['long qt syndrome type 3']
['eleclazine', 'eleclazine placebo']

        Key Inclusion Criteria:

          -  Individuals with an established diagnosis of LQT3 (by genotype testing)

          -  Mean (of triplicate) QTc interval ≥ 480 msec (or ≥ 460 msec, for individuals who are
             currently taking ranolazine or Class I antiarrhythmic drugs such as mexiletine) at 3
             or more time points, determined by standard 12-lead ECG, at screening

        Key Exclusion Criteria:

          -  Known mutations associated with type 1 long QT syndrome (LQT1) or type 2 long QT
             syndrome (LQT2)

          -  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) ≥ 40 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.
      