Biodegradable phase-separated thermoplastic multiblock copolymers

Abstract

The present invention relates to biodegradable phase-separated thermoplastic multiblock copolymers, methods for preparing biodegradable phase-separated thermoplastic multiblock copolymers, uses of biodegradable semi-crystalline phase-separated thermoplastic multiblock copolymers, and compositions for delivering at least one bioactive compound to a host. The biodegradable phase-separated thermoplastic multiblock copolymers of the present invention comprise at least one amorphous hydrolyzable prepolymer (A) segment and at least one semi-crystalline hydrolyzable prepolymer (B) segment, wherein the multiblock copolymer has a Tg of 37°C or less and a Tm of 50 to 110°C under physiological conditions; the segments are linked by a multifunctional chain extender; the segments are randomly distributed along the polymer chain; and the prepolymer (B) segment comprises an XYX triblock copolymer, where Y is a polymerization initiator and X is a poly(p-dioxanone) segment having a block length of 7 or more, represented by p-dioxanone monomer units.

Description

[Technical Field]

[0001] The present invention relates to biodegradable, phase-separated thermoplastic multi-block copolymers, methods for preparing biodegradable, phase-separated thermoplastic multi-block copolymers, uses of biodegradable, semi-crystalline, phase-separated thermoplastic multi-block copolymers, and compositions for delivering at least one biologically active compound to a host. [Background technology]

[0002] Peptides and proteins, collectively referred to as polypeptides, play important roles in all biological processes and have recently attracted attention as potential drug candidates. Rapid advances in peptide and protein pharmacology, along with the large-scale production of these compounds by recombinant DNA technology, among other technologies, have fueled great interest in these compounds. Unfortunately, the development of peptides and proteins has far outpaced the ability to deliver these compounds systemically or locally using convenient and effective delivery systems.

[0003] Biodegradable polymers have attracted increasing attention over the past decade for use in long-acting parenteral controlled-release systems for systemic or site-specific drug delivery. Biodegradable controlled-release formulations can significantly improve the pharmacokinetics of therapeutic compounds. This is particularly relevant for the treatment of chronic diseases and compounds with narrow therapeutic windows, as systemic plasma concentrations can be reduced while reducing undesirable side effects. Furthermore, many novel bioactive compounds have short half-lives and require frequent injections to achieve therapeutically effective plasma concentrations. Patient compliance and high costs associated with frequent dosing schedules of parenterally administered bioactive compounds have led to increased interest in biodegradable parenteral sustained-release formulations.

[0004] Copolymers of lactic acid and glycolic acid, also known as poly(D,L-lactic acid) (PDLLA) and PLGA copolymers, are the most widely applied biodegradable polymers for use in parenteral sustained-release depot formulations. PLGA copolymers have been successfully used to develop sustained-release depot formulations for small molecules such as risperidone and therapeutic peptides such as leuprolide, goserelin, or octreotide.

[0005] However, PLGA polymers have several drawbacks that limit their use and make them unsuitable for polypeptide delivery. First, PLGA copolymers are relatively hydrophobic polymers and do not provide an optimal environment for encapsulated proteins. Proteins can adsorb to the polymer, causing slow and incomplete release, protein unfolding, and / or aggregation. Second, the ability to manipulate the release of larger bioactive compounds, such as encapsulated polypeptides, is limited by the negligible diffusion of such compounds through the relatively rigid, non-swelling PLGA matrix. Thus, protein release from PLGA copolymers relies on diffusion through pores present in the matrix and on matrix degradation. Typically, the encapsulated protein remains entrapped in the polymer matrix until the polymer matrix degrades to the point where it loses its integrity or dissolves, resulting in the biphasic or triphasic degradation-dependent release profile typically obtained with PLGA-based depot formulations. Finally, during degradation of PLGA copolymers, acidic moieties are formed, which accumulate in the rigid, non-swelling PLGA matrix, leading to the formation of an acidic microenvironment within the polymer matrix at low in situ pH levels, typically around 1–2. Under these acidic conditions, encapsulated proteins can form aggregates, leading to incomplete protein release. Furthermore, low pH can adversely affect the structural integrity and biological activity of encapsulated peptides or proteins, potentially resulting in reduced therapeutic efficacy and increased immunogenicity. Chemical modifications of proteins and peptides, such as acylation and adduct formation, have been reported.

[0006] Therefore, there is a need for biodegradable polymers that are more suitable for protein delivery. However, one advantage of PLGA and related polymers is that they have a proven track record of clinical use and are generally considered to be highly biocompatible, and as a result, they have been adopted by pharmaceutical companies to develop depot formulations of their active compounds for risk mitigation reasons. Therefore, it is desirable to design novel biodegradable polymeric protein delivery systems from polymers composed of well-known, biologically safe, and clinically acceptable monomers.

[0007] There remains a need in the art for additional biodegradable, phase-separated, thermoplastic multiblock copolymers. For example, the present inventors have found that multiblock copolymers containing poly(L-lactide) crystalline blocks have degradation times of 3 to 4 years. For the majority of sustained-release drug delivery formulations, such long degradation times are undesirable because they can lead to polymer accumulation upon repeated injections, potentially inducing long-term tolerability issues. It would be desirable to have multiblock copolymers with reduced degradation times compared to multiblock copolymers containing poly(L-lactide) crystalline blocks, such as degradation times of approximately 0.5 to 1.5 years, depending on the duration of release. At the same time, it would be beneficial to maintain the excellent tunability of drug release kinetics for multiblock copolymers containing poly(L-lactide) crystalline blocks.

[0008] Poly(p-dioxanone) is a biodegradable polyester known for its excellent biocompatibility, biodegradability, and mechanical flexibility. Poly(p-dioxanone) is semicrystalline and has a lower concentration of ester groups compared to lactide- and glycolide-based polyesters (Yang et al., J. Macromol. Sci.-Pol. R. 2002, 42(3), 373-398). Poly(p-dioxanone) exhibits high resistance to hydrolytic attack and degrades slowly compared to amorphous (co)polyesters such as poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) (Sabino et al., Polym. Degrad. Stabil. 2000, 69(2), 209-216; Hong et al., J. Appl. Polym. Sci. 2006, 102(1), 737-743; Lichun et al., J. Biomedical Mat. Res. 1999, 46(2), 236-244; Jie et al., Polymer Int. 1997, 42(4), 373; Fredericks et al., J. Polym. Sci Pol. Phys. 1984, 22(1), 57-66).

[0009] However, poly(p-dioxanone) is also known to be relatively hydrophilic compared to lactide- and glycolide-based polyesters. Based on the combination of (i) a reduced concentration of ester groups (contributing to slower hydrolysis), (ii) increased hydrophilicity (contributing to faster hydrolysis), and (iii) the use of low molecular weight prepolymer blocks in the multiblock copolymers, it is extremely difficult to predict the degradation rate of multiblock copolymers composed of low molecular weight crystalline poly(p-dioxanone) blocks compared to the degradation rate of multiblock copolymers composed of low molecular weight crystalline poly(L-lactide) blocks.

[0010] Furthermore, the use of poly(p-dioxanone) (PPDO) as a crystalline block in multiblock copolymers has been disadvantageous, as previously reported by the present inventors (WO 2013 / 015685). The synthesis of multiblock copolymers in which the crystallizable segment is based on PPDO is hindered by the limited polymerization of the p-dioxanone monomer and the limited solubility of PPDO in common solvents. The limited solubility of PPDO-containing polymers also limits their use for the preparation of controlled-release formulations. Furthermore, according to WO 2013 / 015685, the crystallization of PPDO is expected to be slow and incomplete at fast cooling rates and / or low PPDO molecular weights, making the preparation of microspheres by a solvent extraction / evaporation-based microencapsulation process using multiblock copolymers with short PPDO blocks as segment B impractical. Summary of the Invention [Problem to be solved by the invention]

[0011] SUMMARY OF THE INVENTION It is an object of the present invention to fulfill the above-mentioned need in the art and / or to overcome one or more of the shortcomings found in the prior art. [Means for solving the problem]

[0012] The present inventors have surprisingly found that one or more of these objectives can be at least partially met when using a prepolymer (B) segment comprising poly(p-dioxanone) and having a predetermined block length.

[0013] Thus, in a first aspect, the present invention provides a biodegradable, phase-separated thermoplastic multi-block copolymer comprising at least one amorphous hydrolyzable prepolymer (A) segment and at least one semi-crystalline hydrolyzable prepolymer (B) segment, The multi-block copolymer has a Tg of 37°C or less and a Tm of 50 to 110°C under physiological conditions; the segments are linked by a multifunctional chain extender; the segments are randomly distributed along the polymer chain; and The prepolymer (B) segment comprises an XYX triblock copolymer, wherein: Y is a polymerization initiator, and X is a poly(p-dioxanone) segment having a block length of 7 or more represented by p-dioxanone monomer units; This invention relates to biodegradable phase-separated thermoplastic multi-block copolymers.

[0014] In a further aspect, the present invention provides a method for producing a pharmaceutical composition comprising: i) carrying out a chain extension reaction of prepolymer (A) and prepolymer (B) in the presence of a polyfunctional chain extender, wherein prepolymers (A) and (B) are both terminated with a diol or a diacid, and the chain extender is terminated with a dicarboxylic acid, a diisocyanate, or a diol; or ii) carrying out a chain extension reaction using a coupling agent, wherein the prepolymers (A) and (B) are both terminated with a diol or a diacid, and the coupling agent is preferably dicyclohexylcarbodiimide; Including, The prepolymer (B) segment comprises an XYX triblock copolymer, wherein: Y is a polymerization initiator, and X is a poly(p-dioxanone) segment having a block length of 7 or more represented by p-dioxanone monomer units; The present invention relates to a method for preparing a biodegradable, phase-separated, thermoplastic multi-block copolymer.

[0015] In yet another aspect, the present invention relates to the use of the biodegradable, semi-crystalline, phase-separated thermoplastic multi-block copolymers of the present invention, preferably in the form of a microsphere, microparticle, nanoparticle, nanosphere, rod, implant, gel, coating, film, sheet, spray, tube, membrane, mesh, fiber, or plug, for drug delivery.

[0016] In yet another aspect, the present invention relates to a composition for delivering at least one bioactive compound to a host, comprising at least one bioactive compound encapsulated in a matrix, said matrix comprising at least one biodegradable semi-crystalline phase-separated thermoplastic multi-block copolymer of the present invention. [Brief explanation of the drawings]

[0017] [Figure 1] In vitro erosion of 50CP10C20-LL40: Experimental data up to 12 months and extrapolation of experimental data to complete erosion. [Figure 2] In vitro erosion of microspheres composed of various L-MBCP, I-MBCP, and SC-MBCP polymers. 50CP10C20-LL40 is included as a reference. [Figure 3] In vitro erosion of microspheres composed of D-MBCP polymers containing various poly(ε-caprolactone)-PEG-poly(ε-caprolactone) counterblocks. 50CP10C20-LL40 is included as a reference. [Figure 4A] DSC thermogram of [poly(ε-caprolactone)- co -PEG- co -poly(ε-caprolactone)]- b -[poly( p -dioxanone)] multiblock copolymer: RCP-15126 multiblock copolymer. [Figure 4B] DSC thermogram of [poly(ε-caprolactone)- co -PEG- co -poly(ε-caprolactone)]- b -[poly( p -dioxanone)] multiblock copolymer: RCP-15125 multiblock copolymer. [Figure 4C] DSC thermogram of [poly(ε-caprolactone)- co -PEG- co -poly(ε-caprolactone)]- b -[poly( p -dioxanone)] multiblock copolymer: RCP-1524 multiblock copolymer. [Figure 5A]DSC thermogram of 60LP2L20-D27 (RCP 1926) multiblock copolymer. [Figure 5B] DSC thermogram of 10LP6L12-D27 (RCP 1804) multiblock copolymer. [Figure 5C] DSC thermogram of 10LP10L20-D27 (RCP 1810) multiblock copolymer. [Figure 5D] DSC thermogram of 50DP10D24-D25 (RCP 1509) multiblock copolymer. [Figure 6] SEM images of various polymer-only microsphere batches prepared using poly(p-dioxanone)-based multiblock copolymers with different compositions of the hydrophilic block (PEG Mn, PEG content, poly(ε-caprolactone) chain length, and block ratio). [Figure 7] In vitro erosion kinetics of polymer-only microspheres consisting of 57CP10C20-D28, 35CP15C20-D24, 50CP15C20-D24, and 20CP30C40-D23 (50CP10C20-LL40 was used as a reference). [Figure 8] Effect of the molecular weight of poly(ε-caprolactone) chains on the in vitro erosion of several poly(p-dioxanone)-based multiblock copolymers (50CP10C20-LL40 was used as a reference). [Figure 9] SEM images of polymer-only microspheres prepared from 60CP10C20-Dxx multiblock copolymers consisting of poly(p-dioxanone)-blocks with different molecular weights (Mn). [Figure 10] Effect of molecular weight (Mn) of poly(p-dioxanone) prepolymer block on the enthalpy of fusion of 60CP10C20-Dxx multiblock copolymers and polymer-only microspheres composed of them. [Figure 11A]SEM images of polymer-only microspheres prepared with 60CP10C20-Dxx polymers containing poly(p-dioxanone) blocks with Mn of 2116 g / mol (RCP-1710), 2356 g / mol (RCP-1718), and 2806 g / mol (RCP-1714). [Figure 11B] In vitro erosion kinetics of RCP-1710, RCP-1718, and RCP-1714 (50CP10C20-LL40 is included as a reference). [Figure 12A] Cumulative in vitro release of bovine serum albumin from 60CP10C20-D26 based microspheres. [Figure 12B] Cumulative in vitro release of lysozyme from 20CPl5C50-D23-based microspheres. [Figure 13] Cumulative in vitro release of a 1.5 kDa peptide from microspheres prepared with a 10 / 90 block ratio of [poly(ε-caprolactone)-PEG1000-poly(ε-caprolactone)]-b-[poly(p-dioxanone)] multiblock copolymer. Release is shown as μg peptide released over time. [Figure 14A] SEM image (AD19-003-1 (1.0 mm)). [Figure 14B] Cumulative in vitro release of hot-melt extruded levonorgestrel implants prepared with various (multiblock) copolymers. DETAILED DESCRIPTION OF THE INVENTION

[0018] The multi-block copolymers of the present invention can be composed of at least two different segments, each with different physical properties, including degradation and swelling characteristics. Due to their unique composition and semi-crystalline phase-separated morphology, the materials of the present invention are surprisingly versatile and highly suitable for constructing drug delivery matrices and drug-eluting coatings, which can be used to encapsulate specific therapeutic agents and sustainedly release the encapsulated therapeutic agents locally or into the systemic circulation. Compositions containing the biodegradable, phase-separated thermoplastic multi-block copolymer matrices of the present invention are particularly important for the sustained release of bioactive compounds, such as small molecules or bioactive polypeptides, into a host. Furthermore, the multi-block copolymers of the present invention degrade faster than the water-swellable, phase-separated polymers disclosed in WO 2013 / 015685.

[0019] It has been reported in the art that the synthesis of multiblock copolymers in which the crystalline segments are based on poly(p-dioxanone) is hindered by the limited polymerization of the monomer, p-dioxanone, and the limited solubility of poly(p-dioxanone) in common solvents. For example, as described in WO 2013 / 015685, this typically results in a maximum conversion of about 80%, although monomers such as lactide and glycolide can be readily polymerized to conversions of over 95%.

[0020] The synthesis of prepolymers containing poly(p-dioxanone) is very challenging because the reaction mixture usually becomes solid due to crystallization of poly(p-dioxanone) already early in the polymerization process. This means that the stirring of the reaction mixture is suppressed at that stage, and propagation can only occur in the liquid regions where the dissolved monomers are located in the matrix of the crystalline poly(p-dioxanone).

[0021] We have found that this also means that p-dioxanone monomer readily sublimes out of the polymerization reaction mixture, so conversion monitoring must be performed carefully. Therefore, a high degree of monomer sublimation indicates a high conversion rate. Through careful management of the poly(p-dioxanone) synthesis, we have been able to achieve conversion rates of over 90% with control of the poly(p-dioxanone) block molecular weight to within ±1 monomer unit. This also means that the monomer content of the resulting poly(p-dioxanone) block is typically 10-20% of the total weight of the poly(p-dioxanone) block. However, we have found that in multiblock copolymer synthesis, the monomer does not interfere with the chain extension reaction. Controlling p-dioxanone conversion also allows for molecular weight control. Furthermore, we have found that accurate control of poly(p-dioxanone) block length is possible by predicting the actual conversion rate at the desired poly(p-dioxanone) block length. By overestimating, assuming 80-90% conversion, we were able to determine the exact block length. For example, starting with 27 monomers and having 85% conversion yields an X block of (27 / 2 x 0.85 =) 11.5 monomers. At 80% conversion, we obtain an X block of (27 / 2 x 0.80 =) 11 monomers. At 90% conversion, we obtain an X block of (27 / 2 x 0.90 =) 12 monomers.

