The ACR 50 definition of improvement is a 50% improvement over baseline in tender and swollen joint counts (#1 and #2) and a 50% improvement in 3 of the 5 remaining core data 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 acute phase reactant value). Baseline value is the last assessment taken prior to first dose of single-blind study medication.

The number of participants who achieve IMACS DOI (International Myositis Assessment and Clinical Studies definition of improvement) without rescue medication at week 24. The IMACS DOI is: An improvement of \>/= 20% from baseline in 3 IMACS core measures, no more than 2 IMACS core measure scores worsen by \>/= 25% from baseline, and no more than 2 IMACS core measure scores worsen by \>/= 25% from baseline. IMACS core measures are: Physician Global Assessment of Disease Activity (PGA), Patient (Subject) Global Assessment of Disease Activity (SGA), Manual Muscle Test (MMT-8), Health Assessment Questionnaire-Disability Index (HAQ-DI), Muscle Enzyme levels, Myositis Disease Activity Assessment Tool (MDAAT) Extramuscular Global Activity.

The EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) total score is calculated as the sum of scores for activity level for each domain. The EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) Scoring Algorithm. Domain: (Score) Constitutional: (No=0, Low=3, Moderate=6) Lymphadenopathy: (No=0, Low=4, Moderate=8, High=12) Glandular: (No=0, Low=2, Moderate=4) Articular: (No=0, Low=2, Moderate=4, High=6) Cutaneous: (No=0, Low=3, Moderate=6, High=9) Pulmonary: (No=0, Low=5, Moderate=10, High=15) Renal: (No=0, Low=5, Moderate=10, High=15) Muscular: (No=0, Low=6, Moderate=12, High=18) Peripheral Nervous System (PNS): (No=0, Low=5, Moderate=10, High=15) Central Nervous System (CNS): (No=0, Moderate=10, High=15) Haematological: (No=0, Low=2, Moderate=4, High=6) Biological: (No=0, Low=1, Moderate=2) (No = No Disease Activity (DA), Low = Low DA, Moderate = Moderate DA, High = High DA) Overall score, which can range from 0 to 123, a higher score indicates more disease activity

Simple Disease Activity Index (SDAI) is calculated using the following formula: TJC + SJC + PGA + MDGA + CRP (TJC = number of painful joints from 28 joints, SJC = number of swollen joints from 28 joints, PGA = patient global assessment on a visual analog scale 0-10 cm, MDGA = physician global assessment on a visual analog scale 0-10 cm, and CRP = c-reactive protein in mg/dL) SDAI Remission is defined as SDAI \<= 3.3. Using a logistic regression model that includes treatment arm, randomization stratification factor, and baseline SDAI as continuous variable and point estimate of adjusted ORs, corresponding 95% CI and p-value was provided. SDAI total score range: 0 to 86. SDAI \<= 3.3 indicates disease remission and SDAI \>26 = high disease activity.

Treatment failure will be defined as relapse, disease worsening, or failure to achieve a Birmingham Vasculitis Activity Score for Wegener's Granulomatosis (BVAS/WG) = 0 or 1 by 6 months. Relapse will be defined as any of the following after remission: an increase in BVAS/WG, development of a new BVAS/WG item, or symptoms/signs of GPA that cannot be attributed to any cause other than GPA and that requires institution or dosage increase of prednisone. Disease worsening will be defined as any of the following prior to remission: an increase in BVAS/WG, development of a new BVAS/WG item, or symptoms/signs of GPA that cannot be attributed to any cause other than GPA and that requires institution or dosage increase of prednisone.

Trough concentration of abatacept (reported as geometric mean of Cmin) in all pharmacokinetic (PK)-evaluable participants. Cmin is reported in microgram per milliliter (µg/mL). Desired target therapeutic Cmin should be \>= 10 µg/mL.

American College of Rheumatology (ACR) pediatric (PED) 30 response was defined as '≥30% improvement' and '≥3 of the 6 Juvenile Idiopathic Arthritis (JIA) core set' and ≥30% worsening in not more than 1 of the 6 JIA core set variables. JIA core set variables defined as the number of active joints, number of joints with Limit of Motion (LOM), physician's global assessment of disease severity, patient global assessment of overall well being, parent assessment of physical function, and acute phase reactant value. A non-responder imputation was applied.

The American College of Rheumatology (ACR) 20 definition of improvement is a 20% improvement over baseline in tender and swollen joint counts and a 20% improvement in 3 of the 5 remaining core data set measures (participant global assessment of pain, participant global assessment of disease activity, physician global assessment of disease activity, participant assessment of physical function, acute phase reactant value). The number of ACR 20 responders was divided by the number of treated participants and expressed as a percentage. Early escape participants, and participants with missing data at day 169 were imputed as non-responders.

Abatacept SC was self-administered with a prefilled syringe every 7 days for the first 4 weeks until Day 29; Blood samples for PK were taken pre-dose (0 hour) on Days 29 and 113. Serum concentrations of abatacept were analyzed using a validated enzyme-linked immunosorbent assay (ELISA). Steady-state trough observed concentration in serum (Cminss) was measured in micrograms/milliliter (μg/mL). Adjusted geometric mean and 90% confidence interval (CI) are presented.

DAS28-CRP remission defined as \<2.6; TP=treatment phase; WP=withdrawal phase. The DAS 28-CRP is a measure of disease activity in rheumatoid arthritis (RA) that assesses the 28 joints RA commonly affects; the score includes the number of tender and swollen joints (out of 28), CRP level (a measure of inflammation in the blood), and the patient's global assessment of health (ranging from very good to very bad). These measures are then fed into a complex mathematical formula to produce the overall DAS (a score greater than 5.1 implies active disease; less than 3.2, well controlled disease; and less than 2.6, remission.)

Proportion(%)=number of participants meeting criteria (n) divided by number of participants who received drug (N). The ACR score indicates degree of improvement in a patient's rheumatoid arthritis (RA), based on guidelines set forth by the ACR and represents a percentage. To qualify a ACR20 score, patient must have \>=20% fewer tender joints and \>=20% fewer swollen joints and show 20% improvement from baseline in at least 3 of: patient overall assessment of his/her RA, physician global assessment of the patient's RA, patient self-assessment of pain, patient self-assessment of physical functioning, and results of an erythrocyte sedimentation rate or C-reactive protein (CRP) test (to assess inflammation). Baseline was Day 1. Randomization was stratified using screening Disease Activity Score-28 (DAS28) CRP, a composite of 4 variables: number of tender joints/28, number of swollen joints/28, CRP in mg/L and participant assessment of disease activity with visual analogue scale.

