Vitamin D and its analogs are currently widely used for the treatment of psoriasis. The study drug (CTA018) is a novel analog of vitamin D, and this Phase 2 study will investigate the efficacy and safety of CTA018 in the treatment of psoriasis. Patients with chronic plaque psoriasis will receive one of three doses of CTA018 cream or vehicle (no study drug) daily for 12 weeks.

Inclusion Criteria:

• clinical diagnosis of chronic plaque psoriasis for 6 months to a max 15% body surface area excluding face, scalp, groin, axillae, palms, soles of feet
• at least two evaluable plaques with CPSS >/= 6
• baseline PSGA >/= 2
• women of childbearing potential msut agree to use an effective form of contraception

Exclusion Criteria:

• cannot have guttate, pustular, erythrodermic or other non-plaque forms of psoriasis
• cannot have concomitant serious illness/condition that may interfere with participation in the study
• cannot have used topical therapy within 2 weeks prior to baseline visit
• cannot have used photo-therapy or systemic psoriasis therapy within 4 weeks prior to baseline visit
• cannot have had prolonged exposure to natural or artificial UV radiation within 4 weeks of baseline visit or intend to have exposure during the study
• cannot have used systemic immunomodulatory therapy within 12 weeks prior to baseline visit
• cannot have a history of hypercalcemia or kidney stones
• cannot be unable or unwilling to discontinue calcium and/or vitamin D supplementation during the study
• cannot be pregnant or a nursing mother
• cannot be participating in or have participated in an interventional study within 30 days of study start