[0022] p-Dioxane is selected as the solvent of choice for the chain extension reaction due to its compatibility with the chain extender / Sn(Oct)2 combination used. Our data also show that p-dioxane can be easily removed from the polymer at temperatures that do not pose a threat to the integrity of the polymer due to its relatively low boiling point and reasonable volatility. Possible solvent alternatives for chain extension, such as dimethyl sulfoxide (DMSO) or dimethylacetamide (DMAc), are less attractive because their higher boiling points make them much more difficult to remove from the polymer, potentially raising concerns about the polymer's stability and biological acceptability. p-Dioxane has been described as a nonsolvent for poly(p-dioxanone) (Yang et al., J. Macromol. Sci.-Pol. R. 2002, 42(3), 373-398; Kim et al., J. Chem. Eng. Data 2006, 51(4), 1182-1184), but its solubility is sufficient in combination with the low molecular weight of the current polymer.

[0023] The term "phase separated" as used herein refers to a system, especially a copolymer, constructed of two or more different prepolymers, where at least two of said prepolymers are (partially) incompatible with each other at body temperature (under physiological conditions, such as in the human body). Thus, the prepolymers do not form a homogeneous mixture when combined, either as a physical mixture of prepolymers or as a single chemical species, as a "chemical mixture," i.e., a copolymer.

[0024] The term "prepolymer" as used herein refers to polymer segments that are randomly linked by a polyfunctional chain extender and that together constitute the multi-block copolymer of the present invention. Each prepolymer can be obtained by polymerization of appropriate monomers, which are the chemical units of each prepolymer. The desired properties of the prepolymer of the present invention, and consequently the desired properties of the multi-block copolymer of the present invention, can be controlled by selecting a prepolymer of appropriate composition and molecular weight (especially Mn) to obtain the required Tm or Tg.

[0025] As used herein, the terms "block" and "segment" refer to distinct regions in a multi-block copolymer. The terms block and segment are used interchangeably.

[0026] As used herein, the term "multiblock" refers to the presence of at least two distinct prepolymer segments in the polymer chain.

[0027] The term "thermoplastic" as used herein refers to the non-crosslinking nature of the multi-block copolymer. Thermoplastic polymers become liquid when heated and solidify when (re)cooled. Thermoplastic polymers are soluble in suitable solvents.

[0028] As used herein, the term "hydrolyzable" refers to the ability of a molecule to react with water and undergo cleavage. Hydrolyzable groups include ester, carbonate, phosphazene, amide, and urethane groups. Under physiological conditions, only ester, carbonate, and phosphazene groups react with water on a reasonable time scale.

[0029] As used herein, the term "multifunctional chain extender" refers to the presence of at least two reactive groups on the chain extender that allow reactive prepolymers to be chemically linked to form a multi-block copolymer.

[0030] As used herein, the term "random multi-block copolymer" means a multi-block copolymer in which the different segments are randomly distributed along the polymer chain.

[0031] As used herein, the term "water-soluble polymer" refers to a polymer that has good solubility in an aqueous medium, such as water, under physiological conditions. This polymer, when copolymerized with a more hydrophobic moiety, renders the resulting copolymer swellable in water. The water-soluble polymer may be a diol, diamine, or diacid. A diol or diacid is preferably used to initiate the ring-opening polymerization of a cyclic monomer.

[0032] As used herein, the term "swellable" refers to the uptake of water by a polymer. The swelling ratio can be calculated by dividing the mass of the water-swollen copolymer by the mass of the dry copolymer.

[0033] As used herein, the term "semi-crystalline" refers to a morphology of a multi-block copolymer that contains two distinct phases: an amorphous phase and a crystalline phase. In one embodiment, the multi-block copolymer is composed of an amorphous phase and a crystalline phase.

[0034] As used herein, the term "biologically active compound" is intended to be broadly interpreted as any agent that provides a therapeutic or prophylactic benefit, including, but not limited to, antimicrobial agents (including antibacterial agents and antifungal agents), antiviral agents, anticancer agents, hormones, and immunogens.

[0035] As used herein, the term "bioactive polypeptide" refers to peptides and proteins that are biologically active in the mammalian body, particularly the human body.

[0036] The present inventors have surprisingly found that the multi-block copolymers of the present invention, which contain poly(p-dioxanone) in the prepolymer (B) segment, have desirable degradation times that allow for good release of proteins and / or polypeptides. At the same time, the degradation products of the multi-block copolymer do not cause, or significantly reduce, degradation of the peptide or protein. Thus, the bioactive compounds and their functionality remain intact (or largely intact).

[0037] The multiblock copolymer of the present invention has a Tm of 50 to 110°C under physiological conditions, for example, at a temperature range of 60 to 110°C, 60 to 100°C, 70 to 100°C, or 70 to 90°C. This is due to the prepolymer (B) segment. The (B) segment comprises 70% or more of poly(p-dioxanone) based on the total weight of the prepolymer (B) segment. In another embodiment, the (B) segment comprises 80% or more, 85% or more, 90% or more, or 95% or more of poly(p-dioxanone) based on the total weight of the prepolymer (B) segment. In one embodiment, the (B) segment is based on a prepolymer comprising poly(p-dioxanone). The amorphous phase of the phase-separated multiblock copolymer of the present invention is primarily composed of soft (A) segments. The present inventors surprisingly found that the amorphous portion of the hard (B) segments also contributes to the overall amorphous phase of the multiblock copolymer of the present invention.

[0038] According to the present invention, the prepolymer (B) segment comprises poly(p-dioxanone). The prepolymer (B) segment may further comprise additional monomer units such as ε-caprolactone and / or δ-valerolactone.

[0039] The prepolymer (B) segment comprises an XYX triblock copolymer, where Y is a polymerization initiator and X is a poly(p-dioxanone) segment. The block length of the poly(p-dioxanone) segment X, represented by p-dioxanone monomer units, is 7 or more. Preferably, the block length of the poly(p-dioxanone) segment X may be 7 to 35 p-dioxanone monomer units, such as 7 to 30 p-dioxanone monomer units, 8 to 25 p-dioxanone monomer units, 9 to 20 p-dioxanone monomer units, 10 to 15 p-dioxanone monomer units, or 11 to 14 p-dioxanone monomer units.

[0040] Thus, the prepolymer (B) segment can comprise an XYX triblock copolymer, where each poly(p-dioxanone) segment X has a block length, in p-dioxanone monomer units, of 7 or more.

[0041] In one embodiment, the prepolymer (B) segment consists of an XYX triblock copolymer.

[0042] The polymerization initiator Y in the XYX triblock copolymer can suitably be a diol, such as an aliphatic diol having 2 to 8 carbon atoms. Examples of suitable aliphatic diols for use as the polymerization initiator Y include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, diethylene glycol, dipropylene glycol, triethylene glycol, poly(ethylene glycol), 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, hydrogenated bisphenol A, and glycerol. Preferred polymerization initiators include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, and 1,6-hexanediol. More preferred polymerization initiators include ethylene glycol, 1,4-butanediol, and 1,6-hexanediol. In one embodiment, the polymerization initiator is 1,4-butanediol.

[0043] If the block length of the prepolymer (B) segment is too short, the melting enthalpy will be too low, resulting in too low / slow crystallization of the polymer matrix during dichloromethane extraction, and too slow hardening of the microspheres, which may lead to aggregation, smearing, and / or adhesion of the microparticles during preparation, and a microparticle dry powder with a very wide particle size distribution. In addition, small prepolymer (B) segments may result in incomplete crystallization. This may cause further crystallization during storage, which may change important properties of the product (e.g., release rate, etc.), making the product unstable.

[0044] The prepolymer (B) segment may suitably have a molecular weight distribution (Mw / Mn) of 1.0 or greater, for example, 1.1 or greater, 1.2 or greater, 1.3 or greater, or 1.4 or greater. In one embodiment, the molecular weight distribution of the prepolymer (B) segment is 3.0 or less. In another embodiment, the molecular weight distribution of the prepolymer (B) segment is 2.0 or less, for example, 1.8 or less, 1.6 or less, 1.5 or less, or 1.4 or less. A larger molecular weight distribution of the prepolymer (B) segment adversely affects the crystallization potential of the multiblock copolymer. In other words, this means that such multiblock copolymers are less suitable for preparing microspheres.

[0045] The prepolymer (B) segment further has a density (measured in accordance with ASTM D1505) of 1.1 g / cm 3 For example, 1.15 g / cm 3 or more, or 1.2 g / cm 3 The density of the prepolymer (B) can be 1.5 g / cm or more. 3 For example, 1.45 g / cm 3 or less, or 1.4 g / cm 3 The melt flow index of the prepolymer (B) segment (measured in accordance with ASTM D1238-86 at 150°C under a load of 2.16 kg) can be 0.1 g / 10 min or more, for example, 0.2 g / 10 min or more, or 0.3 g / 10 min or more. The melt flow index of the prepolymer (B) (measured in accordance with ASTM D1238-86 at 150°C under a load of 2.16 kg) can be 7 g / 10 min or less, for example, 6 g / 10 min or less, or 5 g / 10 min or less.

[0046] The hard prepolymer (B) segments of the multiblock copolymers of the present invention are typically semi-crystalline, i.e., partially amorphous. The amorphous portions of the hard (B) segments are (partially) phase-mixed with the soft (A) segments, and both contribute to the overall Tg of the multiblock copolymer. Therefore, the Tg of the amorphous phase is determined by both the Tg of segment (A) and the Tg of segment (B), in conjunction with the molar ratio of segment (A) to segment (B). The Tg can vary from a Tg close to that of prepolymer (A) (when the ratio of prepolymer (A) to prepolymer (B) is close to 1) to a Tg close to that of prepolymer (B) (when the ratio of prepolymer (A) to prepolymer (B) is close to 0). Importantly, because the diffusion of the active substance occurs through the amorphous phase rather than through the dense crystalline phase, the release of the active substance encapsulated in the polymer matrix is ​​highly dependent on the Tg of the amorphous phase. This also affects the rate of water influx and hence hydrolysis, so the rate of polymer degradation is highly dependent on the Tg of the amorphous phase.

[0047] The multiblock copolymers of the present invention allow the preparation of non-sticky microspheres by various processes, including solvent extraction / evaporation based emulsification processes such as oil-in-water (O / W) emulsions, water-in-oil-in-water (W / O / W) emulsions, solid-in-oil-in-water (S / O / W) emulsions, water-in-oil-in-oil (W / O / O) emulsions, or solid-in-oil-in-oil (S / O / O) emulsions. The minimum length of the crystalline prepolymer (B) segment plays an important role in obtaining multiblock copolymers with good product stability and good processability. Suitable microspheres cannot be prepared using multiblock copolymers in which the prepolymer (B) segment comprises an XYX triblock copolymer, where X is composed of a short poly(p-dioxanone) block, because the short poly(p-dioxanone) blocks do not crystallize well and / or crystallize very slowly. Such incompletely crystallized polymers are unstable during storage because further crystallization may occur, which alters important properties of the polymer. In addition, short prepolymer (B) segments can result in sticky polymers that cause problems during processing, such as aggregation and fusion of microspheres during extraction / evaporation processes.

[0048] The multi-block copolymers of the present invention further enable the preparation of solid drug delivery implants by hot-melt extrusion. While semi-crystalline multi-block copolymers containing crystalline PLLA blocks with high melting points, such as 50[PCL-PEG1500-PCL]-b-[PLLA], require high extrusion temperatures of 130°C or higher, multi-block copolymers containing crystalline PPDO blocks can be extruded at melting points as low as 80°C, which is suitable for preserving the integrity of labile molecules and polypeptide-based active ingredients.

[0049] In one embodiment, the multiblock copolymers of the present invention contain segments derived from water-soluble polymers (e.g., hydrophilic PEG segments). The presence of such segments promotes the swelling of the phase-separated multiblock copolymers in an aqueous environment, forming a swollen hydrogel that provides a natural environment for bioactive compounds, such as proteins. When the multiblock copolymers of the present invention are applied as a polymer matrix in a controlled-release formulation for delivering bioactive compounds, the swelling property of the multiblock copolymers can avoid the accumulation of acidic degradation products formed during hydrolysis of the polymer chains in the polymer matrix. Instead, such degradation products are released from the matrix, thereby preventing the creation of an acidic microenvironment in the polymer matrix that could be harmful to the encapsulated bioactive compound. Furthermore, the swelling property of the phase-separated multiblock copolymers allows for the sustained release of any encapsulated compound by diffusion. This avoids the biphasic or triphasic release pattern typically obtained with non-swelling biodegradable polyesters, such as poly(D,L-lactide) or poly(lactic-co-glycolic acid).

[0050] In the multi-block copolymers of the present invention, the content of segments derived from water-soluble polymers may be varied independently of the block length of the prepolymer (B) segments (crystalline segments). Thus, a high content of segments derived from water-soluble polymers can be achieved while maintaining crystallinity. Furthermore, the intrinsic viscosity (IV) of the multi-block copolymers of the present invention may be varied independently of the composition. The high variability of the multi-block copolymers of the present invention allows for easy adjustment of the segment length, ratio, and composition to achieve desired degradation characteristics and drug release kinetics.

[0051] The multiblock copolymers of the present invention have additional advantages over the ABA-structured block copolymers disclosed by Kissel et al. (J. Contr. Rel. 1996, 39(2), 315-326). These block copolymers contain a hydrophilic poly(ethylene oxide) B-block and a hydrophobic, biodegradable poly(D,L-lactide-co-glycolide) A-block (poly(D,L-lactide-co-glycolide)-poly(ethylene glycol)-poly(D,L-lactide-co-glycolide). Although polymer properties can be significantly improved by using block copolymers with blocks of different copolymers instead of homo- or random copolymers, these ABA copolymers still have certain drawbacks.

[0052] Typically, ABA copolymers must have a certain minimum molecular weight to ensure that important quality characteristics, such as mechanical stiffness, processability, or thermal stability, are met. To achieve a certain minimum molecular weight for an ABA copolymer, the A and B sequences must have specific lengths. The blocks may independently behave as individual homopolymers with similar compositions. The properties of ABA copolymers can only be tuned by varying the composition of the A and B blocks. Another drawback is that block copolymers must be prepared under inert conditions at relatively high temperatures (>100°C) to fully convert all monomers and achieve sufficient molecular weight. The first drawback can be overcome by using multiblock copolymers, in which the blocks or segments are much shorter and are linked together by chemical reactions carried out at temperatures below 100°C. Properties such as degradation behavior can be tuned in a much better way by selecting the appropriate combination of segment length, ratio, and composition.

[0053] Furthermore, due to the relatively high temperatures used in the preparation of ABA block copolymers (and their derivatives), there is always a possibility of transesterification, resulting in some degree of phase mixing. The multiblock copolymers of the present invention do not suffer from this drawback because they can be prepared by linking prepolymers with predetermined monomer compositions at relatively low temperatures (<100°C), avoiding transesterification and other side reactions that can lead to undesirable degradation and the generation of other by-products. That is, the length of the monomer sequence in the copolymer is determined by the selection of components and not so much by the reaction time and temperature typically applied in the synthesis of random copolymers. Another advantage of the multiblock copolymers of the present invention, which are prepared by linking prepolymers using a polyfunctional chain extender, is that the prepolymer segments are randomly distributed throughout the copolymer, providing much greater possibilities for tailoring the properties. Random multiblock copolymers are, for example, ABBBBABAAABBAAAAA... etc. The random multiblock copolymers of the present invention offer many advantages not available with alternating multiblock copolymers.

[0054] First, the random multiblock copolymer obtained by chain-extending the A and B blocks has no limit on the ratio of A to B. A:B can be, for example, 10:90, but can also be 90:10. In contrast, the ratio of blocks in an alternating multiblock copolymer is limited to that used in a chain-extended polymer. For example, in the case of chain-extension of AB, the A:B ratio in the multiblock copolymer is 50:50. The random nature of the multiblock copolymers of the present invention greatly increases the possible compositions of the material, allowing for control of its physical and chemical properties. This includes better control of swelling ability in water, morphology (phase separation, amorphous / crystalline), and polymer degradation.

[0055] Second, the synthesis method for the random multiblock copolymers of the present invention is significantly less laborious than the synthesis of alternating multiblock copolymers. In alternating multiblock copolymers, segments A and B in the case of an AB diblock, or segments A and C in the case of an ACA triblock, must be linked (or a macrochain extender must be synthesized) prior to chain extension. In random multiblock copolymers, the separate A and B blocks do not need to be linked prior to chain extension, but are directly chain extended with a chain extender.

[0056] Another advantage of the multi-block copolymers of the present invention is that they are based on multifunctional (e.g., aliphatic) chain extenders. By selecting the type and amount of chain extender, the properties of the polymer can be influenced (e.g., the chain extender may act as a softener or affect the degree of phase separation). Overall, there is a great deal of freedom to obtain polymers with desired properties.

[0057] The phase-separated multiblock copolymers of the present invention can swell sufficiently under aqueous and physiological conditions upon administration, providing an aqueous microenvironment for the encapsulated peptide or protein and enabling diffusion-controlled release of the peptide or protein. This allows the material to exhibit a significant decrease in mechanical strength. While such materials can be used as shape-memory materials under dry conditions without exhibiting a significant decrease in mechanical strength before transitioning to a memorized shape, for example, by using temperature or light as an external trigger, these materials absorb significant amounts of water due to their hydrophilic nature, which results in extensive swelling and plasticization of the material, resulting in a significant change in dimension and a significant decrease in mechanical strength under hydrated conditions. As a result, under hydrated conditions, such as the physiological conditions encountered in the human or animal body, constructs prepared from these materials undergo significant changes in size, and the mechanical properties of these materials change by orders of magnitude. In contrast to the multiblock copolymers of the present invention, the shape-memory materials described in U.S. Pat. No. 5,711,958 exhibit little swelling under hydrated conditions, such as the physiological conditions encountered in the human or animal body.

