The present invention relates to a method of treating cancer selected from the group consisting of neuroblastoma, Ewing's Sarcoma, or rhabdomyosarcoma comprising administering a therapeutically effective amount of a compound of formula (I), as defined herein, or a pharmaceutically acceptable salt thereof to a subject, preferably a human, in need thereof； to use of the compound of formula (I) or a pharmaceutically acceptable salt thereof for the manufacture of pharmaceutical compositions for use in the treatment of cancer selected from the group consisting of neuroblastoma, Ewing's Sarcoma, or rhabdomyosarcoma； and to use of the compound of formula (I) or a pharmaceutically acceptable salt thereof in the treatment of cancer selected from the group consisting of neuroblastoma, Ewing's Sarcoma, or rhabdomyosarcoma.
