, characterized in that the solution components are taken in the following content, wt. %: a vascular embolization agent according to the invention, characterized in that the diameter of the cylinder is 0.5-0.6 mm, and the length is 10 mm.

[0128] - a use of the spherical- and cylindrical-shaped embolization agent, obtained on the basis of polymer compositions, for transarterial chemoembolization by impregnation with water- soluble medicinal drugs and physical adsorption on the polymer surface and filling the polymer matrix pores, allowing the drug to be fully released in the tissues of the embolized organ.

[0129] - an agent for vascular embolization, made in form of a sphere from polymer material, is obtained during suspension polymerization of a dispersed phase solution containing 2- hydroxyethylmethacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), A,A,A'A"- tetramethylethylenediamine (TEMED), azoisobutyronitril (AIBN), 1 -dodecanol, cyclohexanol, suspended in a dispersed phase solution containing polyvinyl alcohol (PVA), distilled water and catalyst prepared by mixing solutions of sulfuric acid (SA), ammonium sulfate (AS) and ammonium persulfate (APS) or potassium persulphate (KPS). At a temperature not exceeding 75 °C, the process time does not exceed 120 minutes. In this case, the initiator agents are APS, sulfuric acid, ammonium sulfate and azaisobutyronitrile (AIBN) as internal polymerization initiator. All ingredients are taken in quantity sufficient to obtain a sphere-shaped vascular embolization agent with a diameter of 100-1,200 pm, as indicated in Table 1

[0130] Table 1. The ingredients of solutions for obtaining spherical-shaped poly-HEMA are taken in the following content (wt. %):

[0131] - cylindrical-shaped agent for vascular embolization is obtained by polymerizing a solution that contains HEMA, EGDMA, TEMED, APS and distilled water at room temperature for 30- 40 minutes, as indicated in Table 2.

[0132] Table 2. The ingredients of solutions for obtaining cylindrical-shaped poly-HEMA are taken in the following content, (wt. %):

[0133] The technical result of the proposed embolization systems is improving the efficiency of the vascular embolization due to its increased elasticity that contributes to restoring original shape after possible deformations to which the agent is exposed when delivered through a catheter to embolization site.

[0134] EXAMPLES

[0135] Example 1: Preparation of embolization systems according to the invention

[0136] Spherical-shaped embolization system

[0137] Hydrogel spherical cross-linked poly HEMA particles were obtained in aqueous solution by cross-linking 2-hydroxyethylmethacrylate (HEMA) monomers under the influence of a polymerization initiating system comprising ammonium persulfate (APS) or potassium persulfate (KPS) in presence of N,N,N',N' -tetramethylethylenediamine (TEMED) and a crosslinking agent (e.g. ethylene glycol dimethacrylate (EGDMA)) at a monomer-crosslinking agent molar ratio of from about 43: 1 mol / mol to 48: 1 mol / mol (e.g. 46.7: 1 mol / mol) as follows:

[0138] Step 1: Provision of a polymerization initiating composition

[0139] Upon reaching the specified temperature, a polymerization initiating composition is introduced into the reactor: 2 g (27%) sulfuric acid, 4.5 g (61.6%) ammonium sulfate and 0.8 g (11.0%) Potassium peroxodi sulfate (KPS) and 4 g ammonium sulfate in 20 ml of distilled water. Ammonium sulfate is necessary for precipitating (salting out) the oligomers formed at the initial stage.

[0140] Step 2: Preparation of a dispersion medium before adding the dispersed phase

[0141] 150 ml of an aqueous solution containing 1.5 g (1.0%) polyvinyl alcohol (PVA, M.w. 95,000- 120,000, degree of hydrolysis 96%) is introduced into a 400 ml polymerization reactor. The role of PVA is to keep the resulting droplets (spheres) of the dispersed phase from reverse “sticking together” until the start of polymerization, when the resulting polymer becomes insoluble. At the anchor mixer start (80±2 rpm), the mixture is heated up to 70°C.

[0142] Step 3: Provision of a reaction mixture containing HEMA monomers and cross-linking agent

[0143] A reaction mixture is prepared, said mixture comprises: 2-hydroxyethylmethacrylate (HEMA) - 20 g (37.94%) as the monomer, ethylene glycol dimethacrylate (EGDMA) - 0.6 g (1.14%) as a crosslinking agent, N,N,N',N' -tetramethylethylenediamine (TEMED) - 2 g (3.79%) as coinitiator of polymerization, to accelerate the catalyst formed by mixing PSA and sulfuric acid, azoisobutyronitril (AIBN) - 0.12 g (0.23%) as internal polymerization initiator, 1-dodecanol - 3 g (5.69%), cyclohexanol - 27 g (51.21%). Dodecanol is used as a blowing agent, since the monomer and, moreover, the resulting polymer are poorly soluble in it. Step 4: Polymerization process

[0144] The polymerization initiating composition is added to the dispersion medium, then the 52.7 g of the reaction mixture above is introduced in the polymerization reactor:

[0145] The mixture is let polymerized for a period of about 90 minutes at a rotation speed of anchor mixer at 80-90 rpm at a temperature of 70°C (65-75°C).

