Clobetasol propionate shampoo 0.05%: a new option to treat patients with moderate to severe scalp psoriasis

Journal of Drugs in Dermatology, July-August, 2004 by Michael Jarratt, Debra Breneman, Alice B. Gottlieb, Yves Poulin, Yin Liu, Valerie Foley

Excluded from the study were women who were pregnant, nursing or planning a pregnancy, or subjects with a known allergy to one of the components of the test products. Further exclusion criteria included scalp psoriasis that needed systemic treatment or which required the use of other concomitant therapies for psoriasis during the study. Subjects were also to avoid excessive UV exposure and were to respect specified wash-out periods for systemic anti-psoriatic medications.

Treatments

Subjects were assigned following a computer generated randomization list to either clobetasol propionate shampoo, 0.05%, or clobetasol propionate shampoo vehicle in a 2:1 ratio. All individuals were to apply the study drug once a day and to leave it on the dry scalp for 15 minutes before lathering and rinsing. Subjects were asked to use the study drug over a period of 4 weeks and then to avoid during a 2-week follow-up the study medication and all psoriasis treatments previously excluded. The use of topical emollients, coal tars, vitamin D derivatives, tazarotene, or salicylic acid to treat body psoriasis during the course of the study was allowed.

Efficacy and safety assessments

The primary efficacy variable was the success rate after 4 weeks of treatment, defined as the proportion of subjects with a global severity score (GSS) of 0 (clear) or 1 (minimal). Failure was defined as a GSS of 2 (mild), 3 (moderate), 4 (severe), or 5 (very severe). Subjects were required to have moderate to severe scalp psoriasis (defined as a GSS of at least 3 on a scale of 0 to 5 points) at study entry. Secondary efficacy parameters were: GSS; total severity score (TSS; from 0: none to 3: severe), which was the sum of erythema, plaque thickening, and scaling scores; individual disease scores (rated from 0: none to 3: severe) of erythema, plaque thickening, scaling, pruritus, and percentage scalp surface area of involvement; global assessment of improvement by the investigator; and global assessment of improvement by the subject.

Safety was assessed through adverse events (AEs), including local side effects.

Statistical Methods

The sample size of 120 (80 for clobetasol propionate shampoo 0.05%, and 40 for clobetasol propionate shampoo vehicle) was determined to collect sufficient safety data and to detect a significant difference in success rates of 60% vs. 20% with 90% power at the 0.05 significance level for the 2-tailed alternative. Adjusting for a 10% dropout rate, 132 subjects were planned to be enrolled.

The intent-to-treat (ITT) population was primary for the efficacy analysis. This population consisted of all subjects randomized and who had the study drug dispensed. Success rate was analyzed using the Cochran-Mantel-Haenszel (CMH) test, stratified by center. Additional analyses for the success rate at other time points and for the secondary efficacy variables were conducted as supportive. The CMH test stratified by center, using the RIDIT transformation, was used for the global severity score (full scale), plaque elevation, erythema, scaling, pruritus, and global assessments of improvement by the Investigator and by the subject. Both the per protocol (PP) population with observed cases, and the ITT population, with missing data imputed using the last observation carried forward (LOCF) were analyzed for efficacy.