Proteinuria based on urinary protein creatinine ratio (PCR) measured from 2 consecutive 24h urine collections at Baseline and Week 28, from a pre-intervention spot urine sample and 24 hour urine collection after visit at Weeks 12, 52, 76 and 104, and from a spot urine sample at week 128. Mean PCR was calculated at each time point where there were 2 samples. Baseline is defined as Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Anti-PLA2R autoantibody titers in serum were analyzed by means of a validated anti-PLA2R enzyme linked immunosorbent assay (ELISA) assay from Euroimmun. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Anti-PLA2R autoantibody titers in serum were analyzed by means of a validated anti- PLA2R enzyme linked immunosorbent assay (ELISA) from Euroimmun. Baseline is defined as the Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Complete remission is defined as PCR <30 mg/mmol (proteinuria <0.3grams [g]/24 h) with no worsening in renal function (estimated glomerular filtration rate [eGFR] reduction from Baseline <15 percent). Partial remission is defined as PCR <350 mg/mmol (proteinuria <3.5 g/24 h) but >= 30 mg/mmol (proteinuria >= 0.3g/24h) and decrease of >50 percent from Day 0 Baseline, together with no consistent worsening in renal function (eGFR reduction from Baseline <15percent). Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

Time to complete or partial remission was estimated using the Kaplan-Meier method. Complete remission is defined as PCR <30 mg/mmol (proteinuria <0.3g/24 h) with no worsening in renal function (eGFR reduction from Baseline <15 percent ). Partial remission is defined as PCR <350 mg/mmol (proteinuria <3.5 g/24 h) but >= 30 mg/mmol (proteinuria >= 0.3g/24h) and decrease of >50 percent from Day 0 Baseline, together with no consistent worsening in renal function (eGFR reduction from Baseline <15 percent). Only 1 participant reached complete remission. Hence, statistical analysis for complete remission was not performed.

Complete remission is defined as PCR <30 mg/mmol (proteinuria <0.3g/24 h) with no worsening in renal function (eGFR reduction from Baseline <15percent). Partial remission is defined as PCR <350 mg/mmol (proteinuria <3.5 g/24 h) but >= 30 mg/mmol (proteinuria >= 0.3g/24h) and decrease of >50% from Day 0 Baseline, together with no consistent worsening in renal function (eGFR reduction from Baseline <15percent). Only those participants available at the specified time points were analyzed (represented by n=X in category titles). NA indicates that data was not available as only 1 participant reached complete remission. Hence, standard deviation for complete remission was not calculated.

Incidence of anti-PLA2R autoantibody remission were evaluated by full response and partial response. Full response is defined as antibody undetectable, partial response is defined as reduction in titers by 50 percent. For anti PLA2R autoantibody data, log transformation was applied before the formal analyses. Anti-PLA2R autoantibody blood samples were evaluated at Week 12, 28, 52, 76, 104 and 128/6 week post last-dose. Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

Time to anti-PLA2R autoantibody remission was estimated using Kaplan-Meier method for full response and partial response full response with antibody undetectable and partial response with reduction in titers by 50 percent.

Incidence of anti-PLA2R autoantibody relapse defined as antibody detectable after previously undetectable. Anti-PLA2R autoantibody blood samples were evaluated at Week 12, 28, 52, 76, 104/4 week post last dose, Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

eGFR was assessed from levels of creatinine using the 4 variable version of the modification of diet in renal disease (MDRD) equation as recommended by National Kidney Foundation-Chronic Kidney Disease (NKF-CKD) guidelines. Baseline for eGFR is defined as the mean of the screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

eGFR was assessed from levels of creatinine using the 4 variable version of the modification of diet in renal disease (MDRD) equation as recommended by national kidney foundation-chronic kidney disease (NKF-CKD) guidelines. Baseline for eGFR is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum creatinine was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum creatinine is defined as the mean of the Screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum creatinine was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum creatinine is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum albumin was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum albumin is defined as the mean of the Screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum albumin was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum albumin is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum cholesterol was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum cholesterol is defined as the mean of the Screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum cholesterol was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum cholesterol is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum IgG was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum IgG is defined as the pre-dose Day 0 value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Serum IgG was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum IgG is defined as the pre-dose Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Reduction of proteinuria lessens the risk of thromboembolic and cardiovascular effects and reduces the edema in participants. Investigators physically reviewed participants for clinical manifestations of idiopathic membranous glomerulonephropathy (IMGN) (e.g. edema extending beyond calf) during study and analysis was performed at Week 12, 28, 52, 76 Week 104. Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

The first occurrence of Cmax was determined directly from the serum concentration-time data. The pharmacokinetic (PK) parameters were calculated by standard non-compartmental analysis and all calculations of non-compartmental parameters are being based on actual sampling times.