LOCF=last observation carried forward. PDUS assessed the degree of synovial inflammation of the MCP joints (2nd to 5th) of both hands and was performed at approximately the same time of day for each participant. Total PDUS scores are independent of the presence and grade of joint effusion and are evaluated as follows: Grade 0 or normal=normal joint (no synovial hypertrophy, no Doppler signal); Grade 1 or minimal=minimal synovitis (minimal synovial hypertrophy, with ≤Grade 1 Doppler signal); Grade 2 or moderate=moderate synovitis (moderate synovial hypertrophy with ≤Grade 2 Doppler signal or minimal synovial hypertrophy and Grade 2 Doppler signal; Grade 3 or severe=severe synovitis (severe synovial hypertrophy with ≤Grade 3 Doppler signal or minimal or moderate synovial hypertrophy and Grade 3 Doppler signal). Each joint is rated 1 to 3, for a total possible score ranging from 8 to 24 (8\*1, 8\*3) for 2 hands. Higher grade/score=more severe disease. Change=score Day x - baseline score.

MCP=metacarpophalangeal; PDUS=power Doppler ultrasonography. Time point at which early signs of Global PDUS improvement were observed=earliest time point for which 0 was not included in the 95% confidence interval for the mean changes from baseline in Global PDUS (MCP 2-5) score at that and all later time points. Total PDUS scores are independent of the presence and grade of joint effusion: Grade (Gr) 0 or normal=normal joint (no synovial hypertrophy \[SH\], no Doppler signal); Gr 1 or minimal=minimal synovitis (minimal SH, with ≤Gr 1 Doppler signal); Gr 2 or moderate=moderate synovitis (moderate SH, with ≤Gr 2 Doppler signal or minimal SH and grade 2 Doppler signal); Gr 3 or severe=severe synovitis (severe SH with ≤Gr 3 Doppler signal or minimal or moderate SH and Gr 3 Doppler signal). Each joint is rated 1 to 3, for a total possible score ranging from 8 to 24 (8\*1, 8\*3) for the 2 hands. Higher Gr/score=more severe disease.

An AE is a new or worsening illness, sign, or symptom or a clinically significant abnormal laboratory test result occurring during the study, regardless of causality, and noted by the investigators. Systemic injection reaction occurring ≤ 24 hours after dosing.

An AE is a new or worsening illness, sign, or symptom or a clinically significant abnormal laboratory test result occurring during the study, regardless of causality, and noted by the investigators.

LLN=lower limit of normal; ULN=upper limit of normal; preRx=pretreatment. Marked abnormality criteria: Hemoglobin (g/dL) \>3 decrease from preRx. Hematocrit (%)\<0.75\*preRx. Erythrocytes (\*10\^6 c/uL) \<0.75\*preRx. Platelet count (\*10\^9 c/L) \<0.67\*LLN or 1.5\*ULN or, if preRx\<LLN, use \<0.5\*preRx and \<100,000 mm\^3. Leukocytes (\*10\^3 c/uL) \<0.75\*LLN or \>1.25\*ULN or, if preRx\<LLN, use \<0.8\*preRx or \>ULN or, if preRx\>ULN, use \>1.2\*preRx or \<LLN. Eosinophils \>0.750\*10\^3 c/uL. Lymphocytes \<0.750\*10\^3 c/uL or \>7.50\*10\^3 c/uL.

LLN=lower limit of normal; ULN=upper limit of normal; preRx=pretreatment. Marked abnormality criteria: Alkaline phosphatase (U/L) \>2\*ULN or if preRx\>ULN, use 3\*preRx. Alanine aminotransferase (U/L)\>3\*ULN or if preRx\>ULN, use \>4\*preRx. G-glutamyl transferase (U/L)\>2\*ULN or if preRx\>ULN, use \>3\*preRx. Blood urea nitrogen (mg/dL)\>2\*preRx. Creatinine (mg/dL)\>1.5\*preRx.

LLN=lower limit of normal; ULN=upper limit of normal; preRx=pretreatment. Sodium: \<0.95\*LLN or \>1.05\*ULN or if preRx\<LLN, \<0.95\*preRx or \>ULN, or if preRx\>ULN,\>1.05\*preRx or \<LLN. Potassium,serum: \<0.9\*LLN or \>1.1\*ULN or if preRx\<LLN, use \<0.9\*preRx or \>ULN or if preRx\>ULN, 1.1\*preRx or \<LLN. Phosphorus: 0.75\*LLN or 1.25\*ULN or, if preRx\<LLN, \<0.67\*preRx or \>ULN or, if preRx\>ULN, \<LLN.

LLN=lower limit of normal; ULN=upper limit of normal; preRX=pretreatment. Criteria for marked abnormality: .

preRX=pretreatment. For all values analyzed (protein, urine; glucose, urine; blood, urine: leukocyte esterase, urine; white blood cells, urine; red blood cells, urine): If missing preRx, use \>=2 or, if value \>= 4, or if preRx=0 or 0.5, use \>=2 or, if preRx= 1, use \>=3 or, if preRx=2 or 3, use \>=4.

AEs of special interest are AEs that may be associated with the use of immunomodulatory drugs, such as infections, malignancies, autoimmune disorders, and injection reactions (defined as local injection site reactions and systemic injection reactions occurring within 24 hours of subcutaneous injection).

BP was measured after the patient had been seated quietly for at least 5 minutes and recorded during the screening visit, during every office visit prior to administration of subcutaneous injections, and at study discharge or 7 days after the last dose for patients who terminated early.

Heart rate was measured after the patient had been seated quietly for at least 5 minutes and recorded during the screening visit, during every office visit prior to administration of subcutaneous injections, and at study discharge or 7 days after the last dose for patients who terminated early.

Temperature was measured after the patient had been seated quietly for at least 5 minutes and recorded during the screening visit, during every office visit prior to administration of subcutaneous injections, and at study discharge or 7 days after the last dose for patients who terminated early.

The ACR 20 definition of improvement is a 20% improvement from baseline in the number of tender and swollen joints, and a 20% improvement from baseline 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 acute phase reactant value (C-reactive protein).

Serum samples from all treated adult participants with active rheumatoid arthritis who were from the Anti-TNF failure population were screened for the presence of drug-specific antibodies using Enzyme Linked Immunoabsorbant Assay (ELISA). The number of participants who had the presence of anti-abatacept antibodies or anti-CTLA-4 antibodies present in their serum are summarized.

ELISA is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum. For anti-abatacept antibody ELISA, a sample was considered seropositive if it had a titer of 400 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 400. A sample was considered positive in CTLA4-T antibody ELISA if it had a titer of 25 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 25.

ELISA is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum. For anti-abatacept antibody ELISA, a sample was considered seropositive if it had a titer of 400 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 400. A sample was considered positive in CTLA4-T antibody ELISA if it had a titer of 25 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 25.

The ECL (MSD) assay method is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum. It is more sensitive and has a higher drug tolerance than ELISA method. For the anti-abatacept antibody ECL (MSD) assay, a sample was considered seropositive if it had a titer of 10 or greater and if immunodepletion was observed with abatacept, or abatacept and CTLA4-T. Those responses that were not positive in the initial screen or were not confirmed to be positive based on immunodepletion were reported as seronegative and were assigned a value of \< 10.

