Long-term Safety and Efficacy of ABP 501 in Subjects With Moderate to Severe Rheumatoid Arthritis

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.

Laboratory results were graded 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.

Two validated assays were used to detect the presence of anti-drug antibodies. All samples were first tested in an electrochemiluminescence (ECL)-based bridging immunoassay to detect anti-drug antibodies against ABP 501 (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. If a sample was positive for binding antibodies and demonstrated neutralizing activity at the same time point, the sample was defined as positive for neutralizing antibodies.

Preexisting antibody positive indicates participants with a positive result at baseline of the extension study. Developing antibody positive indicates participants with a negative or no result at baseline of the extension study who were positive at any time point post-baseline during the extension study.

A participant was a responder if the following 3 criteria for improvement from Baseline of the parent study 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 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.