Method of forming spherical crosslinked microbeads

Abstract

To provide a material for embolic arterial intervention (embolotherapy or arterial embolotherapy) and a method for preparing the material.SOLUTION: Radiopaque, bioresorbable spherical microparticles for embolization or vascular occlusion therapy are provided which comprise a copolymer of an iodo-containing, halogenated phenyl-containing unit, such as an iodinated desaminotyrosine derivative, and a rubbery component such as polyethylene glycol (PEG), polycaprolactone (PCL), polytetramethylene oxide (PTMO) or polytrimethylene carbonate (PTMC). The provided microbeads can further contain or be coated with a therapeutic agent, such as paclitaxel, for targeted delivery of the therapeutic agent.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] [Incorporation by reference of priority application] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 734,067, filed August 20, 2018, and U.S. Provisional Application No. 62 / 767,293, filed November 14, 2018, which are incorporated herein by reference in their entireties.

[0002] background Field Embodiments of the present disclosure relate to methods, materials, and devices for embolic arterial intervention in general, and more particularly, to methods and devices for time-controlled embolic occlusion of blood circulation in target tissue with radiopaque bioresorbable microspheres. [Background technology]

[0003] Embolization therapy devices and reagents include metal embolic coils, plugs, gelfoam, polymeric glues, sponges, detachable balloons, oils, alcohols, and particulate polymeric embolic agents, which may be used, for example, to control bleeding, prevent blood loss before or during surgical procedures, and restrict or block the blood supply to tumors, vascular malformations, or other tissue sites.

[0004] Over the past decade, significant improvements have been made in the development of therapeutic arterial embolization therapy, particularly in the use of spherical microparticles or beads.

[0005] Particulate embolic agents such as microspheres can be used as minimally invasive procedures to restrict or block blood supply, for example, by delivering embolic particles through a guide catheter inserted into a blood vessel under X-ray guidance to guide their deployment to a target site, such as a potential tumor or vascular malformation. Examples include uterine fibroids, cancerous tumors (i.e., hepatocellular carcinoma or HCC), bleeding (e.g., during trauma accompanied by bleeding), and arteriovenous malformations (AVMs), fistulas, and aneurysms. Particles used in clinical applications are typically suspended in a radiopaque contrast solution and delivered through a vascular catheter via a syringe.

[0006] Spherical microparticles (the terms "spherical microparticles," "spherical microbeads," and simply "microbeads" are generally used interchangeably herein) have often been advantageous for tumor embolization because they can offer more precise and uniform size, better location control, and the ability for distal microcatheter delivery for deeper penetration into the vasculature. Spherical microparticles minimize the drawbacks of other embolic devices, such as vessel perforation, shrinkage of embolic material, particle fragmentation, and downstream release from sponges, gels, and adhesives.

[0007] Transcatheter arterial chemoembolization (TACE) is a method in which embolic particles or beads carry chemotherapy drugs that are released following particle application to restrict the blood supply to a target tissue, such as a tumor. Thus, the particles can cut off the blood supply and induce cytotoxicity to attack the tumor.

[0008] Radiopaque embolic beads have the potential distinct advantage of being visible under X-ray during and after the embolization procedure. During the procedure, visualization of the particulate matter allows physicians to influence precise delivery to the target vessel or tissue and prevent particles from becoming resident in unintended locations. Once the radiopaque particles are implanted, follow-up can be limited to non-interventional methods, such as simple X-rays. For example, in the case of tumors, radiopaque emboli can be tracked in size, as they have been shown to converge as their mass / volume decreases over time.

[0009] Bioabsorbable embolic particles, beads, or microspheres have the potential advantage of being temporary, effectively removing the particulate foreign material over time, allowing the surrounding tissue to return to an unaffected state. Bioabsorbable embolic particles also allow for retreatment at the initial embolization site, helping to minimize collateral revascularization.

[0010] Many spherical embolic particles have been developed for various transcatheter arterial embolization indications. Currently, various types of embolic microsphere products are available on the market, including Merit Medical's Embosphere® and HepaSphere / QuadraSphere®, BTG International's Bead Block®, LC Bead®, LC Bead LUMI®, DC Bead®, and DC Bead LUMI®, Boston Scientific's Contour SE® and Embozene™, and Terumo's HydroPearl® and LifePearl®. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 8,617,132 [Patent Document 2] U.S. Patent No. 6,284,862 [Patent Document 3] U.S. Patent No. 6,475,477 [Patent Document 4] U.S. Patent No. 8,685,367 [Patent Document 5] U.S. Patent No. 7,473,417 [Patent Document 6] U.S. Patent No. 8,008,528 [Patent Document 7] U.S. Patent No. 8,461,289 [Patent Document 8] U.S. Patent No. 8,551,511 [Patent Document 9] U.S. Patent No. 8,252,887 [Patent Document 10] U.S. Patent No. 8,415,449 [Patent Document 11] U.S. Patent No. 9,080,015 [Patent Document 12] U.S. Patent No. 8,765,161 [Patent Document 13] U.S. Patent No. 9,605,112 [Patent Document 14] U.S. Patent No. 8,883,861 [Patent Document 15] U.S. Patent No. 9,416,090 [Patent Document 16] US Patent Application Publication No. 2015 / 0045,451 [Patent Document 17] US Patent Application Publication No. 2016 / 0177,028 [Non-patent literature]

[0012] [Non-Patent Document 1] Public Health Service Act (42 USC 262(a)), per Section 351(a) Summary of the Invention [Problem to be solved by the invention]

[0013] Spherical microbeads have been developed in a variety of sizes (1–1200 μm), internal structures (solid, porous, encapsulated), and surface morphologies (smooth, rough, intentionally extended). For example, U.S. Patent No. 8,617,132 (Golzarian et al.) discloses embolic microspheres containing carboxymethyl chitosan crosslinked with carboxymethyl cellulose. The range of functionality of commercially available microbeads also includes biodegradability [1, 2, 3], drug loading and drug elution capacity [4, 5], and X-ray visibility [6–8], although not all are present in the same product.

[0014] However, there remain limitations to the functionality available in any single embolic microbead or microsphere, limiting its applications. Currently, no spherical microbeads exist that combine the properties of radiopacity, degradability, drug and / or biological agent delivery capability and deliverability in a single microbead. [Means for solving the problem]

[0015] overview Microbeads have several parameters that significantly influence their functional behavior. Many of these parameters are interrelated and are primarily determined by the composition of the polymeric material. The most important parameters are radiopacity, biodegradability, ease of physical handling, buoyancy, optimized mechanical behavior (compressibility and recovery), hydrodynamics, and occlusion behavior.

[0016] As shown herein, embodiments of the present disclosure address these needs and provide spherical microbeads that combine the properties of radiopacity, degradability, drug and / or biological agent delivery capability and deliverability in a single microbead.

[0017] As provided herein, embodiments of the present disclosure include microbeads comprising a porous polymeric material. Embodiments include generally spherical microbeads comprising a porous, inherently radiopaque, bioabsorbable polymeric material.

[0018] As provided herein, embodiments of the present disclosure include microbeads containing a therapeutic or other drug content. Embodiments include both porous and non-porous microbeads containing a therapeutic or other drug content.

[0019] Some embodiments of the present disclosure relate to embolic spherical microparticles comprising a copolymer material having at least one radiopaque iodine-containing component and at least one rubber component, wherein the rubber component comprises a polymeric material having a Tg below the physiological temperature of about 37°C, the rubber component comprising an oligomer of PEG, PCL, PTMO, PTMC, or a combination thereof, and the radiopaque component comprises a halogenated phenyl-containing monomer or oligomer unit. In some embodiments, the microparticles have internal and / or external porosity. In some further embodiments, the microparticles are radiopaque and biodegradable.

[0020] In some embodiments of the embolic spherical microparticles described herein, the copolymer material comprises monomeric or oligomeric units linked by two or more different chemical bonds having different affinities for hydrolysis, such that the different chemical bonds have different rates of in vivo hydrolysis. In some such embodiments, the hydrolysis rate of the copolymer material is controlled by the relative amounts of fast-degrading chemical bonds and slow-degrading chemical bonds. In some embodiments, the ratio of fast-degrading chemical bonds to slow-degrading chemical bonds ranges from about 100:1 to about 1:100, from about 5:95 to about 95:5, from about 10:90 to about 90:10, from about 20:80 to about 80:20, from about 30:70 to about 70:30, from about 40:60 to about 60:40, or about 50:50. In some such embodiments, the in vivo dissolution or degradation of the microparticles ranges from one minute to several years.

[0021] In some embodiments of the embolic spherical microparticles described herein, the ratio of radiopaque iodine-containing component to rubber component is about 10:1 to about 1:10, about 9:1 to about 1:9, about 8:1 to about 1:8, 7:1 to about 1:7, about 6:1 to about 1:6, about 5:1 to about 1:5, about 4:1 to about 1:4, about 3:1 to about 1:3, about 2:1 to about 1:2, or about 1:1.

[0022] In some embodiments, the copolymer comprises more than one rubber component having different hydrophilicity and different affinities for swelling in water or biologically relevant liquid media, and the ratio between two different rubber components having different hydrophilicity / swelling capabilities ranges from about 100:1 to about 1:100, from about 5:95 to about 95:5, from about 10:90 to about 90:10, from about 20:80 to about 80:20, from about 30:70 to about 70:30, from about 40:60 to about 60:40, or about 50:50. In some such embodiments, hydration of the microparticles to about 80-90% of full hydration occurs within 1-3 minutes after contact with the liquid aqueous medium. In some embodiments, the copolymer comprises more than one rubber component having different hydrolysis rates, and the ratio of the fast-degrading rubber component to the slow-degrading rubber component ranges from about 100:1 to 1:100, from about 5:95 to about 95:5, from about 10:90 to about 90:10, from about 20:80 to about 80:20, from about 30:70 to about 70:30, from about 40:60 to about 60:40, or about 50:50.

[0023] In some embodiments of the embolic spherical microparticles described herein, the microparticles have internal and / or external porosity. In some such embodiments, the porosity is created after microparticle formation by the decomposition of fast-degrading chemical bonds and the resulting release of volatile substances or gases. In some further embodiments, the volatile substances or gases form pores and / or "escape" channels. In one embodiment, the volatile substance or gas is carbon dioxide. In some other embodiments, the porosity is created by the incorporation of one or more porogen materials during microparticle formation and the subsequent expulsion of the porogens from the formed microparticles.

[0024] In some embodiments of the embolic spherical microparticles described herein, the microparticles are highly compressible. In some embodiments, the microparticles have high resilience. In some such embodiments, the microparticles are capable of returning to their original shape and size, or to about 90% to 100% of their original diameter or size. In some such embodiments, the original state may refer to the "dry" state of the microparticles prior to contact with a liquid or aqueous environment. In some other embodiments, the original state refers to the "hydrated" state of the microparticles after contact with a liquid or aqueous environment.

[0025] In some embodiments of the embolic spherical microparticles described herein, the rubber component of the copolymer material comprises one or more oligomers or macromers of PEG, PCL, PTMO, PTMC, or combinations thereof.

