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 is selected from the group comprising oligopeptides with two to five amino acids and/or a disulfide bond, 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, 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, where T is oligopeptide attached to the monomer unit via 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; and the hydrophobic block B is formed by a polypropylene oxide; wherein the block A has its molecular weight M n in the range of from 4,000 to 60,000 g/mol, and the block B has its molecular weight M n in the range of from 1,000 to 17,600 g/mol; and wherein the molecular weight of the block copolymer is in the range of from 5,000 to 95,000 g/mol; wherein the block copolymer 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 -NH 2, 2-aminopropyl, dibenzocyclooctyle, and an oligopeptide of two to five amino acids, connected to PPO via an amide bond. and/or a disulfide bond, 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, 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, where T is oligopeptide attached to the monomer unit via 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; and the hydrophobic block B is formed by a polypropylene oxide; wherein the block A has its molecular weight M n in the range of from 4,000 to 60,000 g/mol, and the block B has its molecular weight M n in the range of from 1,000 to 17,600 g/mol; and wherein the molecular weight of the block copolymer is in the range of from 5,000 to 95,000 g/mol; wherein the block copolymer 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 -NH 2, 2-aminopropyl, dibenzocyclooctyle, and an oligopeptide of two to five amino acids, connected to PPO via an amide bond.