Trough concentration (Cmin) samples collected on the specified days are being used to assess attainment whether there was sufficient belimumab despite it being lost in the urine from the proteinuria and to check if it improved as proteinuria resolved. Analysis was performed on pre-infusion samples at weeks 2,4,8,12,28,40,52,76 and the 4 week post last-dose.

The AUC(0-2) was determined using the linear trapezoidal rule for increasing concentrations and the logarithmic trapezoidal rule for decreasing concentrations. Blood samples for PK analysis were collected at the following time points: pre-dose (on dosing days): Days 0, 1, 4, 7, 14 and Week 4, 8, 12, 28, 40, 52, 76 and 4 week post last dose. Post-dose (5 minutes after dosing complete): Days 0 and 28. The results will be posted at later date following post hoc analysis.

PK parameters from the urine concentration data: urine Ae(0-24) were assessed. 24 h urine collections for PK analysis were collected after the Day 0 and Weeks 12, 28, 52, 76 doses and at the 4 week post last dose visit. A population approach was undertaken to characterize the population PK parameters and associated variability of belimumab in nephrotic participants. The population approach could have provided derived clearance of belimumab for each participant after the first dose. The population PK analysis was conducted using nonlinear mixed-effect modeling (NONMEM) or appropriate nonlinear mixed-effect analysis software. Several samples were taken pre-dose at Day 0 and some at week 12 incorrectly which affects interpretation.

Health-related quality of life was assessed through participant self-completion of the short form health survey (SF-36 version [v2]), a general health related quality of life metrics. Norm-based Scores (NBS) for physical functioning, role emotional, role physical were assessed. The remaining SF-36 component scores require re-scaling and therefore will be added at a later date. SF-36 was administered prior to any procedures at Weeks 12, 28, 52, 76 and 104/4 week post last dose. Item score were recorded and higher score represented better health status. Baseline is defined as Day 0 pre dose value and change from Baseline was calculated by subtracting the Baseline values from the individual post-randomization values. Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

An AE is any untoward medical occurrence in a clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. The analysis was performed on Safety Population which comprised of all participants who were randomized into the study. 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, is a congenital anomaly/birth defect, may require medical or surgical intervention, is associated with liver injury and impaired liver function.

Blood samples were collected from participants for evaluation of clinical chemistry and hematology parameters. The clinical chemistry parameters included albumin, alkaline phosphatase (alk.phosph.), alanine amino transferase (ALT), aspartate amino transferase (AST), total and direct bilirubin, calcium, cholesterol, chloride, carbon dioxide, creatinine, gamma glutamyl transferase (GGT), glucose, potassium, lactate dehydrogenase (LD), magnesium, sodium, phosphorus, total protein, blood urea nitrogen (BUN) and uric acid. The hematology parameters included basophils, eosinophil, hemoglobin, hematocrit, lymphocytes, monocytes, total neutrophils, platelets, red blood cells (RBC) count and white blood cells (WBC) count. Participants were counted in the category that their value changes to (low or high) for the specific time points. Only those participants with data available at the specified data points were analyzed (represented by n=X in the category titles).

Urine samples were collected for urinalysis by dipstick method from Baseline up to Week 116/16 months follow up and number of participants with findings were presented for Baseline, Week 12, 28, 52, 76, 104/4 weeks post last-dose and Week 116/16 week follow up (WF). The urinalysis parameters included occult blood, glucose, ketones, protein. The findings were presented as trace or 1/10 g/100 milliliter (dL), trace, negative, 4+, 3+, 3+ or 1 g/dL, 2+ or 1/2 g/dL, 2+, 1+ or 1/4 g/dL and 1+. Only participants present at the specific time points were presented (represented by n=X in the category titles).

SBP and DBP were measured from Baseline throughout the treatment period up to Week 116/ 16 week follow-up visit. The Baseline value was taken at Day 0 pre dose and change from Baseline was defined as post dose visit value minus Baseline value. Mean and standard deviation (SD) were measured and presented for Week 12, 28, 52, 76, 104 withdrawn visit, 4 Week post last dose and 16 Week follow-up visit. Only those participants with data available at the specified data points were analyzed (represented by n= X in the category titles).

