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

Number of Participants With Adverse Events

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.

Time frame: From the first dose of study drug in the extension study to 28 days following the last dose; 72 weeks

Number of Participants With Grade ≥ 3 Hematology and Chemistry Laboratory Results

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.

Time frame: From the first dose of study drug in the extension study to 28 days following the last dose; 72 weeks

Percentage of Participants Who Developed Antibodies to ABP 501

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.