ELISA is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum. For anti-abatacept antibody ELISA, a sample was considered seropositive if it had a titer of 400 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 400. A sample was considered positive in CTLA4-T antibody ELISA if it had a titer of 25 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 25.

The ECL (MSD) assay method is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum. It is more sensitive and has a higher drug tolerance than the ELISA method. For anti-abatacept antibody ECL (MSD) assay, a sample was considered seropositive if it had a titer of 10 or greater and if immunodepletion was observed with abatacept, or abatacept and CTLA4-T. Those responses that were not positive in the initial screen or were not confirmed to be positive based on immunodepletion were reported as seronegative and were assigned a value of \< 10.

ELISA is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum. For anti-abatacept antibody ELISA, a sample was considered seropositive if it had a titer of 400 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 400. A sample was considered positive in CTLA4-T antibody ELISA if it had a titer of 25 or greater and if immunodepletion was observed. The responses that were negative in initial screen were reported as seronegative with a value of \< 25.

The ECL (MSD) assay method is a validated, sensitive assay technique used to analyze presence of abatacept-specific antibodies in serum . It is more sensitive and has a higher drug tolerance than the ELISA method. For anti-abatacept antibody ECL(MSD) assay, a sample was considered seropositive if it had a titer of 10 or greater and if immunodepletion was observed with abatacept, or abatacept and CTLA4-T. Those responses that were not positive in the initial screen or were not confirmed to be positive based on immunodepletion were reported as seronegative and were assigned a value of \< 10.

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.

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.

Wrist synovitis was assessed by postgadolinium MRI enhancement according to OMERACT 6 RAMRIS in 3 wrist regions: distal radioulnar, radiocarpal, and intercarpal and carpometacarpal joints. For each wrist region, possible score ranges from 0-3, with 0=normal, 1=mild, 2=moderate, and 3=severe damage. The total synovitis score per wrist=the sum of the individual scores for the 3 wrist regions. Minimum score per wrist ranges from 0, indicating no damage, to 9 (score of 3\*3 wrist regions), indicating most severe damage. Change in synovitis = Follow-up synovitis score - baseline score.

Wrist synovitis was assessed by postgadolinium MRI enhancement according to OMERACT 6 RAMRIS in 3 wrist regions: distal radioulnar, radiocarpal, and intercarpal and carpometacarpal joints. For each wrist region, possible score ranges from 0-3, with 0=normal, 1=mild, 2=moderate, and 3=severe damage. The total synovitis score per wrist=the sum of the individual scores for the 3 wrist regions. Minimum score per wrist ranges from 0, indicating no damage, to 9 (score of 3\*3 wrist regions), indicating most severe damage. Change in synovitis=Follow-up synovitis score-baseline score.

Wrist synovitis was assessed by postgadolinium MRI enhancement according to OMERACT 6 RAMRIS in 3 wrist regions: distal radioulnar, radiocarpal, and intercarpal and carpometacarpal joints. For each wrist region, possible score ranges from 0-3, with 0=normal, 1=mild, 2=moderate, and 3=severe damage. The total synovitis score per wrist=the sum of the individual scores for the 3 wrist regions. Minimum score per wrist ranges from 0, indicating no damage, to 9 (score of 3\*3 wrist regions), indicating most severe damage. Change in synovitis score=Follow-up synovitis score-baseline synovitis score.

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.

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.

An event of disease relapse was defined as additional Disease-modifying antirheumatic drug (DMARD) therapy given, or 2 or more courses of high steroids given, or return to abatacept 10 mg/kg (rescue medication given), or DAS28 C-reactive protein (CRP) score \>=3.2 at 2 consecutive visits. Time to disease relapse was evaluated using life tables (Kaplan-Meier Cumulative Percentage of Events of Disease Relapse).

AE is defined as any new untoward medical occurrence or worsening of a pre-existing medical condition. SAE is 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 cancer, is a congenital anomaly/birth defect, results in the development of drug dependency or drug abuse, is an important medical event. Both subjective and objective AEs and SAEs are included.

The laboratory tests were analyses included enzyme, gastrointestinal, hematology, hepatobiliary, lipid, metabolic, nutritional, blood gas, microbiology, serology, protein, chemistry, renal, urinary tract, urinalyses, water, electrolyte and mineral investigations.

The Mayo Scoring system ranges from 0 - 12 points and is a composite index consisting of 4 disease variables (stool frequency, rectal bleeding, endoscopy evaluation, and Physician's Global Assessment). Higher Mayo scores indicate greater severity of disease. A clinical response is defined as a reduction from baseline in the Mayo score of ≥ 3 points and ≥ 30%, with an accompanying decrease in the rectal bleeding subscore of ≥ 1 point or absolute rectal bleeding subscore of ≤ 1 point.

The Mayo Scoring system ranges from 0 - 12 points and is a composite index consisting of 4 disease variables (stool frequency, rectal bleeding, endoscopy evaluation, and Physician's Global Assessment). Higher Mayo scores indicate greater severity of disease. A clinical response is defined as a reduction from baseline in the Mayo score of ≥ 3 points and ≥ 30%, with an accompanying decrease in the rectal bleeding subscore of ≥ 1 point or absolute rectal bleeding subscore of ≤ 1 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. 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 development of drug dependency or drug abuse, is an important medical event.

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. AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections, serious infections, and opportunistic infections; autoimmune disorders; neoplasms; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion) and peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion).

Complete physical examination was obtained at the Screening Visit, Day MP-365, and OL Final Visit/Early Termination visits. Interim physical examinations were performed at other study visits. Interim physical exam were not as comprehensive as the initial full examination but did note any changes in the participant's condition since the last assessment and did not preclude examination of any of the body systems as clinically indicated. Participants were observed for AEs and vital signs (blood pressure, heart rate, and temperature).

High=greater than Upper Normal Limit (ULN), Low=lower than Lower Normal Limit (LLN). LLN/ULN= Hemoglobin (HGB): \>3 g/dL decrease from Baseline (BL); Hematocrit: \<0.75 x BL; Erythrocytes: \<0.75 x BL; Platelets (PLT): \<0.67 x LLN/\>1.5 x ULN; Leukocytes: \<0.75 x LLN/ \>1.25 x ULN; neutrophils+bands: \<1.0 x 10\^3 c/uL; eosinophils: \>0.750 x 10\^3 c/uL; monocytes: \>2000 mm3; lymphocytes: \<0.750 x 10\^3 c/uL/ \>7.50 x 10\^3 c/uL.

