The invention relates to a block copolymer for overcoming drug resistance of tumours to chemotherapy, its polymer-drug conjugate, pharmaceutical compositions containing them, methods for their preparation and their use as micellar drug carriers allowing overcoming multiple drug resistance of tumours.

Background Art

Currently, in the treatment of many diseases, especially cancer, there are efforts to utilize more fully the polymer-based substances which may serve as the so-called polymer drug carriers. The condition of their use for medical purposes is their biocompatibility, ability to reduce non-specific toxicity of a bound drug compared to a low molecular weight drug, prolonged circulation of the drug in the bloodstream, the possibility of elimination of the polymer carrier from the body (preferably by glomerular filtration) after delivery the drug to its targetand, finally, drug accumulation in the target tissue and its controlled release from the polymer carrier. It has been previously found that the high molecular weight of polymer carriers and their conjugates with drugs significantly influences and contributes to the so-called passive drug accumulation in solid tumours. This phenomenon is called the enhanced permeability and retention (EPR) effect. On the basis thereof, in solid tumours there are preferentially accumulated high molecular weight substances both water-soluble and those forming particles in water with sizes of several tens to hundreds of nanometres. This fact is now extensively used for the preparation of polymer conjugates with a covalently bound cancerostatic, specifically accumulating in the majority of solid tumours. A low molecular weight cancerostatic agent is bound to the polymer carrier via a degradable bond allowing controlled release of the delivered drug from the carrier in its original active form either in the tumour tissue, or directly in the tumour cell. Recent years have seen a sharp increase in the research and development of polymer drug carriers based on copolymers of N-(2-hydroxypropyl)methacrylamide (pHPMA), which are water-soluble, non-toxic to living organisms, entirely biocompatible with living tissues and also allow binding of e.g. drug, ABC transporters inhibitor, structures enabling targeting towards cell receptors, and other biologically active molecules.

PHPMAs allow modification of the main chain by another polymer chain, both at chain ends and along the chain by the so called grafting. Other types of polymers studied and utilized in clinical practice as various types and forms of polymer drug carriers are e.g. various derivatives of poly(ethylene oxide), copolymers of poly(ethylene oxide) and poly(propylene oxide) (Pluronic or Poloxamer), poly(N-vinylpyrrolidone), copolymers of lactic and glycolic acids, derivatives of polyphosphazenes, polyanhydrides, poly(s- caprolactone), polyphosphoesters, poly(cyanoacrylate), poly(methyl acrylate)s and poly(methacrylic acid), poly(N-isopropylacrylamide) and others. Binding a low molecular weight cancerostatic drug to polymer carrier via a covalent bond utilizes biodegradable linkages, e.g. amide, hydrazone, acetal, disulphide (-S-S-) and the like. These linkages are usually stable in the bloodstream and are cleaved specifically in the environment of the tumour or tumour cells. Therefore, there is no risk that the low molecular weight cancerostatic releases non-specifically already during circulation in the bloodstream, where it would act toxically and moreover, it would be eliminated from the organism in a very short time without reaching the desired target (e.g. a tumour).

Delivery of a cancerostatic agent to the place of desired effect is one, but not the only prerequisite for successful treatment of cancer. Repeated cytostatic treatment often reduces its effectiveness due to resistance of tumour cells to structurally and functionally different cytotoxic drugs, in particular anthracycline antibiotics, including e.g. doxorubicin (DOX). The resistance of tumour cells to drugs (the multidrug resistance, MDR) is usually caused by prolonged exposure of these cells to cytotoxic agents and so their defensive reaction is to reduce the intracellular concentration of the drug by various mechanisms. One of the most significant and therefore also frequently studied mechanisms is the drug efflux which involves using special transmembrane proteins to "pump" cytostatic agents out of the cell before they can act inside the cell. In most cases, this phenomenon is caused by a high molecular weight membrane glycoprotein called P-glycoprotein (P-gp). P-gp belongs to the superfamily of ABC transporters, which are characterized by two ATP domains where ATP hydrolysis takes place with release of energy required to transport the substrate out of the cell. P-gp is an ATP-dependent efflux pump for endogenous or exogenous substances with a broad substrate specificity which clearly distinguishes it from other ABC transporters whose substrates are narrow groups of substances. P-glycoprotein is a part of the plasma membrane of cells and is located in the cells of many important organs such as the liver, kidney, intestines, and others where it participates in the active transport of ions, amino acids, peptides, sugars, but also drugs and their metabolites from inside the cells to extracellular environment. While in healthy cells P-gp acts as a protection against penetration of xenobiotics in the body, in the case of tumour cells wherein the protein is expressed in much larger quantities it contributes thanks to this property to the resistance of cancer cells to the effects of drugs. Through inhibition of this process it is possible to achieve better penetration of drugs into cells and maintain here a sufficiently high level of the drug required for effective therapy. One of the possible solutions how to achieve inhibition of the P-gp function, and thereby permit the entry of the drug into cell and its activity inside, is a structural modification of drugs or use of special P-gp inhibitors in combination with a therapeutic agent. Using the inhibitor alone, however, has very serious side effects. Moreover, the threat of inhibition of the P-gp function in normal, thus healthy cells is very real. At present, scientists are trying to address the issue of side effects of P-gp inhibitors (e.g. ritonavir- or reversin-based) by their binding to a macromolecular carrier to which also a cytostatic agent is bound, or by combining a polymer inhibitor with a polymer cancerostatic.

Another alternative is the use of a polymer-drug conjugate in which part of the polymer carrier also acts as a P-gp inhibitor. From literature there are known studies of Pluronic- based micellar carriers, triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), PEO-PPO-PEO, which has been found to be capable to inihibit P-gp. Micellar systems based on Pluronic can be used as solubilizers of water- insoluble drugs (such as DOX) and as "nanocontainers" for these drugs which are to be released only at the specific site of action (e.g. in a solid tumour). Polymer micelles, polymersomes or other forms of nanoparticles such as dendrimer-based nanosystems are a type of polymer carrier, which should be able (due to the EPR effect) to passively target the whole system to vascularized solid tumours, where the increased accumulation of a high molecular medicine should occur. Micelles consist of a hydrophobic core in which a low molecular drug is incorporated either by physical interactions or covalently and a hydrophilic shell which is mostly composed of hydrophilic polymers (usually based on PEO) protecting the entire system from aggregation and from interacting with the components of live organism (macrophages and cells of the immune system, RES cells) and trapping in the liver. Systems based on high-molecular weight substances, whether in the form of water-soluble carriers, micelles, liposomes, polymersomes or other nanosystems, promise more efficient and safer use of cancerostatics compared to the current classical chemotherapy.

Drugs which bypass the multiple drug resistance by inhibiting the function of P- glycoprotein (P-gp) by PEO and PPO block copolymers (US 20130195964 (Al); Batrakova, E.V.; Kabanov, A.V., J. Control. Release 2008; 130: 988-106; Chen, L.; Sha, X.; Jiang, X.; Chen, Y.; Ren, Q.; Fang, X., Int. J. Nanomedicine 2013; 8: 73-84; Alakhova, D.Y.; Rapoport, N.Y.; Batrakova, E.V.; Timoshin, A.A.; Li, S.; Nicholls, D.; Alakhov, V.Y., Kabanov, A.V.; J. Control. Release 2010; 142(1): 89-100; Alakhova, D.Y.; Zhao, Y.; Li, S.; Kabanov, A.V., PLOS ONE, 2013; 8(8): e72238) and which also use these amphiphilic copolymers as micellar drug carriers, have a hydrophobic drug trapped within the hydrophobic core of the micelle only by hydrophobic interactions, and it is released by a combination of diffusion and disintegration of micelle when the concentration of the copolymer in body fluids is decreased below the critical micelle concentration (CMC). The disadvantage of systems with non-covalently incorporated drugs is the permanent release of the drug due to diffusion, even in healthy parts of the organism, during transport of the system to the target tissue.

Disclosure of the Invention

The present invention relates to a block copolymer, its biodegradable conjugate with a low molecular weight drug, and compositions for the treatment especially of cancer. The resulting polymer cancerostatics enable a targeted therapy particularly of poorly treatable resistant tumour diseases in human medicine. These polymer cancerostatics allow for a targeted effect of cancerostatics, in particular doxorubicin, on solid tumours while overcoming multiple drug resistance (MDR) of tumours to chemotherapy. The invention relates to an amphiphilic block copolymer, or its conjugate with a drug, which in an aqueous medium forms polymer micelles whose size and structure are controlled by the hydrophilicity and hydrophobicity of each block of the block copolymer, their length and the ratio of the hydrophilic and hydrophobic parts of the molecule. Polymer micelles, which are also an object of the present invention, comprise a hydrophilic shell consisting of a hydrophilic polymer based on N-(2-hydroxypropyl)methacrylamide (HPMA) and a hydrophobic core formed by a polymer based on poly(propylene oxide) (PPO). Both polymers are bound to one another via a biodegradable spacer that permits disintegration of the block copolymer into individual blocks upon reaching the conditions of biodegradation. A relevant drug is bound to the polymer by a pH-sensitive covalent bond which prevents accidental release of the drug in body fluids through diffusion or disintegration of micelles when the concentration of the copolymer is reduced below the critical micelle concentration (CMC), and the drug is thus released from the block copolymer only after pH of the surrounding tissue has changed, which is typically in the target tumour tissue. Moreover, the block copolymer of the present invention itself acts as an inhibitor of P-glycoprotein, and therefore it can be used also separately (without a conjugated drug) in combination with low molecular weight drugs to overcome multiple drug resistance of tumours to chemotherapy. Due to biodegradation of the block polymer system in the target tumour cells, PPO is released which is in itself a highly active inhibitor of P-glycoprotein. By degradation of the polymer system its ability to inhibit MDR is therefore significantly potentiated, whereas any transport of PPO other than within the conjugated amphiphilic polymer is not possible. PPO itself forms a micro-emulsion in aqueous solutions that is unusable for medical use in vivo. Moreover, if this polymer system comprises a conjugated drug, also the drug is released only after pH has changed, i.e. in the target tumour tissue. Therefore, the drug is transported by controlled delivery to the tumour tissue, where it is released and in addition, the potential resistance of the tumour tissue to this drug is inhibited by the block copolymer itself or PPO released therefrom. The whole system of the present invention thus allows for a significant reduction of MDR and controlled delivery of the drug to the tissue, thus reducing the effective doses of drug administered to the subject being treated. The subject of the present invention is a block copolymer for overcoming drug resistance of tumours to chemotherapy, comprising at least one block A and at least one block B, wherein at least one block A and at least one block B are connected to each other with a linker L, which is hydrolytically, enzymatically and/or reductively biodegradable, and wherein the hydrophilic block A is formed by poly(N-(2-hydroxypropyl) methacrylamide), eventually containing up to 20 mol% of monomer units of general formula (I),

where R is aminoacyl selected from the group consisting of glycyl, glycylglycyl, β-alanyl, 6-aminohexanoyl, 4-aminobenzoyl, acyles derived from oligopeptides of two to five amino acids, especially GlyPheGly, GlyLeuGly, GlyLeuPheGly and GlyPheLeuGly;

and/or up to 15 mol% of monomer units of general formula (II),

(Π),

where T is oligopeptide attached to the monomer unit through an amide bond, wherein the oligopeptide is selected from the group consisting of the oligopeptides of two to five amino acids, preferably the oligopeptide is GlyPheGly, GlyLeuGly, GlyLeuPheGly, GlyPheLeuGly, AspProLys, AspProSer, and AspProGly; the block A may optionally contain terminal groups defined below;

and the hydrophobic block B is formed by a polypropylene oxide; the block B may optionally contain terminal groups as defined below;

wherein the block A has its molecular weight M„ in the range of from 4,000 to 60,000 g/mol (corresponding to 25 to 400 monomer units), preferably M _n is in the range of from 5,500 to 40,000 g/mol (37 to 260 monomer units), and the block B has its molecular weight M„ in the range of from 1,000 to 17,600 g/mol (23 to 400 monomer units), preferably a molecular weight from 1,500 to 12,000 g/mol (34 to 270 monomer units); and wherein the molecular weight of the block copolymer is in the range of from 5,000 to 95,000 g/mol.

The block copolymer for overcoming drug resistance of tumours to chemotherapy may

further comprise terminal groups, wherein the terminal group of block A is and the terminal group of block B is selected from the group consisting of - H ₂ , dibenzocyclooctyle (-DBCO), 2-aminopropyl, and an oligopeptide of two to five amino acids connected to PPO through an amide bond, preferably the oligopeptide is GlyPheGly, GlyLeuGly, GlyLeuPheGly, GlyPheLeuGly, AspProLys, AspProSer, and AspProGly.

