Participants initially randomized to placebo with a SALT score ≤ 20 at Week 24 will continue on placebo through Week 160.

Participants will receive upadacitinib Dose A once daily for 52 weeks in Period A and Period B.

Participants will receive upadacitinib Dose B once daily for 52 weeks in Period A and Period B.

Participants will receive matching placebo once daily for 24 weeks in Period A.

Participants initially randomized to placebo (Period A) with a SALT score > 20 at Week 24 will be re-randomized to receive upadacitinib Dose A once daily for 28 weeks in Period B.

Participants initially randomized to placebo (Period A) with a SALT score > 20 at Week 24 will be re-randomized to receive upadacitinib Dose B once daily for 28 weeks in Period B.

Participants initially randomized to placebo with a SALT score ≤ 20 at Week 24 will continue on placebo through Week 160.

Participants receiving upadacitinib Dose A with a SALT score > 20 at Week 52 (end of Period B) of Study 1 or Study 2 will dose escalate to upadacitinib Dose B once daily for 108 weeks.

Participants receiving upadacitinib Dose A with a SALT score ≤ 20 at Week 52 (end of Period B) of Study 1 or Study 2 will remain on upadacitinib Dose A once daily for 108 weeks.

Participants who end Period B on upadacitinib Dose B with a with a SALT score > 20 at Week 40 or Week 52 of Study 1 or Study 2 will remain on upadacitinib Dose B once daily for 108 weeks.

Participants who end Period B on upadacitinib Dose B with a with a SALT score ≤ 20 at Week 40 and Week 52 of Study 1 or Study 2 will be re-randomized to receive upadacitinib Dose B once daily for 108 weeks.

Participants who end Period B on upadacitinib Dose B with a with a SALT score ≤ 20 at Week 40 and Week 52 of Study 1 or Study 2 will be re-randomized to receive upadacitinib Dose A once daily for 108 weeks.

US only adolescent participants will receive upadacitinib Dose A once daily for 52 weeks in Period A and Period B.

US only adolescent participants will receive upadacitinib Dose B once daily for 52 weeks in Period A and Period B.

US only adolescent participants will receive matching placebo once daily for 24 weeks in Period A.

Participants initially randomized to placebo (Period A) with a SALT score > 20 at Week 24 will be re-randomized to receive upadacitinib Dose A once daily for 28 weeks in Period B.

Participants initially randomized to placebo (Period A) with a SALT score > 20 at Week 24 will be re-randomized to receive upadacitinib Dose B once daily for 28 weeks in Period B.

Participants initially randomized to placebo with a SALT score ≤ 20 at Week 24 will continue on placebo through Week 160.

Oral Tablets

The SALT is a global AA severity score based on the combination of extent and density of scalp hair loss. The score is determined by visually defining the amount of terminal hair loss in each of the 4 views of the scalp (left and right side each accounting for 18% of scalp area, the top for 40%, and the back for 24%) and adding these together with a maximum score of 100%.

The SALT is a global AA severity score based on the combination of extent and density of scalp hair loss. The score is determined by visually defining the amount of terminal hair loss in each of the 4 views of the scalp (left and right side each accounting for 18% of scalp area, the top for 40%, and the back for 24%) and adding these together with a maximum score of 100%.

The ClinRO for Eyebrow Hair Loss is a 4-point response scale where 0 = The eyebrows have full coverage and no areas of hair loss and 3 = No notable eyebrows. Responses should have a ≥ 2-point improvement from Baseline among participants with Baseline score ≥ 2.

The ClinRO for Eyelash Hair Loss is a 4-point response scale where 0 = The eyelashes form a continuous line along the eyelids on both eyes and 3 = No notable eyelashes. Responses should have a ≥ 2-point improvement from Baseline among participants with Baseline score ≥ 2.

SALT 75 is defined as at least a 75% improvement [decrease] from Baseline in SALT score.

SALT 90 is defined as at least a 90% improvement [decrease] from Baseline in SALT score.

The SALT is a global AA severity score based on the combination of extent and density of scalp hair loss. The score is determined by visually defining the amount of terminal hair loss in each of the 4 views of the scalp (left and right side each accounting for 18% of scalp area, the top for 40%, and the back for 24%) and adding these together with a maximum score of 100%.

The PaGIC-AA is a single-item measure that asks participants to rate how their alopecia condition has changed overall since the start of the study using a 7-point scale. Responses range from "much better" to "much worse."

The PRO for Scalp Hair Assessment is single item, five-point, categorical response scale that asks respondents to look in the mirror and assess the total area of the scalp with missing hair. Response items range from "No missing hair" to "Nearly all or all" and includes percentage ranges for each category (0%, 1 to 20%, 21 to 49%, 50 to 94%, and 95 to 100%). Responses among participants with baseline score >=3.

The AASIS Interference Subscale is a 6-item assessment with scores ranging from 0 = 'did not interfere' to 10 = 'interfered completely' with higher scores indicating greater symptom interference.

The AASIS Symptom Subscale is a 7-item assessment with scores ranging from 0 = 'not present' to 10 = 'as bad as you can imagine' with higher scores indicating greater symptom severity.

The Skindex-16 AA Emotions Domain is a 7-item assessment ranging from 0 = never bothered to 6 = always bothered that measures the effects of AA on a subject's health-related quality of life. Higher scores indicate greater impact on health-related quality of life.

The Skindex-16 AA Emotions Domain is a 5-item assessment ranging from 0 = never bothered to 6 = always bothered, that measures the effects of AA on a subject's health-related quality of life. Higher scores indicate greater impact on health-related quality of life.

The HADS is a self-administered scale which measures anxiety and depression. It contains 14 items and is comprised of anxiety (7 items) and depression (7 items) subscales, which are scored separately and summed to give a total score. Item scores range from 0 (best) to 3 (worst), and total scores are categorized as normal (0 to 7), borderline abnormal (8 to 10), and abnormal (11 to 21).

The SALT is a global AA severity score based on the combination of extent and density of scalp hair loss. The score is determined by visually defining the amount of terminal hair loss in each of the 4 views of the scalp (left and right side each accounting for 18% of scalp area, the top for 40%, and the back for 24%) and adding these together with a maximum score of 100%.