title: Supersaturation of Calcipotriene and Betamethasone Dipropionate in a Novel Aerosol Foam Formulation for Topical Treatment of Psoriasis Provides Enhanced Bioavailability of the Active Ingredients.
abstract: BACKGROUND
  Previous studies have demonstrated the superior efficacy of a novel aerosol foam formulation of fixed combination calcipotriene 0.005% (Cal) and betamethasone dipropionate 0.064% (BD), compared with the ointment formulation. The aim of this study is to ascertain whether enhanced bioavailability of the active ingredients due to supersaturation and/or occlusive properties can explain the observed greater clinical efficacy.
  
  
  METHODS
  Solubility and evaporation experiments were conducted to examine the abilities of Cal/BD aerosol foam ingredients to create a supersaturated environment. Optical microscopy, Raman imaging and X-ray powder diffraction were used to examine the physical state of Cal and BD in the formulations after application, and determine whether a supersaturated state remained stable for clinically relevant time periods. In vitro skin penetration and ex vivo biomarker assays were conducted to compare the skin penetration and bioavailability of Cal and BD from the aerosol foam and ointment formulations, respectively. Occlusive properties were examined via transepidermal water loss.
  
  
  RESULTS
  Solubility studies showed that Cal and BD solubility increased with increasing dimethyl ether (DME) content. Both active ingredients are completely dissolved in the final aerosol foam formulation. DME rapidly evaporates after spraying, and the amount was reduced to 0.5% of the initial amount after 2 min. This led to the formation of a supersaturated environment, where Cal and BD crystals were absent for at least 26 h after application. Cal/BD aerosol foam had significantly greater in vitro skin penetration and had increased bioavailability compared with Cal/BD ointment. Both formulations effectively occluded the skin.
  
  
  CONCLUSIONS
  A stable supersaturated solution of Cal/BD in the aerosol foam leads to increased bioavailability and explains the improved clinical effect when compared to the Cal/BD ointment.
  
  
  BACKGROUND
  The studies included in the paper are all conducted by LEO Pharma A/S or CROs on behalf of LEO Pharma A/S.
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: Marianne
authors.initials: M
authors.lastname: Lind
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: Kim Troensegaard
authors.initials: KT
authors.lastname: Nielsen
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: Line Hollesen
authors.initials: LH
authors.lastname: Schefe
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark. kasper.noerremark@leo-pharma.com.
authors.forename: Kasper
authors.initials: K
authors.lastname: Nørremark
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: André Huss
authors.initials: AH
authors.lastname: Eriksson
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: Hanne
authors.initials: H
authors.lastname: Norsgaard
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: Brian Thoning
authors.initials: BT
authors.lastname: Pedersen
authors.affiliation: LEO Pharma A/S, Ballerup, Denmark.
authors.forename: Karsten
authors.initials: K
authors.lastname: Petersson
keywords: Aerosol foam; Betamethasone dipropionate; Calcipotriene; Cutaneous foam; Efficacy; Psoriasis; Raman imaging; Skin penetration; Supersaturation; Topical treatments