WO2021073667A1 - Method for the preparation of polymeric carriers for ph- controlled drug release and their conjugates with drugs - Google Patents

Method for the preparation of polymeric carriers for ph- controlled drug release and their conjugates with drugs Download PDF

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WO2021073667A1
WO2021073667A1 PCT/CZ2020/050080 CZ2020050080W WO2021073667A1 WO 2021073667 A1 WO2021073667 A1 WO 2021073667A1 CZ 2020050080 W CZ2020050080 W CZ 2020050080W WO 2021073667 A1 WO2021073667 A1 WO 2021073667A1
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group
drug
statistical copolymer
general formula
linear statistical
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PCT/CZ2020/050080
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French (fr)
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Petr Chytil
Eva RANDAROVA
Tomas Etrych
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Ustav Makromolekularni Chemie Av Cr, V.V.I.
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Priority to EP20810857.1A priority Critical patent/EP4045088A1/en
Publication of WO2021073667A1 publication Critical patent/WO2021073667A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
    • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
    • A61K47/51—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent
    • A61K47/56—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an organic macromolecular compound, e.g. an oligomeric, polymeric or dendrimeric molecule
    • A61K47/58—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an organic macromolecular compound, e.g. an oligomeric, polymeric or dendrimeric molecule obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. poly[meth]acrylate, polyacrylamide, polystyrene, polyvinylpyrrolidone, polyvinylalcohol or polystyrene sulfonic acid resin
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K31/00—Medicinal preparations containing organic active ingredients
    • A61K31/33—Heterocyclic compounds
    • A61K31/335—Heterocyclic compounds having oxygen as the only ring hetero atom, e.g. fungichromin
    • A61K31/337—Heterocyclic compounds having oxygen as the only ring hetero atom, e.g. fungichromin having four-membered rings, e.g. taxol
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
    • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
    • A61K47/51—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent
    • A61K47/62—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being a protein, peptide or polyamino acid
    • A61K47/64—Drug-peptide, drug-protein or drug-polyamino acid conjugates, i.e. the modifying agent being a peptide, protein or polyamino acid which is covalently bonded or complexed to a therapeutically active agent
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
    • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
    • A61K47/51—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent
    • A61K47/68—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an antibody, an immunoglobulin or a fragment thereof, e.g. an Fc-fragment
    • A61K47/6835—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an antibody, an immunoglobulin or a fragment thereof, e.g. an Fc-fragment the modifying agent being an antibody or an immunoglobulin bearing at least one antigen-binding site
    • A61K47/6883—Polymer-drug antibody conjugates, e.g. mitomycin-dextran-Ab; DNA-polylysine-antibody complex or conjugate used for therapy
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K49/00—Preparations for testing in vivo
    • A61K49/001—Preparation for luminescence or biological staining
    • A61K49/0013—Luminescence
    • A61K49/0017—Fluorescence in vivo
    • A61K49/0019—Fluorescence in vivo characterised by the fluorescent group, e.g. oligomeric, polymeric or dendritic molecules
    • A61K49/0021—Fluorescence in vivo characterised by the fluorescent group, e.g. oligomeric, polymeric or dendritic molecules the fluorescent group being a small organic molecule
    • A61K49/0032—Methine dyes, e.g. cyanine dyes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K49/00—Preparations for testing in vivo
    • A61K49/001—Preparation for luminescence or biological staining
    • A61K49/0013—Luminescence
    • A61K49/0017—Fluorescence in vivo
    • A61K49/0019—Fluorescence in vivo characterised by the fluorescent group, e.g. oligomeric, polymeric or dendritic molecules
    • A61K49/0021—Fluorescence in vivo characterised by the fluorescent group, e.g. oligomeric, polymeric or dendritic molecules the fluorescent group being a small organic molecule
    • A61K49/0041—Xanthene dyes, used in vivo, e.g. administered to a mice, e.g. rhodamines, rose Bengal
    • A61K49/0043—Fluorescein, used in vivo
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K49/00—Preparations for testing in vivo
    • A61K49/001—Preparation for luminescence or biological staining
    • A61K49/0013—Luminescence
    • A61K49/0017—Fluorescence in vivo
    • A61K49/005—Fluorescence in vivo characterised by the carrier molecule carrying the fluorescent agent
    • A61K49/0054—Macromolecular compounds, i.e. oligomers, polymers, dendrimers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/52—Amides or imides
    • C08F20/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F20/58—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing oxygen in addition to the carbonamido oxygen, e.g. N-methylolacrylamide, N-acryloylmorpholine
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/52—Amides or imides
    • C08F20/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F20/60—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing nitrogen in addition to the carbonamido nitrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/52—Amides or imides
    • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F220/58—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing oxygen in addition to the carbonamido oxygen, e.g. N-methylolacrylamide, N-(meth)acryloylmorpholine
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/52—Amides or imides
    • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F220/60—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide containing nitrogen in addition to the carbonamido nitrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/30—Introducing nitrogen atoms or nitrogen-containing groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2438/00—Living radical polymerisation
    • C08F2438/03—Use of a di- or tri-thiocarbonylthio compound, e.g. di- or tri-thioester, di- or tri-thiocarbamate, or a xanthate as chain transfer agent, e.g . Reversible Addition Fragmentation chain Transfer [RAFT] or Macromolecular Design via Interchange of Xanthates [MADIX]

Definitions

  • the invention relates to a method for the preparation of polymeric drug carriers enabling targeted transport and controlled release of active substances in the body, in particular in tumour tissue, inflammatory tissue, tumour cells and cells of the immune system.
  • the use of these polymeric conjugates focuses on the targeted therapy of cancer, inflammatory and autoimmune diseases in human medicine.
  • the preparation method is well reproducible and provides high yields. It allows precise control of the molar masses of polymer precursors with low dispersity and precisely defined structure. Last but not least, this method of preparation is easily transferable to an industrial scale.
  • An important feature of these transport systems is the large size in the aqueous environment, which can ensure preferential deposition of the drug delivery system in the tumour tissue of a number of solid tumours (the so-called EPR effect) and in inflammatory tissue (the so-called ELVIS effect).
  • the release of the active drug from the delivery system can advantageously be achieved via a biodegradable linker used to bind the drug to a polymer, the degradation of which in the target tissue leads to a targeted and controlled activation of the drug, preferably in this tissue.
  • hydrazide groups need to be protected during polymerisation.
  • the authors of the publication therefore applied protection with a tert- butoxycarbonyl (Boc) group.
  • the dithiobenzoate groups at the end of the polymeric carrier were removed by reduction with sodium borohydride and the resulting -SH groups were blocked by reaction with N- ethylmaleimide. Only then were the Boc groups removed with trifluoro acetic acid (TFA).
  • TFA trifluoro acetic acid
  • the disadvantage of this carrier synthesis is the need for several subsequent steps after polymerisation.
  • the step of deprotecting the hydrazide groups is a step which is difficult to reproduce and does not allow easy preparation of larger batches of the polymer required for industrial application.
  • the final purification of the polymer by gel filtration means complications for the preparation of a larger amount of the carrier.
  • the described procedure for the synthesis of the carrier was also used in other publications. The basis is always the copolymerisation of HPMA with a monomer bearing Boc protected hydrazide groups (e.g. Subr V. et al. Biomacromolecules 2014, 15 (8), 3030-3043, Chytil P. et al. Macromol. Biosci. 2015, 15 (6), 839-850, Lomkova E. et al. Biomacromolecules 2016, 17 (11), 3493-3507). The blocking of the end groups and the subsequent deprotection of the hydrazide groups differed slightly.
  • the process should also be easily transferable to an industrial scale.
  • the object of the present invention is a method for the preparation of polymeric carriers based on HPMA copolymers suitable for binding drugs by means of a pH-sensitive hydrolysable hydrazone bond.
  • the process for preparing the polymeric carrier according to the present invention makes it possible to introduce biologically active substances at the ends of the polymer chains.
  • Natural amino acids can be understood as naturally occurring acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, arginine, cysteine, glutamine, glycine, proline, tyrosine, alanine, aspartic acid, asparagine, glutamic acid, serine, selenocysteine.
  • Their side chains are to be understood as chains attached to the alpha-carbon of a particular amino acid.
  • a semitelechelic linear copolymer is a statistical copolymer formed by a radical polymerisation reaction.
  • the end groups of the resulting linear copolymer contain parts of molecules of the polymerisation initiator (e.g. azo initiators, such as 2,2'-azobis(2-methylpropionitrile) (AIBN), 4,4'-azobis(4-cyanopentanoic acid) (ACVA), 2,2'-azobis(4-methoxy-2,4-dimethylpentanenitrile) (V70)), and of the transfer agent (preferably selected from the group consisting of 2-cyano-2- propyl benzodithioate, 4-cyano-4-(thiobenzoylthio)pentanoic acid, 2-cyano-2-propyldodecyl trithio-carbonate, 2-cyano-2-propylethyltrithiocarbonate and 4-cyano-4-[(dodecylsulphanylthio- carbonyl)sulphanyl]
  • the end groups of the copolymer contain at one end a radical leaving group of the transfer agent, preferably 2-cyano-2-propyl, or 5-carboxy-2-cyano-2-pentyl.
  • X is selected from the group comprising -CH2-, -(CH2)2-, -(CH2)5- ; -C(H)(CH 2 -Phe)-, -C(H)(CH-iPr)-, -C(H)(sec-Bu)-; -CH 2 -C(O)-NH-CH 2 -;
  • the method for the preparation of polymeric carriers of general formula (I) comprises the following steps: a) providing monomers of the polymeric carrier, thus providing HPMA (commercially available) and providing a monomer of general formula (III), wherein X is as defined above, and Y is selected from the group consisting of hydroxyl, (C1-C6) alkoxy, benzoxy, 4-nitrophenoxy, 2,3,4,5,6-pentafluorophenoxy, succinimidyl, (C1-C6) alkylthio group and thiazolidine-2-thione group; preferably Y is selected from the group consisting of methoxy, ethoxy, tert-butoxy, tert- butylthio and thiazolidine-2-thione group; b) radical RAFT polymerisation of monomers of the polymeric carrier from step a); c) introduction of hydrazide groups instead of the substituent Y, while in situ modifying the end groups of the linear statistical copolymer to give
  • Step a) of providing polymeric carrier monomers comprises providing A- (2 - hydroxypropyl) methacrylamide (HPMA) and a monomer of general formula (III).
  • HPMA is commercially available and its synthesis is published (e.g. Chytil P. et al., Eur. J. Pharm. Sci., 2010, 41, 73-81).
  • the synthesis of monomers of general formula (III) lies in the reaction of an ester, thioester or imide of amino acids and compounds of formula Y-C(O)-X-NH 2 , where X and Y are as defined above, with methacryloyl chloride (this reaction may also be called methacryloylation) according to the Schotten-Bauman method, preferably performed in diethyl ether, or in dichloro methane in the presence of anhydrous sodium carbonate, or in water in the presence of alkali hydroxide.
