The ACR 20 is based on 20% improvement (compared with baseline values) in tender and swollen joint counts and on 20% improvement in 3 of the remaining 5 core set measures (participant global assessment of pain, participant global assessment of disease activity, physician global assessment of disease activity, participant assessment of physical function) and 1 acute phase reactant value.

All randomized participants who received study drug.

The ACR defines ACR 50 and ACR70 response as a 50% or 70% improvement (compared with baseline values) in tender and swollen joint counts and 50% or 70% improvement in 3 of the remaining 5 core set measures (patient global assessment of pain, patient global assessment of disease activity, physician global assessment of disease activity, subject assessment of physical function) and 1 acute phase reactant value (C-reactive protein).

All randomized participants who received study drug.

The ACR defines improvement in core components as 20%, 50%, or 70% improvement in tender and swollen joint counts and 3 of the remaining core components: patient global assessment of disease activity, physician global assessment of disease activity, patient assessment of pain, patient self-assessed disability (Health Assessment Questionnaire Disability Index [HAQ-DI]), and levels of 1 acute phase reactant (C-reactive protein levels or erythrocyte sedimentation rate.) The HAQ-DI assesses a patient's level of functional ability via 20 questions in 8 categories of functioning; scale=0 (no disability) to 3 (completely disabled); total possible score=24. The higher the score, the greater the disability.

All randomized participants who received study drug and who were evaluable.

Adjusted mean change from baseline. The DAS28 provides a score on a scale from 0 to 10 indicating the current activity of rheumatoid arthritis (>5.1=high disease activity; <3.2=low disease activity; <2.6=remission). CRP or ESR give estimations of DAS28 values on a group level. Change from Baseline=Postbaseline - Baseline value.

All randomized participants who received study drug and who were evaluable.

Adjusted mean change from baseline. The HAQ-DI assesses a patient's level of functional ability via 20 questions in 8 categories of functioning. Patients respond on a scale from 0 (no disability) to 3 (completely disabled); total possible score=24. Higher score indicates greater disability. Change from baseline= postbaseline - baseline value.

All randomized participants who received study drug

Adjusted mean change from baseline. The SF-36 is a 36-item self-administered questionnaire developed to assess health-related quality of life and comprised of 8 domains( including 4 physical and 4 mental subscales) used to derive the physical and mental component summary scores. All subscales were scored using norm-based methods that standardized the scores to a mean of 50 and a standard deviation of 10 in the general population. The scores range from 0 to 100, with a higher score indicating better quality of life. Change from baseline=postbaseline - baseline value.

All randomized participants who received study drug and were evaluable.

AE=any new untoward medical occurrence or worsening of a preexisting medical condition that does not necessarily have a causal relationship with this treatment. Related AE=relationship of certain, probable, possible, or missing. SAE=any untoward medical occurrence that at any dose: results in death, is life-threatening, requires inpatient hospitalization or causes prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, results in the development of drug dependency or drug abuse, is an important medical event.

All randomized participants who received study drug.

Steady-state PK parameters following administration of body-weight tiered doses approximating 10 mg/kg. Tmax = the time after administration of a drug when the maximum plasma concentration is reached; when the rate of absorption equals the rate of elimination. T-Half = the biological half-life or elimination half life of a substance is the time it takes for a substance to lose half of its pharmacologic, physiologic, or radiologic activity.

Participants with measurement at stated dose level

Steady-state PK parameters following administration of body-weight tiered doses approximating 10 mg/kg. Maximum Concentration (Cmax)= the maximum plasma concentration of the drug.

Participants with measurement at stated dose level

Area Under the Plasma Concentration-Time Curve (AUC), a measure of drug absorption, in a dosing interval of 28 days from Day 85 to Day 113. Steady-state PK parameters following administration of body-weight tiered doses approximating 10 mg/kg.

Participants with measurement at stated dose level

Steady-state PK parameters following administration of body-weight tiered doses approximating 10 mg/kg. Clearance is a pharmacokinetic parameter that describes how quickly drugs are eliminated, metabolized or distributed throughout the body.

Participants with measurement at stated dose level

The volume of distribution of drug at steady state (VSS). Steady-state PK parameters following administration of body-weight tiered doses approximating 10 mg/kg.

Participants with measurement at stated dose level

Minimum concentration (Cmin) of Abatacept 500 mg and 750 mg at given time points

Participants with measurement at timepoint

Immunogenicity was determined by measuring adult subject sera for reactivity against the whole Abatacept molecule (CTLA4Ig) and CTLA4-T (CTLA4 without the Ig regions).

All participants who received study drug (abatacept)

Mean change in surrogate marker mean ESR. A surrogate marker is an indirect measurement of effectiveness. Change from Baseline = postbaseline - baseline value.

