The effects of custirsen will be evaluated following administration of a single dose following dose-titration period combined with dexamethasone pretreatment. On days −1 and 7, subjects will undergo a full ECG assessment for 24 hours. On day 1, randomization and assignment to the treatment groups will be performed prior to drug administration. Subjects will remain in the study center throughout the treatment period. All subjects will be discharged at the end of day 8 procedures, 24 hours after the last dose of custirsen has been administered. Subjects in groups 1 and 2 will return for an additional visit on day 9, 10 and 14 (±2 days) (approximately 7 days after the last study drug administration). Subjects in group 3 will not return for a follow-up visits.