Efficacy and Safety Study of CC-292 Versus Placebo as Co-therapy With Methotrexate in Active Rheumatoid Arthritis

Inclusion Criteria: * Female between 18 and 80 years of age (inclusive) at the time of signing the informed consent. * Must meet the 2010 ACR/EULAR Classification Criteria for RA (Appendix A), have RA for at least 6 months and must continue to have active RA at the time of randomization despite at least 3 months of treatment with stable doses of MTX (7.5 to 25 mg/week oral or parenteral) for at least 4 weeks prior to randomization. * Must have been treated with MTX for at least 3 months prior to randomization, and must be on a stable dose between 7.5 and 25 mg/week (PO or parenteral, not both) for at least 4 weeks prior to randomization. Subjects will be required to maintain their stable dose through Day 28/Week 4 of the study. Oral folate supplementation is required with a minimum dose of 5 mg/week (ie, folic acid) while the subject is taking MTX. Leucovorin may be used instead of folic acid and may be dosed up to 10 mg/week orally. * Sulfasalazine is allowed as a concomitant medication, however, subject must be on a stable dose for at least 4 weeks prior to randomization and through Day 28/Week 4 of the study. * Hydroxychloroquine or chloroquine is allowed as concomitant medications, however, subject must be on a stable dose for at least 4 weeks prior to randomization and through Day 28/Week 4 of the study. * Modification of Diet in Renal Disease formula (MDRD) estimated glomerular filtration rate (MDRD eGFR) ≥ 60 mL/min/1.73m2+ Exclusion Criteria: * Male subjects * Any condition that could affect CC-292 absorption, including gastric restrictions, bariatric surgery, such as gastric bypass, and clinical conditions that are associated with decreased intragastric acid production such as acid pernicious anemia. * Currently using treatment with DMARDs (other than sulfasalazine, hydroxychloroquine or chloroquine and MTX), including biologics. Previous use is only allowed after adequate washout (4 weeks or 5 half-lives, whichever is longer) prior to randomization. * Previous treatment with any cell depleting therapies, including investigational agents (eg, CAMPATH, anti-CD4, anti-CD5, anti-CD3, anti-CD19 and anti-CD20) within 6 months of screening. * Treatment with intravenous gamma globulin, plasmapheresis or Prosorba® column within 2 weeks prior to randomization. * Intra-articular or parenteral corticosteroids are not allowed within 2 weeks prior to randomization.