Placebo was supplied as a sterile liquid in single-use vials for iv administration.

The synovitis score was determined according to the Outcome Measures in Rheumatology (OMERACT) rheumatoid arthritis MRI scoring (RAMRIS) system in magnetic resonance images of 3 wrist regions and 5 metacarpophalangeal joints in the hand and wrist with the most arthritic activity. If there was no difference in disease activity between the hands, the dominant hand was used. Images were assessed by 2 experienced blinded musculoskeletal radiologists. Each location was scored in 0.5 increments from 0 to 3 with each integer unit increment representing a 33% enhancement of the maximum volume of enhancing tissue in the synovial compartment using the following scale: 0.0=normal, no synovitis; 0.5=1-17% estimated volume of enhancement; 1.0=18-33%; 1.5=34-50%; 2.0=51-67%; 2.5=68-83%; 3.0=84-100% estimated volume of enhancement. The individual scores were summed and normalized to a range of 0 to 100 with a higher score indicating more synovitis. A negative change score indicates improvement.

The osteitis score was determined according to the Outcome Measures in Rheumatology (OMERACT) rheumatoid arthritis MRI scoring (RAMRIS) system in magnetic resonance images of 15 anatomical locations in each wrist and 10 locations in each hand in the hand and wrist with the most arthritic activity. If there was no difference in disease activity between the hands, the dominant hand was used. Each location was scored in 0.5 increments from 0 to 3 with each integer unit increment representing a 33% increase in the volume of the peripheral 1 cm of original (eroded + residual) articular bone using the following scale: 0.0=normal, no osteitis; 0.5=1-17% involvement of original articular bone; 1.0=18-33%; 1.5=34-50%; 2.0=51-67%; 2.5=68-83%; 3.0=84-100% involvement of original articular bone. The individual scores were summed and normalized to a range of 0 to 100 with a higher score indicating more synovitis. A negative change score indicates improvement.

No newly eroded joints was defined as no new erosions in joints which were scored 0 at baseline. The erosion score was determined according to the Outcome Measures in Rheumatology (OMERACT) rheumatoid arthritis MRI scoring (RAMRIS) system in magnetic resonance images with and without gadolinium of 15 anatomical locations in each wrist and 10 locations in each hand in the hand and wrist with the most arthritic activity. If there was no difference in disease activity between the hands, the dominant hand was used. Images were assessed by 2 experienced blinded musculoskeletal radiologists. Each location was scored in 0.5 increments from 0 to 10 with each integer unit increment representing a 10% loss of articular bone using the following scale. 0.0=normal, no erosion; 0.5=1-5% erosion; 1.0=6-10% erosion; 1.5=11-15% erosion; 2.0=16-20% erosion; etc, up to 10.0=96-100% erosion.

There were 2 definitions of no progression/no worsening in bone erosion. A participant met the criterion for definition 1 when there was a change in the magnetic resonance imaging erosion score ≤ 0. A participant met the criteria for definition 2 when there was either (1) no change from Baseline in the MRI erosion score, (2) an increase in erosion score and the size of the increase in score was smaller than the smallest detectable change, or (3) a drop in the erosion score. The erosion score was determined according to the Outcome Measures in Rheumatology (OMERACT) rheumatoid arthritis MRI scoring (RAMRIS) system in magnetic resonance images with and without gadolinium of 15 anatomical locations in each wrist and 10 locations in each hand in the hand and wrist with the most arthritic activity. If there was no difference in disease activity between the hands, the dominant hand was used. Images were assessed by 2 experienced blinded musculoskeletal radiologists.

There were 2 definitions of improvement in synovitis. A participant met the criterion for definition 1 when there was a drop in the magnetic resonance imaging synovitis score from Baseline > 0.5. A participant met the criterion for definition 2 when there was a drop in the magnetic resonance imaging synovitis score from Baseline > than the smallest detectable change. The synovitis score was determined according to the Outcome Measures in Rheumatology (OMERACT) rheumatoid arthritis MRI (RAMRIS) scoring system in magnetic resonance images with and without gadolinium of 15 anatomical locations in each wrist and 10 locations in each hand in the hand and wrist with the most arthritic activity. If there was no difference in disease activity between the hands, the dominant hand was used. Images were assessed by 2 experienced blinded musculoskeletal radiologists.

There were 2 definitions of improvement in osteitis. A participant met the criterion for definition 1 when there was a drop in the magnetic resonance imaging osteitis score from Baseline > 0.5. A participant met the criterion for definition 2 when there was a drop in the magnetic resonance imaging osteitis score from Baseline > than the smallest detectable change. The osteitis score was determined according to the Outcome Measures in Rheumatology (OMERACT) rheumatoid arthritis MRI (RAMRIS) scoring system in magnetic resonance images with and without gadolinium of 15 anatomical locations in each wrist and 10 locations in each hand in the hand and wrist with the most arthritic activity. If there was no difference in disease activity between the hands, the dominant hand was used. Images were assessed by 2 experienced blinded musculoskeletal radiologists.

The DAS28 is a combined index for measuring disease activity in rheumatic arthritis (RA) and includes swollen and tender joint counts, C-reactive protein level (CRP), and general health (GH) status. The index is calculated with the following formula: DAS28 = (0.56 × √(TJC28)) + (0.28 × √(SJC28)) + (0.7 × log(CRO)) + (0.014 × GH), where TJC28 = tender joint count and SJC28 = swollen joint count, each on 28 joints, GH = a participant's global assessment of disease activity in the previous 24 hours on a 100 mm visual analog scale (left end = no disease activity [symptom-free and no arthritis symptoms], right end = maximum disease activity [maximum arthritis disease activity]). The DAS28 scale ranges from 0 to 10, where higher scores represent higher disease activity. A negative change score indicates improvement.