  • the starting compounds of formula Y-C(O)-X-NH 2 are commercially available.
  • the step of methacryloylation of a commercially available compound of formula HO-C(O)-X-NH 2 followed by an esterification, thioesterification, or imidation of a carboxyl group may be included, preferably by the carbodiimide method using dicyclohexylcarbodiimide, diisopropylcarbodiimide, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide, or other reagents using benzotriazol-l-yloxytripyrrolidinophosphonium hexafluorophosphate or (2-(l H- benzotriazol- 1 -yl)- 1 , 1 ,3 ,3-tetramethyluronium hexafluorophosphate.
  • Step b) of polymerisation of monomers of the polymeric carrier lies in the controlled radical RAFT polymerisation of HPMA with a monomer of general formula (III) in a molar ratio of HPMA: monomer of formula (III) in the range of from 99.5:0.5 to 75:25.
  • the polymerisation takes place at a temperature in the range of from 30 to 100 °C, preferably from 40 to 80 °C, and in a solvent preferably selected from the group comprising dimethyl sulphoxide, dimethyl acetamide, dimethyl formamide, dioxane, tert-butyl alcohol, water, aqueous buffer or mixtures thereof, initiated by an initiator, preferably selected from the group comprising, in particular, azo initiators, such as 2,2'-azobis(2-methylpropionitrile) (AIBN), 4,4'-azobis (4-cyanopentanoic acid) (ACVA), 2,2'-azobis( 4-methoxy-2,4-dimethylpentanenitrile) (V70), and in the presence of a transfer agent, preferably selected from the group of 2-cyano-2-propyl benzodithioate, 4- cyano-4-(thiobenzoylthio) pentanoic acid, 2-cyano-2-propyl dodecyl tri
  • the synthesis of the polymer precursors is carried out at a molar ratio of initiator : transfer agent in the range of from 1:1 to 1:10.
  • the synthesis of the polymer precursors is carried out at a molar ratio of transfer agent : monomers in the range of from 1:50 to 1:1000.
  • Step c) of introduction of hydrazide groups while modifying the end groups of the polymeric carrier lies in converting the group Y (reactive esters, thioesters and imides) to hydrazide groups (-NH-NH2) and in situ modification (removal) of sulphur-containing end groups of the polymeric carrier originating from the transfer agent.
  • the double bond compounds are preferably selected from the group comprising N- substituted maleimide and S- substituted vinyl sulphone; more preferably selected from the group comprising divinyl sulphone, carboxy-PEG vinyl sulphone, A-cthyl maleimide.
  • step c) may optionally be followed by step d), in which a biologically active molecule may be attached to the R2 group of general formula (I), if R2 is not
  • the bifunctional agent is A- a m i n o c t h y 1 m a 1 c i m i dc trifluoroacetate, or A- (3 - a m i n o p ro p y 1 ) m a 1 c i m i dc trifluoro acetate
  • the bifunctional agent is maleimidopropionic acid, or carboxy-PEG vinyl sulphone
  • ethynyl group the bifunctional agent is /V-propargylmaleimide
  • an azide group the bifunctional agent is azido-PEG-maleimide
  • the biologically active molecule is selected from the group comprising fluorescent labels, chelators for radionuclides, chelators for contrast agents for nuclear magnetic resonance, targeting groups, oligopeptides, oligosaccharides, peptides, scFc fragments, monoclonal antibodies and specific cell-surface receptor ligands.
  • An example of such an addition of a biologically active substance is the reaction of the end amine group with, for example, ester groups of other biologically active substances, which allows a great variability and universal use of the polymer.
  • the biologically active molecule is a fluorescent label, for example fluorescein, Cyanine 5.5, Cyanine 7, Cyanine 7.5, Dyomics-676, Dyomics-676, Alexa fluor-488; chelators for radionuclides, preferably deferoxamine, DOT A, NOT A, tyrosinamide; targeting groups for targeted biodistribution, preferably targeting oligopeptides, especially selected from the group comprising GE-7 (NPVVGYIGERPQYRDL oligopeptide), GE-11 (YHWYGYTPQNVI oligopeptide), RGD (arginylglycylaspartic acid); scFc fragments; and monoclonal antibodies, preferably anti-CD20, anti-CD38, anti-CD19, anti-Her2Neu, anti-GD2.
  • fluorescent label for example fluorescein, Cyanine 5.5, Cyanine 7, Cyanine 7.5, Dyomics-676, Dyomics-676, Alexa fluor-488
  • the method of binding of a particular known biologically active substance to an amino group, carboxyl group, ethynyl group or azide group of the linear statistical copolymer of general formula (I) may be carried out by standard reactions known to those skilled in the art based on standard knowledge in the technical field.
  • a fluorophore Cyanine 5.5 can be attached to the amino group of a polymer via the NHS ester of Cyanine 5.5.
  • other fluorescent labels e.g. Dyomics-676, Dyomics-782, Alexa fluor-488, containing reactive esters, may be attached.
  • deferoxamine can be bound already in step c) using deferoxamine maleimide.
  • Oligopeptides e.g. GE-7, GE-11, RGD, containing an azide group, i.e. oligopeptides terminated with azidopentanoic acid, can be attached by a catalysed click reaction.
  • fluorescent labels or chelators containing an azide group can be attached.
  • any biologically active substance containing a reactive functional group capable of conjugation with an amino group, a carboxyl group, an ethynyl group or an azide group can be attached to the linear statistical copolymer, or the biologically active substance can be converted to a derivative thereof containing this reactive functional group.
  • Another object of the present invention is a method for preparation of a conjugate of the linear statistical copolymer of general formula (I) based on HPMA copolymers, as defined above, with a drug, in particular by means of a pH-sensitive hydrolysable hydrazone bond.
  • This process comprises preparing the polymeric carrier according to steps a) to c) and optionally step d) above, followed by step e) of linking the drug to a structural unit of general formula (II) of the linear statistical copolymer, as defined above, by a hydrazone bond to form a conjugate of the linear statistical copolymer of formula (I) with the drug.
  • the drug is selected from the group comprising anti-tumour drugs, anti-inflammatory drugs or immuno modulators.
  • the drug is selected from the group comprising anthracycline, doxorubicin, dexamethasone, pirarubicin, epirubicin, ritonavir, docetaxel, paclitaxel, larotaxel, or oxo derivatives thereof (containing at least one keto group).
  • the reaction may be carried out in methanol, dimethyl sulphoxide, dimethyl formamide, dried ethanol and dimethyl acetamide.
  • the synthesis of polymer-drug conjugates is based on the previously described method of binding of doxorubicin (Etrych, T., et al., J. Control. Release, 2001. 73(1): p.
  • dexamethasone to the -NH-Nth group is described, for example, on pages 272 - 273 of the article ‘Synergistic effect of HPMA copolymer-bound doxorubicin and dexamethasone in vivo on mouse lymphomas’, H. Kostkova et at, Journal of Bioactive and Compatible Polymers, 2011, 26 (3), 270-286 or on pages 407 - 408 of the article ⁇ RMA-based polymer conjugates with drug combination’, H.
  • the initial concentration of the polymeric carrier for reaction with the keto groups of the drug is in the range of from 100 to 190 mg/mL
  • the concentration of the glacial acetic acid is in the range of from 30 to 80 mg/mL
  • the concentration of the drug/drug oxo derivative is in the range of from 1 to 50 mg/mL
  • the initial polymer concentration for reaction with the keto groups of the drug is 170 mg/mL
  • the acetic acid concentration is 55 mg/mL
  • the drug concentration is 20 mg/mL at 25 °C.
  • An optional further step f) of preparing the conjugate is the final purification of the conjugate from free unbound drug by gel filtration, for example using a column packed with cross-linked dextran (e.g. Sephadex LH-20) and methanol as mobile phase.
  • Gel filtration for polymer purification is known to the person skilled in the art, who would therefore know which stationary phase to use for gel filtration.
  • the present invention provides a reproducible method for the preparation of very well defined polymeric drug carriers based on HPMA copolymers, allowing the drugs to be bound by a pH-labile hydrazone bond to the carrier.
  • This new method of preparing polymeric carriers by means of controlled polymerisation makes it possible to increase the yields in the polymerisation and, thanks to the advantageous copolymerisation parameters close to one, to control the content of the comonomer unit (according to formula II) in the carrier; the synthesis is significantly easier and cheaper, it allows ‘scale-up’ to large batches and the reproducibility of the synthesis is very good.
  • the biological activity of conjugates of prepared polymeric carriers with drugs is the same as that of conjugates of previously prepared carriers.
  • the prepared copolymers were characterized by determining the weight and number average molar masses (M w , M n ) and the corresponding dispersity index (£ ) ) by gel permeation chromatography (GPC) on a system equipped with a PDA detector (Shimadzu, Japan), RI detector (Optilab REX, Wyatt Technology Corp ., USA) and a multi-angle light scattering detector (DAWN Heleos-II, Wyatt Technology Corp., USA).
  • a TSK 3000 Super SW column was used for SEC and a mixture of methanol (80 %) and 0.3 M acetate buffer pH 6.5 (20 %) as the mobile phase.
  • the sample concentration was 3 mg/mL in all cases.
  • the content of hydrazide groups was determined using the TNBSA test.
  • the content of methyl ester groups and other esters was determined by nuclear magnetic resonance (NMR) on a Bruker Avance III 600 MHz spectrometer in (CD 3 ) 2 SO.
  • the content of bound drugs was determined either spectrophotometrically or by HPLC after total hydrolysis, i.e. release from the polymeric carrier.
  • HPMA was prepared according to the procedure previously described (Chytil P. et al., Eur. J. Pharm. Sci., 2010, 41, 73-82). The product was chromatographically pure.
  • MA-AP-OMe N- methacryloy 1-3 -aminopropionic acid methyl ester
  • Methyl 3-aminopropionate hydrochloride (30 g, 0.215 mol) was dissolved in 350 mL of dichloromethane with vigorous stirring at room temperature. The solution was cooled to 10 - 15 °C and anhydrous sodium carbonate (67 g, 0.645 mol) was added, the temperature was reduced to 5 - 10 °C and then a solution of methacroyl chloride (22.5 g, 0.215 mol (eq.)) in 100 mL of dichloromethane was added dropwise at such a rate that the temperature of the reaction mixture does not exceed 15 °C.
  • MA-AH-OMe was prepared according to the procedure described above using methyl 3- aminohexanoate hydrochloride.
  • the product was chromatographically pure.
