This is a four-arm, randomized, crossover, placebo and active controlled study to evaluate of the effect of therapeutic and supratherapeutic doses of CTP-543 on the QT/QTc intervals in healthy volunteers

Inclusion Criteria:

• Healthy, non-smoking, adult males or females aged 18-60
• Body mass index of 18 to 32 mg/m2 at Screening
• Medically healthy with no clinically significant medical history, physical examination, laboratory profiles, vital signs or Electrocardiograms (ECGs)
• If of reproductive age, willing and able to use a medically highly effective form of birth control 30 days prior to first dose, during the study and for 30 days following last dose of study medication
• Understands the study procedures in the informed consent form and be willing and able to comply with the protocol

Exclusion Criteria:

• History or presence of clinically significant medical or psychiatric condition or disease
• History of any illness that might confound the results of the study or poses an additional risk to the subject by their participation in the study
• History or presence of alcohol or drug abuse within the past 2 years prior to the first dosing
• History of prolonged QT syndrome or a Corrected QT-interval (QTc) with Fridericia's correction (QTcF) > 450 msec for males or QTcF > 470 msec for females obtained at Screening visit or prior to the first dosing
• Females who are nursing, pregnant, or planning to become pregnant while in the study, and for 30 days after last dose of study drug
• Positive results at Screening for human immunodeficiency virus, hepatitis B surface antigen or hepatitis C virus
• A positive test or history of incompletely treated or untreated tuberculosis