CLINICAL PHARMACOLOGY
Mechanism of Action
Corticosteroids play a role in cellular signaling, immune function, inflammation, and protein regulation; however, the precise mechanism of action in corticosteroid-responsive dermatoses is unknown.
The contribution to efficacy by individual components of the vehicle has not been established.
Pharmacodynamics
In a trial evaluating the potential for HPA axis suppression using the cosyntropin stimulation test, OLUX-E Foam demonstrated reversible adrenal suppression after 2 weeks of twice-daily use in subjects with atopic dermatitis of at least 30% body surface area (BSA). The proportion of subjects aged 12 years and older demonstrating HPA axis suppression was 16.2% (6 out of 37). In this trial HPA axis suppression was defined as serum cortisol level ≤18 mcg/dL 30 minutes post cosyntropin stimulation. The laboratory suppression was transient; in all subjects serum cortisol levels returned to normal when tested 4 weeks post treatment [see Warnings and Precautions Use in Specific Populations].
Pharmacokinetics
Topical corticosteroids can be absorbed from intact healthy skin. The extent of percutaneous absorption of topical corticosteroids is determined by many factors, including the product formulation and the integrity of the epidermal barrier. Occlusion, inflammation, and/or other disease processes in the skin may increase percutaneous absorption. The use of pharmacodynamic endpoints for assessing the systemic exposure of topical corticosteroids may be necessary due to the fact that circulating levels are often below the level of detection. Once absorbed through the skin, topical corticosteroids are metabolized primarily in the liver and are then excreted by the kidneys. Some corticosteroids and their metabolites are also excreted in the bile.
Following twice daily application of OLUX-E Foam for 1 week to 32 adult patients with mild to moderate plaque-type psoriasis, mean peak plasma concentrations (±SD) of 59 ± 36 pg/mL of clobetasol were observed at around 5 hours post dose on Day 8.
NONCLINICAL TOXICOLOGY
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long-term animal studies have not been performed to evaluate the carcinogenic potential of OLUX-E Foam or clobetasol propionate.
In a 90-day repeat-dose toxicity study in rats, topical administration of OLUX-E Foam at dose concentrations from 0.001% to 0.1% or from 0.03 to 0.3 mg/kg/day of clobetasol propionate resulted in a toxicity profile consistent with long term exposure to corticosteroids including adrenal atrophy, histopathological changes in several organs systems indicative of severe immune suppression and opportunistic fungal and bacterial infections. A no observable adverse effect level (NOAEL) could not be determined in this study. Although the clinical relevance of the findings in animals to humans is not clear, sustained glucocorticoid-related immune suppression may increase the risk of infection and possibly the risk for carcinogenesis.
Topical doses of 0% (foam vehicle), 0.001%, 0.01%, and 0.05% clobetasol propionate foam were evaluated in a 52-week dermal photocarcinogenicity study (40 weeks of treatment followed by 12 weeks of observation) conducted in hairless albino mice with concurrent exposure to low-level ultraviolet radiation. Topical treatment with increasing concentrations of clobetasol propionate foam did not have an adverse effect in this study. The results of this study suggest that topical treatment with OLUX-E Foam would not enhance photocarcinogenesis.
Clobetasol propionate was non-mutagenic in 4 different test systems: the Ames test, the mouse lymphoma test, the Saccharomyces cerevisiae gene conversion assay, and the E. coli B WP2 fluctuation test. In the in vivo mouse micronucleus test, a positive finding was observed at 24 hours, but not at 48 hours, following oral administration at a dose of 2,000 mg/kg.
Studies in the rat following subcutaneous administration of clobetasol propionate at dosage levels up to 0.05 mg/kg per day revealed that the females exhibited an increase in the number of resorbed embryos and a decrease in the number of living fetuses at the highest dose.
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