[0146] Step 5: Isolation of the cross-linked PHEMA polymer

[0147] Upon completion of the polymerization, the resulting polymer product is filtered passing through a sieve with a pore size of 300 microns and subjected to an eightfold washing with distilled water while stirring and heating (at 70-80 °C) separate low molecular products and auxiliary reagents. Ratio of the isolated polymer product to distilled water is 1 / 10 (by vol.). The polymer is obtained as spherical-shaped polymer product and is stored in distilled water in a sealed container at room temperature.

[0148] Step 6: Further separation of the spherical-shaped polymer particles

[0149] The obtained spherical-shaped polymer particles are isolated by fractionation carried out in distilled water using sieves with cell sizes ranging from 100 to 1,200 pm. Fractionation is carried out in distilled water using sieves with cell sizes ranging from 100 to 1,200 pm equipped with edges and having a diameter of 20 cm. For this purpose, a polymer product is placed on the sieve, and the volume of the fractionated suspension should not exceed 5% of the height of the edges. The sieve with the polymer is placed in a container filled with distilled water, and separation of the fraction with diameters matching or smaller than the sieve pores is achieved by gently rocking the sieve. The separated fraction is placed on the sieve with a smaller pore diameter, and further fractionation is carried out. The polymer product remaining on the sieve is washed off into a separate container.

[0150] To remove hydrophobic impurities, the obtained fractions are washed with acetone in the Soxhlet extraction apparatus. Afterward, a final wash is carried out in distilled water at a temperature of 80-90°C at a polymer product / water ratio of 1 / 10 by volume, changing the water at least eight times. The obtained fractions are packaged, replacing distilled water with an isotonic solution, hermetically sealed and sterilized.

[0151] According to this example, the following diameter distribution (wt. %) is obtained: 100- 200 pm (2±1%), 200-300 pm (5±2%), 300-400 pm (6±2%), 900-1,000 pm (4±2%), 400- 500 pm (20±2%), 500-600 pm (19±2%), 600-700 pm (17±2%), 700-800 pm (14±2%), 800- 900 pm (9±2%), 1,000-1,100 pm (2±1%), 1,100-1,200 pm (2±1%).

[0152] Example 2: Preparation of embolization systems according to the invention

[0153] A spherical-shaped embolization system is prepared as described in Example 1 with the following conditions to vary the sizes of the resulting fractions:

[0154] 200 ml of an aqueous solution containing 2.4 g (1.2%) polyvinyl alcohol (PVA, M.w. 86,000- 102,000, degree of hydrolysis 96%) is introduced into a 600 ml polymerization reactor. At the impeller mixer start (90±2 rpm), the mixture is heated up to 75°C. Upon reaching the specified temperature, the initiating agent of the following composition is introduced into the reactor: 3 g (26,1%) sulfuric acid, 7.0 g (60.9%) ammonium sulfate and 1.5 g (13.0%) KPS in 35 ml of distilled water. Then, 74.7 g of a mixture of the following composition is introduced: HEMA - 30 g (40,17%), EGDMA - 1.0 g (1.34%), TEMED - 3.5 g (4.69%), AIBN - 0.18 g (0.24%), 1-dodecanol - 4.0 g (5.36%), cyclohexanol - 36 g (48.21%). Afterward, polymerization is carried out for 100 minutes. The polymer product is processed as described in Example 1. Fractionation is carried out in distilled water using sieves with cell sizes ranging from 100 to 1,200 pm. Diameter distribution (vol.%): 100-200 pm (1±1%), 200-300 pm (5±2%), 300- 400 pm (6±2%), 400-500 pm (24±2%), 500-600 pm (20±2%), 600-700 pm (16±2%), 700- 800 pm (12±2%), 800-900 pm (9±2%), 900-1,000 pm (4±2%), 1,000-1,100 pm (2±1%), 1,100-1,200 pm (1±1%). The obtained fractions are processed as described in Example 1.

[0155] Example 3: Preparation of embolization systems according to the invention

[0156] A spherical-shaped embolization system is prepared as described in Example 1 with the following conditions to vary the sizes of the resulting fractions:

[0157] 150 ml of an aqueous solution containing 2.25 g (1.5%) polyvinyl alcohol (PVA, M.w. 95,000- 120,000, degree of hydrolysis 96%) is introduced into a 400 ml polymerization reactor. At the anchor mixer start (85±2 rpm), the mixture is heated up to 65°C. Upon reaching the specified temperature, the initiating agent of the following composition is introduced into the reactor: 2 g (29,2%) sulfuric acid, 4.0 g (58.4%) ammonium sulfate and 0.85 g (12.4%) ammonium persulfate (APS) in 20 ml of distilled water. Then, the polymerization solution is introduced according to Example 1. In 120 minutes, the process is stopped. The mixture is processed according to Example 1. Fractionation is carried out in distilled water using sieves with cell sizes ranging from 100 to 1,200 pm. According to this example, the following diameter distribution (wt. %) is obtained: 100-200 pm (2±1%), 200-300 pm (3±2%), 300-400 pm (3±2%), 400-500 pm (16±2%), 500-600 pm (20±2%), 600-700 pm (22±2%), 700-800 pm (17±2%), 800-900 pm (9±2%), (3±2%), 900-1,000 pm (3±2%), 1,000-1,100 pm (2±1%), 1,100-1,200 un (2±1%). The obtained fractions are processed as described in Example 1.