  • Example 2a Synthesis of polymer precursor - HPMA copolymer with MA-AH-OMe (poly(HPMA-co-MA-AH-OMe))
  • Poly(HPMA-co-MA-AH-OMe) copolymer was prepared by controlled radical RAFT copolymerisation of HPMA and MA-AH-OMe (prepared according to Example 1) initiated by AIBN in the presence of RAFT transfer agent 2-cyano-2-propyl benzodithioate in a tert-butyl alcohol and dimethyl sulphoxide at 70 °C.
  • HPMA 4.0 g, 27.9 mmol
  • MA-AH-OMe 0.377 g, 1.8 mmol
  • 2-cyano-2-propyl benzodithioate 18.8 mg, 84.9 ⁇ mol
  • AIBN 7.0 mg, 42.5 ⁇ mol
  • the polymerisation mixture was placed in an argon atmosphere in a polymerisation vial (50 mL volume), bubbled with argon for 10 minutes and sealed.
  • the polymerisation vial was placed in a thermostat at 70 °C.
  • the polymerisation mixture was removed from the thermostat after 16 h, cooled in a bath to the room temperature, and the polymer was isolated by precipitation into ethyl acetate (total 800 mL).
  • the precipitated polymer was allowed to settle for about 0.5 h, the solution above the precipitate was sucked off and the polymer was isolated by filtration on a S4 frit.
  • the precipitate was washed with ethyl acetate, transferred to large Petri dishes and dried at room temperature under a diaphragm pump vacuum for about 1 h.
  • the polymer was dissolved in 40 mL of methanol (100 mL Erlenmeyer flask) by means of ultrasound and precipitated into 800 mL of ethyl acetate in the same manner as in the first isolation. After about 0.5 h of sedimentation, the precipitated polymer was isolated by filtration on a S4 frit, washed with ethyl acetate and dried to constant weight (about 5 h) on a diaphragm pump and finally dried under an oil pump vacuum.
  • Copolymers were prepared analogously using other RAFT agents: S-2-cyano-2-propyl-S -ethyl trithiocarbonate, 4-cyano-4-(thiobenzoylthio) pentanoic acid, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyano-2-propyl ethyl trithiocarbonate and 4-cyano-4- [(dodecylsulphanyl- thiocarbonyl)sulphanyl] pentanoic acid.
  • Example 2b Synthesis of polymer precursor - HPMA copolymer with MA-AP-OMe (poly(HPMA-co-MA-AP-OMe))
  • the execution and procedure of polymerisation of poly(HPMA-co-MA-AP-OMe) were the same as in Example 2a, the difference being in the composition of the polymerisation mixture.
  • the composition of the polymerisation mixture was as follows: HPMA (4.0 g, 27.9 mmol) and MA- AP-OMe (0.308 g, 1.8 mmol) dissolved in 35.7 mL of tert- butyl alcohol, 2-cyano-2-propyl benzodithioate (18.8 mg, 84.9 ⁇ mol) and AIBN (7.0 mg, 42.5 ⁇ mol) dissolved in 4.0 ml of dimethyl sulphoxide.
  • the polymerisation temperature was 70 °C, the polymerisation time was 16 h.
  • Example 3b Synthesis of polymer precursor poly(HPMA-co-MA-AH-NHNH 2 ) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous blocking of the end thiol group of the polymer carrier and introduction of fluorescein at the end of the polymer chain
  • a hydrazide groups-containing copolymer was prepared by hydrazinolysis of the copolymer containing methyl ester groups poly(HPMA-co-MA-AH-OMe) while removing sulphur-containing end groups originating from the transfer agent at the ends of the polymer chains and blocking the resulting end thiol groups by N- (5 - f ⁇ uoresceinyl) - maleimide.
  • Example 3c Synthesis of polymer precursor poly(HPMA-co-MA-AH-NHNH 2 ) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous blocking of the end thiol group of the polymer carrier and introduction of an amino group at the end of the polymer chain
  • a hydrazide groups-containing copolymer was prepared by hydrazinolysis of a copolymer containing methyl ester groups poly(HPMA-co-MA-AH-OMe) while removing sulphur-containing end groups originating from the transfer agent at the ends of the polymer chains and blocking the resulting end thiol groups by N-aminoethylmaleimide trifluoro acetate.
  • Example 3d Synthesis of diblock polymer precursor poly(HPMA-co-MA-AH-NHNH 2 )-S- S-poly(HPMA-co-MA-AH-NHNH 2 ) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous mutual reaction of end thiol groups of polymeric carriers wherein
  • Example 2a A solution of poly(HPMA-co-MA-AH-MeO) prepared in Example 2a (500 mg, 0.20 mmol of methyl ester groups) and dithiothreitol (70 mg, 0.45 mmol) in 3.75 mL of dried distilled methanol was bubbled with argon for 5 minutes and then kept under an argon atmosphere. 3.75 mL of hydrazine hydrate (77 mmol) was added to the reaction mixture. The reaction was allowed to proceed for 5 minutes and then precipitated into ethyl acetate to remove dithiothreitol.
  • the precipitated polymer was dissolved in methanol and then the residual hydrazine hydrate together with the solvent was removed on a rotary evaporator under an oil pump vacuum (1 mbar, 1.5 h) to form a diblock copolymer.
  • the product was isolated by precipitation into ethyl acetate (total 200 mL) and then filtered and dried as described above.
  • Example 4 Synthesis of polymer conjugate poly(HPMA-co-MA-AH-NHNH 2 ) with fluorescent label Cyanine 5.5 at the end of the polymer chain
  • the poly(HPMA-co-MA-AH-NHNH 2 ) polymer with end amino groups prepared according to Example 3c was used to bind the fluorescent label Cyanine 5.5 NHS ester.
  • Copolymers with doxorubicin (DOX) attached to a PHPMA carrier by a hydrolytically cleavable hydrazone bond were prepared by reacting copolymers containing hydrazide groups poly(HPMA-co-MA-AH-NHNH 2 ) with doxorubicin hydrochloride (DOX.HC1) in methanol catalysed by acetic acid.
  • DOX doxorubicin
  • Copolymers with dexamethasone attached to a PHPMA carrier by a hydrolytically cleavable hydrazone bond were prepared by reacting hydrazide groups-containing copolymers poly(HPMA-co-MA-AH-NHNH 2 ) with a dexamethasone derivative, dexamethasone oxo -propyl benzoate (DEX), in methanol catalysed by acetic acid.
  • DEX dexamethasone oxo -propyl benzoate
  • the IC50 values are reported in ng doxorubicin/mL and were calculated as the average of several independent assays.

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Abstract

The present invention relates to an effective method of preparation of copolymers of N-(2-hydroxypropyl) methacrylamide (HPMA) and methacryloylaminoacylhydrazide, suitable for binding of drugs containing a keto group, for pH-controlled drug release. The method comprises the steps: a) providing of the monomers of the linear statistical copolymer; b) RAFT polymerisation of monomers of the linear statistical copolymer; c) introduction of hydrazide groups, and simultaneous in situ modification of the end groups of the linear statistical copolymer, optionally, binding a biologically active molecule to the ends of the polymer chain. The present invention further relates to a method of preparation of a conjugate of the linear statistical copolymer with a drug by means of a pH-sensitive hydrolysable hydrazone bond.

Description

Method for the preparation of polymeric carriers for pH-controlled drug release and their conjugates with drugs
Field of Art
The invention relates to a method for the preparation of polymeric drug carriers enabling targeted transport and controlled release of active substances in the body, in particular in tumour tissue, inflammatory tissue, tumour cells and cells of the immune system. The use of these polymeric conjugates focuses on the targeted therapy of cancer, inflammatory and autoimmune diseases in human medicine. The preparation method is well reproducible and provides high yields. It allows precise control of the molar masses of polymer precursors with low dispersity and precisely defined structure. Last but not least, this method of preparation is easily transferable to an industrial scale.
Background Art
As part of the development of new medicinal products, great attention is paid to drug delivery systems, which make it possible to guarantee the suitable pharmacokinetics and high efficacy of drugs with minimal side effects. Systems based on liposomes, micelles, polymersomes, nanoparticles and water-soluble polymer-drug conjugates are widely studied. Natural or synthetic macromolecules are commonly used in the design and synthesis of these systems. In most of these drug delivery systems, in order to achieve the desired drug effect, it is necessary and crucial to ensure the release of the carried bioactive substance from its delivery system at a given site of the body, e.g. tumour, inflammatory part, while during transport to the site of action the whole system is stable, does not release active substances and is therefore without side effects. An important feature of these transport systems is the large size in the aqueous environment, which can ensure preferential deposition of the drug delivery system in the tumour tissue of a number of solid tumours (the so-called EPR effect) and in inflammatory tissue (the so-called ELVIS effect). The release of the active drug from the delivery system can advantageously be achieved via a biodegradable linker used to bind the drug to a polymer, the degradation of which in the target tissue leads to a targeted and controlled activation of the drug, preferably in this tissue. Systems using a biodegradable linker to activate a biodegradable polymeric material often use water-soluble polymeric materials, with a significant group of such systems being polymeric drugs prepared from A- (2-hyd oxyp opyl) methacrylamide (HPMA) copolymers. Significantly higher anti-tumour effect compared to commonly used cytostatics and a significant reduction of side, especially toxic, effects on a healthy organism were demonstrated by polymeric carriers based on HPMA copolymers carrying a drug bound to the carrier by a hydrolytically labile hydrazone bond. The synthesis of such conjugates was performed first by classical radical polymerisation, which led to the preparation of polymer systems with a relatively wide distribution of molecular weights of polymers with a dispersity D around 2. Later, a method of controlled radical reversible addition-fragmentation chain transfer (RAFT) polymerisation was described, enabling the preparation of copolymers with a significantly lower dispersity of about 1.2 (Moad G. et al., Polymer, 2008. 49(5)). Also polymeric carriers based on HPMA copolymers containing hydrazide groups suitable for hydrazone bonding of drugs were prepared by RAFT polymerisation (Chytil P. et al., Eur. J. Pharm. Sci., 2010, 41, 73-82). However, hydrazide groups need to be protected during polymerisation. The authors of the publication therefore applied protection with a tert- butoxycarbonyl (Boc) group. In the next step, the dithiobenzoate groups at the end of the polymeric carrier were removed by reduction with sodium borohydride and the resulting -SH groups were blocked by reaction with N- ethylmaleimide. Only then were the Boc groups removed with trifluoro acetic acid (TFA). The disadvantage of this carrier synthesis is the need for several subsequent steps after polymerisation. In particular, the step of deprotecting the hydrazide groups is a step which is difficult to reproduce and does not allow easy preparation of larger batches of the polymer required for industrial application. Also, the final purification of the polymer by gel filtration means complications for the preparation of a larger amount of the carrier. The described procedure for the synthesis of the carrier was also used in other publications. The basis is always the copolymerisation of HPMA with a monomer bearing Boc protected hydrazide groups (e.g. Subr V. et al. Biomacromolecules 2014, 15 (8), 3030-3043, Chytil P. et al. Macromol. Biosci. 2015, 15 (6), 839-850, Lomkova E. et al. Biomacromolecules 2016, 17 (11), 3493-3507). The blocking of the end groups and the subsequent deprotection of the hydrazide groups differed slightly. Excess initiator was used instead of reduction with borohydride. Recently, a work has been published in which instead of incubation with TFA a polymer dissolved in distilled water at 100 °C is used to remove Boc groups (Koziolova E. et al. Biomacromolecules 2018, 19 (10), 4003-4013).
