Serum samples from all treated adult participants with active rheumatoid arthritis (RA) were screened for the presence of drug-specific antibodies using an enzyme-linked immunosorbent assay (ELISA). Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody.

Participants treated in the DBW Period with at least 1 immunogenicity result (ELISA) during DBW Period. N=Number of Participants Analyzed, n=number of participants with data for that time point

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody.

Participants treated with Placebo in DBW period who were treated in RI period and had at least 1 immunogenicity result (ELISA) during RI period. N=Number of Participants Analyzed, n=number of participants with data for that time point

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody.

All participants treated in LI Period who had at least 1 immunogenicity result (ELISA) during LI period. N=Number of Participants Analyzed, n=number of participants with data for that time point

ECL screened sera for drug-specific antibodies; immunocompetition was used to identify specific anti-Abatacept reactivity. Cytotoxic leukocyte antigen 4 (CTLA4) and Possibly Immunoglobulin (Ig) Category=reactivity against extracellular domain of human CTLA4, constant regions of human IgG1, or both (CTLA4Ig; Abatacept molecule). Ig and/or Junction (JNC) Category=reactivity against constant regions and/or hinge region of human IgG1. Drug-induced seropositivity was defined as a post-baseline titer higher than Baseline, or any post-baseline positivity if Baseline value was missing or negative.

All participants treated in Period 1 (Lead-in Period). N=Number of Participants Analyzed, n=number of participants with data for that time point

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody. Samples were obtained during treatment (TRT) visits.

All participants treated in DBW period with at least 1 immunogenicity result (ELISA) during DBW period. N=Number of Participants Analyzed, n=number of participants with data for that time point.

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody.

Participants treated in RI period with at least 1 immunogenicity result (ELISA) during RI period. N=Number of Participants Analyzed, n=number of participants with data for that time point.

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody.

These data were not summarized since there were no participants at any post visits.

ECL screened sera for drug-specific antibodies; immunocompetition was used to identify specific anti-Abatacept reactivity. Cytotoxic leukocyte antigen 4 (CTLA4) and Possibly Immunoglobulin (Ig) Category=reactivity against extracellular domain of human CTLA4, constant regions of human IgG1, or both (CTLA4Ig; Abatacept molecule). Ig and/or Junction (JNC) Category=reactivity against constant regions and/or hinge region of human IgG1. Drug-induced seropositivity was defined as a post-baseline titer higher than Baseline, or any post-baseline positivity if Baseline value was missing or negative.

All participants treated in DBW period with at least 1 immunogenicity result (ECL) during DBW period. N=Number of Participants Analyzed, n=number of participants with data for that time point

ECL screened sera for drug-specific antibodies; immunocompetition was used to identify specific anti-Abatacept reactivity. Cytotoxic leukocyte antigen 4 (CTLA4) and Possibly Immunoglobulin (Ig) Category=reactivity against extracellular domain of human CTLA4, constant regions of human IgG1, or both (CTLA4Ig; Abatacept molecule). Ig and/or Junction (JNC) Category=reactivity against constant regions and/or hinge region of human IgG1. Drug-induced seropositivity was defined as a post-baseline titer higher than Baseline, or any post-baseline positivity if Baseline value was missing or negative.

These data were not summarized since there were no participants at any post visits

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody.

All participants treated in RI period with at least 1 immunogenicity result (ELISA) during RI period N=Number of Participants Analyzed, n=number of participants with data for that time point.

ECL screened sera for drug-specific antibodies; immunocompetition was used to identify specific anti-Abatacept reactivity. Cytotoxic leukocyte antigen 4 (CTLA4) and Possibly Immunoglobulin (Ig) Category=reactivity against extracellular domain of human CTLA4, constant regions of human IgG1, or both (CTLA4Ig; Abatacept molecule). Ig and/or Junction (JNC) Category=reactivity against constant regions and/or hinge region of human IgG1. Drug-induced seropositivity was defined as a post-baseline titer higher than Baseline, or any post-baseline positivity if Baseline value was missing or negative.

