BCD-085-5 is an International, Multicenter, Randomized, Double-blind, Placebo-controlled Clinical Study of the Efficacy and Safety of BCD-085. BCD-085 is a monoclonal antibody to interleukin 17. During BCD-085-5 trial patients with active ankylosing spondylitis will receive 120 mg of BCD-085 subcutaneously every other week or placebo up to Week 16. Starting from week 16 all patients will receive BCD-085. Efficacy, PK and safety parameters will be evaluated.

Inclusion Criteria:

• Active ankylosing spondylitis according to modified criteria of New York classification (1984), that was diagnosed at least 3 months prior to screening.
• Active disease according to BASDAI (score 4 or more) if nonsteroidal antiinflammatory drugs were used in the last 3 month prior to screening.
• Mean backache intensity equals 4 points or more.

Exclusion Criteria:

• Total spinal ankylosis.
• Previous treatment with anti-interleukin 17 drugs or anti-interleukin 17 receptor drugs.
• Prior use of >2 biologics to tumor necrosis factor alfa.
• Prior use of live or attenuated vaccines for up to 8 weeks before signing informed consent.
• Prior use of alkylating agents for up to 12 months prior to signing informed consent.