A synthetic vitamin D derivative usually formulated for topical dermatological use, antipsoriatic Calcipotriene (calcipotriol) competes equally with active 1,25-hydroxy-2D3 (the natural form of vitamin D) for 1,25-hydroxy-2D3 receptors in regulating cell proliferation and differentiation. It induces differentiation and suppresses proliferation of keratinocytes, reversing abnormal keratinocyte changes in psoriasis, and leads to normalization of epidermal growth. (NCI04)