Atacicept was administered subcutaneously at a dose of 75 mg twice a week for initial 4 weeks as loading dose, followed by 75 mg once a week for subsequent 21 weeks.

Atacicept was administered subcutaneously at a dose of 150 mg twice a week for initial 4 weeks as loading dose, followed by 150 mg once a week for subsequent 21 weeks.

Placebo matched to atacicept was administered subcutaneously twice a week for initial 4 weeks, followed by once a week for subsequent 21 weeks.

ACR70-CRP response is defined as >=70% improvement in both tender joint counts (based on a total of 68 joints) and swollen joint counts (based on a total of 66 joints) together with >=70% improvement in at least 3 of the following 5 measures: 1) participant's assessment of pain; 2) participant's global assessment of disease activity; 3) physician's global assessment of disease activity; 4) participant's assessment of physical function; and 5) acute-phase marker (CRP).

DAS28-CRP incorporates non-graded joint counts for tenderness and swelling based on a total of 28 joints, CRP as a marker of inflammation, and a general health assessment using a 100-millimeter (mm) visual analog scale (the participant's global assessment of disease activity). DAS28 ranges between 0 and 10 representing current disease activity. A value above 5.1 represents high disease activity, a value below 3.2 represents low disease activity, and a value below 2.6 represents remission.

DAS28-CRP incorporates non-graded joint counts for tenderness and swelling based on a total of 28 joints, CRP as a marker of inflammation, and a general health assessment using a 100 mm visual analog scale (the participant's global assessment of disease activity). DAS28 ranges between 0 and 10 representing current disease activity. A value above 5.1 represents high disease activity, a value below 3.2 represents low disease activity, and a value below 2.6 represents remission.

The HAQ-DI is a participant-reported assessment of ability to perform tasks in 8 categories of daily living activities: dress/groom; arise; eat; walk; reach; grip; hygiene; and common activities over past week. Each item was scored on 4-point scale from 0 to 3: 0 = no difficulty; 1 = some difficulty; 2 = much difficulty; 3 = unable to do. Overall score was computed as the sum of domain scores and divided by the number of domains answered. Total possible score range is 0 to 3 where 0 = least difficulty and 3 = extreme difficulty. Percentage of participants achieving improvement in HAQ-DI of at least 0.3 from baseline at Week 26 was reported.

The EULAR response criteria evaluate change in DAS28 scores represented as "good response", "moderate response", or "no response" considering both the current DAS28 score and the observed improvement from baseline. Participants were considered to have "good" or "moderate" EULAR response if at the time of assessment, their DAS28 score was <=5.1 and the improvement from baseline in their DAS28 score was greater than (>) 0.6; or if at the time of assessment, their DAS28 score was >5.1 and improvement from baseline in their DAS28 score was >1.2.

An AE was defined as any new untoward medical occurrences/worsening of pre-existing medical condition without regard to possibility of causal relationship. An SAE was an AE that resulted in any of the following outcomes: death; life threatening; persistent/significant disability/incapacity; initial or prolonged inpatient hospitalization; congenital anomaly/birth defect.

Atacicept was administered subcutaneously at a dose of 75 mg twice a week for initial 4 weeks as loading dose, followed by 75 mg once a week for subsequent 21 weeks.

Atacicept was administered subcutaneously at a dose of 150 mg twice a week for initial 4 weeks as loading dose, followed by 150 mg once a week for subsequent 21 weeks.

Total of all reporting groups

Atacicept was administered subcutaneously at a dose of 25 mg twice a week for initial 4 weeks as loading dose, followed by 25 mg once a week for subsequent 21 weeks.

Atacicept was administered subcutaneously at a dose of 75 mg twice a week for initial 4 weeks as loading dose, followed by 75 mg once a week for subsequent 21 weeks.

Atacicept was administered subcutaneously at a dose of 150 mg twice a week for initial 4 weeks as loading dose, followed by 150 mg once a week for subsequent 21 weeks.

