The purpose of the study is to assess the PK of bimekizumab following subcutaneous (sc) administration in study participants with moderate to severe hidradenitis suppurativa (HS)

Inclusion Criteria:

• Study participant must be 12 to <18 years of age at the time of informed consent/assent, at Tanner stage 2 or more, for the first 8 participants only, followed by also including participants ≥9 to <18 years of age at Tanner stage 2 or more.
• Study participant must have a diagnosis of HS for at least 6 months prior to the Baseline Visit.
• Study participant must have moderate to severe HS, defined as a total of ≥5 inflammatory lesions (ie, the sum of abscesses and inflammatory nodules), as assessed at both the Screening and Baseline Visits.
• Study participant must have HS lesions present in at least 2 distinct anatomic areas, 1 of which must be at least Hurley Stage II or III, as assessed at both the Screening and Baseline Visits.
• Study participant must have had a history of inadequate response to a course of a systemic antibiotic for treatment of HS
• Study participant must weigh ≥30kg at the Screening Visit.

Exclusion Criteria:

• Study participant has a draining tunnel count of >20 at either the Screening or Baseline Visits.
• Study participant has experienced primary failure (no response within 12 weeks) to 1 or more IL 17 biologic response modifiers (eg, brodalumab, ixekizumab, secukinumab) OR primary failure to more than 1 biologic response modifier other than an IL-17 biologic response modifier.
• Study participant has previously participated in this study or has received previous therapy with bimekizumab.
• Study participant has a history of IBD or symptoms suggestive of IBD.
• History of active tuberculosis unless successfully treated, latent TB unless prophylactically treated
• Study participant has an active infection or history of infections (such as serious infection, chronic infections, opportunistic infections, unusually severe infections)
• Study participant has received drugs outside the specified timeframes relative to the Baseline Visit or receives prohibited concomitant treatments
• Study participant has the presence of active suicidal ideation, or positive suicide behavior,
• Study participant diagnosed with severe depression in the past 6 months prior to the Screening Visit.
• Study participant has a history of psychiatric inpatient hospitalization within the past year before enrolling into the study.

Data from this trial may be requested by qualified researchers six months after product approval in the US and/or Europe, or global development is discontinued, and 18 months after trial completion. Investigators may request access to anonymized individual patient-level data and redacted trial documents which may include: analysis-ready datasets, study protocol, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a prespecified time, typically 12 months, on a password protected portal. This plan may change if the risk of re-identifying trial participants is determined to be too high after the trial is completed; in this case and to protect participants, individual patient-level data would not be made available.

Data from this trial may be requested by qualified researchers six months after product approval in the US and/or Europe or global development is discontinued, and 18 months after trial completion.

Qualified researchers may request access to anonymized IPD and redacted study documents which may include: raw datasets, analysis-ready datasets, study protocol, blank case report form, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed.All documents are available in English only, for a pre-specified time, typically 12 months, on a password protected portal.