A participant was a responder if the following 3 criteria for improvement from Baseline were met:

• ≥ 20% improvement in tender joint count;

• ≥ 20% improvement in swollen joint count; and

• ≥ 20% improvement in at least 3 of the 5 following parameters:

  • Patient's assessment of pain (measured on a 100 mm visual analog scale [VAS]);
  • Patient's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Physician's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index [HAQ-DI]);
  • C-Reactive Protein level.

The full analysis set (all randomized participants); missing values were imputed using the last observation carried forward (LOCF) method for participants with at least 1 postbaseline value.

The DAS28-CRP is a composite score to measure disease activity in patients with rheumatoid arthritis, derived from the following variables:

• The number of swollen and tender joints assessed using the 28-joint count;
• C-reactive protein (CRP) level
• Patient's global assessment of disease activity assessed on a score from 0 to 100 transformed from the result measured on a horizontal scale from 0 (no RA activity at all) to 10 (worst RA activity imaginable).

The DAS28-CRP score ranges from approximately zero to ten. Higher DAS28-CRP scores indicate higher disease activity.

A repeated measures analysis with the DAS28-CRP change from baseline as the response and the stratification variables, visit, treatment, treatment-by-visit interaction and the baseline DAS28-CRP measurement as predictors in the model was performed.

Full analysis set with available data at each time point

A participant was a responder if the following 3 criteria for improvement from Baseline were met:

• ≥ 20% improvement in tender joint count;

• ≥ 20% improvement in swollen joint count; and

• ≥ 20% improvement in at least 3 of the 5 following parameters:

  • Patient's assessment of pain (measured on a 100 mm visual analog scale [VAS]);
  • Patient's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Physician's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index [HAQ-DI]);
  • C-Reactive Protein level.

Full analysis set; LOCF imputation was used for participants with at least 1 postbaseline value (indicated by n).

A participant was a responder if the following 3 criteria for improvement from Baseline were met:

• ≥ 50% improvement in tender joint count;

• ≥ 50% improvement in swollen joint count; and

• ≥ 50% improvement in at least 3 of the 5 following parameters:

  • Patient's assessment of pain (measured on a 100 mm visual analog scale [VAS]);
  • Patient's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Physician's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index [HAQ-DI]);
  • C-Reactive Protein level.

Full analysis set with available data at week 24

A participant was a responder if the following 3 criteria for improvement from Baseline were met:

• ≥ 70% improvement in tender joint count;

• ≥ 70% improvement in swollen joint count; and

• ≥ 70% improvement in at least 3 of the 5 following parameters:

  • Patient's assessment of pain (measured on a 100 mm visual analog scale [VAS]);
  • Patient's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Physician's global assessment of disease activity (measured on a likert scale from 0 to 10);
  • Patient's self-assessment of physical function (Health Assessment Questionnaire - Disability Index [HAQ-DI]);
  • C-Reactive Protein level.

Full analysis set with available data at week 24

Adverse events (AEs) were graded for severity according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 according to the following scale:

1 = mild; 2 = moderate; 3 = severe; 4 = life-threatening; 5 = fatal. A treatment-related AE is defined as an event where the answer to the question "is there a reasonable possibility that the event may have been caused by the Investigational Medicinal Product" was yes.

A serious adverse event is defined as an AE that meets at least 1 of the following serious criteria:

• fatal
• life threatening (places the subject at immediate risk of death)
• requires inpatient hospitalization or prolongation of existing hospitalization
• results in persistent or significant disability/incapacity
• congenital anomaly/birth defect
• other medically important serious event.

The safety analysis set (all participants who received at least 1 dose of study drug)

Two validated assays were used to detect the presence of anti-drug antibodies. Samples were first tested in an electrochemiluminescence (ECL)-based bridging immunoassay to detect anti-drug antibodies (ADA) against ABP 501 and adalimumab (Binding Antibody Assay). Samples confirmed to be positive for binding antibodies were subsequently tested in a non-cell based bioassay to determine neutralizing activity against ABP 501 or adalimumab (Neutralizing Antibody Assay).

Developing antibody incidence is defined as a negative or no antibody result at baseline and a positive antibody result at a post-baseline time point.

Participants with at least 1 evaluable antibody test result (to either ABP 501 or adalimumab)