Pulse rate was measured from Baseline throughout the treatment period up to Week 116/ 16 week follow-up visit. The Baseline value was taken at Day 0 pre dose and change from Baseline was defined as post dose visit value minus Baseline value. Mean and standard deviation (SD) were measured and presented for Week 12, 28, 52, 76, 104 withdrawn visit, 4 Week post last dose and 16 Week post last dose visits. Only those participants with data available at the specified data points were analyzed (represented by n= X in the category titles).

Temperature was measured from Baseline throughout the treatment period up to Week 116/ 16 week follow-up visit. The Baseline value was taken at Day 0 pre dose and change from Baseline was defined as post dose visit value minus Baseline value. Mean and standard deviation (SD) were measured and presented for Week 12, 28, 52, 76, 104 withdrawn visit, 4 Week post last dose and 16 week post last dose visits. Only those participants with data available at the specified data points were analyzed (represented by n= X in the category titles).

Blood samples of participants were collected pre-dose on Weeks 0, 12, 28, 40, 52, 76, 4 week post last dose and 16 week post last dose visit for belimumab immunogenicity assay. No participants showed positive immunogenicity findings.

Urine membrane attack complex was assayed quantitatively by ELISA method. Urine MAC samples were collected at Day 0 and Weeks 8, 28, 52, 76 and 4 week post last dose. Results were normalized using urine creatinine concentration to adjust for urine dilution. Endpoint was moved to 'Exploratory' in Protocol amendment 5 as risk of availability of functioning assay for urine membrane attack complex was noted. No assay was subsequently found and samples were not analyzed

Urine membrane attack complex will be assayed quantitatively by ELISA method. Urine MAC samples are being collected at Day 0 and Weeks 8, 28, 52, 76 and 4 week post last dose. Results will be normalized using urine creatinine concentration to adjust for urine dilution, before calculation of the ratio as value at time point divided by value at Baseline (Day 0). Endpoint was changed to 'exploratory' as risk of availability of functioning assay for urine membrane attack complex was noted. No assay was subsequently found and samples were not analyzed.

B cell Facs panels were used to measure changes over the course of therapy in B cell subsets such as transitional, naïve, memory and plasma B cell compartments by percent of the B cell compartments and absolute numbers. T cell Facs panel were used to measure changes in T cell subsets, such as T regs and CD4+ and CD8+ T cells, in terms of numbers and expression of activation markers to establish if B cell targeting with belimumab affects the T cell compartment perhaps through limiting B cell antigen presentation or cytokine release. Baseline is defined as Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

Cytokine/chemokine associated with T helper skewing or autoimmune pathology will be analyzed using Luminex, ELISA. Serum analyte quantification were used to confirm altered protein levels of any gene expression increases or decreases identified by transcriptomic analysis. Endpoint was moved to 'Exploratory' in Protocol amendment 5 as benefits of assessing cytokines was deemed low. Samples were not analyzed.

Free BLyS protein were analyzed using an ELISA. Serum samples were collected before treatment and after belimumab washout at Week 0 and Week 116/16 week follow-up visit.

B lymphocyte stimulator (BLyS) normalized by creatinine as a ratio of BLyS: creatinine. Free BLyS protein is being analyzed using an ELISA. Urine samples are being collected before treatment and after belimumab washout at Week 0 and Week 116/16 week follow-up visit. Only raw BLyS values available and unable to be assessed due to lack of comparison to a creatinine as a urine concentration marker.

PLA2R autoantibody titers in serum were analyzed at Baseline and Week 28 by means of a validated anti- PLA2R enzyme linked immunosorbent assay (ELISA) from EuroImmun. Baseline is defined as the Day 0 value and change from Baseline was calculated as ratio to Baseline by dividing the Week 28 values with the Baseline values. Ratio to Baseline: Estimated value = 0.27, 2-sided 95% CI=0.12 to 0.58. The geometric mean method was used to calculate the CI.

ITT Population. Only those participants available at the indicated time point (Week 28) were analyzed.