[0158] As shown in Examples 1-3, for production of the spherical-shaped embolization systems based on poly-HEMA, a sequential system for initiating the polymerization process is used, wherein the primary initiation is performed with the APS / TEMED system and the further process is ensured by AIBN — the internal polymerization initiating agent. This combination of ingredients in dispersion media and dispersed phase allows for obtaining a spherical-shaped agent for vascular embolization, and during the process to prevent the coalescence of the dispersed phase drops. This effect is based on the fact that the primary initiation of the process occurs at the boundary of the dispersed and dispersion phases with a shell formation around the dispersed phase. The process is based on the effect of accelerating the decay of the initiating agent (e.g. APS, KPS) by the initiation activator (TEMED) {“Polyesteracrylates”, A. A. Berlin, T. Ya. Kefeli, G. V. Korolev, Nauka Publishing House, Moscow, 1967, 244). The further polymerization process takes place inside the formed sphere due to the AIBN thermal decomposition. Elasticity is regulated due to the content of EGDMA crosslinker under the process conditions in the range of 1.43-2.0 wt%.

[0159] Example 4: Preparation of embolization systems according to the invention

[0160] Cylindrical PHEMA emboli are useful for closure of relatively large afferent arteries and those are produced in a calibrated tube by in-block polymerization as follows. These emboli can be used in some cases as an alternative to metal wire embolization coils due to their large particle size and shape.

[0161] Cylindrical -shaped embolization system

[0162] To produce cylindrical emboli, polymerization is carried out in sterile glass tubes 12-15 cm long with an internal diameter of 0.5-2.0 mm (e.g. 0.5, 0.6, 0.75, 1.0 mm).

[0163] The tube of a calibrated diameter made of glass or PEEK polymer is filled with a pre-prepared solution containing the following components: HEMA 1.44 g (32.9%), EGDMA 0.063 g (1.43%), TEMED 0.09 g (2.05%), APS 0.0175 g (0.39 %), distilled water 2.79 g (63.43%). After filling the tube with the solution, polymerization is carried out at room temperature for 30-40 minutes. After this, the resulting polymer thread is removed by pushing out with a thin wire or under pressure using a syringe attached to one end of the tube. The resulting thread is washed with water, divided into emboli 10 mm long and washed with distilled water to remove oligomers and auxiliary reagents. Typically, flushing is carried out at an embolic-water ratio of 1 to 10 by volume. In this case, the number of washings cannot be less than 10-12 times for 3-5 hours each at a temperature of 70-80°C.

[0164] Example 5: Preparation of embolization systems according to the invention

[0165] Polymer tube made of inert material (PEEK, glass) of a calibrated internal diameter (0.5-0.7 mm) is filled with a pre-prepared solution containing the following components: HEMA 1.42 g (33.8%), EGDMA 0.084 g (2.0%), TEMED 0.09 g (2.14%), APS 0.0175 g (0.42%), distilled water 2.59 g (61.73%). Polymerization is carried out at room temperature for about 30 to 40 minutes. The resulting polymer threads are removed from the tube and processed according to example 4

[0166] Example 6: Characterization of embolization systems according to the invention

[0167] Spherical- or cylindrical-shaped embolization systems based on poly-HEMA, obtained according to Examples 1-5 with the specified ingredient ratio, form a cross-linked hydrogel that can contain up to 67% water in its pores as determined by gravimetric method. Both spherical- and cylindrical-shaped embolization particles, with their porous structure, can be loaded with water-soluble medicinal drugs as supported in the examples below.

[0168] To study the surface morphology and internal structure of porous emboli, a YSM15300 LV scanning electron microscope (Jeol, Japan) was used. The samples were contrasted by gold sputtering using a “Jeol” YFC11100 E Ion sputtering device. Spraying thickness - 40E. Electronic scanning data showed that for the cylindrical embolization system material prepared according to Example 4, the size of the globules ranges from 2-10 microns, the packaging is loose, linear chain aggregates of globules organize multilayer strands, leading to the organization of a macrocellular structure. In turn, the latter create macropores up to several tens of microns in size (Fig. 3).

[0169] The porosity of the spherical embolization material (particles from about 800-900 pm) obtained prepared according to Example 1 was measured by determining their water content and assessing the decrease in their volume during the drying process.

[0170] Before determining the water content, residual amounts of auxiliary substances used in their preparation were removed by a washing step in ethyl alcohol and then in water at 90°C. The material thus obtained was placed on a pre-mixed Petri dish, excess water was removed with filter paper, the initial weight was determined (0.970 g) and the sample was placed in an oven at a temperature of 50°C. Weight changes were determined by weighing at 5 -minute intervals. The experiment was completed when the sample reached a constant weight (0.188±0.002 g). Weight loss of the emboli versus time of drying as represented on Figure 4, shows that water loss from spherical emboli at 50°C occurs within 45 minutes. Residual weight is 20±l%. Thus, the amount of water retained by spherical poly-HEMA on the surface and in the pores is up to 67% of the initial weight of the emboli.

