A randomised trial evaluating the effects of the TRPV1 antagonist SB705498 on pruritus induced by histamine, and cowhage challenge in healthy volunteers.

BACKGROUND: Transient receptor potential vanilloid type 1 (TRPV1) is a non-selective cation channel widely expressed in skin tissues, and peripheral sensory nerve fibres. Activation of TRPV1 releases neuropeptides; the resulting neurogenic inflammation is believed to contribute to the development of pruritus. A TRPV1 antagonist has the potential to perform as an anti-pruritic agent. SB705498 is a TRPV1 antagonist that has demonstrated in vitro activity against cloned TRPV1 human receptors and when orally administered has demonstrated pharmacodynamic activity in animal models and clinical studies. OBJECTIVES: To select a topical dose of SB705498 using the TRPV1 agonist capsaicin; to confirm engagement of the TRPV1 antagonistic action of SB705498 and assess whether the dose selected has an effect on itch induced by two challenge agents. METHODS: A clinical study was conducted in 16 healthy volunteers to assess the effects of 3 doses of SB705498 on skin flare induced by capsaicin. Subjects with a robust capsaicin response were chosen to determine if the selected topical formulation of SB705498 had an effect on challenge agent induced itch. RESULTS: Following capsaicin challenge the greatest average reduction in area of flare was seen for the 3% formulation. This dose was selected for further investigation. Itch intensity induced by two challenge agents (cowhage and histamine) was assessed on the Computerised Visual Analogue Scale. The difference in average itch intensity (Weighted Mean Over 15 Mins) between the 3% dose of SB705498 and placebo for the cowhage challenge was -0.64, whilst the histamine challenge showed on average a -4.65 point change. CONCLUSIONS: The 3% topical formulation of SB705498 cream was clinically well tolerated and had target specific pharmacodynamic activity. However there were no clinically significant differences on pruritus induced by either challenge agent in comparison to placebo. SB705498 is unlikely to be of symptomatic benefit for histaminergic or non-histaminergic induced itch. TRIAL REGISTRATION: ClinicalTrials.gov NCT01673529.

Efficacy and safety of calcipotriene 0.005% foam for the treatment of plaque-type psoriasis: results of two multicenter, randomized, double-blind, vehicle-controlled, phase III clinical trials.

BACKGROUND: Topical calcipotriene is frequently prescribed for the treatment of plaque-type psoriasis. Calcipotriene is currently available in the US as an ointment, a solution, a cream, and in a fixed-dose combination ointment with betamethasone dipropionate. Calcipotriene 0.005% has recently been formulated as a foam using a novel aqueous-based formulation to provide a new topical treatment option for patients with psoriasis. OBJECTIVE: The objective of this study was to evaluate the efficacy and safety of topical calcipotriene 0.005% foam for the treatment of mild to moderate plaque-type psoriasis. DESIGN: Two identical, randomized, double-blind, vehicle-controlled, 8-week phase III clinical trials. INTERVENTION: Subjects with plaque-type psoriasis affecting 2-20% of the body surface area, with an identifiable target lesion affecting the trunk or extremities, were randomized in a 2:1 ratio to calcipotriene foam (n = 437) or vehicle foam (n = 222). Study medication was applied twice daily for 8 weeks. OUTCOME MEASURES: Treatment success was defined as a score of 0 or 1 (clear or almost clear) on the Investigator's Static Global Assessment (ISGA) psoriasis rating scale and a minimum improvement of ISGA score of at least 2 grades from baseline. Predefined target lesions were assessed for erythema, scaling, and plaque thickness. Primary endpoint was the proportion of subjects in each treatment group who achieved treatment success after 8 weeks, analyzed on an intent-to-treat (ITT) basis. In the primary endpoint analysis, subjects missing 8-week outcomes data were classified as treatment failures regardless of their outcomes at earlier evaluations. As part of the sensitivity analysis, a last-observation-carried-forward (LOCF) approach to impute missing 8-week efficacy outcomes also examined treatment. Secondary endpoints included treatment success as a function of baseline ISGA score (mild or moderate), ISGA score of 0 or 1 (clear or almost clear), and effects of treatment on target lesion. Adverse events (AEs) were recorded throughout the study. RESULTS: In the ITT population of Study 1, treatment success after 8 weeks was achieved by 14% of subjects in the calcipotriene foam group versus 7% of subjects in the vehicle foam group (p = 0.058). In the LOCF analysis, treatment success was achieved by more subjects with calcipotriene foam than with vehicle foam (15% vs 7%; p = 0.034). In Study 2, treatment success was achieved by more subjects in the calcipotriene foam group for the primary endpoint (27% vs 16%; p = 0.016) and the LOCF analysis (28% vs 16%; p = 0.010). Subjects in the calcipotriene foam group exhibited better response rates than did the vehicle foam group for most of the secondary outcomes. Calcipotriene foam was safe with an overall incidence of AEs similar to those experienced in the vehicle foam group. Application-site reactions were noted in approximately 1-2% of subjects in each group. No AE was reported in more than 2% of subjects in the calcipotriene foam group. Treatment was discontinued because of AEs in approximately 2% of subjects in both groups. CONCLUSIONS: In two identically designed, phase III clinical trials, calcipotriene 0.005% foam was safe and effective for the treatment of mild to moderate plaque-type psoriasis for up to 8 weeks. CLINICAL TRIAL REGISTRATION: Registered at clinicaltrials.gov: NCT00688519 and NCT00689481.