FIELD : medicine.SUBSTANCE : group of inventions refers to oncology, and can be used for treatment of triple negative breast cancer. Methods of the invention involve administering a drug delivery molecule (triple negative mammary cancer) containing a polypeptide which contains the areeregulin-α receptor-binding domain, segment of penton base and positively charged domain; and a nucleic acid molecule bound to the polypeptide by electrostatic interactions, and a chemotherapeutic agent, noncovalently bonded to the nucleic acid molecule, or a molecule for drug delivery containing a polypeptide, which contains a areeregulin-α receptor-binding domain, a segment of the penton base and a positively charged domain, and corrosion associated with the polypeptide.EFFECT : use of the inventions enables treating triple negative mammary cancer by associating the polypeptide with the HER3 receptor, which is expressed on the cell surface, and internalising the polypeptide with the chemotherapeutic agent or correl associated therewith.90 cl, 1 tbl, 43 dwg, 29 ex