[0026] In some embodiments, the radiopaque iodine-containing component comprises one or more monomers, oligomers, and / or macromers of I2DTE, I2DAT, PrD-diI2DAT, or combinations thereof. In some further embodiments, the radiopaque iodine-containing component comprises a repeating unit having the following structure:

[0027] [ka] wherein n is an integer from 1 to 18. In one embodiment, the radiopaque iodine-containing component comprises PrD-diI2DAT.

[0028] In some embodiments, the microparticles comprise a blend of at least two different constituent copolymers, each of which comprises a polymer backbone having a predetermined amount of carbonate linkages and a predetermined amount of oxalate linkages, and the amount of oxalate linkages relative to the amount of carbonate linkages differs substantially such that one of the two constituent copolymers hydrolyzes in vivo at a faster rate than the other constituent copolymer, resulting in multiple step or phased degradation of the microparticles.

[0029] In some embodiments, the microparticles further comprise one or more therapeutic agents. In some such embodiments, the microparticles are configured to deliver and achieve controlled release of the one or more therapeutic agents. In some further embodiments, the one or more therapeutic agents are selected from the group consisting of cisplatin, doxorubicin, cyclophosphamide, paclitaxel, oxaliplatin, 5-fluorouracil, nivolumab / pembrolizumab, ipilimumab, interleukin-2, and combinations and analogs thereof. In some further embodiments, the therapeutic agent is dispersed in the pores of the microparticle. In other embodiments, the therapeutic agent is encapsulated in the microparticle. In further embodiments, the microparticles are prepared by precipitation from a solution containing the copolymer material and the therapeutic agent.

[0030] Further embodiments of the present disclosure relate to embolic suspensions comprising a solution or solvent and the embolic spherical microparticles described herein suspended in the solution or solvent, wherein the microparticles are hydrated and have diameters ranging from about 40 μm to about 2000 μm, about 50 μm to about 1500 μm, about 60 μm to about 1000 μm, about 70 μm to about 900 μm, about 80 μm to about 800 μm, about 90 μm to about 700 μm, or about 100 μm to about 600 μm. In some embodiments, the suspension further comprises a contrast agent and saline. In some such embodiments, the contrast agent and saline are in a ratio of about 10:90 to about 90:10, about 20:80 to about 80:20, about 30:70 to about 70:30, about 40:60 to about 60:40, or about 50:50.

[0031] Further embodiments herein relate to methods for preparing copolymer raw materials for inclusion in embolic microparticles, comprising conducting a condensation polymerization of at least two different prepolymer components, wherein the condensation polymerization is achieved by the addition of at least two different coupling agents, and the addition of the at least two different coupling agents results in the formation of chemical bonds having different affinities for hydrolysis and / or thermal degradation along the copolymer chain of the copolymer raw materials. In some embodiments, the addition of the at least two different coupling agents is conducted simultaneously. In such embodiments, the condensation polymerization results in the formation of a relatively uniform distribution of fast-hydrolyzable and slow-hydrolyzable chemical bonds along the copolymer chain. In other embodiments, the addition of the at least two different coupling agents is conducted sequentially or sequentially. In such embodiments, the condensation polymerization results in the formation of blocks having fast-hydrolyzable and slow-hydrolyzable chemical bonds along the copolymer chain. In other embodiments, the addition of the at least two different coupling agents comprises alternating addition of the different coupling agents in multiple subportions. In such embodiments, the condensation polymerization results in the formation of relatively small blocks of fast-hydrolyzable and slow-hydrolyzable chemical bonds along the copolymer chain. In some embodiments, the different coupling agents include at least one of oxalyl chloride and triphosgene (TP).

[0032] Further embodiments herein relate to methods for preparing porous spherical microbeads, comprising providing a polymeric material prepared according to the methods described herein, dissolving the polymeric material in a suitable solvent, and flowing the polymer-containing solvent into a receiving solution to form microbeads, wherein volatile gases are generated by simultaneous partial decomposition of highly hydrolyzable chemical bonds within the polymeric material, resulting in the formation of internal pores within the microbeads. In some embodiments, the volatile gases escaping from the microbeads create open pores and / or external porosity. In some embodiments, the formation of microbeads from a copolymer solution occurs simultaneously with the partial decomposition of thermally labile chemical bonds within the microbeads, resulting in internal and / or external porosity of the microbeads.

[0033] A further embodiment relates to a method of forming spherical crosslinked microbeads, comprising the steps of including (hydroxyethyl) methacrylate (HEMA) in a polymer composition, adding a free radical initiator to a solution of the polymer, forming microbeads from the polymer solution such that the free radical initiator diffuses into the microbeads, and initiating polymer crosslinking. In some embodiments, the polymer crosslinking is initiated by the application of heat.

[0034] Further embodiments relate to embolic spherical microparticles comprising a blend of at least two different constituent copolymers, either or both of which are prepared according to the methods described herein, and coupling agents selected such that the two constituent copolymers substantially differ in their relative content of chemical bonds formed by the two different coupling agents, such that one of the two constituent copolymers undergoes in vivo hydrolysis at a faster rate than the other constituent copolymer, resulting in multi-stage or stepwise degradation. In some embodiments, the microparticles further comprise at least one therapeutic agent and are configured to release the therapeutic agent during in vivo degradation of the copolymer, the release being substantially tailored with multi-stage or stepwise degradation. [Brief explanation of the drawings]

[0035] BRIEF DESCRIPTION OF THE DRAWINGS The above and other features of the embodiments set forth herein are described below with reference to the drawings of the embodiments, which are intended to illustrate but not limit the embodiments.

[0036] [Figure 1] FIG. 1 shows a generalized reaction scheme for the condensation polymerization of two monomers A and B (e.g., PrD-diI2DAT and PEG) with triphosgene (TP). [Figure 2] FIG. 2 shows the chemical structure of an exemplary generalized copolymer having a mixture of carbonate and oxalate linkages. [Figure 3] Figure 3 shows SEM images of highly porous radiopaque biodegradable microspheres made from 40%PrD-diI2DAT-co-40%PEG400-co-20%PCL1.25k copolymers with a carbonate to oxalate linkage ratio of 75% to 25%. [Figure 4] FIG. 4 is an SEM image of an exemplary embodiment of a spherical dry embolization microparticle covered with a mannitol coating. [Figure 5] 5A and 5B are SEM images of an exemplary embodiment of a spherical, fully hydrated, non-porous embolization-forming microparticle at two different magnifications. [Figure 6] FIG. 6 is an SEM image of a further exemplary embodiment of a spherical, dry embolization porous microparticle (covered with a mannitol coating). [Figure 7] 7A and 7B are SEM images of a further exemplary embodiment of a spherical, fully hydrated, porous, embolization-forming microparticle at two different magnifications. [Figure 8] Figure 8 shows the compression and size recovery of individual microbeads in the DMA stress relaxation mode test. [Figure 9]Figures 9A-9B show copolymer microbeads prepared from 50% PrDI2FD-co-30% PEGlk-20% PCL1.25k copolymer with a carbonate to oxalate linkage ratio of 75% to 25% and doxorubicin-loaded. Figure 9A shows the microbeads before loading with the drug doxorubicin (DOX); and Figure 9B shows the microbeads fully loaded with DOX. [Figure 10] FIG. 10 shows microbeads made by precipitation of crystalline paclitaxel as a mixture in a copolymer material. [Figure 11] FIG. 11 shows a reaction scheme for making an embodiment of a microbead comprising a cross-linked polymer. [Figure 12] 12A and 12B show the biodegradation patterns of some specific non-limiting exemplary formulas of microspheres including copolymers and copolymer blends achieving multiphasic drug elution patterns. [Figure 13] FIG. 13 shows DOX-loaded microbeads prepared from 50% PrDI2FD-co-50% PEGlk copolymer with 100% carbonate linkages by encapsulation of DOX suspension in organic solvent. DETAILED DESCRIPTION OF THE INVENTION

[0037] Detailed Description According to aspects of the present disclosure, certain embodiments are embolic spherical radiopaque microparticles comprised of a copolymer material synthesized from at least one radiopaque iodine-containing component and at least one rubber component, the combination of which in the resulting polymer provides a combination of desirable properties.

[0038] The radiopaque component may include halogenated phenyl-containing monomeric or oligomeric units as described above. Preferably, the halogen content is entirely or primarily iodine. According to aspects of the present disclosure, certain embodiments include copolymers containing diester units of 1,3-propanediol with diiodinated-desaminotyrosine. Other embodiments include diesters of other diols with diiodinated-desaminotyrosine, such as ethylene glycol, butyl diol, alkyl diols, and generally oligomers of polyethylene glycol (PEG).

[0039] The rubber component may comprise a polymeric material having a Tg (glass transition temperature) below physiological temperature of about 37°C to provide flexibility and resilience during and after implantation in the vasculature. For example, the rubber component of the copolymer material may comprise oligomeric units of PEG, polycaprolactone (PCL), poly(tetramethylene oxide) (PTMO), poly(trimethylene carbonate) (PTMC), or combinations thereof. More than one rubber component may be used to tailor the properties of the copolymer, such as biodegradation, "stickiness," resilience, etc.

[0040] definition The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. All patents, applications, published applications, and other publications cited herein are incorporated by reference in their entirety unless otherwise stated. In the event of multiple definitions of terms herein, those in this section are controlling unless expressly stated otherwise. As used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Conventional methods of mass spectroscopy, NMR, HPLC, protein chemistry, biochemistry, recombinant DNA technology, and pharmacology are employed unless otherwise indicated. The use of "or" or "and" means "and / or" unless otherwise indicated. Furthermore, the use of "including," as well as other forms such as "include," "includes," and "included," is not limiting. As used herein, the terms "comprise(s)" and "comprising," whether in transitional phrases or the body of a claim, should be construed as having an open-ended meaning. That is, the term should be interpreted synonymously with the phrases "having at least" or "including at least." When used in the context of a process, the term "comprising" means that the process includes at least the recited steps, but may include additional steps. When used in the context of a compound, composition, or device, the term "comprising" means that the compound, composition, or device includes at least the recited features or components, but may also include additional features or components.

[0042] While the present disclosure has been described in detail in the foregoing description, such description is illustrative and not restrictive. The present disclosure is not limited to the disclosed embodiments. Variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed disclosure, from a study of the specification and the appended claims.

[0043] All references cited herein are incorporated herein by reference in their entirety. In the event that the publications and patents or patent applications incorporated by reference conflict with the disclosure contained in the specification, the specification is intended to supersede and / or control for such conflicting material.

[0044] Unless otherwise defined, all terms (including technical and scientific terms) shall be given their ordinary and customary meaning to those skilled in the art and shall not be limited to any special or customized meaning unless expressly defined herein. It should be noted that the use of a particular term in describing a particular feature or aspect of the specification should not mean that the term is being redefined herein to include any particular characteristic of the feature or aspect of the disclosure to which the term pertains.

[0045] Where a range of values ​​is provided, it is understood that the upper and lower limits of the range, and each intervening value between the upper and lower limits of the range, are encompassed within the embodiments.

[0046] radiopaque The radiopacity of the microbead embodiments is provided by the incorporation of one or more halogen-containing monomers. The radiopacity of the microbeads can be adjusted by varying the amount of radiopaque component in the copolymer. As discussed above, the radiopacity of the microbeads of the present disclosure allows for precise positioning of the beads at the target location and allows for determination of the "end point" of embolization.

