This study is for people with *Hidradenitis Suppurativa* (HS), a painful skin disease that causes bumps in areas like armpits and groin. We want to see if the drug **upadacitinib** can help people who haven't had success with other treatments. This is a **double-blinded** study, which means neither the participants nor the doctors know who gets the actual drug or a **placebo** (a harmless pill that doesn’t contain medicine). Participants will take pills once a day for 36 weeks in the first two study periods, and possibly for 68 weeks more in another period. There will be regular check-ups to see how the treatment is working. The study will involve *1,328 participants* at *275 locations worldwide*. **Key Points:** - You may feel a higher treatment burden compared to usual care. - Regular visits to the clinic are required. - The study lasts around 104 weeks, with follow-ups for about 30 days after. Before joining, note that some people can't participate, especially if they've had recent skin infections or certain treatments. Always check with your doctor to see if this study is right for you.