An unbiased high-throughput screen of a cancer drug library of 292 compounds alone and in combination with 10 nM SN-38 was conducted in five GBM cell lines (of which three were unmethylated MGMT, +MGMT, and two were methylated MGMT, −MGMT), using an ATP bioluminescence assay, as previously described [45,46,47]. Here, MGMT is linked to glioblastoma.