A Study to Assess the Efficacy and Safety of Alefacept in Psoriasis Patients for Whom Conventional Treatment is Ineffective or Inappropriate

Inclusion Criteria: * Diagnosis of Chronic Plaque Psoriasis involving ≥ 10% body surface area * Treatment history for Psoriasis in which 3 or more conventional anti-psoriatic therapies are inappropriate or ineffective * CD4+ T lymphocyte counts at or above the lower limit of normal Exclusion Criteria: * Clinically significant abnormal hematology values or blood chemistry values * AST or ALT ≥ 3x the upper limit of normal * Other types of Psoriasis * Serious infection within the 3 months prior to the first dose of study drug * History of drug or alcohol abuse within the past 2 years * Antibody positive for HIV * History of malignancy * History of any clinically significant cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, and/or other major disease * Exposure to psoriasis-modifying phototherapy or high-potency topical corticosteroid therapy within 2 weeks prior to the first dose of study drug * Exposure to systemic anti-psoriatic therapy , topical immunomodulators or topical CNIs within 4 weeks prior to the first dose of study drug * Current treatment with any therapy for tuberculosis * Previous exposure to Alefacept * Nursing mothers, pregnant women, and women planning to become pregnant during the study