Percentage of subjects with a ≥ 4 point reduction from baseline in SELENA SLEDAI score, and no worsening (increase of \< 0.30 points from baseline) in PGA, and no new BILAG A organ domain score or 2 new BILAG B organ domain scores compared with baseline. SELENA SLEDAI is calculated from 24 individual descriptors; 0 indicates inactive disease and the maximum theoretical score is 105; scores \> 20 are rare. PGA is a visual analog scale scored from 0 to 3 (1=mild, 2=moderate, 3=severe). BILAG uses a single score for each of the 8 organ domains; range is from severe to no disease (A to E).

Percentage of participants with a state of disease control (Independent blinded assessor \[IBA\]) was defined as the percentage of participants with a Systemic Lupus Erythematosus Disease Activity Index 2000(SLEDAI-2K)score less than or equal to(\<=)2 achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of \<=5 mg/day at Week 52. SLEDAI-2K was a weighted, cumulative index for measuring systemic lupus erythematosus (SLE) disease activity in previous 10 days,consisting 24 individual items in which signs and symptoms, laboratory tests and physician's assessment for each item within each of 9 organ systems were given a weighted score(1 to 8 with higher score indicating increased activity)and summed if present at the time of visit or in preceding 10 days. The SLEDAI-2K score was sum of all 24 individual items from the SLEDAI-2K, ranges from 0(no symptoms) to 105(presence of all defined symptoms) with higher scores representing increased disease activity.

SFI Flare was defined as a mild/moderate or severe flare according to the modified Safety of Estrogen in Lupus National Assessment Systemic Lupus Erythematosus Disease Activity Index (SELENA SLEDAI) SLE Flare Index (modified excluded severe flares from the SELENA SLEDAI flare assessment that were triggered only by an increase in SELENA SLEDAI score to \>12).Time to first SFI flare is defined as the number of days from Day 0 visit date to the date the participant has a flare (event date - Day 0 visit date + 1) in the 52 Week/Holiday phase; (event date - treatment re-start date + 1) in the Re-start Holiday phase. Day 0 visit date is defined as Day 0 from present study. Median time to first SFI flare is reported; estimated using the product-limit method.

Any untoward medical occurrence in participant, temporally associated with use of medicinal product, whether or not considered related to medicinal product. Any untoward event resulting in death,life threatening,requires hospitalization or prolongation of existing hospitalization,results in disability/incapacity,congenital anomaly/birth defect,medically important were categorized as SAE. Number of participants who had any AE(includes those having non-serious and/or serious AEs) or any SAE are presented.Treatment-emergent AEs are defined as AEs that started on or after first dose of belimumab treatment and for those participants who were randomized to placebo in parent study,ongoing AEs that started before first open-label belimumab dose(in either C1115 open-label extension or BEL114333),worsened (severity,seriousness,relatedness) at any point during the open-label treatment.Timeframe includes exposure in parent study/upto16 weeks post infusion in current study(114333).

SRI response is defined as \>=4 point reduction, from Baseline in safety of estrogen in lupus national assessment (SELENA) systemic lupus erythematosus disease activity index (SLEDAI) score, no worsening (increase of \<0.30 points from Baseline) in physician's global assessment (PGA) and no new British Isles Lupus Assessment Group of SLE clinics (BILAG) A organ domain score or 2 new BILAG B organ domain scores compared with Baseline. Analysis was performed using a logistic regression model for the comparison between belimumab and placebo with covariates treatment group, Baseline SELENA SLEDAI score (\<=9 vs. \>=10), Baseline complement levels (low C3 and/or C4 vs. no low C3 or C4) and race (black vs. other).

SRI response is a composite index, defined as the percent of participants with \>=4 point reduction from Baseline in safety of estrogen in lupus national assessment (SELENA) systemic lupus erythematosus disease activity index (SLEDAI) score and no worsening (increase of \< 0.30 points from Baseline) in physicians global assessment (PGA) and no new British isles lupus assessment group (BILAG) A organ domain score or 2 new BILAG B organ domain scores compared with Baseline at the time of assessment (at Week 52 of the blinded period). A SELENA SLEDAI score of 0 would suggest no lupus activity; while a score of 105 is the maximum calculable if all items were scored as being present from active lupus. PGA ranges from 0 (no activity) to 3 (severe activity). BILAG has no range. The higher thresholds of SELENA SLEDAI improvement (i.e., SRI5, SRI6, and SRI7) indicates a higher response (SRI5 is a 5 point SELENA SLEDAI reduction, SRI6 is a 6 point reduction, and SRI7 is a 7 point reduction).

