Efalizumab is a monoclonal anti-CD11a antibody used to treat moderate to severe plaque psoriasis.Humanized IgG1 kappa isotype monoclonal antibody that binds to human CD11a. Efalizumab has a molecular weight of approximately 150 kilodaltons and is produced in a Chinese hamster ovary mammalian cell expression system in a nutrient medium containing the antibiotic gentamicin.Efalizumab binds to CD11a, a subunit of leukocyte function antigen-1 (LFA-1), which is expressed on all leukocytes. As a result efalizumab decreases cell surface expression of CD11a.