Inclusion Criteria:  Have completed 24 weeks of treatment in a previous qualifying CTP-543 clinical trial  Exclusion Criteria:  Active scalp inflammation, psoriasis, or seborrheic dermatitis requiring topical treatment to the scalp, significant trauma to the scalp, or untreated actinic keratosis Females who are nursing, pregnant, or planning to become pregnant while in the study, and for 30 days after last dose of study medication Donation of blood at any point throughout the study and for 30 days after last dose of study medication