A 34-year-old woman comes to the physician for a follow-up visit. She was diagnosed with rheumatoid arthritis 3 months ago and started on methotrexate therapy. Despite treatment, she continues to have several hours of morning stiffness daily and frequently awakens at night due to joint pain. Physical examination shows swelling and tenderness in the joints of her hands and wrists. Etanercept is subsequently added to her treatment regimen. This medication is best characterized as which of the following?
1) Cell surface receptor antibody
2) Chimeric monoclonal antibody
3) Humanized monoclonal antibody
4) Small-molecule receptor inhibitor
5) E. Soluble receptor decoy protein