In one embodiment, blocks A and B are arranged in a linear or branched topology; preferably blocks A and B are arranged in the order of A-L-B or A-L-B-L-A or B-L-A-L- B, or according to general formula (III)

In another embodiment, the linker L is selected from the group comprising oligopeptides with two to five amino acids and/or a disulfide bond, preferably the linker L is oligopeptide AspProLys, AspProLysProAsp, GlyLeuGly, GlyPheGly, GlyPheLeuGly, GlyLeuPheGly or a disulfide bond. The biodegradable linker L may be attached to blocks A and B by an amide bond or as a part of the linking chain of general formula (IV)

(V),

general formula (VI)

(VI),

general formula (VII)

(VII),

wherein L is oligopeptide of two to five amino acids and/or a disulfide bond, A represents the hydrophilic block A, and B represents the hydrophobic block B.

The subject of the present invention is also a polymer conjugate, which comprises the block copolymer according to the invention, and which further contains from 1 to 25 wt% of a low molecular weight drug covalently bound to the monomer unit of the general formula (I) and/or to the monomer unit of the general formula (II) of the block A by a hydrolytically and/or enzymatically degradable covalent bond, preferably by a hydrolytically degradable pH-sensitive bond, preferably the drug is a low molecular weight cytostatic, most preferably the low molecular weight cytostatic is selected from the group comprising doxorubicin, docetaxel, paclitaxel, pirarubicin, mitomycin C, daunorubicin, larotaxel. The low molecular weight drug means a drug that has a molecular weight ranging from 200 to 1,000 g/mol.

In one embodiment, the molecule of the low molecular weight drug is bound to the monomer unit of the general formula (I) and/or to the monomer unit of the general formula (II) of the block A of a polymer conjugate by a hydrazone or a peptide bond.

In one embodiment, the block copolymer according to the present invention and/or the polymer conjugate according to the present invention, are in an aqueous medium in the form of a micelle. The aqueous medium comprises water, saline, body fluids, particularly blood and blood plasma. The size and structure of the micelles depends on the hydrophilicity and hydrophobicity of blocks A and B and on their length. The hydrophilic coating layer of the micelle is formed by the block A, eventually with a bound drug, and the hydrophobic core is formed by the block B.

The subject of the present invention is also a method of preparation of the block copolymer according to the present invention, the said method comprising the following steps:

- a step of radical polymerization of N-(2-hydroxypropyl)methacrylamide, eventually containing up to 20 mol% of the monomer of the general formula (I), where R is aminoacyl selected from the group consisting of glycyl, glycylglycyl, β-alanyl, 6-aminohexanoyl, 4-aminobenzoyl, acyles derived from oligopeptides of two to five amino acids, particularly GlyPheGly, GlyLeuGly, GlyLeuPheGly and GlyPheLeuGly, protected on hydrazide groups by tert- butyloxycarbonyl (Boc) groups, and/or optionally containing up to 15 mol% of the monomer of the general formula (II), where T is oligopeptide attached to the monomer unit by an amide bond, wherein the oligopeptide is selected from the group consisting of oligopeptides of two to five amino acids, preferably the oligopeptide is GlyPheGly, GlyLeuGly, GlyLeuPheGly, GlyPheLeuGly, AspProLys , AspProSer and AspProGly;

at a temperature ranging from 40 to 100°C, preferably from 50 to 80°C, and in a solvent preferably selected from the group comprising of DMSO, aqueous buffers, dimethylacetamide, dimethylformamide, methanol, ethanol, dioxane, tetrahydrofuran, propanol, tert-butanol or mixtures thereof, initiated with an initiator, preferably selected from the group comprising ABIK-TT and ABIK- N ₃ , where ABIK-TT is 2-[(Z)-[l-cyano-l-methyl-4-oxo-4-(2-thioxothiazolidin- 3-yl)butyl]azo]-2-methyl-5-oxo-5-(2-thioxothiazolidin-3-yl)p entanenitrile and ABIK-N ₃ is N-(3 -azidopropyl)-4- [(Z)- [4-(3 -azidopropylamino)- 1 -cy ano- 1 - methyl-4-oxo-butyl]azo]-4-cyano-pentanamide, optionally in the presence of a chain transfer agent, preferably selected from the group of CTA-TT and CTA- N ₃ , where CTA-TT is [l-cyano-l-methyl-4-oxo-4-(2-thioxothiazolidin-3- yl)butyl]benzencarbodithioate and CTA-N ₃ is [4-(3 -azidopropylamino)- 1- cyano-l-methyl-4-oxo-butyl]benzencarbodithioate, to form the hydrophilic block A as a semitelechelic hydrophilic polymer block A, preferably with a terminal TT or N ₃ group; wherein the terminal TT or N ₃ group of the resulting semitelechelic hydrophilic polymer block A may further react with aminoethylpyridyldisulfide to give semitelechelic hydrophilic polymer block A with a terminal aminoethylpyridyldisulfide (PDS) group, or with a peptide of two to five amino acids to give a semitelechelic hydrophilic polymer block A with a terminal peptide chain, as a precursor of the linker L;

- a step in which the semitelechelic hydrophilic polymer block A from the previous step reacts with the semitelechelic or telechelic hydrophobic polymer block B of general formulas Y-PPO-Y, Y-L-PPO-L-Y or PPO-L-Y or

¥

I

L

I

Y

ΡΡΌ PPG. ^{1 l} ,

Y Y ¥ ^¥

or

wherein Y is - H ₂ , oligopeptide of two to five amino acids, succinimidyl carbonate or dibenzocyclooctyne group, and wherein L is oligopeptide of two to five amino acids or an -S-S- bond, and wherein L may be attached to the block B and group Y by an amide bond or as a part of the linking chain of general formula (VIII) CH3 NH

(VIII),

general formula (IX)

(ix),

general formula (X)

(X),

general formula (XI)

(xi),

or with the chain transfer agent PPO-(L-CTA) ₂ , where L is peptide of two to five amino acids or -S-S- bond,

to give an amphiphilic block copolymer according to the invention, which may be optionally further subjected to purification by column chromatography and/or removal of protecting Boc groups, by e.g. trifluoroacetic acid, and/or lyophilization. Lyophilization of the resulting product allows the amphiphilic copolymer to be stored without the risk of its decomposition, and allowing immediate formation of micelles after its dissolution. Types of reactions that are preferably used for preparing the amphiphilic block copolymer according to the present invention are polycondensation (e.g. using the commercial NH ₂ - PPO- H ₂ or PPO-(oligopeptide) ₂ ), "click" reaction (e.g. using terminal groups of dibenzylcyclooctyne, propargyl and azide, respectively, at semitelechelic blocks A and B respectively), and RAFT polymerization (using the pre- prepared chain transfer agent, e.g. PPO-(CTA) ₂ ). While H ₂ -PPO- H ₂ is commercially available, other derivatives of the general formula Y-PPO-Y may be prepared by activation of the terminal OH groups of the commercially available PPO, which is carried out by reaction with phosgene, N- hydroxysuccinimide and N,N-diisopropylethylamine, thereby converting the terminal groups to succinimidyl carbonate groups which optionally may be further converted to dibenzocyclooctyne or propargyl groups by reaction with DBCO-amine or propargyl amine and N,N-diisopropylethylamine, or which may be modified by trifiuoroacetate of oligopeptide, preferably of two to five amino acids, and N,N-diisopropylethylamine.

The subject of the present invention is also a method for preparing a polymer conjugate according to the invention, which comprises the following steps:

- a step of radical polymerization of N-(2-hydroxypropyl)methacrylamide, optionally containing up to 20 mol% of the monomer of the general formula (I), where R is aminoacyl selected from the group consisting of glycyl, glycylglycyl, β-alanyl, 6-aminohexanoyl, 4-aminobenzoyl, acyles derived from the oligopeptides of two to five amino acids, especially GlyPheGly, GlyLeuGly, GlyLeuPheGly and GlyPheLeuGly, protected on hydrazide groups by tert-butyloxycarbonyl (Boc) groups, and/or optionally containing up to 15 mol% of the monomer of the general formula (II), where T is oligopeptide attached to the monomer unit through an amide bond, wherein the oligopeptide is selected from the group consisting of the oligopeptides of two to five amino acids, preferably oligopeptide is GlyPheGly, GlyLeuGly, GlyLeuPheGly, GlyPheLeuGly, AspProLys , AspProSer and AspProGly; wherein the monomer of the general formula (I) and/or the monomer of the general formula (II) may eventually contain a covalently bound molecule of a low molecular weight drug, preferably selected from the group comprising doxorubicin, docetaxel, paclitaxel, pirarubicin, mitomycin C, daunorubicin, larotaxel; the eventual molecule of a low molecular weight drug is bound by a biodegradable (enzymatically or hydrolytically cleavable) bond;

at a temperature ranging from 40 to 100°C, preferably from 50 to 80°C, and a solvent preferably selected from the group comprising of DMSO, aqueous buffers, dimethylacetamide, dimethylformamide, methanol, ethanol, dioxane, tetrahydrofuran, propanol, tert-butanol or mixtures thereof, initiated with an initiator, preferably selected from the group consisting of ABIK-TT and ABIK- N ₃ , where ABIK-TT is 2-[(Z)-[l-cyano-l-methyl-4-oxo-4-(2-thioxothiazolidin- 3-yl)butyl]azo] -2-methyl-5-oxo-5-(2-thioxothiazolidin-3-yl)pentanenitrile and ABIK-N ₃ is N-(3 -azidopropyl)-4- [(Z)- [4-(3 -azidopropylamino)- 1 -cy ano- 1 - methyl-4-oxo-butyl]azo]-4-cyano-pentanamide, optionally in the presence of a chain transfer agent, preferably selected from the group of CTA-TT and CTA- N ₃ , where CTA-TT is [l-cyano-l-methyl-4-oxo-4-(2-thioxothiazolidin-3- yl)butyl]benzencarbodithioate and CTA-N ₃ is [4-(3 -azidopropylamino)- 1- cyano-l-methyl-4-oxo-butyl]benzencarbodithioate, to form the hydrophilic block A, preferably with a terminal TT or N ₃ group; optionally containing a covalently bound low molecular weight drug, as a semitelechelic hydrophilic polymer block A, optionally containing a covalently bound low molecular weight drug; wherein the terminal TT or N ₃ group of the resulting semitelechelic hydrophilic polymer block A may further react with aminoethylpyridyldisulphide to give a semitelechelic hydrophilic polymer block A with terminal aminoethylpyridyldisulphide (PDS) group, or with a peptide to form a semitelechelic hydrophilic polymer block A with a terminal peptide chain or PDS group as a precursor of the linker L;

- a step in which the semitelechelic hydrophilic polymer block A from the previous step, eventually containing the covalently bound low molecular weight drug, reacts with the semitelechelic or telechelic hydrophobic polymer block B of general formula Y-PPO-Y, Y-L-PPO-L-Y or PPO-L-Y or

Y

L

Y

or where Y is - H ₂ , oligopeptide of two to five amino acids, succinimidyl carbonate or dibenzocyclooctyne group, and where L is peptide with two to five amino acids or -S-S- bond, wherein L may be attached to the block B and group Y by an amide bond or as a part of the linking chain of formulas (VIII), (IX), (X), (XI),

or with the chain transfer agent PPO-(L-CTA) ₂ , where L is peptide of two to five amino acids or -S-S- bond,

to give an amphiphilic block copolymer of the invention or, optionally, if the hydrophilic block A from the previous step already contains a covalently bound drug, to give a polymer conjugate of the invention. While H ₂ -PPO- H ₂ is commercially available, other derivatives of formulas Y-PPO-Y, Y-L- PPO-L-Y, PPO-L-Y and trimers can be prepared by activation of the terminal OH groups of the commercially available PPO (HO-PPO-OH or poly(propylene oxide)triol PPO (OH) ₃ ), which is carried out by reaction with phosgene, N-hydroxysuccinimide and N,N-diisopropylethylamine, thereby converting the terminal groups to succinimidyl carbonate groups which optionally may be further converted to dibenzocyclooctyne groups by reacting with DBCO-amine and N,N-diisopropylethylamine, or which may be modified by trifluoroacetate of oligopeptide, preferably of two to five amino acids, and N,N-diisopropylethylamine;

- optionally a step of removal of protecting Boc groups, when the resulting amphiphilic block copolymer or polymer conjugate from the previous step reacts e.g., with trifluoroacetic acid;

- optionally a step of conjugation of free hydrazide groups and/or amide groups of monomer units of the general formula (I) or (II) of the amphiphilic block copolymer, resulting from one of the previous two steps, with a low molecular weight drug in its free form or in a form of its salt with an acid, e.g. HC1, or of a derivative thereof, e.g. with levulinic acid; wherein the low molecular weight drug is a drug which has a molecular weight ranging from 200 to 1,000 g/mol, preferably the low molecular weight drug is doxorubicin, docetaxel, paclitaxel, pirarubicin, mitomycin C, daunorubicin, larotaxel;

- optionally a step of purification by column chromatography and/or lyophilization of the resulting product from the previous step. The subject of the present invention is also a pharmaceutical composition comprising: the block copolymer according to the invention and the low molecular weight drug in its free form (meaning a drug non-covalently bound to the block copolymer of the invention) that has a molecular weight ranging from 200 to 1,000 g/mol, preferably the drug is a low molecular weight cytostatic, most preferably a low molecular weight cytostatic selected from the group comprising doxorubicin, docetaxel, paclitaxel, pirarubicin, mitomycin C, daunorubicin, larotaxel, in its free form; and/or the polymer conjugate according to the invention;

wherein the pharmaceutical composition further comprises at least one pharmaceutically acceptable ingredient selected from the group comprising antiadhesives, binders, coating agents, colouring agents, disintegrants, flavourings, lubricants, preservatives, sweeteners, absorbents. Preferably, the block copolymer and/or the polymer conjugate in the pharmaceutical composition are present in a lyophilized form which enables its rapid reconstitution into micellar form after dissolution in an aqueous medium.

