The overall objectives of the study are to evaluate long-term safety of CTP-543 and to assess long-term effects of CTP-543 on treating hair loss in adult patients with chronic, moderate to severe alopecia areata.

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