Initially, we tested the two hERG/Eag1 blocker astemizole and terfenadine alone and found that both are cytotoxic in all glioblastoma cells to a similar extent (IC50 values for both, astemizole and terfenadine, were in the range of 5–8 μM after 72 h-treatment). This evidence concerns the gene KCNH1 and glioblastoma.