In this study, doctors want to find out how well a medicine called remibrutinib works for adults with a skin condition called hidradenitis suppurativa (HS). HS is a painful skin problem with lumps and bumps. The study lasts up to 76 weeks, which is about a year and a half. There are different parts: a screening (up to 4 weeks), two treatment periods, and a safety check after treatment. Treatment Period 1 lasts 16 weeks, where participants might get remibrutinib or a placebo (a pill that doesn't have medicine in it), and Treatment Period 2 lasts 52 weeks. The safety follow-up lasts 4 weeks.

• The study is for adults aged 18 and up with moderate to severe HS.
• If you have certain health problems or have used similar medicines before, you cannot join.
• Participants should not have more than 20 tunnels or fistulae in their skin at the start.

It's important to stay in the study, even if the treatment is stopped early. This helps doctors learn more about the medicine. Before joining, make sure to talk with a healthcare professional about any concerns or questions you have.