[0047] The radiopaque component comprises a monomer or macromer containing a halogen-substituted phenyl ring, which acts as a radiopaque entity when incorporated into the polymeric structure of the microsphere or bead. Typically, such halogen-substituted phenyl rings contribute to the rigidity of the copolymer material and may be referred to herein as the "rigid" component.

[0048] In a preferred embodiment, the halogen is iodine. Many suitable halogenated phenolic components are described in the following U.S. patents and published U.S. patent applications: U.S. Pat. No. 6,284,862; U.S. Pat. No. 6,475,477; U.S. Pat. No. 8,685,367; U.S. Pat. No. 7,473,417; U.S. Pat. No. 8,008,528; U.S. Pat. No. 8,461,289; U.S. Pat. No. 8,551,511; U.S. Pat. No. 8,252,887; U.S. Pat. No. 8,415,449; U.S. Pat. No. 9,080,015; U.S. Pat. No. 8,765,161; U.S. Pat. No. 9,605,112; U.S. Pat. No. 8,883,861; U.S. Pat. No. 9,416,090; U.S. Patent Application Publication No. 2015 / 0045,451; and U.S. Patent Application Publication No. 2016 / 0177,028.

[0049] For example, U.S. Patent No. 9,416,090 (among others) describes monomers and polymers containing desaminotyrosyltyrosine ethyl ester, commonly abbreviated as DTE. DTE can be halogen-substituted at various positions and to various degrees. An example of a diiodinated DTE variant is shown below, abbreviated as I2DTE. (There are several possible variants of iodine substitution, for example, 1-4 substitutions at different positions according to U.S. Patent No. 9,416,090.)

[0050] [ka]

[0051] In another example, U.S. Pat. No. 8,252,887 discloses alkyl linking units (CH2) n (where n is an integer from 1 to 18) is described.

[0052] [ka]

[0053] In a preferred embodiment, n=3 and the linking unit is 1,3-propanediol, so the monomer is the diester of 1,3-propanediol ("PrD") with I2DAT. This compound (and related polymeric forms) is referred to herein as "PrD-diI2DAT."

[0054] Copolymer elastomer component Certain microbead embodiments having aspects of the present disclosure comprise a copolymer composed of at least two different biodegradable components—a radiopaque component based on halogen-containing monomers and an elastomeric component having a glass transition temperature below physiological temperatures (below about 37° C.), which may also be referred to as a “rubber component,” a “soft component,” or the like.

[0055] The elastomeric component can include one or more monomeric or oligomeric species. For example, in some embodiments, the elastomeric phase can include polyethylene glycol (PEG) units, among others.

[0056] [ka]

[0057] The molecular weight (MW) of a PEG unit depends on the value of "n," which is selected based on the desired properties. For example, an elastic component may contain repeating PEG units with a range of molecular weights characterized by the average and range of "n." PEG oligomers are commercially available in several sizes or MW ranges. For example, Sigma-Aldrich (now Millipol Sigma) markets PEG materials or solutions with molecular weights ranging from about 200 to about 50,000 g / mol.

[0058] Other materials such as oligomeric polycaprolactone (PCL), poly(tetramethylene oxide) (PTMO), poly(trimethylene carbonate) (PTMC), or combinations thereof can be used in place of or in combination with PEG for inclusion in the elastomeric component.

[0059] Materials incorporating fast-degrading chemical bonds In some instances, embodiments described herein include chemical bonds that have different affinities for hydrolysis and / or thermal degradation at bonds along the copolymer chains of the copolymer material, and such differences can affect some different properties of embodiments of the copolymer material of the present disclosure.

[0060] In certain embodiments, the effect of such rapidly degrading bonds can be complementary and useful for medical devices such as embolic microspheres or microbeads. In some embodiments, such rapidly degrading bonds may include other relatively stable linking bonds to link monomeric or oligomeric components of copolymer materials (e.g., linking radiopaque and / or elastomeric components).

[0061] In exemplary embodiments described below, the rapidly degradable linkages may be oxalyl ester linkages, which may be incorporated in conjunction with carbonate linkages, which are relatively stable under conditions of hydrolysis and / or pyrolysis. In certain embodiments for producing copolymer materials, reagents such as triphosgene (TP) and oxalyl chloride may be used as reactants in creating the linkages in the copolymer chains.

[0062] In one embodiment of a copolymer composition having a mixture of carbonate and oxalate linkages, which can be used as a component in making the microbead embodiments herein, the portion of the oxalate linkages can be selected to tailor both the in vivo degradation characteristics of the microbeads and to induce a desired porosity during formation of the microbeads.

[0063] Additionally, polymers containing rapidly degradable linkages can be blended with polymers having more stable carbonate linkages when making the microbead embodiments herein, whereby the portion of the oxalate linkages can be selected to tailor both the in vivo degradation characteristics of the microbeads and to induce the desired porosity during microbead formation.

[0064] Tunable degradation rate due to polymeric bond type The degradation of microbead embodiments of the present disclosure can be tuned from hours to months or years, depending in large part on the amount of fast-degrading chemical bonds incorporated. In certain embodiments, the monomer units of the copolymer are linked by at least two different types of chemical bonds that have different degrees of susceptibility to hydrolysis and thermal degradation.

[0065] In some embodiments, the monomer units of the copolymer are linked by relatively slow decomposing carbonate bonds created by a condensation reaction with phosgene as the coupling agent.

[0066] [ka]

[0067] The resulting carbonate linkages in the copolymer chains are relatively unreactive to hydrolysis under physiological conditions (e.g., in vivo). For example, Figure 1 illustrates a reaction scheme for an example carbonate copolymer prepared using triphosgene (TP) as a reactant (see, e.g., Example 1).

[0068] In some embodiments, the comprising monomeric units are linked by oxalyl ester chemical bonds formed by a polycondensation reaction with oxalyl chloride as a coupling agent reactant (see, e.g., Example 2).

[0069] [ka]

[0070] Oxalyl ester bonds are more susceptible to hydrolysis than carbonate bonds under physiological conditions (e.g., in vivo) to facilitate biodegradation of the copolymer chains. For example, Figure 2 shows a generalized copolymer with a mixture of oxalyl and carbonate linkages.

[0071] Due to the polycondensation nature of the polymerization reaction, the addition of multiple coupling agents can be varied in different ways (e.g., by simultaneous, sequential, and / or alternating addition) to result in the incorporation of different chemical bonds into the same copolymer macromolecule, as described in detail in Examples 3-5 below.

[0072] Microbead porosity In some embodiments, the porosity of the microheads can be adjusted by varying the composition and bead formation conditions. Microbeads can be prepared to have no porosity or to have substantial internal porosity. Specific preparations are described in Examples 7 and 8 below.

[0073] Similarly, microbeads may be prepared with internal porosity that extends to the particle surface. This property may be referred to herein as having internal and / or internal / external porosity. For example, see the highly porous microbeads shown in Figure 3.

[0074] In one embodiment, the internal porosity of the microbeads is introduced by creating channels through carbon dioxide that forms during hydrolysis of the oxalyl ester chemical bonds. Alternatively, porous microbead embodiments can be made by traditional methods for making porous materials, such as the porogen material leaching method, in which a porogen material (salt, DMSO, ice particles, etc.) is incorporated into the beads during bead formation and later removed, leaving behind negative replica pores.

[0075] Density and buoyancy of radiopaque materials The introduction of some porosity is particularly useful for radiopaque microbeads having aspects of the present disclosure because the inclusion of iodine in the polymer formulation increases its density. The introduction of porosity substantially increases the buoyancy of the microbeads, and therefore, the introduction of porosity into the microbeads can be used to offset the density effect of iodine. Balanced buoyancy improves the deliverability of the microbeads and helps to avoid rapid settling.

[0076] Hydration and swelling of microbeads Microbead embodiments of the present disclosure can be manufactured in a dry state to delay response to aqueous fluids. Upon contact with water, a contrast, or a water-control solution, the microbeads can be configured to rapidly absorb water and swell. After an initial rapid swelling period (1-3 minutes), the density of the microparticles, particularly for porous beads, becomes substantially lower than the density of the dry beads. For example, exemplary microbeads are shown in their dry (Figures 4 and 6) and hydrated (Figures 5A, 5B, 7A, and 7B) forms.

[0077] The solvated microparticles have a substantially reduced tendency to interact and aggregate with one another, and they form a suspension in solution with a sedimentation rate that allows the hydrated microbeads to be delivered by passage through a microcatheter with an appropriate lumen size. After the microbeads are placed at the site of occlusion, several small microbeads expand. This additional small expansion of the microbeads creates pressure against the vessel wall, and the embolization microparticles are thus able to conform to the cross-section of the vessel.

[0078] Certain embodiments of the microbeads may comprise multiple rubber components, with the different rubber components comprising copolymer materials having different hydrophilicities and different affinities for swelling in water or biologically relevant liquid media. The relative amount of hydrophobic to hydrophilic components has a substantial effect on the swelling of the beads, their buoyancy, and mechanical properties. The ratio between rubber components with different hydrophilic / swelling capacities may be between 100:0 and 0:100.

[0079] Size and size distribution The embolic materials of the present disclosure may be formed into dry microspheres ranging in diameter from 30 μm to approximately 1500 μm. Different applications require beads of various sizes, depending on the anatomical structure. Microsphere size is crucial for anatomical compatibility, fluid dynamics, deliverability, and occlusion level. Microbeads of the present disclosure can be manufactured in narrow or broad size ranges. Smaller microspheres typically penetrate deeper into blood vessels, while larger sized microspheres have a greater chance of occluding the vessel and preventing penetration of smaller beads. For example, Figures 3 through 7A-7B present scaled images of some embodiments described herein.

[0080] Compressibility and resilience Microbead compressibility and resilience is crucial to the delivery technique, as the microbeads are compressed during movement through the microcatheter, but quickly recover to their original size after injection from the catheter.

[0081] In some embodiments, the compressibility and resilience is adjusted by the amount of rubber component in the copolymer composition. In some other embodiments, the compressibility and resilience is controlled by the molecular weight of the rubber component, the molecular weight of the copolymer material synthesized, or the presence of porosity.

[0082] In some embodiments, the hydrated microbeads are compressible from their original hydrated spherical shape to a substantially deformed elongated cylindrical shape and then can return to their original shape. This compressibility under strain characteristic of the microbeads allows them to be compressed into a delivery catheter having a diameter smaller than that of the hydrated microbeads. resilienceThis allows the microbeads to recover to 90%-100% of their original hydration state within seconds of exiting the catheter. In some embodiments, the microparticles are highly compressible, such that the microparticles are compressible to about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or a range between any two of the aforementioned values, of their previous original size or diameter prior to application of the compressive force. In some embodiments, the microparticles have high resilience, returning to their original shape and size or to about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 100%, or a range between any two of the aforementioned values, of their original diameter after release of the compressive force. In some further embodiments, the microparticles are capable of returning to about 90%-100% of their original diameter or size. In some such embodiments, the original state can refer to the "dry" state of the microparticles prior to contact with a liquid or aqueous environment. In some other embodiments, the original state refers to the "hydrated" state of the microparticles after contact with a liquid or aqueous environment. In further embodiments, the microparticles are highly resilient in the hydrated state.

[0083] Figure 8 shows the rapid strain recovery after unloading individual beads (350 µm diameter) compressed to 80% in a DMA compression test conducted in water. In this example, the microbeads are made of poly(50% PrD-diI2DAT-co-50% PEG1K 100% carbonate).