An AE is defined as any untoward medical occurrence in a participant (par.) temporally associated with the use of a investigational product (IP), whether or not considered related to the IP. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of an IP. An SAE is defined as any untoward medical occurrence that, at any dose, results in death, is life threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, is a congenital anomaly/birth defect, is an important medical event that jeopardizes the participant or may require medical or surgical intervention to prevent one of the other outcomes listed in the above definition, or is associated with liver injury and impaired liver function. Only those participants available at the specified time points (represented by n=X, in the category titles) were analyzed.

AE rates by SOC adjusting for participant-years on study drug anytime post Baseline are summarized, which included the follow up visits. Only treatment-emergent adverse events (AEs) are summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. The event rate of an AE was calculated as the number of events per 100 participant years: Event Rate = 100\* Number of Events / Participant Years. Participant years were calculated as sum across all participants (\[last visit of interval day - first visit of interval day + 1\]/365). Participant years excluded between study gaps if participant had not started extension study on date of last visit of parent study.

SAE rates by SOC adjusting for participants-years on study drug anytime post Baseline are summarized, which included the follow up visits. Only treatment-emergent SAEs are summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. The event rate of an SAE was calculated as the number of events per 100 participant years: Event Rate = 100\* Number of Events / participants Years. participants years were calculated as = sum across all participants (\[last visit of interval day - first visit of interval day + 1\]/365). participants years excluded between study gaps if participant had not started extension study on date of last visit of parent study.

Hematology parameters were assessed at Baseline (BL) (Day 0), Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in APTT and PT is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Hematology parameters were assessed at Baseline (BL) (Day 0), Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in basophils, eosinophils, lymphocytes, monocytes, neutrophils, neutrophils segmented and platelets is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Hematology parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in erythrocytes is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Hematology parameters were assessed at Baseline (BL) (Day 0), Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in hematocrit is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Hematology parameters were assessed at Baseline (BL) (Day 0), Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in hemoglobin is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Clinical chemistry parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in albumin and protein is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Clinical chemistry parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in blood urea nitrogen, glucose, calcium, carbon dioxide, chloride, magnesium, phosphate, potassium and sodium is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Clinical chemistry parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in urate, creatinine and bilirubin is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Clinical chemistry parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in creatinine clearance is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Clinical chemistry parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Change from Baseline in BUN/creatinine is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Clinical chemistry parameters were assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 432 weeks and at exit visit. Change from Baseline in alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, gamma glutamyl transferase and lactate dehydrogenase is summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post- Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Immunogenic response was assessed by binding confirmatory assay at Baseline (BL) (Day 0), at Week 24 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Number of participants with the indicated immunogenic response are summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Results of binding confirmatory assay were categorized as negative, persistent positive (defined as a positive immunogenic response that occurs at least 2 consecutive assessments or a single result at the final assessment) or transient positive (defined as a single positive immunogenic response that does not occur at the final assessment). Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Systolic blood pressure (SBP) and diastolic blood pressure (DBP) was measured at Baseline (BL) (Day 0), at Week 24 and 48 in first year, at Week 24 and 48 in subsequent years up to 432 weeks and at exit visit. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Serum creatinine was assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Percentage of participants with at least 25% increase from baseline in creatinine are summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Serum creatinine was assessed at Baseline (BL) (Day 0), at Week 4, 12, 24, 36 and 48 in first year, at Week 24 and 48 in subsequent years up to 440 weeks and at follow-up (up to 8 weeks post last infusion). Percentage of participants with at least 25% reduction from baseline in creatinine are summarized. The Baseline is defined as the Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

An adverse event is defined as any unfavorable or unintended sign, symptom, or disease that is temporally associated with the use of a study agent but is not necessarily caused by the study agent. This includes worsening (example: increase in frequency or severity) of preexisting conditions. Participants with incidences of any event at any time post-baseline are presented by yearly interval. Only treatment-emergent AEs are summarized.

An adverse event resulting in death, is life threatening (ie, an immediate threat to life), inpatient hospitalization, prolongation of existing hospitalization, persistent or significant disability/incapacity, congenital anomaly/birth defect or any other situation which is medically important is categorized as SAE. Only treatment-emergent AEs are summarized.

SAE rates by SOC adjusting for participants-years on study drug anytime post Baseline are summarized, which included the follow up visits. Only treatment-emergent SAEs are summarized. The event rate of an SAE was calculated as the number of events per 100 participant years. Participants years were calculated as = sum across all participants (\[last visit of interval day - first visit of interval day + 1\] divided by 365). Participants years excluded between study gaps if participant had not started extension study on date of last visit of parent study.