It is an object of the present invention to provide such a process for the preparation of drug carriers enabling drug binding via a pH labile hydrolysable hydrazone bond which would give high yields, be well reproducible and allow precise control of molar masses of polymer precursors with low dispersity and precisely defined structure. The process should also be easily transferable to an industrial scale.
Disclosure of the Invention
The object of the present invention is a method for the preparation of polymeric carriers based on HPMA copolymers suitable for binding drugs by means of a pH-sensitive hydrolysable hydrazone bond. In addition, the process for preparing the polymeric carrier according to the present invention makes it possible to introduce biologically active substances at the ends of the polymer chains.
The polymeric carrier consists of a linear statistical copolymer of general formula (I),
Figure imgf000004_0001
containing at least 75 mol % of HPMA monomer units (75 to 99.5 mol % HPMA) and from 0.5 to 25 mol %, based on the total number of monomer units, structural units of formula (II) :
Figure imgf000004_0002
wherein X is selected from the group consisting of alkylene having 1 to 8 carbon atoms; phenylene; -(CH2)q-(C(O)-NH-(CH2)r)p-, wherein p = 1 to 5, and q and r are independently selected from 1, 2 and 3; wherein the CH2 groups of the substituent X may be optionally substituted independently with one or more natural amino acid side chains; X is preferably selected from the group comprising -CH2-CH2- and -CH2-CH2-CH2-CH2-CH2-; x is an integer in the range of from 25 to 700; preferably in the range of from 120 to 300; Ri is a radical leaving group of the transfer agent used; preferably Ri is selected from the group comprising 2-cyano-2-propyl and 5-carboxy-2-cyano-2-pentyl; and R2 is a thioether derivative given by the structure of the double bond compound (C=C) used after the addition of the SH end groups of the polymer chain or by the interaction of the SH end groups of a linear statistical copolymer to form a disulphide-linked diblock polymer; preferably R2 is selected from the group comprising 2-(ethenylsulphonyl)ethyl, 1-ethyl-2,5- dioxopyrrolidin-3-yl, 1-(2-hydroxyethyl)-2,5-dioxopyrrolidin-3-yl, 1-(2-propynyl)-2,5- dioxopyrrolidin-3-yl, 1-(3-carboxy-l-propyl)-2,5-dioxopyrrolidin-3-yl, 1-(2-aminoethyl)-2,5- dioxopyrrolidine-3-yl, 1-(3-aminopropyl)-2,5-dioxopyrrolidin-3-yl; and
Figure imgf000005_0001
wherein the molar mass of the linear statistical copolymer is in the range of from 4,000 to 100,000 g/mole, preferably from 20,000 to 40,000 g/mole.
Natural amino acids can be understood as naturally occurring acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, arginine, cysteine, glutamine, glycine, proline, tyrosine, alanine, aspartic acid, asparagine, glutamic acid, serine, selenocysteine. Their side chains are to be understood as chains attached to the alpha-carbon of a particular amino acid.
A semitelechelic linear copolymer is a statistical copolymer formed by a radical polymerisation reaction. Thus, the end groups of the resulting linear copolymer contain parts of molecules of the polymerisation initiator (e.g. azo initiators, such as 2,2'-azobis(2-methylpropionitrile) (AIBN), 4,4'-azobis(4-cyanopentanoic acid) (ACVA), 2,2'-azobis(4-methoxy-2,4-dimethylpentanenitrile) (V70)), and of the transfer agent (preferably selected from the group consisting of 2-cyano-2- propyl benzodithioate, 4-cyano-4-(thiobenzoylthio)pentanoic acid, 2-cyano-2-propyldodecyl trithio-carbonate, 2-cyano-2-propylethyltrithiocarbonate and 4-cyano-4-[(dodecylsulphanylthio- carbonyl)sulphanyl]pentanoic acid).
Thus, the end groups of the copolymer contain at one end a radical leaving group of the transfer agent, preferably 2-cyano-2-propyl, or 5-carboxy-2-cyano-2-pentyl. At the other end there is a dithiobenzoate or trithiocarbonate group, which is reduced in situ to a thiol group, which is subsequently added to a double bond compound (C=C); preferably selected from the group comprisingN- substituted maleimide or S- substituted vinyl sulphone; more preferably, the double bond compound (C=C) is selected from the group comprising divinyl sulphone, carboxy-PEG vinyl sulphone, N-ethylmaleimide, N-(2-hydroxyethyl)maleimide, N-propargylmaleimide, 3- maleimidopropionic acid, azido-PEG-maleimide and N-(5-fluoresceinyl)-maleimide, or the end thiol groups are converted to amine groups using N-aminoethylmaleimide trifluoro acetate, or N- (3-aminopropyl)maleimide trifluoro acetate, or after the formation of the hydrazide group by reaction with a reducing agent and hydrazine, the reducing agent being preferably dithiothreitol, the reducing agent is removed from the reaction mixture followed by spontaneous conjugation of the SH end groups of the linear statistical copolymer to form disulphide-linked diblock polymers; wherein the reaction takes place in an inert atmosphere (e.g. Ar or N2) at room temperature and in a solvent preferably selected from the group comprising methanol, ethanol, dimethyl sulphoxide, dimethyl acetamide and dimethyl formamide.
In one preferred embodiment, the natural amino acid side chain is selected from the group comprising methyl, isopropyl, isobutyl, -CH(CH3)(CH2CH3), -CH2OH, -CH(OH)(CH3), -CH2- (C6H4)OH, -(CH2)2-S-CH3, -CH2SH, -(CH2)4-NH2, -CH2COOH, -CH2C(O)NH2, -(CH2)2COOH, -(CH2)2C(O)NH2, -(CH2)3NH-C(=NH)(NH2), benzyl.
In one preferred embodiment, X is selected from the group comprising -CH2-, -(CH2)2-, -(CH2)5- ; -C(H)(CH2-Phe)-, -C(H)(CH-iPr)-, -C(H)(sec-Bu)-; -CH2-C(O)-NH-CH2-;
-CH2-C(O)-NH-(CH-C(H)(CH2-Phe)-C(O)-NH-C(H)(CH-iPr)-NHCH2-.
The method for the preparation of polymeric carriers of general formula (I) according to the present invention comprises the following steps: a) providing monomers of the polymeric carrier, thus providing HPMA (commercially available) and providing a monomer of general formula (III),
Figure imgf000006_0001
wherein X is as defined above, and Y is selected from the group consisting of hydroxyl, (C1-C6) alkoxy, benzoxy, 4-nitrophenoxy, 2,3,4,5,6-pentafluorophenoxy, succinimidyl, (C1-C6) alkylthio group and thiazolidine-2-thione group; preferably Y is selected from the group consisting of methoxy, ethoxy, tert-butoxy, tert- butylthio and thiazolidine-2-thione group; b) radical RAFT polymerisation of monomers of the polymeric carrier from step a); c) introduction of hydrazide groups instead of the substituent Y, while in situ modifying the end groups of the linear statistical copolymer to give the statistical copolymer of the general formula
(i); d) optionally, binding a biologically active molecule to the R2 end group of the polymer chain.
Step a) of providing polymeric carrier monomers comprises providing A- (2 - hydroxypropyl) methacrylamide (HPMA) and a monomer of general formula (III).
HPMA is commercially available and its synthesis is published (e.g. Chytil P. et al., Eur. J. Pharm. Sci., 2010, 41, 73-81).
Figure imgf000007_0001
HPMA
The synthesis of monomers of general formula (III) lies in the reaction of an ester, thioester or imide of amino acids and compounds of formula Y-C(O)-X-NH2, where X and Y are as defined above, with methacryloyl chloride (this reaction may also be called methacryloylation) according to the Schotten-Bauman method, preferably performed in diethyl ether, or in dichloro methane in the presence of anhydrous sodium carbonate, or in water in the presence of alkali hydroxide. The starting compounds of formula Y-C(O)-X-NH2 are commercially available. Optionally, the step of methacryloylation of a commercially available compound of formula HO-C(O)-X-NH2 followed by an esterification, thioesterification, or imidation of a carboxyl group, may be included, preferably by the carbodiimide method using dicyclohexylcarbodiimide, diisopropylcarbodiimide, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide, or other reagents using benzotriazol-l-yloxytripyrrolidinophosphonium hexafluorophosphate or (2-(l H- benzotriazol- 1 -yl)- 1 , 1 ,3 ,3-tetramethyluronium hexafluorophosphate. Step b) of polymerisation of monomers of the polymeric carrier lies in the controlled radical RAFT polymerisation of HPMA with a monomer of general formula (III) in a molar ratio of HPMA: monomer of formula (III) in the range of from 99.5:0.5 to 75:25. The polymerisation takes place at a temperature in the range of from 30 to 100 °C, preferably from 40 to 80 °C, and in a solvent preferably selected from the group comprising dimethyl sulphoxide, dimethyl acetamide, dimethyl formamide, dioxane, tert-butyl alcohol, water, aqueous buffer or mixtures thereof, initiated by an initiator, preferably selected from the group comprising, in particular, azo initiators, such as 2,2'-azobis(2-methylpropionitrile) (AIBN), 4,4'-azobis (4-cyanopentanoic acid) (ACVA), 2,2'-azobis( 4-methoxy-2,4-dimethylpentanenitrile) (V70), and in the presence of a transfer agent, preferably selected from the group of 2-cyano-2-propyl benzodithioate, 4- cyano-4-(thiobenzoylthio) pentanoic acid, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyano-2- propyl ethyl trithiocarbonate, and 4-cyano-4- [(dodecyl sulphanyl thiocarbonyl)sulphanyl] pentanoic acid. The molar mass Mn of the copolymers thus prepared is in the range of from 4,000 to 100,000 g/mol, preferably from 20,000 to 40,000 g/mol.
In one preferred embodiment, the synthesis of the polymer precursors is carried out at a molar ratio of initiator : transfer agent in the range of from 1:1 to 1:10.
In one preferred embodiment, the synthesis of the polymer precursors is carried out at a molar ratio of transfer agent : monomers in the range of from 1:50 to 1:1000.
