MGMT and glioblastoma: At the time of writing, there are two active clinical trials, a phase II (NCT03581292) and a phase II/III (NCT02152982), that compare conventional therapy with or without veliparib for newly diagnosed GBM patients; different from the previously mentioned clinical trials of this section, NCT02152982 is systematically assessing the levels of O-6-methylguanine-DNA methyltransferase (O-MGMT) enzyme as a biomarker of susceptibility to this PARPi [95] (Table 1).