Adalimumab (brand name Humira) is the third TNF antagonist, after infliximab and etanercept, to be approved in the United States. Like infliximab and etanercept, adalimumab binds to TNFα, preventing it from activating TNF receptors; adalimumab was constructed from a fully human monoclonal antibody, while infliximab is a mouse-human chimeric antibody and etanercept is a TNF receptor-IgG fusion protein. TNFα inactivation has proven to be important in downregulating the inflammatory reactions associated with autoimmune diseases. As of February 2007, adalimumab has been approved for the treatment of rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis and Crohn's disease, and was approved by the FDA for the treatment of moderate to severe chronic psoriasis. Humira is marketed in both preloaded 0.8 ml syringes and also in preloaded pen devices, both injected subcutaneously, typically by the patient at home. It cannot be administered orally, because the digestive system would destroy the drug.