PARP1 and glioblastoma: The main target of ATM, Chk2, has also been under investigation for the generation of inhibitor molecules, but studies have so far only reached the pre-clinical stage, at least for GBM: PV1019 [43] and CCT241533 [44] were used in combination with IR, bleomycin or the PARP inhibitor olaparib in GBM cell lines.