A Study of Baricitinib (LY3009104) in Adults With Severe or Very Severe Alopecia Areata

Inclusion Criteria: * Are at least 18 years and ≤60 years for males (≤70 years of age for females) at the time of informed consent. * Have severe or very severe AA, as determined by all of the following: * Current AA episode of more than 6 months' duration and hair loss encompassing ≥50% of the scalp, as measured by SALT (AA-IGA of 3 or 4) at screening and baseline. * No spontaneous improvement over the past 6 months. * Current episode of severe or very severe AA of less than 8 years. Note: participants who have severe or very severe AA for ≥8 years may be enrolled if episodes of regrowth, spontaneous or under treatment, have been observed on the affected areas over the past 8 years. * Male or nonpregnant, nonbreastfeeding female participants. Exclusion Criteria: * Primarily "diffuse" type of AA. * Are currently experiencing other forms of alopecia or any other concomitant conditions that would interfere with evaluations of the effect of study medication on AA. * Previously treated with an oral Janus kinase (JAK) inhibitor and had an inadequate response (for example, absence of significant terminal hair growth after at least 12 weeks of treatment).