Study of the Drug Efalizumab (Raptiva), for Adult Patients With Moderate to Severe Plaque Psoriasis

Inclusion Criteria: Signed informed consent * Plaque psoriasis covering \>10% of total BSA * Diagnosis of plaque psoriasis for at least 6 months * PASI score \>=12 (see Appendix A) or Linear PASI score of \>= 8.0 at screening (see Appendix B) * In the opinion of the investigator, candidate for systemic therapy for psoriasis: * Who has not been previously treated (naive to systemic treatment) OR * Who has had prior treatment with systemic therapy for psoriasis (e.g., PUVA, cyclosporine, corticosteroids, methotrexate, oral retinoids, mycophenolate mofetil (MMF), thioguanine, hydroxyurea, sirolimus, azathioprine, 6-MP, etanercept) * Body weight of \<140 kg * 18 to 75 years old. As the risk of Efalizumab in childhood is unknown, those \< 18years will be excluded from the study * For women of childbearing potential or in men whose partners may become pregnant, willingness to use an acceptable method of contraception to prevent pregnancy for the duration of the study (while receiving study medication and 3 months following). Acceptable methods of contraception include use of a condom; abstinence; use by sexual partner of oral implantable or injectable contraceptives, IUD, female condom, diaphragm with spermicide, cervical cap; or a sterile sexual partner * Willingness to hold sun exposure reasonably constant and to avoid use of tanning booths or other UV light sources during the study Exclusion Criteria Subjects who meet any of the following exclusion criteria are ineligible for study entry: * Guttate, erythrodermic, or pustular psoriasis as sole or predominant form of psoriasis * History of severe allergic or anaphylactic reactions to humanized monoclonal antibodies or fusion proteins that contain an Ig Fc region * Clinically significant psoriasis flare during screening or on the first treatment day * Treatment with efalizumab (anti-CD11a) within the last 12 months before enrollment * Pregnancy or lactation. As the risk of Efalizumab in pregnancy is unknown, pregnant women will be excluded from the study * History of or ongoing uncontrolled bacterial, viral, fungal, or atypical mycobacterial infection * History of active tuberculosis (TB) or currently undergoing treatment for TB. PPD testing or chest X-ray is required for high-risk subjects (see Appendix D). Subjects with a positive PPD (not due to BCG vaccination) or chest X-ray will be excluded * History of opportunistic infections (e.g., systemic fungal infections, parasites) * Seropositivity for human immunodeficiency virus (HIV) * Seropositivity for hepatitis B or C virus * Hepatic enzymes \>3 times the upper limits of normal (ULN) * Diagnosis of hepatic cirrhosis, regardless of cause or severity * WBC count \<4000μL or \>14,000/μL * Serum creatinine \>2 times the ULN * Hospital admission for cardiac disease, stroke, or pulmonary disease within the last year * Presence of malignancy within the past 5 years, including lymphoproliferative disorders. Subjects with a history of fully resolved basal cell or squamous cell skin cancer may be enrolled * History of substance abuse within the last 5 years * Any medical condition that, in the judgment of the investigator, would jeopardize the subject's safety following exposure to study drug Note: Certain medications and vaccines may not be used for specified periods of time prior to enrollment or at any time during the treatment period.