Evaluation of the proarrhythmic potential of imetelstat, a novel oligonucleotide telomerase inhibitor, in nonclinical and clinical studies is presented. In vitro, imetelstat sodium ≤ 750 μg/mL and negative (vehicle) and positive (cisapride) controls were evaluated for hERG channel current inhibition. In vivo, cynomolgus monkeys received a single vehicle control or imetelstat sodium (5 mg/kg [2-h infusion], 10 mg/kg [6-h infusion], or 15 mg/kg [6- or 24-h infusion])
cardiovascular parameters were collected before and after drug administration. A ventricular repolarization substudy of the IMerge phase III study evaluated patients with lower-risk myelodysplastic syndromes administered imetelstat 7.1 mg/kg active dose every 4 weeks
intensive electrocardiograms and pharmacokinetic samples were collected for concentration-QTc and by-time point analyses after a single dose. In vitro, imetelstat did not inhibit the hERG channel (IC