Low=lower than LLN, High=greater than ULN. LLN/ULN= Alkaline phosphatase (ALP): \>2 x ULN; aspartate aminotransferase (AST): \>3 x ULN; alanine aminotransferase (ALT): \>3 x ULN; G-Glutamyl transferase (GGT): \>2 x ULN; Bilirubin: \>2 x ULN; blood urea nitrogen (BUN): \>2 x BL; creatinine: \>4 x BL; potassium (K): \<0.9 x LLN/ \>1.1 x ULN; calcium (Ca): \<0.8 x LLN/\>1.2 x ULN; phosphorous (P): \<0.75 x LLN/ \>1.2 5 x ULN

Low=lower than LLN, High=greater than ULN. LLN/ULN= serum glucose (Glu): \<65 mg/dL/ \>220 mg/dL; fasting serum Glu: \<0.8 x LLN/ \>1.5 x ULN; total protein: \< 0.9 x LLN/ \>1.1 x ULN; albumin:\<0.9 x LLN; uric acid: \>1.5 x ULN. For Urinalysis (Urine protein, urine Glu, urine blood, leukocyte esterase, Red Blood Cells \[RBCs\], White Blood Cells \[WBCs\]): Use ≥2 when BL value missing or value ≥4, or when pre-dose=0 or 0.5. Use ≥3 when pre-dose=1. Use ≥4 when pre-dose=2 or 3

Number of participants who achieved remission at Month 12 of treatment, as defined by a Disease Activity Score (DAS) 28-CRP score of \<2.6. DAS 28-CRP is a continuous measure, a composite of 4 variables: number of tender joints out of 28 joints, number of swollen joints out of 28 joints, CRP (in mg/L), and subject assessment of disease activity measure on a Visual Analogue Scale (VAS) of 100 millimeters (mm). The DAS28 scale=0 (best) to 10 (worst), indicating the current activity of the rheumatoid arthritis. A DAS28 \>5.1 = high disease activity; \<=3.2 = low disease activity; \<2.6 = remission.

To assess joint damage progression, the Genant-modified Sharp scoring method was used to evaluate radiographs of hands/wrists and feet for erosions and joint space narrowing (JSN). The total Genant-modified Sharp score ranges from 0 (no radiographic damage) to 290 (worst possible radiographic damage) and is the sum of the erosion score (range 0-145) and the joint space narrowing score (range 0-145). Higher scores indicated more damage.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition in a subject administered an investigational product and that does not necessarily have a causal relationship with this treatment. Related AE/SAE=Certain, Probable, Possible, or Missing. SAE=any untoward medical occurrence that results in death, is life-threatening, requires or prolongs inpatient hospitalization (including elective surgery), results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, or is an important medical event.

SAE=any untoward medical occurrence that results in death, is life-threatening, requires or prolongs inpatient hospitalization (including elective surgery), results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, or is an important medical event.

Any untoward medical occurrence (SAE) that resulted in death

The incidence rates of autoimmune disorders are defined as the (number of patients experiencing the event/exposure within the period)\*100 and are expressed in 100 person-years. Subjects experiencing the event had their exposure censored at the time of the 1st event.

The incidence rates of infections and infestations are defined as the (number of patients experiencing the event /exposure within the period)\*100 and are expressed in 100 person-years. Subjects experiencing the event had their exposure censored at the time of the 1st event.

The incidence rates of malignant neoplasms are defined as the (number of patients experiencing the event /exposure within the period)\*100 and are expressed in 100 person-years. Subjects experiencing the event had their exposure censored at the time of the 1st event.

There were 107 Prespecified, acute-infusional SAEs (occurring within 1 hour after the start of study drug infusion) pre-specified in the protocol; anaphylactic shock was the only one occuring in this study.

Number of subjects with high liver function and kinedy tests: alkaline phosphatase (ALP) \>2x upper limit of normal (ULN) or if pretreatment (PRE-RX) \>ULN then \>3x PRE-RX; aspartate aminotransferase (AST) \>3x ULN or if PRE-RX \>ULN then \>4x PRE-RX; alanine aminotransferase (ALT) \>3x ULN or if PRE-RX \>ULN then \>4x PRE-RX; g-glutamyl transferase (GGT)\>2x ULN or if PRE-RX \>ULN then \>3x PRE-RX; total bilirubin \>2x ULN or if PRE-RX \>ULN then \>4x PRE-RX; blood urea nitrogen \>2x PRE-RX; creatinine \>1.5x PRE-RX.

Marked abnormalities in hemoglobin \>3 g/dL decrease from PRE-RX; hematocrit \<0.75x PRE-RX; erythrocytes \<0.75x PRE-RX; platelet count \<0.67x lower limit of normal (LLN) or \>1.5x ULN or if PRE-RX \<LLN then \<0.5x PRE-RX and \<100,000/mm3; leukocytes \<0.75x LLN or \>1.25x ULN or if PRE-RX \<LLN then \<0.8x PRE-RX or \>ULN if PRE-RX \>ULN then \>1.2x PRE-RX or \<LLN; neutrophils if value \<1.00 x10\^3 c/uL; lymphocytes if value \<.750 x10\^3 c/uL or if value \>7.50 x10\^3 c/uL; monocytes if value \>2000/MM3; basophils if value \>400/mm3; eosinophils if value \>.750 x10\^3 c/uL

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with 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.Related AE/SAE=Certain,Probable,Possible,or Missing relationship to Drug

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. AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections, serious infections, and opportunistic infections; autoimmune disorders; neoplasms; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion) and peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion).

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/\<100,000 mm\^3; Leukocytes: \<0.75 \* LLN/ \>1.25 \* ULN, or if BL\<LLN then use \<0.8 \* BL/\>ULN, or if BL\>ULN then use \>1.2 \* BL/\<LLN; neutrophils+bands: \<1.0 \* 10\^3 c/uL; eosinophils: \>0.750 \* 10\^3 c/uL; basophils: \> 400 mm\^3; monocytes: \>2000 mm\^3; lymphocytes: \<0.750 \* 10\^3 c/uL/ \>7.50 \* 10\^3 c/uL.

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

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; chloride: \<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 \<LLN

Marked abnormality 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; 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 value ≥4,or when pre-dose=0 or 0.5. Use ≥3 when pre-dose=1. Use ≥4 when pre-dose=2 or 3

Serum samples from all 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.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with 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.Related AE/SAE=Certain,Probable,Possible,or Missing relationship to Drug

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. AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections, serious infections, and opportunistic infections; autoimmune disorders; neoplasms; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion) and peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion).

ULN=upper limit of normal; LLN=lower limit of normal; BL=baseline. Marked abnormality criteria=Hemoglobin: \>3 g/dL decrease from BL; Hematocrit: \<0.75\*BL; Erythrocytes:\<0.75\*BL; Platelets: \<0.67\*LLN/\>1.5 \* ULN, or if BL\<LLN, use 0.5\*BL/\<100,000 mm\^3; Leukocytes: \<0.75\*LLN/\>1.25\*ULN, or if BL\<LLN, use \<0.8\*BL/\>ULN, or if BL\>ULN,use \>1.2\*BL/\<LLN; neutrophils+bands: \<1.0\*10\^3 c/uL; eosinophils: \>0.750\*10\^3 c/uL; basophils: \>400 mm\^3; monocytes: \>2000 mm\^3; lymphocytes: \<0.750\*10\^3 c/uL/\>7.50\*10\^3 c/uL.