Step c) of introduction of hydrazide groups while modifying the end groups of the polymeric carrier lies in converting the group Y (reactive esters, thioesters and imides) to hydrazide groups (-NH-NH2) and in situ modification (removal) of sulphur-containing end groups of the polymeric carrier originating from the transfer agent. First, a reducing agent, preferably dithiothreitol, and hydrazine are added to the product of step b), followed by hydrazinolysis with hydrazine (hydrazine hydrate), and then the end thiol groups are added to: i) compounds bearing a double bond (C=C) to form a thioether bond. The double bond compounds are preferably selected from the group comprising N- substituted maleimide and S- substituted vinyl sulphone; more preferably selected from the group comprising divinyl sulphone, carboxy-PEG vinyl sulphone, A-cthyl maleimide. A- (2 - hydroxycthyl)maleimidc, N- propargylmaleimide, 3-maleimidopropionic acid, azido-PEG-maleimide and A-(5-fluoresceinyl)- maleimide; or ii) the end thiol groups are converted to amines using A-aminoethylmaleimide trifluoroacetate, or A-(3-aminopropyl)maleimide trifluoroacetate; or iii) the reducing agent is removed from the reaction mixture followed by spontaneous conjugation of the SH end groups (in a basic medium secured by the presence of residual hydrazine in the reaction mixture) of a linear statistical copolymer to form disulphide-linked diblock polymers; wherein the reaction takes place in an inert atmosphere (e.g. Ar or N2) at room temperature and in a solvent preferably selected from the group comprising methanol, ethanol, dimethyl sulphoxide, dimethyl acetamide and dimethyl formamide; to give the linear statistical copolymer of general formula (I) as defined above. The presence of a reducing agent (e.g. dithiothreitol) in the reaction mixture ensures that most of the SH groups are retained from their reaction to the disulphide, while if the dithiothreitol is removed before complete removal of the base (hydrazine hydrate), a diblock is formed. If a compound containing a double bond (C=C) is added, the SH groups are blocked and no diblock copolymer with an -S-S- bond is formed.
The resulting structure of the statistical linear copolymer (polymeric drug carrier) can thus be expressed by the general formula (IV)
Figure imgf000009_0001
or general formula (V) (disulphide-linked diblock polymer)
Figure imgf000009_0002
wherein X is as defined above; x is an integer ranging from 25 to 700; preferably ranging from 120 to 300; Ri is given by the structure of the transfer agent used and consists of a so-called radical leaving group, preferably 2-cyano-2-propyl, or 5-carboxy-2-cyano-2-pentyl; and R2 is given by the structure of the double bond compound (C=C) used after the addition ofthe SH end groups of the polymer chain; preferably R2 is selected from the group comprising 2-
(ethenylsulphonyl)ethyl, l-ethyl-2,5-dioxopyrrolidin-3-yl, 1-(2-hydroxyethyl)-2,5- dioxopyrrolidin-3-yl, 1-(2-propynyl)-2,5-dioxopyrrolidin-3-yl, 1-(3-carboxy-l-propyl)-2,5- dioxopyrrolidin-3-yl, 1-(2-aminoethyl)-2,5-dioxopyrrolidine-3-yl, or 1-(3-aminopropyl)-2,5- dioxopyrrolidin-3-yl group.
In one embodiment, step c) may optionally be followed by step d), in which a biologically active molecule may be attached to the R2 group of general formula (I), if R2 is not
Figure imgf000010_0001
(thus via the compound with a double bond (C=C), introduced into the polymeric structure by the reaction of end thiol groups of the polymer with a bifunctional agent containing a double bond and another functional group, preferably a primary amino group (the bifunctional agent is A- a m i n o c t h y 1 m a 1 c i m i dc trifluoroacetate, or A- (3 - a m i n o p ro p y 1 ) m a 1 c i m i dc trifluoro acetate), a carboxyl group (the bifunctional agent is maleimidopropionic acid, or carboxy-PEG vinyl sulphone), ethynyl group (the bifunctional agent is /V-propargylmaleimide), or an azide group (the bifunctional agent is azido-PEG-maleimide)). The biologically active molecule is selected from the group comprising fluorescent labels, chelators for radionuclides, chelators for contrast agents for nuclear magnetic resonance, targeting groups, oligopeptides, oligosaccharides, peptides, scFc fragments, monoclonal antibodies and specific cell-surface receptor ligands. This results in a polymeric conjugate of this biologically active molecule with the linear statistical polymer, which can be further used for fluorescent labelling, radionuclide binding for radiotherapy, Gd3+ binding for MRI imaging or for targeted transport of the polymer to specific cell receptors. An example of such an addition of a biologically active substance is the reaction of the end amine group with, for example, ester groups of other biologically active substances, which allows a great variability and universal use of the polymer.
In one preferred embodiment, the biologically active molecule is a fluorescent label, for example fluorescein, Cyanine 5.5, Cyanine 7, Cyanine 7.5, Dyomics-676, Dyomics-676, Alexa fluor-488; chelators for radionuclides, preferably deferoxamine, DOT A, NOT A, tyrosinamide; targeting groups for targeted biodistribution, preferably targeting oligopeptides, especially selected from the group comprising GE-7 (NPVVGYIGERPQYRDL oligopeptide), GE-11 (YHWYGYTPQNVI oligopeptide), RGD (arginylglycylaspartic acid); scFc fragments; and monoclonal antibodies, preferably anti-CD20, anti-CD38, anti-CD19, anti-Her2Neu, anti-GD2. The method of binding of a particular known biologically active substance to an amino group, carboxyl group, ethynyl group or azide group of the linear statistical copolymer of general formula (I) may be carried out by standard reactions known to those skilled in the art based on standard knowledge in the technical field.
For example, a fluorophore Cyanine 5.5 can be attached to the amino group of a polymer via the NHS ester of Cyanine 5.5. Similarly, other fluorescent labels, e.g. Dyomics-676, Dyomics-782, Alexa fluor-488, containing reactive esters, may be attached.
Fluorescein can be attached to the linear statistical copolymer already in step c) using N-( 5- fluoresceinyl)-maleimide as a double bond (C=C) compound, while blocking the end thiol groups. Similarly, deferoxamine can be bound already in step c) using deferoxamine maleimide. Oligopeptides, e.g. GE-7, GE-11, RGD, containing an azide group, i.e. oligopeptides terminated with azidopentanoic acid, can be attached by a catalysed click reaction. Similarly, fluorescent labels or chelators containing an azide group can be attached.
Analogously, any biologically active substance containing a reactive functional group capable of conjugation with an amino group, a carboxyl group, an ethynyl group or an azide group can be attached to the linear statistical copolymer, or the biologically active substance can be converted to a derivative thereof containing this reactive functional group.
Another object of the present invention is a method for preparation of a conjugate of the linear statistical copolymer of general formula (I) based on HPMA copolymers, as defined above, with a drug, in particular by means of a pH-sensitive hydrolysable hydrazone bond. This process comprises preparing the polymeric carrier according to steps a) to c) and optionally step d) above, followed by step e) of linking the drug to a structural unit of general formula (II) of the linear statistical copolymer, as defined above, by a hydrazone bond to form a conjugate of the linear statistical copolymer of formula (I) with the drug.
The preparation process comprises the reaction of the linear statistical copolymer from step c) or d) with drug, or a derivative thereof containing a keto group, catalysed by a defined amount of acetic acid leading to the formation of a hydrazone bond (-C(=O)- the group of drug or derivative thereof reacts with the -NH-NH2 group of the polymeric carrier side chain to form a hydrazone bond between the drug/drug derivative and the polymeric carrier side chain). Preferably, the drug is selected from the group comprising anti-tumour drugs, anti-inflammatory drugs or immuno modulators. More preferably, the drug is selected from the group comprising anthracycline, doxorubicin, dexamethasone, pirarubicin, epirubicin, ritonavir, docetaxel, paclitaxel, larotaxel, or oxo derivatives thereof (containing at least one keto group). The reaction may be carried out in methanol, dimethyl sulphoxide, dimethyl formamide, dried ethanol and dimethyl acetamide. The synthesis of polymer-drug conjugates is based on the previously described method of binding of doxorubicin (Etrych, T., et al., J. Control. Release, 2001. 73(1): p. 89-102), pirarubicin (Nakamura, H., et al., J. Control. Release, 2014. 174: p. 81-87) and taxol ketoderivatives (Etrych, T., et al., Mol. Pharm., 2010. 7(4): p. 1015-1026), dexamethasone (Krakovicova, H., T. Etrych, and K. Ulbrich, Eur. J. Pharm. Sci., 2009. 37(3-4): p. 405-412), mitomycine C (Kostkova, H., et al, Macromol. Biosci., 2013. 13(12): p. 1648-60), ritonavir ketoderivatives (Koziolova, E., et al, J. Control. Release, 2016. 233: p. 136-146) and other drugs containing an amino or hydroxyl group.
Syntheses of polymer-drug conjugates are known in the art, so a person skilled in the art would be familiar with which groups of which drugs are reactive and will react with the -NH-NH2 group of the polymer.
The following citations are given as an example:
The binding of doxorubicin to the -NH-Nth group is described, for example, on page 95 of the article ‘New HPMA copolymers containing doxorubicin bound via pH-sensitive linkage: synthesis and preliminary in vitro and in vivo biological properties’, T. Etrych et al., Journal of Controlled Release 73 (2001) 89-102.
The binding of pirarubicin to the -NH-NH2 group is described, for example, on page 137 of the article Overcoming multidrug resistance in Dox-resistant neuroblastoma cell lines via treatment with HPMA copolymer conjugates containing anthracyclines and P-gp inhibitors^ E. Koziolova et al. (2016) 136-146 or on page 82 of the article ‘Two step mechanisms of tumour selective delivery of N-(2-hydroxypropyl) methacrylamide copolymer conjugated with pirarubicin via an acid-cleavable linkage’, H. Nakamura et al., Journal of Controlled Release 174 (2014) 81-87 (this article states that the synthesis was performed similarly to doxorubicin) .
The binding of epirubicin to the -NH-NH2 group is described, for example, on page 3453 of the article ‘Superior Penetration and Cytotoxicity of HPMA Copolymer Conjugates of Pirarubicin in Tumor Cell Spheroid’, H. Nakamura et al., Mol. Pharmaceutics 2019, 16, 3452-3459.
The binding of paclitaxel and docetaxel to the -NH-NH2 group is described, for example, on page 1017 - 1019 of the article ΉRMA Copolymer Conjugates of Paclitaxel and Docetaxel with pH-Controlled Drug Release’, T. Etrych et al., Mol. Pharmaceutics 2010, 7 (4), 1015-1026. Mitomycine C binds to the -NH-NH2 group according to pages 1650 - 1651 of the article ΉRMA Copolymer Conjugates of DOX and Mitomycin C for Combination Therapy: Physicochemical Characterisation, Cytotoxic Effects, Combination Index Analysis, and Anti- Tumor Efficacy’, H. Kostkova et al, Macromol. Biosci. 2013, 13, 1648-1660.
