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.

Modified Intent-to-Treat (MITT) Population comprised of all randomized participants who received at least one dose of study treatment (Belimumab or Rituximab or Placebo) and excluding participants from Arm 3 (Belimumab + Standard therapy) who were randomized prior to 07-Sep-2018.

Percentage of participants with a state of clinical remission (IBA) was defined as percentage of participants with a clinical SLEDAI-2K score =0 (does not include anti-double stranded deoxyribonucleic [dsDNA] and complement activity scores), achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of 0 mg/day at Week 64. SLEDAI-2K was a weighted, cumulative index for measuring 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 the visit or in the preceding 10 days. The clinical SLEDAI-2K score was sum of 22 out of all 24 individual items from the SLEDAI-2K and ranges from 0 (no symptoms) to 101 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of disease control (IBA) was defined as the percentage of participants with a SLEDAI-2K score <=2, achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of <=5 mg/day at Week 104. SLEDAI-2K was a weighted, cumulative index for measuring SLE disease activity in previous 10 days which consisted of 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 the visit or in the preceding 10 days. The SLEDAI-2K score was the sum of all 24 individual items from the SLEDAI-2K which ranges from 0 (no symptoms) to 105 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of disease control (IBA) was defined as the percentage of participants with a SLEDAI-2K score <=2, achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of <=5 mg/day. SLEDAI-2K was a weighted, cumulative index for measuring SLE disease activity in previous 10 days which consisted of 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 the visit or in the preceding 10 days. The SLEDAI-2K score was the sum of all 24 individual items from the SLEDAI-2K which ranges from 0 (no symptoms) to 105 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of clinical remission (IBA) was defined as percentage of participants with a clinical SLEDAI-2K score =0 (does not include anti-dsDNA and complement activity scores), achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of 0 mg/day. SLEDAI-2K was a weighted, cumulative index for measuring 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 the visit or in the preceding 10 days. The clinical SLEDAI-2K score was sum of 22 out of all 24 individual items from the SLEDAI-2K and ranges from 0 (no symptoms) to 101 (presence of all defined symptoms) with higher scores representing increased disease activity

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of CR (Principal Investigator [PI] assessed) was defined as percentage of participants with a SLEDAI-2K=0 achieved without immunosuppressants and with corticosteroids at prednisone equivalent dose of 0 mg/day,sustained for at least 24 weeks. Sustained CR was longest period a participant maintains CR without break calculated as last consecutive CR date minus first consecutive CR date plus 1. SLEDAI-2K consisted of 24 individual items within each 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at time of visit or in preceding 10 days. SLEDAI-2K score was sum of all 24 individual items from SLEDAI-2K, ranges from 0(no symptoms) to 105(presence of all defined symptoms),higher scores indicates increased disease activity. Percentage of participants with a state of CR sustained for at least 24 weeks at any visit during Week 52 to Week 104 were reported.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of CLR (PI assessed) at Week 104 was defined as percentage of participants with a clinical SLEDAI-2K score=0 (does not include anti-dsDNA and complement activity scores) achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of 0 mg/day, sustained for at least 24 weeks(from Week 80 to Week 104). Sustained CLR is longest period a participant maintains CLR without a break, calculated as last consecutive CLR date minus first consecutive CLR date plus 1. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was 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 clinical SLEDAI-2K score was sum of 22 out of all 24 individual items from the SLEDAI-2K and ranges from 0 (no symptoms) to 101 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of complete remission (PI assessed) was defined as the percentage of participants with a SLEDAI-2K score =0, achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of 0 mg/day. SLEDAI-2K was a weighted, cumulative index for measuring systemic lupus erythematosus (SLE) disease activity in the previous 10 days which consisted of 24 individual items in which signs and symptoms, laboratory tests, and physician's assessment for each item within for 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 the visit or in the preceding 10 days. The SLEDAI-2K score was the sum of all 24 individual items from the SLEDAI-2K which ranges from 0 (no symptoms) to 105 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Time to first severe SLE flare was the number of days from treatment start date until the participant met an event. Time to first severe flare was defined as event date minus treatment start date plus 1. Time to first severe flare was measured by Modified SLE flare index which identifies whether a participant had experienced a mild/moderate or severe flare. Analysis of first severe flare was performed on the modified SLE Flare index that excludes severe flares that were triggered only by an increase is SLEDAI-2K score to greater than 12.