[0084] Relative properties of microbeads Generally, increasing the % content of radiopaque components not only increases radiopacity but also increases structural stiffness and degradation time, which may decrease compressibility.

[0085] In general, increasing the percentage of oxalate linkages to carbonate linkages increases both porosity and buoyancy on the one hand, and the rate of hydrolysis on the other hand.

[0086] Microbead preparation method The present disclosure also provides a method for making spherical, radiopaque, biodegradable, compressible, recoverable microparticles with internal and external porosity, the porosity of which is created by the formation of carbon dioxide gas formed during microbead preparation by the degradation of pre-incorporated, readily hydrolyzable or thermolabile chemical bonds.

[0087] In some embodiments, microparticle porosity can also be created by incorporating porogen materials during the bead formation stage and subsequently expelling them from the already formed microbeads.

[0088] Drug content and drug delivery in microbeads In some embodiments, the radiopaque biodegradable microbeads described herein comprise at least one drug or pharmaceutical agent that can be released at the site of the embolic implant. As used herein, the term "drug" is intended broadly to encompass "therapeutic agents," as they are commonly known in medicine, as the term "drug" is not limited and can include either or both small molecule compounds and polymeric compositions or biological agents.

[0089] Common Drugs and Therapeutics According to one embodiment of the embolization therapy products and methods described herein, the polymer can be formulated with an effective amount of at least one therapeutic agent (e.g., a pharmaceutical and / or biological agent) sufficient to exert a selected therapeutic effect.

[0090] As used herein, the term "medicine" includes substances that stimulate a specific physiological (metabolic) response and are intended to alleviate, treat, or prevent disease.

[0091] The term "biological agent" as used herein encompasses any substance that has structural and / or functional activity in a biological system, including, but not limited to, organs, tissues, or cell-based derivatives, cells, viruses, vectors, nucleic acids (animal, plant, microbial, and viral) of natural and synthetic origin and of any sequence and size, antibodies, polynucleotides, oligonucleotides, cDNA, oncogenes, proteins, peptides, amino acids, lipoproteins, glycoproteins, lipids, carbohydrates, polysaccharides, lipids, liposomes, or other cellular components or organelles for receptors and ligands.

[0092] As used herein, the term "biological agent" includes any virus, serum, toxin, antitoxin, vaccine, blood, blood component or derivative, or allergenic product, or congener product, or arsphenamine or its derivatives (or any trivalent organic arsenic compound) applicable to the prevention, treatment, or cure of human disease or injury (pursuant to Section 351(a) of the Public Health Service Act (42 U.S.C. 262(a))).

[0093] Additionally, the term "biologic agent" may include: 1) "Biomolecule," as used herein, includes biologically active peptides, proteins, carbohydrates, vitamins, lipids, or nucleic acids produced and purified by naturally occurring or recombinant organisms, antibodies, tissues or cell lines, or synthetic analogs of such molecules; 2) "Genetic material," as used herein, includes nucleic acids (either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA)), genetic elements, genes, factors, alleles, operons, structural genes, regulatory genes, operator genes, gene complements, genomes, genetic codes, codons, anticodons, messenger RNA (mRNA), transfer RNA (tRNA), ribosomal extrachromosomal genetic elements, plasmagens, plasmids, transposons, genetic mutations, genetic sequences, exons, and introns; 3) "Processed biological products," as used herein, such as cells, tissues, or organs that have undergone manipulation.

[0094] The therapeutic agent may also include vitamin or mineral substances, or other natural elements.

[0095] Pre-loaded embolic microbeads and "bed-side" drug loading In some embodiments, the radiopaque, bioresorbable embolic microbeads described herein are preloaded with a drug or therapeutic agent content as delivered to the end user (e.g., a treating physician). In some embodiments, the microbeads described herein are configured to incorporate a drug or therapeutic agent at the time of use by application of the therapeutic agent by the end user (e.g., a therapeutic agent injected into the microbead embodiment by a treating professional at the so-called "bedside"). Alternatively, the embodiments also include microbeads intended to be used solely to achieve an embolic effect without the application of a drug or therapeutic agent (e.g., "plain" or "bland" microbeads).

[0096] In some embodiments, the methods shown and described herein for incorporating drugs or therapeutic agents into microbeads can be adapted for "bedside" loading, as described in Example 12 and Figures 9A-9B.

[0097] Tumor Treatment. In an important, non-limiting example, the microbeads described herein can deliver drugs for the treatment of neovascular tumors. For example, many drugs commonly used in oncology can be advantageously delivered by microbead embodiments with selected rates of biodegradation and drug release, where the inherent radiopacity of the bead copolymers aids in precise, localized delivery to the tumor while minimizing systemic effects.

[0098] In some embodiments, the radiopaque, bioresorbable embolic microbeads described herein can provide "multifaceted" therapeutic capabilities. For example, the microbeads can provide sustained localized release of two complementary therapeutic target drugs: one, a potent chemotherapeutic agent to shrink tumors, and a second, a therapeutic agent designed to stimulate the immune system to attack tumors.

[0099] In one example of a multifaceted therapeutic method using embodiments of the microbeads described herein, a mixture of two or more different microbead types can be administered to a tumor site. In this example, a first type of microbead contains one or more tumor-reducing chemotherapeutic drugs, and a second type of microbead contains an immunotherapeutic agent. Each type of microbead can have a structure and composition suitable for optimizing the therapeutic effect of its constituent drugs.

[0100] In another example of a multi-faceted therapeutic method using microbead embodiments, a single type of microbead contains both (i) a more tumor-reducing chemotherapeutic agent and (ii) an immunotherapeutic agent, and the structure and composition of the microbead embodiment are adapted to allow for effective delivery and elution timing of each therapeutic agent.

[0101] In some embodiments, the controllable or tunable biodegradability of the microbeads described herein is highly advantageous in certain drug treatment strategies, allowing for subsequent re-treatment at the original implantation site.

[0102] Another example of a multifaceted treatment method uses the controllable bioabsorption properties of the microbeads described herein to enable sequential retreatment at a tumor site for delivery of multiple therapeutic agents. For example, initial embolization treatment of a tumor may involve administration of microbeads described herein comprising a microbead structure and / or composition (in terms of elution rate and / or biodegradation rate) configured to effectively deliver a first drug or agent. Retreatment may then be performed using a second microbead embodiment comprising a second drug or agent.

[0103] Similarly, embolization of a site such as a tumor can be controlled to create a temporary ischemic state at the site without disrupting the vasculature. In some embodiments, the radiopaque bioresorbable microbeads described herein comprise compositions that not only produce biocompatible biodegradation products, but have been shown to be compatible with many drugs, avoiding denaturing or rendering the drug ineffective.

[0104] Examples of therapeutic drugs Non-limiting examples of drugs or other therapeutic agents include: A. Cisplatin - commonly used in lung cancer, ovarian cancer, carcinoma, breast cancer, brain tumors, etc. Cisplatin binds to DNA in a way that interferes with DNA replication, increasing mitochondrial oxidative stress and causing apoptosis. Cisplatin is effective regardless of the replicative state of the target cell. B. Doxorubicin - commonly used in breast cancer, lung cancer, stomach cancer, ovarian cancer, thyroid cancer, myeloma, sarcoma, etc. Doxorubicin interferes with TOPII (topoisomerase II)-mediated DNA repair, generates free radicals that damage membranes, and generally target replicating cells. C. Cyclophosphamide - Often used as an antiangiogenic agent and in combination with peptide cancer vaccines, especially for immunotherapy. Cyclophosphamide targets cells regardless of their replicative state. D. Paclitaxel - Used in breast cancer, ovarian cancer, prostate cancer, gastric cancer, non-small cell lung cancer, head and neck cancer, etc. Paclitaxel works by locking tubulin structures in place, impairing mitosis. E. Oxaliplatin - Used especially in colon and ovarian cancer, typically in combination with 5-fluorouracil. Oxaliplatin works by cross-linking DNA and proteins. F. 5-Fluorouracil (5-Fluororcil) - Used especially for colon cancer and solid tumors, it is sometimes combined with leucovorin for increased effectiveness. 5-Fluorouracil works by disrupting RNA synthesis. G. Nivolumab / pembrolizumab - An IgG4 isotype antibody that blocks the protective mechanisms of cancer cells, allowing the immune system to destroy them. It is used, among other things, in melanoma and non-small cell lung cancer. H. Ipilimumab - A monoclonal antibody that activates the immune system by targeting CTLA-4, a protein receptor that downregulates the immune system. It is a cancer immunotherapy approved for use in treating melanoma. I. Interleukin-2 (IL-2) - A biological response modifier and cytokine that stimulates the immune system to attack cancer. Used in the treatment of renal cell carcinoma and melanoma.

[0105] As an example, liver cancer, such as hepatocellular carcinoma, may generally appear as a highly vascular solid tumor. Embolic microbead embodiments can be delivered to the tumor's arterioles to block its blood supply and deliver chemotherapy drugs, such as doxorubicin. In one embodiment, the microbeads can have diameters ranging from about 100 microns to about 300 microns. The polymeric material of the microbeads is adapted to degrade predictably, releasing their drug contents over a selected period of time, e.g., about two to six months. Immunotherapeutic drugs can also be administered via the microbead embodiments described herein.

[0106] In some embodiments, the bioabsorbable microbeads of the present disclosure have properties that can enhance the effectiveness of certain drugs. For example, paclitaxel and doxorubicin are advantageously used in low doses over extended periods of time. The hydrophobic components of the copolymer embodiments described herein can interact with these drugs to act as a stable reservoir for prolonged elution at the microbead implantation site. Selectable biodegradation rates (e.g., with a mixture of carbonate and oxalyl ester linkages) can result in such extended elution.

[0107] Carbonate Bond In some embodiments, copolymer materials are synthesized by forming carbonate bonds linking either or both of the radiopaque and / or rubber subunits. This can be achieved, for example, by using triphosgene (TP) as a polymerization reactant, whereby TP acts on the carbonyl and hydroxy groups of each monomer or oligomer in the reaction mixture. Generally, the carbonate bonds in such polymer chains are relatively stable to hydrolysis under physiological conditions. In certain embodiments, the copolymer contains both PrD-diI2DAT and polyethylene glycol (PEG). Example 1 below illustrates a general method for preparing such copolymers. In this example, excess triphosgene (TP) is used as a reactant to create the carbonate bond.

[0108] Oxalate bond In some embodiments, copolymer materials are synthesized by forming oxalyl ester or oxalate linkages linking subunits of either or both the radiopaque and / or rubber components. For example, when oxalyl chloride is used as a polymerization reactant, the oxalyl chloride attacks the carbonyl and hydroxyl groups of each monomer or oligomer in the reaction mixture. Example 2 below describes a general method for preparing such copolymers. In some instances, the oxalate linkages in such polymer chains are relatively vulnerable to hydrolysis.

[0109] A mixture of carbonate and oxalate bonds In some embodiments, the polymerization scheme is configured to create a mixture of both carbonate and oxalate linkages in the copolymer chains of material forming the embolic microbeads. The details of the mixture, described below, allow for the biodegradation properties of the microbeads to be tailored and matched to therapeutic requirements.

