Clinical Study of Efficacy and Safety of BCD-085 (Monoclonal Anti-IL-17 Antibody) in Psoriatic Arthritis

Inclusion Criteria: * Signed informed consent (IC) * History of psoriatic arthritis (According to CASPAR, 2006) for 6 months * 3/68 TJC and 3/66 SJC * RF / ACCP negative * At least 1 psoriatic plaque ≥ 2 cm and/or psoriatic nails and/or history of confirmed plaque psoriasis * History of inadequate response to NSAID * Stable dose of NSAID for 2 weeks * If on steroids: inadequate response to steroids (at least 3 months of treatment) and stable dose of steroids (10 mg or less) for at least 2 weeks. * If on MTX: inadequate response to MTX (stable dose 15 - 25 mg / week for at least 2 months) * In case of history of etanercept therapy: at least 4 weeks after last administration * In case of history of infliximab therapy: at least 8 weeks after last administration * In case of history of adalimumab / golimumab / certolizumab pegol therapy: at least 10 weeks after last administration * In case of history of other mabs / fragments / small molecules : at least 5 half life after last administration * Negative pregnancy test for women with childbearing potential * Ability to follow procedures of the study * Patient and his/her sexual partner with childbearing potential are ready to use reliable contraception, starting at the date of IC sign, within the study period and 4 weeks after the last dose of investigational drug administration. (Not applied to participants/sexual partners who surgically sterilized, and women at menopause for more than 2 years). Reliable contraception considered as 1 barrier method and one of the following: spermicides, oral contraception or intrauterine devices) Exclusion Criteria: * Therapy with anti-IL17 / IL17R or anti-IL12/23 or history of therapy with 2 or more monoclonal antibodies or therapy with topical / oral retinoids or phototherapy or other topical medication for psoriasis history or parenteral steroids administration or any intraarticular injections within 4 weeks prior IC sign or any DMARD therapy (excl. methotrexate) on the dated of IC * Vaccination with live vaccines within 8 weeks prior to IC sign * Diagnosis of any other chronic infection which may increase the risk of infectious adverse events. * HIV, HCV, HBV, Syphilis. * Clinically significant deviations in blood chemistry and blood count * History of Herpes Zoster * History of depression, suicidal ideation/behavior. * Known history of alcohol or drug abuse * Diagnosis or history of tuberculosis * Any acute infection or chronic infection flare within 30 days prior to informed consent sign, which may increase (according to the PI opinion) the risk of infectious adverse events. * Any other documented conditions which increase the risk of AEs development or may interfere with symptoms the disease (masking, increasing or changing) or induce clinical symptoms or laboratory abnormalities similar to PsA: 1. Uncontrolled diabetes mellitus; 2. Severe, uncontrolled hypertension; 3. Presence or history of inflammatory joint disease other than PsA (or any other systemic autoimmune disease (including lupus, Crohn's disease, ulcerative colitis, scleroderma, inflammatory myopathy, mixed connective tissue disease, autoimmune overlap syndrome, fibromyalgia etc.); 4. History of malignancy, excluding cured basal cell carcinoma / cervical cancer in situ (complete remission for 5 years); cured basal cell skin carcinoma (5 years complete remission), cured ductal breast cancer (5 years complete remission); 5. Decompensated liver or kidney diseases; 6. Unstable angina pectoris; 7. Chronic heart failure, class III-IV according to NYHA; 8. Myocardial infarction, within 1 year prior to IC sign; 9. History of organ transplantation; 10. History of Quincke edema; 11. History of any significant respiratory diseases, including COPD, asthma or bronchiectasis; 12. Decompensated respiratory failure; 13. History of multiple sclerosis, 14. Devic's disease, or Guillain-Barre syndrome; 15. Any neurological disease with motor or sensory functions impairment) * Pregnancy, current or planned in less than 8 weeks after study completion or breastfeeding. * Simultaneous participation in other clinical trials or participation in other clinical trials with 3 month prior to IC signing date or history of participation it current clinical study (excluding patients dropped out at screening).