Topical PTH (1-34) is a novel, safe and effective treatment for psoriasis: a randomized self-controlled trial and an open trial.

BACKGROUND There continues to be a need to develop new pharmacological approaches for treating the common skin disease psoriasis. Human skin produces parathyroid hormone related peptide. This peptide is a potent inhibitor of epidermal cell growth. OBJECTIVES A programme was initiated to determine whether an agonist of this peptide's receptor, PTH (1-34), could be developed as a drug to treat psoriasis. METHODS PTH (1-34) was formulated in Novasome A cream. Fifteen adult patients with chronic plaque psoriasis who had failed to respond to at least one standard treatment were enrolled in a randomized double-blinded placebo self-controlled trial. The patients topically applied to a 25-cm2 psoriatic lesion 0.1 g of either Novasome A cream or Novasome A cream that contained 20 microg of PTH (1-34) twice a day for 2 months. At the end of the double-blind study, patients were enrolled in an open large area study. Ten patients applied PTH (1-34) (50 microg per 0.1 g) once daily to their psoriatic lesions. The patients were evaluated for their global improvement and calcium metabolism. RESULTS Novasome A cream enhanced the percutaneous absorption of PTH (1-34) in human skin in comparison with formulations in propylene glycol or normal saline. Psoriatic lesions treated with PTH (1-34) showed marked improvement in scaling, erythema and induration. There was a 67.3% improvement in the global severity score for the lesion treated with PTH (1-34) compared with the placebo-treated lesion, which only showed a 17.8% improvement. Ten patients topically applied PTH (1-34) on all of their lesions in a stepwise manner. A Psoriasis Area and Severity Index score analysis of all the patients revealed improvement of 42.6% (P < 0.02). None of the patients experienced hypercalcaemia or hypercalciuria or developed any side-effect to the medication. CONCLUSIONS Patients who were resistant to at least one standard therapy for psoriasis had a remarkable improvement in their psoriasis when they applied PTH (1-34) to their lesion(s). No untoward toxicity was observed in any of the subjects. This pilot study suggests that topical PTH (1-34) is a safe and effective novel therapy for psoriasis.