 Inclusion Criteria: - Active, but clinically stable, plaque psoriasis involving greater than or equal to 10 of the body surface area - A minimum PASI score of 10 obtained during the screening period Exclusion Criteria: - Active guttate, erythrodermic, or pustular psoriasis at the time of the screening visit - Evidence of skin conditions at the time of the screening visit e.g., eczema that would interfere with evaluations of the effect of an investigational product on psoriasis 