[0171] The diameter of the initial spherical particles was 900 pm, and the diameter of the dried sphere to be 600 pm as measured by optical microsopy and as illustrated on Fig. 5. In this case, the volume of these spheres will be 0.3817 and 0.1131 pm3, respectively. The volume of the dried sphere relative to the volume of the original will be 29.6%. If we assume that the material is completely dry and does not contain pores (all pores have “collapsed”), then their volume in the original sphere is up to 70%. Thus, it can be deduced that the spherical particles retain up to 80% of water on the surface and in the pores, and the total volume of pores of various structures is up to85%.

[0172] Example 7: In vitro loading of embolization systems according to the invention with an agent of therapeutic interest

[0173] In order to investigate the possibility of using an embolization material according to the invention for the accumulation and targeted delivery of a drug, the cytostatic drug doxorubicin hydrochloride was used as a model for studying the dynamics of its accumulation in the polymer, the rate and volume of release in the environment depending on the level of its acidity, the presence of blood plasma proteins, under conditions of a stationary and dynamic environment (in a flow) as described below.

[0174] Fragments of embolization material (EM) from a hydrogel based on poly-HEMA of a cylindrical shape with a diameter of 0.75 mm and a length of 10 mm, obtained by precipitation copolymerization of 2 hydroxyethyl methacrylate with ethylene glycol dimethacrylate, with a method of the invention as described in Example 5.

[0175] Doxorubicin, which belongs to the group of anthracycline antibiotics and is widely used as a cytostatic drug in the treatment of many types of malignant tumors, was chosen as a drug model to study the possibility of targeted delivery. To standardize the results, a commercial antitumor drug, Doxorubicin-LENS (DR) (manufactured by LENS-Pharm LLC, Russia) was used, containing, in addition to the active substance doxorubicin hydrochloride in a dose of 50 mg for a single injection, the excipient mannitol.

[0176] The doxorubicin molecule (1) contains three conjugated aromatic hydroxyanthracycline rings that act as a chromophore, a cyclohexane moiety, and the associated aminosaccharide daunosamine). Doxorubicin has a specific ultraviolet spectrum (UV spectrum) with several maxima at wavelengths of 231, 252, 290 and 480 nm, which makes it possible to determine the concentration of this substance in experimental solutions using UV spectrometry. (Doxorubicin molecule)

[0177] Saturation of EM with doxorubicin was carried out in 0.9% isotonic sodium chloride solution at a temperature of 25°C for 1.5-2.5 hours. The amount of absorbed drug was determined by measuring the concentration of doxorubicin in solution using a UV spectrophotometer at a wavelength of 480 nm, according to a pre-constructed calibration graph. Samples of embolic materials were saturated with various amounts of doxorubicin, the final content of the drug in them was 0.25, 0.5 and 1.0 mg.

[0178] To study the influence of the medium on the process of doxorubicin release from the polymer matrix, model media were used - solutions with different pH and different protein contents. The model media chosen were 0.9% isotonic sodium chloride solution (pH 7.4), phosphate buffer (pH 6.89) and 5% solution of human albumin (HA) in isotonic solution and phosphate buffer, simulating blood plasma. Tests for the release of doxorubicin were carried out at a temperature of 40°C in two modes: stationary (without replacement of the release medium) and non-stationary (with replacement of the medium at certain intervals), simulating continued blood flow. The release of doxorubicin was also monitored using UV spectroscopy, and its amount was determined from calibration graphs constructed for each model mixture. Each experiment was repeated at least three times.

[0179] Results

[0180] A polymer EM saturated with a drug can be presented in the form of a three-dimensional network of poly-HEMA macromolecules containing doxorubicin molecules, which occupy the free space between the network chains and are reversibly adsorbed on the polymer surface.

[0181] However, taking into account the highly organized three-dimensional structure with the formation of many pores in the hydrogel, the distribution and accumulation of drugs occurs by diffusion throughout the entire volume of the polymer. Thus, this process should be considered absorption - the absorption of a dissolved drug by the entire mass of the polymer without the formation of chemical covalent bonds. The accumulation of drugs in the volume of EM occurs by diffusion in the direction of the concentration gradient from a concentrated solution into the thickness of the polymer until the concentration of drugs in the solution and inside the polymer is equalized.

[0182] Theoretically, the polymer (poly-HEMA) can be saturated to an equilibrium state where the rate of drug absorption becomes equal to its desorption. This phenomenon can be observed when the polymer remains in solution for as long as possible. If the procedure for saturating the emboli is carried out in practice (immediately before their use), this process is limited to a reasonable time. In particular, the preparation time of the drug can be limited to 1.5-2.5 hours.

[0183] Based on this, saturation experiments were conducted during this period.

[0184] During drug release, the drug is desorbed and diffuses in the direction of the concentration gradient through the hydrated polymer matrix into an environment that does not contain the molecules of the substance that make up the drug. The diffusion of doxorubicin molecules and the relaxation of the poly-HEMA chain determine the type of release mechanism that the drug molecules follow. To analyze data on the release of doxorubicin in vitro, the equation proposed by Korsmeyer et al., 1983, supra was used: where Mtand M, are the masses of the drug released at the moment t and in the equilibrium state, respectively; k is a constant that takes into account the geometric and structural characteristics of high-molecular network systems and drugs; n is a diffusion index that describes the mechanism of drug transport. This equation is valid for Mt / Mco < 60%. If the process is controlled by diffusion, then the value of n is close to 0.5. In addition, the diffusion index depends on the shape of the hydrogel. So, for cylindrical polymer particles n = 0.45. At a value of n from 0.89 to 1, the drug release process is controlled by the relaxation of polymer chains. In the range from 0.45 to 0.89, both mechanisms operate simultaneously.