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

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; chloride: \<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 \<LLN

Marked abnormality 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; 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 value ≥4,or when pre-dose=0 or 0.5. Use ≥3 when pre-dose=1. Use ≥4 when pre-dose=2 or 3

HGB normal range (NR)=11.6 - 16.2 g/dL, marked abnormality (MA) is \>3 g/dL decrease from BL. Total protein NR=6.0 - 8.4 g/dL, MA is \<0.9\* LLN/\>1.1\* ULN; Albumin NR=3.5 - 5.3 g/dL, MA is \<0.9\* LLN, or if BL\<LLN then use \<0.75 BL

The hematocrit value refers to the percentage of blood volume that is occupied by red blood cells. Hematocrit values for participants were expressed as percentages and were averaged to yield a group mean value (percentage) at a particular time point. The mean change from baseline in hematocrit value (expressed as a percent)= mean post-baseline value (expressed as a percent) - mean baseline value (expressed as a percent).

Erythrocytes NR= 3.80 - 5.50 \*10\^6 c/uL, MA is \<0.75 \* BL

Erythrocytes NR= 3.80 - 5.50 \*10\^6 c/uL, MA is \<0.75 \* BL

Leukocytes NR=4.1 - 12.3\*10\^3 c/uL, MA is \<0.75 \* LLN/ \>1.25 \* ULN, or if BL\<LLN then use \<0.8 \* BL/\>ULN, or if BL\>ULN then use \>1.2 \* BL/\<LLN. Neutrophils+bands MA is \<1.0 \* 10\^3 c/uL. Eosinophils MA is \>0.750 \* 10\^3 c/uL. Basophils MA is \> 400 mm\^3. Monocytes MA is \>2000 mm\^3. Lymphocytes MA is \<0.750 \* 10\^3 c/uL/ \>7.50 \* 10\^3 c/uL

HGB normal range (NR)=11.6 - 16.2 g/dL, marked abnormality (MA) is \>3 g/dL decrease from BL. Total protein NR=6.0 - 8.4 g/dL, MA is \<0.9\* LLN/\>1.1\* ULN; Albumin NR=3.5 - 5.3 g/dL, MA is \<0.9\* LLN, or if BL\<LLN then use \<0.75 BL

Bilirubin NR=0.2-1.2 mg/dL, MA: \>2\* ULN, or if BL\>ULN then use \>4\* BL. BUN NR=4.0-24.0 mg/dL, MA: \>2\*BL. Creatinine NR=0.4-1.2 mg/dL, MA: \>1.5\*BL. Ca NR=8.8-10.2 mg/dL, MA: \<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. P NR=2.8-4.0 mg/dL, MA: \<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 \<LLN. Glu MA: \<65 mg/dL/ \>220 mg/dL. Uric acid MA: \>1.5\*ULN, or if BL\>ULN then use \>2\*BL.

Na NR=132 - 147 mEq/L, MA is 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. K NR=3.3 - 5.5 mEq/L, MA is \<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 NR=94 - 111 mEq/L, MA is \<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

Measurements were taken in a seated position before and after abatacept infusion.

Measurements were taken in a seated position before and after abatacept infusion.

Time to flare is defined as the elapsed number of days between the first dose date in Period B and the study day that disease flare is confirmed. All of the following criteria must be met to be defined as a flare: * \> 30% worsening in at least 3 of the 6 JRA/JIA core response variables * \> 30% improvement in not more than 1 of the 6 JRA/JIA core set variables * ≥ 2 cm of worsening must be present if the Physician or Parent Global Assessment is used to define flare * worsening in ≥ 2 joints must be present if the number of active joints or joints with limitation of motion is used to define flare based on changes in the surrogate marker, erythrocyte sedimentation rate (ESR)

ACR 20 response requires a patient to have a 20% reduction in the number of swollen and tender joints, and a reduction of 20% in three of the following five parameters: physician global assessment of disease, patient global assessment of disease, patient assessment of pain, C-reactive protein or erythrocyte sedimentation rate, and degree of disability in Health Assessment Questionnaire (HAQ) score. A participant achieved a sustained ACR 20 response if the participant had ACR 20 observed for at least 2 consecutive study visits.

The HAQ-DI includes 20 questions to assess physical function in 8 domains: dressing, arising, eating, walking, hygiene, reach, grip, and common activities. The domain questions are evaluated on a 4-point scale: 0=without any difficulty, 1=with some difficulty, 2=with much difficulty, 3=unable to do. HAQ-DI=sum of worst scores in each domain dividied by the number of domains answered. HAQ-DI ranges from 0 to a maximum overall score of 3.0. Clinically meaningful HAQ response was defined as an improvement of at least 0.3 units from baseline in HAQ DI.

To assess joint damage progression, the Genant-modified Sharp scoring method was used to evaluate radiographs of hands/wrists and feet for erosions. The erosion score range is 0 (no radiographic damage) to 145 (worst possible radiographic damage). Change from baseline = Post-baseline - Baseline value

AE was defined as 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 was defined as 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.

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 c/uL; eosinophils: \>0.750 \* 10\^3 c/uL; basophils: \> 400 mm\^3; monocytes: \>2000 mm\^3; lymphocytes: \<0.750 \* 10\^3 c/uL/ \>7.50 \* 10\^3 c/uL.

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 c/uL; eosinophils: \>0.750 \* 10\^3 c/uL; basophils: \> 400 mm\^3; monocytes: \>2000 mm\^3; lymphocytes: \<0.750 \* 10\^3 c/uL/ \>7.50 \* 10\^3 c/uL.

Sodium \< 0.9 \* LLN or \> 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: \< 0.9 \* LLN or \> 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; Chloride: \< 0.9 \* LLN or \> 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 \<0.8 \* LLN or \> 1.2 \* ULN or if BL \< LLN then use \<0.67 \* BL or \> ULN or if BL \> ULN then use \> 1.3 \* BL or \< LLN.

Glucose: \< 65 mg/dL or \> 220 mg/dL; Fasting Glucose: \<0.8 \* LLN or \> 1.5 \* ULN or if BL \< LLN then use \< 0.8 \* BL or \> ULN or if BL \> ULN then use 1.1 \* BL or \< LLN; Total protein: \< 0.9 \* LLN or 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; Albumin: \< 0.9 \* LLN or if BL \< LLN then use 0.75 \* BL; Uric acid: \> 1.5 \* ULN or if BL \> ULN then use \> 2.0 \* BL. All urinalysis abnormalities were defined as: if missing BL then use \>= 2 or if value \>=4, or if BL = 0 or 0.5 then use \>= 2, or if BL = 1.0 then use \>= 3, or if BL = 2.0 then use \>=4.