The binding of dexamethasone to the -NH-Nth group is described, for example, on pages 272 - 273 of the article ‘Synergistic effect of HPMA copolymer-bound doxorubicin and dexamethasone in vivo on mouse lymphomas’, H. Kostkova et at, Journal of Bioactive and Compatible Polymers, 2011, 26 (3), 270-286 or on pages 407 - 408 of the article ΉRMA-based polymer conjugates with drug combination’, H. Krakovicova et at, European Journal of Pharmaceutical Sciences 37 (2009) 405-412 or on page 464 of the article ‘Nanomedicines for Inflammatory Arthritis: Head-to-Head Comparison of Glucocorticoid-Containing Polymers, Micelles, and Liposomes’, L. Quan et al., ACS Nano, 2013, 8(1), 458-466.
The binding of ritonavir to the -NH-NH2 group is described, for example, on pages 3033 - 3035 of the article ‘Synthesis of Poly[N-(2-hydroxypropyl)methacrylamide] Conjugates of Inhibitors of the ABC Transporter That Overcome Multidrug Resistance in Doxorubicin-Resistant P388 Cells in Vitro’, V. Subr et al, Biomacromolecules 2014, 15, 3030-3043.
In one preferred embodiment, the initial concentration of the polymeric carrier for reaction with the keto groups of the drug is in the range of from 100 to 190 mg/mL, the concentration of the glacial acetic acid is in the range of from 30 to 80 mg/mL, and the concentration of the drug/drug oxo derivative is in the range of from 1 to 50 mg/mL, more preferably the initial polymer concentration for reaction with the keto groups of the drug is 170 mg/mL, the acetic acid concentration is 55 mg/mL, and the drug concentration is 20 mg/mL at 25 °C.
An optional further step f) of preparing the conjugate is the final purification of the conjugate from free unbound drug by gel filtration, for example using a column packed with cross-linked dextran (e.g. Sephadex LH-20) and methanol as mobile phase. Gel filtration for polymer purification is known to the person skilled in the art, who would therefore know which stationary phase to use for gel filtration.
Thus, the present invention provides a reproducible method for the preparation of very well defined polymeric drug carriers based on HPMA copolymers, allowing the drugs to be bound by a pH-labile hydrazone bond to the carrier. This new method of preparing polymeric carriers by means of controlled polymerisation makes it possible to increase the yields in the polymerisation and, thanks to the advantageous copolymerisation parameters close to one, to control the content of the comonomer unit (according to formula II) in the carrier; the synthesis is significantly easier and cheaper, it allows ‘scale-up’ to large batches and the reproducibility of the synthesis is very good. The biological activity of conjugates of prepared polymeric carriers with drugs is the same as that of conjugates of previously prepared carriers.
Brief description of Figures
Figure 1: Time dependence of amount of DEX liberated from the conjugate po 1 y (H P M A - co- A H - NH-N=DEX) incubated in buffers of pH 5 and pH 7.4, at 37 °C: DEX, pH 5 (grey); DEX, pH 7.4 (black).
Examples
Characterisation of polymer precursors and conjugates
The prepared copolymers were characterized by determining the weight and number average molar masses (Mw, Mn ) and the corresponding dispersity index (£)) by gel permeation chromatography (GPC) on a system equipped with a PDA detector (Shimadzu, Japan), RI detector (Optilab REX, Wyatt Technology Corp ., USA) and a multi-angle light scattering detector (DAWN Heleos-II, Wyatt Technology Corp., USA). For characterisation, a TSK 3000 Super SW column was used for SEC and a mixture of methanol (80 %) and 0.3 M acetate buffer pH 6.5 (20 %) as the mobile phase. The sample concentration was 3 mg/mL in all cases.
The content of hydrazide groups was determined using the TNBSA test. The content of methyl ester groups and other esters was determined by nuclear magnetic resonance (NMR) on a Bruker Avance III 600 MHz spectrometer in (CD3)2SO. The content of bound drugs was determined either spectrophotometrically or by HPLC after total hydrolysis, i.e. release from the polymeric carrier.
Example 1: Synthesis of monomers
A-(2-hydroxypropyl) methacrylamide (HPMA)
HPMA was prepared according to the procedure previously described (Chytil P. et al., Eur. J. Pharm. Sci., 2010, 41, 73-82). The product was chromatographically pure. 1 H-NMR (300 MHz, (CD3)2SO, 296 K): d 1.00-1.02 (d, 3H, CHOH-CH3), 1.85 (s, 3H, CH3), 3.00-3.12 (m, 2H, CH2), 3.64-3.73 (m, 1H, CH), 4.68-4.70 (d, 1H, OH), 5.30 and 5.66 (d, 2H, CH2=), 7.59 (br, 1H, NH). N- methacryloy 1-3 -aminopropionic acid methyl ester (MA-AP-OMe)
Figure imgf000015_0001
Methyl 3-aminopropionate hydrochloride (30 g, 0.215 mol) was dissolved in 350 mL of dichloromethane with vigorous stirring at room temperature. The solution was cooled to 10 - 15 °C and anhydrous sodium carbonate (67 g, 0.645 mol) was added, the temperature was reduced to 5 - 10 °C and then a solution of methacroyl chloride (22.5 g, 0.215 mol (eq.)) in 100 mL of dichloromethane was added dropwise at such a rate that the temperature of the reaction mixture does not exceed 15 °C. After consumption of all methacroyl chloride, the mixture was stirred for a further 45 minutes at 15 - 20 °C, then the cooling bath was removed, the suspension was stirred for a further 20 minutes, filtered off on a No. 3 frit, washed with 300 mL dichloromethane and the filtrate was evaporated to dryness on a rotary evaporator. The yield was 29.5 g of product (84 %). 1H-NMR (300 MHz, (CD3)2SO, 295 K): 1.83 (s, 3H, CH3), 3.30-3.43 (m, 4H, CH2-α, CH2-β), 5.33 (s, 3H, OCH3), 5.60 and 5.96 (d, 2H, CH2=), 7.97 (br, 1H, NH). The product was chromatographically pure.
N- met hacry lo y 1-6-a m i no hexano ic acid methyl ester (MA-AH-OMe)
Figure imgf000015_0002
MA-AH-OMe was prepared according to the procedure described above using methyl 3- aminohexanoate hydrochloride. 1H-NMR (300 MHz, (CD3)2SO, 295 K): d 1.20-1.27 (m, 2H, CH2-γ), 1.40-1.54 (m, 4H, OH2-b, CH2-δ), 1.82 (s, 3H, CH3), 2.28 (t, 2H, CH2-a), 3.04-3.34 (m, 2H, CH2-ε), 3.57 (s, 3H, OCH3), 5.28 and 5.60 (d, 2H, CH2=), 7.88 (br, 1H, NH). The product was chromatographically pure.
Example 2a: Synthesis of polymer precursor - HPMA copolymer with MA-AH-OMe (poly(HPMA-co-MA-AH-OMe))
Figure imgf000016_0001
Poly(HPMA-co-MA-AH-OMe) copolymer was prepared by controlled radical RAFT copolymerisation of HPMA and MA-AH-OMe (prepared according to Example 1) initiated by AIBN in the presence of RAFT transfer agent 2-cyano-2-propyl benzodithioate in a tert-butyl alcohol and dimethyl sulphoxide at 70 °C.
HPMA (4.0 g, 27.9 mmol) and MA-AH-OMe (0.377 g, 1.8 mmol) were dissolved in 35.7 mL of tert-butyl alcohol, to the solution were added 2-cyano-2-propyl benzodithioate (18.8 mg, 84.9 μmol) and AIBN (7.0 mg, 42.5 μmol) dissolved in 4.0 mL of dimethyl sulphoxide. The polymerisation mixture was placed in an argon atmosphere in a polymerisation vial (50 mL volume), bubbled with argon for 10 minutes and sealed. The polymerisation vial was placed in a thermostat at 70 °C.
The polymerisation mixture was removed from the thermostat after 16 h, cooled in a bath to the room temperature, and the polymer was isolated by precipitation into ethyl acetate (total 800 mL). The precipitated polymer was allowed to settle for about 0.5 h, the solution above the precipitate was sucked off and the polymer was isolated by filtration on a S4 frit. The precipitate was washed with ethyl acetate, transferred to large Petri dishes and dried at room temperature under a diaphragm pump vacuum for about 1 h.
The polymer was dissolved in 40 mL of methanol (100 mL Erlenmeyer flask) by means of ultrasound and precipitated into 800 mL of ethyl acetate in the same manner as in the first isolation. After about 0.5 h of sedimentation, the precipitated polymer was isolated by filtration on a S4 frit, washed with ethyl acetate and dried to constant weight (about 5 h) on a diaphragm pump and finally dried under an oil pump vacuum.
Characterisation of the copolymer: Yield 3.07 g (70 %), methyl ester group content 5.3 mol %, molar mass Mw = 38,800 g/mol, dispersity index D = 1.19.
Other poly (HPMA-co- MA-AH-OMe) copolymers differing in the molar ratio of monomer units and RAFT transfer agent in the polymerisation mixture were prepared analogously (see Table 1).
Figure imgf000017_0002
Copolymers were prepared analogously using other RAFT agents: S-2-cyano-2-propyl-S -ethyl trithiocarbonate, 4-cyano-4-(thiobenzoylthio) pentanoic acid, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyano-2-propyl ethyl trithiocarbonate and 4-cyano-4- [(dodecylsulphanyl- thiocarbonyl)sulphanyl] pentanoic acid.
Example 2b: Synthesis of polymer precursor - HPMA copolymer with MA-AP-OMe (poly(HPMA-co-MA-AP-OMe))
Figure imgf000017_0001
The execution and procedure of polymerisation of poly(HPMA-co-MA-AP-OMe) were the same as in Example 2a, the difference being in the composition of the polymerisation mixture. The composition of the polymerisation mixture was as follows: HPMA (4.0 g, 27.9 mmol) and MA- AP-OMe (0.308 g, 1.8 mmol) dissolved in 35.7 mL of tert- butyl alcohol, 2-cyano-2-propyl benzodithioate (18.8 mg, 84.9 μmol) and AIBN (7.0 mg, 42.5 μmol) dissolved in 4.0 ml of dimethyl sulphoxide. The polymerisation temperature was 70 °C, the polymerisation time was 16 h. The polymer solution was precipitated into ethyl acetate, and the polymer product was precipitated in a 20-fold volume of precipitant. The polymer was freed of low molecular weight impurities by precipitation from methanol into ethyl acetate. The yield was 3.1 g (72 %), the content of methyl ester groups was 5.1 mol %, molar mass Mw = 37,700 g/mol, dispersity D = Example 3a: Synthesis of polymer precursor poly(HPMA-co-MA-AH-NHNH2) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous blocking of the end thiol group of the polymeric carrier
Figure imgf000018_0001
The hydrazide groups-containing copolymer poly(HPMA-co-MA-AH-NHNH2), was prepared by hydrazinolysis of the methyl ester groups-containing copolymer poly(HPMA-co-MA-AH- OMe) prepared in Example 2a, while removing sulphur-containing end groups derived from of the transfer agent at the ends of polymer chains and blocking of the resulting end thiol groups with N-ethylmaleimide.