[0058] The phase-separated polyesters or polyestercarbonates of the present invention are a promising group of biomaterials that can be used in a variety of drug delivery applications because they offer excellent control over drug release, allowing for the release of biologically active compounds such as polypeptides.

[0059] The morphology of a multiblock copolymer (or construct using the same) depends on environmental conditions: DSC (differential scanning calorimetry) measurements can be performed under inert (dry) conditions, and the results can be used to characterize the thermal properties of the dry material. However, the morphology and properties under physiological conditions (i.e., in the body) can differ from those under ambient conditions (dry, room temperature). The transition temperatures Tg and Tm used herein are understood to refer to the corresponding values ​​of the material when applied in vivo (i.e., at body temperature and in equilibrium with an aqueous environment or an atmosphere saturated with water vapor). This can also be simulated in vitro by equilibrating the material with a water-saturated atmosphere and then performing DSC measurements. In the dry state, the materials used in the present invention can have Tg values ​​somewhat higher than those observed in the mammalian body; that is, when a dry material is subjected to DSC, the first inflection point can occur at relatively high temperatures, e.g., 42°C, 50°C, or higher. However, when applied in vivo, the Tg and / or Tm of the dry material decreases due to absorption of water, which plasticizes the polymer, and the final Tg is, according to the present invention, at or below body temperature, which should occur under physiological conditions at temperatures between 50°C and 110°C.

[0060] For example, a polymer containing PEG in the soft prepolymer (A) segment can crystallize under dry conditions at ambient temperature, but is amorphous under wet conditions, resulting in a mixed Tg or two separate Tgs for the soft prepolymer (A) segment. The phase-separated properties of the copolymers of the present invention are reflected in their Tg or Tm profiles. Phase-separated copolymers are characterized by at least two phase transitions, each of which is related to (but generally not identical to) the corresponding Tg or Tm value of the prepolymer contained in the copolymer. Tg is determined by taking the midpoint of a particular thermal jump, as can be measured, for example, by DSC. Tm is the peak maximum of the melting peak. As defined herein, the Tg and Tm values ​​of a given prepolymer reflect those measured for the copolymer. If the prepolymers are completely immiscible, the Tg of the copolymer is dominated solely by the Tg of the amorphous soft prepolymer (A). However, in reality, the composition of the crystalline and amorphous phases of a multi-block copolymer is not the same as the composition of the soft prepolymer (A) segment and the semi-crystalline prepolymer (B) segment. The amorphous portion of the original hard segment forming the prepolymer mixes with the soft segment forming the prepolymer (A) and becomes part of the amorphous phase. The Tg value of the amorphous phase is different from that of the prepolymer used. The degree of miscibility (and therefore the deviation of Tg and / or Tm from that of the corresponding prepolymer) depends on the composition, ratio, and segment length of the prepolymers in the copolymer. The Tg of the copolymer segment is generally between that of the phase-mixed copolymer and that of the individual prepolymers.

[0061] The physicochemical properties (e.g., decomposition, swelling, thermal properties, etc.) of multiblock copolymers can be easily adjusted by changing the type and chain length and chain ratio of the soft and hard segment monomers forming the prepolymer, as well as by selecting the type and amount of chain extender. Furthermore, the phase transition temperature is low enough to process the polymer in the melt. The ratio and distribution of the monomers in the copolymer can be easily controlled by changing the polymerization conditions.

[0062] To obtain a non-adhesive material, a crystalline prepolymer (B) segment is usually desirable. Furthermore, a phase-separated morphology with amorphous and crystalline regions must be maintained during exposure to physiological conditions (i.e., an aqueous environment at body temperature) to control the swelling of the polymer matrix. Controlling the degree of swelling is essential for controlling the release of the encapsulated compound. The crystalline prepolymer (B) segment acts as a physical crosslink to control the swelling of the more hydrophilic soft prepolymer (A) segment. In addition to being influenced by the content of the hard prepolymer (B) segment, the swelling degree of the polymer also depends on the content and molecular weight / length of the water-soluble polymer in the soft prepolymer (A) segment.

[0063] A prerequisite for a phase-separated segmented multiblock copolymer is that it has a Tm in the range of 50 to 110°C and a Tg of 37°C or less under physiological conditions. This may be obtained by using a prepolymer (B) having a Tm in the range of 50 to 110°C under physiological conditions and a prepolymer (A) having a Tg of 37°C or less under physiological conditions. The prepolymer (B) can have a Tm in the range of 60 to 110°C under physiological conditions, such as 60 to 100°C, 70 to 100°C, or 75 to 95°C. The Tm of the prepolymer (B) segment in the multiblock copolymer can be lower than the Tm of the unreacted prepolymer (B) due to the reduced chain flexibility of the prepolymer incorporated into the multiblock copolymer and the possibility of phase mixing of other components of the multiblock copolymer in the crystalline phase. The prepolymer (A) can have a Tg of 30°C or less under physiological conditions, such as 25°C or less, 15°C or less, or 5°C or less. Prepolymer (B) can have a Tg of 0° C. or less. In one embodiment, prepolymer (B) can have a Tg of −20° C. or less, −25° C. or less, −30° C. or less, −35° C. or less, or −40° C. or less.

[0064] In general, a desired phase-separated morphology (reflected in one Tm and at least one low Tg value) may be obtained by varying the composition, for example, by selecting the number average molecular weight Mn of prepolymer (A) and prepolymer (B). It is also possible to influence the phase-separated morphology by varying the ratio of segment A / segment B.

[0065] The segmented multiblock copolymers of the present invention comprise soft prepolymer (A) segments derived from prepolymer (A). Prepolymer (A) is hydrolyzable and typically completely amorphous under physiological (in vivo) conditions. Furthermore, in one embodiment, prepolymer (A) has at least one phase transition, measured under physiological (in vivo) conditions, with a Tg of 37°C or less, or in one embodiment, 35°C or less, 30°C or less, or 25°C or less. This segment is part of the amorphous phase in the multiblock copolymer, which is herein referred to as phase (A). The copolymers of the present invention also comprise hard prepolymer (B) segments derived from prepolymer (B). Prepolymer (B) typically comprises a semicrystalline hydrolyzable polymer having a Tm of 50-110°C measured under physiological (in vivo) conditions. The prepolymers (A) and (B), which form the "soft" and "hard" segments, respectively, are linked by a polyfunctional chain extender. Typically, the crystalline phase(s) consist of hard prepolymer (B) segments, and the amorphous phase(s) consist of soft prepolymer (A) segments and the amorphous portions of the prepolymer (B) segments. The crystalline and amorphous phase(s) are incompatible or only partially compatible, i.e., phase-separated, under conditions within the body. The multifunctional chain extender is, in one embodiment, an aliphatic molecule. In a preferred embodiment, the resulting multiblock copolymer of the present invention has the structure of formula (1):

[0066] [ka]

[0067] In the formula, R 1 is part of the prepolymer (A) segment, which is part of phase (A), and may be an amorphous polyester, amorphous polyetherester, or amorphous polycarbonate; or may be an amorphous prepolymer obtained from a combination of ester, ether, and / or carbonate groups. H is the midblock of the prepolymer (A) segment and is derived from a water-soluble polymer. The block derived from the water-soluble polymer may be amorphous or semi-crystalline at room temperature. However, the block H introduced into the prepolymer (A) segment becomes amorphous under physiological conditions. The water-soluble polymer is selected from the group consisting of polyethers such as polyethylene glycol (PEG), polytetramethylene oxide (PTMO), and polypropylene glycol (PPG), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinylcaprolactam, poly(hydroxyethyl methacrylate) (poly-(HEMA)), polyphosphazene, or copolymers of these polymers. In one embodiment, H is PEG, and R is PEG. 1 It is a ring-opening polymerization initiator of a cyclic monomer forming

[0068] R 2 are prepolymer (B) segments and contribute mainly or completely to phase (B). 2 Phase R may be a crystalline or semi-crystalline polyester, polyetherester, polycarbonate or polyanhydride; or a prepolymer combining ester, ether, anhydride and / or carbonate groups. 2 A portion of R may be amorphous. 2 This part of contributes to phase (A). 1 and R 2 are not the same in one embodiment. The variable z is 0 or a positive integer. The variables x and y are both positive integers.

[0069] Optionally, segment R 3 This segment is derived from a water-soluble polymer selected from the group of polymers described for H.3 becomes part of the amorphous phase (A) under physiological conditions. 3 When present, the multiblock copolymer of the present invention includes a water-soluble polymer as an additional prepolymer. In one embodiment, the water-soluble polymer is selected from the group consisting of polyethers such as polyethylene glycol (PEG), polytetramethylene oxide (PTMO), and polypropylene glycol (PPG), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinylcarprolactam, poly(hydroxymethyl methacrylate) (poly-(HEMA)), polyphosphazenes, polyorthoesters, polyorthoesteramides, or copolymers of these polymers. For example, the additional water-soluble polymer segment can be derived from PEG having an Mn of 150 to 5000 g / mol. The additional prepolymer derived from a water-soluble polymer can be suitably present in the multiblock copolymer in an amount of 60% or less, e.g., 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the total weight of the multiblock copolymer. The amount of additional water-soluble polymer segments can be 0.1% or more, such as 1% or more, or 2% or more, 3% or more, 4% or more, or 5% or more of the total weight of the multi-block copolymer.

[0070] R 4 is derived from a chain extender and consists of an aliphatic C2 to C8 alkylene group, optionally C1 to C 10 The aliphatic group is substituted with an alkylene, and the aliphatic group is linear or cyclic. 4 In one embodiment, is a butylene, —(CH2)4— group. 10 The alkylene side groups may contain protected S, N, P, or O moieties. Chain extenders containing aromatic groups are generally not suitable because they can produce undesirable decomposition products. Therefore, aliphatic chain extenders are preferred.

[0071] Q 1 ~Q 6 Q is the linking unit obtained by reacting the prepolymer with a polyfunctional chain extender. 1 ~Q6 may each independently be selected from amines, urethanes, amides, carbonates, esters, and anhydrides. It is rare and generally not preferred for all linking groups Q to be different.

[0072] Typically, one chain extender may be used with three prepolymers having the same end group to give a copolymer of formula (1) having six similar linking groups.

[0073] Prepolymer R 1 and R 2 If Q has different ends, then there will be two groups Q, e.g., Q 1 and Q 2 is two connected segments R 1 The same is true for R 1 and R 2 When and are connected, Q 1 and Q 2 The example of formula (1) shows the result of the reaction with a difunctional chain extender and a difunctional prepolymer.

[0074] Referring to formula (1), the polyester of the present invention also comprises a segment (AB) r where "A" corresponds to prepolymer (A) segment A and "B" corresponds to prepolymer (B) segment (z=0). (AB) r In the formula (1), the A / B ratio (corresponding to x / y in formula (1)) may be 1:1 (unity) or away from unity. The prepolymers can be mixed in any desired amount and linked by a multifunctional chain extender, i.e., a compound with at least two functional groups that can be used to chemically link the prepolymers. In one embodiment, this is a bifunctional chain extender. When z is not 0, the random distribution of all segments is (ABC), where three different prepolymers (one segment derived from a water-soluble polymer such as PEG) are randomly distributed in all possible ratios. rcan be given by

[0075] The a and b (and optionally c) segments are (AB) r and (ABC) r The prepolymers formed in are linked by a multifunctional chain extender, which in one embodiment is a diisocyanate chain extender, but can be a diacid or diol compound. If the prepolymers all contain hydroxyl end groups and a diisocyanate chain extender is used, the linking units will be urethane groups. If one of the prepolymers is terminated with a carboxylic acid, the linking units will be amide groups. Structure (AB) r and (ABC) r Multi-block copolymers having the formula (I) can also be prepared by reacting a dicarboxylic acid terminated prepolymer with a diol chain extender, or vice versa (reaction of a diol terminated prepolymer with a diacid chain extender), using a coupling agent such as DCC (dicyclohexylcarbodiimide) to form an ester bond.

[0076] As previously mentioned, a randomly segmented copolymer refers to a copolymer having a random distribution (ie, non-alternating) of prepolymer (A) segments and prepolymer (B) segments.

[0077] The hydrolyzable segment R of formula (1) 1 -HR 1 is obtained by the reaction of prepolymer (A).

[0078] The prepolymer (A) may be prepared, for example, by ring-opening polymerization. Thus, the prepolymer (A) may be a hydrolyzable copolymer prepared by ring-opening polymerization initiated by a diol or diacid compound, and in one embodiment, has a random monomer distribution. In one embodiment, the diol compound is an aliphatic diol or a low molecular weight polyether such as PEG. By using the polyether as an initiator, it becomes part of the prepolymer (A) and can be further mixed with the prepolymer (A), thereby adding an additional hydrophilic segment R in formula (1). 3 The prepolymer (A) may be a hydrolyzable polyester, polyetherester, polycarbonate, polyestercarbonate, polyanhydride, or copolymer thereof. For example, the prepolymer (A) comprises the reaction product of ester-forming monomers selected from diols, dicarboxylic acids, and hydroxycarboxylic acids. The prepolymer (A) may comprise the reaction product of cyclic and / or acyclic monomers. Exemplary cyclic monomers include glycolide, L-lactide, D-lactide, D,L-lactide, ε-caprolactone, δ-valerolactone, trimethylene carbonate, tetramethylene carbonate, cyclic anhydrides such as 1,5-dioxepan-2-one, 1,4-dioxan-2-one (p-dioxanone), and / or oxepane-2,7-dione. In one embodiment, ε-caprolactone is used.

[0079] To meet the requirement of a Tg below 37°C, some of the above-mentioned monomers or combinations of monomers are preferred over others. For example, in one embodiment, a prepolymer (A) containing the monomer ε-caprolactone is combined with any of the other mentioned cyclic comonomers (glycolide, L-lactide, D-lactide, D,L-lactide, δ-valerolactone, trimethylene carbonate, 1,4-dioxane-2-one, and combinations thereof). This may itself lower the Tg. Alternatively, the prepolymer can be initiated with PEG having a molecular weight sufficient to lower the Tg of the multiblock copolymer.

[0080] When the prepolymer (A) contains poly(D,L-lactide), the L / D ratio of the lactide may be different from 1:1 (i.e., other than 50 / 50). For example, an L / D ratio between 85 / 15 and 15 / 85 will give a completely amorphous homopolymer. Furthermore, it is known that an excess of one isomer (L or D) over the other increases the Tg of poly(D,L-lactide). The other monomers mentioned above that constitute the amorphous phase may also be present in small amounts in the crystalline phase forming the prepolymer or block.

[0081] Furthermore, the prepolymer (A) can be based on (a mixture of) monomers of the condensed (non-cyclic) type, such as hydroxy acids (e.g., lactic acid, glycolic acid, hydroxybutyric acid), diacids (e.g., glutaric acid, adipic acid or succinic acid, sebacic acid), and diols such as ethylene glycol, diethylene glycol, 1,4-butanediol or 1,6-hexanediol, which form ester and / or anhydride hydrolyzable moieties.

[0082] Preferably, at least a portion of the prepolymer (A) is derived from a water-soluble polymer. The water-soluble polymer may include one or more selected from the group consisting of polyethers such as polyethylene glycol (PEG), polytetramethylene oxide (PTMO), and polypropylene glycol (PPG); polyvinyl alcohol (PVA); polyvinylpyrrolidone (PVP); polyvinylcaprolactam; poly(hydroxyethyl methacrylate) (poly-(HEMA)); polyphosphazene; polyorthoester; polyorthoesteramide; or copolymers of these polymers. In one embodiment, at least a portion of the prepolymer (A) is derived from PEG.

[0083] Some non-limiting examples of suitable prepolymer (A) segments include poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone), poly(D,L-lactide)-co-PEG-co-poly(D,L-lactide), poly(glycolide)-co-PEG-co-poly(glycolide), and poly(p-dioxanone)-co-PEG-co-poly(p-dioxanone).

[0084] In an optional addition, the prepolymer (A) segment may include, on each side of the water-soluble polymer, a copolymer of any of the above-mentioned monomers. Some non-limiting examples of such prepolymer (A) segments include [poly(ε-caprolactone-co-D,L-lactide)]-co-PEG-co-[poly(ε-caprolactone-co-D,L-lactide)], [poly(ε-caprolactone-co-glycolide)]-co-PEG-co-[poly(ε-caprolactone-co-glycolide)], [poly(ε-caprolactone-co-p-dioxanone)]-co-PEG-co-[poly(ε-caprolactone lactone-co-p-dioxanone)], [poly(D,L-lactide-co-glycolide)]-co-PEG-co-[poly(D,L-lactide-co-glycolide)], [poly(D,L-lactide-co-p-dioxanone)]-co-PEG-co-[poly(D,L-lactide-co-p-dioxanone)], and [poly(glycolide-co-p-dioxanone)]-co-PEG-co-[poly(glycolide-co-p-dioxanone)].

[0085] Preferably, 30% or more, for example, 40% or more, 50% or more, 60% or more, or 70% or more of the total weight of the prepolymer (A) is derived from the water-soluble polymer. Preferably, 95% or less, for example, 90% or less, or 85% or less of the total weight of the prepolymer (A) is derived from the water-soluble polymer.

