Efficacy and Safety Study of KN019 in Rheumatoid Arthritis Patients With an Inadequate Response to Methotrexate

Key Inclusion Criteria: * The patient must meet the American College of Rheumatology (ACR) classification criteria for the diagnosis of rheumatoid arthritis (RA) by satisfying at least four of the seven criteria; * Patients must have been taking methotrexate for at least 3 months with at least a weekly dose of 7.5-25 mg, and a stable dose for 28 days prior to treatment (Day 1) * The patient must have active disease at both screening and baseline, as defined by having both: 6 tender/painful joints on motion (out of 68 joints assessed); and; 6 swollen joints (out of 66 joints assessed); CRP ≥ 7 mg/L, or ESR ≥28 mm/h Key Exclusion Criteria: * Pregnant or lactating females. * History of any other autoimmune rheumatic disease. * Patients who have previously received CTLA4-Ig therapy for any reason.