Study of Efficacy and Safety of Brodalumab Compared With Placebo in Subjects With Axial Spondyloarthritis

Inclusion Criteria: * Subject fulfills the ASAS classification criteria of axial spondyloarthritis (except Crohn's disease criterion) for \> 3 months with age of onset \< 45 years of age * Subject has Bath Ankylosing Spondylitis DIsease Activity Index (BASDAI) score greater than or equal to 4 at screening and baseline * Subject has spinal pain score (BASDAI question #2) greater than or equal to 4 at screening and baseline * Subject has had adequate therapeutic trial (at least 4 weeks) of greater than or equal to 2 non-steroidal anti-inflammatory drgs (NSAIDs) at the maximum recommended dose unless contraindicated or subject is intolerant * For subjects receiving non-biologic DMARDS subject has received treatment for greater than or equal to 3 months with a stable doe for greater than or equal to 4 weeks prior to initiation of IM * For subjects receiving oral corticosteroids: the subject must be on a stable dose (not to exceed the equivalent of 10 mg of prednisone per day) for equal to or greater than 4 weeks prior to initiation of IMP Exclusion Criteria: * Complete ankylosis (fusion) of the spine; Subject has a positive test for tuberculosis * Subject has a planned surgical intervention between baeline and week 16 * Subject has an active infection or history of infections as follows (any active infection for which systemic anti-infectives were used within 28 day prior to the first MP dose * A serious infection, defined as requiring hospitalization or intravenous anti-infectives within 8 weeks prior to the first IMP dose * Recurrent or chronic infections or other active infection that, in the opinion ofthe investigator might cause this study to be detrimental to the subject) * Subject has active Crohn's disease or a history of Crohn's disease * Subject has active ulcerative colitis requiring daily use of immunosuppressive therapy * Subject has had active fibromyalgia within the past 12 months * Subject has a prior history of greater than 1 anti-TNF therapy for ankylosing spondylitis * Subject has used commercially available or investigational biologic therapies for ankylosing spondylitis as follows * Anti-tumor necrosis factor (TNF) therapy as follows: within 1 month prior to IMP initiation for etanercept and within 2 months prior to IMP initiation for other anti-TNF agents. * Other experimental or commercially available biologic therapies for ankylosing spondylitis within 3 months prior to IMP initiation * Anti-IL17 biologics (eg, brodalumab, secukinumab, ixekizumab) or anti-IL12/IL23 biologic therapy (eg, ustekinumab, briakinumab) at any time * Rituximab at any time