Modified Intent-to-Treat (MITT) Population

Time to first SLE flare was the number of days from treatment start date until the participant met an event. Time to first flare was defined as event date minus treatment start date plus 1. Time to first flare was measured by modified SLE flare index which identifies whether a participant had experienced a mild/moderate or severe flare.

Modified Intent-to-Treat (MITT) Population

Disease control sustained for at least 24 weeks and maintained through Week 104 was defined as SLEDAI-2K score <=2, achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of <=5 mg/day. Time to disease control (PI assessed) was defined as the first visit of sustained disease control until Week 104 on or before Week 80 minus treatment start date (Day 1) plus 1. Sustained disease control was longest period a participant maintained disease control without a break. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at the time of visit or in preceding 10 days. SLEDAI-2K score was the sum of all 24 individual items from SLEDAI-2K , ranges from 0 (no symptoms) to 105 (presence of all defined symptoms),higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Clinical remission sustained for at least 24 weeks and maintained through Week 104 was defined as clinical SLEDAI-2K score=0 (does not include anti-dsDNA and complement activity scores), achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of 0 mg/day. Time to CLR (PI assessed) was defined as first visit of sustained CLR until Week 104 on or before Week 80 minus treatment start date (Day 1) plus 1. Sustained CLR was longest period a participant maintained clinical remission without a break. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at the time of visit or in preceding 10 days. The clinical SLEDAI-2K score was sum of 22 out of all 24 individual items from the SLEDAI-2K and ranges from 0 (no symptoms) to 101 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population

Duration of disease control was defined as SLEDAI-2K score <=2, achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of <=5 mg/day. The duration of disease control (PI assessed) was the longest period between 2 visits that the participant was a disease control responder at all visits and calculated as the first visit of disease control minus last visit of disease control plus 1. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at the time of visit or in preceding 10 days. SLEDAI-2K score was the sum of all 24 individual items from SLEDAI-2K, ranges from 0(no symptoms) to 105 (presence of all defined symptoms),higher scores representing increased disease activity

Modified Intent-to-Treat (MITT) Population. Only those participants with at least one assessment where disease control was met were analyzed.

Clinical remission was defined as clinical SLEDAI-2K score =0 (does not include anti-dsDNA and complement activity scores), achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of 0 mg/day. The duration of clinical remission (PI assessed) was the longest period between 2 visits that the participant was a clinical remission responder at all visits and was calculated as the first visit of clinical remission minus last visit of clinical remission plus 1. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at the time of visit or in preceding 10 days. The clinical SLEDAI-2K score was sum of 22 out of all 24 individual items from the SLEDAI-2K and ranges from 0 (no symptoms) to 101 (presence of all defined symptoms) with higher scores representing increased disease activity.

Modified Intent-to-Treat (MITT) Population. Only those participants with at least one assessment where clinical remission was met were analyzed.

The SLEDAI-2K consisted of 24 individual items within 9 organ systems. Each item was given a weighted score (1 to 8 with higher score indicating increased activity) and summed if present at the time of visit or in the preceding 10 days. Weighted scores for central nervous system (CNS) (7 items) was 8; for vascular (1 item) was 8; for Musculoskeletal (2 items) was 4; for Renal (4 items) was 4; for Mucocutaneous (3 items) was 2; for Cardiovascular and Respiratory (2 items) was 2; for Immunologic (2 items) was 2;for Constitutional (1 item) was 1 and for Hematologic (2 items) was 1. SLEDAI-2K score was the sum of all 24 individual items from the SLEDAI-2K which ranges from 0 (no symptoms) to 105 (presence of all defined symptoms) with higher scores representing increased disease activity. Baseline value was latest pre-dose assessment with a non-missing value, including those from unscheduled visits. Change from Baseline was defined as post-dose visit value minus Baseline value.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles).

SLEDAI-2K assessments consisted of 24 individual items with 9 organ systems. Each item was given a weighted score(1 to 8 with higher score indicating increased activity)and summed if present at the time of analysis. SLEDAI-2K score was sum of all 24 individual items from SLEDAI-2K ranges from 0(no symptoms) to 105(presence of all defined symptoms). Higher scores indicates increased disease activity. An improvement was defined as a decrease(compared to Baseline) in SLEDAI-2K score within same organ system at a post-Baseline visit. Baseline value was latest pre-dose assessment with a non-missing value, including those from unscheduled visits. Data for following organ systems was reported: CNS total, Vascular total, Musculoskeletal total, Renal total, Mucocutaneous total, Cardiovascular (Cardio) and Respiratory (Resp) total, Immunologic total and Hematologic total. Constitutional organ system was removed from analysis and its one item (fever)moved to hematologic organ system.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles). Only participants with organ system involvement at Baseline were included.

