A Study to Determine the Efficacy and Safety of 122-0551 in Subjects With Plaque Psoriasis

Inclusion Criteria: * Subject has a clinical diagnosis of stable plaque psoriasis * Subject has an ODS score for the Treatment Area of 3 or 4 at study start Exclusion Criteria: * Subject has spontaneously improving or rapidly deteriorating plaque psoriasis. * Subject has guttate, pustular, erythrodermic or other non-plaque forms of psoriasis. * Subject has used any phototherapy, photo-chemotherapy or systemic corticosteroid therapy within 30 days prior to study start * Subject has used any systemic methotrexate, retinoids, cyclosporine or analogous products within 90 days prior to study start * Subject has used any systemic biologic therapy for the treatment of psoriasis within 5 half-lives of the biologic prior to study start * Subject had prolonged exposure to natural or artificial sources of ultraviolet radiation within 30 days prior to study start * Subject has used topical body (excluding the scalp) psoriasis therapy including coal tar, anthralin, steroids, retinoids, vitamin D analogs (e.g., Dovonex®) within 14 days prior to study start * Subject has used emollients/moisturizers on areas to be treated within four hours prior to clinical evaluation at study start * Subject is currently using lithium or Plaquenil (hydroxychloroquine) * Subject is currently using a beta-blocking medication (e.g., propranolol) or ACE (e.g., lisinopril) inhibitor at a dose that has not been stabilized * Subject is pregnant, lactating, or is planning to become pregnant during the study * Subject is currently enrolled in an investigational drug or device study * Subject has used an investigational drug or investigational device treatment within 30 days prior to study start * Subject has been previously enrolled in this study and treated with a test article