Single ascending dose administration of four doses of CTP-499 as tablets under fasting condition.

8 subjects per dose group will be enrolled with a 3:1 randomization of active drug to placebo.

Dose levels: 600mg -> 1200mg -> 1800mg -> 2400mg

Part B will consist of a single 400 mg dose of an immediate release capsule of CTP-499 administered under fasting conditions. In Part B 6 subjects will be enrolled.

600 mg, 1200 mg, 1800 mg and 2400 mg

Assessments will include monitoring of adverse events, vital signs (blood pressure, pulse rate, respiratory rate and oral temperature), clinical laboratory findings, 12 lead ECGs, and physical examination findings. Safety data will be summarized using descriptive statistics for all subjects who receive at least 1 dose. Adverse events will be summarized by frequency. Abnormal laboratory and physical exam findings will be summarized by dose and treatment.

Pharmacokinetics: individual and mean concentration time profiles will be presented graphically. Alll PK parameters will be summarized by dose group using descriptive statistics (eg n, arithmetic mean, SD, geometric mean, median, CV). Relative bioavailability will be estimated using the geometric mean values of dose normalized AUC for each dose.

Pharmacodynamics: From the 12 lead ECG data, VR, PR, QRS, QT, QTcF andd QTcB will be reported for each time point and summarized using descriptive statistics. Mean temporal profiles for 12 lead ECG and vital signs will be presented graphically.