Abatacept in the Treatment and Prevention of Active Systemic Lupus Erythematosus (SLE) Flares in Combination With Prednisone

DB; Number of Participants Who Died, Experienced AEs, Other SAEs or Discontinuations Due to AEs, Drug Related AEs

AEs: any new untoward medical occurrences/worsening of pre-existing medical condition, whether or not related to study drug. SAE: any AE that resulted in death; was life threatening; resulted in persistent/significant disability/incapacity; resulted in/prolonged an existing in-patient hospitalization; was a congenital anomaly/birth defect; or was an overdose. Drug-related AEs: events with a certain; probable; possible; or missing relationship to the study therapy. Participants who discontinued the study due to an AE were recorded.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With Significant AEs of Special Interest

An AE was defined as any new untoward medical occurrence or worsening of a pre-existing medical condition (even if not caused by the study drug). For this study, AEs of special interest were associated with the use of immunomodulatory agents. Number of participants with infections, malignant neoplasms, pre-specified autoimmune disorders, acute infusional AEs and peri-infusional AEs were recorded.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With MAs in Hematology: Hemoglobin, Hematocrit, Erythrocytes and Platelet Count

MAs are laboratory measurements marked as abnormal, per pre-defined study criteria, at any study time point. The following hematology MA definitions specify the criteria for the data presented. Hemoglobin: \>3 g/dL decrease from pre-treatment (pre-Rx) value; hematocrit: \<0.75\* pre-Rx value; erythrocyte count: \<0.75\* pre-Rx value; platelet count: \<0.67\* LLN or \>1.5\* ULN (or, if pre-Rx value \<LLN, then \<0.5\* pre-Rx value or \<100000/mm\^3).

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With MAs in Hematology: Leukocytes, Neutrophils + Bands (Absolute), Lymphocytes (Absolute), Monocytes (Absolute), Basophils (Absolute) and Eosinophils (Absolute)

MAs are laboratory measurements marked as abnormal, per pre-defined study criteria, at any study time point. The following hematology MA definitions specify the criteria for the data presented. Leukocytes: \<0.75\* LLN or \>1.25\* ULN (or, if pre-Rx value \<LLN, then \<0.8\* pre-Rx or \>ULN. If pre-Rx value \>ULN, then \>1.2\* pre-Rx or \<LLN; Neutrophils+bands (absolute): \<1.00\* 10\^3 cells/microliter (c/uL); Lymphocytes (absolute): \<0.75\* 10\^3 c/uL or \>7.50\* 10\^3 c/uL; Monocytes (absolute): \>2000/mm\^3; Basophils (absolute): \>0.40\* 10\^3 c/uL; Eosinophils (absolute): \>0.75\* 10\^3 c/uL.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB: Number of Participants With MAs in Serum Chemistry: ALP, AST, ALT, GGT, Bilirubin (Total), BUN and Creatinine

MAs are laboratory measurements marked as abnormal, per pre-defined study criteria, at any study time point. The following serum chemistry MA definitions specify MA criteria. ALP, GGT: \>2\* ULN (if pre-Rx \>ULN, then \>3\* pre-Rx); AST, ALT: \>3\* ULN (if pre-Rx \>ULN, then \>4\* pre-Rx). Bilirubin (total): \>2\* ULN (if pre-Rx \>ULN, then \>4\* pre-Rx), BUN:\>2\* pre-Rx; Creatinine:\>1.5\* pre-Rx.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With MAs in Serum Chemistry: Sodium (Serum), Potassium (Serum), Chloride (Serum), Calcium (Total),Protein (Total)

MAs are laboratory measurements marked as abnormal as per pre-defined study criteria, at any study time point. The following serum chemistry MA definitions specify MA criteria, Sodium (serum): \<0.95\* LLN or \>1.05\* ULN (if pre-Rx \<LLN, then \<0.95\* pre-Rx or \>ULN. If pre-Rx \>ULN, then \>1.05\* pre-Rx or \<LLN); Potassium (serum), Chloride (serum), protein (total): \<0.9\* LLN or \>1.1\* ULN (if pre-Rx \<LLN, then \<0.9\* pre-Rx or \>ULN. If pre-Rx \>ULN, then \>1.1\* pre-Rx or \<LLN; Calcium (total): \<0.8\* LLN or \>1.2\* ULN (if pre-Rx \<LLN, then \<0.75\* pre-Rx or \>ULN. If pre-Rx \>ULN, then \>1.25\* pre-Rx or \<LLN.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With MAs in Serum Chemistry: Glucose (Serum), Glucose (Fasting Serum), Albumin, Cholesterol (Total), Triglycerides, Fasting Triglycerides

