This study is for teens aged 12 to 18 with a condition called alopecia areata, which causes people to lose hair, often from their scalp. The study tests a drug called deuruxolitinib to see if it's safe and works well for treating hair loss. It has two parts: the first lasts 24 weeks with some teens getting the drug and others a placebo, which is a fake treatment. After that, everyone can get the real drug for 52 weeks. To join, you need to have lost at least 50% of your scalp hair and be willing to follow all study rules.

• Study Length: Total of 76 weeks (24 weeks plus 52 weeks).
• Visits Needed: Regular visits to the study site for check-ups and treatment.
• Risks & Requirements: No other hair treatments allowed during the study; some participants only receive a placebo initially.