The subject of the present invention is also the block copolymer according to the invention and/or the polymer conjugate according to the invention and/or the pharmaceutical composition according to the invention for use as a medicament.

The subject of the present invention is also the block copolymer according to the invention and/or the polymer conjugate according to the invention and/or the pharmaceutical composition according to the invention for use as a cytostatic. The subject of the present invention is also the block copolymer according to the invention and/or the polymer conjugate according to the invention and/or the pharmaceutical composition according to the invention for use as a medicament in the treatment of solid tumours and/or lymphoma and/or leukaemia. The presence of hydrolytically and/or enzymatically and/or reductively biodegradable linker L between the blocks A and B highly significantly and unexpectedly increases the inhibiting activity of P-gp of the resulting amphiphilic block copolymer and hence its cytostatic effectiveness as compared with systems in which there is only a non-degradable covalent bond between the hydrophobic block B and hydrophilic block A. As is apparent from Examples 35 to 38 of the invention (see below), by replacing a covalent bond between blocks A and B with a biodegradable oligopeptide or -S-S- bond, the resulting inhibiting ability of the polymer towards P-gp on the multiresistant tumour lines increases twice, which significantly increases also the cytotoxicity of the degradable polymer conjugate itself against resistant tumour cells. The biodegradable amphiphilic block copolymer, when added to a free drug or other polymer pro-drug, will increase cytotoxicity significantly more than a non-degradable amphiphilic block copolymer. Due to degradation of the polymer system according to the invention in the target tumour cells, PPO itself is released, which is in itself a highly active inhibitor of P-glycoprotein, better than the amphiphilic block copolymer, in which the hydrophilic part prevents PPO from being fully effective. It must be emphasized that the delivery of PPO to the target tissues other than within a conjugated amphiphilic polymer is not possible, since PPO itself forms in aqueous solutions a micro-emulsion unusable for medical use in vivo. Within a degradable block copolymer, hence the conjugate, unique properties of the carrier system, namely the ability to targetedly accumulate in tumour tissue and deliver and release a drug in this tissue, combine with a unique ability to inhibit multiple drug resistance by highly active parts of the system after its degradation. The inhibition of MDR unexpectedly and significantly increases by degradation of the polymer system according the present invention in the target tissue (i.e. biodegradation of the linker L).

Brief Description of Figures

Figure 1 : Example of a particle size distribution curve depending on the intensity of scattered light.

Figure 2: Release of the drug doxorubicin from the diblock polymer conjugate with doxorubicin as prepared in Example 28A at 37°C in buffers of pH 5.0 and 7.4.

Figure 3 : Dependence of the rate of release of docetaxel derivative (DTX-LEV) from the solution of micellar polymer conjugate with the bound DTX-LEV of Example 28B using a pH-labile hydrazone bond in phosphate buffers of pH 5.0 and pH 7.4 at 37 °C.

Figure 4: Calcein assay in B3/DOX cell line: The degree of inhibition of P-gp mediated efflux by various concentrations of diblock degradable polymer PUPMA-L-PPO, where L is disulphide linker, with regard to non-degradable PUPMA-PPO (Example 20) after 2 and 6 hours incubation. Expressed as a percentage of calcein MFI related to the control, control 10 μΜ CsA (cyclosporine A).

Figure 5: Calcein assay in B4/DOX cell line: The degree of inhibition of P-gp mediated efflux by various concentrations of diblock degradable polymer PFIPMA-L-PPO, where L is disulphide linker, with regard to non-degradable PFIPMA-PPO (Example 20) after 2 and 6 hours of incubation. Expressed as a percentage of calcein MFI related to the control, control 10 μΜ CsA (cyclosporine A).

Figure 6: Calcein assay in P388/MDR cell line: The degree of inhibition of P-gp mediated efflux by various concentrations of diblock degradable polymer PUPMA-L-PPO, where L is AspProLys linker, with regard to non-degradable PHPMA-PPO (Example 20) after 6 h incubation. Expressed as a percentage of calcein MFI related to the control, control 10 μΜ CsA (cyclosporine A).

Figure 7: Average tumour growth (a) and survival (b) in C57BL/6 mice with EL4 lymphoma after treatment with micellar diblock conjugate of Example 28 (DB-DOX) or linear conjugate with doxorubicin (PUPMA-DOX) or free doxorubicin (as described in Table 7). The tumour size is recorded as volume V=a*b ² /2, where "a" is the longer diameter of the tumour and "b" is the shorter one.

Figure 8: Time dependence of DOX amount accumulated in solid tumours of EL4 T cell lymphoma in mice after administration of the diblock polymer conjugate with DOX of Example 28 (DB-DOX). As a control group was used the linear PHPMA-based conjugate with DOX (PHPMA-DOX) and the free drug (DOX), dosage 10 mg Dox/kg, free drug 2 x 5 mg DOX/kg.

Figure 9: Time dependence of DOX amount circulating in the bloodstream of mice inoculated with EL4 T-cell lymphoma after administration of the diblock polymer conjugate with DOX of Example 28 (DB-DOX). As a control group was used the linear PHPMA based conjugate with DOX (PHPMA-DOX) and the free drug (DOX), dosage 10 mg Dox/kg, free drug 2 x 5 mg Dox/kg.

Figure 10: Scheme of a micelle formed by the A-L-B type amphiphilic diblock copolymer with a covalently bound drug doxorubicin (DOX).

Figure 11 : Scheme of a micelle formed by the A-L-B-L-A type amphiphilic triblock copolymer with a covalently bound drug doxorubicin (DOX).

Examples Example 1 : Synthesis of the chain transfer agent PP0-(GFLG-CTA)2 for RAFT pol merization

PPO-(GFLG-CTA) ₂

The commercially available poly(propylene oxide)-bis-2-aminopropylether was first modified at both terminal amino groups by tetrapeptide GFLG prepared by solid-phase peptide synthesis. NH ₂ -PPO- H ₂ (M ~ 4,000 g/mol; 8.60 mg, 4.30 x 10 ^"3 mmol -NH ₂ ) was dissolved in DMF and the solution was added to excess of GFLG (7.29 mg; 17 x 10 ^"3 mmol) and solid N-hydroxysuccinimide (NHS, 1.96 mg; 17 x 10 ^"3 mmol). The reaction mixture was cooled using an ice water bath. The excess of N,A^-diisopropylcarbodiimide (DIC) was added to the reaction mixture and the reaction mixture was reacted under stirring overnight. The product PPO(GFLG) ₂ was purified by column chromatography (LH-20, MeOH) and after solvent evaporation it was dried to constant weight. The content of tetrapeptide on the polymer was determined by amino acid analysis. Yield: 74%. The polymer chain transfer agent PPO-(GFLG-CTA) ₂ usable for controlled radical polymerization was then prepared by reaction of PPO(GFLG) ₂ with 2.5 fold excess of commercially available succinimide ester of 4-cyano-4-

(phenylcarbonothioylthio)pentanoic acid (CTA-NHS; 22.8 mg, 60.5 x 10 ^"3 mmol). NH ₂ - PPO-NH ₂ was dissolved in 0.5 mL of dichloromethane (DCM) and this solution was added to a suspension of CTA-NHS in 0.2 mL of DCM. The reaction mixture was allowed to react with stirring overnight. The crude product was purified on silica gel using a mixture solvent of chloroform/ethyl acetate (5/1) and chloroform/methanol (5/1). The solvent was evaporated and the product was dried under vacuum to constant weight. The product was characterized by TLC, HPLC and SEC. The functionality of terminal DTB groups of the final product was 1.96. Unless otherwise stated in what follows, all of the starting monomers and following polymers are always racemic mixtures.

Example 2: Synthesis of semitelechelic random copolymer poly(HPMA-co-MA-AH-NHNH- Boc)-TT (hydrophilic block A) using solution radical copolymerization

poly(HPMA-co-MA-AH- HNH-Boc)-TT

Semitelechelic random copolymer poly(HPMA-co-MA-AH- HNH-Boc)-TT, containing terminal thiazolidine-2-thione (TT) groups and protected hydrazide groups (-NHNH-Boc) along the polymer chain, was prepared by solution radical copolymerization of N-(2- hydroxypropyl) methacrylamide (HPMA) and methacryloyl-6-aminohexanoylhydrazide protected on hydrazide groups by tert-butyloxycarbonyl groups (MA-AH-NHNH-Boc) in DMSO at 60°C and initiated with initiator ABIK-TT (2-[(Z)-[l-cyano-l-methyl-4-oxo-4- (2-thioxothiazolidin-3-yl)butyl] azo]-2-methyl-5-oxo-5-(2-thioxothiazolidin-3-yl) pentanenitrile) (CZ 298 945). Characterization of the resulting copolymer: M _a (SEC) 12,400 g/mol; D ~ 1.60; F _iTT) 1.18; content (-NHNH ₂ ) ~ 5.4 mol%; R _h ~ 4.4 nm.

Following the procedure of Example 2, other copolymers poly(HPMA-co-MA-AH- NHNH-Boc)-TT were prepared analogously with different molecular weights M _n in the range from 4,000 to 58,000 g/mol, wherein the polydispersity index D was in all cases in the range from 1.5 to 1.8. The functionality of terminal TT groups was in the range from 110 to 120% /¾ = 1.10 to 1.20). The content of - HNH ₂ groups along the chain (0.5 to 19.5 mol%). See Table 1.

Table 1 : Physico-chemical characterization of semitelechelic random copolymers poly(HPMA-co-MA-AH- HNH-Boc)-TT prepared according to Example 2

Example 3 : Synthesis of semitelechelic random copolymer poly(HPMA-co-MA-GFLG- DOXJ-TT hydrophilic block A) using solution radical copolymerization

poly(HPMA-co-MA-GFLG-DOX)-TT Semitelechelic random copolymer poly(HPMA-co-MA-GFLG-DOX)-TT was prepared by solution radical copolymerization of HPMA and doxorubicin-containing monomer (N- methacryloylglycyl-DL-phenylalanylleucylglycyl)doxorubicin (Ma-GFLG-DOX), which was prepared by reaction of an equivalent amount of N-methacryloylglycyl-DL- phenylalanyl-L-leucylglycine 4-nitrophenyl ester (Ma-GFLG-ONp) with DOX.HC1 in DMF at 4 °C, in DMSO at 60°C and initiated with initiator ABIK-TT (2-[(Z)-[l-cyano-l- methyl-4-oxo-4-(2-thioxothiazolidin-3-yl)butyl]azo]-2-methyl -5-oxo-5-(2- thioxothiazolidin-3-yl)pentanenitrile). 220 mg (1.54 mmol) HPMA, 25 mg (0.025 mmol) MA-GFLG-DOX was dissolved in 1.7 mL DMSO and this solution was placed in a polymerization vial, which already has 84 mg (0.170 mmol) ABIK-TT (4 wt%) inside. The solution in the vial was bubbled with nitrogen for 15 min; the vial was sealed and placed in a thermostat heated to 60°C. The initiator dissolved after 3 min at 60°C. After 6 hours the reaction mixture was precipitated into 50 mL mixture of acetone - diethyl ether (2: 1). The copolymer was dissolved in 3 mL of methanol and precipitated again into 50 mL of the same precipitation mixture. The precipitated copolymer was filtered through S4 sintered glass filter and dried until constant weight. Characterization of the copolymer poly(FIPMA- co-MA-GFLG-DOX)-TT: M _A (SEC) 13,200 g/mol; D ~ 1.61 ; F _(TI) 1.20; content of GFLG monomer units: 3 mol%; content (DOX) ~ 8.9 wt%; R ~ 4.4 nm. Following the procedure of Example 3, other copolymers poly(HPMA-co-MA-GFLG-DOX)-TT were prepared analogously with different molecular weights M _A in the range from 4,500 to 59,500 g/mol, wherein the polydispersity index D was in all cases in the range from 1.5 to 1.8. The functionality of terminal TT groups was in the range from 1 10 to 120 % (F(TT = 1.10- 1.20). The content of GFLG groups along the chain (0.5 to 15 mol%). See Table 2.

