A Study Exploring the Safety, Tolerability, and Efficacy of a 28 Day Course Followed by an Additional 56 Day Course of Itacitinib in Subjects With Active Rheumatoid Arthritis

Inclusion Criteria: * Subjects with active RA aged 18 to 75 years of age and meet tender and swollen joint assessment expectations defined in the study protocol. * c-Reactive protein (CRP) or erythrocyte sedimentation rate (ESR) laboratory values meet minimal study protocol expectations. Exclusion Criteria: * Females who are pregnant or breastfeeding. * Men and women who cannot comply with requirements to avoid fathering a child or becoming pregnant, respectively. * Subjects treated with a biologic agent within 12 weeks prior to first dose of study drug. (12 months in the case of rituximab.) * Subjects with a history or currently suspected inflammatory disease other than RA. * Subjects with a history of hematological disorders.