Topical paricalcitol (19-nor-1alpha,25-dihydroxyvitamin D2) is a novel, safe and effective treatment for plaque psoriasis: a pilot study

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Abstract
Background There continues to be a need to develop new pharmacological approaches for treating psoriasis. Topical active vitamin D compounds have proven to be both safe and effective for treating psoriasis. Paricalcitol (19‐nor‐1α,25‐dihydroxyvitamin D2) is a novel vitamin D analogue which has been developed for the prevention of secondary hyperparathyroidism in patients with chronic renal failure. Objectives To investigate the efficacy and safety of 12 weeks' therapy with a once‐daily application of paricalcitol ointment (15 μg g−1) in comparison with placebo ointment. Methods This pilot double‐blinded self‐controlled study was initiated in 11 patients with moderate plaque psoriasis. To characterize the biological effects further and to evaluate the efficacy of topical paricalcitol treatment in psoriasis, we have analysed immunohistochemically the expression of one of the markers for epidermal differentiation (transglutaminase K) in paricalcitol‐treated skin as compared with placebo treatment. Results Treatment with paricalcitol was superior to placebo treatment beginning at week 1. The global severity score for erythema, plaque elevation and scaling was improved significantly more by paricalcitol ointment than by placebo (P < 0·001). Similar results were obtained for assessments of scaling, erythema and plaque elevation. No symptoms of local skin irritation were noted. Laboratory parameters including serum calcium, phosphorus, parathyroid hormone and urinary calcium/creatinine ratio did not reveal any changes of clinical relevance during treatment. The immunoreactivity of transglutaminase K changed after 12 weeks of paricalcitol treatment almost completely to the pattern characteristic for nonlesional psoriatic skin. Conclusions Once‐daily application of paricalcitol ointment was safe and effective for the treatment of plaque psoriasis.