[0110] In some other embodiments, the copolymer also contains both PrD-diI2DAT and polyethylene glycol (PEG). In these embodiments, both carbonate linkages (e.g., by addition of TP) and oxalate linkages (e.g., by addition of oxalyl chloride) are formed, thereby achieving distinct properties of the resulting copolymer. Examples 3-5 below demonstrate some methods for preparing such copolymers having both carbonate and oxalate linkages.

[0111] Condensation schemes and bond configurations for specific carbonate-oxalate synthesis In various microbead embodiments, the synthesis of the polymeric material may have one of several different timing schemes or strategies to create copolymer materials with varying placement and frequency of carbonate and oxalate linkages. Both the frequency of each linkage type (% carbonate vs. % oxalate) and the pattern or placement of carbonate and oxalate linkages along the copolymer can affect the properties of the copolymer raw material.

[0112] Figure 1 shows a generalized reaction scheme for the condensation polymerization of two monomers, A and B, with triphosgene. For example, A can be PrD-diI2DAT and B can be PEG.

[0113] FIG. 2 illustrates the chemical structure of an exemplary generalized copolymer having a mixture of carbonate and oxalate linkages.

[0114] As described below in Examples 3-5, the condensation reaction is accomplished by dissolving stoichiometric portions of triphosgene (TP) and oxalyl chloride in a suitable solvent to provide the respective reaction additives. Each of these reactant additives can then be added in a specific, desired timing pattern to a reaction mixture containing the desired precursor monomer or oligomer: (a) Simultaneous Addition (e.g., Example 3)—The triphosgene (TP) and oxalyl chloride reactant solutions are added to the reaction mixture at approximately the same time, allowing reactions with the respective precursor monomers or oligomers to proceed simultaneously. Simultaneous addition results in a relatively even distribution of faster and slower hydrolyzable chemical bonds along the copolymer chain. This even distribution of highly hydrolyzable chemical bonds results in uniform degradation of the microbeads. (b) Sequential Addition (e.g., Example 4)—One of the triphosgene (TP) and oxalyl chloride reactant solutions is selected and added to the reaction mixture first, and allowed to react until complete or near completion, after which the other is added and allowed to react. This sequential or stepwise condensation mode results in the formation of blocks with highly hydrolyzable chemical bonds, followed by blocking with slower hydrolyzable chemical bonds along the copolymer chain. The resulting blocking of the copolymer results in at least two steps of degradation of the microbeads. (c) Alternating Addition (e.g., Example 5)—A variation of the sequential scheme in which each portion of reactant solution is subdivided into the desired number of subportions (e.g., 20 subportions), and then the subportions are added alternately, with appropriate reaction time between additions, until all subportions have been added and reacted. This alternating addition of different coupling agents results in the formation of relatively small blocks of faster hydrolyzable and slower hydrolyzable chemical bonds. The alternating distribution of small blocks of highly and slowly hydrolyzable chemical bonds affects the degradation kinetics of the microbeads, allowing for tuning of the degradation rate.

[0115] In subsequent reactions, such as (a)-(c) above, the copolymer material can be purified as described in the Examples, for example, by precipitation from the reaction mixture (e.g., with IPA), followed by multiple dissolutions (e.g., into DCM) and precipitations (IPA), followed by sequential drying.

[0116] Microbead preparation The purified copolymer materials, such as those described in Examples 1-6, can be formed into microbeads by a variety of methods.

[0117] In one embodiment, the microbeads are prepared as described in Example 7. Made by This involves dissolving the polymeric material in a suitable solvent and adding the solution in a thin stream (e.g., from a syringe) to a receiving solution, with the beads forming upon collapse of the stream.

[0118] Examples 9-13 also describe methods for producing microbeads, particularly those with drug or biological agent inclusions. Made by In manufacturing, other methods, such as the Continuous Flow Beads (CFB) method, can be used to obtain uniform beads of the desired size.

[0119] Microbead porosity Embodiments of the microbeads described herein have substantial porosity that contributes to both compressibility and buoyancy, among other properties. Embodiments also include methods of making spherical, radiopaque, biodegradable, compressible, recoverable microparticles with internal and external porosity (external porosity refers to pores that open to the surface of the microbead).

[0120] Effect of the relative proportions of carbonate and oxalate linkages In embodiments, the porosity of the microbeads is created by the formation of carbon dioxide gas formed during microbead preparation by decomposition of pre-incorporated readily hydrolyzable or thermally labile chemical bonds (e.g., oxalate bonds).

[0121] In embodiments, porosity can be created during microbead formation (and / or hydration of the microbeads) by the breakdown of fast-degrading chemical bonds with the release of volatiles, such as carbon dioxide-formed pores and / or "escape" pores. Particulate porosity can also be created by the incorporation of porogen materials during the bead formation stage and their subsequent removal from the already formed microbeads.

[0122] Drug loading method using microbeads Diffusion. As described herein, embodiments of the microbeads described herein can be precipitated in a reaction that produces carbon dioxide, resulting in gas-filled pores. Depending on the reaction conditions, the pores may interconnect to create a sponge-like porosity.

[0123] As shown in Figure 3, the surface of the generally spherical microbeads contains a large proportion of open pores, thus allowing extensive communication with the interior of the bead. In this manner, the pores provide a very substantial void volume within the bead, which can act both as a storage volume for drugs or biological agents and also to modulate the buoyancy and fluidic delivery properties of the microbead.

[0124] Pre-prepared dry microbeads can be loaded with drug content by diffusion (e.g., Example 12). Drugs, drug mixtures, and / or biological agents can be suspended in a suitable solvent and diffused into the microbeads. Figures 9A-9B show microbeads loaded with the exemplary water-soluble drug doxorubicin (DOX). Figure 9A shows small clusters of pristine beads (before diffusion—light color). This contrasts with similar clustered beads in Figure 9B after DOX has diffused into the porous microbead structure when the beads are immersed in a drug solution. Figure 9B shows a close-up detail of a fully drug-loaded microbead with the deep orange color of DOX. In this non-limiting example, the microbeads are composed of a copolymer consisting of 50% PrD-diI2DAT-co-30% PEG1k, 20% PCL1.25k, with a carbonate / oxalate linkage ratio of 75% / 25%.

[0125] Drug loading by diffusion can be included as a step in manufacturing microbeads for medical use (pre-loading), or alternatively, can be performed as part of the administration procedure, allowing the drug or agent to diffuse into the beads under sterile conditions immediately prior to implantation in the body (e.g., catheter delivery to a site within the vasculature). This latter method may be particularly suitable for certain biologicals, such as perishable or sensitive drugs.

[0126] In certain embodiments, diffusion of the drug in the solvent can be followed by evaporation of the solvent to form a drug deposit with pores, and this process can be optionally repeated to increase the drug content within the microbeads.

[0127] Precipitation. In certain embodiments, the drug or agent may be stable and compatible in the solvent or mixture into which the microbead embodiment is precipitated, and the drug or agent is contained within the body of the microbead. For example, embodiments of copolymer microbeads have been prepared to have paclitaxel in solution when the microbeads are precipitated, with the paclitaxel present as crystals within the formed microbeads. Biodegradability allows for time-sustained elution of paclitaxel at the implant site.

[0128] Figure 10 is a composite image showing microbead embodiments made by precipitating crystalline paclitaxel as a mixture in a copolymer material. Example 9 describes exemplary methods for making such microbeads. These methods have demonstrated paclitaxel contents of greater than 30% by weight. The penetration of the crystalline drug to the surface of the microbeads is particularly evident in the magnified portion of the image.

[0129] In Example 10, microbeads are prepared by encapsulating rapamycin (sirolimus) into microbeads at a concentration greater than 25% by weight.

[0130] In Example 13, microbeads are prepared by encapsulating doxorubicin (DOX) from a suspension of DOX in a dichloromethane solution of the embolic copolymer. An image of microparticles with an encapsulated suspension of DOX is shown in Figure 13. This method can achieve a higher concentration of the encapsulated drug DOX than the diffusion method.

[0131] Encapsulation of biological agents in radiopaque, bioresorbable microbeads In Example 11, a biological agent is encapsulated in a microbead embodiment to demonstrate the ability of the microbeads to deliver the biological agent to tumors and other anatomical structures. In this case, the biological agent is bovine serum albumin (BSA), a suitable model for biologics and / or large molecule drugs. As previously mentioned, immunological agents (e.g., nivolumab / pembrolizumab, ipilimumab, and interleukin-2) are important in tumor treatment.

[0132] Microbeads made from potentially crosslinkable copolymer materials Microbead embodiments can include cross-linked copolymer materials. Figure 11 shows a reaction scheme for making microbead embodiments that include cross-linked polymers, whereby a copolymer is prepared having pendant groups that include potentially cross-linkable HEMA or HEMA-like cross-linking groups. Following formation of the preformed microbeads, cross-linking is induced by application of a free radical initiator.

[0133] Example 17 describes a method for producing biodegradable crosslinked microbeads by treating microbeads with a free radical initiator followed by a free radical polymerization procedure. In this embodiment, (hydroxyethyl) methacrylate or HEMA is incorporated into the polymer composition. A free radical initiator is then added to the polymer solution during the bead formation stage, resulting in the initiator diffusing into and becoming incorporated within the beads. Heat may be applied to initiate polymer crosslinking.

[0134] Microbeads containing copolymer blends Microbeads could also be fabricated from mixtures (or blends) of copolymers composed purely of carbonate linkages and copolymers composed purely of oxalate linkages. In the case of copolymer blends, degradation is a two-step process. The copolymers with oxalate linkages degrade first, which changes the physical structure of the microbeads and promotes the degradation of the copolymers with carbonate linkages at a later stage. The hydrolysis rate of the microbeads and the duration of each degradation step could be adjusted by incorporating different ratios of copolymers with oxalyl linkages and copolymers with carbonate linkages. See Example 8 below.

[0135] Examples of achievable degradation profiles are shown in Figures 12A and 12B.

[0136] Figure 12A shows the degradation kinetics (mass loss) of copolymers prepared with 100% carbonate linkages (formula #4 - slow degradation), 100% oxalate linkages (formula #1 - fast degradation in 1 to 24 hours), and copolymers prepared with a mixture of carbonate and oxalate linkages (formulas #2 and 3 - intermediate degradation).

[0137] Specific non-limiting examples of this include Formulas 1-4 of the present invention: Formula #1: Copolymer 70%PrD-diI2DAT-co-30%PEG1k with 100% oxalate linkages. Formula #2: Copolymer 40%PrD-di2DAT-co-30%PEG400-co-30%PCL1.25k with 80% carbonate linkages and 20% oxalate linkages. Formula #3: Copolymer 40%PrD-diI2DAT-co-30%PEG1k-co-30%PCL1.25k with 80% carbonate linkages and 20% oxalate linkages. Formula #4: Copolymer 50%PrD-diI2DAT-co-50%PEG1K with 100% carbonate linkages.

[0138] FIG. 12B shows the degradation kinetics (mass loss) of microbeads prepared from a blend of copolymers composed purely of carbonate or oxalate chemical bonds.

[0139] For example, Formulas #5-7 were prepared as copolymer blends composed purely of carbonate or oxalate linkages, with the copolymer weight ratios being 50% / 50% (Formula #5), 70% / 30% (Formula #7), and 90% / 10% (Formula #6).

