Long-Term Safety and Efficacy of Bimekizumab in Adults with Active Axial Spondyloarthritis: An Open-Label Extension Study

The primary objective of this study is to assess the long-term **safety** and tolerability of **bimekizumab** in patients with active **axial spondyloarthritis**. This is clinically relevant as it aims to ensure that the therapeutic benefits of bimekizumab are sustained over an extended period without compromising patient safety, which is crucial for chronic conditions like axial spondyloarthritis.

Secondary objectives include evaluating the impact of bimekizumab on:

• Long-term efficacy
• Patient-reported outcomes, including health-related quality of life
• Spinal mobility
• Enthesitis and peripheral arthritis

The clinical trial involves a total of **123 participants** diagnosed with **axial spondyloarthritis**, aiming to assess the long-term safety and tolerability of bimekizumab. The study population includes both male and female subjects, with an age range that spans from young adults to middle-aged individuals. Participants were selected based on their completion of previous studies AS0010 or AS0011, and their ability to adhere to the study protocol, as judged by the investigator. The trial does not include a vulnerable population, and no specific lifestyle considerations such as diet or physical activity are highlighted. The selection criteria ensure that participants are reliable and capable of following the study requirements, although specific inclusion or exclusion criteria are not the primary focus of this description.

The clinical trial is designed as a **phase III open-label extension study** to evaluate the long-term safety, tolerability, and efficacy of **bimekizumab** in patients with active **axial spondyloarthritis**, including ankylosing spondylitis and nonradiographic axial spondyloarthritis. The trial is not categorized as low intervention and involves the administration of bimekizumab via **subcutaneous use**. The investigational product is provided as a solution for injection in a pre-filled syringe, ensuring ease of administration. The trial is expected to span from June 29, 2020, to November 27, 2025, with a maximum treatment period of 164 weeks for each participant.

Participants eligible for this study must have completed prior studies AS0010 or AS0011 and be deemed reliable and capable of adhering to the protocol by the investigator. The primary endpoints focus on the incidence of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs), as well as TEAEs leading to withdrawal from the study. Secondary endpoints include assessments of the SpondyloArthritis International Society (ASAS) response criteria, changes in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and other relevant indices at specified weeks throughout the study.

The sequence of study visits includes an initial screening visit to confirm eligibility, followed by regular follow-up visits at intervals such as Weeks 28, 52, and 112, where efficacy and safety assessments will be conducted. The end-of-study visit will conclude the participant's involvement, ensuring all necessary data is collected. Participants are expected to remain in the study for the full duration unless conditions arise that necessitate early termination, such as the occurrence of significant adverse events or withdrawal of consent. The study aims to provide comprehensive data on the long-term use of bimekizumab in the specified patient population.

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". 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, which includes an elastomeric needle cover and a polypropylene Rigid Needle Shield (RNS). Each syringe is pre-assembled and ready for use, ensuring ease of administration. The route of administration for bimekizumab is **subcutaneous use**. The maximum total dose administered is 160 mg, with a treatment period extending up to 164 weeks. The dosing schedule and participant compliance are monitored throughout the study to ensure adherence to the protocol.

In this trial, no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are utilized. The focus remains solely on evaluating the long-term safety, tolerability, and efficacy of bimekizumab in participants with active axial spondyloarthritis, including ankylosing spondylitis and nonradiographic axial spondyloarthritis. The study does not include a pediatric formulation, and bimekizumab is not classified as an orphan drug for this trial. Compliance with the dosing regimen is critical, and participants are monitored to ensure accurate administration of the medication as per the study protocol.

The efficacy of **bimekizumab** in the treatment of active axial spondyloarthritis, including ankylosing spondylitis and nonradiographic axial spondyloarthritis, will be assessed through a series of predefined secondary endpoints. These endpoints include the Assessment of SpondyloArthritis International Society 40% response criteria (ASAS40) and 20% response criteria (ASAS20) at Weeks 28, 52, and 112. Additionally, changes from baseline in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Bath Ankylosing Spondylitis Functional Index (BASFI) will be evaluated at the same timepoints. The study will also measure changes in the Ankylosing Spondylitis Disease Activity Score-C-reactive protein (ASDAS-CRP), the Bath Ankylosing Spondylitis Disease Metrology Index (BASMI), and the Maastricht Ankylosing Spondylitis Enthesitis (MASES) Index.

Patient-reported outcomes will be collected using the Ankylosing Spondylitis Quality of Life (ASQoL) and the Short Form 36-Item Health Survey (SF-36) physical component summary (PCS). The Nocturnal Spinal Pain Numeric Rating Scale (NRS) will also be used to assess changes in nocturnal spinal pain. These assessments will be conducted at Weeks 28, 52, and 112. The efficacy parameters will be measured and analyzed using validated scales and instruments, ensuring the reliability and accuracy of the data collected throughout the trial. The study aims to provide comprehensive insights into the long-term efficacy of bimekizumab in managing symptoms and improving the quality of life for patients with these conditions.