All participants treated in RI period with at least 1 immunogenicity result (ECL) during RI period N=Number of Participants Analyzed, n=number of participants with data for that time point

Serum samples from Abatacept-treated adult participants with active rheumatoid arthritis (RA) were screened for the presence of drug-specific antibodies using ELISA. Immunogenicity was defined as the presence of a positive anti-abatacept or anti-CTLA4 antibody. ST was defined as the LI Period, the DBW Period, and the RI Period (Days 1-253).

All participants treated in DBW period with at least 1 immunogenicity result (ELISA) during the Short Term. N=Number of Participants Analyzed, n=number of participants with data for that time point.

ECL screened sera for drug-specific antibodies; immunocompetition was used to identify specific anti-Abatacept reactivity. Cytotoxic leukocyte antigen 4 (CTLA4) and Possibly Immunoglobulin (Ig) Category=reactivity against extracellular domain of human CTLA4, constant regions of human IgG1, or both (CTLA4Ig; Abatacept molecule). Ig and/or Junction (JNC) Category=reactivity against constant regions and/or hinge region of human IgG1. Drug-induced seropositivity was defined as a post-baseline titer higher than Baseline, or any post-baseline positivity if Baseline value was missing or negative.

All participants treated in DBW period with at least 1 immunogenicity result (ECL) during the Short Term. N=Number of Participants Analyzed, n=number of participants with data for that time point.

The DAS28 is a continuous disease measure composite of 4 variables: the number of tender joints out of 28 joints, the number of swollen joints out of 28 joints, the level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. DAS28 has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Clinically meaningful improvement= decrease in DAS28 score of ≥1.2 from baseline.

Intent To Treat Analysis Population (DBW Period, Participants randomized in DBW period who received at least 1 dose of study medication in DBW period). N=Number of Participants Analyzed, n=number of participants with data for that time point and at baseline.

DAS28 is a continuous disease measure composite of 4 variables: the number of tender joints out of 28 joints, the number of swollen joints out of 28 joints, the level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. DAS28 has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Clinically meaningful improvement= decrease in DAS28 score of ≥1.2 from baseline.

Intent To Treat Analysis Population (DBW Period, Participants randomized in DBW period who received at least 1 dose of study medication in DBW period). N=Number of Participants Analyzed, n=number of participants with data for that time point and, when relevant, at baseline.

The disability section of the full HAQ includes 20 questions to assess physical functions in 8 domains: dressing, arising, eating, walking, hygiene, reach, grip and common activities. The questions are evaluated on a 4-point scale: 0=without any difficulty, 1= with some difficulty, 2= with much difficulty, and 3= unable to do. Higher scores= greater dysfunction. A disability index was calculated by summing the worst scores in each domain and dividing by the number of domains answered. Clinically meaningful HAQ response=an improvement of at least 0.3 units from baseline in HAQ disability Index.

Intent To Treat Analysis Population (DBW Period, Participants randomized in DBW period who received at least 1 dose of study medication in DBW period). N=Number of Participants Analyzed, n=number of participants with data for that time point and at baseline.

The disability section of the full HAQ includes 20 questions to assess physical functions in 8 domains: dressing, arising, eating, walking, hygiene, reach, grip and common activities. The questions are evaluated on a 4-point scale: 0=without any difficulty, 1= with some difficulty, 2= with much difficulty, and 3= unable to do. Higher scores= greater dysfunction. A disability index was calculated by summing the worst scores in each domain and dividing by the number of domains answered. Clinically meaningful HAQ response=an improvement of at least 0.3 units from baseline in HAQ disability Index.

Intent To Treat Analysis Population (DBW Period, Participants randomized in DBW period who received at least 1 dose of study medication in DBW period). N=Number of Participants Analyzed, n=number of participants with data for that time point and at baseline.

DAS28 is a continuous disease measure composite of 4 variables: the number of tender joints out of 28 joints, the number of swollen joints out of 28 joints, the level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. DAS28 has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Clinically meaningful improvement= decrease in DAS28 score of ≥1.2 from baseline.

Participants who received at least 1 dose of study medication during LI period. N=Number of Participants Analyzed, n=number of participants with data for that time point and at baseline.

DAS28 is a continuous disease measure composite of 4 variables: the number of tender joints out of 28 joints, the number of swollen joints out of 28 joints, the level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. DAS28 has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Clinically meaningful improvement= decrease in DAS28 score of ≥1.2 from baseline.

