ACR Responder Index: composite of clinical, laboratory, and functional measures of rheumatoid arthritis (RA). ACR20 Responder: a ≥20% improvement from baseline in both 68 tender joint counts (TJC) and 66 swollen joint counts (SJC) and a ≥20% improvement in at least 3 of 5 criteria: participant's and physician's global assessment of disease activity, Health Assessment Questionnaire-Disability Index (HAQ-DI) (which measured participants' perceived degree of difficulty performing daily activities), joint pain, and C-reactive protein (CRP). Percentage of participants achieving ACR20 response = (number of ACR20 responders / number of participants treated) * 100. All NR at Week 16, as well as all participants who discontinued study treatment at any time for any reason, were defined as NR starting at that time-point and going forward, including Week 24 endpoint.

All randomized participants with evaluable ACR20 responder data. If participant's CRP was missing, last post-baseline value was used. If ACR was missing after carrying forward CRP, last post-baseline ACR response was used. Data after Week 16 for Week 16 NR were not included.

ACR Responder Index: composite of clinical, laboratory, and functional measures of RA. ACR50 Responder: had a ≥50% improvement from baseline in both 68 TJC and 66 SJC and a ≥50% improvement in at least 3 of 5 criteria: participant's (Pt's) and physician's global assessment of disease activity, HAQ-DI (measured Pts' perceived degree of difficulty performing daily activities), joint pain, and CRP. Percentage of Pt achieving ACR50 response = [number (No.) of ACR50 responders / No. of Pts treated]*100. ACR70 Responder: had a ≥70% improvement from baseline in both TJC and SJC and a ≥70% improvement in at least 3 of same 5 criteria for ACR50. Percentage of Pts achieving ACR70 response = (No. of ACR70 responders / No. of Pts treated)*100. All NR at Week 16, as well as all Pts who discontinued study treatment at any time for any reason, were defined as NR starting at that time-point and going forward, including Week 24 endpoint.

All randomized participants with evaluable ACR50 or ACR70 responder data. If participant's CRP was missing, last post-baseline value was used. If ACR was missing after carrying forward CRP, last post-baseline ACR response was used. Data after Week 16 for Week 16 NR were not included.

ACR-N is a continuous measure of clinical, laboratory, and functional outcomes in RA that characterizes percentage (%) of improvement in disease activity from baseline based on ACR core set. This index was calculated as minimum of either a) % change in TJC, b) % change in SJC, or c) the median % change of remaining 5 ACR core criteria: If ≥3 components of the 5 ACR core criteria were missing, then c) was set to missing; if any of 3 components a), b), or c) were missing, then ACR-N was set to missing. Percentage of improvement was truncated to range of -100 to 100 to minimize impact of outliers (greater values indicate greater % improvement) and negative scores indicate a decline. Least Squares (LS) means were calculated using analysis of covariance (ANCOVA) with treatment and region as fixed factors and baseline Disease Activity Score based on 28 joint counts -CRP (DAS28-CRP) as a covariate.

All randomized participants with evaluable ACR-N data. Modified Baseline Observation Carried Forward (mBOCF) was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Tender joint count is the number of tender and painful joints determined for each participant by examination of 68 joints. Joints were assessed by pressure and joint manipulation on physical examination. Participants were asked for pain sensations on these manipulations and watched for spontaneous pain reactions. Any positive response on pressure, movement, or both was translated into a single tender-versus-nontender dichotomy. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable tender joint count data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Swollen joint count is the number of swollen joints determined for each participant by examination of 66 joints. Joints were classified as either swollen or not swollen. Swelling was defined as palpable fluctuating synovitis of the joint. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable swollen joint count data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Participant's assessment of their current arthritis pain using VAS ranged from 0 millimeters (mm) (no pain) to 100 mm (worst possible pain). A decrease in pain score indicated an improvement in the participant's condition. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable participant's assessment of pain data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Participant's assessment of their current arthritis disease activity using VAS ranged from 0 mm (no arthritis activity) to 100 mm (extremely active arthritis). A decrease in disease activity score indicated an improvement in the participant's condition. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable participant's global assessment of disease activity data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Physician's assessment of the participant's current arthritis disease activity using VAS ranged from 0 mm (no arthritis activity) to 100 mm (extremely active arthritis). A decrease in disease activity score indicated an improvement in the participant's condition. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable physician's global assessment of disease activity data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

The HAQ-DI questionnaire assesses the participant's self-perception on the degree of difficulty [0 (without any difficulty), 1 (with some difficulty), 2 (with much difficulty), and 3 (unable to do)] when dressing and grooming, arising, eating, walking, hygiene, reaching, gripping, and performing other daily activities. Scores for each functional area were averaged to calculate HAQ-DI scores, which ranged from 0 (no disability) to 3 (severe disability). A decrease in HAQ-DI score indicated an improvement in the participant's condition. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable HAQ-DI data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Disease Activity Score (DAS) modified to include 28 joint count (DAS28) consisted of composite score of following variables: tender joint count (TJC28), swollen joint count (SJC28), CRP (milligrams per liter), and participant's global assessment of disease activity using VAS (participant global VAS). DAS28-CRP=0.56*square root (sqrt)(TJC28)+0.28*sqrt(SJC28)+0.36*natural log(CRP+1)+0.014*participant global VAS+0.96. Scores ranged from 1.0 to 9.4, where lower scores indicated less disease activity and remission is DAS28-CRP <2.6. A decrease in DAS28-CRP indicated an improvement in participant's condition. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable DAS28-CRP data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

