Number of participants who died during on-treatment period (Week 52) is reported. The on-treatment period was defined as first dose to last dose + 28 days (or death). The As-Treated Population was defined as all participants who were randomized and received at least one dose of study agent,grouped according to the actual treatment administered for the majority (greater than [>]50 percent [%]) of the time. The on-treatment period was the primary analysis period for safety analyses.

As-Treated Population. One participant in placebo group who received belimumab >50% of the time was reported in the belimumab group.

A summary of protocol defined AESIs including serious infections, opportunistic infections and other infections of interest (serious and non-serious), non-melanoma skin cancer (NMSC), malignancies (excluding NMSC), psychiatric events suggesting serious mood disorders and anxiety (serious depression), suicidality (using Columbia-Suicide Severity Rating Scale [C-SSRS]) and serious infusion and hypersensitivity reactions (SIHR) is reported. The on-treatment period (Week 52) was defined as first dose to last dose + 28 days (or death). The on-treatment period was the primary analysis period for safety analyses.

As-Treated Population. One participant in placebo group who received belimumab >50% of the time was reported in the belimumab group. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

An SAE is defined as any untoward medical occurrence that results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent disability/incapacity, is a congenital anomaly/birth defect, associated with liver injury and impaired liver function or any other situations as per medical or scientific judgement. The on-treatment period (Week 52) was defined as first dose to last dose + 28 days (or death) and was the primary analysis period for safety analyses.

As-Treated Population. One participant in placebo group who received belimumab >50% of the time was reported in the belimumab group.

Number of participants who died during on-study period (Week 52) is reported. The on-study period (which includes on and off treatment data) was defined as first dose to the end of the Week 52 study follow-up (or death). The on-study period was a supportive analysis period for safety analysis.

As-Treated Population. One participant in placebo group who received belimumab >50% of the time was reported in the belimumab group.

A summary of protocol defined AESIs including serious infections, opportunistic infections and other infections of interest (serious and non-serious), NMSC, malignancies (excluding NMSC), psychiatric events suggesting serious mood disorders and anxiety (serious depression), suicidality (using C-SSRS) and SIHR is reported. The on-study period (Week 52) (which includes on and off treatment data) was defined as first dose to the end of the Week 52 study follow-up (or death). The on-study period was a supportive analysis period for safety analysis.

As-Treated Population. One participant in placebo group who received belimumab >50% of the time was reported in the belimumab group. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

A SAE is defined as any untoward medical occurrence that results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent disability/incapacity, is a congenital anomaly/birth defect, associated with liver injury and impaired liver function or any other situations as per medical or scientific judgement. The on-study period (Week 52) (which includes on and off treatment data) was defined as first dose to the end of the Week 52 study follow-up (or death) and was a supportive analysis period for safety analyses.

As-Treated Population. One participant in placebo group who received belimumab >50% of the time was reported in the belimumab group.

The average daily prednisone dose during Weeks 40 to 52 is the sum of all prednisone doses to treat SLE from the day following the Week 40 visit date up to but not including the Week 52 study completion date divided by the number of days between Week 40 visit date and study completion date (study completion date - Week 40 visit date). Percentage of participants whose average prednisone dose has been reduced by >=25% from Baseline to <=7.5 mg/day during Weeks 40 through 52 in participants with average prednisone use greater than 7.5 mg/day at Baseline was compared between belimumab and placebo using a logistic regression model including treatment group, Baseline prednisone dose, screening safety of estrogen in lupus national assessment (SELENA) systemic lupus erythematosus disease activity index (SLEDAI) score (<=9 versus >=10) and region. Baseline is defined as the last available value measured prior to dosing on or before the date of first dose (Day 1).

ITT Population. Only those participants with Baseline prednisone>7.5 mg/day were analyzed. The ITT population is defined as all participants who were randomized and received at least one dose of study agent and the analysis was performed per the treatment that a participant was randomized to receive, regardless of the actual treatment received.

Number of participants with all-cause mortality during years 2 to 5 has been presented.

As-Treated Any Year 2-5 Follow-up Population consisted of all participants in the As-Treated population who completed at least one post-treatment follow-up visit for Year 2 to 5.

Number of participants with new primary malignancies during years 2 to 5 has been presented.

As-Treated Any Year 2-5 Follow-up Population