[0185] Simulation of stasis parameters and continued blood flow

[0186] During embolization, several stages can be distinguished: at the initial stage, EM is in the blood flow, as emboli fill the vascular bed, the blood flow slows down, and when the vessel is completely blocked, the blood flow practically stops. Therefore, two modes were studied that simulate the initial and final stages of embolization: a non-stationary mode with periodic 1 replacement of model media and a stationary mode without replacement of model media, corresponding to maximum occlusion of the vascular bed - the stasis mode. The results of drug isolation in 0.9% isotonic sodium chloride solution are shown in Fig. 6.

[0187] As can be seen from the data presented, under stationary experimental conditions, desorption of doxorubicin actively occurs during the first hour of observation (curves 1 and 3 in Fig. 6). After 3 hours, the amount of doxorubicin released was -60% and -55% for EM (embolic material) containing 0.5 and 0.25 mg, respectively. During the further measurement period, the amount of desorbed doxorubicin remains virtually unchanged. With periodic replacement of the release medium, doxorubicin is desorbed exponentially (curves 2 and 4 in Fig. 7); after 5 hours, 92% and 81% of the initial content are released for EM containing 0.5 and 0.25 mg, respectively. The time intervals for desorption of 50% of doxorubicin from the initial amount, given in Table 3 below, demonstrate that under non-stationary conditions (mode of maintained blood flow) in any model environment, drug release occurs faster.

[0188] Table 3

[0189] Note: DR - doxorubicin; EM- embolic material; HA — human albumin.

[0190] Mechanism of release of doxorubicin

[0191] To establish the release mechanism of doxorubicin, the parameters n for equation 1 were calculated, the calculation results are shown in Table 2 of the diffusion index n. The values of n under static conditions ranged from 0.33 to 0.48, which is evidence that the process obeys Fick's first law and is controlled by diffusion. Under dynamic conditions (model of preserved blood flow), the values of the diffusion index are in the range of 0.45-0.79, thus, in this case, the release mechanism is anomalous in nature and, in addition to diffusion, the relaxation of polymer chains makes a contribution to the release of doxorubicin. These results confirm that the main mechanism of doxorubicin release is diffusion, which is quite expected, since the interaction of doxorubicin with the hydrogel is non-covalent in nature. This nature of the interaction is the reason for the “explosive” release of DR, and the time for release of 50% of the drug is no more than 2 hours (Table 4) which is more than 2 times compared to 21% for DC Bead microspheres (Boston Scientific, Marlborough, Massachusetts) and more than 6 times compared to 8% for HepaSphere (MeritMedical, SouthJordan, Utah) (de Baere et al., 2016, supra).

[0192] Table 4

[0193] Note - *R2 - correlation coefficient; DR - doxorubicin, HA - human albumin, EM- embolic material.

[0194] It was found that under stationary experimental conditions, drug desorption actively occurs during the first hour of observation. Under non-stationary conditions simulating blood flow, drug release occurs faster in any model environment. The amount of released drugs depends not only on the initial content of the drug in the embolic material, but also on the composition of the environment. The most effective release of doxorubicin occurs in a more acidic environment, characteristic of tissues during a pathological process. The amount of released doxorubicin in the presence of human albumin increases, especially at pH 6.86, and after 5 hours reaches 80% under stationary conditions and 95% under non-stationary conditions with periodic replacement of the release medium as described above.

[0195] Example 8: Clinical use of embolization systems of the invention Below are provided examples of clinical use of the poly-HEMA-based embolization systems of the invention for vascular occlusion to stop bleeding without arterial ligation, as well as for endovascular embolization in the treatment of various neoplasms.

[0196] Spherical-shaped microparticles

[0197] A method of using spherical-shaped embolization systems according to the invention is illustrated by the following clinical example: patient A., age 17, was hospitalized with complaints of pulsating formation on the left half-face, pain, and intermittent bleeding from the gingival surface of the left upper teeth. The patient has been ill since birth. Diagnosed with: arteriovenous hemangioma of the left half-face. At the age of 7, the left external carotid artery was ligated with a good primary effect. After a year, the disease recurrence was observed, and removal of the hemangioma was recognized impossible. Upon admission to the hospital, the condition was almost satisfactory, there was a pulsating tumor-like formation in the left halfface, angiomatously changed plus tissue in the hard palate area on the left, with a fibrin deposit, was detected upon examination of the oral cavity. Systolic thrill was palpable over the formation. On auscultation, a continuous systolodiastolic murmur was detected (Fig. 7 A-D). The ultrasonic Doppler examination determines an increase in the linear velocity of blood flow in the common carotid arteries: on the right to 63 cm / sec, on the left to 83 cm / sec. The volumetric blood flow velocity on the right is 237 mL / min, on the left 890 mL / min, indicating an elevated flow rate. The patient underwent several stages of selective arteriography of all brachiocephalic arteries to detect afferent branches.

