Three Dose Levels of CP-690,550 Monotherapy Versus Placebo, Administered Orally Twice Daily (BID) for 6 Weeks

ACR20 response: greater than or equal to (>=) 20 percent (%) improvement in tender joints count (TJC); >= 20% improvement in swollen joints count (SJC); and >= 20% improvement in at least 3 of 5 remaining ACR core measures: participant assessment of pain; participant global assessment of disease activity; physician global assessment of disease activity; self-assessed disability (disability index of the Health Assessment Questionnaire [HAQ]); and C-Reactive Protein (CRP).

ACR20 response: >=20% improvement in TJC; >= 20% improvement in SJC; and >= 20% improvement in at least 3 of 5 remaining ACR core measures: participant assessment of pain; participant global assessment of disease activity; physician global assessment of disease activity; self-assessed disability (disability index of the HAQ); and CRP.

ACR50 response: >= 50% improvement in TJC or SJC and 50% improvement in at least 3 of 5 remaining ACR core measures: participant assessment of pain; participant global assessment of disease activity; physician global assessment of disease activity; self-assessed disability (disability index of the HAQ); and CRP.

ACR70 response: >= 70% improvement in TJC or SJC and 70% improvement in at least 3 of 5 remaining ACR core measures: participant assessment of pain; participant global assessment of disease activity; physician global assessment of disease activity; self-assessed disability (disability index of the HAQ); and CRP.

ACR-n: calculated by taking the lowest percentage improvement in (1) SJC or (2) TJC or (3) the median of the remaining 5 components of the ACR response (participant's assessment of disease activity; participant's global assessment of pain; physician's assessment of disease activity; participant's assessment of physical function; an acute phase reactant value - CRP). Negative numbers indicate worsening. The area under the curve (AUC) for ACR-n is the measure of the AUC of the mean change from baseline in ACR-n. The trapezoidal rule was used to compute the AUC.

Number of tender joints was determined by examining 68 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.

Number of tender joints was determined by examining 68 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. A negative value in change from baseline indicated an improvement.

Number of swollen joints was determined by examination of 66 joints and identifying when swelling was present. The number of swollen joints was recorded on the joint assessment form at each visit, no swelling = 0, swelling =1.

Number of swollen joints was determined by examination of 66 joints and identifying when swelling was present. The number of swollen joints was recorded on the joint assessment form at each visit, no swelling = 0, swelling =1. A negative value in change from baseline indicates an improvement.

Participants answered: "Considering all the ways your arthritis affects you, how are you feeling today?" Participants responded by using a 0 - 100 millimeter (mm) Visual Analog Scale (VAS) where 0 mm = very well and 100 mm = very poorly.

Participants answered: "Considering all the ways your arthritis affects you, how are you feeling today?" Participants responded by using a 0 - 100 mm VAS, where 0 mm = very well and 100 mm = very poorly.

Physician Global Assessment of Arthritis was measured on a 0 to 100 mm VAS, where 0 mm = very good and 100 mm = very bad.

Physician Global Assessment of Arthritis was measured on a 0 to 100 mm VAS, where 0 mm = very good and 100 mm = very bad.

Participants rated the severity of arthritis pain on a 0 to 100 mm VAS, where 0 mm = no pain and 100 mm = most severe pain.

Participants rated the severity of arthritis pain on a 0 to 100 mm VAS, where 0 mm = no pain and 100 mm = most severe pain.

HAQ-DI: 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 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 0-3 where 0 = least difficulty and 3 = extreme difficulty.

HAQ-DI: 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 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 0-3 where 0 = least difficulty and 3 = extreme difficulty.

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 0 milligram per liter (mg/L) to 100 mg/L. A decrease in the level of CRP indicates reduction in inflammation and therefore improvement.

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 0 mg/L to 100 mg/L. A decrease in the level of CRP indicates reduction in inflammation and therefore improvement.

DAS28-3 (CRP) was calculated from the SJC and TJC using the 28 joints count and CRP (mg/L). Total score ranging 0 to 9.4; higher scores indicated greater affectation due to disease activity. DAS 28-3 (CRP) less than or equal to (<=) 3.2 implied low disease activity and greater than (>) 3.2 to 5.1 implied moderate to high disease activity, and less than (<) 2.6 = remission.

DAS28-3 (CRP) was calculated from the SJC and TJC using the 28 joints count and CRP (mg/L). Total score ranging 0 to 9.4; higher scores indicated greater affectation due to disease activity. DAS 28-3 (CRP) <=3.2 implied low disease activity and >3.2 to 5.1 implied moderate to high disease activity, and <2.6 = remission.

Disease improvement was classified as good, moderate, and no change based on improvement in DAS 28-3 (CRP) from baseline and present DAS 28-3 (CRP) score. Good: an improvement from baseline of >1.2 and a present score of <=3.2; none: an improvement of <=0.6 or >0.6 to <=1.2 with a present score of >5.1; remaining participants were classified as having moderate improvement. Scores of good and moderate were considered to have therapeutic response.