Table 2: Physico-chemical characterization of semitelechelic random copolymers poly(FIPMA-co-MA-GFLG-DOX)-TT prepared according to Example 5

Sample M _n (g/mol) D F(TY) GFLG monomer unit Rh (nm)

(mol%)

3-1 13,200 1.61 1.20 3.0 4.4

3-2 4,500 1.63 0.96 5.6 3.8

3-3 16,800 1.76 0.95 15.0 4.6 3-4 39,800 1.74 0.94 9.8 4.8

3-5 59,500 1.61 0.96 0.5 5.2

Example 4: Synthesis of semitelechelic random copolymer raft-poly (HPMA-co-MA-AH- NHNH-Boc)-TT (hydrophilic block A ) using controlled radical RAFT polymerization

raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT

Semitelechelic random copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT, containing terminal thiazolidine-2-thione (TT) groups and protected hydrazide groups (- HNH-Boc) along the polymer chain, was prepared by controlled radical RAFT polymerization with the molar ratio of initiator/chain transfer agent/comonomers was 1/2/150. The ratio of comonomers HPM A/M A- AH- HNH-B oc was 92/8 mol%. HPMA was dissolved in tert-butanol (6,747 mL), M A- AH-NHNH-B oc, initiator 2-[(Z)-[l-cyano- l-methyl-4-oxo-4-(2-thioxothiazolidin-3-yl) butyl]azo]-2-methyl-5-oxo-5-(2- thioxothiazolidin-3-yl)pentanenitrile (ABIK-TT) and chain transfer agent [1-cyano-l- methyl-4-oxo-4-(2-thioxothiazolidin-3-yl)butyl]benzencarbodi thioate (CTA-TT) were dissolved in dimethyl sulphoxide (DMSO; 1,687 mL). These solutions were mixed together in a polymerization vial. The polymerization mixture was bubbled with argon for 10 min. Copolymerization was carried out at 70°C for 16 hours in a sealed vial. The product was isolated by precipitation into acetone/di ethyl ether 1 : 1, filtered off and dried to constant weight. Reactive co-terminal dithiobenzoate (DTB) groups were removed by 2,2'-azobisisobutyronitrile (AIBN). Characterization of the copolymer raft-poly(HPMA- co-MA-AH-NHNH-Boc)-TT: M _a (SEC) 8,400 g/mol; D ~ 1.20; F _(TT) 0.98; content (- HNH ₂ ) ~ 5.9 mol%; conversion ~ 46% (833 mg); R _h ~ 4.5 nm.

Following the procedure of Example 4, other copolymers raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT were prepared analogously with different molecular weights M _a in the range from 4,000 to 60,000 g/mol, wherein the polydispersity index D was in all cases in the range from 1.1 to 1.2. The functionality of terminal TT groups was in the range from 90 to 99 % (F( _TT ) = 0.90-0.99). The content of - HNH ₂ groups along the chain (0.5 to 20.5 mol%). See Table 3.

Table 3 : Physico-chemical characterization of semitelechelic random copoly poly(HPMA-co-MA-AH- HNH-Boc)-TT prepared according to Example 4

Example 5: Synthesis of telechelic random copolymer raft-TT-poly(HPMA-co-MA-AH- NHNH-Boc)-TT hydrophilic block A) using controlled radical RAFT polymerization

raft-TT-poly(HPMA-co-MA-AH- HNH-Boc)-TT Telechelic random copolymer raft-TT-poly(HPMA-co-MA-AH- HNH-Boc)-TT, containing terminal thiazolidine-2-thione (TT) groups and protected hydrazide groups (- HNH-Boc) along the polymer chain, was prepared using controlled radical RAFT polymerization similarly as in Example 4.

Only the co-terminal dithiobenzoate (DTB) groups were not removed using AIBN, but converted to TT as follows. 15% solution of polymer with ABIK-TT (10 wt%) in DMSO was prepared. The solution in the vial was bubbled with argon for 10 minutes, sealed and left for 3 hours at 80°C. The product was isolated by precipitation into the mixture of acetone/di ethyl ether 1 : 1, filtered off and dried to constant weight. Characterization: M _a (SEC) 8,500 g/mol; f ⁾ = 1.19; <Tr> 1.7; content (- HNH ₂ ) = 5.9 mol%; R _h = 4.8 nm. Following the procedure of Example 5, other copolymers raft-TT-poly(HPMA-co-MA- AH- fNH-Boc)-TT were prepared analogously with different molecular weights M _a in the range from 5,000 to 59,000 g/mol. See Table 4.

Table 4: Physico-chemical characterization of telechelic random copolymers raft-TT- poly(HPMA-co-MA-AH- HNH-Boc)-TT prepared according to Example 5

Example 6: Preparation of semitelechelic random copolymer raft-poly (HPMA-co-MA-AH- NHNH-Boc)-N3 (hydrophilic block A) using RAFT polymerization

raft-poly(HPMA-co-MA-AH- HNH-Boc)-N ₃

Semitelechelic random copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-N ₃ with terminal azide groups was prepared in a similar manner as the semitelechelic PHPMA- based copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT in Example 4. The molar ratio of initiator/chain transfer agent/comonomers was 1/2/180. The ratio of comonomers HPM A/M A- AH- HNH-B oc was 92/8 mol%. HPMA was dissolved in tert-butanol (6,747 mL), MA-AH- HNH-Boc, initiator N-(3-azidopropyl)-4-[(Z)-[4-(3-azidopropylamino)-l- cyano-l-methyl-4-oxo-butyl]azo]-4-cyano-pentanamide (ABIK-N ₃ ) and chain transfer agent [4-(3 -azidopropylamino)- 1 -cyano- 1 -methyl-4-oxo-butyl]benzencarbodithioate

(CTA-N ₃ ) were dissolved in dimethyl sulphoxide (DMSO; 1,687 mL). These solutions were mixed together in a polymerization vial. The polymerization mixture was bubbled with argon for 10 min. Copolymerization was carried out at 70°C for 16 hours in a sealed vial. The product was isolated by precipitation into the mixture of acetone/di ethyl ether (1 : 1), filtered off and dried to constant weight. Reactive co-terminal dithiobenzoate (DTB) groups were removed by 2,2'-azobisisobutyronitrile (AIBN). Characterization of the product: _n (SEC) 9,100 g/mol; D ~ 1.21; F _(m) 0.99; content (- HNH ₂ ) - 5.4 mol%; conversion ~ 63% (750 mg); ¾ ~ 4.5 nm.

Example 7: Synthesis of semitelechelic random copolymer raft-poly(HPMA-co-MA-AH- NHNH-Boc)-PDS (hydrophilic block A)

Semitelechelic random copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-PDS was prepared by reaction of semitelechelic random copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT (46.2 mg; 4.32 x 10 ^"3 mmol TT groups), prepared according to Example 4, with an excess of aminoethylpyridyldisulphide (1.90 mg, 8.64 x 10 ^"3 mmol) in DMA (0.5 mL) in the presence of a base (DIEA; 1.5 μL·, 8.64 x 10 ^"3 mmol). The crude product raft-poly(HPMA-co-MA-AH- HNH-Boc)-PDS was purified by column chromatography (Sephadex LH-20, MeOH). The product was precipitated into diethyl ether and dried under vacuum to constant weight. The content of terminal PDS groups was determined by UV- VIS spectroscopy. Characterization: M _a (SEC) = 10,890 g/mol; D = 1.11; F _(PDS ) = 0.80; content (- HNH ₂ ) = 5.8 mol%; conversion ~ 74% (34.7 mg); R _h = 4.7 nm.

Example 8: Synthesis of semitelechelic random copolymer raft-poly(HPMA-co-MA-AH- NHNH-Boc)-GFLG (hydrophilic block A)

Tetrapeptide GlyPheLeuGly (GFLG-) was, like tripeptide Asp-Pro-Lys, prepared by solid- phase peptide synthesis. Semitelechelic copolymer raft-poly(HPMA-co-MA-AH- TNH- Boc)-GFLG was prepared by modifying semitelechelic copolymer raft-poly(HPMA-co- MA-AH- HNH-Boc)-TT (Example 4) with tetrapeptide GFLG. Semitelechelic copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT (52.30 mg, 4.89 x 10 ^"3 mmol -TT) was dissolved in DMA and added to an excess of of tetrapeptide GFLG (10.30 mg, 24 x 10 ^"3 mmol). The reaction mixture was immediately treated with excess DIEA (16.74 μΐ _^ , 9.78 x 10 ^"3 mmol). The reaction mixture was allowed to react at room temperature overnight. The product was precipitated into diethyl ether, centrifuged, purified with LH-20 column in MeOH and dried under vacuum to constant weight. The sample was characterized by HPLC and SEC (M„ (SEC) = 10,770 g/mol; D = 1.10); content of tetrapeptide bound to the terminal TT group of the polymer was determined by amino acid analysis ( _n (calculated) = 10,933 g/mol; 3.59 wt%, i.e. 99% modification). Yield: 36.7 mg (68 %).

Example 9: Synthesis of telechelic random copolymer raft-GFLG-poly(HPMA-co-MA-AH- NHNH-Boc)-GFLG (hydrophilic block A) using controlled radical RAFT polymerization

Telechelic random copolymer raft-GFLG-poly(HPMA-co-MA-AH- HNH-Boc)-GFLG was prepared analogously to semitelechelic copolymer of Example 8. Characterization: M _n (SEC) = 11,500 g/mol; D = 1.12; conversion (65 %). Example 10: Preparation of the poly (propylene oxide)-tris(succinimidyl carbonate) (PPO- TSC; hydrophobic block B)

PPO-TSC

Poly(propylene oxide)-tris(succinimidyl carbonate) (PPO-TSC) was prepared according to the following procedure: the commercially available poly(propylene oxide)triol PPO(OH) ₃ (Aldrich; M ~ 5,000 g/mol; 85 mg; 51 x 10 ^"3 mmol -OH) was first twice dried by azeotropic distillation from dried, distilled toluene, then it was dissolved in toluene/DCM (0.637 mL/0.213 mL) and 20% solution of phosgene in toluene (0.5 mL) was added to the solution of PPO. The reaction mixture was allowed to react overnight. The following morning phosgene was evaporated to dryness under vacuum. The residue was dissolved into mixture of toluene/DCM (0.240 mL/0.120 mL), solid N-hydroxysuccinimide (58 mg, 0.504 mmol) and N,N-diisopropylethylamine (DIEA; 0.02 mL; 0.117 x 10 ^"3 mmol) were added to the mixture and the mixture was allowed to react at room temperature on a shaker overnight. The solvent was evaporated and the product was dried under vacuum to constant weight. The product was used without any further purification in the next reaction (see Example 12). Example 1 1 : Preparation of poly (propylene oxide)-bis(succinimidyl carbonate) (PPO- BSC; hydrophobic block B)

In the synthesis of poly(propylene oxide)-bis(succinimidyl carbonate) (PPO-BSC), the starting polymer is the commercially available poly(propylene oxide) (HO-PPO-OH) with M ~ 4,000 g/ mol. The preparation was analogous to the synthesis of PPO-TSC (see Example 10). The procedure in Example 11 was analogously used for activating terminal OH groups of poly(propylene oxide) with molecular weights M _n 2,000 to 17,000 g/mol.

Example 12: Preparation of PPO-(DBCO)3 (hydrophobic block B)

PPO-(DBCO) In the preparation of poly(propylene oxide) with terminal dibenzocyclooctyne groups (PPO (DBCO) ₃ ), the starting polymer was PPO-TSC prepared in Example 10 (85 mg; 51 x 10 ^"3 mmol TSC), which was dissolved in DCM. To a solution of polymer was added a solution of DBCO-amine (21.14 mg; 76.5 x 10 ^"3 mmol H ₂ ) in DCM together with DIEA (0.026 mL; 153 x 10 ^"3 mmol). The reaction mixture was allowed to react with stirring over the weekend. The solvent was evaporated under vacuum and the resulting product PPO- (DBCO) ₃ was purified by column chromatography (Sephadex LH-20, methanol). The fraction with the sample was evaporated under vacuum and the product was dried to constant weight. Yield: 81% (80 mg). The content of DBCO groups was 71% (2.12 groups per polymer chain). Following the procedure of Example 12, PPO-BSC prepared in Example 11 was analogously modified to give the resulting PPO-(DBCO) ₂ .