Change of the DAS28 score from Baseline was used to determine the EULAR responses. For a post-Baseline score ≤ 3.2, a change from Baseline of < -1.2 was a good response, < -0.6 to ≥ -1.2 was a moderate response, and ≥ -0.6 was no response. For a post-Baseline score > 3.2 to ≤ 5.1, a change from Baseline of < -0.6 was a moderate response and ≥ -0.6 was no response. For a post-Baseline score > 5.1, a change from Baseline < -1.2 was a moderate response and ≥ -1.2 was no response. A good response could not be achieved for post-Baseline scores > 3.2. DAS28=(0.56×√(TJC28))+(0.28×√(SJC28))+(0.7×log(CRP))+(0.014×GH), where TJC28=tender joint count (JC) and SJC28=swollen JC (28 joints), GH=a participant's global assessment of disease activity in the previous 24 hours on a 100 mm visual analog scale (left end=no disease activity, right end=maximum disease activity), and CRP=C-reactive protein level. The DAS28 scale ranges from 0 to 10, where higher scores represent higher disease activity.

The percentage of participants who had low rheumatic arthritis disease activity at Weeks 24 and 52, as measured by a DAS28 score ≤ 3.2, is reported. DAS28 is calculated with the following formula: DAS28 = (0.56 × √(TJC28)) + (0.28 × √(SJC28)) + (0.7 × log(CRO)) + (0.014 × GH), where TJC28 = tender joint count and SJC28 = swollen joint count, each on 28 joints, GH = a participant's global assessment of disease activity in the previous 24 hours on a 100 mm visual analog scale (left end = no disease activity [symptom-free and no arthritis symptoms], right end = maximum disease activity [maximum arthritis disease activity]), and CRP = C-reactive protein level. The DAS28 scale ranges from 0 to 10, where higher scores represent higher disease activity.

The percentage of participants in remission of their rheumatic arthritis at Weeks 24 and 52, as measured by a DAS28 score < 2.6, is reported. DAS28 is calculated with the following formula: DAS28 = (0.56 × √(TJC28)) + (0.28 × √(SJC28)) + (0.7 × log(CRO)) + (0.014 × GH), where TJC28 = tender joint count and SJC28 = swollen joint count, each on 28 joints, GH = a participant's global assessment of disease activity in the previous 24 hours on a 100 mm visual analog scale (left end = no disease activity [symptom-free and no arthritis symptoms], right end = maximum disease activity [maximum arthritis disease activity]), and CRP = C-reactive protein level. The DAS28 scale ranges from 0 to 10, where higher scores represent higher disease activity.

Improvement must be seen in tender and swollen joint counts (28 assessed joints; Joints were evaluated and classified as swollen or not swollen and tender or not tender based on pressure and joint manipulation upon physical examination) and in at least 3

A major clinical response was defined as an improvement of at least 70% in the American College of Rheumatology score from Baseline at Week 52. Improvement must be seen in tender and swollen joint counts (28 assessed joints) and in at least 3 of the following 5 parameters: Separate participant and physician assessments of participant disease activity in the previous 24 hours on a visual analog scale (VAS, the extreme left end of the line "no disease activity" [symptom-free and no arthritis symptoms] and the extreme right end "maximum disease activity"); participant assessment of pain in previous the 24 hours on a VAS (extreme left end of the line "no pain" and the extreme right end "unbearable pain"); Health Assessment Questionnaire-Disability Index (20 questions, 8 components: dressing/grooming, arising, eating, walking, hygiene, reach, grip, and activities, 0=without difficulty to 3=unable to do); and C reactive protein level.

Correlation coefficients of magnetic resonance imaging erosion, synovitis, and osteitis scores and clinical outcome measures of swollen joint count (SJC), tender joint count (TJC), C-reactive protein level (CRP), erythrocyte sedimentation rate (ESR), a participant's global assessment of disease activity in the previous 24 hours on a 100 mm visual analog scale (GH), Disease Activity Score 28-C-reactive protein (DAS28-CRP), and Disease Activity Score 28-erythrocyte sedimentation rate (DAS28-ESR) are reported. Not all of these variables were specified as primary or secondary Outcome Measures in the study protocol and were not individually analyzed.

The HAQ-DI assesses how well the patient is able to perform 8 activities: Dressing/grooming, arising, eating, walking, hygiene, reach, grip, and activities. The patient answers 20 questions with 1 of 4 responses with the past week as the time frame: 0=without difficulty, 1=with some difficulty, 2=with much difficulty, and 3=unable to do. The highest score for any question in a category determines the category score. The total score ranges from 0 (no disability) to 3 (completely disabled). A negative change score indicates improvement.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received rituximab 1000 mg iv on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants received further treatment courses on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.

Participants received placebo intravenously (iv) on Day 1 and Day 15 of the main study. Participants received a second course of treatment on Day 1 and Day 15 after Week 24 of the main study, if they met eligibility criteria (see the Detailed Description). Participants were switched to receive rituximab 1000 mg iv on Day 1 and Day 15 at intervals of ≥ 6 months after Week 52 in the study extension phase, if they met eligibility criteria (see the Detailed Description). Throughout the study, participants received methylprednisolone 100 mg iv prior to infusion of the investigational drug, methotrexate 7.5 to 25 mg/week orally or parenterally, and folic acid or folate ≥ 5 mg/week orally.