Participants who received at least 1 dose of study medication during LI period. N=Number of Participants Analyzed, n=number of participants with data for that time point and at baseline.

DAS28 is a continuous disease measure composite of 4 variables: the number of tender joints out of 28 joints, the number of swollen joints out of 28 joints, the level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. DAS28 has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Clinically meaningful improvement= decrease in DAS28 score of ≥1.2 from baseline.

Intent To Treat Analysis Population (DBW Period, Participants randomized in DBW period who received at least 1 dose of study medication in DBW period). N=Number of Participants Analyzed, n=number of participants with data for that time point and at DBW period baseline.

A participant had an RA flare if at least 2 of the following criteria were met:

• Doubling of tender and swollen joint count from Day 78
• Increase in DAS28-CRP score ≥ 1.2 from Day 78
• Prematurely discontinued from Double-blind Withdrawal Period (Period 2) and continued to Re-introduction Period (Period 3)

Intent To Treat Analysis Population (DBW Period, Participants randomized in DBW period who received at least 1 dose of study medication in DBW period). N=Number of Participants Analyzed, n=number of participants with data for that time point.

DAS28 is a continuous disease measure composite of 4 variables: the number of tender joints out of 28 joints, the number of swollen joints out of 28 joints, the level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. DAS28 has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Clinically meaningful improvement= decrease in DAS28 score of ≥1.2 from baseline.

Participants who received at least 1 dose of study medication during RI period. N=Number of Participants Analyzed, n=number of participants with data for that time point and at RI period baseline.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with this treatment. 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 development of drug dependency or drug abuse, is an important medical event.

Participants who received at least 1 dose of study medication during LI period

AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections and opportunistic infections; autoimmune disorders; malignancies; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion), peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion),local injection site reaction (pre-specified AEs occurring at the site of SC injection)and systemic injection site reactions (pre-specified systemic AEs such as hypersensitivity reactions occurring within 24 hours of SC injection)

Participants who received at least 1 dose of study medication during LI period

Upper Normal Limit (ULN), Lower Normal Limit (LLN), Baseline (BL). Marked abnormality criteria are: Hemoglobin (HGB): >3 g/dL decrease from BL; Hematocrit: <0.75 * BL; Erythrocytes: <0.75 * BL; Platelets (PLT): <0.67 * LLN/>1.5 * ULN, or if BL < LLN then use <0.5 * BL and <100,000 mm^3; Leukocytes: <0.75 * LLN/ >1.25 * ULN, or if BL<LLN then use <0.8 * BL or >ULN, or if BL>ULN then use >1.2 * BL or <LLN; neutrophils+bands: <1.0 * 10^3 cells/ microliter (uL); eosinophils: >0.750 * 10^3 cells/uL; basophils: > 400 mm^3; monocytes: >2000 mm^3; lymphocytes: <0.750 * 10^3 cells/uL/ >7.50 * 10^3 cells/uL.

Participants who received at least 1 dose of study medication during LI period.

Marked abnormality criteria: Alkaline phosphatase (ALP): >2* ULN, or if BL>ULN then use >3* BL; aspartate aminotransferase (AST): >3* ULN, or if BL>ULN then use >4* BL; alanine aminotransferase (ALT): >3* ULN, or if BL>ULN then use >4* BL; G-Glutamyl transferase (GGT): >2* ULN, or if BL>ULN then use >3* BL; Bilirubin: >2* ULN, or if BL>ULN then use >4* BL; blood urea nitrogen (BUN): >2* BL; creatinine: >1.5* BL

Participants who received at least 1 dose of study medication during LI period.

Marked abnormality criteria: Sodium (Na): <0.95*LLN/ >1.05*ULN, or if BL<LLN then use <0.95* BL or >ULN, or if BL>ULN then use>1.05* BL or <LLN; potassium (K): <0.9* LLN/>1.1*ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; (Cl): <0.9* LLN/>1.1* ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; calcium (Ca): <0.8* LLN/>1.2* ULN, or if BL<LLN then use <0.75* BL or >ULN, or if BL>ULN then use>1.25* BL or <LLN; phosphorous (P): <0.75* LLN/ >1.25* ULN, or if BL<LLN then use 0.67* BL or >ULN, or if BL>ULN then use>1.33* BL or \

Participants who received at least 1 dose of study medication during LI period.

