Study to Assess if ABP 798 is Safe & Effective in Treating Moderate to Severe Rheumatoid Arthritis (RA) Compared to Rituximab

- Men or women ≥ 18 and ≤ 80 years old - Subjects must be diagnosed with rheumatoid arthritis for at least 6 months before baseline - Active RA defined as ≥ 6 swollen joints and ≥ 6 tender joints at screening and baseline and at least one of the following at screening: • erythrocyte sedimentation rate (ESR) ≥ 28 mm/hr • serum C-reactive protein (CRP) > 1.0 mg/dL - Subjects must be taking methotrexate (MTX) for ≥ 12 consecutive weeks and on a stable dose of MTX 7.5 to 25 mg/week for ≥ 8 weeks prior to receiving the investigational product (IP), and be willing to remain on a stable dose throughout the study - Subject has no known history of active tuberculosis

- Class IV RA, Felty's syndrome or history of prosthetic or native joint infection - Major chronic inflammatory disease or connective tissue disease other than RA, with the exception of secondary Sjögren’s syndrome - Use of commercially available or investigational biologic therapies for RA as follows: • anakinra, etanercept within 1 month prior to first dose of IP • infliximab, abatacept, tocilizumab, golimumab, certolizumab within 3 months prior to first dose of IP • other experimental or commercially available biologic therapies for RA within 3 months or 5 half-lives (whichever is longer) prior to first dose of IP - Previous receipt of rituximab or a biosimilar of rituximab Other Inclusion/Exclusion criteria may apply