[0086] The prepolymer (A) can further contain p-dioxanone. The introduction of p-dioxanone monomer in the prepolymer (A) segment can introduce additional crystallinity into the multiblock copolymer. The content of such p-dioxanone monomer in the prepolymer (A) can be 80% or less, for example, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less, based on the weight of the prepolymer (A). The content of p-dioxanone monomer in the prepolymer (A) can be 0.1% or more, for example, 1% or more, or 2% or more.

[0087] The prepolymer (A) can have an Mn of 500 g / mol or more, and in other embodiments, 1000 g / mol or more, 1500 g / mol or more, or 2000 g / mol or more. The length of the prepolymer must be selected to be as large as necessary to obtain good phase-separated morphology and good mechanical and thermal properties of the resulting copolymer. Typically, the Mn of the prepolymer (A) is 10,000 g / mol or less. In one embodiment, the content of the prepolymer (A) in the copolymer is 5 to 95% of the total weight of the multiblock copolymer; in other embodiments, the content of the prepolymer (A) in the copolymer is 10 to 90%, 25 to 80%, 40 to 70%, or 50 to 60%.

[0088] Segment R in Eq. (1) 2 may be obtained by reacting a prepolymer (B) derived from poly(p-dioxanone). Any further monomer present in the prepolymer (B) may be selected from L-lactide, D-lactide, hydroxybutyrate, glycolide and combinations thereof.

[0089] The prepolymer (B) segment comprises poly(p-dioxanone). Poly(p-dioxanone) can be synthesized by reacting p-dioxanone monomer in the presence of a suitable catalyst and polymerization initiator. Suitable polymerization initiators have been previously described herein.

[0090] The polymerization reaction may be carried out at a temperature of 10 to 120°C; in other embodiments, the reaction may be carried out at 50 to 100°C, 60 to 95°C, 70 to 90°C, or 75 to 85°C. The catalyst is a catalyst effective in promoting the polymerization reaction and may be suitably selected from the group consisting of tin octoate-based catalysts and tin titanate-based catalysts. A suitable catalyst is tin octoate (i.e., tin bis(2-ethylhexanoate)). The molar ratio of monomer to catalyst may be 20,000 or more, for example, 21,000 or more. The molar ratio of monomer to catalyst may be 35,000 or less, for example, 34,000 or less. In one embodiment, the reaction is carried out under a nitrogen atmosphere.

[0091] The prepolymer (B) segment comprises an XYX triblock copolymer, in which the block length of the poly(p-dioxanone) segment X, represented by p-dioxanone monomer units, is 7 or greater. The prepolymer (B) may have a number average molecular weight Mn of 1300 g / mol or greater, e.g., 1500 g / mol or greater, 2000 g / mol or greater, 2200 g / mol or greater, or 2500 g / mol or greater. The prepolymer (B) may have a number average molecular weight Mn of 7200 g / mol or less, e.g., 5000 g / mol or less, 4500 g / mol or less, 4000 g / mol or less, or 3200 g / mol or less.

[0092] Prepolymer (B) can have a weight average molecular weight Mw of 1800 g / mol or more, for example, 2100 g / mol or more, 2600 g / mol or more, or 3000 g / mol or more. Prepolymer (B) can have a weight average molecular weight Mw of 10080 g / mol or less, 7000 g / mol or less, for example, 6300 g / mol or less, 5600 g / mol or less, or 4200 g / mol or less.

[0093] Suitably, 70% or more of the total weight of the prepolymer (B) segments can be poly(p-dioxanone). In one embodiment, 80% or more of the total weight of the prepolymer (B) segments can be poly(p-dioxanone). In another embodiment, 85% or more, 90% or more, or 95% or more of the total weight of the prepolymer (B) segments can be poly(p-dioxanone). In one embodiment, 80% or more of the total weight of the X segments is poly(p-dioxanone). In another embodiment, 85% or more, 90% or more, or 95% or more of the total weight of the X segments is poly(p-dioxanone). In one embodiment, the X segments consist of poly(p-dioxanone).

[0094] The content of prepolymer (B) in the copolymer may be 10 to 90% of the total weight of the multi-block copolymer. The content of prepolymer (B) in the copolymer can be, for example, 25 to 90%, 25 to 70%, or 30 to 50% of the total weight of the multi-block copolymer. Such a content generally results in a desired material with good physical (e.g., swelling) and degradation properties at the application temperature (i.e., about 37°C for medical applications).

[0095] In one embodiment, the prepolymers are linear and random (co)polyesters, polyester-carbonates, polyetheresters, or polyanhydrides with reactive end groups. These end groups may be hydroxyl or carboxyl groups. Dihydroxy-terminated copolymers are preferred, but hydroxy-carboxyl or dicarboxyl-terminated polymers can also be used. If the polymer must be linear, it can be prepared using a difunctional component (diol) as the initiator, but star-shaped polyesters can be obtained if a trifunctional or higher polyol is used. The diol in prepolymer (A) can be an aliphatic diol or a low molecular weight polyether.

[0096] In one embodiment, the prepolymer synthesis by ring-opening polymerization is carried out in the presence of a catalyst. A suitable catalyst is Sn(Oct)2 with an M / I ratio of 5,000 to 30,000 (M / I is the ratio of monomer to initiator). Alternatively, the prepolymer can be synthesized without a catalyst.

[0097] The conditions for preparing the polyesters, polycarbonates and polyanhydrides are known in the art.

[0098] The multi-block copolymer of the present invention may suitably comprise a water-soluble polymer (e.g., poly(ethylene glycol)) in an amount of 3 to 45% by total weight of the multi-block copolymer, for example, 4 to 40% by total weight of the multi-block copolymer.

[0099] The multi-block copolymer of the present invention may suitably contain poly(p-dioxanone) in an amount of 30 to 70% by total weight of the multi-block copolymer, for example, 35 to 65%, or 40 to 60% by total weight of the multi-block copolymer.

[0100] The copolymers of the present invention are generally linear. However, it is also possible to prepare branched copolymers. These non-linear copolymers of the present invention may be obtained by using trifunctional (or higher) chain extenders, such as tri-isocyanates. Branched copolymers can exhibit improved creep properties.

[0101] In one embodiment, the multi-block copolymer of the present invention is a poly(ether ester) multi-block copolymer, wherein the prepolymer (A) segment comprises:

[0102] [ka]

[0103] [ka]

[0104] [ka]

[0105] and

[0106] [ka]

[0107] and one or more selected from the group consisting of

[0108] The prepolymer (A) segment is

[0109] [ka]

[0110] and

[0111] The prepolymer (B) segment is

[0112] [ka]

[0113] Includes.

[0114] The prepolymer (A) segment is, for example,

[0115] [ka]

[0116] or

[0117] [ka]

[0118] where n is 4 to 115, for example, 13 to 70 or 20 to 46.

[0119] In one embodiment, the thermoplastic multi-block copolymer of the present invention is 1 R 2 n R 3 ) q ] r [(R 4 p R 5 R 6 p )] s where R 1 and R 3 But independently,

[0120] [ka]

[0121] [ka]

[0122] [ka]

[0123] and

[0124] [ka]

[0125] and R 2 but,

[0126] [ka]

[0127] and R 4 and R 6 However, respectively,

[0128] [ka]

[0129] is.

[0130] R 2 The repeating number of the moiety, n, is 4 to 120; R 4 and R 6 The number of repetitions of the part, p, is 7 or more; (R 1 R 2 n R 3 The molecular weight of the ) block, q, is 400 to 10,000 g / mol; and the ratio of the prepolymer (A) segment to the prepolymer (B) segment, r / s, is 0.1 to 2.5.

[0131] In this notation, n is R 2 is the number of repetitions of the part, and q is (R 1 R 2 n R 3 ) is the (number average) molecular weight of the block, and r is (R 1 R 2 n R 3 ) q is the weight percent of the block, and p is R 4 and R 6 is the number of repetitions of the part, and s is (R 4 p R 5 R 6 p ) is the weight percent of the block.

[0132] Suitably, n may be 4 to 120, for example, 13 to 70, and more preferably 20 to 46.

[0133] Preferably, p is 7 or greater, for example, 8 or greater, 9 or greater, 10 or greater, 11 or greater, 12 or greater, or 14 or greater. The upper limit of p is not particularly important, but may be, for example, 35 or less, for example, 30 or less, 25 or less, 20 or less, 15 or less, or 14 or less.

[0134] Suitably, q may be 400 to 10,000 g / mol, for example, 600 to 8,000 g / mol, 1,000 to 6,000 g / mol, 1,200 to 5,000 g / mol, 1,400 to 4,000 g / mol, 1,600 to 3,000 g / mol, or 1,800 to 2,200 g / mol.

[0135] Suitably, r may be 20 to 80, for example, 30 to 75, 40 to 70, or 50 to 65.

[0136] Suitably, s may be 20 to 80, for example, 25 to 70, 30 to 60, or 35 to 50.

[0137] (R 4 p R 5 R 6 p The number average molecular weight of the (B) block (corresponding to the prepolymer (B) segment) may be 1300 to 7200 g / mol, preferably 1300 to 5000 g / mol, more preferably 1500 to 4500 g / mol, and most preferably 2000 to 4000 g / mol, for example, 2200 to 3200 g / mol.

[0138] (R 4 p R 5 R 6 p The weight average molecular weight of the (B) block (corresponding to the prepolymer (B) segment) can be 1800 to 10080 g / mol, 1800 to 7000 g / mol, for example, 2100 to 6300 g / mol, 2600 to 5600 g / mol, or 3000 to 4200 g / mol.

[0139] In a further aspect, the present invention relates to a method for preparing the phase-separated thermoplastic multi-block copolymer of the present invention, said method comprising a chain extension reaction of prepolymer (A) and prepolymer (B) in the presence of a multifunctional chain extender, thereby obtaining a randomly segmented multi-block copolymer.

[0140] Structure (AB) r and (ABC) r The segmented multi-block copolymer having the segment R 1 , H and R 2 , and optionally R 3 A mixture of prepolymers containing monomers forming the hard and soft segments of Structure (AB) can be prepared by chain extending the mixture in the desired ratio with an equivalent amount of a multifunctional chain extender, which in one embodiment is an aliphatic molecule such as 1,4-butane diisocyanate (BDI) or other diisocyanate. r and (ABC) r In one embodiment, the segmented copolymer is prepared in solution. Preferably, the prepolymer(s) are dissolved in an inert organic solvent, and the chain extender is added neat or in solution. The polymerization temperature can be equal to or lower than the maximum phase transition temperature of the prepolymer. The coupling reaction with dicyclohexylcarbodiimide (DCC) is carried out in solution in one embodiment. Two (or three) prepolymers, all diol- or diacid-terminated, may be mixed in solution with the diacid- or diol-terminated chain extender, respectively, followed by the addition of DCC.

[0141] The polymerization is carried out for a time sufficient to obtain an intrinsic viscosity of the copolymer of 0.1 dL / g or greater (measured in chloroform at 25°C). Low polymerization temperatures and short polymerization times prevent transesterification so that a phase-separated morphology is obtained, with the monomer distribution being the same as in the prepolymer from which the copolymer is constructed. In contrast, high molecular weight random copolymers must be prepared with longer reaction times to achieve complete incorporation of the prepolymer. Longer reaction times cause transesterification reactions, resulting in a more random (i.e., less blocky) monomer distribution.

[0142] Bulk chain-extended materials can also be produced in situ in an extruder.

[0143] If the chain extender is a difunctional aliphatic molecule and the prepolymer is linear, a linear copolymer is produced. If one reactant (either the chain extender or at least one prepolymer) or both has more than two functional groups, a branched structure can be obtained at a sufficiently low conversion. The chain extender can be a difunctional aliphatic chain extender, and in one embodiment, can be a diisocyanate such as 1,4-butane diisocyanate.

[0144] The combination of prepolymers or monomers forming the crystalline and amorphous phases is selected to obtain a phase-separated segmented or block copolyester or polyestercarbonate having the desired degradation, swelling, physical, and thermal properties. Typically, the intrinsic viscosity is greater than 0.1 dL / g and less than 10 dL / g (measured in chloroform at 25° C.), in one embodiment between 0.1 and 2 dL / g, and in another embodiment between 0.2 and 1 dL / g.

[0145] In a further aspect, the present invention relates to a method for preparing a biodegradable phase-separated thermoplastic multi-block copolymer, said method comprising: i) carrying out a chain extension reaction of prepolymer (A) and prepolymer (B) in the presence of a polyfunctional chain extender, wherein prepolymers (A) and (B) are both terminated with a diol or a diacid, and the chain extender is terminated with a dicarboxylic acid, a diisocyanate, or a diol; or ii) carrying out a chain extension reaction using a coupling agent, wherein prepolymers (A) and (B) are both terminated with a diol or a diacid, and the coupling agent is, in one embodiment, dicyclohexylcarbodiimide; Including, The prepolymer (B) segment comprises an XYX triblock copolymer, wherein: Y is a polymerization initiator, and X is a poly(p-dioxanone) segment having a block length of 7 or more represented by p-dioxanone monomer units.

[0146] The multiblock segmented copolymers can be formed into formulations of various shapes and sizes using any known technique, such as solvent extraction / evaporation-based emulsion processes, extrusion, molding, solvent casting, spray drying, spray freeze drying, electrospinning, or lyophilization. The latter technique is used to form porous materials. Porosity can be controlled by adding cosolvents, nonsolvents, and / or leachables. The copolymers can be processed into microspheres, microparticles, nanospheres, rods, films, sheets, sprays, tubes, membranes, meshes, fibers, plugs, coatings, and other articles (solid or porous). Products can be solid, hollow, or (micro)porous. For example, a wide range of biomedical implants can be manufactured for applications such as wound healing, skin repair, nerve regeneration, vascular grafts, drug delivery, meniscus reconstruction, tissue engineering, surgical device coatings, ligament and tendon regeneration, dental, and orthopedic repair. The copolymers can be used alone or blended and / or coextruded with other absorbable or nonabsorbable polymers.

[0147] Additionally, the copolymers can be used in pharmaceutical applications, e.g., for drug delivery, in the form of, e.g., microspheres, nanoparticles, solid implants, gels, coatings, films, sheets, sprays, tubes, membranes, meshes, fibers, plugs, and other configurations.

[0148] As shown in the examples below, the materials of the present invention have improved properties, including thermal, mechanical and processing properties, compared to copolymers described in the prior art.

[0149] In yet another aspect, the present invention relates to a composition for delivering at least one bioactive compound (e.g., a biologically active small molecule, protein, or peptide) to a host, the composition comprising the at least one bioactive compound encapsulated in a matrix, the matrix comprising at least one phase-separated thermoplastic multi-block copolymer described herein.

[0150] The biodegradable multi-block copolymers of the present invention are particularly suitable as delivery vehicles for polypeptides, allowing for the controlled release of the polypeptide from the matrix into its environment (eg, within the body of a subject).

[0151] The multi-block copolymers of the present invention offer many options for tailoring the release profile of the delivery composition for a particular application. The release rate of the bioactive compound can be increased, for example, by: Keeping the molecular weight of prepolymer (A) constant, increasing the molecular weight of the water-soluble polymer in prepolymer (A) Increasing the molar ratio of prepolymer (A) to prepolymer (B) Increasing the monomer content in the prepolymer (A) that gives a polymer that degrades faster, for example by substituting ε-caprolactone with D,L-lactide or glycolide, or by substituting D,L-lactide with glycolide. Decreasing the molecular weight of prepolymer (B) while keeping the molar ratio of prepolymer (A) to prepolymer (B) constant (this increases the weight percentage of prepolymer (A) and also decreases the Tm of prepolymer (B) and the total amount of crystalline phase present). Decreasing the molecular weight of the prepolymer (A) while keeping the molecular weight of the water-soluble polymer and the molar ratio of prepolymer (A) to prepolymer (B) constant, and / or Increasing the content of water-soluble polymers by using an additional third segment derived from a water-soluble polymer.

[0152] The release rate can also be reduced by the reverse of the above modifications, or as follows. Increasing the Tm of segment B The content of water-soluble polymer is maintained constant or decreased by using an additional third segment derived from a water-soluble polymer diol using a diisocyanate as a chain extender. The water-soluble polymer in the third segment is constructed into a multi-block copolymer with slowly degrading urethane bonds compared to the faster degrading ester bonds of the water-soluble polymer in prepolymer (A).

[0153] For example, biologically active compounds that may be included in the multiblock copolymer matrix of [poly(D,L-lactide)-co-PEG-co-poly(D,L-lactide)]-b-[poly(p-dioxanone)], [poly(glycolide)-co-PEG-co-poly(glycolide)]-b-[poly(p-dioxanone)], or [poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone)]-b-[poly(p-dioxanone)], or [poly(ε-caprolactone)-co-D,L-lactide)-co-PEG-co-poly(ε-caprolactone-co-D,L-lactide)]-b-[poly(p-dioxanone)] matrix include, but are not limited to, non-peptides, non-protein small molecule drugs generally having a molecular weight of 1000 Da or less, and biologically active polypeptides.