MA criteria: serum glucose (Glu): <65 mg/dL/>220 mg/dL;fasting serum Glu: <0.8* LLN/>1.5*upper limits of normal (ULN),or if BL< lower limits of normal (LLN) then use 0.8*BL or > upper limits of normal (ULN),or if BL>ULN then use >2.0*BL or <LLN;total protein: <0.9*LLN/>1.1*ULN,or if BL<LLN then use <0.9*BL or >ULN,or if BL>UNL then use >1.1*BL or <LLN; albumin: <0.9*LLN,or if BL<LLN then use <0.75 BL;uric acid: >1.5*ULN,or if BL>ULN then use >2*BL. Urinalysis: Urine protein,urine Glu,urine blood,leukocyte esterase,Red Blood Cells (RBCs), White Blood Cells (WBCs):Use ≥2 when BL value missing or when pre-dose=0 or 0.5; use ≥3 when pre-dose=1, use ≥4 when pre-dose=2 or 3

Participants who received at least 1 dose of study medication during LI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during LI period.

Blood pressure was taken in participants while seated and measured in millimeters of mercury (mmHg). Pressures were assessed at screening, at baseline on Day 1 prior to infusion of IV abatacept, at 30 and 60 minutes after IV infusion of abatacept on Day 1, and at all office visits prior to SC injection of abatacept. Vital signs were also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication during LI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point during the LI period.

Heart rate was taken in participants while seated and measured in beats per minute (bpm). Heart rate was assessed at screening, at baseline on Day 1 prior to infusion of IV abatacept, at 30 and 60 minutes after IV infusion of abatacept on Day 1, and at all office visits prior to SC injection of abatacept. Heart rate was also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication during LI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point during the LI period.

Temperature was taken in participants while seated and measured in degrees celsius. Temperature was assessed at screening, at baseline on Day 1 prior to infusion of IV abatacept, at 30 and 60 minutes after IV infusion of abatacept on Day 1, and at all office visits prior to SC injection of abatacept. Temperature was also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication during LI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point during the LI period.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with this treatment. 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 development of drug dependency or drug abuse, is an important medical event.

Participants who received at least 1 dose of study medication in DBW period

AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections and opportunistic infections; autoimmune disorders; malignancies; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion), peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion),local injection site reaction (pre-specified AEs occurring at the site of SC injection)and systemic injection site reactions (pre-specified systemic AEs such as hypersensitivity reactions occurring within 24 hours of SC injection)

Participants who received at least 1 dose of study medication in DBW period

Marked abnormality criteria are: Hemoglobin (HGB): >3 g/dL decrease from BL; Hematocrit: <0.75 * BL; Erythrocytes: <0.75 * BL; Platelets (PLT): <0.67 * LLN/>1.5 * ULN, or if BL < LLN then use <0.5 * BL and <100,000 mm^3; Leukocytes: <0.75 * LLN/ >1.25 * ULN, or if BL<LLN then use <0.8 * BL or >ULN, or if BL>ULN then use >1.2 * BL or <LLN; neutrophils+bands: <1.0 * 10^3 cells/uL; eosinophils: >0.750 * 10^3 cells/uL; basophils: > 400 mm^3; monocytes: >2000 mm^3; lymphocytes: <0.750 * 10^3 cells/uL/ >7.50 * 10^3 cells/uL.

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the DBW period.

Marked abnormality criteria: Alkaline phosphatase (ALP): >2* ULN, or if BL>ULN then use >3* BL; aspartate aminotransferase (AST): >3* ULN, or if BL>ULN then use >4* BL; alanine aminotransferase (ALT): >3* ULN, or if BL>ULN then use >4* BL; G-Glutamyl transferase (GGT): >2* ULN, or if BL>ULN then use >3* BL; Bilirubin: >2* ULN, or if BL>ULN then use >4* BL; blood urea nitrogen (BUN): >2* BL; creatinine: >1.5* BL

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the DBW period.

