DAS28-4 (CRP) examines progression or improvement of RA. It was assessed from swollen joint count (SJC) and tender joint count (TJC) using the 28 joints count, CRP (normal range of CRP is less than (<) 10 milligram per liter [mg/L], decrease in the level of CRP indicates reduction in inflammation) and participant global assessment (PGA) of disease activity (participant global assessment of diseases condition scores ranging from 0 [very well condition] to 100 [very poor condition], higher scores indicated greater affectation due to disease activity). Total DAS28-4 (CRP) transformed score range: 0 (least severe) to 10 (most severe), higher scores indicate more severe disease activity. DAS28-4 (CRP) scores: less than equal to (<=) 3.2 implied low disease activity; greater than (>) 3.2 to 5.1 implied moderate to high disease activity.

The full analysis set (FAS) included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Number of tender joints was determined by examining 28 joints and identified the joints that were painful under pressure or to passive motion. The number of tender joints was recorded on the joint assessment form at each visit, no tenderness = 0, tenderness = 1.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Number of swollen joints was determined by examination of 28 joints and identifying if swelling was present. The number of swollen joints was recorded on the joint assessment form at each visit, no swelling = 0, swelling =1.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

The test for CRP is a laboratory measurement for evaluation of an acute phase reactant of inflammation through the use of an ultrasensitive assay. Normal range of CRP is less than (<) 10 mg/L. A decrease in the level of CRP indicates reduction in inflammation and therefore improvement.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

HAQ-DI assessed the ability of participants to perform task in 8 domains of daily living activities: dress/groom, arise, eat, walk, reach, grip, hygiene, and common activities. Each item was scored on a 4-point scale ranging from 0 to 3: 0= no difficulty; 1= some difficulty; 2= much difficulty; 3= unable to do, higher scores indicate more difficulty. Overall score was computed as the sum of domain scores and divided by the number of domains answered. Total possible HAQ-DI score range: 0 (no difficulty) to 3 (extreme difficulty), where higher scores indicate more difficulty while performing daily living activities.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Participant assessment of arthritis pain included assessment of severity of arthritis pain using a 100 millimeter (mm) visual analog scale (VAS). Participants placed a mark on the VAS between 0 mm (no pain) and 100 mm (most severe pain), which corresponded to the magnitude of their pain, higher scores indicate more pain.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

PGA was a questionnaire where participants answered the following question, "Considering all the ways your arthritis affects you, how are you feeling today?" The participants' response were recorded using a 100 mm visual analog scale placing a mark on the scale, between 0 mm (very well condition) to 100 mm (very poor condition). Higher scores indicate higher degree of arthritis.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

PhGA included assessment of severity of arthritis pain where physicians were asked to rate the severity of the participant's overall arthritis. The physician's response was recorded using a visual analog scale between 0 mm (very good condition) to 100 mm (very poor condition). Higher scores indicate higher degree of arthritis.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

SF-36 is a standardized survey evaluating 8 aspects of functional health and well-being: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional and mental health. Score for each of the 8 aspects are scaled from 0 (worst condition) to 100 (best condition), where higher scores indicate better health status. These 8 domains were also reported as two summary scores: physical component scores and mental component scores. Score range for each of the 2 summary scores = 0 (worst condition) to 100 (best condition), where higher scores represent better health status.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

DAS28-3 (CRP) was calculated from the swollen joint count and tender joint count using the 28 joints count and CRP (normal range of CRP is <10 mg/L, decrease in the level of CRP indicates reduction in inflammation). Total DAS28-3 (CRP) score range: 0 (least severe) to 9.4 (most severe), higher scores indicate more disease activity.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

DAS28-4 (CRP) examines progression or improvement of RA. It was assessed from SJC and TJC using the 28 joints count, CRP (normal range of CRP is <10 mg/L, decrease in the level of CRP indicates reduction in inflammation) and PGA of disease activity (participant global assessment of diseases condition scores ranging from 0 [very well condition] to 100 [very poor condition], higher scores indicated greater affectation due to disease activity). Total DAS28-4 (CRP) transformed score range: 0 (least severe) to 10 (most severe), higher scores indicate more severe disease activity. DAS28-4 (CRP) scores: <=3.2 implied low disease activity; >3.2 to 5.1 implied moderate to high disease activity.

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'Number of Participants analyzed' signifies those participants who were evaluable for this outcome measure.

ACR20 responder: participants who achieved at =20% improvement in tender and swollen 28-joints count, and >=20% improvement in at least 3 of the following 5 measures: 1) participant's assessment of arthritis pain (participant's self-assessed severity of arthritis pain, score range from 0[no pain] to 100[most severe pain], higher scores=more pain), 2) PGA of arthritis (participant's assessed overall arthritis activity, score range from 0[no arthritis] to 100[extreme arthritis], higher scores=higher degree of arthritis), 3) PhGA of arthritis (physician rated severity of participants overall arthritis activity, score range from 0[no arthritis] to 100[extreme arthritis], higher scores=higher degree of arthritis), 4) HAQ-DI (assessment of functional disability, score range from 0[no difficulty] to 3[extreme difficulty], higher scores=more functional limitation) and 5) CRP (assessment of inflammation, normal range of CRP is <10 mg/L, decrease in the level of CRP=reduction in inflammation).

