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.

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

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.

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

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

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

Serum concentrations of abatacept were analyzed using ELISA. 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. Tmax was measured in hours (h).

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

Serum concentrations of abatacept were analyzed using ELISA. 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. T-HALF was measured in hours (h).

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

Serum concentrations of abatacept were analyzed using ELISA. 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. CL/F was measured in milliliters per hour per kilogram body weight (mL/h/kg).

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

Serum concentrations of abatacept were analyzed using ELISA. 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. V/F was measured in liters per kilogram body weight (L/kg)

PK-evaluable analysis population: All randomized and treated participants with adequately evaluable PK parameters were summarized.

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. Treatment-related=having certain, probable, possible, or missing relationship to study drug. Includes data Day 1 up to 76 days (71 days + 5 day window) post the single dose of study drug.

All treated participants were included in safety analysis.

Prospectively identified events of special interest which were a subset of all AEs, and were either SAEs or non-serious AEs, included the following categories: Infections, Autoimmune Disorders, Malignancy, local site reactions, any AE occurring within 24 hours of SC injection. 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.

All treated participants were included in safety analysis.

Blood samples were screened at baseline, Day 57 and Day 71 for the presence of drug-specific antibodies using Electrochemiluminescence (ECL). A positive immunogenicity response relative to baseline for Anti-Cytotoxic T Lymphocyte Antigen 4-T Cell (CTLA4) and 'possibly immunoglobulin (Ig)', and 'Ig and/or Junction Region', respectively, was defined as: A missing baseline immunogenicity measurement and a positive analytical laboratory reported immunogenicity response post-baseline; A negative baseline immunogenicity response and a positive analytical laboratory reported immunogenicity response post-baseline; A positive baseline immunogenicity response and a positive analytical laboratory reported immunogenicity response post-baseline that has a titer value strictly greater than the baseline titer value. Baseline=Pre-dose value.

All treated participants with at least one post baseline immunogenicity result reported were included in the immunogenicity analysis. n=number of participants evaluated at the specific time point.

Marked abnormality criteria: lower limit of normal (LLN); upper limit of normal (ULN); pretreatment (preRX); cells per microliter (cµ/L); milligram per deciliter (mg/dL); milliequivalent (mEq): Hematology: leukocytes (*10^3 c/µL): <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 (*10^3 cµ/L): if value >0.750*10^3 c/µL; lymphocytes (*10^3 cµ/L): if value <0.750*10^3 c/µL or if value >7.50*10^3 c/µL. Chemistry: blood urea nitrogen (mg/dL): >2*preRX; creatinine (mg/dL): >1.5*preRX; potassium (mEq/L): <0.9*LLN or >1.1*ULN, or if preRX<LLN, use <0.9*preRX or >ULN, or if preRX>ULN, use 1.1*preRX or <LLN; glucose (mg/dL): <65 mg/dL (low) or >220 mg/dL (high). Urine Blood, urine red blood cell (RBC), urine white blood cell (WBC): if missing PreRX use >= 2, or if Value >= 4, or if preRX = 0 or 0.5 then use >= 2, or if preRX = 1 then use >= 3, or if preRX = 2 or 3 then use >= 4.

All treated participants with laboratory values were included in the safety analysis. n=number of participants evaluated.