[0154] Small molecule drugs are incorporated into multiblock copolymer matrices (e.g., [poly(D,L-lactide)-co-PEG-co-poly(D,L-lactide)]-b-[poly(p-dioxanone)], [poly(glycolide)-co-PEG-co-poly(glycolide)]-b-[poly(p-dioxanone)], [poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone)]-b-[poly(p-dioxanone)], or [poly(ε-caprolactone)]-co-PEG-co-poly(ε-caprolactone)]-b-[poly(p-dioxanone)]). When included in a poly(ε-caprolactone-co-D,L-lactide)-co-PEG-co-poly(ε-caprolactone-co-D,L-lactide)-b-[poly(p-dioxanone)] matrix), the PEG component of the copolymer has a molecular weight of 200-1500 g / mol in one embodiment, and 600-1000 g / mol in another embodiment, and is present in the copolymer in an amount of 5-20% of the total weight of the copolymer, or 5-10% of the total weight of the copolymer. The at least one small drug molecule may be present in the matrix in an amount of 0.1-80% of the combined weight of the matrix and the at least one small drug molecule, in one embodiment 1.0-40% and in another embodiment 5-20%. If it is desired to increase the hydrophilicity of the multi-block copolymer, thereby increasing the rate of degradation of the copolymer and the release rate of the incorporated bioactive compound, the copolymer may be modified by substituting some or all of the D,L-lactide in the hydrophilic prepolymer (A) segment with glycolide, and / or by using a higher molecular weight PEG component or by increasing the weight fraction of the PEG component in the prepolymer (A) segment. If it is desired to decrease the hydrophilicity of the polymer, thereby decreasing the rate of degradation of the copolymer and the release rate of the incorporated bioactive compound, the copolymer may be modified by substituting some or all of the D,L-lactide in the hydrophilic prepolymer (A) segment with ε-caprolactone, and / or by using a lower molecular weight PEG component or by decreasing the weight fraction of the PEG component in the prepolymer (A) segment.

[0155] Polypeptides consist of amino acids linked by peptide bonds. Short polypeptides are also called peptides, while longer polypeptides are typically called proteins. By convention, polypeptide chains short enough to be synthesized synthetically from their constituent amino acids are called peptides rather than proteins. However, with the advent of better synthetic techniques, polypeptides of several hundred amino acids can be produced, including complete proteins such as ubiquitin. Another convention informally defines polypeptides as those approximately 50 amino acids long. This definition is somewhat arbitrary. Long polypeptides, such as the amyloid beta peptide associated with Alzheimer's disease, can be considered proteins, while small proteins, such as insulin, can be considered peptides. In any event, those skilled in the art will understand that essentially any type of polypeptide can be encapsulated and subsequently released from the copolymer matrix.

[0156] In one embodiment, the compositions of the present invention comprise a bioactive peptide or protein.

[0157] The size of the polypeptide(s) may vary. In one embodiment, the polypeptide has a molecular weight of 10,000 Da or less. Polypeptides of such size are particularly suitable for encapsulation in a copolymer matrix comprising PEG, as a segment of prepolymer (A) and / or as an additional prepolymer, said PEG having a number average molecular weight of 400-3,000 g / mol, or in another embodiment 600-1,500 g / mol. Alternatively or additionally, the PEG may be present in an amount of 5-60%, or in another embodiment 5-40%, of the total weight of the copolymer.

[0158] In another embodiment, the polypeptide is a bioactive protein having a molecular weight of 10,000 Da or greater. These larger polypeptides are encapsulated in a copolymer matrix comprising PEG, in one embodiment, as a segment of prepolymer (A) and / or as an additional prepolymer, the PEG having a number average molecular weight of 600-5,000 g / mol, or in another embodiment, 1,000-3,000 g / mol. Alternatively or additionally, the PEG can be present in an amount of 5-70%, or in another embodiment, 10-50%, of the total weight of the copolymer.

[0159] The compositions of the present invention can have any desired appearance or shape. In one embodiment, the multi-block copolymers of the present invention are fabricated in the form of microspheres, microparticles, sprays, implants, coatings, gels, films, foils, sheets, membranes, or rods.

[0160] One particular embodiment relates to a composition in the form of microspheres. Microspheres are generally minute spherical particles with a diameter of less than 1000 μm that contain a bioactive compound. Microspheres may be homogeneous or monolithic, with the bioactive compound dissolved or dispersed throughout a polymer matrix. Microspheres may also be reservoir-type, with the bioactive compound in a mononuclear or polynuclear state surrounded by a polymer. When the bioactive compound is a small, water-soluble drug, the drug may first be dispersed in a hydrophobic or lipophilic excipient, and the mixture is then dispersed in the polymer matrix in the form of particles, droplets, or a microsuspension. Microspheres can then be formed from the emulsion.

[0161] Microspheres may be prepared by techniques known to those skilled in the art, including, but not limited to, droplet formation, solvent extraction / evaporation, spray drying, or spray freeze drying techniques.

[0162] In one embodiment, the microspheres are prepared by a solvent extraction / evaporation technique that involves dissolving the multi-block copolymer in an organic solvent such as dichloromethane and emulsifying the multi-block copolymer solution in an aqueous phase containing an emulsifier such as polyvinyl alcohol (as described, inter alia, in Okada, Adv. Drug Del. Rev. 1997, 28(1), 43-70).

[0163] The properties of the microspheres thus formed, such as particle size, porosity, drug loading, etc., depend on process parameters such as the viscosity or concentration of the aqueous polyvinyl alcohol phase, the concentration of the multiblock copolymer solution, the ratio of dichloromethane to aqueous active solution, the ratio of primary emulsion to polyvinyl alcohol phase, and the stirring speed.

[0164] When the microspheres are formed by spray drying, a low concentration of the multi-block copolymer is used, such as 0.5-5% of the total weight of the solution, in one embodiment about 2%, in an organic solvent such as dichloromethane. Spray drying generally results in the formation of porous, irregularly shaped particles.

[0165] When the microspheres are formed, the bioactive compound is encapsulated in the microspheres or microparticles. Generally, when encapsulating lipophilic compounds using the solvent extraction / evaporation technique, the compound is first dissolved in a solution of a multiblock copolymer in an organic solvent such as dichloromethane or ethyl acetate. The organic solution is then emulsified in an aqueous polyvinyl alcohol solution to obtain an oil-in-water (O / W) emulsion. The organic solvent is then extracted into the aqueous phase and evaporated, solidifying the microspheres.

[0166] Generally, when encapsulating a water-soluble compound using the solvent evaporation technique, an aqueous solution of the compound is first emulsified in a solution of a multiblock copolymer in an organic solvent such as dichloromethane. This primary emulsion is then emulsified in an aqueous polyvinyl alcohol solution to obtain a water-in-oil-in-water (W / O / W) emulsion. Similar to the O / W process route, an organic solvent such as dichloromethane or ethyl acetate is then extracted, resulting in coagulation of the microspheres. Alternatively, a water-soluble drug can be directly dispersed in a solution of the multiblock copolymer in an organic solvent. The resulting dispersion is then emulsified in an aqueous solution containing a surfactant such as polyvinyl alcohol to obtain a solid-in-oil-in-water (S / O / W) emulsion. Similar to the O / W process route, the organic solvent is then extracted, resulting in coagulation of the microspheres.

[0167] When encapsulating water-soluble compounds using the W / O / W and S / O / W emulsification routes, it can be difficult to obtain microspheres with sufficient encapsulation efficiency. Due to the water-solubility characteristics of the compound, a portion of the compound may be lost to the aqueous extraction medium, such as an aqueous polyvinyl alcohol solution. To prevent the compound in the internal aqueous phase from diffusing into the external aqueous phase, a thickener such as gelatin may be used in the internal aqueous phase. Additionally, additives may be added to the external aqueous phase to reduce the solubility of the compound in the external aqueous phase. For this purpose, salts may be used or the pH may be adjusted.

[0168] The water-in-oil-in-oil (W / O / O) or solid-in-oil-in-oil (S / O / O) emulsification routes offer interesting alternatives for obtaining microspheres with sufficient encapsulation efficiency. In the W / O / O process, the bioactive compound is dissolved in an aqueous solution and emulsified with a solution of a polymer, typically in an organic solvent such as dichloromethane or ethyl acetate, similar to the W / O / W process. A polymeric precipitant, such as silicone oil, is then slowly added with stirring to form embryonic microparticles, which are then poured into heptane or hexane to extract the silicone oil and organic solvent and solidify the microspheres. The microparticles may be recovered by vacuum filtration, rinsed with additional solvent, and dried under vacuum. In the S / O / O emulsification route, the bioactive compound is dispersed as a solid powder in a solution of a polymer in an organic solvent such as dichloromethane or ethyl acetate, similar to the S / O / W process. A polymeric precipitant, such as silicone oil, is then slowly added with stirring to form embryonic microparticles, which are then poured into heptane or hexane to extract the silicone oil and dichloromethane and solidify the microspheres.

[0169] To prevent loss of protein activity during processing into microspheres, stabilizers may be added to the aqueous protein solution. Examples of such stabilizers include polyvinyl alcohol, Tween® / polysorbatum, human serum albumin, gelatin, and carbohydrates such as trehalose, inulin, and sucrose.

[0170] When using the spray drying technique, an aqueous solution of the compound is emulsified in a solution of the copolymer in an organic solvent, such as methylene chloride, as described above, and the water-in-oil emulsion is then spray-dried using a spray dryer.

[0171] In further embodiments, the compositions of the present invention are in the form of a coating, an injectable gel, an implant (such as an injectable implant), or a coated implant. The composition in the form of a coating can be applied, for example, as a drug-eluting coating on a medical implant such as a vascular or urinary stent, an orthopedic prosthesis, or an ocular implant.

[0172] Bioactive compounds may be incorporated into injectable solid implants by extrusion. Typically, the compound and multiblock copolymer powder are physically mixed, and the resulting powder blend is introduced into an extruder, where it is heated and processed to obtain a formulation with the desired shape and dimensions, such as a small-diameter cylindrical rod. Instead of physically mixing the compound and multiblock copolymer powder, the compound and polymer may be co-dissolved in a suitable solvent, or a dispersion of the compound in a polymer solution may be prepared in a suitable solvent, followed by lyophilization and extrusion of the lyophilized powder. The latter generally improves the blend homogeneity and content uniformity of the implant.

[0173] In yet another aspect, the present invention relates to a method of delivering a biologically active compound to a subject in need thereof, said method comprising administering to said subject an effective amount of a composition as defined herein.

[0174] The subject is typically a mammal, preferably a human. However, veterinary uses of the present invention are also encompassed. The method can have therapeutic, prophylactic, and / or cosmetic purposes. Any appropriate administration form can be selected depending on the situation. For example, administration may include parenteral, oral, intra-arterial, intra-articular, intravenous, intraocular, epidural, intrathecal, intramuscular, intraperitoneal, intravenous, intravaginal, rectal, topical, or subcutaneous administration of the composition. In one embodiment, the present invention provides a method for delivering a biologically active polypeptide of interest to a subject in need thereof, the method comprising administering to the subject an effective amount of a composition of the present invention, the composition being in the form of a microsphere, an injectable implant, or an in situ-forming gel, and the composition being administered intraocularly, intra-arterially, intramuscularly, or subcutaneously.

[0175] For topical administration, the microspheres may be contained in a gel, cream, or ointment, and may be coated with a barrier if desired. Thus, the microspheres may contain one or more bioactive compounds used in the treatment of skin disorders such as psoriasis, eczema, seborrhea, and dermatitis.

[0176] In another embodiment, the microspheres may be contained in a gel, such as a hyaluronic acid gel or a high molecular weight polysaccharide gel, which is particularly applicable to parenteral applications, such as during and after surgery.

[0177] For administration by injection, the microspheres may be contained in a pharmaceutical carrier such as water, saline (e.g., 0.9%), or a solution containing a surfactant in an amount of 0.1-0.5% w / v. Examples of surfactants that may be used include, but are not limited to, Tween 80 surfactant. The pharmaceutical carrier may further contain a viscosity enhancer such as sodium carboxymethylcellulose.

[0178] Such microspheres, when administered in combination with an acceptable pharmaceutical carrier, can be used to treat a variety of diseases or disorders, depending on the bioactive compound encapsulated.

[0179] In one aspect, provided herein is an injectable delivery system comprising the poly(ether ester) multi-block copolymers (PEE-MBCPs) provided herein.

[0180] The PEE-MBCP can be in the form of an implant. Such an implant can be a microsphere, a rod, a film, a PEE-MBCP depot, or a combination thereof. The PEE-MBCP can be in the form of a plurality of polymeric microspheres, each having a diameter of 20 μm or greater, the polymeric microspheres comprising the PEE-MBCP described herein. The polymeric microspheres can have a diameter of 20 μm or greater and 80 μm or less, for example, a diameter of 30 μm or greater and 70 μm or less. The polymeric microspheres can be monodisperse, having a coefficient of variation of about 25%. The injectable delivery system can further comprise a therapeutic agent or a pharmaceutically acceptable salt thereof. The therapeutic agent can be a small chemical entity, a protein, an antibody, a peptide, or an oligonucleotide, or a combination thereof. In addition, the injectable delivery system can further comprise a pharmaceutically acceptable excipient. An example of an injectable delivery system comprises PEE-MBCP (also abbreviated as 60CP10C20-D25) composed of a poly(ε-caprolactone)-co-PEG1000-co-poly(ε-caprolactone) prepolymer (A) block combined with a poly(p-dioxanone) prepolymer (B) block having a molecular weight of approximately 2500 g / mol in a block ratio of 60 / 40 wt%, which may optionally contain small chemicals, proteins, antibodies, peptides, or oligonucleotides, or combinations thereof, as active ingredients.

[0181] The present invention has been described with reference to various embodiments, compositions, and methods. Those skilled in the art will appreciate that features of the various embodiments, compositions, and methods can be combined with one another.

[0182] All references cited herein are incorporated by reference in their entirety as if each reference was individually and specifically indicated to be incorporated by reference.

[0183] The use of the terms "a," "an," and "the" and similar referents in the context of describing the present invention (particularly in the context of the claims) is to be construed as including both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise stated herein, and each separate value is incorporated herein as if set forth individually herein. The use of any and all examples or exemplary language (e.g., "e.g., "etc.") provided herein is intended merely to facilitate a better understanding of the invention and does not limit the scope of the invention unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. For purposes of the description and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like are to be understood in all instances to be modified by the term "about." Also, all ranges include any combination of the maximum and minimum points disclosed, and include any intermediate ranges that may or may not be specifically recited herein.

[0184] Although, for purposes of clarity and conciseness of description, features are described herein as part of the same or separate embodiments, it will be understood that the scope of the present invention may include embodiments having all or any combination of the described features. [Example]

[0185] The present invention is further illustrated by the following non-limiting examples.

[0186] In the following examples, various biodegradable semi-crystalline phase-separated multiblock copolymers were synthesized and evaluated for their processing, drug release, and erosion properties. The polymers were composed of a crystalline p-dioxanone-based hard prepolymer (B) segment with a melting point (Tm) and a hydrophilic poly(ethylene glycol) (PEG)-based prepolymer (A) segment with a glass transition temperature (Tg) below 37°C under physiological conditions. In the following examples, PEG is indicated by its molecular weight (MW). For example, PEG 1000 refers to PEG with a Mw of 1000 g / mol.

[0187] Example 1

[0188] PLGA polymers are most frequently used for sustained drug release and have been clinically proven to be safe in the body. Although PLGA polymers are quite versatile and their physicochemical properties can be tailored to suit different drug delivery needs, their suitability has been shown to be limited for protein delivery. Protein stability remains a major obstacle in delivering proteins with PLGA due to (1) the hydrophobic nature of the polymer and (2) the formation and accumulation of acidic degradation products within the polymer matrix, which leads to a decrease in in situ pH, potentially causing degradation and loss of bioactivity of any encapsulated protein. Proteins have also been shown to be chemically modified by (3) deamination or acylation within the PLGA matrix. Therefore, PLGA-based delivery systems are associated with all of the aforementioned issues, including (4) protein aggregation and (5) undesirable release kinetics.

[0189] Biodegradable phase-separated segmented multiblock copolymers (SynBiosys, InnoCore Technologies BV, Groningen, The Netherlands), disclosed in WO 2012 / 005594 and WO 2013 / 015685, have been developed for the delivery of structurally intact, biologically active peptides and proteins over extended periods of up to 3–6 months. SynBiosys multiblock copolymers typically consist of two distinct blocks of commonly used monomers, including D,L-lactide, glycolide, ε-caprolactone, and polyethylene glycol (PEG), copolymerized into a low-molecular-weight polymer (prepolymer), which are linked together with a diisocyanate, typically 1,4-butane diisocyanate. For example, the use of two chemically and physically distinct prepolymer blocks, consisting of hydrophilic amorphous and hydrophobic crystalline domains, results in phase-separated segmented multiblock copolymers that provide a mechanism for the extended release of drugs, including peptides and proteins. The hydrophilic amorphous block typically contains a high content of polyethylene glycol (PEG), which leads to swelling of the multi-block copolymer under aqueous conditions, and the hydrophobic crystalline block acts as a physical crosslink.

[0190] As disclosed in WO 2012 / 005594, hydrophilic phase-separated segmented multiblock copolymers containing hydrophobic poly(ε-caprolactone)-based crystalline blocks enabled the long-term sustained release of peptides and proteins when processed into implants by hot-melt extrusion (Stankovic et al., Eur. J. Pharm. Sci. 2013, 49(4), 578-587). As disclosed in WO 2013 / 015685, hydrophilic phase-separated segmented multiblock copolymers containing hydrophobic poly(L-lactide)-based crystalline blocks have previously been shown to have highly beneficial properties for protein delivery. In particular, multiblock copolymers composed of poly(ε-caprolactone)-PEG-poly(ε-caprolactone)-based hydrophilic blocks combined with poly(L-lactide)-based crystalline blocks (PCL multiblock copolymers) have been found to exhibit promising properties for the long-term sustained release of structurally intact biologics when formulated into microparticles (Teekamp et al., Int. J. Pharm. 2017, 534(1-2), 229-236; Teekamp et al., J. Control Release 2018, 269, 258-265; Scheiner et al., ACS Omega 2019, 4(7), 11481-11492).

