Study to Evaluate the Safety and Efficacy of CTP-543 in Adult Patients With Moderate to Severe Alopecia Areata

This is a double-blind, randomized, placebo-controlled multi-center study consisting of 3
cohorts to assess the safety and efficacy of CTP-543. Each Cohort will be initiated
sequentially in ascending dose order. Subjects will be randomized to either an active dose of
CTP-543 or placebo for a 24-week treatment period.

Inclusion Criteria:

- Definitive diagnosis of alopecia areata with a current episode lasting at least 6
months and not exceeding 10 years at the time of Screening. Total disease duration
greater than 10 years is permitted.

- At least 50% scalp hair loss, as defined by a SALT score ≥50, at Screening and
Baseline.

- Clinical lab results within the normal range

Exclusion Criteria:

- Active scalp inflammation, psoriasis, or seborrheic dermatitis requiring topical
treatment to the scalp, significant trauma to the scalp, or untreated actinic
keratosis on the scalp.

- Treatment with systemic immunosuppressive medications or biologics.

- Vaccination with herpes zoster vaccine or any live virus within 6 weeks of screening
or during the study