Study to Evaluate the Effect of Eleclazine on QT, Safety, and Tolerability in Participants With Long QT2 Syndrome

A Double-blind, Placebo-controlled Study to Evaluate the Effect of GS-6615 on QT, Safety and Tolerability in Subjects With Long QT2 Syndrome

The primary objective of the study is to evaluate the effect of oral eleclazine (formerly GS-6615) on corrected QT (QTc) interval in participants with long QT2 syndrome.

Key Inclusion Criteria:

• Participants with an established diagnosis of LQT2 (by genotype testing)
• Mean (of triplicate) QTc interval ≥ 480 msec for at least four out of seven time points, determined by standard 12-lead electrocardiogram (ECG), at screening

Key Exclusion Criteria:

• Known mutations associated with long QT syndrome type 1 or long QT syndrome type 3
• Known or suspected history of seizures or epilepsy
• History of heart failure defined as New York Heart Association (NYHA) Class IV and/or known left ventricular ejection fraction (EF) ≤ 45%
• Body mass index (BMI) ≥ 36 kg/m^2 at screening
• Severe renal impairment at screening (defined as an estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73m^2, using the 4 variable modification of diet in renal disease (MDRD) equation), as determined by the study center
• Abnormal liver function tests at screening, defined as alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 2 x upper limit of normal (ULN), or total bilirubin > 1.5 x ULN
• An aborted cardiac arrest (ACA), implantable cardioverter-defibrillator (ICD) implantation, syncopal episode, or appropriate ICD therapy within 3 months prior to screening
• Any other condition or circumstance that in the opinion of the investigator would preclude compliance with the study protocol.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.