A solution of poly(HPMA-co-MA-AH-MeO) (500 mg, 0.20 mmol methyl ester groups) and dithiothreitol (70 mg, 0.45 mmol) in 3.75 mL of dried distilled methanol was bubbled with argon for 5 minutes and subsequently kept under an argon atmosphere. 3.75 mL of hydrazine hydrate (77 mmol) was added to the reaction mixture. The reaction was carried out for 5 minutes and then the hydrazine hydrate together with the solvent were removed on a rotary evaporator under an oil pump vacuum (1 mbar, 1.5 h). A solution of N-ethylmaleimide (168 mg, 1.35 mmol) in 10 mL of methanol was added to the residue and the reaction was allowed to proceed for 20 minutes. The product was isolated by precipitation into ethyl acetate (total 200 mL) and then filtered and dried as described above. The polymer was freed of low molecular weight impurities by precipitation from methanol into ethyl acetate. The yield was 470 mg (94 %), the content of hydrazide groups 5.1 mol %, molar mass Mw = 41,900 g/mol, dispersity index D = 1.19.
Example 3b: Synthesis of polymer precursor poly(HPMA-co-MA-AH-NHNH2) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous blocking of the end thiol group of the polymer carrier and introduction of fluorescein at the end of the polymer chain
Figure imgf000019_0001
Analogously to Example 3a, a hydrazide groups-containing copolymer was prepared by hydrazinolysis of the copolymer containing methyl ester groups poly(HPMA-co-MA-AH-OMe) while removing sulphur-containing end groups originating from the transfer agent at the ends of the polymer chains and blocking the resulting end thiol groups by N- (5 - fΊuoresceinyl) - maleimide. The hydrazide group content 5.2 mol %, amino group content 0.5 mol %, molar mass Mw = 42,800 g/mol, dispersity D = 1.20.
Example 3c: Synthesis of polymer precursor poly(HPMA-co-MA-AH-NHNH2) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous blocking of the end thiol group of the polymer carrier and introduction of an amino group at the end of the polymer chain
Figure imgf000019_0002
Analogously to Example 3a, a hydrazide groups-containing copolymer was prepared by hydrazinolysis of a copolymer containing methyl ester groups poly(HPMA-co-MA-AH-OMe) while removing sulphur-containing end groups originating from the transfer agent at the ends of the polymer chains and blocking the resulting end thiol groups by N-aminoethylmaleimide trifluoro acetate. The hydrazide group content 5.1 mol %, amino group content 0.4 mol %, molar mass Mw = 38,500 g/mol, dispersity D = 1.16. Example 3d: Synthesis of diblock polymer precursor poly(HPMA-co-MA-AH-NHNH2)-S- S-poly(HPMA-co-MA-AH-NHNH2) by hydrazinolysis of poly(HPMA-co-MA-AH-MeO) and simultaneous mutual reaction of end thiol groups of polymeric carriers
Figure imgf000020_0001
wherein
X 1S-CH2-CH2-CH2-CH2-CH2-; R1 is 2-cyano-2-propyl; x is an integer ranging from 25 to 700.
A solution of poly(HPMA-co-MA-AH-MeO) prepared in Example 2a (500 mg, 0.20 mmol of methyl ester groups) and dithiothreitol (70 mg, 0.45 mmol) in 3.75 mL of dried distilled methanol was bubbled with argon for 5 minutes and then kept under an argon atmosphere. 3.75 mL of hydrazine hydrate (77 mmol) was added to the reaction mixture. The reaction was allowed to proceed for 5 minutes and then precipitated into ethyl acetate to remove dithiothreitol. The precipitated polymer was dissolved in methanol and then the residual hydrazine hydrate together with the solvent was removed on a rotary evaporator under an oil pump vacuum (1 mbar, 1.5 h) to form a diblock copolymer. The product was isolated by precipitation into ethyl acetate (total 200 mL) and then filtered and dried as described above. The polymer was purified by precipitation from methanol into ethyl acetate. The yield was 470 mg (94 %), the content of hydrazide groups 5.1 mol %, molar mass Mw = 71,900 g/mol, dispersity D = 1.16.
Example 4: Synthesis of polymer conjugate poly(HPMA-co-MA-AH-NHNH2) with fluorescent label Cyanine 5.5 at the end of the polymer chain
Figure imgf000020_0002
The poly(HPMA-co-MA-AH-NHNH2) polymer with end amino groups prepared according to Example 3c was used to bind the fluorescent label Cyanine 5.5 NHS ester.
A solution of 100 mg of poly(HPMA-co-MA-AH-NHNH2) copolymer in 0.5 mL of dimethyl acetamide (final concentration 100 mg polymer/mL) was mixed with a solution of 1 mg of Cyanine 5.5 NHS ester in 0.5 mL of dimethyl acetamide with the addition of dimethyl isopropylamine (equimolar to Cyanine 5.5 NHS ester). After 2 h of reaction, the polymer product was isolated by gel filtration in methanol. The solvent was evaporated under reduced pressure on a vacuum evaporator and the product was dissolved in water and lyophilized. The content of total Cyanine 5.5 was determined spectrophotometrically.
Characterisation of the polymer conjugate with Cyanine 5.5: Total yield of the fluorescent label binding reaction: 80 mg (80 %), content of total Cyanine 5.5 0.3 mol %.
Example 5a: Preparation of polymer conjugate poly(HPMA-co-AH-NH-N=DOX)
Figure imgf000021_0001
Copolymers with doxorubicin (DOX) attached to a PHPMA carrier by a hydrolytically cleavable hydrazone bond were prepared by reacting copolymers containing hydrazide groups poly(HPMA-co-MA-AH-NHNH2) with doxorubicin hydrochloride (DOX.HC1) in methanol catalysed by acetic acid.
A solution of 1.53 g of poly(HPMA-co-MA-AH-NHNH2) copolymer, prepared according to Example 3a, in 9.2 mL of methanol (167 mg of polymer/ml) was placed in a thermostated cell in which 0.19 g of g DOX.HC1 (3.3 mmol) was put. The inhomogeneous suspension was stirred in the dark at 25 °C and after 1 minute 0.5 mL of acetic acid was added. The suspension slowly dissolved during the reaction, after 22 h of reaction the polymer product was isolated from the homogeneous solution by precipitation into 100 mL of ethyl acetate; the polymer drug precipitate was isolated by filtration on a S4 frit, washed with 50 mL of ethyl acetate and dried to constant weight.
Characterisation of the polymer-drug conjugate: Total yield of the drug binding reaction: 17.2 g (96 %), total DOX content 11.3 % by weight, free DOX content less than 1.5 % of the total DOX content.
Example 5b: Preparation of polymer conjugate poly(HPMA-co-AH-NH-N=DEX)
Figure imgf000022_0001
Copolymers with dexamethasone attached to a PHPMA carrier by a hydrolytically cleavable hydrazone bond were prepared by reacting hydrazide groups-containing copolymers poly(HPMA-co-MA-AH-NHNH2) with a dexamethasone derivative, dexamethasone oxo -propyl benzoate (DEX), in methanol catalysed by acetic acid.
A solution of 1 g of poly(HPMA-co-MA-AH-NHNH2) copolymer in 5 ml of methanol (final concentration 167 mg polymer/mL) was mixed with a solution of 60 mg DEX (0.1 mmol) in 1 mL of methanol. After 5 h of reaction, the polymer product was isolated by precipitation into
200 mL of ethyl acetate; the precipitate of polymer drug was isolated by filtration on a S4 frit, washed with 150 mL of ethyl acetate and dried to constant weight. The content of total DEX was determined by HPLC according to the procedure (Krakovicova, EL, T. Etrych, and K. Ulbrich, HPMA-based polymer conjugates with drug combination. European Journal of Pharmaceutical Sciences, 2009. 37(3-4): p. 405-412). Characterisation of the polymer-drug conjugate: Total yield of drug binding reaction: 980 mg (92 %), total DEX content 5.3 % by weight, free DEX content less than 1.3 % of total DEX content.
Conjugates of poly(HPMA-co-MA-AH-NHNH2) with other drugs or their derivatives: pirarubicin, epirubicin, oxo -derivatives of ritonavir, oxo-derivatives of docetaxel, paclitaxel and larotaxel were prepared analogously.
Example 6: Release of dexamethasone from the polymeric conjugate poly(HPMA-co-AH- NH-N=DEX)
Release of dexamethasone from the poly(HPMA-co-AH-NH-N=DEX) conjugate was performed by incubation in 0.1 M phosphate buffer containing 0.15 M NaCl at 37 °C. The pH of the buffer was adjusted to conditions in the endosomes of the cells, thus slightly acidic environment of pH 5.5.
An aliquot part of the incubation medium was taken at appropriate time intervals and the DEX content was determined after extraction into chloroform and evaporation of the solvent and transfer to the methanol solution by HPLC (Shimadzu 20VP) on a Chromolith C18 reverse phase column (Chromolith Performance RP-18e; 100 x 4.6 mm) at an eluent flow rate of 5 mL/min and using a gradient from 0 to 100 % of solution B over 7 min (solution A: 5 % acetonitrile, 94.9 % water, 0.1 % trifluoro acetic acid (TFA); solution B : 89.9 % acetonitrile; 10 % water; 0.1 % TFA). A PDA detector (Shimadzu, Japan) (l = 230 nm) was used for detection. The calibration curve was constructed using DEX.
The results of the measurement of the drug release from the conjugate are shown in Figure 1.
Example 7: Demonstration of cytostatic activity of polymeric conjugate poly(HPMA-co- AH-NH-N=DOX) in vitro
Cells of several stable tumour lines of various origin were used to demonstrate the cytostatic activity of a polymeric conjugate poly(HPMA-co-AH-NH-N=DOX) bearing doxorubicin from Example 5a. These were the mouse tumour lines (CT26 - colon carcinoma cell line, 4T1 - breast cancer cell line, both from the BALB/c mouse inbred strain, and EL4.IL-2 - T-cell lymphoma line from the C57BL/6 mouse inbred strain) and FaDu - a human squamous cell carcinoma of the head and neck. Cells were cultured in 96-well plates with various concentrations of poly (HPMA-co-AH-NH-N=DOX) for 72 h. Cell proliferation was then determined by a standard method of incorporation of 3H-thymidine, which was added for the last 6 h of cultivation. Subsequently, the cultures were processed using a Tomtec Mach III harvester, and after drying, the radioactivity of the obtained samples was measured by a MicroBeta Trilux beta-scintillation counter (Wallac) using a solid scintillator (Meltilex; Perkin Elmer). The test results are expressed as an IC50 value, equal to the concentration of poly(HPMA-co-AH-NH-N=DOX) required to induce just 50 % inhibition of the growth (proliferation) of the tumour cells in question (see Table 2). The cytostatic activity of poly(HPMA-co-AH-NH-N=DOX) from Example 5a was compared with the activity of poly(HPMA-co-AH-NH-N=DOX), prepared according to the procedure reported in the literature (Chytil P. et al ., Eur. J. Pharm. Sci., 2010, 41, 73-82), and with the free drug.