[0191] PCL multiblock copolymers were constructed by combining a crystalline poly(L-lactide) block (abbreviated as LL40) with a molecular weight (Mn) of 4000 g / mol and a hydrophilic poly(ε-caprolactone)-PEG1000-poly(ε-caprolactone) block (abbreviated as CP10C20) with a Mn of 2000 g / mol in various block ratios ranging from 20 / 80 (20CP10C20-LL40) to 50 / 50 (50CP10C20-LL40), and a PCL multiblock copolymer was constructed by combining a crystalline poly(L-lactide) block (abbreviated as LL40) with a hydrophilic poly(ε-caprolactone)-PEG1000-poly(ε-caprolactone) block (abbreviated as CP10C20) with a Mn of 4000 g / mol. PCL multiblock copolymers composed of a combination of hydrophilic poly(ε-caprolactone)-PEG3000-poly(ε-caprolactone) block (abbreviated as CP30C40) and a hydrophilic poly(ε-caprolactone) block in a weight ratio of 30 / 70 (30CP30C40-LL40) or 50 / 50 (50CP30C40-LL40) were found to be suitable for the sustained delivery of biologics of various molecular sizes, such as goserelin, lysozyme, bovine serum albumin, insulin-like growth factor-1, hepatocyte growth factor, and vascular endothelial growth factor.

[0192] Unfortunately, the 50CP10C20-LL40-based microspheres were found to degrade very slowly. Based on extrapolation of experimental data, the in vitro erosion time of 50CP10C20-LL40 microspheres was predicted to be 3–4 years (Figure 1) and at least 14–16 months in vivo. The slow erosion of PCL multiblock copolymers was confirmed for other PCL multiblock copolymers, such as 20CP10C20-LL40 and 30CP30C40-LL40, and was attributed to the slow hydrolysis of the crystalline poly(L-lactide) block.

[0193] SynBiosys PCL multiblock copolymers were redesigned to decrease the polymer erosion time, avoid polymer accumulation during repeated administration, and improve long-term local tolerability. To increase the erosion rate, both the CP10C20 amorphous block and the crystalline LL40 block were modified. The crystalline LL40 block was modified by: 1) partial replacement of L-lactide with D-lactide (L-MBCP concept), 2) use of a more hydrophilic initiator for the synthesis of the crystalline L-lactide block (I-MBCP concept), 3) use of a short stereocomplex crystalline block consisting of L-lactide and D-lactide (SC-MBCP concept), and 4) complete replacement of L-lactide with dioxanone (D-MBCP concept). The amorphous CP10C20 block was modified by changing the weight fraction and molecular weight of PEG, the length of the poly(ε-caprolactone) chain, and partial replacement of ε-caprolactone with DL-lactide. Finally, the ratio of the amorphous block to the crystalline block (block ratio) was changed.

[0194] L-MBCP polymer

[0195] The various L-MBCP-based polymers synthesized are listed in Table 1. The table shows L-MBCP polymers prepared by chain extension of crystalline lactide-based blocks with D-lactide / L-lactide ratios of 0 / 100 (PCL05), 1 / 99, 4 / 96, and 7 / 93 mol / mol with amorphous CP10C20 or poly(DL-lactide-co-ε-caprolactone)-PEG1000-poly(DL-lactide-co-ε-caprolactone) prepolymer (LCP10LC20) with DL-lactide / ε-caprolactone ratios (L / c ratios) of 0 / 100, 5 / 95, and 15 / 85 mol / mol.

[0196] [Table 1]

[0197] I-MBCP polymer

[0198] To prepare more hydrophilic L-lactide-based crystalline blocks, diethylene glycol (DEG) and triethylene glycol (TEG) were used as initiators instead of 1,4-butanediol. LL40 prepolymer blocks initiated with DEG and TEG were combined with either CP10C20 or LCP10LC20. Table 2 lists the DEG- and TEG-based I-MBCP polymers.

[0199] [Table 2]

[0200] D-MBCP polymer

[0201] Poly(p-dioxanone) was evaluated as an alternative to L-lactide-based crystalline blocks. Poly(p-dioxanone) is a crystalline polyester, but is more hydrophilic than poly(L-lactide). Low molecular weight polydioxane-based prepolymers were synthesized and chain-extended with CP10C20 and alternative caprolactone-PEG-based prepolymers with various PEG molecular weights and poly(ε-caprolactone) chain lengths. Table 3 lists the various D-MBCP polymers that were prepared.

[0202] [Table 3]

[0203] SC-MBCP polymer

[0204] SC-MBCP polymers were obtained by chain extension of amorphous prepolymers with a 50 / 50 wt% mixture of low molecular weight D-lactide prepolymers (DL15, DL20) and L-lactide prepolymers (LL15, LL20). The D-lactide and L-lactide blocks form highly crystalline blocks by stereocomplexation. The DL15 / LL15 or DL20 / LL20 prepolymer mixtures were combined with low molecular weight amorphous prepolymers consisting of CP10C20, LCP10LC20, and PEG600 (CP6C12, LCP6LC12) (Table 4).

[0205] [Table 4]

[0206] The synthesized L-MBCP, I-MBCP, SC-MBCP, and D-MBCP polymers were evaluated for their processability into polymer-only microspheres (particle size distribution, microscopic appearance, stickiness, lack of aggregation). The in vitro erosion kinetics of the polymers successfully processable into microspheres were further evaluated.

[0207] The particle size distribution of the microspheres was measured by laser diffraction. Microspheres were suspended in water until the transmittance was within the range of 70-90%, and the particle size distribution of the suspension was measured in the range of 10 nm to 5000 μm. The surface morphology of the microspheres was evaluated by scanning electron microscopy using a JEOL JCM-5000 Neoscope. A small amount of microspheres was attached to carbon conductive tape and coated with gold for 3 minutes. The samples were imaged using a 10 kV electron beam.

[0208] In vitro erosion of unloaded polymer-only microspheres was measured in 100 mM phosphate buffer, pH 7.4 (90–100 mg of microspheres in 10 ml). Samples were incubated at 37°C. At each sampling point, microspheres were harvested, lyophilized, and weighed.

[0209] Most polymers were highly processable, enabling the preparation of microspheres with narrow particle size distributions. However, polymers from the L-MBCP, I-MBCP, and SC-MBCP families exhibited very slow in vitro erosion (Figure 2). On the other hand, all multiblock copolymers based on poly(dioxanone) substitution of PLLA in the prepolymer (B) segment combined with hydrophilic poly(ε-caprolactone)-PEG-poly(ε-caprolactone) blocks (PCD multiblock copolymers) were found to erode significantly faster in vitro compared to all other multiblock copolymers (Figure 3).

[0210] The promising in vitro erosion properties of PCD multiblock copolymers were attributed to the replacement of poly( l -lactide)-based prepolymer (B) segments with poly( p -dioxanone) prepolymer (B) segments.

[0211] In the following examples, various biodegradable semi-crystalline phase-separated multiblock copolymers consisting of crystalline poly(p-dioxanone)-based hard prepolymer (B) segments with a melting point (Tm) and hydrophilic poly(ethylene glycol) (PEG)-based prepolymer (A) segments with a glass transition temperature (Tg) below 37°C under physiological conditions were synthesized and evaluated for processing into drug-loaded microparticles and implants, drug release characteristics, and erosion properties.

[0212] Example 2

[0213] This example describes the analytical methods used to analyze the prepolymers and multi-block copolymers. 1 H-NMR was performed at 500 MHz on a Bruker Avance DRX 500 MHz NMR spectrometer (B AV-500) equipped with a Bruker automatic sample changer (BACS 60) (Varian). The d1 wait time was set to 20 s, and the number of scans was 16. Spectra were recorded from 0 to 14 ppm. The conversion was 1The prepolymer Mn was determined by H-NMR and 1 Identification was performed using H-NMR. 1 H-NMR samples were prepared by adding 1.3 g of deuterated chloroform to 25 mg of polymer.

[0214] Intrinsic viscosity was measured using a Si Analytics Ubbelohde viscometer (DIN), type 0C, equipped with a Si Analytics viscometer containing a water bath. Measurements were performed in chloroform at 25 °C. The polymer concentration in chloroform was such that the relative viscosity was in the range of 1.2–2.0.

[0215] The p-dioxane, ethanol, and n-heptane contents were determined using a GC-FID headspace method. Measurements were performed on a GC-FID CombiSampler equipped with an Agilent column, DB-624 / 30 m / 0.53 mm. Samples were prepared in DMSO (dimethyl sulfoxide). The residual solvent contents were determined using p-dioxane, ethanol, and n-heptane calibration standards.

[0216] The thermal behavior of multiblock copolymers was characterized by modulated differential scanning calorimetry (MDSC) using a Q2000 MDSC (TA Instruments, Ghent, Belgium). Approximately 5–10 mg of dry material was accurately weighed and heated from −85°C to 120°C under a nitrogen atmosphere at a heating rate of 2°C / min with a modulation amplitude of + / −0.42°C every 80 seconds. The glass transition temperature (Tg, midpoint) and melting point (maximum of the endothermic peak, Tm), as well as the enthalpy of fusion (ΔHm), calculated from the surface area of ​​the melting endotherm, were determined from reverse heat flow. Temperature and enthalpy were calibrated with an indium standard.

[0217] Example 3

[0218] This example provides a procedure for preparing poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone) prepolymer (A). CL (CL = ε-caprolactone, Acros Organics) monomer was dried, distilled with CaH2 under reduced pressure, and stored under nitrogen atmosphere until further use. 1 This was confirmed by H-NMR.

[0219] PEG was weighed into a three-necked bottle under a nitrogen atmosphere and dried at 90 °C under reduced pressure for at least 16 hours. CL was added to the PEG under a nitrogen atmosphere, and the mixture was heated to 160 °C. Tin octoate (Sigma) was then added at a monomer-catalyst ratio of 5000-12000, and the mixture was magnetically stirred and reacted at 160 °C until the conversion reached >98%.

[0220] Poly(ε-caprolactone)-co-PEG with a target Mn of 2000 g / mol was prepared by ring-opening polymerization of ε-caprolactone using polyethylene glycol (PEG1000) with a molecular weight of 1000 g / mol as an initiator. 1000 A poly(ε-caprolactone)-co-poly(ε-caprolactone) prepolymer (abbreviated as ppCP10C20) was prepared. 500.9 g (2.00 mol) of PEG1000 (Merck, Emprove® Essential Ph Eur) was weighed into a three-necked bottle under nitrogen and dried at 90°C under reduced pressure for at least 16 hours. ε-Caprolactone (Acros Organics) was dried, distilled over CaH2 under reduced pressure, and stored under nitrogen. 495.9 g (4.34 mol) of ε-caprolactone was added to the PEG under nitrogen, and the mixture was heated to 160°C. 140.1 mg of tin octoate was added, and the mixture was magnetically stirred and reacted at 160°C for 73 hours. 1 H-NMR indicated approximately 100% monomer conversion. 1 The molecular weight measured by 1 H-NMR was 1980 g / mol.

[0221] Poly(ε-caprolactone)-co-PEG 1500-co-poly(ε-caprolactone) prepolymer (abbreviated as ppCP15C20) with a target Mn of 2000 g / mol was similarly prepared by ring-opening polymerization of ε-caprolactone using polyethylene glycol (PEG 1500) with a molecular weight of 1500 g / mol as the initiator. 152.6 g (0.10 mol) of PEG MW 1500 (Merck) was weighed into a three-necked bottle under nitrogen and dried at 90 °C under reduced pressure for at least 16 hours. 49.0 g (0.43 mol) of ε-caprolactone was added to the PEG under nitrogen, and the mixture was heated to 130 °C. 31.3 mg of tin octoate was added, and the mixture was allowed to react at 130 °C for approximately 192 hours with magnetic stirring. 1 H-NMR showed a monomer conversion of 97.1%. 1 The molecular weight measured by 1 H-NMR was 2000 g / mol.

[0222] Poly(ε-caprolactone)-co-PEG3000-co-poly(ε-caprolactone) prepolymer (abbreviated as ppCP30C40) with a target Mn of 4000 g / mol was similarly prepared by ring-opening polymerization of ε-caprolactone using polyethylene glycol (PEG3000) with a molecular weight of 3000 g / mol as the initiator. 183.54 g (61.2 mmol) of PEG MW 3000 (Merck) was weighed into a three-necked bottle under nitrogen and dried at 90 °C under reduced pressure for at least 16 hours. 61.22 g (0.54 mol) of ε-caprolactone was added to the PEG under nitrogen, and the mixture was heated to 160 °C. 25.1 mg of tin octoate was added, and the mixture was allowed to react at 160 °C for approximately 69 hours with magnetic stirring. 1 H-NMR showed a monomer conversion of 99.4%. 1 The molecular weight determined by H-NMR was 3970 g / mol. The experimental details and results obtained for the synthesis of poly(ε-caprolactone-co-PEG-co-poly(ε-caprolactone) prepolymer are listed in Table 5.

[0223] [Table 5]

[0224] Example 4

[0225] This example provides a procedure for preparing prepolymer (A) including poly(DL-lactide)-co-PEG-co-poly(DL-lactide), poly(ε-caprolactone-co-DL-lactide)-co-PEG1000-co-poly(ε-caprolactone-co-DL-lactide), and poly(p-dioxanone)-co-PEG1000-co-poly(p-dioxanone).

[0226] Poly(DL-lactide)-co-PEG200-co-poly(DL-lactide) prepolymer (abbreviated as ppLP2L20) with a target Mn of 2000 g / mol was prepared by ring-opening polymerization of DL-lactide using polyethylene glycol (PEG200) with a molecular weight of 200 g / mol as an initiator. 450.7 g (3.95 mol) of D,L-lactide (Purac) was weighed into a three-necked bottle under nitrogen and dried at 50°C under reduced pressure for at least 16 hours. 49.7 g (0.25 mol) of pre-dried PEG200 (Merck, EMPROVE® ESSENTIAL DAB 8) was added under nitrogen. The mixture was heated to 140°C. 59.6 mg of tin octoate was added, and the mixture was magnetically stirred and reacted at 140°C for 69 hours. 1 H-NMR showed a monomer conversion of 95.4%. 1 The molecular weight measured by 1 H-NMR was 2000 g / mol.

[0227] Poly(DL-lactide)-co-PEG600-co-poly(DL-lactide) prepolymer (abbreviated as ppLP6L12) with a target Mn of 1200 g / mol was prepared by ring-opening polymerization of DL-lactide using polyethylene glycol (PEG600) with a molecular weight of 600 g / mol as an initiator. 252.4 g (2.21 mol) of D,L-lactide (Purac) was weighed into a three-necked bottle under nitrogen and dried at 50°C under reduced pressure for at least 16 hours. 249.5 g (0.42 mol) of pre-dried PEG600 (Merck, EMPROVE® ESSENTIAL Ph Eur) was added under nitrogen. The mixture was heated to 140°C. 51.4 mg of tin octoate was added, and the mixture was magnetically stirred and reacted at 140°C for 22 hours. 1 H-NMR showed a monomer conversion of 96.0%. 1 The molecular weight measured by 1 H-NMR was 1190 g / mol.

[0228] Poly(DL-lactide)-co-PEG1000-co-poly(DL-lactide) prepolymer (abbreviated as ppLP10L20) with a target Mn of 2000 g / mol was prepared by ring-opening polymerization of DL-lactide using polyethylene glycol (PEG1000) with a molecular weight of 1000 g / mol as an initiator. 256.2 g (2.24 mol) of D,L-lactide (Purac) was weighed into a three-necked bottle under nitrogen and dried at 50°C under reduced pressure for at least 16 hours. 240.8 g (0.24 mol) of pre-dried PEG1000 (Merck, EMPROVE® ESSENTIAL Ph Eur) was added under nitrogen. The mixture was heated to 140°C. 71.1 mg of tin octoate was added, and the mixture was magnetically stirred and reacted at 140°C for 190 hours. 1 H-NMR showed a monomer conversion of 95.4%. 1 The molecular weight measured by 1 H-NMR was 1920 g / mol.

[0229] Poly(ε-caprolactone-co-DL-lactide)-co-PEG1000-co-poly(ε-caprolactone-co-DL-lactide) prepolymer (abbreviated as ppLCP10LC20) with a target Mn of 2000 g / mol was prepared by ring-opening copolymerization of ε-caprolactone and DL-lactide (L / C = 5 / 95 mol / mol) using polyethylene glycol (PEG1000) with a molecular weight of 1000 g / mol as initiator. 15.5 g (0.11 mol) of D,L-lactide (Purac) was weighed into a three-necked bottle under a nitrogen atmosphere and dried at 50 °C for at least 16 h under reduced pressure. 248.5 g (0.25 mol) of pre-dried PEG 1000 (Merck, EMPROVE® ESSENTIAL Ph Eur) was added together with 233.0 g (2.04 mol) of freshly distilled ε-caprolactone under a nitrogen atmosphere. The mixture was heated to 140° C. 69.8 mg of tin octoate was added, and the mixture was magnetically stirred and reacted at 140° C. for 120 hours. 1 H-NMR showed a monomer conversion of 98.8%. 1 The molecular weight measured by 1 H-NMR was 1980 g / mol.