Mean baseline values are those that are reported for each cohort at each time point on Day 365, Day 729, and Day 1,093.

Participants with titers to abatacept in the DB and OL periods. Serum samples from abatacept-treated adult participants with active Rheumatoid Arthritis (RA) were screened for the presence of drug-specific antibodies using two validated direct-format enzyme-linked immunosorbent assays (ELISAs) to determine the presence of antibodies to abatacept and or CTLA4-T.

Vital signs included body temperature, heart rate, and seated blood pressure. Clinically significant changes were defined as those that were not within the normal range for the participant.

AEs were defined as any new untoward medical occurrence or worsening of a pre- existing medical condition which does not necessarily have a causal relationship with this treatment. AEs of special interest have been identified to be those which may be associated with the use of immunomodulatory agents or infusion of therapeutic proteins. Acute infusional AEs were defined as those that occurred within 1 hour after the start of the infusion.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

Mean baseline values are those that are reported for each cohort at each time point on Day 365 to Day 2,185.

All changes in participant laboratory parameters were monitored on each day of study drug administration.

ACR 20 response requires a participant to have a 20% reduction in the number of swollen and tender joints, and a reduction of 20% in three of the following five parameters: physician global assessment of disease, participant global assessment of disease, participant assessment of pain, C-reactive protein or erythrocyte sedimentation rate, and degree of disability in Health Assessment Questionnaire (HAQ) score. A participant achieved a sustained ACR 20 response if the participant had ACR 20 observed for at least 2 consecutive study visits.

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.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with 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.Related AE/SAE=Certain,Probable,Possible,or Missing relationship to Drug

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. AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections, serious infections, and opportunistic infections; autoimmune disorders; neoplasms; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion) and peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion).

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/\<100,000 mm\^3; Leukocytes: \<0.75 \* LLN/ \>1.25 \* ULN, or if BL\<LLN then use \<0.8 \* BL/\>ULN, or if BL\>ULN then use \>1.2 \* BL/\<LLN; neutrophils+bands: \<1.0 \* 10\^3 c/uL; eosinophils: \>0.750 \* 10\^3 c/uL; basophils: \> 400 mm\^3; monocytes: \>2000 mm\^3; lymphocytes: \<0.750 \* 10\^3 c/uL/ \>7.50 \* 10\^3 c/uL.

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

Serum samples collected from participants were used to determine serum levels of IgA, IgM, and IgG. Time-matched baseline values were presented by visit and represented the mean baseline value for only that cohort of participants with serum samples available at that visit.

Serum samples collected from participants were used to determine serum levels of IgA, IgM, and IgG. Time-matched mean change from baseline = Post-baseline value - time-matched baseline value, where the time-matched baseline value represents the mean baseline value for only that cohort of participants with serum samples available at that visit.

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. Related SAE/AE = possibly, probably, or certainly related to study drug

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. AEs of special interest are those AEs that may be associated with the use of immunomodulatory drugs, including all infections, serious infections, and opportunistic infections; autoimmune disorders; neoplasms; acute infusional AEs (pre-specified AEs occurring within 1 hour of start of infusion) and peri-infusional AEs (pre-specified AEs occurring within 24 hours of the start of infusion).

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 c/uL; eosinophils: \>0.750 \* 10\^3 c/uL; basophils: \> 400 mm\^3; monocytes: \>2000 mm\^3; lymphocytes: \<0.750 \* 10\^3 c/uL/ \>7.50 \* 10\^3 c/uL.

ULN=upper level of normal; BL=baseline.Marked abnormality criteria: High alkaline phosphatase (ALP): \>2\* ULN, or if BL\>ULN then use \>3\* BL; high aspartate aminotransferase (AST): \>3\* ULN (80 U/L), or if BL\>ULN then use \>4\* BL; high alanine aminotransferase (ALT): \>3\* ULN (34-47 U/L), or if BL\>ULN then use \>4\* BL; high G-Glutamyl transferase (GGT): \>2\* ULN, or if BL\>ULN then use \>3\* BL; high bilirubin: \>2\* ULN, or if BL\>ULN then use \>4\* BL; high blood urea nitrogen (BUN): \>2\* BL; high creatinine: \>1.5\* BL (ULN 14.6 pg/mg. AST ULN=80 U/L; ALT ULN=34-47 U/L;creatinine ULN=14.6 pg/mg.

Physical examinations were performed at the discretion of the investigator and included breast examinations for female participants. Vital sign measurements were performed for participants before and after infusion of study medication at each visit and included seated systolic blood pressure, seated diastolic blood pressure, temperature, and heart rate. Abnormalities were determined to be clinically significant by the investigator.

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. Related SAE/AE = possibly, probably, or certainly related to study drug

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

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 \<LLN

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

Physical examinations were performed at the discretion of the investigator and included breast examinations for female participants. Vital sign measurements were performed for participants before and after infusion of study medication at each visit and included seated systolic blood pressure, seated diastolic blood pressure, temperature, and heart rate. Abnormalities were determined to be clinically significant by the investigator.

Assess inhibition \& progression of structural damage in MTX inadequate responders with moderate to severe active RA on SC Abatacept plus MTX, utilizing eMRI and X-ray at baseline, eMRI at Week 12, and eMRI and X-ray final assessment at week 24.

Event-free survival is a composite endpoint defined as rejection-free, severe GVHD-free survival. Events for this outcome include death, severe (grade II-IV) acute GVHD up to day 100, moderate to severe chronic GVHD up to 1 year, and/or graft rejection up to 1 year.

Renal Response is defined as the presence of all the following criteria: PROTEINURIA: Reduction of baseline urine protein/creatinine ratio (UPCR) of \>= 50% and to less than 3. RENAL FUNCTION: No worsening of baseline estimated glomerular filtration rate (eGFR) defined as within normal range if normal at baseline or ≥ 75% baseline value if below normal at baseline.

Safety is measured using AEs, including clinical significant changes in vital signs, laboratory test abnormalities and clinical tolerability of abatacept, and using serious AEs

The efficacy of treatment on skin fibrosis will be measured by changes from baseline to month 12 in mRSS, a measure of skin thickness. mRSS scores have a range from 0 to 51, with higher score indicating greater severity of SSc (worse outcome).

number of participants with adverse events

The ACR score of 20 indicates the degree of improvement in a patient's rheumatoid arthritis (RA), based on ACR guidelines (ACR20). The ACR score represents a percentage. To qualify for an ACR20 score, the patient must have \>=20% fewer tender joints and \>=20% fewer swollen joints and show 20% improvement in at least 3 of: patient overall assessment of his/her RA, physician global assessment of the patient's RA, patient self-assessment of pain, patient self-assessment of physical functioning, and results of an erythrocyte sedimentation rate or C-reactive protein test (to assess inflammation). Percentage is calculated n/N with n=number of participants with ACR score of 20 and N= all randomized participants who received at least one dose of study drug.

