Sorilux

CLINICAL PHARMACOLOGY

Mechanism of Action

Calcipotriene is a synthetic vitamin D3 analog that has a similar receptor binding affinity as natural vitamin D3. However, the exact mechanism of action contributing to the clinical efficacy in the treatment of psoriasis is unknown.

Pharmacodynamics

The pharmacodynamics of SORILUX (calcipotriene foam) Foam are unknown.

Pharmacokinetics

The systemic absorption of calcipotriene in psoriatic subjects was evaluated at steady state following application of SORILUX Foam or calcipotriene ointment. In the SORILUX Foam treatment group, 15 out of 16 subjects showed calcipotriene plasma concentrations below the limit of quantitation (10 pg/mL), while in the calcipotriene ointment treated group, 5 out of 16 subjects had measurable calcipotriene plasma concentrations at various time points. All measurable plasma calcipotriene concentrations were below 25 pg/mL.

The systemic disposition of calcipotriene is expected to be similar to that of the naturally occurring vitamin D. Absorbed calcipotriene is known to be converted to inactive metabolites within 24 hours of application and the metabolism occurs via a similar pathway to the natural hormone.

Clinical Studies

In two multi-center, randomized, double-blind, vehicle-controlled clinical studies a total of 659 subjects with psoriasis were randomized 2:1 to SORILUX (calcipotriene foam) Foam or vehicle; subjects applied the assigned medication twice daily for 8 weeks. Baseline disease severity was graded using a 5-point Investigator Static Global Assessment scale (ISGA), on which subjects scored either "mild" or "moderate" as shown in Table 1.

Table 1: Investigator Static Global Assessment (ISGA) Scale

Disease Severity Grade Definition
clear 0 No evidence of scaling, erythema, or plaque thickness
almost clear 1 Occasional fine scale, faint erythema, and barely perceptible plaque thickness
mild 2 Fine scale with light coloration and mild plaque elevation
moderate 3 Coarse scale with moderate red coloration and moderate plaque thickness
severe 4 Thick tenacious scale with deep coloration and severe plaque thickness

Efficacy evaluation was carried out at Week 8 with treatment success being defined as a score of "clear" (grade 0) or "almost clear" (grade 1) and at least 2 grade improvement from the baseline score. Approximately 30% of enrolled subjects were graded as "mild" on the ISGA scale. The study population ranged in age from 12 to 89 years with 10 subjects less than 18 years of age at baseline. The subjects were 54% male and 88% Caucasian. Table 2 presents the efficacy results for each study.

Table 2: Number and Percent of Subjects Achieving Success at Week 8 in Each Study

  Study 1 Study 2
  SORILUX Foam
N=223
Vehicle Foam
N=113
SORILUX Foam
N=214
Vehicle Foam
N=109
Number (%) of Subjects with Treatment Success 31(14%) 8 (7%) 58 (27%) 17 (16%)

In one study, subjects graded as "mild" at baseline showed a greater response to vehicle than SORILUX (calcipotriene foam) Foam.

Table 3 presents the success rates by disease severity at baseline for each study.

Table 3: Number and Percent of Subjects Achieving Success by Baseline ISGA Score and by Study

  Study 1 Study 2
ISGA scores at baseline SORILUX Foam
(N=223)
Vehicle Foam
(N=113)
SORILUX Foam
(N=214)
Vehicle Foam
(N=109)
mild 2/73 (2.7%) 3/34 (8.8%) 8/56 (14.3%) 4/31 (12.9%)
moderate 29/150 (19.3%) 5/79 (6.3%) 50/158 (31.6%) 13/78 (16.7%)

The contribution to efficacy of individual components of the vehicle has not been established.

Last reviewed on RxList: 11/2/2010
This monograph has been modified to include the generic and brand name in many instances.

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