All randomized participants who received study drug. Participants with baseline and post-baseline measurements were included, not the participants who had only baseline measurements.

Mean change in RF. A surrogate marker is an indirect measurement of effectiveness. Mean change from Baseline = postbaseline - baseline value.

All Randomized and Treated Participants. The summary was based on the last observation carried forward (LOCF) procedure. Participants with baseline and post-baseline measurements were included, not the participants who had only baseline measurements.

AE=any new untoward medical occurrence or worsening of a preexisting medical condition which does not necessarily have a causal relationship with this treatment. Related AE=relationship of certain, probable, possible, or missing. SAE=any untoward medical occurrence that at any dose: results in death, is life-threatening, requires inpatient hospitalization or causes prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, results in the development of drug dependency or drug abuse, is an important medical event.

All participants who completed the short-term period and received at least 1 infusion of abatacept during the LTE period

Positive antibody titers were identified by validated enzyme-linked immunosorbent assay results. On-treatment samples were obtained during the LTE period, and posttreatment samples were following the last infusion of study medication.

All participants who during the LTE period, received at least 1 infusion of abatacept and had at least 1 immunogenicity sample collected.

The ACR 20, ACR50, and ACR70 are based on 20%, 50% and 70% improvement, respectively, (compared with baseline values) in tender and swollen joint counts and on 20%, 50% and 70%, respectively, improvement in 3 of the remaining 5 core set measures (participant global assessment of pain, participant global assessment of disease activity, physician global assessment of disease activity, participant assessment of physical function) and 1 acute phase reactant value.

All participants who completed the ST period and received at least 1 infusion of abatacept during the LTE period. n=evaluable participants at that timepoint for that measure.

Improvement is measured by an improved response of at least 0.3 units from baseline on the HAQ-DI score. The HAQ-DI assesses a patient's level of functional ability via 20 questions in 8 categories of functioning. Patients respond on a scale from 0 (no disability) to 3 (completely disabled); total possible score=24. Higher score indicates greater disability. Change from baseline= postbaseline - baseline value.

All participants who received study drug and who were evaluable

The HAQ-DI assesses a patient's level of functional ability via 20 questions in 8 categories of functioning. Patients respond on a scale from 0 (no disability) to 3 (completely disabled); total possible score=24. Higher score indicates greater disability. Change from baseline= postbaseline - baseline value.

All participants who received study drug and who were evaluable

The SF-36 is a 36-item questionnaire used to measure Quality of Life over 8 physically and emotionally based areas: physical functioning, role limitations due to physical health, role limitations due to emotional problems, energy/fatigue, emotional well-being, social functioning, pain, and general health. Answers to each question correspond to a precoded numeric value. An aggregate percentage score is reached for each of the 8 sections and is based on answers to questions. The mean average is worked out for each section. Scores range from 0% (lowest level of functioning) to 100% (highest level of functioning, with higher score indicated increasing levels of functioning.

All participants who received study drug and who were evaluable

EULAR defines LDAS as a disease activity score as measured by c-reactive protein (DAS28-CRP) ≤3.2 and remission as DAS28-CRP <2.6

All participants who received study drug and who were evaluable

The SDAI is the sum of 5 parameters: Tender joint (TJC) and swollen joint(SJC)counts, based on a 28-joint assessment; patient global (PtGA)and physician global assessments (PGA), assessed on 0-10 cm visual analog scale (VAS), on which higher scores=greater affection due to disease activity DA); and C-reactive protein level. SDAI total score=0-86. SDAI <=3.3 indicates disease remission, >3.4 to 11=low DA, >11 to 26=moderate DA, and >26=high DA. SJC is assessed at each visit, with no swelling=0, swelling=1. TJC is assessed through identification of joints painful under pressure or to passive motion at each visit, with no tenderness=0, tenderness=1. Higher score=greater affection due to DA. CDAI is sum of 4 parameters: TJC and SJC (based on a 28-joint assessment), PtGA and PGA (assessed on 0-10 cm VAS; higher scores=greater affection due to disease activity). CDAI total score=0-76. CDAI <=2.8 indicates disease remission, >2.8 to 10=low DA, >10 to 22=moderate DA, and >22=high DA.

All participants who received study drug and who were evaluable

LDAS is defined as a Disease Activity Score C-reactive protein (DAS28-CRP) level <=3.2. Remission is defined as a DAS28-CRP level <2.6.

All participants who finished the Short-term period. n=Number of evaluable participants

Participants who completed the Short-term Period. n=Number of evaluable participants.

Participants who completed the Short-term Period. n=Number of evaluable participants.