Example 13 : Preparation of poly (propylene oxide) modified by tripeptide Asp-Pro-Lys (PPO-(As -Pro-Lys) ₂ ; hydrophobic block B)

PPO-(Asp-Pro-Lys) ₂

PPO-(Asp-Pro-Lys) ₂ was prepared by modifying PPO-BSC (Example 11) with tripeptide Asp-Pro-Lys. Trifluoroacetate of tripeptide Asp-Pro-Lys was prepared by solid-phase peptide synthesis. PPO-BSC (50 mg; 0.05 mmol SC groups) was dissolved in dimethylformamide (DMF) and added to excess of tripeptide Asp-Pro-Lys .TFA (34 mg; 0.1 mmol). The reaction mixture was immediately treated with excess of DIEA (51 μΕ, 0.3 mmol). The reaction mixture was allowed to react at room temperature overnight. The product was triturated with diethyl ether and further purified with LH-20 column in MeOH. The polymer fraction was evaporated to dryness under vacuum and the product was dried to constant weight. Yield: 47 mg (70%). Similarly, other biodegradable linkers were attached to PPO-BSC or PPO-TSC, e.g. Asp-Pro-Leu, Asp-Pro-Ser, GlyPheGly, GlyLeuGly, GlyLeuPheGly and GlyPheLeuGly. Example 14: Preparation of PPO-S-S-DBCO (hydrophobic block B)

PPO-S-S-DBCO

In the preparation of poly(propylene oxide) with terminal dibenzocyclooctyne groups (PPO-S-S-DBCO), the starting polymer was H ₂ -PPO- H ₂ (30 mg; 7.5 x 10 ^"3 mmol), which was dissolved in DMF. To a solution of H ₂ -PPO- H ₂ (30 mg in 300 uL) was added a solution of DBCO-SS- HS (4,2 mg; 7.4 x 10 ^"6 mol) in DMF together with DIPEA (1.2 uL; 7 x 10 ^"6 mol). The reaction mixture was allowed to react with stirring for 3 hours. The solvent was evaporated under vacuum and the resulting product PPO-S-S-DBCO was purified by column chromatography (Sephadex LH-20, methanol). The fraction with the sample was evaporated under vacuum and the product was dried to constant weight. Yield: 79% (26 mg).

Example 15: Preparation of the A-L-B type amphiphilic diblock copolymer (frqfl- poly(HPMA-co-MA-AH-NHNH-Boc)]-S-S-PPO-NH ₂ ) with reductively and enzymatically cleavable S-S bond between the hydrophilic and hydrophobic blocks

Polypropylene oxide)-bis-2-aminopropylether (NH ₂ -PPO- H ₂ ; M ~ 4,000 g/mol; 11.33 mg; 5.66 x 10 ^"3 mmol - H ₂ ) was dissolved in MeOH (0.1 mL) pre-bubbled with argon. This solution was added to the commercially available 2-iminothiolane (0.39 mg, 2.83 x 10 ^"3 mmol - H ₂ ) and the reaction mixture was allowed to react. After 20 min the solution of raft-poly(HPMA-co-MA-AH- HNH-Boc)-PDS (30 mg, 2.83 x 10 ^"3 mmol) in MeOH (0.2 mL) was added to the reaction mixture and the reaction mixture was allowed to react for 2.5 hours. The product formation was monitored by SEC. The resulting diblock copolymer was purified by column chromatography (Sephadex LH-20, MeOH) and the solvent was evaporated under vacuum. The resulting product was dried to constant weight. Characterization of the prepared Boc-protected product: M _n (SEC) = 15,280 g/mol; D = 1.10; conversion ~ 65% (27 mg); R _h = 17.7 nm (in PBS). Example 16 Preparation of the A-L-B type diblock copolymer (raft-poly(HPMA-co-MA- AH- H H-Boc)-S-S-PPO- H ₂ II with reductively and enzymatically cleavable S-S bond between the hydrophilic and hydrophobic blocks, prepared by click reaction

The diblock copolymer (raft-poly(HPMA-co-MA-AH-NHNH-Boc)-S-S-PPO-NH ₂ II was prepared by click reaction, without copper catalysis, of copolymer (raft-poly(HPMA-co- MA-AH- HNH-Boc)-N ₃ ) (Example 6) and PPO-S-S-DBCO (Example 14). The copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-N ₃ was dissolved in 160 μΐ. of DMF. To this solution was added a solution of PPO-SS-DBCO (6.4 mg in 64 uL of DMF) and the reaction mixture was allowed to react overnight under constant stirring. The solvent was evaporated under vacuum and the resulting product was purified by column chromatography (Sephadex LH-20, methanol). The fraction with the sample was evaporated under vacuum and the product was dried to constant weight.

Example 17: Preparation of the A-L-B type amphophilic diblock copolymer (fraft- poly(HPMA-co-MA-AH-NHNH-Boc)]-GFLG-PPO-NH ₂ ) with enzymatically cleavable bond between the h drophilic and hydrophobic blocks

The semitelechehc copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-GFLG (23 mg; 2.15 x 10 ^"3 mmol), prepared in Example 8, was dissolved in DMF and its solution was added to H ₂ -PPO- H ₂ (M ~ 4,000 g/mol; 8.60 mg; 4.30 x 10 ^"3 mmol - H ₂ ) and solid N- hydroxysuccinimide (NHS; 1.96 mg; 17 x 10 ^"3 mmol). The reaction mixture was cooled using an ice water bath. To the reaction mixture was added a tenfold excess of NJP- diisopropylcarbodiimide (DIC) and the reaction mixture was allowed to react with stirring overnight. The product was purified on a column (LH-20, MeOH) and after evaporation of the solvent it was dried to constant weight. Characterization: M _n (SEC) = 15,500 g/mol; D = 1.11; conversion ~ 74% (23.6 mg); R _h = 19.2 nm.

Example 18: Preparation of the A-L-B-L-A type amphiphilic triblock copolymer (frafl- poly(HPMA-co-MA-AH-NHNH-Boc)] ₂ -GFLG-PPO) with enzymatically cleavable bond between the hydrophilic and hydrophobic blocks

The triblock copolymer ([raft-poly(HPMA-co-MA-AH-NHNH-Boc)] ₂ -GFLG-PPO was prepared in the same manner as the diblock copolymer (Example 17), when the semitelechelic copolymer raft-poly(HPMA-co-MA-AH-NHNH-Boc)-GFLG, prepared according to Example 8, and NH ₂ -PPO-NH ₂ were reacted in the presence of NHS and DIC in a molar ratio PHPMA: PPO 2: 1. Characterization: M _a (SEC) = 24, 100 g/mol; £> = 1.14; conversion ~ 70%; ¾ = 17.2 nm. Example 19: Preparation of the B-L-A-L-B type amphiphilic triblock copolymer (PPO[raft-GFLG-poly(HPMA-co-MA-AH-NHNH-Boc) J-GFLG-PPO) with enzymatically cleavable bond between the hydrophilic and hydrophobic blocks

The triblock copolymer PPO[raft-GFLG-poly(HPMA-co-MA-AH-NHNH-Boc)]-GFLG- PPO was prepared by reaction of raft-GFLG-poly(HPMA-co-MA-AH-NHNH-Boc)-GFLG (Example 9) with NH ₂ -PPO-NH ₂ in the presence of DIC and NHS in a similar manner as the triblock copolymer of Example 18, in a molar ratio PHPMA:PPO 1 :2. Example 20: Synthesis of the A-B type reference non-degradable amphiphilic diblock copolymer ([raft-poly(HPMA-co-MA-AH-NHNH-Boc) ]-b-PPO-NH ₂ )

[raft-poly(HPMA-co-MA-AH- TNH-Boc)]-6-PPO- H ₂

In the synthesis of Boc-protected diblock copolymer [raft-poly(HPMA-co-MA-AH- HNH-Boc)]-PPO- H ₂ we started from the commercially available poly(propylene oxide)-bis-2-aminopropyl ether ( H ₂ -PPO- H ₂ ; M ~ 4,000 g/mol; 33.2 mg, 16.6 x 10 ^"3 mmol - H ₂ ), which was dissolved in 1 mL of dimethylacetamide (DMA). Also the semitelechelic copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT, prepared in Example 4 (71 mg; 8.3 x 10 ^"3 mmol, M _n ~ 7,614 g/mol, F _TT ~ 0.89) was dissolved in 1 mL of DMA. The solution of copolymer raft-poly (HPMA-co-M A- AH- HNH-Boc)-TT was slowly added with stirring to a solution of H ₂ -PPO- H ₂ and the mixture was reacted under stirring at room temperature overnight. After about 16 hours, the reaction mixture was diluted with methanol (MeOH) and purified by column chromatography over Sephadex LH-20 in MeOH with RI and UV detection (230 nm) and TLC. The purified product was then evaporated under vacuum to constant weight. Yield: 80 mg (77%). Characterization of the Boc-protected diblock polymer [raft-poly(HPMA-co-MA-AH- HNH-Boc)]-PPO- H ₂ : M _w ~ 15,230 g/mol, M„ ~ 12,950 g/mol (in the organic mobile phase), D ~ 1.18, ¾ ~ 14 nm (in physiological saline or PBS).

Example 21 : Synthesis of the reference non-degradable amphiphilic triblock copolymer raft-poly(HPMA-co-MA-AH-NHNH-Boc) ] ₂ -PPO

[raft-poly(HPMA-co-MA-AH- HNH-Boc)] ₂ -PPO

The A-B-A type amphiphilic triblock copolymer [raft-poly(HPMA-co-MA-AH- HNH- Boc)] ₂ -PPO was prepared by the same procedure as its diblock analogue [raft- poly(HPMA-co-MA-AH HNH-Boc)]-PPO- H ₂ of Example 20, i.e. by polycondensation of H ₂ -PPO- H ₂ and semitelechelic copolymer raft-poly(HPMA-co-MA-AH- HNH- Boc)-TT. H ₂ -PPO- H ₂ (M ~ 4,000 g/mol; 28 mg; 14 x 10 ^"3 mmol - H ₂ ) and raft- poly(HPMA-co-MA-AH- HNH-Boc)-TT (115 mg; 14 x 10 ^"3 mmol, M _n ~ 8,450 g/mol, FIT ~ 0.98) were dissolved separately in DMA (1.575 mL). A solution of H ₂ -PPO- H ₂ was slowly added dropwise under vigorous stirring to a solution of the semitelechelic copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT and the reaction mixture was allowed to react with constant stirring at room temperature. After 24 hours the reaction mixture was precipitated into diethyl ether (47 mL). The fine precipitate was centrifuged and the solvent was decanted. The polymer product was dried under vacuum to constant weight. Yield: 120 mg (84%). Characterization of the prepared Boc-protected triblock copolymer [raft-poly(HPMA-co-MA-AH- HNH-Boc)] ₂ -PPO: M _w ~ 22,200 g/mol, M„ ~ 18,790 g/mol (in the organic mobile phase), D ~ 1.18, ¾ ~ 15 nm (in physiological saline or PBS). Example 22: Synthesis of the amphiphilic diblock copolymer poly(HPMA-co-MA-GFLG- DOX -GFLG-PPO-NH ₂ with a drug bound via an enzymatically cleavable oligopeptide

poly(HPMA-co-MA-GFLG-DOX)-GFLG-PPO- H ₂

The semitelechelic copolymer poly(HPMA-co-MA-GFLG-DOX)-TT of Example 3 was first end-modified by tetrapeptide GFLG in the same manner as in Example 8 and the resulting semitelechelic copolymer poly(HPMA-co-MA-GFLG-DOX)-GFLG was used together with H ₂ -PPO- H ₂ , DIC and NHS in the synthesis of diblock copolymer poly(HPMA-co-MA-GFLG-DOX)-GFLG-PPO-NH ₂ , where we followed the same procedure as in Example 17. Yield: 78%. Characterization of the diblock polymer poly(HPMA-co-MA-GFLG-DOX)-GFLG-PPO-NH ₂ : M _w ~ 20,300 g/mol, M„ ~ 15,650 g/mol (in the organic mobile phase), R _h ~ 15 nm (in physiological saline or PBS). Example 23 : Preparation of the A-L-B-L-A type triblock copolymer [raft-(polyHPMA)- GFLG] ₂ -PPO by RAFT polymerization using the polymer chain transfer agent PPO- GFLG-(CTA) ₂

[raft-(polyHPMA)-GFLG] ₂ -PPO

The A-L-B-L-A type triblock copolymer raft-(polyHPMA) ₂ -PPO was prepared by controlled radical RAFT polymerization using PPO-(GFLG-CTA) ₂ prepared in Example 1 as the chain transfer agent. The molar ratio of initiator/chain transfer agent/monomer was 1/2/150. HPMA (33.64 mg, 0.235 mmol) was dissolved in tert-butanol (0.232 mL), PPO (GFLG-CTA) ₂ (10 mg; 4.35 x 10 ^"3 mmol) and AfflN (0.36 mg; 2.18 x 10 ^"3 mmol) were dissolved in DMSO (0.026 mL). These solutions were mixed together in a polymerization vial. The polymerization mixture was bubbled with argon for 10 min and then the vial was sealed. Copolymerization was carried out at 70°C for 16 hours. The product was isolated by precipitation into acetone/di ethyl ether in the ratio 3/1. The fine precipitate was centrifuged, filtered off and dried to constant weight under vacuum. Reactive co-terminal DTB groups were removed using AIBN. Characterization: M _a (SEC) ~ 14,600 g/mol (in the organic mobile phase), D ~ 1.13; conversion ~ 60% (26 mg); ¾ ~ 14.5 nm (in physiological saline or PBS).