[0140] In this particular non-limiting example, Formula 5-7 includes: Formula #5: A blend of copolymer 50%PrD-diI2DAT-co-50%PEG1K, having 100% carbonate linkages, and copolymer 50%PrD-diI2DAT-co-50%PEG1k, having 100% oxalate linkages, 50 / 50% w / w. Formula #6: A blend of copolymer 50%PrD-diI2DAT-co-50%PEG1K, with 100% carbonate linkages, and copolymer 50%PrD-diI2DAT-co-50%PEGlk, with 100% oxalate linkages, 90 / 10% w / w. Formula #7: A blend of copolymer 50%PrD-diI2DAT-co-50%PEG1K, with 100% carbonate linkages, and poly(50%PrD-diI2DAT-co-50%PEGlk), with 100% oxalate linkages, 70 / 30% w / w.

[0141] By adjusting the ratio of iodinated structural component (PrD-diI2DAT) to rubber component (PEG400 or PEG1000) and the ratio of carbonate to oxalate linkages in a single copolymer or a blend of copolymers, a wide range of degradation profiles, including multistage degradation, could be achieved. For example, Equation 5 exhibits a rapid mass loss of approximately 30%, followed by a clear plateau, followed by a second stage of mass loss beginning at approximately 20 days. Equation 7 (lower oxalate %) exhibits a similarly clear plateau, followed by a rapid mass loss of approximately 20%, followed by a second stage of mass loss beginning at approximately 70 days.

[0142] This property is useful not only for achieving the desired embolic effect, but also for the administration of drugs or other therapeutic or biologically active agents when incorporated into the microbeads. Thus, embodiments of the copolymer blends as exemplified herein allow for the placement of embolic microspheres or microbeads eluting one or more therapeutic agents or drugs in a multiphasic time-release program. [Example]

[0143] Example Examples 1-6 demonstrate an alternative scheme for forming copolymer materials using triphosgene (TP) and oxalyl chloride to form a mixture of carbonate and oxalyl linkages between monomers / macromers. An exemplary, non-limiting embodiment is a copolymer of PrD-diI2DAT and polyethylene glycol (PEG).

[0144] As used herein, the term "PrD-diI2DAT" is an abbreviation that refers to a di-ester of 1,3-propanediol ("PrD") with di-iodinated-desaminotyrosine ("I2DAT").

[0145] Example 1 - Poly(50% PrD-diI2DAT-co-50% PEG1K carbonate). Polymer preparation for embolization therapy using triphosgene alone To a 3 L flask, 75 g of polyethylene glycol (PEG, Mn ~ 1000 Da) and PrD-diI2DAT were added. 1200 g of dichloromethane (DCM) and 54.8 g of pyridine were added. The mixture was stirred until the solution became clear.

[0146] In a 250 ml bottle, 19 g of triphosgene (TP) was dissolved in 76 g of DCM. The amount of TP was at least 1.2-1.3 times the molar equivalent of the OH groups. The TP solution was slowly added to the flask with stirring, with the addition time being approximately 1.5 hours. At this point, the reaction mixture was viscous. Depending on the desired molecular weight, more TP may be added.

[0147] The polymer was isolated by precipitation using 2-propanol (IPA) followed by multiple IPA washes. The crude polymer was redissolved in DCM, precipitated, and washed with IPA. This process was repeated until the polymer was pyridine-free. The polymer was then placed in a vacuum oven under dynamic vacuum until dry.

[0148] Example 2 - Poly(50%PrD-diI2DAT-co-50%PEG1K oxalate). Polymer preparation for embolization therapy using oxalyl chloride alone To a 3 L flask, 75 g each of polyethylene glycol (PEG, Mn-1000 Da) and PrD-diI2DAT were added. To the flask, 1200 g of dichloromethane (DCM) and 54.8 g of pyridine were added. The mixture was stirred until the solution became clear.

[0149] In a 250 ml bottle, 25 g of oxalyl chloride (OC) was dissolved in 100 g of DCM. The amount of OC was at least 1.2-1.3 times the molar equivalent of OH groups. While stirring the solution in the flask, the OC solution was slowly added over approximately 1.5 hours. At this point, the reaction mixture was viscous. Depending on the desired molecular weight, more OC may be added.

[0150] The polymer was isolated by precipitation using 2-propanol (IPA) followed by multiple IPA washes. The crude polymer was redissolved in DCM, precipitated, and washed with IPA. This process was repeated until the polymer was pyridine-free. The polymer was then placed in a vacuum oven under dynamic vacuum until dry.

[0151] Example 3 - Simultaneous Addition Preparation of a Polymer with Both Oxalate and Carbonate Attachment Groups An appropriate mixture of PrD-diI2DAT and polyethylene glycol of the desired molecular weight was dissolved in DCM in a four-neck flask equipped with an overhead stirrer, a nitrogen inlet, and two ports for liquid addition. Pyridine equivalent to 3-4 times the OH groups in the mixture was added. Approximately 1 / 2 equivalent of triphosgene, equivalent to the total number of OH groups, was dissolved in DCM. Oxalyl chloride equivalent to 1 / 2 of the total OH groups was dissolved in the same amount of DCM used to dissolve the TP.

[0152] Both the TP solution and the oxalyl chloride solution were added at the same rate with moderate stirring. After the addition was complete, the reaction mixture was stirred for 30 minutes, and the polymer was isolated by precipitation with IPA. The polymer was further purified by multiple dissolutions (DCM) and precipitations (IPA) until all by-products were removed. The polymer was dried in a vacuum oven at 40 °C.

[0153] Example 4 - Sequential Addition Preparation of a Polymer with Both Oxalate and Carbonate Attachment Groups An appropriate mixture of PrD-diI2DAT and polyethylene glycol of the desired molecular weight was dissolved in DCM in a four-neck flask equipped with an overhead stirrer, a nitrogen inlet, and two ports for liquid addition. Pyridine equivalent to 3-4 times the OH groups in the mixture was added. Approximately 1 / 2 equivalent of the total number of OH groups was dissolved in DCM. Oxalyl chloride equivalent to 1 / 2 of the total OH groups was dissolved in the same volume of DCM used to dissolve TP.

[0154] The oxalyl chloride solution was added to the flask with moderate stirring. After the addition was complete, the reaction mixture was stirred for 10 minutes, and then the TP solution was added at the same rate. After the addition was complete, the polymer was isolated by precipitation with IPA. The polymer was further purified by multiple dissolutions (DCM) and precipitations (IPA) until all by-products were removed. The polymer was dried in a vacuum oven at 40°C.

[0155] Example 5 - Alternating Addition Preparation of a Polymer with Both Oxalate and Carbonate Attachment Groups An appropriate mixture of PrD-diI2DAT and polyethylene glycol of the desired molecular weight was dissolved in DCM in a four-neck flask equipped with an overhead stirrer, a nitrogen inlet, and two ports for liquid addition. Pyridine was added in an amount equivalent to 3-4 times the OH groups in the mixture. Triphosgene (approximately 1 / 2 equivalent of the total number of OH groups) was dissolved in DCM. Oxalyl chloride equivalent to 1 / 2 of the total OH groups was dissolved in the same amount of DCM used to dissolve the TP.

[0156] With moderate stirring, approximately 1 / 20 of the oxalyl chloride solution was added to the flask. After stopping the addition and stirring for 5 minutes, approximately 1 / 20 of the TP solution was added. This addition sequence was repeated until both reagents were completely added. After the addition was complete, the reaction mixture was stirred for 30 minutes and the polymer was isolated by precipitation with IPA. The polymer was further purified by multiple dissolutions (DCM) and precipitations (IPA).

[0157] Example 6: Preparation of poly(40%PrD-diI2DAT-co-30%PEGlk-co-30%PCL1.25k) with 80% carbonate and 20% oxalate linking groups Example 6 demonstrates an exemplary method for making an alternating copolymer material suitable for preparing the generally spherical microbeads described herein.

[0158] A mixture of PrD-diI2DAT (60 g, 0.0685 mol), polyethylene glycol 1000 g / mol (45 g, 0.0450 mol), and polycaprolactone 1250 g / mol (45 g, 0.0360 mol) was added to a dry 3 L jacketed vessel set at 35 °C. The vessel assembly was capped with a four-neck cap and equipped with a stir blade assembly and motor. The mixture was stirred overnight under N2. After stirring overnight, 1200 g of dichloromethane (DCM) was added to the flask, followed by 50.99 g of pyridine, and the mixture was dissolved.

[0159] In a separate vessel, 13.6 g (0.1196 mol) of triphosgene and 54.42 g of DCM were added to obtain a 20% (W Triphosgene / W Solution ) liquid.

[0160] In a separate container, 4.36 g (0.0299 mol) of oxalyl chloride and 17.46 g of DCM were added to form a 20% (W oxalyl chloride / W Solution) ) solution was prepared.

[0161] The two solutions were alternately added via pump to a 3 L jacketed vessel containing the monomer mixture over a 3-hour period until the desired viscosity was reached. After the final viscosity was reached, the reaction was quenched by adding 125 ml of a 10% water in tetrahydrofuran solution. The polymer was purified by successive precipitations and washes with isopropanol (IPA) and multiple dissolutions in DCM. The isolated polymer was oven-dried under vacuum at 45°C.

[0162] Examples 7-17 illustrate exemplary methods for making the spherical microbeads described herein. Example 7 describes one exemplary embodiment of a method for making spherical microbeads. Example 8 illustrates an exemplary procedure for preparing microbeads from a blend of copolymer materials. Examples 9-13 illustrate methods and procedures for incorporating one or more drugs, therapeutic agents, and / or biological agents into the microbead embodiments described herein. Examples 14-17 describe microbeads comprising crosslinked polymeric materials and provide step-by-step instructions for preparing various related precursors and methods for preparing such microbeads. In Examples 7 and 8, copolymer material compositions containing oxalate linkages can be used; in such cases, the described methods can produce microbeads with porous structures.

[0163] Example 7 - Preparation of beads The microbeads of Examples 1-6 were prepared by stirring a 0.5% solution of poly(vinyl alcohol) (“PVA”) (e.g., in the range of about 0.5-2.5%) while introducing a solution of the polymer in methylene chloride (e.g., in the range of 5-25%) to form a microbead suspension in the PVA, washing the microbeads with water, coating them with a mannitol solution, and freeze-drying the microbeads.

[0164] A 0.5% PVA solution was prepared by dissolving 4 g of "cold water-soluble PVA" in 800 mL of deionized (DI) water overnight. 5 g of embolization polymer was dissolved in 50 mL of methylene chloride in a glass bottle by stirring using a magnetic stirrer or other means. 600 mL of the PVA solution was placed in a 2 L glass beaker and stirred at 700 rpm using an overhead stirrer. Using a 60 mL syringe and a 16-gauge needle, the polymer solution was introduced in one continuous stream into the stirred PVA solution. The suspension was stirred under a fume hood for 1 to 24 hours, after which the stirring was stopped.

