This is a study to evaluate the pharmacokinetic (PK) and safety of sonelokimab in adolescent patients with HS.

Inclusion Criteria:

1. Participants must be between ≥12 and ≤17 years of age at the time of signing the informed consent.
2. Participants who are diagnosed with HS as determined by the investigator and have a history of signs and symptoms of HS for ≥6 months before signing the informed consent.
3. Participants who have moderate to severe HS as determined by the refined Hurley staging (Stages IB and IC, IIB and IIC, and III).
4. Participants who have had an inadequate response to appropriate systemic antibiotics for treatment of HS .
5. Participants must be up to date with age-appropriate vaccine requirements 8 weeks prior to entry in the study.
6. Participants with a body weight of ≥ 40 kg.

Exclusion Criteria:

1. Participants with a known hypersensitivity to sonelokimab or any of its excipients.
2. Participants with a draining fistula count of ≥20 at the Screening Visit.
3. Participants with any other active skin disease or condition that may, in the opinion of the investigator, interfere with the assessment of HS.
4. Participants with underlying conditions that, in the opinion of the investigator, potentially compromise the participant and/or places the participant at unacceptable risk.
5. Participants who have history or concurrent clinically significant medical conditions or any other reason, including any physical, psychological, or psychiatric condition, that in the opinion of the investigator would compromise the safety or interfere with participation in the study, would make the participant an unsuitable candidate to receive study drug, or would put the participant at risk.
6. Participants with any other skin disease or other medical condition that in the opinion of the investigator would interfere with an accurate assessment of clinical symptoms of HS.
7. Participants with a confirmed or suspected diagnosis of inflammatory bowel disease.