Example 24: Preparation of the A-L-B-L-A type triblock copolymer [raft-poly(HPMA-co- MA-AH-NHNH-Boc)-GFLG] 2-PPO by RAFT polymerization using the polymer chain trans er agent PPO- (GFLG-CTA) ₂

[poly(HPMA-co-MA-AH- HNH-Boc)-GFLG] ₂ -PPO

The triblock copolymer [raft-poly(HPMA-co-MA-AH- HNH-Boc) -GFLG] ₂ -PPO was prepared similarly as the triblock copolymer [raft-(polyHPMA)-GFLG] ₂ -PPO of Example 23. The molar ratio of initiator/chain transfer agent/comonomers was 1/2/150. The ratio of comonomers HPMA/M A- AH- HNH-B oc was 90/10 mol%. Reactive ω-terminal DTB groups were removed using AIBN.

Characterization: M _a (SEC) = 8,750 g/mol (in the organic mobile phase); D 1.56; conversion 50% (8.3 mg); ¾ 14.0 nm (in physiological saline or PBS). Example 25: Preparation of a Boc-protected diblock copolymer containing in its structure biodegradable linkers Asp-Pro-Lys

Block copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT and PPO-(Asp-Pro-Lys) ₂

The biodegradable diblock copolymer was prepared by polycondensation of the copolymer raft-poly(HPMA-co-MA-AH- HNH-Boc)-TT and PPO-(Asp-Pro-Lys) ₂ in a similar manner as the amphiphilic diblock copolymer [raft-poly(HPMA-co-MA-AH- HNH- Boc)]-PPO- H ₂ (see Example 20). In a similar manner diblock copolymers containing other biodegradable oligopeptide linkers were prepared as listed in Example 13.

Example 26: Preparation of the A-L-B-L-A type biodegradable triblock copolymer based on raft-poly(HPMA-co MA-AH-NHNH-Boc)-TT and PPO-(Asp-Pro-Lys) ₂

Block copolymer raft-poly(HPMA-co MA-AH- HNH-Boc)-TT and PPO-(Asp-Pro-Lys) ₂ A biodegradable triblock copolymer based on raft-poly(HPMA-co-MA-AH- HNH-Boc)- TT and PPO-(Asp-Pro-Lys) ₂ , containing a hydrolytically and enzymatically biodegradable peptide sequence Asp-Pro-Lys between the hydrophilic block A and hydrophobic block B, was prepared in a similar manner as the amphiphilic diblock copolymer raft-poly(HPMA- co-MA-AH-NHNH-Boc)-PPO (see Example 20), i.e. by polycondensation of the copolymer raft-poly (HPMA-co-M A- AH- HNH-Boc)-TT and polymer PPO-( Asp-Pro- Lys^ in a molar ratio of 2: 1. In a similar manner triblock copolymers containing other biodegradable oligopeptide linkers were prepared as listed in Example 13.

Example 27: Removal of a Boc protecting group on hydrazide groups of the diblock polymer precursor [raft-poly(HPMA-co-MA-AH-NHNH-Boc) ]GFLG-PPO-NH ₂

[raft-poly(HPMA-co-MA-AH-NHNH ₂ )]-GFLG-PPO-NH ₂

The diblock polymer precursor [raft-poly(HPMA-co-MA-AH- HNH ₂ )]-GFLG-PPO- H ₂ was prepared from the diblock copolymer [raft-poly (HPMA-co-M A- AH- HNH-Boc)]- GFLG-PPO- H ₂ of Example 17 (50 mg) containing hydrazide groups protected by tert- butyloxycarbonyl group (Boc). The diblock copolymer [raft-poly(FIPMA-co-MA-AH- TNH-Boc)]-GFLG-PPO- H ₂ was dissolved in 1.08 mL of a mixture of trifluoroacetic acid (TFA)/triisopropylsilane (TIS)/water (95/2.5/2.5). Immediately after dissolving, the mixture was evaporated under vacuum to dryness. The residue was then dissolved in a borate buffer (pH 8.0; 200 pL) and the pH of the solution was adjusted by titration with a saturated NaOH solution to pH 6.5-8.0. The crude product was desalted and purified using a PD10 column (Sephadex G25) in water and lyophilized. Yield: 40 mg (78%). Characterization: M _w = 16,200 g/mol, M _n = 13,500 g/mol (in the organic mobile phase), R _h ~ 14.5 nm (in physiological saline or PBS).

In the same manner these protecting groups were removed also from polymer precursors prepared in Examples 15 to 21 and 24 to 26

Example 28: Preparation of a diblock polymer conjugate with a drug bound via hydrolytically labile hydrazone linkage:

(A) Diblock polymer conjugate [raft-poly(HPMA-co-MA-AH- HN=DOX)]-GFLG- PPO- H ₂ with a hydrazone bound doxorubicin

The diblock polymer precursor [raft-poly(HPMA-co-MA-AH- HNH ₂ )]-GFLG-PPO-NH ₂ , prepared in Example 27, with free hydrazide groups (120 mg) was dissolved in MeOH (960 pL). The polymer solution was added to the solid doxorubicin hydrochloride (DOX. HCl; 12.94 mg) and to the suspension was added 38.4 μΙ_, of concentrated acetic acid. The reaction mixture was shaken on a shaker in the dark at room temperature overnight. The reaction was monitored by TLC (CHCl ₃ /MeOH/acetic acid ~ 8/2/1). After 24 hours the reaction mixture was diluted with MeOH and the crude product was purified by column chromatography in MeOH over Sephadex LH-20. The polymer fraction was evaporated under vacuum to dryness and dried to constant weight. The content of bound doxorubicin was determined spectroscopically (λ ~ 488 nm, water, ε ~ 9,800 L x mol ^"1 x cm ^"1 ). The yield was 110.8 mg (83%), the content of drug on the polymer was 8.9 wt%. Characterization: M _w = 18,300 g/mol, M _n = 14,100 g/mol (in the organic mobile phase), R _h ~ 14.2 nm (in physiological saline or PBS). In a similar manner a diblock polymer conjugate with a drug pirarubicin or daunorubicin was prepared; the drug content for these conjugates was 9.9 wt% of pirarubicin or 9.5 wt% of daunorubicin.

Characterization of a conjugate with pirarubicin: _w = 19,200 g/mol, M _a = 14,300 g/mol (in the organic mobile phase), R ~ 14.4 nm (in physiological saline or PBS). Characterization of a conjugate with daunorubicin: _w = 18,800 g/mol, M _a = 14,500 (in the organic mobile phase), Rh ~ 13.9 nm (in physiological saline or PBS).

(B) Diblock polymer conjugate with a hydrazone bound docetaxel derivative

[raft-poly(HPMA-co-MA-AH- HN=DTX-LEV)]-GFLG-PPO- H ₂ The docetaxel derivatized by levulinic acid (DTX-LEV) was prepared by reacting docetaxel with levulinic acid in the presence of diisopropylcarbodiimide in DMSO. The diblock polymer precursor [raft-poly(HPMA-co-MA-AH- HNH ₂ )]-GFLG-PPO- H ₂ prepared in Example 27 (191.5 mg) and the derivative of drug DTX-LEV (22.9 mg) were dissolved in MeOH (172 [iL) and the reaction mixture was immediately treated with concentrated acetic acid (70 [iL). The reaction mixture was stirred for 2.5 hours. It was then diluted with MeOH and the product was purified by column chromatography in MeOH (Sephadex LH-20, MeOH; UV detection - 230 nm, RI]. The fraction of the polymer conjugate with DTX-LEV was collected, evaporated to dryness under vacuum and dried to constant weight. The yield was 172 mg (80%). Characterization: _w = 17,500 g/mol, M _a = 13,600 g/mol (in the organic mobile phase), R _h ~ 14 nm (in physiological saline or PBS). The content of the DTX-LEV derivative, after complete acidic hydrolysis (HC1 with pH ~ 2.0) and extraction into chloroform, was determined by chromatography (HPLC) to be 9.0 wt%. In a similar manner also paclitaxel and larotaxel were derivatized and then both drugs were bound to a polymer carrier following the procedure as described above. Characterization of the conjugate with paclitaxel: _w = 18,500 g/mol, M _a = 14, 100 g/mol (in the organic mobile phase), ¾ ~ 14.3 nm (in physiological saline or PBS). The content of paclitaxel-LEV derivative was 9.6 wt%. Characterization of the conjugate with larotaxel: _w = 17,800 g/mol, M _a = 14,200 g/mol (in the organic mobile phase), R _h ~ 14.1 nm (in physiological saline or PBS). The content of larotaxel -LEV derivative was 9.4 wt%. After removal of Boc protecting groups according to Example 27, it is possible using the same procedure as in Example 28 to bind the above-mentioned drugs even to polymer precursors prepared in Examples 15 to 21 and 24 to 26.

Example 29: Preparation of a lyophilized form of polymer-drug conjugates

The block polymer-drug conjugates prepared as in Example 28 and the block polymer precursors without drugs were by lyophilization with additives converted into a lyophilized form, which facilitates conversion of a solid form of polymer drug into a solution and formation of nanoparticle micellar structures within 1 minute after adding the appropriate buffer or physiological saline.

The diblock polymer-drug conjugate prepared in Example 28 (100 mg; 8.7 wt% of DOX bound to polymer), NaH ₂ P0 ₄ x 2 H ₂ 0 (2.40 mg), Na ₂ HP0 ₄ x 2H ₂ 0 (9.54 mg) and lactose (332 mg) were dissolved in distilled water, the solution was frozen and lyophilized. The resulting lyophilizate (100 mg of the original polymer conjugate with the drug) was dissolved in 17.2 mL of an aqueous solution of NaCl with concentration of 9 g/L (physiological saline). Lyophilization cakes of polymer precursors and their conjugates with drugs were dissolved in physiological saline (0.9% of NaCl), which was prior to use filtered through Whatman membrane (PVDF) with a pore size of 0.20 μπι.

Example 30: Example of characterization of polymer precursors and conjugates

The prepared copolymers, polymer precursors and their conjugates with drugs were characterized by determination of weight and number average of molecular weights (M _w , M _n ) and the respective polydispersity index (£ ⁾ ) by means of the size exclusion chromatography (SEC) performed on a system equipped with an UV detector (Shimadzu, Japan), RI detector (Optilab REX, Wyatt Technology Corp., USA) and a multiangle light scattering detector (DAWN-Heleos II Wyatt Technology Corp., USA). Some systems were characterized using a FFF system (Eclipse 3+ module) equipped with DLS (DAWN 8+; Wyatt Technology Corp., USA), UV and RI (Optilab REX; Wyatt Technology Corp., USA) detection. For characterization, the TSK 3000 Super SW column was used in the case of SEC and the mixture of MeOH (80%) and 0.3M acetate buffer with pH 6.5 (20%) as a mobile phase, in the case of FFF the membrane of regenerated cellulose (10 kDa) was used for separation and water with NaN ₃ as a mobile phase. The concentration of samples in all cases was 3 mg/mL.