Marked abnormality criteria: Sodium (Na): <0.95*LLN/ >1.05*ULN, or if BL<LLN then use <0.95* BL or >ULN, or if BL>ULN then use>1.05* BL or <LLN; potassium (K): <0.9* LLN/>1.1*ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; (Cl): <0.9* LLN/>1.1* ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; calcium (Ca): <0.8* LLN/>1.2* ULN, or if BL<LLN then use <0.75* BL or >ULN, or if BL>ULN then use>1.25* BL or <LLN; phosphorous (P): <0.75* LLN/ >1.25* ULN, or if BL<LLN then use 0.67* BL or >ULN, or if BL>ULN then use>1.33* BL or \

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the DBW period.

MA criteria: serum glucose (Glu): <65 mg/dL/>220 mg/dL;fasting serum Glu: <0.8* LLN/>1.5*ULN,or if BL<LLN then use 0.8*BL or >ULN,or if BL>ULN then use >2.0*BL or <LLN;total protein: <0.9*LLN/>1.1*ULN,or if BL<LLN then use <0.9*BL or >UNL,or if BL>UNL then use >1.1*BL or <LLN; albumin: <0.9*LLN,or if BL<LLN then use <0.75 BL;uric acid: >1.5*ULN,or if BL>ULN then use >2*BL. Urinalysis (Urine protein,urine Glu,urine blood,leukocyte esterase,Red Blood Cells [RBCs], White Blood Cells [WBCs]):Use ≥2 when BL value missing or when pre-dose=0 or 0.5; use ≥3 when pre-dose=1, use ≥4 when pre-dose=2 or 3

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the DBW period.

Blood pressures were taken in participants while seated, just prior to study drug injection, and measured in millimeters of mercury (mmHg).

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

Heart Rate was taken in participants while seated, just prior to study drug injection, and measured in beats per minute (bpm)

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

Participants were seated and temperature taken just prior to study drug injection.

Participants who received at least 1 dose of study medication in DBW period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with this treatment. 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 development of drug dependency or drug abuse, is an important medical event.

Participants who received at least 1 dose of study medication in RI period.

AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections and opportunistic infections; autoimmune disorders; malignancies; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion), peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion),local injection site reaction (pre-specified AEs occurring at the site of SC injection)and systemic injection site reactions (pre-specified systemic AEs such as hypersensitivity reactions occurring within 24 hours of SC injection)

Participants who received at least 1 dose of study medication in RI period.

Marked abnormality criteria are: Hemoglobin (HGB): >3 g/dL decrease from BL; Hematocrit: <0.75 * BL; Erythrocytes: <0.75 * BL; Platelets (PLT): <0.67 * LLN/>1.5 * ULN, or if BL < LLN then use <0.5 * BL and <100,000 mm^3; Leukocytes: <0.75 * LLN/ >1.25 * ULN, or if BL<LLN then use <0.8 * BL or >ULN, or if BL>ULN then use >1.2 * BL or <LLN; neutrophils+bands: <1.0 * 10^3 cells/uL; eosinophils: >0.750 * 10^3 cells/uL; basophils: > 400 mm^3; monocytes: >2000 mm^3; lymphocytes: <0.750 * 10^3 cells/uL/ >7.50 * 10^3 cells/uL.

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the RI period.

Marked abnormality criteria: Alkaline phosphatase (ALP): >2* ULN, or if BL>ULN then use >3* BL; aspartate aminotransferase (AST): >3* ULN, or if BL>ULN then use >4* BL; alanine aminotransferase (ALT): >3* ULN, or if BL>ULN then use >4* BL; G-Glutamyl transferase (GGT): >2* ULN, or if BL>ULN then use >3* BL; Bilirubin: >2* ULN, or if BL>ULN then use >4* BL; blood urea nitrogen (BUN): >2* BL; creatinine: >1.5* BL

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the RI period.

Marked abnormality criteria: Sodium (Na): <0.95*LLN/ >1.05*ULN, or if BL<LLN then use <0.95* BL or >ULN, or if BL>ULN then use>1.05* BL or <LLN; potassium (K): <0.9* LLN/>1.1*ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; (Cl): <0.9* LLN/>1.1* ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; calcium (Ca): <0.8* LLN/>1.2* ULN, or if BL<LLN then use <0.75* BL or >ULN, or if BL>ULN then use>1.25* BL or <LLN; phosphorous (P): <0.75* LLN/ >1.25* ULN, or if BL<LLN then use 0.67* BL or >ULN, or if BL>ULN then use>1.33* BL or \

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the RI period.