ACR50-CRP response is defined as >=50% improvement in both tender joint counts (based on a total of 68 joints) and swollen joint counts (based on a total of 66 joints) together with >=50% improvement in at least 3 of the following 5 measures: 1) participant's assessment of pain; 2) participant's global assessment of disease activity; 3) physician's global assessment of disease activity; 4) participant's assessment of physical function; and 5) acute-phase marker (CRP).

ITT population included all randomized participants who received at least 1 treatment dose.

ACR70-CRP response is defined as >=70% improvement in both tender joint counts (based on a total of 68 joints) and swollen joint counts (based on a total of 66 joints) together with >=70% improvement in at least 3 of the following 5 measures: 1) participant's assessment of pain; 2) participant's global assessment of disease activity; 3) physician's global assessment of disease activity; 4) participant's assessment of physical function; and 5) acute-phase marker (CRP).

ITT population included all randomized participants who received at least 1 treatment dose.

DAS28-CRP incorporates non-graded joint counts for tenderness and swelling based on a total of 28 joints, CRP as a marker of inflammation, and a general health assessment using a 100-millimeter (mm) visual analog scale (the participant's global assessment of disease activity). DAS28 ranges between 0 and 10 representing current disease activity. A value above 5.1 represents high disease activity, a value below 3.2 represents low disease activity, and a value below 2.6 represents remission.

ITT population included all randomized participants who received at least 1 treatment dose.

DAS28-CRP incorporates non-graded joint counts for tenderness and swelling based on a total of 28 joints, CRP as a marker of inflammation, and a general health assessment using a 100 mm visual analog scale (the participant's global assessment of disease activity). DAS28 ranges between 0 and 10 representing current disease activity. A value above 5.1 represents high disease activity, a value below 3.2 represents low disease activity, and a value below 2.6 represents remission.

ITT population included all randomized participants who received at least 1 treatment dose.

The HAQ-DI is a participant-reported assessment of ability to perform tasks in 8 categories of daily living activities: dress/groom; arise; eat; walk; reach; grip; hygiene; and common activities over past week. Each item was scored on 4-point scale from 0 to 3: 0 = no difficulty; 1 = some difficulty; 2 = much difficulty; 3 = unable to do. Overall score was computed as the sum of domain scores and divided by the number of domains answered. Total possible score range is 0 to 3 where 0 = least difficulty and 3 = extreme difficulty. Percentage of participants achieving improvement in HAQ-DI of at least 0.3 from baseline at Week 26 was reported.

ITT population included all randomized participants who received at least 1 treatment dose. Here, 'N' (number of participants analyzed) signifies those participants who were evaluable for this outcome measure.

The EULAR response criteria evaluate change in DAS28 scores represented as "good response", "moderate response", or "no response" considering both the current DAS28 score and the observed improvement from baseline. Participants were considered to have "good" or "moderate" EULAR response if at the time of assessment, their DAS28 score was <=5.1 and the improvement from baseline in their DAS28 score was greater than (>) 0.6; or if at the time of assessment, their DAS28 score was >5.1 and improvement from baseline in their DAS28 score was >1.2.

ITT population included all randomized participants who received at least 1 treatment dose.

An AE was defined as any new untoward medical occurrences/worsening of pre-existing medical condition without regard to possibility of causal relationship. An SAE was an AE that resulted in any of the following outcomes: death; life threatening; persistent/significant disability/incapacity; initial or prolonged inpatient hospitalization; congenital anomaly/birth defect.

Safety population included all randomized participants who received at least 1 treatment dose and had safety data following their first dose.

Atacicept was administered subcutaneously at a dose of 25 mg twice a week for initial 4 weeks as loading dose, followed by 25 mg once a week for subsequent 21 weeks.

Atacicept was administered subcutaneously at a dose of 75 mg twice a week for initial 4 weeks as loading dose, followed by 75 mg once a week for subsequent 21 weeks.

Atacicept was administered subcutaneously at a dose of 150 mg twice a week for initial 4 weeks as loading dose, followed by 150 mg once a week for subsequent 21 weeks.