SLEDAI-2K assessments consisted of 24 individual items with 9 organ systems. Each item was given a weighted score(1 to 8 with higher score indicating increased activity)and summed if present at time of analysis. SLEDAI-2K score was sum of all 24 individual items from SLEDAI-2K, ranges from 0(no symptoms) to 105(presence of all defined symptoms). Higher scores indicates increased disease activity. A worsening was defined as an increase(compared to Baseline) in SLEDAI-2K score within same organ system at a post-Baseline visit. Baseline value was latest pre-dose assessment with a non-missing value, including those from unscheduled visits. Percentage of participants with SLEDAI-2K organ worsening for following organ systems were reported;CNS total,Vascular total,Musculoskeletal total,Renal total,Mucocutaneous total,Cardio and Resp total,Immunologic total and Hematologic total. Constitutional organ system was removed from analysis and its one item (fever)moved to hematologic organ system.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles). Only participants with no organ system involvement at Baseline were included.

The Physician's Global Assessment (PGA) was a physician-reported visual analogue scale that provides an overall measure of the participant's current disease activity. Physician's Global Assessment was collected on a 10 centimeter (cm) visual analogue scale (VAS) by placing a mark on the scale between 0 (no disease activity) to 10 (maximum disease activity). The PGA score was then rescaled for reporting by multiplying the collected score by 3 divided by 10. Hence, the PGA score ranges from 0 to 3 with higher scores indicating greater disease activity. Baseline value was the latest pre-dose assessment with a non-missing value, including those from unscheduled visits. Change from Baseline was defined as the post-dose visit value minus Baseline value.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles).

The SLICC-ACR Damage Index measures irreversible (not related to active inflammation) changes occurring since the diagnosis of SLE ascertained by clinical assessment and present for at least 6 months. The questionnaire contains 39 items covering 12 different organ systems which were scored on a numerical scale between 0 (no damage) to 7 (increasing disease damage). Individual ranges for organ systems were; ocular: 0-2, neuropsychiatric: 0-6, renal: 0-3, pulmonary: 0-5, cardiovascular:0-6, peripheral vascular: 0-5, gastrointestinal:0-5, musculoskeletal: 0-6, skin: 0-3, endocrine (diabetes): 0-1, gonadal:0-1 and malignancies: 0-2. The SLICC-ACR score was calculated by taking sum of the individual scores for 12 organ systems which ranges from 0 (no damage) to 45 (increasing disease damage) where higher score indicates increasing disease damage severity. Baseline value was the latest pre-dose assessment with a non-missing value, including those from unscheduled visits.

Modified Intent-to-Treat (MITT) Population

Lupus low disease activity state (LLDAS) was defined as a state which, if sustained, was associated with a low likelihood of adverse outcome, considering disease activity and medication safety. The LLDAS response criteria were: (1) SLEDAI-2K <=4, with no activity in major organ systems (renal, CNS, cardiopulmonary, vasculitis, fever) and no hemolytic anemia or gastrointestinal activity; (2) no new features of lupus disease activity compared with the previous assessment; (3) PGA (scale 0-3), <=1; (4) current prednisolone (or equivalent) dose <=7.5 mg daily; and (5) well tolerated standard maintenance doses of immunosuppressive drugs and approved biological agents, excluding investigational drugs. Percentage of participants that met the LLDAS response criteria were reported.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of disease control was defined as the percentage of participants with a SLEDAI-2K score <=2, achieved without immunosuppressants and with corticosteroids at a prednisone equivalent dose of <=5 mg/day, using the PI assessment of SLEDAI-2K. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at the time of visit or in preceding 10 days. SLEDAI-2K score was the sum of all 24 individual items from SLEDAI-2K, ranges from 0 (no symptoms) to 105 (presence of all defined symptoms), higher scores representing increased disease activity. Percentage of participants with a state of disease control using the PI assessment of SLEDAI-2K were summarized.