MA criteria: serum glucose (Glu): <65 mg/dL/>220 mg/dL;fasting serum Glu: <0.8* LLN/>1.5*ULN,or if BL<LLN then use 0.8*BL or >ULN,or if BL>ULN then use >2.0*BL or <LLN;total protein: <0.9*LLN/>1.1*ULN,or if BL<LLN then use <0.9*BL or >UNL,or if BL>UNL then use >1.1*BL or <LLN; albumin: <0.9*LLN,or if BL<LLN then use <0.75 BL;uric acid: >1.5*ULN,or if BL>ULN then use >2*BL. Urinalysis (Urine protein,urine Glu,urine blood,leukocyte esterase,Red Blood Cells [RBCs], White Blood Cells [WBCs]):Use ≥2 when BL value missing or when pre-dose=0 or 0.5; use ≥3 when pre-dose=1, use ≥4 when pre-dose=2 or 3

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the RI period.

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

Participants who received at least 1 dose of study medication in RI period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

Pharmacokinetics is a branch of pharmacology concerned with the rate at which drugs are absorbed, distributed, metabolized, and eliminated by the body. Cmin=minimum observed plasma concentration of single-dose abatacept. Cmin for each participant was listed by study visit and immunogenicity status (seropositive vs. seronegative) was determined by ELISA.

Participants treated during the RI Period with at least 1 immunogenicity result (ELISA) during this period. N=Number of Participants Analyzed, n=number of participants with data for that time point

Pharmacokinetics is a branch of pharmacology concerned with the rate at which drugs are absorbed, distributed, metabolized, and eliminated by the body. Cmin=minimum observed plasma concentration of single-dose abatacept. Cmin for each participant was listed by study visit and immunogenicity status (seropositive vs. seronegative) was determined by ECL.

Participants treated in RI period with at least 1 immunogenicity result (ECL) during RI period. N=Number of Participants Analyzed, n=number of participants with data for that time point

Venous blood was collected and tested for anti-nuclear antibodies, anti-dsDNA antibodies, and rheumatoid factor. ANA were detected by means of immunofluorescent antibodies. An anti-DNA radioimmunoassay was used for detection of anti-dsDNA antibodies (Diagnostic Products Corporation). RF was measured by an immunoturbidimetric assay (Roche Tina-Quant). Determinations of antibody or RF status were made at baseline and Day 253.

Participants treated in DBW period with at least 1 immunogenicity result (immunofluorescence, radioimmunoassay, or immunoturbidimetry) during this period. N=Number of Participants Analyzed, n=number of participants with data for that time point

DAS28=continuous disease measure composite of 4 variables: number of tender joints out of 28, number of swollen joints out of 28, level of serum reactant protein CRP, and participant global assessment of disease activity measured on a visual analogue scale. DAS28-CRP has numeric thresholds defining high disease activity (> 5.1), low disease activity (≤ 3.2) and remission (< 2.6). Last day of ST is Day 85 for Period I Nonresponders and Day 253 for ST Completers . Data are not available(NA) for the period from Day 113 to Day 253 for Period 1 non-responders. Note: Day 85 and Day 337 assessments for the Period I Nonresponder cohort in fact represent consecutive assessments with an interval of approximately 1 month. For Period I nonresponder, study days do not represent treatment days. Study Day 337 for a Period I nonresponder actually corresponds to that participant's Treatment Day 169.

The LTE Treated Population contained those participants who received at least 1 dose of study medication during the LTE. Participants in LTE either completed Period 3 or were nonresponders at the end of Period 1. n=number of participants with both baseline and post-baseline measurements.

DAS28=continuous disease measure composite of 4 variables: number of tender joints out of 28, number of swollen joints out of 28, level of serum reactant protein CRP, and participant global assessment of disease activity measured on a visual analogue scale. Clinical remission=DAS28-CRP score<2.6. Percent=Number of participants meeting remission divided by number of participants evaluated. Last day of ST is Day 85 for Period I Nonresponders and Day 253 for ST Completers . Data are not available (NA) for the period from Day 113 to Day 253 for Period 1 non-responders. Note: Day 85 and Day 337 assessments for the Period I Nonresponder cohort in fact represent consecutive assessments with an interval of approximately 1 month. For Period I nonresponder, study days do not represent treatment days. Study Day 337 for a Period I nonresponder actually corresponds to that participant's Treatment Day 169.