[0165] The supernatant was decanted and discarded. The beads were washed five times with 100 mL of 2% mannitol solution, mixing the beads for approximately 30–60 seconds after each wash. The wet beads were transferred to a 100 mL flask with 25 mL of mannitol solution. While rotating the flask, the beads were frozen with the mannitol solution using dry ice / IPA or liquid nitrogen until the frozen material coated the walls. The contents of the flask were lyophilized until all the ice sublimated. The dried beads, along with the mannitol, were placed on a sieve set consisting of 500, 300, 180, and 90 micron sieves with a pan at the bottom. This separated the beads into the following ranges: >500, 300–500, 180–300, and <90 microns. The beads were then packaged and stored under nitrogen.

[0166] Other methods for producing beads include, for example, the Continuous Flow Beads (CFB) method, which has been reported to yield uniform beads of a desired size.

[0167] Example 8 - Poly(50%PrD-diI2DAT-co-50%PEG1K 100% carbonate) and Poly(50%PrD-diI2DAT-co-50%PEG1K 100% oxalate) 60 / 40% ww . Preparation of microbeads from blends of A 0.5% solution of PVA was prepared by dissolving 10 g of "cold water-soluble PVA" in 2000 mL of DI water overnight. 3 g of poly(50%PrD-diI2DAT-co-50%PEG1K 100% carbonate) and 2 g of poly(50%PrD-diI2DAT-co-50%PEG1K 100% oxalate) were dissolved in 50 mL of DCM in a glass bottle using a magnetic stirrer.

[0168] 700 mL of the PVA solution was placed in a 2 L glass beaker and stirred at 320 rpm using an overhead stirrer. Five 10 mL syringes were filled with the polymer solution. 1 / 16 inch tubing was attached to a 21.5 Ga needle. The 21.5 Ga needle was positioned above the surface of the PVA solution. Using a syringe pump, the contents of each syringe were introduced into the PVA solution through the tubing / needle at a rate of 1 mL / min. The suspension was stirred for at least 2 hours.

[0169] The supernatant was decanted and discarded. The beads were washed with 100 mL of DI water and then decanted for a total of three water washes. The beads were then washed with 100 mL of 1.25% aqueous mannitol for a total of two mannitol washes. The wet beads were transferred to a 250 mL flask with at least 100 mL of mannitol solution. The mannitol solution was decanted and replaced with 50 mL of mannitol solution. The beads were frozen with the mannitol solution using dry ice / IPA while rotating.

[0170] The frozen contents of the flask were lyophilized until all the ice had sublimed. The dried beads were placed on a sieve set along with mannitol to separate them into the appropriate size range and then packaged.

[0171] Example 9 - Preparation of paclitaxel encapsulated in microbeads The following solutions were prepared for the preparation of embolic beads:

[0172] Polymer solutions containing paclitaxel In a 250 mL vial, 35 mL of DCM was dissolved in 5.95 g of Example 1 and 1.05 g of paclitaxel (15% Wpaclitaxel / W Total solids ) and added to 20%W polymer / V DCM The solution was made and mixed overnight using a Roto-Shake Genie to dissolve.

[0173] PVA solution In a 1 L beaker, 4 g of polyvinyl alcohol (PVA, MW 30,000-70,000 g / mol) was added to 800 ml of water to obtain a 0.5% W PVA / V water A solution was prepared and stirred with a magnetic stirrer overnight to dissolve the solution.

[0174] Mannitol solution In a 1 L Erlenmeyer flask, add 7.5 g of mannitol to 600 mL of water to make a 1.25% W Mannitol / V water A solution was prepared. The solution was stirred with a magnetic stirrer until dissolved. The solution was prepared before the final washing step of the microbeads.

[0175] The microbeads were prepared as follows: The PVA solution was strained through a Texwipe directly into a 1 L cylindrical reaction vessel to remove all particulate matter. The mixture was stirred at 325 rpm. The polymer solution containing paclitaxel was added to several 10 mL syringes. The mixture was stirred for 3 hours. After stirring, the beads were allowed to settle and the aqueous phase was decanted from the vessel. The beads were washed three times with 50 mL of water, followed by three times with 50 mL of mannitol solution. The beads were then frozen in 20 mL of mannitol solution using a dry ice / IPA bath. The frozen beads were placed in an oven and dried under high vacuum. After drying, the beads were separated by passing them through a series of sieves of appropriate mesh size.

[0176] Example 10 - Preparation of rapamycin encapsulated in microbeads The following solutions were prepared for the preparation of embolic beads:

[0177] Polymer solutions containing rapamycin In a 250 mL vial, 35 mL of DCM was dissolved in 5.25 g of Example 1 and 1.75 g of rapamycin (25% W Rapamycin / W Total Solids ) plus 20% W Total / V DCM A solution was made and mixed overnight using a funnel shaker to dissolve the solution.

[0178] PVA solution In a 1 L beaker, add 4 g of polyvinyl alcohol (PVA, MW 30,000-70,000 g / mol) to 800 ml of water to obtain a 0.5% W PVA / V water The solution was prepared by magnetic stirring and allowed to mix overnight to dissolve.

[0179] Mannitol solution - In a 1 L Erlenmeyer flask, add 7.5 g of mannitol to 600 ml of water to obtain a 1.25% W Mannitol / V water A solution was made. The solution was stirred with a magnetic stirrer until dissolved. The solution was made before the final microbead washing step.

[0180] The microbeads were prepared as follows: The PVA solution was strained through a Texwipe directly into a 1 L cylindrical reaction vessel to remove all particulate matter. The mixture was stirred at 325 rpm. The polymer solution containing rapamycin was added to several 10 ml syringes. This solution was added to the PVA solution directly above. The mixture was stirred for 3 hours. After stirring, the beads were allowed to settle and the aqueous phase was decanted from the vessel. The beads were washed three times with 50 ml of water, followed by three times with 50 ml of mannitol solution. The beads were then frozen in 20 ml of mannitol solution using a dry ice / IPA bath. The frozen beads were placed in an oven and dried under high vacuum. After drying, the beads were separated and packaged by passing them through a series of sieves of appropriate mesh size.

[0181] Example 11 - Preparation of bovine serum albumin (BSA) in microbeads The following solutions were prepared for the preparation of embolic beads:

[0182] Polymer solution containing BSA In a 250 mL vial, 35 mL of DCM was added to 7.5 g of Example 1, and 20% W polymer / V DCM A solution was prepared. The solution was mixed overnight using a funnel shaker to dissolve. 1 g of BSA was added to the dissolved polymer solution and the solution was mixed thoroughly.

[0183] PVA solution In a 1 L beaker, add 16 g of polyvinyl alcohol (PVA, MW 30,000-70,000 g / mol) to 800 ml of water to obtain a 2.0% W PVA / V water The solution was prepared by magnetic stirring and allowed to mix overnight to dissolve.

[0184] Mannitol solution In a 1 L Erlenmeyer flask, add 7.5 g of mannitol to 600 mL of water to make a 1.25% W solution. Mannitol / V water A solution was prepared. The solution was stirred with a magnetic stirrer until dissolved. The solution was prepared before the final washing step of the microbeads.

[0185] The microbeads were prepared as follows: The PVA solution was filtered directly into a 1 L cylindrical reaction vessel through a Texwipe to remove all particulate matter. The mixture was stirred at 325 rpm. The polymer solution containing BSA was added to several 10 mL syringes. This solution was added to the PVA solution directly above. The mixture was stirred for 3 hours. After stirring, the beads were allowed to settle and the aqueous phase was decanted from the vessel. The beads were washed three times with 50 mL of water, followed by three times with 50 mL of mannitol solution. The beads were then frozen in 20 mL of mannitol solution using a dry ice / IPA bath. The frozen beads were placed in an oven and dried under high vacuum. After drying, the beads were separated through a series of sieves of appropriate mesh size and packaged.

[0186] Example 12 - Diffusion of doxorubicin into microbeads The following solutions / materials were prepared for drug loading of the embolic beads:

[0187] Doxorubicin dissolution in water In a 200 mL amber bottle, add 100 mL of HPLC-grade water to 200 mg of doxorubicin and 0.2% W Doxorubicin / V water A solution was prepared by sonicating for 2 minutes, vortexing for 1 minute, and then mixing overnight using a funnel shaker to dissolve the solution. A portion of this solution can be analyzed for drug content by HPLC.

[0188] Pre-prepared dry microbeads -Drug loading was successfully carried out with different copolymer compositions based on PrD-diI2DAT and PEG, as well as different copolymer mixtures, with varying bead sizes.

[0189] Diffusion of doxorubicin into microbeads was performed as follows: Approximately 50 mg of dry microbeads were added to a 4 mL screw-top glass vial. 3 mL of 0.2% doxorubicin solution was added to the microbeads. Using a funnel shaker, the sample was mixed by tumbling for 1-23 h. After mixing, the beads were allowed to settle and the supernatant was decanted. The drug-loaded beads were then ready for immediate use or analysis. Figure 9 shows the uptake of DOX by the diffusion method.

[0190] Example 13 - Encapsulation of doxorubicin into microbeads from a DOX suspension in organic solvent Prepare a suspension of 25 mg of doxorubicin in 10 mL of a 5% w / v solution of embolic polymer in dichloromethane. Mix the suspension thoroughly by vortexing and place into a stirring vessel of 0.5% poly(vinyl alcohol) with a 21 (1 / 2) gauge needle. Microbeads form, encapsulating the suspended doxorubicin particles. Decant from the poly(vinyl alcohol) solution. See Figure 13 for an image. This method allows for higher doxorubicin loading than the diffusion method.

[0191] Examples 14-17 below describe the preparation of embodiments of microbeads comprising crosslinked polymers, whereby copolymers having pendant groups containing potentially crosslinkable HEMA or HEMA-like crosslinking groups were prepared. Following the formation of preformed microbeads, crosslinking was induced by application of a free radical initiator.

[0192] Example 14 - Preparation of Diol-Containing HEMA (Compound I) A 1-L round-bottom flask was charged with glyceryl monomethacrylate (100 g, 0.624 mol) and trimethylene carbonate (318 g, 3.12 mol to 636 g, 6.24 mol) and heated under a nitrogen atmosphere until all solids were melted. The flask was then heated to 130 °C and Sn(II) octoate (0.24 g, 500 ppm) was added to the flask. The flask was heated at this temperature for 4 hours. The flask was then cooled to room temperature. To remove unreacted monomer and catalyst, the product was dissolved in dichloromethane (DCM) and precipitated twice with heptane. The product was dried in a vacuum oven at 30 °C for 24 hours. The purity of the product was determined by 1H NMR. The product was used without further treatment. Other compounds such as lactide (L or D,L), caprolactone, and glycolide can be used instead of TMC.

[0193] Example 15 - Preparation of Prepolymer with HEMA Reaction of Compound I with PrD-diI2DAT or other diol monomers or polymers

[0194] 100 g of compound I was placed in a 1-liter round-bottom flask. PrD-diI2DAT, polylactic acid diol (or oligocaprolactone, oligo-TMC, or oligo-glycolide), or a mixture thereof, was added to the flask to obtain the desired copolymer. Approximately three times the amount of excess pyridine was also added. Triphosgene (slightly more than one-third of the OH groups) was dissolved in chloroform. With moderate stirring, the triphosgene solution was slowly introduced into the reaction flask until the viscosity of the reaction mixture reached the desired value. The product was isolated by precipitation from 2-propanol or other suitable solvent. The precipitate was purified by redissolving in DCM and reprecipitating into IPA several times until all by-products of the reaction were removed. The product was dried in a vacuum oven at an appropriate temperature.

