Study stopped prematurely due to enrolment challenges.

This is a Phase 2, multicenter, double-blind, placebo-controlled, 12-week proof-of-concept study to assess the efficacy, safety, and tolerability of UCB5857 in subjects with primary Sjögren's Syndrome (pSS).

The primary objective of this study is to evaluate the efficacy on overall disease activity and safety of UCB5857 added to current treatment relative to placebo in subjects with pSS.

Inclusion Criteria:

• Subject must be between 18 years and 75 years of age
• Women of childbearing potential must agree to use a highly effective method of birth control during the study and for a period of 3 months after their final dose of study drug. Women not agreeing to use birth control must be of non-childbearing potential defined as; permanently sterile, congenitally sterile or postmenopausal for at least 2 years prior to Screening (Visit 1). Women of childbearing potential are required to have a serum pregnancy test taken at Screening (Visit 1), which is confirmed to be negative by urine testing prior to the first dose of study drug at Week 1 (Visit 2) Male subjects with a partner of childbearing potential must be willing to use a condom when sexually active during the study and for 3 months after the last dose of study drug In addition female partner of childbearing potential of male subject must be willing to use a highly effective method of contraception for duration of study and for 3 months after last dose of study drug
• Subject must meet the 2002 AECG (American-European Consensus Group) criteria for Primary Sjӧgren's Syndrome
• Subject must have a serum test positive for anti-SSA/Ro (Ro-52 or Ro-60) and/or anti SSB/La autoantibodies

Exclusion Criteria:

• Subject has a diagnosis of any other autoimmune disease, ie, secondary Sjögren's syndrome (eg, rheumatoid arthritis, systemic lupus erythematosus

• Subject has a diagnosis of any other sicca syndrome (eg, history of head and neck radiation treatment, sarcoidosis chronic graft-versus-host disease)

• Subject has significant fibromyalgia syndrome as defined by the American College of Rheumatology 2010 classification criteria

• Subject has significant depression as defined by the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders

• Subject has oral candidiasis

• Subject is female and is breast-feeding, pregnant, or plans to become pregnant or to start breastfeeding during the study or within 3 months after the final dose of the investigational medicinal product (IMP)

• Subject has evidence of an immunosuppressive state, including human immunodeficiency virus (HIV) infection, hypogammaglobulinemias, T-cell deficiencies, or human T-cell leukemia virus type 1 (HTLV-1)

  o Positive testing for HIV-1/2 at Screening (Visit 1)

• Subject has a history of chronic infections, including but not limited to concurrent acute or chronic viral hepatitis B (HBV) or hepatitis C (HCV)

  • Positive testing for HBV at Screening (Visit 1)
  • Positive testing for HCV at Screening (Visit 1)

• A subject with a history of a recent serious or life-threatening infection or any current signs or symptoms that may indicate a significant infection at Screening (Visit 1) to randomization, as per the Investigator's clinical judgment is also excluded Subject must have completed any prior anti-infective therapy prior to the first dose of study drug with the exception of anti-infectives taken specifically for the treatment of acne, rosacea, onychomycosis, or vaginal yeast infections; for the prophylaxis of urinary tract infections; or prophylaxis for pre-surgical or pre-procedural reasons (including dental procedures). Note: minocycline may not be used for these purposes

• Subject is at a particularly high risk of significant infection due to their lifestyle and/or occupation

• Subject has received intranasal influenza vaccine within the 8 weeks prior to Screening (Visit 1)

• Subject has significant hematologic abnormalities of hemoglobin <10.0 g/dL, or white blood cell (WBC) <2000 /mm^3, or absolute neutrophil count <1000 /mm^3, or platelets <100,000 /mm^3 at Screening (Visit 1)

• Subject has a history of cancer