Proteinuria based on urinary protein creatinine ratio (PCR) measured from 2 consecutive 24h urine collections at Baseline and Week 28, from a pre-intervention spot urine sample and 24 hour urine collection after visit at Weeks 12, 52, 76 and 104, and from a spot urine sample at week 128. Mean PCR was calculated at each time point where there were 2 samples. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Proteinuria based on urinary protein creatinine ratio (PCR) measured from 2 consecutive 24h urine collections at Baseline and Week 28, from a pre-intervention spot urine sample and 24 hour urine collection after visit at Weeks 12, 52, 76 and 104, and from a spot urine sample at week 128. Mean PCR was calculated at each time point where there were 2 samples. Baseline is defined as Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population.

Anti-PLA2R autoantibody titers in serum were analyzed by means of a validated anti-PLA2R enzyme linked immunosorbent assay (ELISA) assay from Euroimmun. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population.

Anti-PLA2R autoantibody titers in serum were analyzed by means of a validated anti- PLA2R enzyme linked immunosorbent assay (ELISA) from Euroimmun. Baseline is defined as the Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Complete remission is defined as PCR <30 mg/mmol (proteinuria <0.3grams [g]/24 h) with no worsening in renal function (estimated glomerular filtration rate [eGFR] reduction from Baseline <15 percent). Partial remission is defined as PCR <350 mg/mmol (proteinuria <3.5 g/24 h) but >= 30 mg/mmol (proteinuria >= 0.3g/24h) and decrease of >50 percent from Day 0 Baseline, together with no consistent worsening in renal function (eGFR reduction from Baseline <15percent). Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

ITT Population

Time to complete or partial remission was estimated using the Kaplan-Meier method. Complete remission is defined as PCR <30 mg/mmol (proteinuria <0.3g/24 h) with no worsening in renal function (eGFR reduction from Baseline <15 percent ). Partial remission is defined as PCR <350 mg/mmol (proteinuria <3.5 g/24 h) but >= 30 mg/mmol (proteinuria >= 0.3g/24h) and decrease of >50 percent from Day 0 Baseline, together with no consistent worsening in renal function (eGFR reduction from Baseline <15 percent). Only 1 participant reached complete remission. Hence, statistical analysis for complete remission was not performed.

ITT Population

Complete remission is defined as PCR <30 mg/mmol (proteinuria <0.3g/24 h) with no worsening in renal function (eGFR reduction from Baseline <15percent). Partial remission is defined as PCR <350 mg/mmol (proteinuria <3.5 g/24 h) but >= 30 mg/mmol (proteinuria >= 0.3g/24h) and decrease of >50% from Day 0 Baseline, together with no consistent worsening in renal function (eGFR reduction from Baseline <15percent). Only those participants available at the specified time points were analyzed (represented by n=X in category titles). NA indicates that data was not available as only 1 participant reached complete remission. Hence, standard deviation for complete remission was not calculated.

ITT Population

Incidence of anti-PLA2R autoantibody remission were evaluated by full response and partial response. Full response is defined as antibody undetectable, partial response is defined as reduction in titers by 50 percent. For anti PLA2R autoantibody data, log transformation was applied before the formal analyses. Anti-PLA2R autoantibody blood samples were evaluated at Week 12, 28, 52, 76, 104 and 128/6 week post last-dose. Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

ITT Population

Time to anti-PLA2R autoantibody remission was estimated using Kaplan-Meier method for full response and partial response full response with antibody undetectable and partial response with reduction in titers by 50 percent.

ITT Population

Incidence of anti-PLA2R autoantibody relapse defined as antibody detectable after previously undetectable. Anti-PLA2R autoantibody blood samples were evaluated at Week 12, 28, 52, 76, 104/4 week post last dose, Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

ITT Population

eGFR was assessed from levels of creatinine using the 4 variable version of the modification of diet in renal disease (MDRD) equation as recommended by National Kidney Foundation-Chronic Kidney Disease (NKF-CKD) guidelines. Baseline for eGFR is defined as the mean of the screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

eGFR was assessed from levels of creatinine using the 4 variable version of the modification of diet in renal disease (MDRD) equation as recommended by national kidney foundation-chronic kidney disease (NKF-CKD) guidelines. Baseline for eGFR is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum creatinine was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum creatinine is defined as the mean of the Screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum creatinine was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum creatinine is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum albumin was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum albumin is defined as the mean of the Screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum albumin was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum albumin is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum cholesterol was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum cholesterol is defined as the mean of the Screening and Day 0 values. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum cholesterol was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum cholesterol is defined as the mean of the Screening and Day 0 values and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum IgG was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum IgG is defined as the pre-dose Day 0 value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Serum IgG was assessed as a clinical chemistry laboratory parameter from Baseline up to Week 128/6 month follow-up visit. Baseline for serum IgG is defined as the pre-dose Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Reduction of proteinuria lessens the risk of thromboembolic and cardiovascular effects and reduces the edema in participants. Investigators physically reviewed participants for clinical manifestations of idiopathic membranous glomerulonephropathy (IMGN) (e.g. edema extending beyond calf) during study and analysis was performed at Week 12, 28, 52, 76 Week 104. Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

ITT Population

The first occurrence of Cmax was determined directly from the serum concentration-time data. The pharmacokinetic (PK) parameters were calculated by standard non-compartmental analysis and all calculations of non-compartmental parameters are being based on actual sampling times.