The LTE Treated Population contained those participants who received at least 1 dose of study medication during the LTE. Participants in LTE either completed Period 3 or were nonresponders at the end of Period 1. n= number of participants evaluated at each specific timepoint

DAS28:continuous disease measure composite of 4 variables: number of tender joints out of 28 joints, number of swollen joints out of 28 joints, level of the serum reactant protein CRP, and participant global assessment of disease activity measure on a visual analogue scale. Low disease activity score: ≤ 3.2. Percent=Number of participants with Low Disease Activity divided by number of participants evaluated. Last day of ST is Day 85 for Period I Nonresponders and Day 253 for ST Completers . Data are not available(NA) for the period from Day 113 to Day 253 for Period 1 non-responders. Note: Day 85 and Day 337 assessments for the Period I Nonresponder cohort in fact represent consecutive assessments with an interval of approximately 1 month. For Period I nonresponder, study days do not represent treatment days. Study Day 337 for a Period I nonresponder actually corresponds to that participant's Treatment Day 169.

The LTE Treated Population contained those participants who received at least 1 dose of study medication during the LTE. Participants in LTE either completed Period 3 or were nonresponders at the end of Period 1.

The disability section of the full HAQ includes 20 questions to assess physical functions in 8 domains: dressing, arising, eating, walking, hygiene, reach, grip and common activities. The questions are evaluated on a 4-point scale: 0=without any difficulty, 1= with some difficulty, 2= with much difficulty, and 3= unable to do. Higher scores= greater dysfunction. A disability index (DI) was calculated by summing the worst scores in each domain and dividing by the number of domains answered. Clinically meaningful HAQ response=an improvement of at least 0.3 units from baseline in HAQ DI. Percent=number of participants with HAQ response divided by number of participants in the analysis. Since Period I Non-responders proceeded directly to the LTE at the end of Period I (Day 85), study days do not represent treatment days.

The LTE Treated Population contained those participants who received at least 1 dose of study medication during the LTE. Participants in LTE either completed Period 3 or were non-responders at the end of Period 1. n= number of participants with data who were evaluated

Serum samples from Abatacept-treated adult participants with active RA were screened for the presence of drug-specific antibodies using electrochemiluminescence (ECL). The percent of participants with a positive abatacept induced immunogenicity response against cytotoxic T-lymphocyte antigen 4 (CTLA4) and possibly immunoglobulin (Ig), or against Ig and/or Junction Region was calculated by number of participants with a positive response divided by number of participants evaluated. Overall for on-treatment includes treatment visits on Days 337, 365, 449, 533, 617, 729, 813, 897, 981, 1093, 1177, 1261, 1457, 1625, 1821, and 1989.

All participants treated in LTE period with at least 1 immunogenicity result (ECL) during LTE period. n=number of participants evaluated.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with this treatment. 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 development of drug dependency or drug abuse, is an important medical event. SAEs include hospitalizations for elective surgical procedures.All deaths reported during the LTE including those that occurred > 56 days after the last dose. Related AE or SAE defined as AE or SAE with Certain, Probable, Possible, or Missing relationship to study medication. All participants who completed the ST period could enter the open label LTE on Day 253; LI Period 1 non-responders could directly enter the LTE.