Hematology parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 hematology parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Plt, Lymp, Leu, Eos, Baso, Mono, Neu, NeuBF, and NueS are summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Hematology parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 hematology parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Hg is summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Hematology parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 hematology parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Erythrocytes is summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Electrolytes parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 electrolytes parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Ca,CO2, Chloride, Mg, Phos, K and Na were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Other chemistries parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 other chemistries parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in BUN/Cr is summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Other chemistries parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 other chemistries parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Alb and Protein were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Other chemistries parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 other chemistries were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in BUN and Glucose were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Other chemistries parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 other chemistries were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Cr and Urate were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Liver function parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 liver function parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in ALT, ALP, AST, GGT and LDH were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.NA indicates standard deviation was not calculable for a single data point.

Liver function parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 liver function parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Bili were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Immunoglobulin (Ig) parameters were assessed at Baseline, Week 4,12,24,36, and 48 during Year 1. From Year 2-9 Ig parameters were assessed at Week 24 and 48 ; Exit visit and at follow-up (up to 8 weeks post infusion). Change from Baseline in Ig G were summarized. The Baseline is defined as For Year 1, Day 0 values for MITT participants who were treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants who were treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed. NA indicates standard deviation was not calculable for a single data point.

Immunogenic response was analyzed using serum samples for anti-belimumab antibody measurements in MITT population. Categories of response are Negative, Transient Positive (+) means single + response that does not occur at the final assessment, and Persistent + means + response that occurs at least 2 consecutive assessments or a single result at the final assessment. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Blood samples were collected to evaluate IgG levels at Baseline and at Weeks 12, 24 and 48 during Year 1. From Year 2-9, IgG was evaluated at Week 24 and 48 ; Exit visit and at follow-up visit (up to 8 weeks post last infusion). Number of participants with IgG immunoglobulin values below the LLN at each one year interval are presented. Baseline includes Extension Year 1 Day 0 values for MITT participants treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants treated with Belimumab in the parent study. If a participant had more than one response within a year, then the last response within the year interval (usually the Week 48 assessment) was summarized. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Participants who had improving SLE disease activity for at least 8 weeks, at the investigator's discretion, the steroid dose was reduced by reduction to 7.5 mg/day. If the participant continued to have stable or improving disease activity after 4 weeks on a reduced dose, then the investigator considered reducing the dose again. Baseline includes extension Year 1 Day 0 values for MITT participants treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants treated with Belimumab in the parent study. Number of participants with shifts from Baseline total daily dose category by visit is summarized.

The SLICC/ACR Damage Index was assessed every 48 weeks and at the exit visit as a measure of disease activity. It was developed to assess the accumulated damage since the onset of the disease. The number of participants with worsening in their SLICC/ACR Damage Index score compared with Baseline have been presented. Worsening was defined as a change in score (post-Baseline visit score - Baseline score) \> 0. Baseline includes extension Year 1 Day 0 values for MITT participants treated with placebo in the parent study, and the last pre-treatment value in the parent study for MITT participants treated with Belimumab in the parent study. For years in which a participant was withdrawn from the study, the exit visit assessment was used in place of the Week 48 assessment for the year. This value was not carried forward through later years. Only those participants available at the specified time points (represented by n=X in the category titles) were analyzed.

Blood samples were collected for measurement of serum concentrations of belimumab. Observed belimumab concentrations at Week 12 is presented.

Blood samples were collected for measurement of serum concentrations of belimumab at steady state. Average concentrations were analyzed and reported for all time-points from Week 1 through Week 60.

Blood samples were collected for measurement of serum concentrations of belimumab at steady state. Cmax was analyzed and reported for all time-points from Week 1 through Week 60.

Blood samples were collected for measurement of serum concentrations of belimumab at steady state. Cmin was analyzed and reported for all time-points from Week 1 through Week 60.

The primary objective was to assess the suitability of the auto injector for self-administration of belimumab. An overall assessment of usability and reliability for the device was determined by assessing the rate of successfully complete self-administered injections relative to attempted ones. The assessment for the parameter, drug successfully injected was elicited by a Yes/No response. The participants who were able to administer injections inside and outside of the clinic without assistance were included.

SRI response is defined as \>=4 point reduction, from Baseline in safety of estrogen in lupus national assessment (SELENA) systemic lupus erythematosus disease activity index (SLEDAI) score, no worsening (increase of \<0.30 points from Baseline) in physician's global assessment (PGA) and no new British Isles Lupus Assessment Group of SLE clinics (BILAG) A organ domain score or 2 new BILAG B organ domain scores compared with Baseline. Analysis was performed using a logistic regression model for the comparison between belimumab and placebo with covariates treatment group, Baseline SELENA SLEDAI score (\<=12 vs. \>=13). Percentage of participants with SRI response at Week 52 of Part A were reported. Intent-to-Treat Population comprised of all participants who were randomized and treated with at least one dose of study agent in Part A. One participant had missing data at Baseline and therefore, could not be included in the analysis.