PK Population: all participants in the ITT Population for whom a PK sample was obtained and analyzed.

Trough concentration (Cmin) samples collected on the specified days are being used to assess attainment whether there was sufficient belimumab despite it being lost in the urine from the proteinuria and to check if it improved as proteinuria resolved. Analysis was performed on pre-infusion samples at weeks 2,4,8,12,28,40,52,76 and the 4 week post last-dose.

PK Population

The AUC(0-2) was determined using the linear trapezoidal rule for increasing concentrations and the logarithmic trapezoidal rule for decreasing concentrations. Blood samples for PK analysis were collected at the following time points: pre-dose (on dosing days): Days 0, 1, 4, 7, 14 and Week 4, 8, 12, 28, 40, 52, 76 and 4 week post last dose. Post-dose (5 minutes after dosing complete): Days 0 and 28. The results will be posted at later date following post hoc analysis.

PK Population

PK parameters from the urine concentration data: urine Ae(0-24) were assessed. 24 h urine collections for PK analysis were collected after the Day 0 and Weeks 12, 28, 52, 76 doses and at the 4 week post last dose visit. A population approach was undertaken to characterize the population PK parameters and associated variability of belimumab in nephrotic participants. The population approach could have provided derived clearance of belimumab for each participant after the first dose. The population PK analysis was conducted using nonlinear mixed-effect modeling (NONMEM) or appropriate nonlinear mixed-effect analysis software. Several samples were taken pre-dose at Day 0 and some at week 12 incorrectly which affects interpretation.

PK Population

Health-related quality of life was assessed through participant self-completion of the short form health survey (SF-36 version [v2]), a general health related quality of life metrics. Norm-based Scores (NBS) for physical functioning, role emotional, role physical were assessed. The remaining SF-36 component scores require re-scaling and therefore will be added at a later date. SF-36 was administered prior to any procedures at Weeks 12, 28, 52, 76 and 104/4 week post last dose. Item score were recorded and higher score represented better health status. Baseline is defined as Day 0 pre dose value and change from Baseline was calculated by subtracting the Baseline values from the individual post-randomization values. Only those participants available at the specified time points were analyzed (represented by n=X in category titles).

ITT Population

An AE is any untoward medical occurrence in a clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. The analysis was performed on Safety Population which comprised of all participants who were randomized into the study. 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, is a congenital anomaly/birth defect, may require medical or surgical intervention, is associated with liver injury and impaired liver function.

ITT Population

Blood samples were collected from participants for evaluation of clinical chemistry and hematology parameters. The clinical chemistry parameters included albumin, alkaline phosphatase (alk.phosph.), alanine amino transferase (ALT), aspartate amino transferase (AST), total and direct bilirubin, calcium, cholesterol, chloride, carbon dioxide, creatinine, gamma glutamyl transferase (GGT), glucose, potassium, lactate dehydrogenase (LD), magnesium, sodium, phosphorus, total protein, blood urea nitrogen (BUN) and uric acid. The hematology parameters included basophils, eosinophil, hemoglobin, hematocrit, lymphocytes, monocytes, total neutrophils, platelets, red blood cells (RBC) count and white blood cells (WBC) count. Participants were counted in the category that their value changes to (low or high) for the specific time points. Only those participants with data available at the specified data points were analyzed (represented by n=X in the category titles).

ITT Population

Urine samples were collected for urinalysis by dipstick method from Baseline up to Week 116/16 months follow up and number of participants with findings were presented for Baseline, Week 12, 28, 52, 76, 104/4 weeks post last-dose and Week 116/16 week follow up (WF). The urinalysis parameters included occult blood, glucose, ketones, protein. The findings were presented as trace or 1/10 g/100 milliliter (dL), trace, negative, 4+, 3+, 3+ or 1 g/dL, 2+ or 1/2 g/dL, 2+, 1+ or 1/4 g/dL and 1+. Only participants present at the specific time points were presented (represented by n=X in the category titles).

