A Study to Compare Upadacitinib (ABT-494) to Placebo in Adults With Rheumatoid Arthritis (RA) Who Are on a Stable Dose of Conventional Synthetic Disease-Modifying Anti-Rheumatic Drugs (csDMARDs) and Have an Inadequate Response to csDMARDs

Change From Baseline in Disease Activity Score 28 (DAS28) (CRP) at Week 12

The DAS28 is a composite index used to assess rheumatoid arthritis disease activity, calculated based on the tender joint count (out of 28 evaluated joints), swollen joint count (out of 28 evaluated joints), Patient's Global Assessment of Disease Activity (0-100 mm), and hsCRP (in mg/L). Scores on the DAS28 range from 0 to approximately 10, where higher scores indicate more disease activity.

Time frame: Baseline and Week 12

Change From Baseline in Health Assessment Questionnaire - Disability Index (HAQ-DI) at Week 12

The Health Assessment Questionnaire - Disability Index is a patient-reported questionnaire that measures the degree of difficulty a person has in accomplishing tasks in 8 functional areas (dressing, arising, eating, walking, hygiene, reaching, gripping, and errands and chores) over the past week. Participants assessed their ability to do each task on a scale from 0 (without any difficulty) to 3 (unable to do). Scores were averaged to provide an overall score ranging from 0 to 3, where 0 represents no disability and 3 represents very severe, high-dependency disability. A negative change from Baseline in the overall score indicates improvement.

Time frame: Baseline and Week 12

Percentage of Participants With an American College of Rheumatology 50% (ACR50) Response at Week 12

Participants who met the following 3 conditions for improvement from baseline were classified as meeting the ACR50 response criteria: 1. ≥ 50% improvement in 68-tender joint count; 2. ≥ 50% improvement in 66-swollen joint count; and 3. ≥ 50% improvement in at least 3 of the 5 following parameters: * Physician global assessment of disease activity * Patient global assessment of disease activity * Patient assessment of pain * Health Assessment Questionnaire - Disability Index (HAQ-DI) * High-sensitivity C-reactive protein (hsCRP).

Time frame: Baseline and Week 12

Percentage of Participants With an American College of Rheumatology 70% (ACR70) Response at Week 12

Participants who met the following 3 conditions for improvement from baseline were classified as meeting the ACR70 response criteria: 1. ≥ 70% improvement in 68-tender joint count; 2. ≥ 70% improvement in 66-swollen joint count; and 3. ≥ 70% improvement in at least 3 of the 5 following parameters: * Physician global assessment of disease activity * Patient global assessment of disease activity * Patient assessment of pain * Health Assessment Questionnaire - Disability Index (HAQ-DI) * High-sensitivity C-reactive protein (hsCRP).

Time frame: Baseline and Week 12

Change From Baseline in Short-Form 36 (SF-36) Physical Component Score (PCS) at Week 12

The Short Form 36-Item Health Survey (SF-36) Version 2 is a self-administered questionnaire that measures the impact of disease on overall quality of life during the past 4 weeks. The SF-36 consists of 36 questions in eight domains (physical function, pain, general and mental health, vitality, social function, physical and emotional health). The physical component score is a weighted combination of the 8 subscales with positive weighting for physical functioning, role-physical, bodily pain, and general health. The PCS was calculated using norm-based scoring so that 50 is the average score and the standard deviation equals 10. Higher scores are associated with better functioning/quality of life; a positive change from baseline score indicates an improvement.

Time frame: Baseline and Week 12

Percentage of Participants Achieving Low Disease Activity (LDA) Based on DAS28(CRP) at Week 12

Low disease activity. was defined as a DAS28 score less than or equal to 3.2. The DAS28 is a composite index used to assess rheumatoid arthritis disease activity, calculated based on the tender joint count (out of 28 evaluated joints), swollen joint count (out of 28 evaluated joints), Patient's Global Assessment of Disease Activity (0-100 mm), and hsCRP (in mg/L). Scores on the DAS28 range from 0 to approximately 10, where higher scores indicate more disease activity.

Time frame: Week 12

Percentage of Participants Achieving Clinical Remission (CR) Based on DAS28(CRP) at Week 12

Clinical remission was defined as a DAS28 (CRP) score less than 2.6. The DAS28 is a composite index used to assess rheumatoid arthritis disease activity, calculated based on the tender joint count (out of 28 evaluated joints), swollen joint count (out of 28 evaluated joints), Patient's Global Assessment of Disease Activity (0-100 mm), and hsCRP (in mg/L). Scores on the DAS28 range from 0 to approximately 10, where higher scores indicate more disease activity.

Time frame: Week 12

Percentage of Participants With an American College of Rheumatology 20% (ACR20) Response at Week 1

Participants who met the following 3 conditions for improvement from baseline were classified as meeting the ACR20 response criteria: 1. ≥ 20% improvement in 68-tender joint count; 2. ≥ 20% improvement in 66-swollen joint count; and 3. ≥ 20% improvement in at least 3 of the 5 following parameters: * Physician global assessment of disease activity * Patient global assessment of disease activity * Patient assessment of pain * Health Assessment Questionnaire - Disability Index (HAQ-DI) * High-sensitivity C-reactive protein (hsCRP).

Time frame: Baseline and Week 1

Change From Baseline in in Functional Assessment of Chronic Illness Therapy - Fatigue (FACIT-F) at Week 12

The FACIT Fatigue scale is a 13-item tool that measures an individual's level of fatigue during their usual daily activities over the past 7 days. Each of the fatigue and impact of fatigue items are measured on a four point Likert scale. The FACIT Fatigue Scale is the sum of the individual 13 scores and ranges from 0 to 52 where higher scores indicate better quality of life. A positive change from Baseline indicates improvement.

Time frame: Baseline and Week 12

Change From Baseline in Rheumatoid Arthritis Work Instability Scale (RA-WIS) at Week 12

RA-WIS is a simple validated tool to evaluate work instability (the consequence of a mismatch between an individual's functional ability and their work tasks). RA-WIS consists of 23 questions relating to the participant's functioning in their work environment, each answered as Yes or No. The total score is the number of questions answered Yes, and ranges from 0 to 23. A score \< 10 means low risk and no action is needed, scores between 10 and 17 indicate medium risk and appropriate advice and information should be given. If the score is \> 17, it means high risk and it could warrant referral. A negative change from Baseline indicates improvement.

Time frame: Baseline and Week 12

Change From Baseline in the Severity of Morning Stiffness at Week 12

Morning stiffness severity was determined by the Patient's Assessment of Severity and Duration of Morning Stiffness questionnaire. Participants rated the severity of morning stiffness on awakening over the past 7 days on a scale from 0 (No morning stiffness) to 10 (Worst possible morning stiffness).

Time frame: Baseline and Week 12