[0195] Example 16 - Preparation of HEMA-containing microbeads Microbeads can be prepared from the copolymer material from Example 15 using the method described in Example 7.

[0196] Example 17 - Incorporation of free radical initiator into microbeads A suitable solvent or mixture of solvents was found to introduce a free radical initiator into microbeads, such as those prepared in Example 16. The solvent must dissolve the free radical initiator. It should not dissolve the prepolymer, but it must swell the polymer slightly so that some of the initiator can be absorbed into the device. A solution of the initiator, such as AIBN, was prepared in this solvent mixture (a 1:1 mixture of acetone and heptane works in most cases). Dry microbeads were added to the AIBN solution for a known length of time, then removed and processed appropriately to obtain beads that did not stick together. The microbeads were crosslinked by appropriate triggering of potentially crosslinkable pendant groups on the copolymer.

Claims

1. 1. An embolic spherical microparticle comprising a copolymer material having at least one radiopaque iodine-containing component and at least one rubber component, the rubber component comprises a polymeric material having a Tg below the physiological temperature of about 37°C, the rubber component comprising an oligomer of PEG, PCL, PTMO, PTMC or a combination thereof; The radiopaque component comprises a halogenated phenyl-containing monomeric or oligomeric unit.

2. 10. The embolic spherical microparticle of claim 1, wherein the copolymer material comprises monomeric or oligomeric units linked by two or more different chemical bonds having different affinities for hydrolysis, such that the different chemical bonds have different rates of in vivo hydrolysis.

3. 3. The embolic spherical microparticle of claim 1, wherein the hydrolysis rate of the copolymer material is controlled by the relative amounts of fast degrading and slow degrading chemical bonds.

4. 4. The embolic spherical microparticle of claim 3, wherein the ratio of fast degradable chemical bonds to slow degradable chemical bonds is in the range of about 100:1 to about 1:

100.

5. 5. The embolic spherical microparticles according to claim 3 or 4, wherein the in vivo dissolution of said microparticles ranges from 1 minute to several years.

6. The embolic spherical microparticle according to any one of claims 1 to 5, wherein the ratio of said radiopaque iodine-containing component to said rubber component is from about 10:1 to about 1:

10.

7. 7. The embolic spherical microparticle according to any one of claims 1 to 6, wherein the copolymer comprises more than one rubber component having different hydrophilicity and different affinity for swelling in water or biologically relevant liquid media, and the ratio between two different rubber components having different hydrophilicity / swelling ability is in the range of about 100:1 to about 1:

100.

8. 8. The embolic spherical microparticle according to any one of claims 1 to 7, wherein hydration of the microparticle occurs to about 80-90% of the fully hydrated state in 1 to 3 minutes after contact with a liquid aqueous medium.

9. The embolic spherical microparticles according to any one of claims 1 to 8, wherein the copolymer comprises more than one rubber component with different hydrolysis rates, and the ratio of fast-degrading rubber component to slow-degrading rubber component is in the range of about 100:1 to 1:

100.

10. 10. The embolic spherical microparticles according to any one of claims 1 to 9, wherein the microparticles have internal and / or external porosity, which is generated after microparticle formation by the breakdown of fast-degrading chemical bonds and the release of volatile substances, optionally forming pores and / or "escape" channels.

11. The embolic spherical microparticle of claim 10, wherein the volatile substance is carbon dioxide.

12. 12. The embolic spherical microparticles according to any one of claims 1 to 11, wherein the microparticles have internal and / or internal / external porosity, and the porosity is created by the incorporation of a porogen material during microparticle formation and the subsequent exclusion of the porogen from the formed microparticles.

13. The embolic spherical microparticle according to any one of claims 1 to 12, wherein said microparticle is highly compressible.

14. The embolic spherical microparticles according to any one of claims 1 to 13, wherein the microparticles have high resilience, and the microparticles can return to about 90% to 100% of their original shape and size or original diameter after being released from compression.

15. The embolic spherical microparticle according to any one of claims 1 to 14, wherein the rubber component of the copolymer material comprises one or more oligomers or macromers of PEG, PCL, PTMO, PTMC, or combinations thereof.

16. The embolic spherical microparticle of any one of claims 1 to 15, wherein the radiopaque iodine-containing component comprises one or more monomers, oligomers and / or macromers of I2DTE, I2DAT, PrD-diI2DAT, or combinations thereof.

17. 16. The embolic spherical microparticle of any one of claims 1 to 15, wherein the radiopaque iodine-containing component comprises a repeating unit having the following structure: 【Chemistry 1】 In the formula, n is an integer from 1 to 18.

18. 17. The embolic spherical microparticle of claim 16, wherein said radiopaque iodine-containing component comprises PrD-diI2DAT.

19. the microparticles comprise a blend of at least two different constituent copolymers, each of the constituent copolymers comprising a polymer backbone having a predetermined amount of carbonate linkages and a predetermined amount of oxalate linkages; 19. The embolic spherical microparticle of any one of claims 1 to 18, wherein the amount of oxalate linkages relative to the amount of carbonate linkages is substantially different such that one of the two constituent copolymers hydrolyzes in vivo at a faster rate than the other constituent copolymer, resulting in multi-stage or stepwise degradation of the microparticle.

20. The embolic spherical microparticle of any one of claims 1 to 19, wherein said microparticle further comprises one or more therapeutic agents.

21. 21. The embolic spherical microparticle of claim 20, wherein the microparticle is configured to deliver and achieve controlled release of the one or more therapeutic agents.

22. The embolic spherical microparticles according to claim 20 or 21, wherein the one or more therapeutic agents are selected from the group consisting of cisplatin, doxorubicin, cyclophosphamide, paclitaxel, oxaliplatin, 5-fluorouracil, nivolumab / pembrolizumab, ipilimumab, interleukin-2, and combinations and analogs thereof.

23. The embolic spherical microparticle of any one of claims 20 to 22, wherein the therapeutic agent is dispersed in the pores of the microparticle.

24. The embolic spherical microparticle according to any one of claims 20 to 23, wherein the therapeutic agent is encapsulated in the microparticle.

25. 25. The embolic spherical microparticle of claim 24, wherein said microparticle is precipitated from a solution comprising said copolymer material and said therapeutic agent.

26. An embolization suspension comprising a solution and embolic spherical microparticles according to any one of claims 1 to 25 suspended in the solution, the microparticles being hydrated and having a diameter of about 40 µm to about 2000 µm.

27. 27. The embolizing suspension of claim 26, wherein the suspension comprises a contrast agent and saline in a ratio of about 10:90 to about 90:

10.

28. 1. A method of preparing a copolymer material for inclusion in an embolic microparticle comprising carrying out a condensation polymerization of at least two different prepolymer components, The condensation polymerization is achieved by the addition of at least two different coupling agents; The method wherein the addition of the at least two different coupling agents results in the formation of chemical bonds with different affinities for hydrolytic and / or thermal degradation along the copolymer chain of the copolymer material.

29. 30. The method of claim 28, wherein the addition of at least two different coupling agents is performed simultaneously.

30. 30. The method of claim 29, wherein the condensation polymerization results in the formation of a relatively uniform distribution of fast and slow hydrolyzable chemical bonds along the copolymer chain.

31. 30. The method of claim 28, wherein the addition of the at least two different coupling agents is continuous or sequential.

32. 32. The method of claim 31 , wherein the condensation polymerization results in the formation of blocks with fast hydrolyzable chemical bonds and blocks with slow hydrolyzable chemical bonds along the copolymer chain.

33. 30. The method of claim 28, wherein adding at least two different coupling agents comprises alternating addition of different coupling agents in multiple subportions.

34. 34. The method of claim 33, wherein the condensation polymerization results in the formation of relatively small blocks of fast and slow hydrolyzable chemical bonds along the copolymer chain.

35. 35. The method of any one of claims 28 to 34, wherein the at least two different coupling agents comprise at least one of oxalyl chloride and triphosgene (TP).

36. 1. A method for preparing porous spherical microbeads, the method comprising: Providing a polymeric material by the method of any one of claims 28 to 35; dissolving the polymeric material in a suitable solvent; flowing the polymer-containing solvent into a receiving solution to form microbeads; wherein volatile gases are produced by simultaneous partial decomposition of highly hydrolyzable chemical bonds within the polymeric material, resulting in the formation of internal pores within the microbeads.

37. 37. The method of claim 36, wherein volatile gases escaping from the microbeads create open pores and / or porosity on the outer surface.

38. 36. A method for forming porous spherical microbeads from a solution of a copolymer prepared according to any one of claims 28 to 35 with simultaneous partial decomposition of thermally labile chemical bonds, wherein volatile gases generated by the decomposition escape the microbeads, forming internal porosity and / or opening external surface porosity.

39. 1. A method for forming spherical crosslinked microbeads, comprising: including (hydroxyethyl) methacrylate (HEMA) in the polymer composition; adding a free radical initiator to a solution of the polymer; forming microbeads from a solution of the polymer such that the free radical initiator diffuses into the microbeads; initiating polymer crosslinking; A method comprising:

40. 36. An embolic spherical microparticle comprising a blend of at least two different constituent copolymers, either or both of which are prepared according to the method of any one of claims 28 to 35, wherein the coupling agents are selected such that the two constituent copolymers differ substantially in the relative content of chemical bonds formed by the two different coupling agents, and wherein one of the two constituent copolymers is hydrolyzed in vivo at a faster rate than the other constituent copolymer, resulting in multi-stage or stepwise degradation.

41. 41. The embolic spherical microparticle of claim 40, wherein the microparticle further comprises at least one therapeutic agent and is configured to release the therapeutic agent during in vivo degradation of the copolymer, the release being substantially coordinated with the multi-stage or stepwise degradation.

42. A radiopaque biodegradable embolic spherical microparticle comprising a copolymer material synthesized from at least one radiopaque iodine-containing component and at least one rubber component, the rubber component comprises a polymeric material having a Tg below the physiological temperature of about 37°C, the rubber component comprising an oligomeric PEG, PCL, PTMO, PTMC or a combination thereof; the radiopaque component comprises a halogenated phenyl-containing monomeric or oligomeric unit; A microparticle, wherein said microparticle comprises internal and / or external porosity.

43. 43. The embolic spherical microparticle of claim 42, wherein the copolymer material is linked by two or more different chemical bonds having different affinities for hydrolysis, the different chemical bonds comprising monomeric or oligomeric units having different rates of in vivo hydrolysis, and the rate of hydrolysis of the copolymer material is controlled by the relative amounts of fast-degrading and slow-degrading chemical bonds.

44. 44. An embolic spherical microparticle according to claim 42 or 43, wherein the porosity of the microparticle is created via the incorporation of a porogen material during microparticle formation and the subsequent expulsion of the porogen material from the formed microparticle.

45. 44. Embolized spherical microparticles according to claim 42 or 43, wherein porosity is formed after microparticle formation by decomposition of fast-degrading chemical bonds and release of volatile substances, optionally the volatile substances forming pores and / or forming "escape" pores.

46. The embolic spherical microparticle of any one of claims 42 to 45, wherein the microbeads are highly compressible.

47. 47. The embolic spherical microparticle of any one of claims 42 to 46, wherein the microbeads have high resilience, allowing the microbeads to return to about 90% to 100% of their original shape and size or original diameter after being released from compression.

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