<br>        Inclusion Criteria:<br><br>          -  Age >=18 years, at the time of signing the informed consent.<br><br>          -  Documented Primary Sjögren's Syndrome by American European Consensus Group criteria<br>             including: either anti-Sjogren's-syndrome-related antigen A (SS-A) or<br>             anti-Sjogren's-syndrome-related antigen B (SS-B) positive.<br><br>          -  Baseline unstimulated salivary flow >0.0 mL/min or evidence of glandular reserve<br>             function (stimulated baseline salivary flow >0.05 mL/min).<br><br>          -  Symptomatic oral dryness (>=5/10 on subject completed numeric response scale).<br><br>          -  Systemically active disease, ESSDAI >=5 points.<br><br>          -  Male and female subjects; females of child bearing potential are eligible if using<br>             effective contraception: Female subject is eligible to participate if she is not<br>             pregnant (as confirmed by a negative urine human chorionic gonadotropin [hCG] test),<br>             not lactating, and at least one of the following conditions applies:<br><br>               1. Non-reproductive potential defined as: Pre-menopausal females with one of the<br>                  following: Documented tubal ligation, Documented hysteroscopic tubal occlusion<br>                  procedure with follow-up confirmation of bilateral tubal occlusion, Hysterectomy,<br>                  Documented Bilateral Oophorectomy.<br><br>                  Postmenopausal defined as 12 months of spontaneous amenorrhea (in questionable<br>                  cases a blood sample with simultaneous follicle stimulating hormone [FSH] and<br>                  estradiol levels consistent with menopause). Females on hormone replacement<br>                  therapy (HRT) and whose menopausal status is in doubt will be required to use one<br>                  of the highly effective contraception methods if they wish to continue their HRT<br>                  during the study; otherwise, they must discontinue HRT to allow confirmation of<br>                  post-menopausal status prior to study enrolment.<br><br>               2. Reproductive potential and agrees to follow one of the options in the<br>                  GlaxoSmithKline (GSK) Modified List of Highly Effective Methods for Avoiding<br>                  Pregnancy in Females of Reproductive Potential (FRP) requirements from 30 days<br>                  prior to the first dose of study medication up to Week 68 after Day 0.<br><br>          -  Ability to understand and comply with the protocol-required procedures and provision<br>             of informed consent.<br><br>        Exclusion Criteria:<br><br>          -  Diagnosis of secondary Sjögren's syndrome.<br><br>          -  Active life-threatening or organ-threatening complications of Sjogren's-syndrome (SS)<br>             disease at the time of screening based on treating physician evaluation including but<br>             not restricted to (1) vasculitis with renal, digestive, cardiac, pulmonary or central<br>             nervous system (CNS) involvement characterized as severe, (2) active CNS or peripheral<br>             nervous system (PNS) involvement requiring high dose steroids, (3) severe renal<br>             involvement defined by objective measures, (4) lymphoma.<br><br>          -  History of major organ transplant (including hematopoietic stem cell transplant).<br><br>          -  History of malignancy within past 5 years (with the exception of adequately treated:<br>             [1] cervical carcinoma Stage 1B or less, [2] non-invasive basal cell and squamous cell<br>             skin carcinoma).<br><br>          -  History of infection requiring long term systemic therapy including: (1) history of<br>             positive human immunodeficiency virus (HIV) serology, (2) positive serology for<br>             Hepatitis C virus (HCV), (3) positive serology for Hepatitis B (HB), defined as: HB<br>             surface antigen positive (HBsAg+) OR HB core antibody positive (HBcAb+).<br><br>          -  Previous serious opportunistic or atypical infections or hospitalization for treatment<br>             of infection within 364 days of Day 0 or use of parenteral (intravenous [IV] or<br>             intramuscular [IM]) antibacterials, antivirals, anti-fungals, or anti-parasitic agents<br>             within 364 days of prior to Day 0.<br><br>          -  Patients in a severely immunocompromised state.<br><br>          -  History of an anaphylactic reaction to parenteral administration of contrast agents,<br>             human or murine proteins or monoclonal antibodies.<br><br>          -  History of significant medical illness (or planned surgical procedure) which in the<br>             opinion of the investigator would interfere with the study procedures and / or<br>             assessments - including but not limited to immunoglobulin G4 (IgG4) disease or prior<br>             head or neck irradiation.<br><br>          -  Severe heart failure (New York Heart Association, Class IV) or other severe,<br>             uncontrolled cardiac disease.<br><br>          -  Tuberculosis (TB), defined as: prior history of TB infection; suspicion of TB<br>             infection or current TB infection<br><br>          -  At risk of suicide, as indicated by a lifetime history of attempted suicide or<br>             significant suicidal ideation over the 6 months prior to the screening visit; or, if<br>             in the Investigator's judgment, the subject is at risk for a suicide attempt.<br><br>          -  Neurological findings consistent with Progressive Multifocal Leukoencephalopathy (PML)<br>             - not otherwise explained - or confirmed PML.<br><br>          -  Electrocardiogram (ECG) showing a clinically significant abnormality at Screening or<br>             showing an average corrected QT using Bazett's formula (QTcB) or corrected QT using<br>             Fridericia's formula (QTcF) interval >=450 milliseconds (msec) (>=480 msec for<br>             subjects with a Bundle Branch Block) over 3 consecutive ECGs.<br><br>          -  Alanine aminotransferase (ALT) >2x upper limit of normal (ULN) and bilirubin >1.5xULN<br>             (isolated bilirubin >1.5xULN is acceptable if bilirubin is fractionated and direct<br>             bilirubin <35%).<br><br>          -  Current or chronic history of liver disease, or known hepatic or biliary abnormalities<br>             (with the exception of Gilbert's syndrome or asymptomatic gallstones)<br><br>          -  Use of systemic immunosuppressive or immunomodulatory agents including methotrexate,<br>             azathioprine, leflunomide, mycophenolate (including mycophenolate mofetil,<br>             mycophenolate mofetil hydrochloride, and mycophenolate sodium), mizoribine,<br>             calcineurin inhibitors [e.g., tacrolimus, cyclosporine], sirolimus, 6-mercaptopurine,<br>             or thalidomide within 60 days prior to Day 0.<br><br>          -  Have received cyclophosphamide within 180 days prior to Day 0.<br><br>          -  Have received anti- B lymphocyte stimulator (BLyS), anti-CD 20, anti-CD22 or anti-CD52<br>             or any other B-cell depleting agent within 364 days prior to Day 0.<br><br>          -  Have received abatacept or any biologic agent within 180 day prior to Day 0 (with<br>             exception of denosumab).<br><br>          -  Have received intravenous immunoglobulin (IVIG) or plasmapheresis within 90 days prior<br>             to Day 0.<br><br>          -  Have received oral steroid >10 milligram (mg) prednisone equivalent/day within 30 days<br>             prior to Day 0 or oral steroid >20 mg prednisone equivalent / day for a minimum of two<br>             consecutive weeks within 60 days prior to Day 0. Have received