The ACR score indicates the degree of improvement in a patient's rheumatoid arthritis (RA), based on ACR guidelines. The ACR score= a percentage. To qualify for a score of 20, 50 or 70 (ACR20, ACR50 or ACR70), the patient must have \>=20%, \>=50% or \>=70%, respectively, fewer tender joints and \>=20%, \>=50% or \>=70%, respectively, fewer swollen joints and show 20%, 50% or 70%, respectively, improvement in at least 3 of the following: patient overall assessment of his/her RA, physician global assessment of the patient's RA, patient self-assessment of pain, patient self-assessment of physical functioning, and results of an erythrocyte sedimentation rate or C-reactive protein test (to assess inflammation). Treatment groups represent treatment received in the short term period. Percentage calculated as n/m with n=number of paticipants with sustained ACR response at Day 533; m= long term participants who received at least one dose of drug and were ACR responders in the short term period.

Adjusted mean. The Health Assessment Questionnaire Disability Index (HAQ-DI) assesses patients' functional ability by rating their abilities over the previous week. At least 2 questions are asked from each of 8 categories: dressing and grooming, hygiene, arising, reach, eating, grip, walking, and common daily activities. Patients rate difficulty performing specific tasks: 0=without difficulty, 1=with some difficulty, 2=with much difficulty, and 3=unable to do. The sum of the categories score (the highest scored item in the category) is divided by the number of categories answered, yielding a score from 0-3. Treatment groups represent treatment received in the short term period. Baseline is Day 1 of the study or last non-missing pre-treatment value.

The Health Assessment Questionnaire (HAQ) disability index assesses patients' functional ability by rating their abilities over the previous week. At least 2 questions are asked from each of 8 categories: dressing and grooming, hygiene, arising, reach, eating, grip, walking, and common daily activities. Patients rate difficulty performing specific tasks: 0=without difficulty, 1=with some difficulty, 2=with much difficulty, and 3=unable to do. The higher the number the worse the outcome. The sum of the categories score (the highest scored item in the category) is divided by the number of categories answered, yielding a score from 0-3. HAQ response=reduction of at least 0.30 units in HAQ score from baseline. The percentage of participants with a reduction of at least 0.30 units in their HAQ score from baseline is presented. Baseline is Day 1 of the study or last non-missing pre-treatment value. Treatment groups represent treatment received in the short term period.

The Disease Activity Score 28 using C-Reactive Protein (DAS28-CRP) is a measure of disease activity in rheumatoid arthritis (RA) and assesses the 28 joints RA commonly affects; the score includes the number of tender and swollen joints (out of 28), CRP level (a measure of inflammation in the blood), and the patient's global assessment of health (ranging from very good to very bad). An overall DAS \>5.1 implies active disease; \<3.2, well controlled disease; and \<2.6, remission.). Treatment groups represent treatment received in the short term period. Baseline is Day 1 of the study or last non-missing pre-treatment value.

SLE flares scored using BILAG:A:presence of =\>1 serious;B:more moderate;C:mild symptomatic;D:prior activity,no current symptoms;E:organ that has never been involved. Calculated based on change during previous 4 weeks (1=improving,2=staying same,3=worsening,4=new).New SLE flare:first BILAG 'A' or 'B' event adjudicated to be flare following resolution of entry flare and start of prednisone/prednisone-equivalent taper.Inception treatment failure included (entry flare did not subside by Day 57/participant discontinued double-blind period before Day 29).

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. Participants who discontinued the study due to an AE were recorded. Drug-related AEs or SAEs: events with a relationship to the study therapy of certain; probable; possible; or missing.

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, it was decided that AEs of particular importance 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.

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\* lower limit of normal (LLN) or \>1.5\* upper limit of normal (ULN) (or, if pre-Rx value \<LLN, then \<0.5\* pre-Rx value or \<100000/mm\^3).

MMAs 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.

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.

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, Sodium (serum): \<0.95x LLN or \>1.05x ULN (if pre-Rx\<LLN, then \<0.95x pre-Rx or \>ULN. If pre-Rx \>ULN, then \>1.05x pre-Rx or \<LLN); Potassium (serum), Chloride (serum), protein (total): \<0.9x LLN or \>1.1xULN (if pre-Rx \<LLN, then \<0.9xpre-Rx or \>ULN. If pre-Rx \>ULN, then \>1.1xpre-Rx or \<LLN; Calcium (total): \<0.8xLLN or \>1.2xULN (if pre-Rx \<LLN, then \<0.75x pre-Rx or \>ULN. If pre-Rx \>ULN, then \>1.25x pre-Rx or \<LLN.

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, 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.

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, red blood cells (RBC), white blood cells (WBC): \>=2+ (or, if value \>=4, or if pre-Rx value = 0 or 0.5, then \>= 2\* 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; Glomerular filtration rate (GFR): \<=60 mL/min/1.73m\^2 or \> 15% change from baseline; Protein/creatinine ratio: \> 100 mg/mmol.

ARA criteria is a 7-item tool for RA classification purposes; a patient is said to have RA (meeting endpoint) if he or she has satisfied at least 4 of the 7 criteria. If a participant discontinued due to lack of efficacy, he/she was regarded as meeting primary endpoint also.

ACR 20 response requires a participant to have a 20% reduction in the number of swollen and tender joints, and a reduction of 20% in three of the following five parameters: physician global assessment of disease, participant global assessment of disease, participant assessment of pain, C-reactive protein or erythrocyte sedimentation rate, and degree of disability in Health Assessment Questionnaire score. A participant achieved a sustained ACR 20 response if the participant had ACR 20 observed for at least 2 consecutive study visits.

The number of participants receiving concomitant rheumatoid arthritis treatment with disease modifying rheumatic drugs and/or biologics.

AE=any new untoward medical occurrence or worsening of a pre-existing medical condition which does not necessarily have a causal relationship with 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. Related AE/SAE=Certain,Probable,Possible,or Missing relationship to drug.

AEs were defined as any new untoward medical occurrence or worsening of a pre- existing medical condition which does not necessarily have a causal relationship with this treatment. AEs of special interest were those which may be associated with the use of immunomodulatory agents or infusion of therapeutic proteins. Acute infusional AEs were defined as those that occurred within 1 hour after the start of the infusion. Peri-Infusional AEs were defined as those that occurred within 24 hours after the start of the infusion.

Time-matched baseline (Day 0) values and post-baseline values were presented for each post-baseline visit and represent only that cohort of participants with measurements available at that post-baseline assessment. Mean Change from Baseline data for these cohorts are presented in Outcome Measure 6.

Blood samples for immunoglobulin assessments were obtained to determine change from baseline in serum IgA. Baseline data for these time-matched cohorts are presented in Outcome Measure 5.