[0198] Based on the arteriography results, the left external carotid artery was ligated at its origin. Participation in the blood supply to the angiomatous tissue of the branches of the external carotid artery on the right, inter-arterial anastomoses from the internal carotid artery system on the left, and the branches of the thyrocervical trunk on the left. The last of the listed sources was the most significant one (Fig. 7C).

[0199] Diagnosed with: Congenital arteriovenous angiodysplasia of the left half-face and hard palate on the left, macrofistulose form. Condition after surgical ligation of the left external carotid artery. Relapsing bleeding from angiomatous tissue in the hard palate area.

[0200] Since radical removal of angiomatous tissue was recognized impossible, the patient underwent several stages of X-ray endovascular occlusion of afferent vessels using an effective amount of spherical-shaped hydrogel emboli with a diameter of 900-1,000 pm, a total of up to 20 ml of microspheres prepared according to Example 2, and transcatheter sclerotherapy with a 96% ethyl alcohol solution.

[0201] During the follow-up arteriography of the afferent artery systems, a complete effect of embolization was observed (Fig. 8A-B). The post-embolization period went smoothly; short episodes of hyperthermia up to 37.3-37.8°C.

[0202] The only vessels that have not underwent embolization were the interarterial anastomoses from the left internal carotid artery pool due to the high risk of embolic complications in the brain arteries, the development of critical ischemia of angiomatous tissue in the hard palate area and subsequent necrotic changes. Disappearance of the formation pulsating and the absence of systolic thrill were objectively observed; at auscultation, no systolodiastolic murmur was detected. The patient was discharged in satisfactory condition.

[0203] In this case, the technique of multi-stage X-ray endovascular occlusion of the afferent arteries with spherical-shaped hydrogel microspheres was the method of choice and significantly improved the patient’s condition, although, it was undoubtedly of a palliative nature. The partial cosmetic effect of X-ray endovascular occlusion and sclerotherapy is shown in Fig. 8C. Thus, the embolization system of the invention in the form of microspheres, when used, does not apply pressure to the walls of the embolized vessel and does not cause destructive changes in the adjacent tissues, promotes reliable thrombus formation within the lumen of the vascular bed. Furthermore, due to its spherical shape, high elasticity and lack of adhesion, this agent can be easily delivered through the catheter and occludes the vessels. The agent meets all medical requirements for drugs used in vascular surgery.

[0204] Cylindrical-shaped microparticles

[0205] A method of embolization using cylindrical-shaped embolic agent is illustrated by the following clinical example: patient R., age 17, was admitted with complaints of the presence of a pulsating tumor-like formation in the upper part of the posterior neck, at the border with the occipital area. The formation was painful when palpated. Superficial injuries to the formation resulted in the development of intense bleeding. Selective arteriography detected: the carotid arteries were located typically, no abnormality, the right occipital artery was enlarged and tortuous. From the above artery, in the neck posterior surface area below the occipital protuberance, contrast enhancement of the angiomatous tissue with a pronounced derivative circulation and a slight reflux of a radiopaque substance into the contralateral conominal artery was observed (Fig. 9 A, B). The left common carotid artery was selectively catheterized and arteriography of the left carotid artery system was performed. Practically mirror-like pattern was obtained as at the examination of the right carotid system, with a slightly more significant blood supply to the angiomatous tissue from the left occipital artery. Conclusion: arteriovenous dysplasia in the occipital area, macrofistulose form, limited lesion.

[0206] The treatment using X-ray endovascular occlusion of the occipital arteries on both sides was planned. The choice of embolization agent was determined by the proximity of the occipital artery branches to the cranial bones and their anastomoses with the branches of the internal carotid arteries supplying blood to the brain matter. For endovascular occlusion, the cylindrical-shaped embolic hydrogel was selected. Both occipital arteries were alternately endovascularly occluded with the vascular embolization agents made of cylindrical-shaped hydrogel with a diameter of 0.5-0.6 mm and a length of 1 cm. 180 cylindrical-shaped microemboli (with a diameter of 0.5-0.6 mm) prepared as described in Example 4 were required to occlude the left occipital artery until the symptom of “stop-contrast” and reflux in trunk of the external carotid artery appeared. After introducing hydrogel emboli, both occipital arteries were additionally occluded with Gianturco metal coils. The right occipital artery was also endovascularly occluded with the vascular embolization agents made of cylindricalshaped hydrogel with a diameter of 0.5-0.6 mm and a length of 1 cm. 120 cylindrical-shaped microemboli were required to occlude. During the follow-up arteriography from the trunk of the left external carotid artery, contrast enhancement of the angiomatous tissue was not obtained. The occipital artery stump was enhanced (Fig. 10A, B). On the third day after embolization, the bloodless resection of the occipital area angiomatous tissue was performed (up to 100 ml). The post-surgical period went smoothly, the wound healed by primary intention, the stitches were removed on the 10th day after the surgery. The patient was discharged in satisfactory condition on the 14th day after the surgery. Follow-up in the post- surgical period lasted two years. No data of disease recurrence has been detected.

[0207] Combined use of cylindrical- and spherical-shaped embolic agents

[0208] A method of combined use of cylindrical- and spherical-shaped embolic agents is illustrated by the following clinical example: patient V., age 50, medical record No. 548. Diagnosis: uterine submucous myoma. Hyperpolymenorrhea syndrome. Uterine bleeding. Complication of the disease — severe posthemorrhagic anemia.