The content of terminal -DTB, -DBCO,-TT groups and hydrazide groups copolymerized randomly along the polymer chain was determined spectrophotometrically. All measurements were performed on a UV-VIS spectrophotometer Specord 205 (Analytik Jena, Germany). The content of -TT groups was determined according to the literature (Subr, V.; Konak, C.; Laga, R.; Ulbrich, K. Biomacromolecules 2006, 7(1): 122-130) in methanol (¾05 = 10,800 L . mol ^"1 . cm ^"1 ). The content of hydrazide groups (after deprotecting by a mixture of TFA (95%), triisopropylsilane (2.5%) and water (2,5%)) was determined according to the method described in Etrych, T.; Jelinkova, M., Rihova, B. and Ulbrich, K., J. Control. Release 2001; 73 : 89-102 (ε ₅₀ ο = 17,200 L . mol^.cm ^"1 ). The content of terminal -DBCO or -DTB groups was determined spectrophotometrically in MeOH (-DTB: ε ₃₀₂ = 12,400 L . mol^.cm ^"1 , -DBCO: ¾ ₀₂ = 13,000 L . mol ^"1 . cm ^"1 ). The content of PDS groups was determined spectrophotometrically {ε ₃₄₃ = 8,080 L . mol ^"1 . cm ^{" l} ).

The sizes of nanoparticles, consisting of polymer precursors and conjugates with drugs in an aqueous medium, were determined by techniques of dynamic light scattering (Nano-ZS Zetasizer, Malvern) and static light scattering (ALV instrument, Germany) in aqueous buffer (PBS, pH 7.4). The static light scattering was measured in the range from 30 to 140° with steps of 10° at a concentration of 0.5 to 10 mg/mL and temperatures of 25°C and 37°C. The particle size distribution curve is shown in Figure 1.

Example 31 : Release of a drug

(A) Polymer conjugates with doxorubicin prepared according to Example 28A: The amount of doxorubicin released from polymer micelles was determined after incubation of polymer conjugates with DOX at 37°C in a phosphate buffer with pH 5.0 (0.1 M phosphate buffer containing 0.05 M of NaCl) modelling the environment in endosomes and lysosomes of tumour cells, and in a phosphate buffer with pH 7.4 (0.1 M phosphate buffer containing 0.05 M of NaCl), which models the bloodstream environment. A portion of the incubation solution was collected at predetermined time intervals and the amount of released DOX was determined by SEC (Shimadzu, Japan; isocratic flow rate 0.3 mL/min; mobile phase: MeOH (80%)/0.3 M acetate buffer with pH 6.5 (20%)) on TSK 3000 Super SW column.

The amount of released DOX was calculated from the peak areas of free and bound DOX detected at a wavelength of 488 nm. While during incubation of polymer micelles at pH 5.0 there was a rapid release of DOX from the carrier (more than 70% of DOX released after 9 hours of incubation), during incubation of polymer conjugates in physiological environment (pH 7.4) the hydrolysis of hydrazone bond does practically not work and the drug is released only very slowly (up to 9% in 24 hours). The rate of DOX release from our prepared nanoparticulate systems in both environments (pH 5.0 and pH 7.4) is shown in Figure 2.

(B) Polymer conjugates with docetaxel derivative prepared according to Example 28B: The amount of docetaxel (DTX) or derivatives thereof released from polymer conjugates after their incubation in a phosphate buffer with pH 5.0 (0.1 M phosphate buffer containing 0.05 M of NaCl) modelling the intracellular environment and in a phosphate buffer with pH 7.4 (0.1 M phosphate buffer containing 0.05 M of NaCl) modelling the bloodstream environment was determined by HPLC. At predetermined time intervals 200 μΐ. of incubation solution was collected and after the extraction of released drugs and derivatives thereof into chloroform their amounts were determined using an HPLC system (Shimadzu HPLC system equipped with a column with a reverse phase Chromolith Performance RP- 18e (100 x 4.6 mm) and UV-VIS detector Shimadzu SPD-lOAVvp (230 nm), eluent water- acetonitrile with gradient from 50 to 100 vol% of acetonitrile, flow rate of 0.5 mL x min ^"1 ). After incubation of the conjugates (concentration 5 mg/mL) in a physiological environment at 37°C (phosphate buffer, pH 7.4) the drug DTX (or its derivative) is released significantly slower (Fig. 3) than in a slightly acidic environment at pH 5.0 modelling the environment in endosomes and lysosomes of tumour cells (Fig. 3). The disintegration of the drug derivative into free drug or direct cleaving of the drug from the polymer conjugate is presumably by the effect of enzymes, especially carboxyesterases.

Example 32: The disintegration of PHPMA-L-PPO-based micelles

The disintegration of PHPMA-L-PPO-based micelles into polymer chains eliminable from the organism is possible in two ways: i) after the decrease in concentration of the sample below the critical micelle concentration (CMC), or ii) after the disintegration of biodegradable linkers between the copolymer blocks, or a combination of both procedures. The copolymer prepared according to Example 15, 17 and 25 was (after removal of Boc - protecting groups according to Example 27) dissolved in PBS buffer (0.15 moll ^"1 , pH 7.4) to a micellar solution at a concentration of 2 mg/mL and then diluted. The size of the micelles was monitored by a dynamic light scattering (QELS) technique. The CMC was measured with isothermal calorimetry (ITC). The CMC of deprotected diblock copolymers of Examples 15, 17 and 25 was set as 0.01 to 0.02 mg/mL. Below this concentration the micelles disintegrate into individual polymer chains eliminable from the organism.

Enzymatic, hydrolytic and reductive degradations of deprotected PHPMA-L-PPO-based polymer diblock of Example 15, 16, 17, 18, 19, 22, 23, 24, 25 and 26 were studied in 0.1 M phosphate buffer (NaH ₂ P0 ₄ /NaOH, pH = 6.0; 5 mM glutathion; 1 mM EDTA), containing the lysosomal enzyme cathepsin B, intracellular enzyme thioredoxin, i.e. in the environment modelling the intracellular environment of the tumour cells at substrate concentration of 10 mg/mL. Deprotected diblock or triblock copolymers of Examples above were dissolved in phosphate buffer at a concentration of 10 mg/mL and immediately before they are placed into a thermostat (temperature 37°C), an enzyme stock solution was added to get final concentration of cathepsin B or thioredoxin of 5.10 ^"7 M. In cases of experiments which determine a simple hydrolytic or reductive degradation no enzyme was added to the solution. Aliquots (200 μΕ) of incubation solutions were collected at predetermined time intervals, which were desalted on PD-10 columns and lyophilized. The molecular weight of degradation products was measured in the same manner as described above (Example 30). Conjugates containing oligopeptide spacer Asp-Pro-Lys or GFLG and others were slowly degraded in a solution comprising cathepsin B (5.10 ^"7 M).

After 48 hours of incubation with cathepsin B it was determined that 40% of polymer portions are in the form of soluble portions having a molecular weight below the threshold for renal filtration. Polymer conjugates with spacer Asp-Pro-Lys disintegrated even by simple hydrolysis, after 48 hours it was determined that 20% of the polymer portion is degraded. Similarly, reductive degradation using thioredoxin and glutathione proceeded very rapidly, after 10 hours these polymer conjugates degraded into individual polymer components. The aforementioned experiment confirmed the biodegradability of the block polymer conjugates into degradation products eliminable from the organism.

Example 33 : In vitro cytotoxic activity of the diblock and triblock polymers based on biodegradable PHPMA-L-PPO copolymers

The cytotoxic activity of biodegradable diblock and triblock polymer precursors based on PHPMA-L-PPO was studied in several cancer cell lines, particularly the neuroblastoma cell lines B3, B4 and the derived lines resistant to DOX ( B3/DOX and B4/DOX), further in cell lines of T-cell lymphoma EL4, P388 lymphoma and derived resistant line P388/MDR. In in vitro experiments the cell viability was determined after 72 hours of incubation with various concentrations of the diblock and triblock polymer precursor using the AlamarBlue method. It was found that not even the concentration of 500 μg/mL of these polymer systems is toxic to the cells; it does not decrease their viability.

Example 34: In vitro biological activity of the diblock and triblock polymers based on PHPMA-L-PPO as inhibitors ofP-gp

The ability of biodegradable diblock and triblock polymers to inhibit transmembrane pumps, namely P-gps, which are one of the main causes of drug resistance, was demonstrated using a calcein assay. Experiments were performed in neuroblastoma cell lines B3, B4 and derived lines resistant to doxorubicin B3/DOX and B4/DOX and in lymphoma cell line P-388/MDR. In the aforementioned cell lines it was demonstrated that the drug resistance is caused by overexpression of P-gp.

In in vitro experiments the cells were incubated with various concentrations of biodegradable diblock and triblock polymers for various periods of time (0.5 hour, 2 hours and 6 hours or 4 hours, 8 hours and 24 hours), and then Calcein^ was added thereto for 20 minutes, which is cleaved in the cells into fluorescence-activated Calcein (excitation 485 nm/emission 530 nm). At the same time, Calcein is removed from the cells with increased activity of P-gp. The extent of ability to inhibit P-gp was determined as the fluorescent activity of Calcein as compared to control (10 mM Cyclosporin A - CsA, low molecular weight inhibitor of P-gp). The significant ability to inhibit P-gp was detected in all studied DOX resistant lines, namely B3/DOX (Fig. 4), B4/DOX (Fig. 5) and P388/MDR (Fig. 6). For all cell lines, the highest rate of P-gp inhibition was observed for the highest concentrations 250 and 500 μg/mL and decreased with decreasing concentration of the polymers used. Degradable polymer diblocks PPO-L-pFIPMA showed in all studied lines significantly higher inhibition ability than the non-degradable PPO- pFIPMA system (prepared in Example 20). For parental cell lines B3, NB4 and P388 no determinant change was detected, which is consistent with the very low expression of P-gp in these cell lines. The studied concentrations of polymers ranging from 30 to 250 μg/mL are fully consistent with the expected concentrations of polymer systems used in the treatment of solid tumours exhibiting a multiple drug resistance. An increase of P-gp inhibition was observed in the use of all the degradable polymer conjugates. Given the rate of disintegration of the amphiphilic polymer systems, the highest P-gp inhibition was observed for systems with a disulphide linker, where the degradation rate was the highest. Example 35: Comparison of the in vitro biological activity of diblock and triblock conjugates - influencing the cytotoxic effect

The effect was monitored of P-gp inhibition in the cells of neuroblastoma lines using the diblock copolymer of pFIPMA-L-PPO of Example 15 (where L is a disulphide linker) and triblock copolymer (PHPMA-L) ₂ -PPO (where L is Asp-Pro-Lys) prepared in Example 26, with free hydrazide groups removed as described in Example 27, on the change of IC ₅₀ of drugs: i) DOX; ii) polymer doxorubicin PFIPMA-DOX (the linear hydrazone conjugate with DOX based on PHPMA); iii) a diblock polymer conjugate of Example 28 (DB-DOX). In in vitro experiments the cells were first incubated for 1 hour with/without a diblock or triblock copolymer at a concentration 250 μg/mL and thereto were added the above mentioned drugs in a concentration series. After 72 hours of incubation the metabolic activity of cells was determined using the AlamarBlue method and from it the IC ₅₀ of individual drugs. The results are shown in Table 5. An experiment was performed with non-degradable diblock polymers PHPMA-PPO (Example 20) and triblock polymers (PHPMA) ₂ -PPO (Example 21) as a control.

Table 5: Increased cytotoxicity of drugs: doxorubicin (DOX), the linear hydrazone conjugate with DOX based on PHPMA (PHPMA-DOX) and the A-L-B type diblock conjugate of Example 28 (DB-DOX) caused by blocking the P-gp transmembrane pumps in neuroblastoma cell lines resistant to doxorubicin: NB3/DOX and B4/DOX, measured by the AlamarBlue method. Table 5 shows the IC ₅₀ values, i.e. concentrations in μ§/ιηΙ. at which the viability of one half of test cells is reduced.

