FIELD : medicine. SUBSTANCE : invention relates to medicine, specifically to oncology, and can be used in the treatment of epithelioid sarcoma and a malignant rhabdoid tumour. Method comprises administering to a subject in need thereof a therapeutically effective amount of an EZH2 inhibitor. EFFECT : use of the invention allows to achieve regression of the tumour due to targeted inhibition of histone methyltransferase. 22 cl, 6 tbl, 16 dwg, 7 ex