The purpose of this trial is to compare the anti-psoriatic effect of a topical combination product containing clobetasol propionate and calcipotriol in an ointment formulation to the single components in the same vehicle using a psoriasis plaque test design.

Inclusion Criteria (in summary):

• Subjects having understood and signed an informed consent form
• Either sex
• Age 18 years or above
• All skin types and any ethnic origin
• Subjects with a diagnosis of psoriasis vulgaris with lesions located on arms, legs or trunk

Exclusion Criteria (in summary):

• Females who are pregnant, or who wish to become pregnant during the study, or who are breast feeding

• Systemic treatment with biological therapies (marketed or not marketed) with a possible effect on psoriasis vulgaris within 4 weeks (etanercept), 2 months (adalimumab, alefacept, infliximab), 4 months (ustekinmab) or 4 weeks/5 half-lives (which-ever is longer) for experimental biological products prior to randomisation

• Systemic treatments with all other therapies than biologicals, with a potential effect on psoriasis vulgaris (e.g., corticosteroids, vitamin D analogues, retinoids, immuno-suppressants) within the 4-week period prior to randomisation

• Subjects using one of the following topical drugs for the treatment of psoriasis within the 4 week period prior to randomisation

  • Potent or very potent (WHO group III-IV) corticosteroids
  • PUVA or Grenz ray therapy

• Subjects using one of the following topical drugs for the treatment of psoriasis within 2 weeks prior to randomisation

  • WHO group I-II corticosteroids
  • Topical retinoids
  • Vitamin D analogues
  • Topical immunomodulators (e.g. macrolides)
  • Anthracen derivatives
  • Tar
  • Salicylic acid
  • UVB therapy

• Subjects who have received treatment with any non-marketed drug substance (i.e., an agent which has not yet been made available for clinical use following registration) within the 4 week period prior to randomisation or longer, if the class of the substance requires a longer washout as defined above (e.g., biological treatments)

• Subjects with current participation in any other interventional clinical, based on interview of the subject

• Subjects with current diagnosis of guttate, erythrodermic, exfoliative or pustular psoriasis

• Subjects with known or suspected hypersensitivity to component(s) of the investigational products

• Subjects with known/suspected disorders of calcium metabolism associated with hypercalcaemia

• Subjects with known severe hepatic and/or severe renal insufficiency

• Subjects with any of the following conditions present on the plaque test areas: viral (e.g. herpes or varicella) lesions of the skin, fungal and bacterial skin infections, parasitic infections and atrophic skin

• Subjects with skin manifestations on the plaque test areas in relation to syphilis or tuberculosis, rosacea, perioral dermatitis, acne vulgaris, atrophic skin, striae atrophicae, fragility of skin veins, ichthyosis, acne rosacea, ulcers and wounds

• Subjects with any concomitant medical or dermatological disorder(s) which might preclude accurate evaluation of the psoriasis