[0209] The title of the surgery: angiography and embolization of the left and right uterine arteries. Blood parameters on admission on February 25, 2007: red blood cells 1.2 10*12 g / 1, hemoglobin 32, hematocrit 14.3, leukocytes 5.8 10*9, ESR 23 mm / h, platelets 160 10*9, PTI 96%, fibrinogen 3.8 g / 1, aPTT 23 s, thrombin time 13 s. Ultrasound duplex scanning: uterus in the center of the pelvis, dimensions 81*55*81 mm. Sessile cervical node with a diameter of up to 51*34 mm. Submucous node with a diameter of 44*36 mm, deforming the cervical canal and uterine cavity. Interstitial node with a diameter of 44x32 mm in the uterine fundus area. Duration of surgery: 45 minutes. Surgical record: puncture of the right femoral artery was performed under local anesthesia with a solution of novocaine 0.25%-10.0 ml. 6F introducer was installed in the arterial lumen according to Sei dinger’s procedure. Roberts 5F catheter was passed through the introducer. The catheter was deployed in the aortic arch and lowered into the right, then into the left contralateral iliac artery, and then into the mouth of the corresponding uterine artery. Radiopaque substance was introduced “by hand”. The video and a series of images were taken (Fig. 11 A, B).

[0210] The obtained angiograms demonstrated significant hyperplasia of the uterine arteries on both sides that indicated a pronounced pathological blood supply to the leiomyoma nodes located in the myometrium (contour arrow at Fig.11 A,B). This is the cause of numerous episodes of hypermenorrhea. Furthermore, the hyperplastic uterine arteries on the right and left have a large number of intervascular anastomoses with arteries supplying blood to the ovaries. This is indicated by the retrograde injection with a radiopaque substance of the ovarian arteries (filled arrow at Fig.11 A,B). In the presence of a pronounced network of intervascular anastomoses, it is completely contraindicated to carry out transcatheter embolization of uterine arteries using microemboli with a diameter of 300-500 pm, according to modern recommendations.

[0211] In the presence of the pronounced intervascular anastomoses, embolization with microemboli could certainly result in retrograde reflux of microemboli into the ovarian arteries and further into the aorta. As a result, there may be inadvertent embolization of arteries supplying the intestines, spinal, pelvic arteries, and lower limb vessels with the risk of ischemic injury to the spinal cord, viscera, and limbs.

[0212] Therefore, in the treatment of this patient, a combined embolization was carried out: first, with cylindrical-shaped emboli that cannot penetrate the network of anastomoses between the uterine and ovarian arteries. 20 hydrogel cylinders with a diameter of 0.5 and 0.7 mm and a length of 10 mm were introduced into each uterine artery until the appearance of the “separation of the uterine and ovarian arteries on each side” sign. (Fig. 11C,D).

[0213] Afterward, embolization of the uterine arteries was continued with spherical-shaped microemboli with a diameter of 300-400 pm. The uterine arteries were not visualized on the follow-up angiogram (Fig. 11E,F). To complete the catheter surgery, the catheter and introducer were removed from the femoral artery. Hemostasis was performed by application of pressure. The aseptic dressing was applied. The post-surgical period went smoothly.

[0214] In clinical trial 19 patients with leiomyoma submitted to the uterine artery embolization were diagnosed with ovarian artery hyperplasia or interarterial uterine-ovarian anastomoses at the diagnostic stage . (Fig. 12 A,B) Due to the detection of uterine-ovarian anastomoses before uterine artery embolization, cylindrical emboli prepared as described in Example 4 (10 mm long, 500-700 pm in diameter) were used in order to exclude occlusion of the ovarian arteries and ovarian ischemia. These emboli occluded only the bed of the uterine artery and were unable to overcome the uterine-ovarian interarterial anastomoses. For the occlusion of each uterine artery, 20 to 40 cylindrical emboli as described in Example 4 were required (Fig. 2B). Uterine artery embolization was completed using standard emboli 500-700 pm microspheres (Fig 2A). None amenorrhea was noted in the studied group of patients during the period of outpatient observation up to 18 months

[0215] Thus, the above examples further support the usefulness of method of treatment by selective vascular occlusion using the specified vascular embolization systems according to the invention.

[0216] Furthermore, both spherical- and cylindrical-shaped embolization systems obtained by the method described above can be impregnated with water-soluble drug and used in a process of chemoembolization. Before the embolization process, spherical- and cylindrical-shaped compositions for embolization, obtained on the basis of polymer compositions, can be saturated with the required water-soluble medicinal drug to improve the local therapeutic effect of the procedure and achieve a prolonged effect on the embolized organ. Furthermore, the process of drug impregnation consists of physical adsorption on the surface of the polymer and filling the polymer matrix pores, allowing the drug to be fully released into the tissues of the embolized organ.

