Bimekizumab is a medication used in this clinical trial to help people with certain types of arthritis, specifically axial spondyloarthritis, ankylosing spondylitis, and nonradiographic axial spondyloarthritis. These conditions cause inflammation in the spine and other joints, leading to pain and stiffness. Bimekizumab works by blocking specific proteins in the body that are involved in the inflammation process. By doing this, it aims to reduce the symptoms of these conditions, such as pain and swelling, and improve the overall quality of life for patients. The trial is focused on understanding how safe and tolerable this medication is when used over a long period.

Axial Spondyloarthritis – Axial Spondyloarthritis is a chronic inflammatory disease primarily affecting the spine and the sacroiliac joints, which connect the lower spine to the pelvis. It is characterized by inflammation that can lead to pain and stiffness, particularly in the lower back and buttocks. Over time, the inflammation may cause new bone formation, leading to the fusion of the vertebrae, which can reduce flexibility and mobility. The disease often begins in early adulthood and can progress slowly, with periods of increased symptoms and periods of remission. In some cases, it may also affect other joints and organs, such as the eyes and skin. The progression and severity of symptoms can vary widely among individuals.