[0230] Poly(p-dioxanone)-co-PEG1000-co-poly(p-dioxanone) (abbreviated as ppDP10D24) with a target Mn of 2400 g / mol was prepared by ring-opening polymerization of p-dioxanone using polyethylene glycol (PEG1000) with a molecular weight of 1000 g / mol as an initiator. 5.84 g (57.2 mmol) of freshly distilled p-dioxanone was added to 4.17 g (4.17 mmol) of pre-dried PEG1000 (Merck, EMPROVE® ESSENTIAL Ph Eur) in a three-neck flask, and the reaction mixture was heated to 80 °C. 4.1 mg of tin octoate was added, and the mixture was magnetically stirred and reacted at 80 °C for 265 h. 1 H-NMR indicated a monomer conversion of 75.1%. 1 The molecular weight measured by 1 H-NMR was 2410 g / mol.

[0231] The experimental details and results obtained for the synthesis of the prepolymers are listed in Table 6.

[0232] [Table 6]

[0233] Example 5

[0234] Poly(p-dioxanone) prepolymers with different molecular weights were synthesized in bulk via ring-opening polymerization initiated by 1,4-butanediol (BDO). BDO (Acros Organics) and p-dioxanone monomer (PDO, ≥99.5% purity, HBCChem) were distilled with CaH2 under reduced pressure and stored under nitrogen until further use. PDO was melted and introduced into a jacketed reactor under nitrogen. BDO was then added to PDO under nitrogen. The mixture was heated to 80 °C to obtain a clear molten liquid. Tin octoate (Sigma-Aldrich) was added as a solution to p-dioxane (Acros, dried and distilled) at a monomer-catalyst ratio of 23,000–33,000 to initiate the ring-opening polymerization. The mixture was mechanically stirred at 80 °C. Stirring was stopped when poly(p-dioxanone) solidified. Polymerization continued in the solid state, increasing the conversion to the target 80–90%. Table 7 lists the amount of PDO monomer, amount of BDO initiator, and amount of tin octoate catalyst used in the synthesis of poly(p-dioxanone) prepolymers with different molecular weights. Samples were taken from the bulk of the coagulated polymer. 1 The average conversion and molecular weight of the polymer were determined by H-NMR analysis. The polymerization was continued until the conversion reached 80% or higher, which varied from 80.0 to 92.7%. The number-average molecular weight of the poly(p-dioxanone) prepolymer (ppDxx) thus prepared varied from 1783 to 2806 g / mol. The poly(p-dioxanone) prepolymer was not isolated but remained in the reactor until further use.

[0235] [Table 7]

[0236] Example 6

[0237] This example describes the synthesis and analysis of [poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone)]-b-[poly(p-dioxanone)] multiblock copolymers.

[0238] [Poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone)]-b-[poly(p-dioxanone)] multiblock copolymers with various block ratios were prepared by chain extending ppDxx prepolymers with ppCP10C20, ppCP15C20, or ppCP30C40 prepolymers using 1,4-butanediisocyanate as the chain extender. First, ppDxx prepolymers were prepared in situ in a jacketed reactor as previously described, followed by the addition of the required amount of ppCP10C20, ppCP15C20, or ppCP30C40 prepolymers, also prepared as previously described. Water-free p-dioxane (Acros Organics, distilled and fractionated under reduced pressure in a modified rotary evaporator setup) was pumped into the reactor until a polymer concentration of 30 wt% was reached. The reactor was heated to 80°C to dissolve the prepolymer, and 1,4-butanediisocyanate (Bayer) was added. Additional tin octoate was added to increase its total content to 45 ppm. The reaction mixture was then magnetically stirred until the desired viscosity was achieved. Distilled p-dioxane containing 20 wt% water was then added to quench any unreacted isocyanate groups and terminate the reaction. Stirring was continued for an additional 30 minutes. The reaction mixture was further diluted with p-dioxane to a polymer concentration of 10 wt%, cooled to room temperature, poured into trays, and frozen at -18°C. p-Dioxane was removed from the frozen reaction mixture under reduced pressure in a vacuum oven at 30°C or by precipitation with a mixture of ethanol and n-heptane. Table 8 lists experimental details for various [poly(ε-caprolactone)-co-PEG-co-poly(ε-caprolactone)]-b-[poly(p-dioxanone)] multiblock copolymers.

[0239] [Table 8]

[0240] The polymer was stored in a sealed container at −18°C and the polymer composition ( 1H-NMR), intrinsic viscosity, residual p-dioxane content (gas chromatography), and thermal properties (mDSC).

[0241] Table 9 shows the analytical results collected for 54CP10C20-D20, 60CP10C20-D23, 50CP15C20-D23, and 50CP15C20-D25. From the D / P and C / P molar ratios, 1 The actual compositions of the copolymers, determined by H-NMR, closely resembled the target compositions. The intrinsic viscosities of the polymers varied between 0.54 and 1.13 dL / g. The residual dioxane content was very low, indicating that it had been effectively removed by vacuum drying and precipitation.

[0242] [Table 9]

[0243] The multiblock copolymers were analyzed for thermal properties to confirm their phase-separated morphology (Table 10). Figure 4 shows typical DSC thermograms for 60CP10C20-D23 (RCP 15126), 50CP15C20-D23 (RCP 15125), and 50CP30C40-D28 (RCP 1524) multiblock copolymers. All multiblock copolymers exhibited melting points (Tm) at approximately 80 °C due to the melting of the dioxanone segments. In addition, the PEG1500-containing 50CP15C20-D23 and the PEG3000-containing 50CP30C40-D28 exhibited melting peaks at approximately 50 °C due to the melting of the PEG-rich phase. The glass transition temperature (Tg) of the multi-block copolymer generally lies between the glass transition temperatures of the two prepolymers, indicating phase mixing of the amorphous prepolymer with the amorphous component of the semi-crystalline prepolymer.

[0244] [Table 10]

[0245] Example 7

[0246] This example describes the synthesis and analysis of [poly(DL-lactide)-co-PEG-co-poly(DL-lactide)]-b-[poly(p-dioxanone)] multiblock copolymers.

[0247] [Poly(DL-lactide)-co-PEG-co-poly(DL-lactide)]-b-[poly(p-dioxanone)] multiblock copolymers with various block ratios were prepared by chain extending ppDxx prepolymers with ppLP2L20, ppLP6L12, or ppLP10L20 prepolymers using 1,4-butanediisocyanate as the chain extender. Poly(p-dioxanone) prepolymers were first prepared in situ in a jacketed reactor as described above, followed by the addition of the required amount of ppLP2L20, ppLP6L12, or ppLP10L20 prepolymers, also prepared as described above. Chain extension and workup of the [poly(DL-lactide)-co-PEG-co-poly(DL-lactide)]-b-[poly(p-dioxanone)] multiblock copolymers were carried out according to the procedure described in Example 6. p-Dioxane was removed by precipitation using a mixture of ethanol and n-heptane. Table 11 lists the experimental details of various [poly(DL-lactide)-co-PEG-co-poly(DL-lactide)]-b-[poly(p-dioxanone)] multiblock copolymers.

[0248] [Table 11]

[0249] The polymer was stored in a sealed container at −18°C and the polymer composition ( 1 H-NMR), intrinsic viscosity, residual p-dioxane content (gas chromatography), and thermal properties (mDSC).

[0250] From the molar ratios of D / P and L / P 1The actual compositions of the copolymers, determined by H-NMR, closely resembled the target compositions. The intrinsic viscosity of the polymers varied between 0.60 and 0.68 dl / g.

[0251] The multiblock copolymers were analyzed for thermal properties to confirm their phase-separated morphology (Table 13). Figure 5 shows typical DSC thermograms for 60LP2L20-D27 (RCP 1926), 10LP6L12-D27 (RCP 1804), 10LP10L20-D27 (RCP 1810), and 50DP10D24-D25 (RCP 1509) multiblock copolymers. All multiblock copolymers exhibited melting points (Tm) between 85 and 90 °C due to melting of the poly(p-dioxanone) segments. The glass transition temperatures (Tg) of the multiblock copolymers generally lie between those of the two prepolymers, indicating phase mixing between the amorphous prepolymer and the amorphous component of the semicrystalline prepolymer.

[0252] [Table 12]

[0253] Example 8

[0254] Due to the phase-separated morphology of multiblock copolymers, the block composition significantly affects the overall erosion kinetics of the multiblock copolymers. The content and molecular weight of PEG, as well as the length of the poly(ε-caprolactone) chain of the hydrophilic prepolymer segment (A) and the molecular weight (Mn) of the crystalline poly(p-dioxanone) prepolymer segment (B) are considered to be the most important parameters for the overall erosion kinetics of the resulting multiblock copolymers. The synthesis of the polymers tested for in vitro erosion kinetics is described in Example 6. The polymer compositions and related physicochemical properties are listed in Table 14.

[0255] [Table 13]

[0256] Polymer-only microspheres were prepared by an oil-in-water emulsification process based on solvent extraction / evaporation. 5.8 g of polymer (10.0 wt %) dissolved in 52.4 g of dichloromethane was emulsified in 3.08 kg of ultrapure water containing 4.0 wt % PVA and 5 wt % NaCl by membrane emulsification using a 20 μm pore size membrane. The resulting microspheres were collected on a 5 μm membrane filter and washed three times with 250 ml of ultrapure water containing 0.05 wt % Tween® 80 and three times with 250 g of ultrapure water. Finally, the microspheres were freeze-dried. Particle size measurement by SEM imaging and microscopy were performed according to the same procedures as described in Example 1.

[0257] In vitro erosion of unloaded polymer-only microspheres was measured in 100 mM phosphate buffer, pH 7.4 (90–100 mg microspheres in 10 ml). Samples were incubated at 37°C. At each sampling point, microspheres were collected, lyophilized, and weighed.

[0258] All of the various poly(p-dioxanone)-based multiblock copolymers were successfully processed into microspheres. Spherical microspheres with smooth surface morphology (Figure 6) and average sizes ranging from 42 to 55 μm were obtained for all polymers. Figure 7 shows the effect of PEG molecular weight and PEG content of the hydrophilic block, as well as the block ratio, on the in vitro erosion of D-MBCP-based polymer-only microspheres. Polymer-only microspheres composed of 50CP10C20-LL40 were included as controls. The erosion rates of all multiblock copolymers composed of poly(p-dioxanone)-based crystalline blocks were significantly faster than those of 50CP10C20-LL40. After 12 months, the residual mass of the polymer-only microspheres composed of 50CP10C20-LL40 was approximately 80%. Substituting the LL40 block with a poly(p-dioxanone)-based block resulted in significantly faster eroding polymers. The residual mass of polymer-only microspheres composed of 60CP10C20-D25 was approximately 40% after 12 months. The erosion rate could be further increased by replacing PEG1000 with PEG1500 or PEG3000. Polymer-only microspheres composed of 30CP15C20-D24, 50CP15C20-D23, and 20CP30C40-D23 showed a nearly linear erosion rate, with only 20-25% residual mass after 12 months.

[0259] Furthermore, the erosion rate of the entire multiblock copolymer was found to increase significantly with decreasing poly(ε-caprolactone) chain length in the hydrophilic block (Figure 8), which is attributed to the high PEG content (and high water swelling) of the multiblock copolymer, which is composed of hydrophilic blocks containing short poly(ε-caprolactone) chains.

[0260] Example 9

[0261] To screen poly(p-dioxanone)-based multiblock copolymers, the in vitro erosion (IVE) kinetics of polymer-only microspheres composed of poly(p-dioxanone)-based multiblock copolymers with different compositions (synthesized as described in Example 6) were compared. Polymer-only microspheres were prepared and analyzed for their in vitro erosion kinetics as described in Example 1. Table 15 shows the in vitro erosion duration of polymer-only microspheres composed of various poly(p-dioxanone)-based multiblock copolymers.

[0262] [Table 14]

[0263] All poly(p-dioxanone)-based multiblock copolymers degraded much faster than the 50CP10C20-LL40 reference material. Based on extrapolation of in vitro erosion data, the time to complete in vitro erosion of the various poly(p-dioxanone)-based multiblock copolymers varied from 9 to 24 months, which is 2 to 5 times faster than the time obtained for 50CP10C20-LL40. The time to complete in vivo erosion of the various poly(p-dioxanone)-based multiblock copolymers is expected to be 3 to 8 months.

[0264] Example 10

[0265] To further characterize the 60CP10C20-Dxx-based microspheres, we investigated in more detail the effect of the Mn of the poly(p-dioxanone) prepolymer block of 60CP10C20-Dxx on microsphere processability and the crystallization of the poly(p-dioxanone) block. 60CP10C20-Dxx multiblock copolymers (Table 19) consisting of poly(p-dioxanone) prepolymer blocks with Mn ranging from 1556 g / mol to 2806 g / mol were synthesized as described in Example 6. Polymer-only microspheres were prepared and analyzed for particle size and microscopy as described in Example 1. Microspheres prepared with RCP1511 (Mn D-block 1556 g / mol) and RCP15116 (Mn D-block 1852 g / mol) exhibited poor processability (polymer thread formation, smearing) and resulted in sticky microspheres with severe aggregation (Table 16, Figure 9). Microspheres prepared with 60CP10C20-Dxx multiblock copolymers (RCP 1721, RCP 1711, RCP 1720, and RCP 1714) consisting of D-blocks with Mn greater than 2200 g / mol exhibited excellent processability leading to spherical microspheres with smooth surfaces and no visible surface voids, and showed good powder flowability without a tendency to agglomerate.

[0266] The thermal properties of the microspheres were analyzed by modulated differential scanning calorimetry (m-DSC) using a Q2000 DSC (TA Instruments) as described in Example 1. For the polymer, the melting temperature (Tm) and corresponding enthalpy of fusion (ΔHm) of the semicrystalline poly(p-dioxanone) block were determined from reverse heat flow. For polymer-only microspheres, Tm and ΔHm were determined from the total heat flow of the first heating run.

[0267] Thermal analysis showed that polymer-only microspheres prepared with 60CP10C20-Dxx (RCP 1511, RCP 15116) consisting of low-Mn poly(p-dioxanone) prepolymer blocks had significantly lower melting points and enthalpies of fusion than polymer-only microspheres prepared with 60CP10C20-Dxx multiblock copolymers (RCP 1721, RCP 1711, RCP 1720, and RCP 1714) consisting of poly(p-dioxanone) prepolymer blocks with Mn >2200 g / mol. At low D-block Mn, ΔHm increased rapidly with D-block Mn, whereas at higher D-block Mn, ΔHm appeared to plateau at a maximum of approximately 30–35 J / g (Figure 10). The poor microsphere processability, stickiness, and extensive aggregation observed for polymer-only microspheres prepared with 60CP10C20-Dxx multiblock copolymers with low molecular weight D-blocks can apparently be attributed to insufficient crystallization of the poly(p-dioxanone) prepolymer blocks.

[0268] [Table 15]

[0269] The effect of the molecular weight of the poly(p-dioxanone) block on in vitro erosion rates was investigated in more detail. Polymer-only microspheres were prepared with 60CP10C20-Dxx multiblock copolymers consisting of poly(p-dioxanone) blocks with molecular weights of 2116 (RCP 1710), 2356 (RCP 1718), and 2806 g / mol (RCP 1714) and analyzed according to the procedure described in Example 6. Spherical microspheres with smooth surfaces, no visible surface porosity, and average diameters of 50–55 μm were obtained (Figure 11A). Thermal analysis of the polymer-only microspheres was performed as described in Example 12. The melting points increased slightly from 81 to 88 °C with increasing D-block Mn, whereas the enthalpy of fusion remained relatively constant (24–32 J / g) (Table 17). The molecular weight of the poly(p-dioxanone) block did not affect the in vitro erosion kinetics of the 60CP10C20-Dxx-based microspheres in the range of 2100 to 2800 g / mol (Figure 11B).

[0270] [Table 16]

[0271] Example 11

[0272] In this example, sustained-release microspheres were prepared for two model proteins, bovine serum albumin and lysozyme, using poly(ε-caprolactone)-PEG-poly(ε-caprolactone)]-b-[poly(p-dioxanone)] multiblock copolymers with various block ratios and PEG molecular weights. The polymers were synthesized using a procedure similar to that used in Example 6.

[0273] Microspheres with a target protein loading of 4.5-5 wt% were prepared using a W1 / O / W2 water-in-oil-in-water double emulsion membrane emulsification method by solvent extraction / evaporation. 1 g of polymer was dissolved in 9 g of dichloromethane (10.0 wt%) and filtered through a 0.2 μm PTFE filter. Approximately 0.05 g of aqueous protein solution (100 mg / ml) was added, followed by emulsification at 21,600 rpm for 40 seconds using a rotor-stator mixer to obtain a primary emulsion. The primary emulsion was then emulsified in 650 g of ultrapure water containing 4.0 wt% PVA and 5 wt% NaCl by membrane emulsification using a 20 μm pore membrane to form a secondary emulsion. The secondary emulsion was stirred at room temperature for 3 hours, and the dichloromethane was removed by solvent extraction / evaporation. The obtained microspheres were collected on a 5 μm membrane filter and washed three times with a 0.05 w / v% Tween (registered trademark) 80 aqueous solution and three times with ultrapure water, and then the hardened microspheres were dried by freeze-drying.