Claims

Claims1. A method for the preparation of cross-linked PHEMA particles, said method comprising the following steps:- Providing a polymerization initiating composition comprising sulfuric acid (SA), ammonium sulfate (AS) and potassium peroxodi sulfate (KPS) or ammonium persulfate (APS) in distilled degassed water at room temperature;- Providing a dispersion medium comprising a solution of polyvinyl alcohol (PVA) in distilled degassed water prepared at a temperature of 90-95°C under intensive stirring;- Providing a reaction mixture as a dispersed phase comprising 2-hydroxyethylmethacrylate (HEMA), a crosslinking agent (e.g. ethylene glycol dimethacrylate (EGDMA)), N,N,N',N'- tetramethylethylenediamine (TEMED) and azoisobutyronitril (AIBN) as an internal polymerization initiator in a mixture of 1 -dodecanol and cyclohexanol;- Adding sequentially the polymerization initiating composition to the dispersion medium, at a temperature from about 65-75°C under stirring at a speed of 80-90 rpm and, then the reaction mixture;- Leaving the mixture at a temperature about 65-75°C under stirring at a speed of 80-90 rpm to let polymerization process to proceed until completion (e.g. for about 90-120 min);- Isolating the obtained polymer from the reaction mixture by filtration or by sedimentation (precipitation) of the resulting polymer product followed by treatment with distilled water to separate the low molecular weight fraction and auxiliary components.

2. A method according to claim 1, wherein the polymerization initiating composition comprises 0.35-1 (wt.%) APS or KPS.

3. A method according to claim 1 wherein the reaction mixture comprises 17-20 (wt.%) HEMA in dispersed phase.

4. A method according to any one of the preceding claims wherein, the reaction mixture comprises 0.4-0.7 (wt.%) EGDMA in dispersed phase.

5. A method according to any one of the preceding claims wherein, the reaction mixture comprises 1.4-2 (wt.%) N,N,N',N' -tetramethylethylenediamine (TEMED) in dispersed phase.

6. A method according to any one of the preceding claims wherein, the reaction mixture comprises 0.1-0.15 (wt.%) of azoisobutyronitril (AIBN) in dispersed phase.

7. A method according to any one of the preceding claims wherein, the reaction mixture (dispersed phase) comprises a mixture of 1-dodecanol of 1.7-1.9 (wt.%) and cyclohexanol 24-26 (wt.%).

8. A method for the preparation of cross-linked PHEMA particles of cylindrical shape, said method comprising the following steps:- providing a polymerization composition prepared by mixing 2 -hydroxy ethylmethacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), N,N,N',N'- tetramethylethylenediamine (TEMED), ammonium persulfate (APS) in distilled water under stirring;- placing the polymerization composition in tubes (capillaries) made of sterile glass or an inert such as polyether ether ketone (PEEK);- Leaving the polymerization composition at room temperature to let polymerization process to proceed for 30-40 minutes at room temperature;- removing the polymer from the tubes to isolate polymer threads having a diameter from 0.5 mm to 10 to 150 mm the length;- subjecting the isolated polymer threads to a washing step with water to remove low molecular weight impurities.

9. A method of claim 8, wherein the composition comprises 0.35-0.45 (wt.%) AP.

10. A method of claim 8 or 9, wherein the composition comprises (wt.%): 1.4-2 (wt.%) EGDMA as a crosslinking agent11. A method of claim 8 or 9, wherein the composition comprises (wt.%): 32-34 (wt.%) HEMA.

12. A method of any one of claims 8 to 11, wherein the polymerization composition comprises (wt.%): HEMA - 32.9-33.8, EGDMA - 1.43-2.0, TEMED - 2.05-2.14, APS - 0.39-0.42, the rest being water.

13. The method according to any of claims 1-7, in which the total content of the components of the polymerization mixture are the following:

14. A method according to any one of claims 8 to 12, wherein the polymerization mixture is the following:

15. A cross-linked HEMA particle obtainable from a method according to any one of the preceding claims.

16. A cross-linked HEMA particle having a porosity from about 76% to about 85% and a compressibility from 20% about to about 30% and have a size from about 100 to about 1’200 pm for spherical shape, and for cylindrical particles from 0.5 to 1.0 mm.

17. A method for the ex-vivo preparation of an embolization system comprising an active water-soluble agent, said method comprising:- Providing at least one cross-linked poly HEMA particle according to claims 15 or 16;Contacting said at least one cross-linked poly HEMA particle with said water soluble active agent in an aqueous solution;Incubating the obtained mixture with said active agent to reach dynamic equilibrium of absorption (at least for 1 hour);Isolating the particle impregnated with the active agent.

18. An embolization system comprising at least one cross-linked poly HEMA according to claim 15or 16 or obtainable from a method of claim 17.

19. An embolization system according to claim 18, wherein said system further comprises an- anticancer agent loaded on the particle through physical interaction without the formation of chemical bonds20. An embolization system according to claim 18 or 19 for use in the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization.

21. A method for the treatment or prevention of a bleeding disorder, vascular embolization, in particular chemoembolization in a subject in need thereof, said method comprising placing at least one cross-linked poly HEMA particle according to claims 15 or 16 or an embolization system according to claims 18 to 19 into an artery of said subject.

22. A method for the treatment or prevention of a bleeding disorder, for vascular embolization, in particular chemoembolization in a patient in need thereof, said method comprising placing at least one cylindrical embolization system according to claim 15 or 16 in a collateral vessel and at least one spherical embolization system claims 18 to 19 in a main target vessel for achieving both conventional embolization and targeted delivery of active water-soluble agents to the side of implantation of the spherical and cylindrical embolization systems in said subject.

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