Global sales of topical products for the treatment of psoriasis were approximately $532 million for the twelve month period ended October 2005, with almost 70% of these sales coming from existing topical vitaminD-based products according to IMS Health. Other available topical agents include corticosteroids, keratolytics, anthralin, coal tar and retinoids. While each of these existing topical treatments has been shown to produce some clinical benefit, each has also been associated with undesirable side effects, including skin irritation, odor and staining of the skin. Physicians often switch or rotate therapies to try to avoid such problems or improve efficacy. Topical products are mainly used for mild to moderate psoriasis; recently, new systemic products have been approved for the treatment of moderate to severe psoriasis. As use of these much more expensive therapies increases, the overall value of the total market for psoriasis products is projected to grow significantly.

Corticosteroids and calcitriol analogues, either alone or in combination, are the most popular of topical treatments. Steroids can quickly clear lesions, but they typically do not produce long remissions and repeated use can be associated with a thinning of the outer layers of the skin and other undesired skin changes. All currently marketed calcitriol based products have reported cases of excessive blood levels of calcium, which can result in kidney and other potentially serious problems. These existing products are also reported to exhibit frequent skin irritation that may reduce patient compliance and encourage switching of therapies.