Efficacy and Safety of MEthylprednisolone Administered Intravenously for the Treatment of Patients With Active AnkyLosing spondyLitis (METALL)

Inclusion Criteria: * Age of ≥18 years. * Definite diagnosis of AS according to the modified New York criteria. * History of an inadequate response to ≥2 nonsteroidal antiinflammatory drugs (NSAIDs) taken for at least 2 weeks each or NSAIDs intolerance. * Active disease as defined by the Bath Ankylosing Spondylitis DIsease Activity Index (BASDAI) value of ≥4 at screening despite concomitant treatment with an NSAID or without NSAIDs in case of intolerance. Exclusion Criteria: * The female subject is pregnant or lactating. * Patients with other chronic inflammatory articular disease or systemic autoimmune disease. * History of inadequate response to previous anti-tumour necrosis factor (TNF) α therapy. * Treatment with any other investigational drug within 4 weeks of 5 half-life of the drug (whichever is longer) prior to baseline. * Treatments with disease modifying anti-rheumatic drugs (DMARDs) other than methotrexate within 4 weeks prior to screening (8 weeks for leflunomide or 4 weeks with a standard cholestyramine wash-out). * Treatment with intravenous, intramuscular or intraarticular/periarticular steroids within 4 weeks prior to screening. * History of oesophageal, gastric, duodenal or intestinal ulceration, clinically relevant gastrointestinal bleeding. * History of or current signs of coronary heart disease, myocardial infarction, stroke or transient ischemic attack, peripheral arterial thrombotic events. * Congestive heart failure (NYHA III-IV) * Uncontrolled arterial hypertension. * History of diabetes mellitus. * History of glaucoma. * Major surgery within 12 weeks prior to screening. * Evidence of any other severe uncontrolled gastrointestinal, hepatic, renal, pulmonary, cardiovascular, nervous or endocrine disorders. * Any active current viral, bacterial or fungal infection, a history of recurrent clinically significant infection, infections requiring treatment with antibiotics within 4 weeks prior to baseline. * History of chronic infection with hepatitis B or C, history of HIV infection. * Primary or secondary immunodeficiency. * Any other conditions making the patient unsuitable in the opinion of the investigator for the participation in the current study.