Modified Intent-to-Treat (MITT) Population

Percentage of participants with a state of clinical remission was defined as the percentage of participants with a clinical SLEDAI-2K score =0 (does not include anti-dsDNA and complement activity scores), achieved without immunosuppressants (which was allowed in Belimumab+ Standard therapy arm only) and with corticosteroids at a prednisone equivalent dose of 0 mg/day using the PI assessment of SLEDAI-2K. SLEDAI-2K consisted of 24 individual items within each of 9 organ systems. Each item was given a weighted score (1 to 8, higher score indicates increased activity) and summed if present at the time of visit or in preceding 10 days. The clinical SLEDAI-2K score was sum of 22 out of all 24 individual items from the SLEDAI-2K and ranges from 0 (no symptoms) to 101 (presence of all defined symptoms) with higher scores representing increased disease activity. Percentage of participants with a state of clinical remission using the PI assessment of SLEDAI-2K were summarized.

Modified Intent-to-Treat (MITT) Population

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of a study treatment, whether or not considered related to the study treatment. A SAE is defined as any untoward medical occurrence that, at any dose 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 or any other situations as per medical or scientific judgment. Data for number of participants with SAE and non-SAE (>=5 %) has been summarized.

Intent-to-Treat Population comprised of all randomized participants who received at least one dose of study treatment (Belimumab or Rituximab or Placebo).

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of a study treatment, whether or not considered related to the study treatment. AESIs were Malignant Neoplasms, Post-Injection Systemic Reactions (PISR), All Infections of Special Interest (Opportunistic Infections (OI), Herpes Zoster (HZ), Tuberculosis (TB), and Sepsis), Depression (including mood disorders and anxiety)/suicide/self-injury and Deaths. Data for number of participants with AESIs has been summarized.

Intent-to-Treat Population

The Patient's Global Assessment (PtGA) of Disease Activity is a single-item, participant reported scale developed for the assessment of the participant's overall rating of their disease activity due to SLE. The scale measures disease activity ranging from 0 (Very Well) to 10 (Very Poor) and the higher score indicates severe disease activity. Baseline value was the latest pre-dose assessment with a non-missing value, including those from unscheduled visits. Change from Baseline was defined as the post-dose visit value minus Baseline value.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles).

LupusQoL is a SLE-specific health related qualify of life (HRQOL) instrument with 34 questions across 8 domains:Physical health(8 items),Pain(3 items),Planning(3 items),Intimate relationship(2 items),Burden to others(3 items),Emotional health(6 items),Body image(5 items),Fatigue(4 items). Questions were related to participants experience in prior 4 weeks.A 5-point Likert response format was used, ranging from 0(all of the time) to 4(never) for each question. Individual domain scores were reported which were calculated by taking sum of responses to all items within each domain. Individual domain scores range:Physical health(0-32),Pain(0-12),Planning(0-12),Intimate relationship(0-8),Burden to others(0-12),Emotional health(0-24),Body image(0-20),Fatigue(0-16). Higher score indicates better HRQOL. Baseline value was latest pre-dose assessment with a non-missing value including those from unscheduled visits. Change from Baseline was defined as post-dose visit value minus Baseline value.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles).

The FACIT-Fatigue scale was a 13-item questionnaire completed by the participant, which provides a measure of fatigue/quality of life, with a 7-day recall period. The participant scored each item on a 5-point scale: 0 (Not at all) to 4 (Very much). The higher score for the questions, the greater the fatigue. The total score was the sum of the responses from all questions (inverted for reversed items) multiplied by 13, then divided by the number of questions answered, ranging from 0 (worse fatigue) to 52 (no fatigue) where a higher score indicates an improvement in the participant's health status and decrease in the score indicates worse fatigue/quality of life. Baseline value was the latest pre-dose assessment with a non-missing value, including those from unscheduled visits. Change from Baseline was defined as the post-dose visit value minus Baseline value.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles).

The FACIT-Fatigue scale was a 13-item questionnaire completed by the participant, which provides a measure of fatigue/quality of life, with a 7-day recall period. The participant scored each item on a 5-point scale: 0 (Not at all) to 4 (Very much). The larger the participant's response to the questions, the greater the fatigue. The total score was the sum of the responses (inverted for reversed items) multiplied by 13, then divided by the number of questions answered, ranging from 0 (worse fatigue) to 52 (no fatigue) where a higher score indicates an improvement in the participant's health status and decrease in the score indicates worse fatigue/quality of life. A participant was considered to had an improvement exceeding the minimal clinically important difference if they had >=4 points improvement in their FACIT-Fatigue Scale score from Baseline. Percentage of participants with improvement in FACIT-Fatigue scale score exceeding the MCID (>=4 points) were summarized.

Modified Intent-to-Treat (MITT) Population. Only those participants with data available at specified time points were analyzed (represented by n=X in category titles).