This study is looking at how safe and effective a drug called *deuruxolitinib* is for teenagers with a condition called alopecia areata. *Alopecia areata* is when you lose a lot of hair, and in this study, participants have lost at least half of the hair on their heads. The study has two parts. In the first part, which lasts 24 weeks, teenagers will get either deuruxolitinib or a placebo (a fake pill that doesn't have any medicine). This part is **double-blind**, meaning neither the doctors nor the participants know who is getting the real medicine. In the second part, which lasts 52 weeks, everyone will get the real medicine. People who want to join must be between 12 and 17 years old and have had hair loss for 6 months to 10 years.

• The study lasts a total of 76 weeks.
• Participants will need to visit the study site for tests and check-ups.
• There may be risks, like side effects, but these will be monitored by doctors.