[0274] The particle size distribution of the microspheres was measured using a Coulter counter. The BSA-loaded microspheres had a mean particle size of 52 μm and a narrow particle size distribution (CV 16%), while the mean particle size of the lysozyme-loaded microspheres was 34 μm (CV 18%). The surface morphology of the microspheres evaluated by scanning electron microscopy according to the method described in Example 1 showed that both the BSA-loaded and lysozyme-loaded microspheres had smooth surface morphologies without microporous structures.

[0275] The protein content of the microspheres was determined by dissolving 5-10 mg of microspheres in 5 ml of acetonitrile, centrifuging, removing 4 ml of the supernatant, and adding 5 ml of PBS. The BSA concentration was measured by UPLC (eluent A: 0.1 wt% TFA in UP water, eluent B: 0.1 wt% TFA in acetonitrile, with a gradient of 90 / 10 v / v to 10 / 90 v / v A / B over 4 min).

[0276] The BSA-loaded microspheres had a BSA content of 3.9% and showed an encapsulation efficiency of 77%, while the lysozyme-loaded microspheres contained 4.6% lysozyme and showed an encapsulation efficiency of 99.5%.

[0277] [Table 17]

[0278] The in vitro release (IVR) of protein-loaded microspheres was investigated in triplicate in 2 ml of 100 mM phosphate buffer, pH 7.4, containing 0.02 w / v% NaN3, thermostated at 37°C. Samples taken at predetermined time points until the release was complete were analyzed by RP-UPLC to determine the cumulative protein release versus sampling time.

[0279] BSA-loaded 60CP10C20-D26 microspheres exhibited a sigmoidal release kinetics (Figure 12A). After a time lag of approximately 6 weeks during which little BSA was released, BSA was released relatively linearly for 2–4 months, after which the release slowed down. The total release duration was approximately 5 months, with a recovery rate of approximately 80%.

[0280] Lysozyme-loaded 20CP15C50-D23 microspheres also showed a time lag, but only for a few days (Figure 12B). Lysozyme was released in a nearly linear fashion from 1 to 6 weeks with a recovery rate of approximately 90%.

[0281] Example 12

[0282] In this example, sustained-release microspheres were prepared for a 1.5 kDa peptide using a 10 / 90 block ratio [poly(ε-caprolactone)-PEG1000-poly(ε-caprolactone)]-b-[poly(p-dioxanone)] multiblock copolymer prepared by a procedure similar to that used in Example 6.

[0283] Sustained-release peptide microspheres were prepared by solvent extraction / evaporation using a water-in-oil-in-water double emulsion membrane emulsification method. The polymer was dissolved in dichloromethane to a concentration of 10 wt% and emulsified with an aqueous solution of the peptide to obtain a primary emulsion. The primary emulsion was then pumped through a 20 μm pore membrane into a vessel containing aqueous 4.0 wt% PVA as the extraction medium to obtain a secondary emulsion. The secondary emulsion was stirred at room temperature for 3 hours, and the DCM was removed by solvent extraction / evaporation. The resulting microspheres were collected, washed, and dried by lyophilization.

[0284] The particle size distribution and surface morphology of the microspheres were characterized according to the method described in Example 1. The peptide-loaded microspheres were spherical, with a smooth surface morphology and an average size of approximately 80 μm. The encapsulation efficiency was approximately 85%. The in vitro release kinetics of the peptide-loaded microspheres was performed in triplicate at 37°C in aqueous TRIS buffer, pH 7.4, containing 0.02 w / v% NaN3. The peptide concentration in release samples collected at predetermined time points was analyzed by RP-UPLC (Waters ACQUITY UPLC BEH C18 column) using a water / acetonitrile / 0.1% TFA gradient elution and UV detection at 226 nm. Following an initial burst release, the peptide was then released slowly at a nearly constant rate (Figure 13).

[0285] Example 13

[0286] In this example, levonorgestrel-loaded implants were prepared using the multiblock copolymer synthesized as described in Example 7. Small-diameter implants with target levonorgestrel loadings of 20-48 wt% were prepared at a 7 g scale by hot-melt extrusion using a Haake Minilab extruder. Briefly, the polymer and micronized levonorgestrel (D90 < 10 μm) were mixed manually with a spatula, then the mixture was added to a preheated extruder (100-110°C) and mixed for 5-10 minutes using a circulation loop. The mixture was then extruded through a 0.5 mm or 1.0 mm die. After cooling, the extrudate was manually cut into approximately 10 mm long implants.

[0287] [Table 18]

[0288] The microscopic appearance of the levonorgestrel implants was evaluated by scanning electron microscopy using a JEOL JCM-5000 Neoscope. The implant surface was relatively rough, suggesting the presence of LNG particles (Figure 14A). The levonorgestrel content of the implants was determined by dissolving the implants in acetonitrile, diluting the solution with water after the implants had completely dissolved, and centrifuging the precipitated polymer. The actual content was close to the target content.

[0289] The in vitro release (IVR) of the levonorgestrel implant was investigated in triplicate in aqueous buffer (100 mM phosphate buffer, 0.5% SDS, pH 7.4, 0.02 w / v% NaN3) at 37°C. Samples were taken at predetermined time points until the release was complete, and the levonorgestrel concentration was determined by RP-UPLC using a Waters ACQUITY UPLC BEH C18 column, eluted with a 50 / 50 mixture of water / acetonitrile, and detected by UV detection (243 nm).

[0290] Figure 14B shows the cumulative in vitro release kinetics of levonorgestrel implants. Poly(DL-lactide)-based levonorgestrel implants released very little levonorgestrel up to four months. 10LP6L12-D27-based levonorgestrel implants exhibited sustained release for up to three months (0.5 mm) or four months (1.0 mm). 10LP6L12-60GL20-D27-based levonorgestrel implants exhibited almost completely linear release kinetics from the start through three months. At the three-month time point, very little residue was found to remain for the 10LP6L12-D27-based and 10LP6L12-60GL20-D27-based implants, indicating complete degradation of the polymer by that time. The present disclosure also includes the following aspects. <1> 1. A biodegradable phase-separated thermoplastic multi-block copolymer, comprising: at least one amorphous hydrolyzable prepolymer (A) segment and at least one semi-crystalline hydrolyzable prepolymer (B) segment; The multi-block copolymer has a Tg of 37°C or less and a Tm of 50 to 110°C under physiological conditions; the segments are linked by a multifunctional chain extender; the segments are randomly distributed along the polymer chain; and The prepolymer (B) segment comprises an XYX triblock copolymer, wherein: Y is a polymerization initiator, and X is a poly(p-dioxanone) segment having a block length of 7 or more represented by p-dioxanone monomer units; Biodegradable phase-separated thermoplastic multiblock copolymers. <2> X is a poly(p-dioxanone) segment having a block length represented by p-dioxanone monomer units of 7 to 35, for example, 7 to 30, 8 to 25, 9 to 20, 10 to 15, or 11 to 14; <1> 1. A biodegradable, phase-separated, thermoplastic multi-block copolymer according to claim 1. <3> The prepolymer (B) segment has a molecular weight distribution Mw / Mn in the range of 1.0 to 3.0, for example, in the range of 1.2 to 2.0, or in the range of 1.3 to 1.6. <1> or <2> 1. A biodegradable, phase-separated, thermoplastic multi-block copolymer according to claim 1. <4> At least a portion of the prepolymer (A) segments are derived from a water-soluble polymer; <1> ~ <3> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <5> 30% or more, for example, 40 to 95%, 50 to 90%, or 60 to 85% of the total weight of the prepolymer (A) is derived from a water-soluble polymer; <1> ~ <4> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <6> The prepolymer (A) segment comprises poly(p-dioxanone); <1> ~ <5> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <7> the amount of poly(p-dioxanone) in the prepolymer (A) segment is 80% or less, 60% or less, or 40% or less, 20% or less, 10% or less, or 5% or less of the total weight of the prepolymer (A); <6> 1. A biodegradable, phase-separated, thermoplastic multi-block copolymer according to claim 1. <8> 70% or more of the total weight of the prepolymer (B) segments is poly(p-dioxanone), preferably 80% or more of the total weight of the prepolymer (B) segments is poly(p-dioxanone), and more preferably 90% or more of the total weight of the prepolymer (B) segments is poly(p-dioxanone). <1> ~ <7> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <9> The prepolymer (B) segment has a number average molecular weight Mn of 1300 to 7200 g / mol, preferably 1300 to 5000 g / mol, more preferably 1500 to 4500 g / mol, even more preferably 2000 to 4000 g / mol, and most preferably 2200 to 3200 g / mol. <1> ~ <8> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <10> The prepolymer (B) segment has a weight average molecular weight Mw of 1800 to 10080 g / mol, preferably 1800 to 7000 g / mol, preferably 2100 to 6300 g / mol, more preferably 2600 to 5600 g / mol, and most preferably 3000 to 4200 g / mol. <1> ~ <9> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <11> The prepolymer (B) has a Tg of less than 0°C, preferably less than -20°C, more preferably less than -40°C; <1> ~ <10> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <12> The prepolymer (B) has a Tm in the range of 60 to 100°C, preferably in the range of 75 to 95°C. <1> ~ <11> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <13> The water-soluble polymer comprises one or more selected from the group consisting of polyethers such as polyethylene glycol (PEG), polytetramethylene oxide (PTMO), and polypropylene glycol (PPG), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinylcaprolactam, poly(hydroxyethyl methacrylate) (poly-(HEMA)), polyphosphazene, or copolymers of these polymers; <4> ~ <12> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <14> The water-soluble polymer is derived from poly(ethylene glycol) (PEG) having an Mn of 150 to 5000 g / mol. <4> ~ <13> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <15> The chain extender is a difunctional aliphatic chain extender. <1> ~ <14> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <16> The difunctional aliphatic chain extender is a diisocyanate such as 1,4-butane diisocyanate. <15> 1. A biodegradable, phase-separated, thermoplastic multi-block copolymer according to claim 1. <17> the prepolymer (A) comprises a reaction product of cyclic and / or acyclic monomers, the acyclic monomers being preferably selected from the group consisting of succinic acid, glutaric acid, adipic acid, sebacic acid, lactic acid, glycolic acid, hydroxybutyric acid, ethylene glycol, diethylene glycol, 1,4-butanediol, and / or 1,6-hexanediol, and the cyclic monomers being preferably selected from the group consisting of cyclic anhydrides such as glycolide, lactide, ε-caprolactone, δ-valerolactone, trimethylene carbonate, tetramethylene carbonate, 1,5-dioxepan-2-one, 1,4-dioxan-2-one (p-dioxanone), and / or oxepane-2,7-dione; <1> ~ <16> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <18> The water-soluble polymer is present as an additional prepolymer; <1> ~ <17> 1. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9. <19> the additional prepolymer is present in the multi-block copolymer in an amount of 30% or less, e.g., 20% or less, of the total weight of the multi-block copolymer; <18> 1. A biodegradable, phase-separated, thermoplastic multi-block copolymer according to claim 1. <20> The prepolymer (A) segment is

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Claims

1. 1. A biodegradable phase-separated thermoplastic multi-block copolymer, comprising: at least one amorphous hydrolyzable prepolymer (A) segment and at least one semi-crystalline hydrolyzable prepolymer (B) segment; The multi-block copolymer has a Tg of 37°C or less and a Tm of 50 to 110°C under physiological conditions; the segments are linked by a multifunctional chain extender; the segments are randomly distributed along the polymer chain; and The prepolymer (B) segment comprises an X-Y-X triblock copolymer, wherein: Y is a polymerization initiator, and X is a poly(p-dioxanone) segment having a block length of 9 to 35 represented by p-dioxanone monomer units; Biodegradable phase-separated thermoplastic multiblock copolymers.

2. 2. The biodegradable phase-separated thermoplastic multi-block copolymer of claim 1, wherein the prepolymer (B) segment has a molecular weight distribution Mw / Mn in the range of 1.0 to 3.

0.

3. 3. The biodegradable phase-separated thermoplastic multi-block copolymer according to claim 1 or 2, wherein at least a portion of the prepolymer (A) segments are derived from a water-soluble polymer.

4. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 3, wherein 30% or more of the total weight of the prepolymer (A) is derived from a water-soluble polymer.

5. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 4, wherein the prepolymer (A) segment comprises poly(p-dioxanone).

6. 6. The biodegradable phase-separated thermoplastic multi-block copolymer of claim 5, wherein the amount of poly(p-dioxanone) in the prepolymer (A) segment is 80% or less of the total weight of the prepolymer (A).

7. 7. The biodegradable phase-separated thermoplastic multi-block copolymer according to claim 1, wherein 70% or more of the total weight of the prepolymer (B) segments is poly(p-dioxanone).

8. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 7, wherein the prepolymer (B) segment has a number average molecular weight Mn of 1300 to 7200 g / mol.

9. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 8, wherein the prepolymer (B) segment has a weight average molecular weight Mw of 1800 to 10080 g / mol.

10. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 9, wherein the prepolymer (B) has a Tg of less than 0°C.

11. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 10, wherein the prepolymer (B) has a Tm in the range of 60 to 100°C.

12. 5. The biodegradable phase-separated thermoplastic multi-block copolymer of claim 3 or 4, wherein the water-soluble polymer comprises one or more selected from the group consisting of polyether, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinylcaprolactam, poly(hydroxyethyl methacrylate) (poly-(HEMA)), polyphosphazene, or copolymers of these polymers.

13. 5. The biodegradable phase-separated thermoplastic multi-block copolymer according to claim 3 or 4, wherein the water-soluble polymer is derived from poly(ethylene glycol) (PEG) having a Mn of 150-5000 g / mol.

14. The biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 13, wherein the chain extender is a difunctional aliphatic chain extender.

15. 15. The biodegradable phase-separated thermoplastic multi-block copolymer of claim 14, wherein the difunctional aliphatic chain extender is a diisocyanate.

16. 16. The biodegradable phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 15, wherein prepolymer (A) comprises the reaction product of cyclic and / or acyclic monomers.

17. 17. The biodegradable, phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 16, wherein a water-soluble polymer is present in the multi-block copolymer as an additional prepolymer segment.

18. 20. The biodegradable, phase-separated, thermoplastic multi-block copolymer of claim 17, wherein the additional prepolymer is present in the multi-block copolymer in an amount of 30% or less of the total weight of the multi-block copolymer.

19. The prepolymer (A) segment is 【Chemical 1】 【Chemistry 2】 【Chemistry 3】 and 【Chemistry 4】 and one or more selected from the group consisting of The prepolymer (A) segment is 【Chemistry 5】 and The prepolymer (B) segment is 【Chemistry 6】 Including, The biodegradable phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 18, which is a poly(ether ester) multi-block copolymer.

20. The prepolymer (A) segment is 【Chemistry 7】 or 【Chemistry 8】 is expressed as wherein n is 4 to 120; The biodegradable, phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 19.

21. The multi-block copolymer is １ R ２ ｎ R ３ ) ｑ ] ｒ [(R ４ ｐ R ５ R ６ ｐ )] ｓ is expressed as where: R １ and R ３ But independently, 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 and any combination thereof; R ２ but, 【Chemistry 13】 and R ４ and R ６ However, respectively, 【Chemistry 14】 and R 5 is the polymerization initiator; R ２ n, the number of repeating moieties, is 4 to 120; R ４ and R ６ The number of repeating moieties, p, is 9 to 35; (R １ R ２ ｎ R ３ ) the number average molecular weight of the block, q, is 400 to 10,000 g / mol; The ratio of prepolymer (A) segments to prepolymer (B) segments, r / s, is 0.1 to 2.5; and r is (R １ R ２ ｎ R ３ ) ｑ is the weight percent of the block, and s is (R ４ ｐ R ５ R ６ ｐ ) is the weight percent of the block, The biodegradable, phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 19.

22. The biodegradable, phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 21 in the form of microspheres.

23. i) carrying out a chain extension reaction of prepolymer (A) and prepolymer (B) in the presence of a polyfunctional chain extender, wherein prepolymers (A) and (B) are both terminated with a diol or a diacid, and the chain extender is terminated with a dicarboxylic acid, a diisocyanate, or a diol; or ii) carrying out a chain extension reaction using a coupling agent, wherein prepolymers (A) and (B) are both terminated with a diol or diacid; Including, The prepolymer (B) segment comprises an X-Y-X triblock copolymer, wherein: Y is a polymerization initiator, and X is a poly(p-dioxanone) segment having a block length of 9 to 35 represented by p-dioxanone monomer units; A method for preparing the biodegradable phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 22.

24. Use of the biodegradable phase-separated thermoplastic multi-block copolymer of any one of claims 1 to 22 for drug delivery.

25. 25. The use of claim 24, wherein the multi-block copolymer is in the form of a microsphere, microparticle, nanoparticle, nanosphere, rod, implant, gel, coating, film, sheet, spray, tube, membrane, mesh, fiber, or plug.

26. 23. A composition for delivering at least one bioactive compound to a host, comprising at least one bioactive compound encapsulated in a matrix, said matrix comprising at least one biodegradable phase-separated thermoplastic multi-block copolymer according to any one of claims 1 to 22.

27. 27. The composition of claim 26, wherein the at least one biologically active compound is a non-peptide, non-proteinaceous small molecule drug or a biologically active polypeptide.

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