Participants who received at least 1 dose of study medication in LTE period

AEs of special interest in LTE are those AEs that may be associated with the use of immunomodulatory drugs, including all infections and opportunistic infections; autoimmune disorders; malignancies, local injection site reaction (pre-specified AEs occurring at the site of SC injection) and systemic injection site reactions (pre-specified systemic AEs such as hypersensitivity reactions occurring within 24 hours of SC injection)

Participants who received at least 1 dose of study medication in LTE period

Marked abnormality criteria are: Hemoglobin (HGB): >3 g/dL decrease from BL; Hematocrit: <0.75 * BL; Erythrocytes: <0.75 * BL; Platelets (PLT): <0.67 * LLN/>1.5 * ULN, or if BL < LLN then use <0.5 * BL and <100,000 mm^3; Leukocytes: <0.75 * LLN/ >1.25 * ULN, or if BL<LLN then use <0.8 * BL or >ULN, or if BL>ULN then use >1.2 * BL or <LLN; neutrophils+bands: <1.0 * 10^3 cells/uL; eosinophils: >0.750 * 10^3 cells/uL; basophils: > 400 mm^3; monocytes: >2000 mm^3; lymphocytes: <0.750 * 10^3 cells/uL/ >7.50 * 10^3 cells/uL.

Participants who received at least 1 dose of study medication in LTE period and who had data available during the LTE period.

Marked abnormality criteria: Alkaline phosphatase (ALP): >2* ULN, or if BL>ULN then use >3* BL; aspartate aminotransferase (AST): >3* ULN, or if BL>ULN then use >4* BL; alanine aminotransferase (ALT): >3* ULN, or if BL>ULN then use >4* BL; G-Glutamyl transferase (GGT): >2* ULN, or if BL>ULN then use >3* BL; Bilirubin: >2* ULN, or if BL>ULN then use >4* BL; blood urea nitrogen (BUN): >2* BL; creatinine: >1.5* BL

Participants who received at least 1 dose of study medication in LTE period and who had data available during the LTE period.

Marked abnormality criteria: Sodium (Na): <0.95*LLN/ >1.05*ULN, or if BL<LLN then use <0.95* BL or >ULN, or if BL>ULN then use>1.05* BL or <LLN; potassium (K): <0.9* LLN/>1.1*ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; (Cl): <0.9* LLN/>1.1* ULN, or if BL<LLN then use <0.9* BL or >ULN, or if BL>ULN then use>1.1* BL or <LLN; calcium (Ca): <0.8* LLN/>1.2* ULN, or if BL<LLN then use <0.75* BL or >ULN, or if BL>ULN then use>1.25* BL or <LLN; phosphorous (P): <0.75* LLN/ >1.25* ULN, or if BL<LLN then use 0.67* BL or >ULN, or if BL>ULN then use>1.33* BL or \

Participants who received at least 1 dose of study medication in LTE period and who had data available during the LTE period.

MA criteria: serum glucose (Glu): <65 mg/dL/>220 mg/dL;fasting serum Glu: <0.8* LLN/>1.5*ULN,or if BL<LLN then use 0.8*BL or >ULN,or if BL>ULN then use >2.0*BL or <LLN;total protein: <0.9*LLN/>1.1*ULN,or if BL<LLN then use <0.9*BL or >UNL,or if BL>UNL then use >1.1*BL or <LLN; albumin: <0.9*LLN,or if BL<LLN then use <0.75 BL;uric acid: >1.5*ULN,or if BL>ULN then use >2*BL. Urinalysis (Urine protein,urine Glu,urine blood,leukocyte esterase,Red Blood Cells [RBCs], White Blood Cells [WBCs]):Use ≥2 when BL value missing or when pre-dose=0 or 0.5; use ≥3 when pre-dose=1, use ≥4 when pre-dose=2 or 3

Participants who received at least 1 dose of study medication in LTE period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available during the LTE period.

During LTE, blood pressure was taken in participants while seated, measured in millimeters of mercury (mmHg) and were assessed at all office visits prior to SC injection of abatacept. Vital signs were also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication in LTE period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

During LTE, blood pressure was taken in participants while seated, measured in millimeters of mercury (mmHg) and were assessed at all office visits prior to SC injection of abatacept. Vital signs were also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication in LTE period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

During LTE, heart rate was taken in participants while seated, measured in beats per minute (bpm) and was assessed at all office visits prior to SC injection of abatacept. Heart rate was also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication in LTE period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.

During LTE, temperature was taken in participants while seated, measured in degrees celsius and was assessed at all office visits prior to SC injection of abatacept. Temperature was also assessed 7 days after the last injection of abatacept for participants who were withdrawn prematurely.

Participants who received at least 1 dose of study medication in LTE period. N=Number of Participants Analyzed. n (when indicated)= number of participants with data available at that time point.