FIELD : medicine; pharmaceuticals.SUBSTANCE : presented group of inventions refers to pharmaceutical industry, namely to an agent for treating cancer. Pharmaceutical composition for treating cancer, comprising : micronized particles of compound A and/or micronized particles of at least one pharmaceutically acceptable salt of compound A and at least one pharmaceutically acceptable excipient, wherein said micronised particles of compound A and/or micronized particles of at least one pharmaceutically acceptable salt of compound A have particle size distribution (PSD) D90 of less than or equal to 20 mcm, wherein said compound A is N-(2-(dimethylamino)ethyl)-1-(3-((4-((2-methyl-1H-indol-5-yl)oxy)pyrimidin-2-yl)amino)phenyl)methanesulphonamide, presented by formula (embodiments).Use of the pharmaceutical composition for preparing a drug for treating cancer. Micronized particles of compound A and/or micronized particles of at least one pharmaceutically acceptable salt of compound A (embodiments). Use of micronized particles of compound A for preparing a drug for treating cancer. Method of treating a subject for which the need to treat cancer is recognized, comprising administering to an individual in need thereof an effective amount of a pharmaceutical composition or micronized particles of compound A.EFFECT : compositions described above and micronized particles of compound A are characterized by high AUC value in the dosage form, low toxicity, using them reducing cases of vomiting in treating cancer diseases.26 cl, 8 dwg, 12 tbl, 4 ex