This is a Phase 1, randomized, single-center, clinical study of SQ109 to evaluate the potential for this drug to produce QTc prolongation. The study population is healthy male and female subjects, aged 18-45 years. Pharmacokinetics of SQ109 will be measured using interval plasma samples.The overall study design will incorporate within it a four-period investigation suitable for the QT evaluation of an active study treatment. The primary goal of the sample size considerations will be to ensure that the sample size employed during this phase of the study will be adequate to ensure a high likelihood of a successful demonstration of the QT safety of 300 and 450 mg/day SQ109. All subjects will be randomized to a sequence of three seven-day dosing periods, with each dosing period occurring once per subject. The final seven-day dosing period will occur after the first sequence of three dosing periods is completed. A washout period of at least seven days will occur between all dosing periods, and a follow-up visit will occur.