IC ₅₀ after 72 hours of incubation B3/DOX NB4/DOX

DOX 0.215 ± 0.004 2.61 ± 0.17

DOX + PHPMA-PPO (250 ug/mL) 0.020 ± 0.001 0.42 ± 0.03

DOX + PHPMA-L-PPO (250 ug/mL) 0.010 ± 0.001 0.25 ± 0.02

IC50 after 72 hours of incubation B3/DOX

DOX 0.168 ± 0.005

DOX + (PHPMA) ₂ -PPO (250 ug/mL) 0.032 ± 0.003

DOX + (PHPMA-L) ₂ -PPO

(250 ug/mL) 0.020 ± 0.002

IC ₅₀ after 72 hours of incubation NB3/DOX B4/DOX

PHPMA-DOX 2.596 ± 0.132 35.00 ± 2.79

PHPMA-DOX + PHPMA-PPO

(250 ug/mL) 0.340 ± 0.006 5.60 ± 0.32

PHPMA-DOX + PHPMA-L-PPO

(250 ug/mL) 0.180 ± 0.004 2.90 ± 0.21

IC50 after 72 hours of incubation NB3/DOX

PHPMA-DOX 3.338 ± 0.110

PHPMA-DOX + (PHPMA) ₂ -PPO

(250 ug/mL) 0.521 ± 0.006

PHPMA-DOX + (PHPMA-L) ₂ -PPO

(250 ug/mL) 0.385 ± 0.009

IC ₅₀ after 72 hours of incubation B3/DOX B4/DOX

DB-DOX 0.919 ± 0.020 7.07 ± 0.11

DB-DOX + PHPMA-PPO

(250 ug/mL) 0.152 ± 0.007 3.92 ± 0.13

DB-DOX + PHPMA-L-PPO 0.101 ± 0.005 2.85 ± 0.16

Table 5 shows that both PHPMA-L-PPO (copolymer of Example 15) and (PHPMA-L) ₂ - PPO (copolymer of Example 26 with free hydrazide groups) at a concentration of 250 μg/mL ensured the increase of cytotoxicity, i.e. reduction of IC ₅₀ value of the polymer conjugate PHPMA-DOX and free DOX by more than one order of magnitude. A slightly higher effect was observed in PHPMA-L-PPO than in (PHPMA-L) ₂ -PPO. For PHPMA-L- PPO higher effect was observed on tumour resistant cell line B3/DOX that expresses higher amounts of P-gp transmembrane pump. From the aforementioned results it can be concluded that the inhibitory effect on resistant tumour cells will be higher, the higher the level of P-gp transmembrane pumps is. When comparing degradable systems PHPMA-L- PPO and (PHPMA-L) ₂ -PPO with non-degradable systems PHPMA-PPO and (PHPMA) ₂ - PPO, the degradable systems seem approximately twice as good, which is fully in accordance with the results of calcein assay. A similar increase in cytotoxicity was observed even when other degradable conjugates were used. Given the rate of disintegration of the amphiphilic polymer systems, the highest inhibitory ability against P- gp was observed for systems with a disulphide linker, where the degradation rate was the highest.

The actual diblock polymer conjugate of Example 28 (DB-DOX) exhibits a 3 to 5 times higher cytotoxicity in both resistant neuroblastoma cell lines than PHPMA-DOX, a linear hydrazone conjugate with DOX (concentration of DB carrier at IC ₅₀ is approximately 10 μ^ηύ,). Adding PHPMA-L-PPO (copolymer of Example 15) to the DB-DOX conjugate of Example 28 increased the cytotoxicity of DB-DOX less than in the case of PHPMA-DOX or free DOX. The effect of PHPMA-L-PPO is already evident in the biological in vitro activity of DB-DOX itself and adding of PHPMA-L-PPO (copolymer of Example 15) has only a supplementary effect.

It was demonstrated that the degradable diblock polymer PHPMA-L-PPO is capable of increasing the cytotoxic effect in selected resistant tumour cell lines by more than one order of magnitude. This effect is shown for both other long-circulating polymer drugs (e.g. PHPMA-DOX) and classical low molecular weight drug DOX. The actual polymer conjugate with a drug based on block copolymers PHPMA-L-PPO of Example 28 (DB- DOX) shows significantly higher cytostatic effect on resistant tumour cell lines than similar PHPMA-based polymer systems. Example 36: Cytostatic in vitro activity of the biodegradable diblock micellar doxorubicin conjugate of Example 28 A (DB-DOX) when acting upon the tumour cell lines

To demonstrate the cytostatic activity of the micellar diblock polymer conjugate carrying doxorubicin of Example 28A (DB-DOX) the cells were used of several stable tumour cell lines having different origins. These were murine tumour cell lines (CT26 - colon carcinoma cell line, 4T1 - mammary carcinoma cell line, both originating from the BALB/c inbred strain of mice, followed by EL4.IL-2-line of T-cell lymphoma originating from the C57BL/6 inbred strain of mice) and FaDu - a human line of squamous cell carcinoma of the head and neck. The cells were cultured in 96-well culture plates with different concentrations of DB-DOX for 72 hours. The cell proliferation was then determined using the standard method of incorporating ³ H-thymidine which was added for the last 6 hours of culture. Subsequently, the cultures were processed using the Tomtec Mach III harvester and, after drying, the radioactivity of samples obtained was measured by the beta-scintillation counter Microbeta Trilux (Wallac) using a solid scintillant (MeltiLex; Perkin Elmer). Test results are expressed as IC ₅₀ value equal to the concentration of DB-DOX (indicated in terms of doxorubicin content in the conjugate), which is required for induction of just 50% inhibition of growth (proliferation) of the tumour cells in question (see Table 6). The cytostatic activity of DB-Dox was compared with the activity of other micellar HPMA-based conjugate with doxorubicin (HPMA copolymer with cholesterol units self-assembling into micellar structures, for reference see Chytil P., Etrych T., Sirova M., Mrkvan T., Rihova B., Ulbrich K., J. Controlled Release 127, 121-130, 2008), and further with the activity of the linear HPMA copolymer with doxorubicin (water-soluble HPMA copolymer, for reference see Etrych Τ. _Λ Jelinkova M., Rihova B., Ulbrich K, J. Controlled Release 73, 89-102,2001), and with a free drug.

Table 6: Cytostatic effectiveness of DB-DOX of Example 28 A, other HPMA-based conjugates and free doxorubicin in four selected tumour cell lines. The activity of conjugates was determined by ³ H-thymidine incorporation after 72 hours of incubation of cells with various concentrations of drugs. The IC ₅₀ values are given in ng of doxorubicin/mL and were calculated as a mean of several independent determinations.

For all lines tested, namely those sensitive to doxorubicin (FaDu) or slightly sensitive (CT26), it can be seen that the cytostatic activity of DB-DOX (conjugate according to Example 28A) is equal to or even slightly higher than that of another type of micellar conjugate based on FIPMA. The linear conjugate with doxorubicin (DOX-PFIPMA) showed activity in all lines substantially lower than DB-DOX (conjugate of Example 28). For the line having a high degree of natural resistance to a cytostatic agent (CT26) the cytostatic effect of doxorubicin decreased by binding the drug to a diblock carrier only 2.6 times, while for more drug sensitive lines it was 6 to 8.6 times (EL4.IL-2 and FaDu) (see Table 6). In the entire range of concentrations used the amount of diblock polymer system was lower than concentrations demonstrated as functional in the ABC transporter blockade, see above. The diblock micellar conjugate with doxorubicin (conjugate of Example 28) shows a significant cytostatic activity against tumour cell lines of various origins in vitro.

Example 3Ί. In vivo biological activity of micellar diblock conjugate with doxorubicin of Example 28A (DB-DOX) in the treatment of murine T-cell lymphoma EL4

The in vivo antitumour effect of micellar diblock polymer conjugate of Example 28 carrying doxorubicin (DOX-DB) was studied on a model of murine T-cell lymphoma EL4 in the C57BL/6 inbred strains of mice. The conjugate was administered to mice intravenously (i.v.) in a single dose equivalent to 7.5 mg of doxorubicin/kg. The drug was injected 8 days after subcutaneous administration of 1 x 10 ⁵ EL4 tumour cells, at a time when tumours are developed and the tumour bed size is about 6-8 mm in diameter. For comparing the therapeutic effect of the diblock copolymer of Example 28A (DB-DOX), we administered the linear FIPMA copolymer with doxorubicin (PUPMA-DOX) at the same dose. Both the micellar diblock conjugate of Example 28A (DB-DOX) and linear conjugate (PUPMA-DOX) carried doxorubicin linked via a hydrazone bond. Further, the free doxorubicin (DOX) was used for treatment, injected at a total dose of 10 mg/kg, which, due to the different pharmacokinetics of a low molecular weight drug and the associated danger of high systemic toxicity, was injected in two partial intravenous doses on the 8 ^th and 12 ^th day after transplantation of tumour cells (each dose of 5 mg of doxorubicin).

Mice in the group treated with the diblock conjugate of Example 28A (DB-DOX) showed in comparison to untreated controls a tumour growth stagnation within three days and a significant reduction in growth between the third and sixth day after administration of the drug. A similar stagnation of tumour growth showed also the linear conjugate treated group (PHPMA-DOX), within six days there was a reduction in tumours, but was less pronounced than in the group treated with DB-DOX (conjugate of Example 28). In contrast, in the group treated with free doxorubicin (DOX) the average tumour growth was slower than in the group of untreated mice, but showed a steady progression. As early as the eighth day after drug administration the first mouse with complete tumour regression appeared in the group treated with DB-DOX, 13 days after drug administration there were 4 mice in the group (out of 8) without apparent tumour at the place of administration, while in other mice the tumours gradually grow, however their size was always significantly lower than in untreated controls at the same time. The reappearance of a small tumour bed in the original localization occurred in one out of 4 mice in which the complete tumour regression has been previously observed, and this was very late (after the 40 ^th day of experiment, that is 32 days after drug administration). The mean survival of untreated mice is 29 days (SD 2.0 days, mean survival time 29 days). The diblock conjugate DB-DOX (conjugate of Example 28) thus eventually induced complete cure in 3 out of 8 subjects (37.5%) and the survival of other mice was significantly prolonged compared to untreated controls (see Table 7). Prolongation of survival in the group treated with DB-DOX (conjugate of Example 28A) is statistically significant and the median survival is 47.5 days versus 29 in the group of untreated mice. The linear conjugate with doxorubicin (PHPMA- DOX) cured only one mouse (12.5%), whereas the free doxorubicin (DOX) cured none. The average tumour growth is shown in Figure 7a, the survival of mice after treatment is shown in Table 7 and Figure 7b.

Table 7: Survival of C57B/6 mice inoculated with murine EL4 lymphoma, treated with micellar diblock conjugate DB-Dox according to Example 28 after i.v. administration of a single dose of 7.5 mg/kg or linear conjugate with doxorubicin (PHPMA-DOX) at the same dose or free doxorubicin (DOX) administered in two doses (2 x 5 mg/kg). Days mean the death of animals after administration of tumour cells (1 x 10 ⁵ cells EL4 s.c. on day 0), LTS ("long term survivor") means long-term surviving mice without evidence of tumour (at least until day 70 after administration of tumour cells). The last line contains information about the median survival in groups.

Administration of DB-DOX (conjugate according to Example 28A) did not induce in the treated mice any observable signs of systemic toxicity (e.g. reduced body weight, bristly hair, hunched position, eating disorders). Without risk of systemic toxicity even higher doses of this drug may be administered. An important feature of treatment with the diblock conjugate according to Example 28A (DB-DOX) is the establishment of a resistance against tumour, which is tumour- specific, long-term and mediated by antitumour immune mechanisms. It was demonstrated by retransplantation of cured mice (LTS) with the same dose of live EL4 tumour cells that was used to induce the disease, but with leaving these mice without any treatment. Resistant individuals after this retransplantation developed no tumour and survive in the long term. Mice cured in the described experiment (LTS) were retransplanted as late as 119 days after administration of the first tumour, and of these three mice two were resistant. The micellar conjugate according to Example 28A (DB-DOX) demonstrated high activity as a delivery system for a cytotoxic drug (doxorubicin) in the treatment of the experimental mouse lymphoma. Example 38: Drug accumulation in solid tumours and time of circulation in the bloodstream

The drug accumulation in solid tumours and time of its circulation in the blood were determined in mice inoculated with T-cell lymphoma EL4. At predetermined time intervals, blood was collected from mice along with tumour samples. These samples were homogenized and analyzed for drug content. The drug content was determined after acid hydrolysis in 1 M HC1 at 50°C when DOX decomposes into aglycone, which is then shaken into an organic solvent immiscible with water and assayed by HPLC (Shimadzu HPLC system equipped with a reverse phase column Chromolith Performance RP-18e (100 x 4.6 mm) and UV-VIS detector Shimadzu SPD-lOAVvp (230 nm); eluent: water- acetonitrile with the gradient of 50-100 vol% of acetonitrile, flow rate 0.5 mL · min ^"1 ).

After administration of the diblock conjugate based on PHPMA-L-PPO with DOX attached via a hydrazone bond (DB-DOX, i.e. the conjugate according to Example 28) 4 times higher amount of drug was determined in the tumour tissue than with the linear PHPMA conjugate (PHPMA-DOX), see Figure 8. It was also found that the accumulation in the tumour tissue is more than 20-fold as compared with the drug accumulation following administration of a free drug at the maximum tolerated dose. Also, in determining the time of circulation in blood it was found that the drug bound to the diblock PHPMA-L-PPO polymer system (conjugate according to Example 28) circulates in the bloodstream considerably longer than in the case of linear PHPMA conjugate (PHPMA- DOX) and the free drug (DOX) (see Fig. 9). Both experiments demonstrated the ability of block PHPMA-PPO-based copolymers to be highly effective delivery systems for pharmaceuticals having significantly better pharmacokinetic parameters.