This is a single center, Phase 1, open-label, fixed-sequence, drug-drug interaction study to determine the effect of CTP-543 on the pharmacokinetics (PK) of midazolam in healthy adult subjects

Inclusion Criteria:

• Healthy, adult, male or female, aged 18-60
• Non-smoker who has not used nicotine-containing products for at least 3 months prior to the first dosing
• Body mass index (BMI) ≥ 18.0 and ≤ 32.0 kg/m2 at screening
• If of reproductive age, willing and able to use a medically highly effective form of birth control 4 weeks prior to first dose, during the study and for 30 days following last dose of study medication
• Capable of giving informed consent and complying with study procedures

Exclusion Criteria:

• History or presence of clinically significant medical or psychiatric condition or disease
• History or presence of alcohol or drug abuse within the past 2 years prior to the first dosing
• Presence or history of significant gastrointestinal, liver or kidney disease, or any other condition that is known to interfere with drug absorption, distribution, metabolism or excretion, or known to potentiate or predispose to undesired effects
• History of prolonged QT syndrome or a QTc interval with Fridericia's correction (QTcF) > 450 msec for males or QTcF > 470 msec for females at screening visit or prior to the first dosing
• Abnormal liver function at screening
• 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 for coronavirus infection (COVID-19) at screening or check-in
• Positive drug or alcohol results at screening or check-in
• Positive results at screening for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg) or hepatitis C virus (HCV)
• Participation in another clinical study within 30 days prior to, and 30 days after the first dosing.