For example, telomerase inhibitors that target the telomerase RNA template TERC, such as imetelstat, showed promise in preclinical studies, including in GBM, but failed in clinical trials in part owing to “on-target” toxicity in normal stem cells with TERC and TERT expression (Marian et al., 2010; Chiappori et al., 2015; Kozloff et al., 2010). Here, TERT is linked to glioblastoma.