This study will assess the effect of a 24-week withdrawal followed by a 28-week reintroduction of belimumab 10 mg/kg plus standard of care medications in subjects with stable low systemic lupus erythematosus (SLE) disease activity. Rebound phenomenon will be assessed for subjects who have permanently withdrawn from further belimumab treatment.
Inclusion Criteria: * Received a minimun of 6 months therapy with with belimumab 10 mg/kg in their current SLE belimumab continuation study. * Be 18 years of age at the Day 0 visit. * Non-prenant, non-lactating females willing to comply with specific birth control requirements as set forth in the protocol. * Able to provide written informed consent to participate. * Subjects who wish to enroll in the control group and the group taking a 6 month belimumab treatment holiday will need a SELENA SLEDAI score of 3 or less after the minimum of 6 months belimumab therapy, as well as having C3 and C4 complement levels at or above the lower limit of the central laboratory reference range, and are on a stable SLE treatment regimen during the 30 day screening period prior to Day 0. * Subjects who wish to enroll in the long-term discontinuation group have voluntarily withdrawn from their continuation studies. Exclusion Criteria: * Subjects who have developed clinical evidence of significant, unstable or uncontrolled, acute or chronic diseases not due to SLE, or experienced an adverse event (AE) in their belimumab continuation study that could, in the opinion of the principle investigator, put the subject at undue risk. * Subjects who have developed any other medical diseases, laboratory abnormalities, or conditions that, in the opinion of the principle investigator, makes the subject unsuitable for the study.