Belimumab 1 mg/kg IV plus standard therapy (SOC) for RA; belimumab 1 mg/kg administered on Days 0, 14, 28, and every 28 days thereafter through 24 weeks in the double-blind period. In the open-label extension period, patients who opted to participate either continued on the same dose of belimumab or may have been switched to belimumab 10 mg/kg at the investigator's discretion for an additional 24 weeks.

Belimumab 4 mg/kg IV plus standard therapy (SOC) for RA; belimumab 4 mg/kg administered on Days 0, 14, 28, and every 28 days thereafter through 24 weeks in the double-blind period. In the open-label extension period, patients who opted to participate either continued on the same dose of belimumab or may have been switched to belimumab 10 mg/kg at the investigator's discretion for an additional 24 weeks.

Belimumab 10 mg/kg IV plus standard therapy (SOC) for RA; belimumab 10 mg/kg administered on Days 0, 14, 28, and every 28 days thereafter through 24 weeks in the double-blind period. In the open-label extension period, patients who opted to participate continued on the same dose of belimumab (10 mg/kg) for an additional 24 weeks.

An ACR70 response is defined as having at least a 70% improvement in tender and swollen joints as well as a 70% improvement in 3 of 5 other criteria (patient assessment, physician assessment, pain scale, disability/functional questionnaire, and acute phase reactant value based on erythrocyte sedimentation rate [ESR]).

The time to first ACR20 response (based on ESR) is defined as the time from the first dose to the first visit at which a patient first exhibited an ACR20 response, which may or may not have been sustained through Week 24.

Measure not posted because time to ACR50 response was unable to be determined due to the small number of patients achieving an ACR50 response in the study.

Measure not posted because time to ACR70 response was unable to be determined due to the small number of patients achieving an ACR70 response in the study.

DAS is a composite index of a patient's level of RA disease activity. DAS28 is an abbreviated version of DAS, using a subset of 28 joints in the assessment, calculated based on 4 variables: 1) number of tender joints out of a total of 28 joints, 2) number of swollen joints out of a total of 28 joints, 3) ESR, 4) patient's global assessment of disease activity based on a 100-mm visual analog scale. The calculation provides a number on a scale from 0 to 10 (>5.1=active disease; <3.2=well controlled disease; <2.6=remission). Change from baseline >1.2 = good response and ≤0.6 = non-response.

DAS28 response is defined as the time from the first dose to the first time at which a patient exhibited a "good" or a "moderate" improvement in RA disease activity, based on DAS28 improvements compared to baseline. Good response was defined as >1.2 change from baseline and DAS28 score ≤ 3.2. No response was defined as ≤ 0.6 change from baseline in DAS28 score or change between ≤ 1.2 and > 0.6 with a DAS28 score of > 5.1.

The modified total Sharp score method was used to evaluate radiographs of hands/wrists for erosions (ERO) and joint space narrowing (JSN). The total modified Sharp score ranges from 0 (no radiographic damage) to 200 (worst possible radiographic damage) and is the sum of the normalized ERO score (range 0-100) and the normalized JSN score (range 0-100). Higher scores indicated more damage.

Belimumab 4 mg/kg IV plus standard therapy (SOC) for RA for 24-week double-blind period of the study. The 24-week open-label extension period of the study included patients who completed the 24-week double-blind period and opted to continue to receive the same dose in the 24-week open-label extension period of the study.

Belimumab 10 mg/kg IV plus standard therapy (SOC) for RA for 24-week double-blind period of the study. The 24 week-open label extension period of the study included patients who completed the 24-week double-blind period and opted to continue in the 24-week open-label period of the study and included patients who were originally randomized to the belimumab 10 mg/kg group in the double-blind period, patients who switched to belimumab 10 mg/kg at the investigator's discretion, and former placebo patients.

Patients who required rescue RA medications were declared nonresponders, as were patients who dropped out or were missing Week 24 data.

P-value was not adjusted for multiple testing.

Belimumab 10 mg/kg IV plus standard therapy (SOC) for RA for 24-week double-blind period of the study

Includes all patients who completed the 24-week double-blind period and opted to continue in a 24-week open-label extension period. Belimumab patients received the same dose or were switched to 10 mg/kg at the investigator's discretion and former placebo patients received belimumab 10 mg/kg. AE onset may be during the extension phase or continuing from the double-blind period.