Drug-drug Interaction Study of CTP-543 and Oral Contraceptives in Healthy Female Subjects

Inclusion Criteria: * Healthy female participants of non-childbearing potential, or adult females of childbearing potential who agree to use birth control methods described in the protocol * If of reproductive age, willing and able to use a medically highly effective form of birth control 28 days prior to first dose, during the study and for 28 days following last dose of study medication. Examples of medically highly effective forms of birth control are: 1. Surgical sterilization of the partner (via vasectomy, hysterectomy, bilateral tubal ligation or bilateral salpingectomy) at least 4 months prior to first dose or post-menopausal with amenorrhea for at least 1 year prior to the first dosing and follicle-stimulating hormone (FSH) serum levels (\> 40 IU/L) consistent with postmenopausal status 2. Sexual partner is sterile, or of the same sex 3. Double-barrier method (any combination of physical and chemical methods) 4. Non-hormone releasing intrauterine device in females * Continuous non smoker who has not used nicotine containing products for at least 3 months prior to the first dosing and throughout the study * Body mass index (BMI) ≥ 18.0 and ≤ 32.0 kg/m2 * Medically healthy with no clinically significant medical history, physical examination, laboratory tests, vital signs, or ECGs * Understands the study procedures in the informed consent form, and be willing and able to comply with the protocol Exclusion Criteria: * Positive pregnancy test * 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 pose 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 * A positive tuberculosis test at screening or history of incompletely treated or untreated tuberculosis * Positive results at screening for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg) or hepatitis C virus (HCV) * Donation of blood or significant blood loss within 56 days prior to dosing