Use of a psoriasis plaque test in the development of a gel formulation of calcipotriol and betamethasone dipropionate for scalp psoriasis

BACKGROUND: The efficacy and safety of calcipotriol plus betamethasone dipropionate ointment in the treatment of psoriasis vulgaris has consistently been demonstrated in several clinical trials. For treatment of scalp psoriasis, more convenient formulations are required. Therefore, new lipophilic alcohol-free gel formulations containing calcipotriol (50 µg/g) and betamethasone (0.5 mg/g; as dipropionate) (two-compound gels) for treatment of scalp psoriasis were developed. OBJECTIVE: To identify the optimal gel formulation by evaluating the antipsoriatic effect in a psoriasis plaque test model. METHOD: The use of a psoriasis plaque test enables investigation of the antipsoriatic effect of several formulations and compounds in a limited number of patients, and is a useful method for predicting treatment efficacy in psoriasis vulgaris. Five different gel vehicles were investigated in two plaque test studies. RESULTS AND CONCLUSION: The optimised two-compound gels showed superior antipsoriatic effect over marketed betamethasone dipropionate solution. The results suggest that use of the psoriasis plaque test early in the development process can improve the development of topical formulations for dermatological use and can be a beneficial tool for selecting the most promising formulations for further clinical studies in psoriasis vulgaris.