The BeLimumab Antiphospholipid Syndrome Trial (BLAST)

Inclusion Criteria: • Positive aPL profile defined as: Positive lupus anticoagulant test as defined by the International Society on Thrombosis and Haemostasis, on two or more occasions, at least 12 weeks apart and/or Positive anticardiolipin antibody (aCL) immunoglobulin G(Ig)G/M/A isotype, present in \> 40U, on two or more occasions, at least 12 weeks apart and/or Positive anti-β2-glycoprotein-I (aβ2GPI) IgG/M/A isotype, present in \> 40U, on two or more occasions, at least 12 weeks apart AND • Clinical features attributable to aPL that are resistant to warfarin and/or heparin: * Recurrent thrombosis despite ongoing anticoagulation and/or * Persistent thrombocytopenia and/or * Persistent autoimmune hemolytic anemia and/or * Cardiac valve disease and/or * Chronic skin ulcers and/or * Renal thrombotic microangiopathy and/or * Cognitive dysfunction with/without white matter changes Exclusion Criteria: * \>=4/11 American College of Rheumatology Classification Criteria for SLE * Acute thrombosis (arterial or venous acute thrombosis diagnosis less than 30 days before study screening) * History of stroke Acute or chronic pancreatitis * Pregnancy * Have a history of malignant neoplasm within the last 5 years except basal cell or squamous cell carcinoma of the skin treated with local resection only or carcinoma in situ of the uterine cervix treated locally and with no evidence of metastatic disease for 3 years * Have evidence of serious suicide risk including any history of suicidal behaviour in the last 6 months and/or any suicidal ideation in the last 2 months or who in the investigator's judgment, poses a significant suicide risk * Have a history of a primary immunodeficiency * Have a significant IgG deficiency (IgG level \< 400 mg/dL) * Have an IgA deficiency (IgA level \< 10 mg/dL) * Known active bacterial, viral fungal mycobacterial, or other infection * Infection history: * Currently on any suppressive therapy for a chronic infection (such as tuberculosis, pneumocystis, cytomegalovirus, herpes simplex virus, herpes zoster and atypical mycobacteria) * Hospitalization for treatment of infection within 60 days of Day 0. * Use of parenteral (IV or IM) antibiotics (anti-bacterial, antiviral, anti-fungal, or antiparasitic agents) within 60 days of Day 0 * Have current drug or alcohol abuse or dependence, or a history of drug or alcohol abuse or dependence within 365 days prior to Day 0 * Have a historically positive HIV test or test positive at screening for HIV * Hepatitis status: * Serologic evidence of current or past Hepatitis B (HB) infection based on the results of testing for HBsAg and HBcAb as follows: * Patients positive for HBsAg or HBcAb are excluded * Positive test for Hepatitis C antibody * Have a history of an anaphylactic reaction to parenteral administration of contrast agents, human or murine proteins or monoclonal antibodies * Have any other clinically significant abnormal laboratory value in the opinion of the investigator * If Women of Child-Bearing Potential (WCBP) are included, please see special instructions below. * Have any intercurrent significant medical or psychiatric illness that the investigator considers would make the candidate unsuitable for the study