EULAR Responder index categorizes clinical response based on improvement since baseline in DAS28-CRP. DAS28-CRP=0.56*sqrt(TJC28)+0.28*sqrt(SJC28)+0.36*natural log(CRP+1)+0.014*participant global VAS+0.96. DAS28-CRP scores range from 1.0-9.4, where lower scores indicated less disease activity. High disease activity: DAS28-CRP >5.1, low disease activity: DAS28-CRP <3.2, and remission: DAS28-CRP <2.6. Participants are categorized as EULAR responders or NR based on improvement of DAS28-CRP scores from baseline. EULAR DAS28-CRP responder index defines a good (absolute: <3.2 or >1.2 improvement from baseline), moderate (absolute: 3.2-5.1 or 0.6-1.2 improvement from baseline), or no response (absolute: >5.1 or <0.6 improvement from baseline). Percentage of participants with DAS28-CRP based EULAR response = ( number of participants with specific response) / (number of participants analyzed in the group) * 100.

All randomized participants with evaluable EULAR response data. Modified Last Observation Carried Forward (mLOCF) was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

SF-36 is a health-related survey that assesses participant's quality of life and consists of 36 questions covering 8 health domains: physical functioning, bodily pain, role limitations due to physical problems and emotional problems, general health, mental health, social functioning, vitality, 2 component scores (CS), physical CS (PCS) and mental CS (MCS). Domain scores calculated by summing each item for each domain and transforming scores into 0-100 scale; higher scores indicated better health status. If < 50% of the questions within a domain were answered, the raw score were not calculated. PCS score consisted of physical functioning, bodily pain, role-physical, and general health scales. MCS score consisted of social functioning, vitality, mental health, and role-emotional scales. Both PCS and MCS range from 0-100 with higher score indicating better mental or physical health. LS means were calculated using ANCOVA with treatment, region as fixed factors and baseline as a covariate.

All randomized participants with evaluable SF-36 domain and summary scores. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

The BFI is a brief participant-reported questionnaire for the rapid assessment of fatigue severity and the impact of fatigue on daily functioning in the past 24 hours. The BFI contains 10 items; however, the first item is not included in the scoring of the scale as it asks about usual fatigue over the past week with the participant answering 'yes' or 'no'. The remaining 9 items assess fatigue severity (3 items) and impact of fatigue on daily functioning (6 items) using an 11-point numeric scale, with 0 = no fatigue and 10 = fatigue as bad as you can imagine. The fatigue impact subscale score is the average of the non-missing responses to 6 items: general activity, mood, walking ability, normal work, relations with other people, and enjoyment of life. If more than 3 items within the fatigue impact subscale were not answered by a participant, the subscale is set to missing. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable BFI data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

The BPI-SF is a self-reported scale that measures the severity of pain based on the worst pain, least pain, average pain experienced during the past 24 hours and pain based on the pain right now, with scores ranging from 0 (no pain) to 10 (pain as severe as you can imagine). Pain interference score is the average of the responses in the past 24 hours to 7 items: general activity, mood, walking ability, normal work, relations with other people, sleep, and enjoyment of life [each item scored from 0 (does not interfere) to 10 (completely interferes)]. If more than 3 items of the Pain Interference Score are not answered by a participant, the score is set to missing. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable BPI-SF scores. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

The Investigator asks participants about the duration of their morning stiffness (in minutes) in and around the joints and records the duration. The Investigator should ask participants about duration of morning stiffness on the day prior to the study visit to capture actual symptoms. If morning stiffness duration is longer than 12 hours (720 minutes), it was truncated to 720 minutes for statistical presentations and analyses.LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable morning stiffness data; mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Zero participants analyzed. Time to ACR20 data not collected for analysis.

Cell-surface marker cluster designation (CD) 3 negative, CD20 positive (CD3-CD20+) defines total mature B cells. B-lymphocyte antigen CD20 is an activated-glycosylated phosphoprotein expressed on the surface of all mature B cells. Baseline B cell count is the average of the values on or prior to the date of first injection of study treatment, including unscheduled visits. A positive or negative change indicated an increase or decrease, respectively in B cell count. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable CD3-CD20+ B cell counts. mLOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Immunoglobulin (Ig), or antibodies, are large proteins used by the immune system to identify and neutralize foreign particles such as bacteria and viruses. Their normal blood levels indicate proper immune status. Change from baseline in serum immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels are reported. A negative change indicated a decrease in Ig levels. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable serum Ig data. mLOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.

Population estimate of constant clearance as determined by population PK analysis. A 2-compartment model was used in PK modeling. Constant clearance is the PK parameter which describes the linear elimination of LY2127399 from serum.

All randomized participants who received at least 1 dose of LY2127399 with evaluable LY2127399 PK data.

Participants with treatment-emergent anti-drug antibody (ADA) were participants who had any sample from baseline up to and through Week 52 that was a 4-fold increase (2-dilution increase) in immunogenicity titer over baseline titer, or participants who tested negative at baseline and positive post-baseline (at titer of ≥1:20). Percentage of participants with ADA = (number of participants with treatment-emergent ADA) / (number of participants assessed) * 100.

All randomized participants who received at least 1 dose of study drug with an evaluable baseline ADA result and a post-baseline ADA result. Participants missing an evaluable baseline result with all negative post-baseline results were included. Data after Week 16 for Week 16 NR were not included.

CRP is an indicator of inflammation. A negative change indicated an improvement in the participant's condition. LS means were calculated using ANCOVA with treatment and region as fixed factors and baseline as a covariate.

All randomized participants with evaluable CRP data. mBOCF was used to impute missing post-baseline values. Data after Week 16 for Week 16 NR were not included.