AE rates by SOC adjusting for participant-years on study drug anytime post Baseline are summarized, which included the follow up visits. Only treatmentemergent AEs are summarized. The Baseline is defined as the last available value prior to belimumab start date, for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. The event rate of an AE was calculated as the number of events per 100 participant years: Event Rate=100\* number of events divided by participant years. Participant years were calculated as sum across all participants (\[last visit of interval day minus first visit of interval day plus 1\] divided by 365).

Hematology parameters were assessed at Baseline, Week 8, 16, 24, 32, 40 and 48 during Year 1 to 12; Week 8, 16, 24, 32, and 40 during Year 13; Exit visit and at follow-up (up to 8 weeks and 24 weeks post last infusion). Change from Baseline in basophils, eosinophils, lymphocytes, monocytes, neutrophils segmented and platelets is summarized. The Baseline is defined as the Extension Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value.

Clinical chemistry parameters were assessed at Baseline, Week 8, 16, 24, 32, 40 and 48 during Year 1 to 12; Week 8, 16, 24, 32, and 40 during Year 13; Exit visit and at follow-up (up to 8 weeks and 24 weeks post last infusion). Change from Baseline in BUN, glucose, calcium, carbon dioxide, chloride, magnesium, phosphate, potassium and sodium is summarized. The Baseline is defined as the Extension Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value.

Clinical chemistry parameters were assessed at Baseline, Week 8, 16, 24, 32, 40 and 48 during Year 1 to 12; Week 8, 16, 24, 32, and 40 during Year 13; Exit visit and at follow-up (up to 8 weeks and 24 weeks post last infusion). Change from Baseline in ALT, AP, AST, GGT and LD are summarized. Baseline is defined as the Extension Year 1 Day 0 values for participants treated with placebo in the parent study and last pre-treatment value in the parent study for participants treated with belimumab in the parent study. Change from Baseline is defined as the difference between the post-dose post-Baseline visit value and the Baseline value.

Blood samples were collected at indicated time points for pharmacokinetic (PK) analysis of belimumab. AUCss,0-tau of belimumab for participants weighing \>= 50 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. AUCss,0-tau of belimumab for participants weighing between 30 kg and \< 50 kg has been reported.

Blood samples were collected at indicated time points for PK analysis of belimumab. AUCss,0-tau of belimumab for participants weighing between 15 kg and \< 30 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cavg,ss of belimumab for participants weighing \>= 50 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cavg,ss of belimumab for participants weighing between 30 kg and \< 50 kg has been reported.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cavg,ss of belimumab for participants weighing between 15 kg and \< 30 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cmin,ss of belimumab for participants weighing \>= 50 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cmin,ss of belimumab for participants weighing 30 kg and \< 50 kg has been reported.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cmin,ss of belimumab for participants weighing 15 kg and \< 30 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cmax,ss of belimumab for participants weighing \>= 50 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cmax,ss of belimumab for participants weighing between 30 kg and \< 50 kg has been reported.

Blood samples were collected at indicated time points for PK analysis of belimumab. Cmax,ss of belimumab for participants weighing between 15 kg and \< 30 kg has been reported. As the first dose of belimumab was administered on Day 1, Week 12 post-dose correlates to Day 1 plus 84 days, i.e., Day 85.

Blood samples were collected at indicated time points for measurement of serum concentrations of belimumab following intravenous administration. Pharmacokinetic Population comprised of all safety participants (all randomized participants who received at least one dose of study treatment) for whom at least one evaluable pharmacokinetic sample was obtained and analyzed.

Blood samples were collected at indicated time points for measurement of serum concentrations of belimumab following subcutaneous administration.

Blood samples were collected at the indicated timepoints to calculate Cmax of belimumab.

Blood samples were collected at the indicated timepoints to calculate AUC (0 to t) and AUC (0 to inf) of belimumab.

Blood samples were collected at the indicated time points to calculate t1/2 of belimumab.

Blood samples were collected at the indicated time points to calculate lambda z of belimumab.

Blood samples were collected at the indicated time points to calculate CL of belimumab.

Blood samples were collected at the indicated time points to calculate Vz of belimumab.

AE is any untoward medical occurrence in a participant or clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a medicinal product. For marketed medicinal products, this also includes failure to produce expected benefits (i.e., lack of efficacy), abuse or misuse. SAE is any untoward medical occurrence that, at any dose results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, or is a congenital anomaly/birth defect or is medically significant, or associated with liver injury and impaired liver function.

Blood sample will be collected for estimation of relative bioavailability and assessment of PK parameters including maximum observed concentration; Cmax, area under the concentration-time curve from time 0 to time t; AUC(0-t) and area under the concentration-time curve from time 0 to infinity; AUC(0-inf)