As PARP1 inhibitors have exhibited promising activity in early clinical trials34, phase I/II trials of PARP inhibitors (olaparib and BMN-673) are currently undergoing investigations in adults with recurrent and metastatic Ewing sarcoma (NCT01583543), and patients with locally advanced or metastatic solid tumours (NCT02049593). Here, PARP1 is linked to Ewing sarcoma.