Table 2: The cytostatic efficiency of poly(HPMA-co-AH-NH-N=DOX) from Example 5a was compared with the activity of poly(HPMA-co-AH-NH-N=DOX), prepared according to the procedure reported in the literature (Chytil P. et al ., Eur. J. Pharm. Sci., 2010, 41, 73-82), and free doxorubicin in four selected tumour lines. The IC50 values are reported in ng doxorubicin/mL and were calculated as the average of several independent assays.
Figure imgf000024_0001
In all tested lines, sensitive to doxorubicin (FaDu) or slightly sensitive (CT26), it is clear that the cytostatic activity of both conjugates poly(HPMA-co-AH-NH-N=DOX) is expected to be lower than the activity of the free drug, however, the values for conjugates whose polymeric carriers are prepared by other methods do not differ significantly. These values show high cytostatic activity of poly(HPMA-co-AH-NH-N=DOX) from Example 5a against tumour lines of various origins in vitro.

Claims

C L A I M S
1. A method for preparation of a linear statistical copolymer of general formula (I),
Figure imgf000025_0001
containing at least 75 mol % of HPMA monomer units, and from 0.5 to 25 mol %, based on the total number of monomer units, of structural units of formula (II)
Figure imgf000025_0002
wherein X is selected from the group consisting of alkylene having 1 to 8 carbon atoms; phenylene; -(CH2)q-(C(O)-NH-(CH2)r)p-, wherein p = 1 to 5, and q and r are independently selected from 1, 2 and 3; wherein X may optionally be substituted with one or more natural amino acid side chains, wherein the side chains might be the same or different; x is an integer in the range of from 25 to 700;
Ri is a radical leaving group of the transfer agent used; preferably Ri is selected from the group comprising 2-cyano-2-propyl and 5-carboxy-2-cyano-2-pentyl; and R2 is a thioether derivative given by the structure of the double bond compound (C=C) used after the addition of the SH end groups of the polymer chain or by the interaction of the SH end groups of a linear statistical copolymer to form a disulphide-linked diblock polymer; preferably R2 is selected from the group comprising 2-(ethenylsulphonyl)ethyl, 1-ethyl-2,5- dioxopyrrolidin-3-yl, 1-(2-hydroxyethyl)-2,5-dioxopyrrolidin-3-yl, 1-(2-propynyl)-2,5- dioxopyrrolidin-3-yl, 1-(3-carboxy-l-propyl)-2,5-dioxopyrrolidin-3-yl, 1-(2-aminoethyl)-2,5- dioxopyrrolidine-3-yl, 1-(3-aminopropyl)-2,5-dioxopyrrolidin-3-yl; and
Figure imgf000026_0001
wherein the molar mass of the linear statistical copolymer is in the range of from 4,000 to 100,000 g/mole; characterized in that the method comprises the following steps: a) providing HPMA, and providing a monomer of general formula (III),
Figure imgf000026_0002
wherein X is as defined above, and Y is selected from the group consisting of hydroxyl, (C1-C6) alkoxy, benzoxy, 4-nitrophenoxy, 2,3,4,5,6-pentafluorophenoxy, succinimidyl, (C1-C6) alkylthio group and thiazolidine-2-thione group; preferably Y is selected from the group consisting of methoxy, ethoxy, tert-butoxy, tert- butylthio and thiazolidine-2-thione group; b) radical RAFT polymerisation of monomers from step a) resulting in formation of the linear statistical copolymer; c) introduction of hydrazide groups in place of the substituent Y, and simultaneous in situ modification of the end groups of the linear statistical copolymer to give the statistical copolymer of the general formula (I); d) optionally, binding a biologically active molecule to the R2 end group of the polymer chain.
2. The method according to claim 1, characterized in that the monomer of general formula (III) from step a) is provided by a reaction of a compound of formula Y-C(O)-X-NH2, wherein X and Y are as defined above, with methacryloyl chloride; or by an esterification, thioesterification, or imidation of a carboxyl group present in a compound of formula HO-C(O)- X-NH2, followed by a reaction of the resulting aminoacid ester, thioester, or imide with methacryloyl chloride, resulting in formation of the monomer of the general formula (III).
3. The method according to claim 1 or 2, characterized in that the step b) of polymerisation of monomers is the controlled radical RAFT polymerisation of HPMA with the monomer of general formula (III) in a molar ratio in the range of from 75:25 to 99.5:0.5, at the temperature in the range of from 10 to 100 °C, and in a solvent preferably selected from the group comprising dimethyl sulphoxide, dimethyl acetamide, dimethyl formamide, dioxane, tert- butyl alcohol, water, aqueous buffer or mixtures thereof; initiated by an initiator, preferably selected from the group comprising 2,2'-azobis(2- methylpropionitrile), 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis(4-methoxy-2,4- dimethylpentanenitrile) ; and in the presence of a transfer agent, preferably selected from the group comprising 2-cyano-2- propyl benzodithioate, 4-cyano-4-(thiobenzoylthio) pentanoic acid, 2-cyano-2-propyl dodecyl trithiocarbonate, 2-cyano-2-propyl ethyl trithiocarbonate, and 4-cyano-4- [(dodecyl sulphanyl thiocarbonyl)sulphanyl] pentanoic acid.
4. The method according to claim 3, characterized in that step b) is carried out at a molar ratio of initiator : transfer agent in the range of from 1:1 to 1:10 and/or step b) is carried out at a molar ratio of transfer agent : monomers in the range of from 1:50 to 1:1000.
5. The method according to any one of the preceding claims 1 to 4, characterized in that step c) of introduction of hydrazide groups while modifying the end groups of the polymeric carrier consists in converting the group Y to a hydrazide group by a reaction with a reducing agent and hydrazine, preferably the reducing agent is dithiothreitol, and in situ modification of sulphur-containing end groups of the polymeric carrier:
- by a reaction with a compound bearing a double bond (C=C), preferably selected from the group comprising N - substituted maleimide or S- substituted vinyl sulphone; more preferably selected from the group comprising divinyl sulphone, carboxy-PEG vinyl sulphone, A- ethylmaleimide, A- (2 - hydroxycthyl) maleimide, A-propargylmaleimide, 3-maleimidopropionic acid, azido-PEG-maleimide and A- ( 5 - fΊuoreseeinyl) - maleimide ;
- or the end thiol groups are converted to amines using A-aminoethylmaleimide trifluoroacetate, or A- (3 - aminopropyl) maleimide trifluoroacetate;
- or the reducing agent is removed from the reaction mixture followed by a spontaneous conjugation of the SH end groups of the linear statistical copolymer to form disulphide-linked diblock polymers; wherein the reaction takes place in an inert atmosphere at room temperature and in a solvent preferably selected from the group comprising methanol, ethanol, dimethyl sulphoxide, dimethyl acetamide and dimethyl formamide; resulting in the linear statistical copolymer of general formula (I) as defined in claim 1.
6. The method according to any one of the preceding claims 1 to 5, characterized in that step c) is followed by step d), in which R2 group of the compound of general formula (I), preferably selected from the group comprising 2-(ethenylsulphonyl)ethyl, l-ethyl-2,5-dioxopyrrolidin-3-yl, l-(2-hydroxyethyl)-2,5-dioxopyrrolidin-3-yl, l-(2-propynyl)-2,5-dioxopyrrolidin-3-yl, l-(3- carboxy-l-propyl)-2,5-dioxopyrrolidin-3-yl, l-(2-aminoethyl)-2,5-dioxopyrrolidine-3-yl, l-(3- aminopropyl)-2,5-dioxopyrrolidin-3-yl; reacts with a biologically active molecule, selected from the group comprising fluorescent labels, chelators for radionuclides, chelators for contrast agents for nuclear magnetic resonance, targeting groups, oligopeptides, oligosaccharides, peptides, scFc fragments, monoclonal antibodies and specific cell-surface receptor ligands, resulting in formation of a polymeric conjugate of this biologically active molecule with the linear statistical polymer.
7. The method according to claims 6, characterized in that the biologically active molecule is selected from the group comprising fluorescent labels, preferably fluorescein, Cyanine 5.5, Cyanine 7, Cyanine 7.5, Dyomics-676, Dyomics-676, Alexa fluor-488; chelators for radionuclides, preferably deferoxamine, DOTA, NOTA, tyrosinamide; targeting groups for targeted biodistribution, preferably targeting oligopeptides, especially selected from the group comprising GE-7, GE-11, RGD; scFc fragments; and monoclonal antibodies, preferably anti- CD20, anti-CD38, anti-CD19, anti-Her2Neu, anti-GD2.
8. A method for preparation of a conjugate of the linear statistical copolymer of general formula (I) with a drug by means of a pH-sensitive hydrolysable hydrazone bond, characterized in that it comprises the following steps: a) preparing the linear statistical copolymer of general formula (I) according to any one of the preceding claims 1 to 7 ; b) binding of a drug to the structural unit of general formula (II) of the linear statistical copolymer, as defined in claim 1, by a hydrazone bond, resulting in formation of a conjugate of the linear statistical copolymer of formula (I) with the drug.
9. The method according to claim 8, characterized in that binding of a drug in step b) comprises reacting the linear statistical copolymer of general formula (I) with a drug, or with a derivative thereof containing a keto group, catalysed with acetic acid, resulting in the formation of a hydrazone bond between -C(=0)- group of the drug, and the -NH-Nth group of the side chain of the linear statistical copolymer of general formula (I); preferably, the drug is selected from the group comprising anti-tumour drugs, anti-inflammatory drugs or immunomodulators, more preferably, the drug is selected from the group comprising anthracycline, doxorubicin, pirarubicin, epirubicin, taxol, paclitaxel, docetaxel, larotaxel, mitomycin C, dexamethasone, ritonavir, or oxo -derivatives thereof; most preferably, the drug is selected from the group comprising doxorubicin, dexamethasone, pirarubicin, epirubicin, ritonavir, docetaxel, paclitaxel, larotaxel, or oxo-derivatives thereof; wherein the reaction is carried out in a solvent selected from non-aqueous alcohols containing 1 to 5 carbons or polar aprotic solvents, preferably the solvent is methanol, ethanol, dimethyl formamide, dimethyl acetamide or dimethyl sulphoxide.
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