Time-matched baseline (Day 0) values and post-baseline vales were presented for each post-baseline visit and represent only that cohort of participants with measurements available at that post-baseline assessment. Mean Change from Baseline data for these cohorts are presented in Outcome Measure 8.

Blood samples for immunoglobulin assessments were obtained to determine change from baseline in serum IgG. Baseline data for these cohorts are presented in Outcome Measure 7.

Time-matched baseline (Day 0) values and post-baseline values were presented for each post-baseline visit and represent only that cohort of participants with measurements available at that post-baseline assessment. Mean Change from Baseline data for these cohorts are presented in Outcome Measure 10.

Blood samples for immunoglobulin assessments were obtained to determine change from baseline in serum IgM. Baseline data for these time-matched cohorts are presented in Outcome Measure 9.

Participants were monitored for adverse events (AEs) at each visit. Cumulative AEs were tracked including specific AE, severity, and relationship on source documentation. Special attention was given to infusion-related events and hypersensitivity reactions. Assessment of Complete Blood Count (CBC) and Metabolic profile were also tracked.

Area under the serum concentration-time curve from time zero extrapolated to infinity

Serum concentrations of abatacept were analyzed using a validated enzyme-linked immunosorbent assay (ELISA). Cmax was measured in micrograms per milliliter (μg/mL). Blood samples for pharmacokinetic (PK) parameters were collected at Day 1 pre-dose at 0 hour (h), 1, 2, and 8 h post dose, and on subsequent Days, 2 (24 h post dose), 3 (48 h), 5 (96 h), 8 (168 h), 15 (336 h), 29 (672 h) , 43 (1008 h), 57 (1344 h) and 71 (1680 h) following the single administration of abatacept SC.

Serum concentrations of abatacept were analyzed using ELISA. AUC (0-T) was measured in μg\*h/mL. Blood samples were collected at Day 1 pre-dose at 0 h, 1, 2, and 8 h post dose, and on subsequent Days, 2 (24 h post dose), 3 (48 h), 5 (96 h), 8 (168 h), 15 (336 h), 29 (672 h) , 43 (1008 h), 57 (1344 h) and 71 (1680 h) following the single administration of abatacept SC.

Serum concentrations of abatacept were analyzed using ELISA. Blood samples were collected at Day 1 pre-dose at 0 hour (h), 1, 2, and 8 h post dose, and on subsequent Days, 2 (24 h post dose), 3 (48 h), 5 (96 h), 8 (168 h), 15 (336 h), 29 (672 h) , 43 (1008 h), 57 (1344 h) and 71 (1680 h) following the single administration of abatacept SC. AUC (INF) was measured in μg\*h/mL

Cmax was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). Cmax was measured in micro grams per milliliter (µg/mL).

Tmax was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). Tmax was measured in hours (h).

AUC (0 - 28) was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). AUC (0 - 28) was measured in micro grams\*hours per milliliter (µg\*h/mL).

AUC (0 - T) was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). AUC (0 - T) was measured in micro grams\*hour per milliliter (µg\*h/mL).

AUC (0 - INF) was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). AUC (0 - INF) was measured in µg\*h/mL.

T-HALF was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). T-HALF was measured in hours (h).

CLT was the volume of abatacept cleared by the system, normalized by baseline body weight. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). CLT was measured in milliliters per hours per kilogram of body weight (mL/h/kg).

Vss was derived from serum concentration versus time data. Serum samples were analyzed for abatacept by a validated enzyme-linked immunosorbent assay (ELISA) and were obtained at: predose (0 hours), 0.25 hours (h), 0.5, 1, 2, 6, 12, 24, 72, 168, 336, 504, 672, 1008, 1344, and 1688 h post dose (Days 1 to 71). The results were summarized. The lower limit of assay quantitation (LLOQ) was 1.00 nanograms per milliliter (ng/mL). Vss was measured in liters per kg body weight (L/kg).

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. 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.

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. Related AE=relationship of certain, probable, possible, or missing. Intensity = mild (grade 1), moderate (grade 2), severe (grade 3), life-threatening/disabling (grade 4).

Vital sign measurements are summarized without regard to position (sitting, standing, supine).

Vital signs measurements are summarized without regard to position (sitting, standing, supine).

Vital sign measurements are summarized without regard to position (sitting, standing, supine).

Vital sign measurements are summarized without regard to position (sitting, standing, supine).

Laboratory tests consisted of complete blood count, chemistry, and urinalysis.

Participants received abatacept while also receiving DMARDS over a short term (ST) 12 Week period. To eliminate contribution from the IV loading dose of abatacept during the short term study period, Cmin values were selected from Days 71 to 85, when contribution from IV was negligible. Minimum trough serum concentration of abatacept (Cmin) was measured in micrograms/milliliter (µg/mL). Data are presented by treatment the participant actually received, not by what they were randomized to receive.

AEs during variable dose phase of LTE + 56 days post last dose in the variable dose phase or start of the fixed dose phase, which ever came first; includes deaths reported during the variable dose phase including those that occurred greater than 56 days after last dose. Medical Dictionary for Regulatory Activities (MedDRA) version: 15.1. AE=any new unfavorable symptom, sign, or disease or worsening of a preexisting condition that may not have a causal relationship with treatment. SAE=medical event that at any dose results in death, persistent or significant disability/incapacity, or drug dependency/abuse; is life-threatening, an important medical event, or a congenital anomaly/birth defect; or requires or prolongs hospitalization (included hospitalizations for elective surgical procedures). Treatment-related=having certain, probable, possible, or missing relationship to study drug. Data presented by treatment the participant was randomized to and not what they actually received.

LTE period with variable abatacept dosing starting on Day 85 and continuing until Day 533 when LTE fixed dosing started. AEs of special interest: infection and/or infestation; neoplasms (malignant); pre-specified autoimmune disorder; infusional AEs (peri-infusional: pre-specified AEs occurring during first 24 hours (hrs) after start of the IV loading dose; acute infusional: pre-specified AEs occurring during the first hour after the start of the IV loading dose; systemic injection site reactions (SIR): pre-specified AEs for SIR; local injection site reaction: pre-specified AEs for local site reaction. Data are presented by treatment the participant was randomized to and not what they actually received.

On Day 85 participants rolled over into the LTE with variable dose phase first and at Day 533, a fixed dose phase of 125 mg abatacept SC weekly, irrespective of body weight. This summary includes AEs reported during entire LTE treatment plus 56 days post last dose; includes all deaths reported during the LTE including those that occurred greater than 56 days after last dose. MedDRA version: 15.1. AE=any new unfavorable symptom, sign, or disease or worsening of a preexisting condition that may not have a causal relationship with treatment. SAE=a medical event that at any dose results in death, persistent or significant disability/incapacity, or drug dependency/abuse; is life-threatening, an important medical event, or a congenital anomaly/birth defect; or requires or prolongs hospitalization (also included hospitalizations for elective surgical procedures). Treatment-related=having certain, probable, possible, or missing relationship to study drug.