This observational study wants to examine the disease progression independent of relapses in patients with Multiple Sclerosis (MS) that are treated with monoclonal antibodies. Participants will be clinically examined every 6 months and optionally receive a magnetic resonance imaging (MRI) every 12 months. The investigators will also take blood for blood biomarker tests with each clinical examination. Optionally, digital data can be continuously collected via smartphone and smartwatch. With this information the study will compare the results from clinical, digital, radiological, and blood-based tests with the disease progression the participants report themselves. This study aims to investigate what percentage auf patients with MS under antibody treatment experience a slow progression of the disease.