Safety Set consisted of all participants that received study drug in the core study (CACZ885H2361 [NCT01356602]) and had at least one post-baseline safety assessment. The patients with more than one treatment are counted in the Safety Set under those treatment groups as the actual treatments they received. Thus, the number of subjects in the treatment arms are more than the number of randomized subjects.

The Kaplan-Meier estimates of the proportion of participants with first new gout flare, along with the associated 95% confidence intervals using Greenwood's formula were reported. The first new flare was observed either in the core or extension of the study right prior to the switch. The results were reported as Kaplan-Meier estimates.

Full Analysis Set (FAS) consisted of all participants randomized in the core study (CACZ885H2361 [NCT01356602]) that had taken at least one dose of study drug.

The flare rate was calculated as the number of new flares over the period of observation in years. New flares that occurred before the first study medication dose in the extension 1 study were considered.

FAS consisted of all participants randomized in the core study (CACZ885H2361 [NCT01356602]) that had taken at least one dose of study drug.

A Likert scale is a type of scale with a range of responses corresponding to an item such as pain. Participants were advised to score their current pain intensity in the most affected joint of the gouty arthritis flare on a 5-point Likert scale of 1 (None) to 5 (extreme pain), where; 1= none, 2= mild pain, 3= moderate pain, 4= severe pain, or 5= extreme pain (none, mild, moderate, severe, extreme). The higher value presented on the scale was the outcome (high intensity of pain). The respondent selects the best response that indicates the respondent's subjective evaluation of the item. The Last-observation-carried-forward (LOCF) method was used to impute post-dose pain intensity Likert measurements up to 14 days.

Modified Analysis Set (MAS) consisted of all FAS participants. Here, the number of participants analyzed refer to the participants evaluable for this outcome measure.

Patients scored their current pain intensity in the most affected joint of the current gouty arthritis flare on a 0-100 VAS, ranging from no pain (0) to unbearable pain (100). Scores on the 100 mm linear scale were measured to the nearest millimeter from the left.

MAS consisted of all FAS participants. Here, the number of participants analyzed refer to the participants evaluable for this outcome measure.

Participants were advised to make a global assessment of response to treatment using a 5-point Likert scale (1=excellent, 2=good, 3=acceptable, 4=slight, 5=poor).

MAS consisted of all FAS participants. Here, the number of participants analyzed refer to the participants evaluable for this outcome measure.

Tenderness was measured on a 0-3 point scale: no pain, participant states that "there is pain", participant states "there is pain and winces" and participant states "there is pain, winces and withdraws" on palpation or passive movement of the affected study joint. Swelling was measured on a 0 - 3 point scale as follows: 0 = no swelling, 1 = palpable, 2= visible and 3 = bulging beyond the joint margins. Erythema was assessed as present, absent or not assessable.

MAS consisted of all FAS participants. Here, the number of participants analyzed refer to the participants evaluable for this outcome measure and at specific category.

The physician made a global assessment of the participant's response to treatment using a 5-point Likert scale: 1=very good, 2=good, 3=fair, 4=poor, 5=very poor.

MAS consisted of all FAS participants. Here, the number of participants analyzed refer to the participants evaluable for this outcome measure.