This mechanism of action study is to evaluate the effect of oral GS-6615 on the QTc interval in participants with Long QT-3 syndrome. This study will be performed in six cohorts of participants in a sequential manner, four single-dose cohorts followed by two multiple-dose cohorts. Duration of treatment for the single-dose cohorts and multiple-dose cohorts will be 1 day and 7 days, respectively. Participants will be confined at the study center from check-in until completion of assessments at discharge. Participants will be continuously monitored using real-time telemetry throughout the in-clinic confinement. Physical examinations including vital signs, laboratory analysis, electrocardiograms (ECGs), Holter recordings and echocardiography (ECHO) will be performed at defined time points throughout the study period. Assessment of adverse events and concomitant medications will continue throughout the duration of the study.

NCT01849003

Conditions

1. Long QT Syndrome

Interventions

1. Drug: GS-6615

MeSH:Long QT Syndrome Syndrome

Inclusion Criteria: 1. Males and females between ages 18-65 years (inclusive) at time of screening 2. Documented LQT-3 genotype with one of the following mutations: delta KPQ, R1623Q, N1325S, E1784K, S1787N, D1790G, G1631D, 1795insD, delF1617, R1644H, L409P, F2004L, I1768V, T1304M, A1330T, or F1596I3. --- R1623Q ---

Psychosocial or addictive disorders that would interfere with ability to give informed consent or could compromise compliance with the protocol Inclusion Criteria: 1. Males and females between ages 18-65 years (inclusive) at time of screening 2. Documented LQT-3 genotype with one of the following mutations: delta KPQ, R1623Q, N1325S, E1784K, S1787N, D1790G, G1631D, 1795insD, delF1617, R1644H, L409P, F2004L, I1768V, T1304M, A1330T, or F1596I3. --- R1623Q ---