Treat-to-target With Secukinumab in Axial Spondyloarthritis

Inclusion Criteria: 1. Diagnosis of axial spondyloarthritis (axSpA) according to the ASAS (Assessment of Spondyloarthritis International Society) criteria and/or ankylosing spondylitis (AS) according to the modified New York criteria as judged by a spondyloarthritis (SpA) rheumatologist (regarding imaging in the criteria, see below). 2. Active inflammation on MRI of the SIJs and/or spine as evaluated by a central SpA imaging expert and/or radiographic modified New York criteria fulfilled as judged by a central SpA imaging expert. 3. Active disease defined as ASDAS ≥ 2.1 (ASDAS high disease activity). 4. Total back pain as measured on a visual analogue scale (VAS) scale ≥ 4 0 mm (0-100 mm) at baseline. 5. Clinical indication for a biologic drug as assessed by the treating physician. 6. Patients should have received at least 2 different NSAIDs at the highest recommended dose for at least 2 weeks each with an inadequate response or failure to respond, or less if therapy had to be reduced due to intolerance, toxicity or contraindications. 7. Patients on NSAIDs at inclusion should stay on a stable dose from at least 2 weeks before the baseline MRI scans are performed and to the week 24 visit. 8. Patients on synthetic disease-modifying anti-rheumatic drugs (sDMARDs) at inclusion should stay on a stable dose from at least 4 weeks before initiation of secukinumab to the week 24 visit. 9. Patient must be able to understand and communicate with the investigator and comply with the requirements of the study and must provide written, signed and dated informed consent before any study assessment is performed. 10. Male or female patients at least 18 years and less than 70 years of age. 11. Sufficient contraception for women. 12. Age ≥18 to \<70 years. 13. Capable of giving informed consent. 14. Capable of complying with the examination programme of the protocol. Exclusion Criteria: 1. Contraindications for secukinumab (described in protocol). 2. Contraindication for TNF inhibitor (described in protocol). 3. Contraindication for MRI (described in protocol). 4. Previous exposure to secukinumab or other biologic drug directly targeting interleukin-17 or interleukin-17 receptor. 5. Previous exposure to TNF inhibitor or drug targeting TNF. 6. Previous exposure to other types of biological disease-modifying anti-rheumatic drugs (bDMARDs) than TNF inhibitor. 7. Patients taking high-potency opioid analgesics (e.g. methadone, hydromorphone, morphine) 8. Any change in the dose of oral corticosteroids in the last 8 weeks prior to the baseline visit or use of i.v. intramuscular or intra-articular corticosteroid during the last 8 weeks prior to the enrollment visit. 9. Use of any investigational drug and/or devices within 4 weeks before randomization or a period of 5 half-lives of the investigational drug, whichever is longer. 10. Pregnant or nursing (lactating) women, where pregnancy is defined as the state of a female after conception and until the termination of gestation, confirmed by a positive human chorionic gonadotropin (hCG) laboratory test. 11. Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using effective methods of contraception during the entire study or longer if required by locally approved prescribing information (e.g. 20 weeks in EU). 12. Known recent drug or alcohol abuse. 13. Incapable of complying with the examination programme for physical or mental reasons. 14. Failure to provide written consent