MAs are laboratory measurements marked as abnormal, per pre-defined study criteria, at any study time point. The following serum chemistry MA definitions specify MA criteria, Glucose: \<65 mg/dl or \>220 mg/dl; Glucose (fasting serum): \<0.8\* LLN or \>1.5 ULN (if pre-Rx \<LLN, then \<0.8\* pre-Rx or \>ULN. If pre-Rx \>ULN, then \>2.0\* pre-Rx or \<LLN; Albumin: \<0.9\* LLN (if pre-Rx \<LLN, then \<0.75 \* pre-Rx); cholesterol (total): \>2\* pre-Rx; triglycerides: \>=2.5\* ULN, or if pre Rx\>ULN then use \>2.5\* pre Rx; fasting triglycerides: \>=2.0\* ULN, or if pre Rx\>ULN then use \>2.0\* pre Rx.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With MAs in Urinalysis

MAs are laboratory measurements marked as abnormal, per pre-defined study criteria, at any study time point. The following definitions specify the criteria for MAs in urinalysis, Protein, glucose, blood, Leukocyte esterase, RBC, WBC: \>=2+ (or, if value \>=4, or if pre-Rx value = 0 or 0.5, then \>= 2\* pre-Rx, or if pre-Rx value =1, then \>=3, or if pre-Rx = 2 or 3, then \>=4); protein (24 hour urine): \>1000 mg/24 hrs and \>=2\* pre-Rx; GFR: \<=60 mL/min/1.73m\^2 or \> 15% change from baseline; Protein/creatinine ratio: \> 100 mg/mmol.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With Clinically Significant Abnormal Vital Signs and/or Physical Examination Findings

Vital signs assessments and physical examination were conducted throughout the study. Vital signs assessments included body temperature, respiratory rate, blood pressure (systolic and diastolic) and heart rate. The investigator used his/her clinical judgment to decide whether or not abnormalities in vital signs or physical examination were clinically meaningful.

Time frame: Events recorded at each participant encounter, from start of study drug therapy up to Day 337, including up to 56 days after the last dose or up to the first dose of open-label, whichever occurred earlier

DB; Number of Participants With Antibodies Specific for CTLA4-T and Abatacept, Following Abatacept Treatment

Electrochemiluminescence (ECL) immunoassay based on Meso Scale Discovery (MSD) technology was used to detect antibodies specific for CTLA4-T and for abatacept.

Time frame: From Day 1 to Day 365

OL; Number of Participants With a New SLE Flare

SLE flares scored using BILAG:A:presence of =\>1 serious lupus features;B:more moderate features;C:mild symptomatic features;D:prior activity with no current symptoms due to active lupus;E:an organ that has never been involved.BILAG scores based on degrees of change in clinical features (1=improving,2=staying the same,3=worsening,4=new).New SLE flare means new BILAG A/B features in any organ system.Based on the recommendation of the Data Monitoring Committee, open-label period terminated, as failed to meet primary outcome measure for double-blind period/increase in SAEs in abatacept group.

Time frame: From start of study drug therapy in open-label period (Day 365), Day 393, 421, 449 and every 28 days thereafter till Day 729.

OL; Number of Participants With a Change in the SLICC/ACR Damage Index at Year 2 Compared to Baseline

SLICC/ACR damage index:measure of cumulative damage due to SLE.Damage=non-reversible change occurring since onset of lupus,ascertained by clinical assessment \& present for =\>6 months.Scores of SLICC/ACR index:1:single episode;2:repeated episodes at least 6 months apart.Change in score from baseline to 1 year presented as:no change,increase 1 (an increase in score of 1),increase \>1 (an increase in score of \>1).Based on recommendation of Data Monitoring Committee, open-label period terminated, as failed to meet primary outcome measure for double-blind period/increase in SAEs in abatacept group.

Time frame: From start of study drug therapy in open-label period (Day 365) and on Day 729.

OL; Total Number of BILAG A Flares Each Participant Experienced

Total number of BILAG A flares in any organ system after steroid tapering = new BILAG A features in any organ system. Scores defined as follows: None: participants with no BILAG A flare; 1: participants with 1 BILAG A flare or participants who discontinued without a new BILAG A flare were imputed as having one event. 2: participants with 2 BILAG A flares; 3 or \>3: participants with 3 or more BILAG A flares.Based on recommendation of Data Monitoring Committee, open-label period terminated, as failed to meet primary outcome measure for double-blind period/increase in SAEs in abatacept group.

Time frame: From start of study drug therapy in open-label period (Day 365), Day 393, 421, 449 and every 28 days thereafter till Day 729.

OL; Area Under the Curve (AUC) for Prednisone or Prednisone Equivalent

Total exposure to glucocorticosteroid was measured by the total prednisone or prednisone equivalent AUC. Based on the recommendation of the Data Monitoring Committee, the open-label, long-term extension period was terminated by the sponsor, for failure to meet the primary outcome measure for the double-blind period and because of an increase in SAEs in the abatacept treatment group. As such, these data were not analyzed.

Time frame: From start of study drug therapy in open-label period (Day 365), Day 393, 421, 449 and every 28 days thereafter till Day 729.

OL; Number of Participants With Antibodies Specific for CTLA4-T and Abatacept, Following Abatacept Treatment

MSD technology was used to detect antibodies specific for CTLA4-T and for abatacept.

Time frame: After the first dose of open-label period