**Study Overview:** This study looks at how a drug called tibulizumab helps people with a skin condition named *hidradenitis suppurativa* (HS). HS causes painful lumps under the skin. The study is split into two parts, each lasting 16 weeks. In the first part, some people will get tibulizumab, while others get a placebo (a fake treatment), without knowing which one they receive. In the second part, everyone gets tibulizumab. **Key Points:** - **Study Length:** Total duration is 32 weeks. - **Visits and Treatment:** Participants initially receive either tibulizumab or a placebo, then all receive tibulizumab. - **Eligibility:** Participants must have HS for over six months, with certain characteristics. Some health conditions can disqualify participation. If you have HS and meet the criteria, this study might help improve your skin condition. However, consider the time commitment and medical requirements before enrolling.