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

ACR50 responder: participants who achieved at =50% improvement in tender and swollen 28-joints count, and >=50% improvement in at least 3 of the following 5 measures: 1) participant's assessment of arthritis pain (participant's self-assessed severity of arthritis pain, score range from 0[no pain] to 100[most severe pain], higher scores=more pain), 2) PGA of arthritis (participant's assessed overall arthritis activity, score range from 0[no arthritis] to 100[extreme arthritis], higher scores=higher degree of arthritis), 3) PhGA of arthritis (physician rated severity of participants overall arthritis activity, score range from 0[no arthritis] to 100[extreme arthritis], higher scores=higher degree of arthritis), 4) HAQ-DI (assessment of functional disability, score range from 0[no difficulty] to 3[extreme difficulty], higher scores=more functional limitation) and 5) CRP (assessment of inflammation, normal range of CRP is <10 mg/L, decrease in the level of CRP=reduction in inflammation).

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

ACR70 responder: participants who achieved at =70% improvement in tender and swollen 28-joints count, and >=70% improvement in at least 3 of the following 5 measures: 1) participant's assessment of arthritis pain (participant's self-assessed severity of arthritis pain, score range from 0[no pain] to 100[most severe pain], higher scores=more pain), 2) PGA of arthritis (participant's assessed overall arthritis activity, score range from 0[no arthritis] to 100[extreme arthritis], higher scores=higher degree of arthritis), 3) PhGA of arthritis (physician rated severity of participants overall arthritis activity, score range from 0[no arthritis] to 100[extreme arthritis], higher scores=higher degree of arthritis), 4) HAQ-DI (assessment of functional disability, score range from 0[no difficulty] to 3[extreme difficulty], higher scores=more functional limitation) and 5) CRP (assessment of inflammation, normal range of CRP is <10 mg/L, decrease in the level of CRP=reduction in inflammation).

FAS included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

An AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. An SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. Treatment-emergent are events between first dose of study drug and up to 31 days after last dose (Day 45) that were absent before treatment or that worsened relative to pretreatment state.

Safety analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug.

Criteria for laboratory abnormalities: Hematology (hemoglobin, hematocrit <0.8*baseline; platelet count <75 or >700*10^3 per mm^3; leucocytes <2.5 or >17.5*10^3 per mm^3); chemistry (total bilirubin >1.5*upper limit of reference range [ULN]; aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transpeptidase, alkaline phosphatase, >3.0*ULN; total protein, albumin <0.8*lower limit of reference range [LLN] or >1.2*ULN; blood urea nitrogen [BUN]/urea, creatinine >1.3*ULN; glucose [fasting] <0.6*LLN or >1.5*ULN; uric acid >1.2*ULN; sodium <0.95*LLN or >1.05*ULN; potassium, calcium <0.9*LLN or >1.1*ULN; albumin, total protein <0.8*LLN or >1.2*ULN; urinalysis (urine white blood cell (WBC) =>6/ high power field (hpf); urine red blood cell (RBC) =>6/hpf). Number of participants with clinically significant change from baseline in laboratory abnormalities identified by investigator were reported.

Safety analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug.

Safety analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Following parameters were analyzed for examination of vital signs: systolic and diastolic blood pressure, heart rate and body temperature. Vital sign measurements were performed with the participant in the seated position. Clinical significance vital sign abnormality was determined by investigator.

Safety analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug.

Clinically significant ECG findings included PR interval >=300 milliseconds (msec) or >=25% increase from baseline (if baseline PR interval >200 msec) or >=50% increase (if baseline PR interval less than or equal to [<=] 200 msec); QRS interval >=200 msec or >=25% increase from baseline (if baseline PR interval >100 msec) or >=50% increase (if baseline PR interval <= 100 msec); QT interval >=500 msec, corrected QT interval >=500 msec.

Safety analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug.

Plasma concentration of PF-00251802 versus time summary, a metabolite of PF-04171327 was reported in this outcome measure.

Analysis set included all randomized participants who received at least 1 dose of PF-04171327. Here, 'Number of Participants analyzed' signifies those participants who were evaluable for this outcome measure. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood. Methotrexate was used as a background therapy by participants.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'Number of Participants analyzed' signifies those participants who were evaluable for this outcome measure.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Unit of ratio of urinary N-terminal telopeptide of type 1 collagen (uNTX-I) level to urinary creatinine (uCr) level was nanomoles bone collagen equivalents (nmol bce) per millimole creatinine (mmol cr).

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.

Analysis set included all randomized participants who received at least 1 dose of the randomized investigational drug. Here, 'n' signifies those participants who were evaluable at specified time points, respectively.