Long-Term Safety Evaluation of Bimekizumab in Patients with Moderate to Severe Hidradenitis Suppurativa: A Phase 3, Open-Label, Multicenter Extension Study

The primary objective of this study is to evaluate the **safety** of long-term therapy with bimekizumab in participants with moderate to severe **Hidradenitis Suppurativa** (HS). This is clinically relevant as it aims to ensure that prolonged use of bimekizumab does not result in adverse effects, thereby supporting its potential as a sustainable treatment option for HS, a chronic and often painful skin condition.

Secondary objectives include:

• Evaluating the safety of long-term therapy of bimekizumab using additional safety measures in study participants with moderate to severe HS.
• Assessing the long-term efficacy of bimekizumab dose regimens on Hidradenitis Suppurativa Clinical Response (HiSCR), other HS scores, and other clinical measures of disease activity in study participants with moderate to severe HS.

The clinical trial involves a total of **281 participants** diagnosed with **Hidradenitis Suppurativa**, a chronic skin condition characterized by painful nodules and abscesses. The study population includes both male and female subjects, with an age range corresponding to categories 3 and 4, which typically represent adults and older adults. Participants were selected based on their completion of a prior maintenance treatment period in related studies (HS0003 or HS0004) and their eligibility to continue receiving bimekizumab. The trial does not include a vulnerable population. Participants are expected to adhere to the study protocol, including medication intake and visit schedules. Lifestyle factors such as diet and physical activity are not specified as part of the selection criteria. The study ensures that female participants are not pregnant or breastfeeding and comply with contraceptive guidance if they are of childbearing potential. The trial aims to evaluate the long-term safety of bimekizumab in individuals with moderate to severe Hidradenitis Suppurativa.

The clinical trial is designed as a **Phase 3**, open-label, parallel group, multicenter extension study to evaluate the long-term treatment of **bimekizumab** in participants with moderate to severe **hidradenitis suppurativa**. The primary objective is to assess the safety of long-term therapy with bimekizumab. The trial will monitor the percentage of participants experiencing treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs), as well as those achieving clinical response as measured by Hidradenitis Suppurativa Clinical Response 50 (HiSCR50) and 75 (HiSCR75). The study will also evaluate the absolute change from baseline in the Dermatology Life Quality Index (DLQI) total score.

Participants eligible for this study must have completed the maintenance treatment period through Week 48 in previous studies HS0003 or HS0004, be eligible to receive bimekizumab, and not meet any withdrawal criteria from the feeder study. The trial is expected to last until December 5, 2025, with participant involvement potentially extending up to 188 weeks, depending on the protocol amendments applicable in specific countries such as France and Germany.

The sequence of study visits includes an initial screening visit to confirm eligibility, followed by regular follow-up visits to monitor safety and efficacy outcomes. The end-of-study visit will conclude the participant's involvement, assessing the overall impact of the treatment. Participants may be withdrawn from the study if they experience significant adverse events or fail to adhere to the protocol requirements. The investigational medicinal product, bimekizumab, is administered as a solution for injection via subcutaneous use, with a maximum total dose of 320 mg. The study does not include a pediatric formulation and is not classified as a low-intervention trial.

The clinical trial involves the administration of **bimekizumab**, an experimental medication formulated as a **solution for injection**. Bimekizumab is a protein-based therapeutic agent, specifically classified under "Protein - Other," and is developed by UCB Biopharma SRL. The medication is supplied in a 1mL Type I glass pre-filled syringe, equipped with a staked 27G, ½” thin wall needle. The syringe is sealed with a fluropolymer laminated bromobutyl rubber stopper and a rigid needle shield, ensuring it is pre-assembled and ready for use. The administration route for bimekizumab is **subcutaneous use**, with a maximum total dose of 320 mg. The treatment period extends up to 188 days, with the dosing schedule determined by the study protocol.

In this trial, no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are utilized. The focus is solely on evaluating the long-term safety of bimekizumab in participants with moderate to severe **Hidradenitis Suppurativa**. Participant compliance with the dosing regimen is monitored throughout the study to ensure adherence to the protocol. The trial is designed as an open-label, parallel group, multicenter extension study, emphasizing the collection of safety data over an extended treatment duration.

Efficacy in this clinical trial will be assessed through several secondary endpoints. These include the percentage of participants achieving clinical response as measured by **Hidradenitis Suppurativa Clinical Response 50 (HiSCR50)** and **Hidradenitis Suppurativa Clinical Response 75 (HiSCR75)**. Additionally, the percentage of participants experiencing a flare, as well as responses to the Hidradenitis Suppurativa Symptom Questionnaire (HSSQ) for skin pain, will be evaluated. Another parameter for efficacy assessment is the absolute change from baseline in the Dermatology Life Quality Index (DLQI) total score. These endpoints will provide a comprehensive evaluation of the treatment's impact on the participants' condition and quality of life.