ITT Population

SBP and DBP were measured from Baseline throughout the treatment period up to Week 116/ 16 week follow-up visit. The Baseline value was taken at Day 0 pre dose and change from Baseline was defined as post dose visit value minus Baseline value. Mean and standard deviation (SD) were measured and presented for Week 12, 28, 52, 76, 104 withdrawn visit, 4 Week post last dose and 16 Week follow-up visit. Only those participants with data available at the specified data points were analyzed (represented by n= X in the category titles).

ITT Population

Pulse rate was measured from Baseline throughout the treatment period up to Week 116/ 16 week follow-up visit. The Baseline value was taken at Day 0 pre dose and change from Baseline was defined as post dose visit value minus Baseline value. Mean and standard deviation (SD) were measured and presented for Week 12, 28, 52, 76, 104 withdrawn visit, 4 Week post last dose and 16 Week post last dose visits. Only those participants with data available at the specified data points were analyzed (represented by n= X in the category titles).

ITT Population

Temperature was measured from Baseline throughout the treatment period up to Week 116/ 16 week follow-up visit. The Baseline value was taken at Day 0 pre dose and change from Baseline was defined as post dose visit value minus Baseline value. Mean and standard deviation (SD) were measured and presented for Week 12, 28, 52, 76, 104 withdrawn visit, 4 Week post last dose and 16 week post last dose visits. Only those participants with data available at the specified data points were analyzed (represented by n= X in the category titles).

ITT Population

Blood samples of participants were collected pre-dose on Weeks 0, 12, 28, 40, 52, 76, 4 week post last dose and 16 week post last dose visit for belimumab immunogenicity assay. No participants showed positive immunogenicity findings.

ITT Population

Urine membrane attack complex was assayed quantitatively by ELISA method. Urine MAC samples were collected at Day 0 and Weeks 8, 28, 52, 76 and 4 week post last dose. Results were normalized using urine creatinine concentration to adjust for urine dilution. Endpoint was moved to 'Exploratory' in Protocol amendment 5 as risk of availability of functioning assay for urine membrane attack complex was noted. No assay was subsequently found and samples were not analyzed

ITT Population

Urine membrane attack complex will be assayed quantitatively by ELISA method. Urine MAC samples are being collected at Day 0 and Weeks 8, 28, 52, 76 and 4 week post last dose. Results will be normalized using urine creatinine concentration to adjust for urine dilution, before calculation of the ratio as value at time point divided by value at Baseline (Day 0). Endpoint was changed to 'exploratory' as risk of availability of functioning assay for urine membrane attack complex was noted. No assay was subsequently found and samples were not analyzed.

ITT Population

B cell Facs panels were used to measure changes over the course of therapy in B cell subsets such as transitional, naïve, memory and plasma B cell compartments by percent of the B cell compartments and absolute numbers. T cell Facs panel were used to measure changes in T cell subsets, such as T regs and CD4+ and CD8+ T cells, in terms of numbers and expression of activation markers to establish if B cell targeting with belimumab affects the T cell compartment perhaps through limiting B cell antigen presentation or cytokine release. Baseline is defined as Day 0 value and change from Baseline was calculated as ratio of post-Baseline value divided by the Baseline value. Only those participants available at the specified time points were analyzed (represented by n=X in the category titles).

ITT Population

Cytokine/chemokine associated with T helper skewing or autoimmune pathology will be analyzed using Luminex, ELISA. Serum analyte quantification were used to confirm altered protein levels of any gene expression increases or decreases identified by transcriptomic analysis. Endpoint was moved to 'Exploratory' in Protocol amendment 5 as benefits of assessing cytokines was deemed low. Samples were not analyzed.

ITT Population

Free BLyS protein were analyzed using an ELISA. Serum samples were collected before treatment and after belimumab washout at Week 0 and Week 116/16 week follow-up visit.

ITT Population

B lymphocyte stimulator (BLyS) normalized by creatinine as a ratio of BLyS: creatinine. Free BLyS protein is being analyzed using an ELISA. Urine samples are being collected before treatment and after belimumab washout at Week 0 and Week 116/16 week follow-up visit. Only raw BLyS values available and unable to be assessed due to lack of comparison to a creatinine as a urine concentration marker.

ITT Population