The aim of the exploratory study is to compare dose related effects of LAS41004 formulations in a non-occlusive PPT.

Going for a non-occlusive application design will allow to draw practical conclusions as being similar to a real treatment situation (compared with a occluded design to maximise effects)

Inclusion Criteria:

• 18 to 75 years of age

• Caucasian men and women

• Suffering from mild to moderate plaque psoriasis of at least 6 months duration that is amenable to local therapy

• With at least one stable psoriatic plaque in an area sufficient for product application meeting the following criteria:

  1. located at trunk and/or extremities (plaques located on the head, palms, or sole of feet, intertriginous or genitoanal areas are not suitable)
  2. Where more than one plaque is to be used, plaques that are comparable, with at least "2" in each score for scaling, erythema and induration.
  3. No more than 3 points difference in total score (sum of scores for scaling, erythema and induration)
  4. Negative urine pregnancy test (in female patients of child bearing potential)

• In the case of women of childbearing potential, using reliable methods of contraception which result in a low failure rate i.e. less than 1% per year (eg contraceptive implants or injectables, combined oral contraceptives, some intrauterine devices, sexual abstinence or vasectomized partner)

Exclusion Criteria:

• Patients who need systemic treatment for their psoriasis
• Severe forms of psoriasis or forms of psoriasis other than chronic plaque psoriasis, including:
• guttate
• erythroderma
• exfoliative or
• pustular psoriasis
• psoriatic arthritis
• Changes in the expression of psoriasis within the last 6 weeks prior screening
• Intensive UV light exposure within two weeks before the beginning of the test as well as during the study and four weeks after the end of the study at the test area
• Systemic treatment (see table below):

Corticosteroids, antibiotics 4 weeks prior to study day 1 and during conduct of study Retinoids Ciclosporin Methotrexate Fumaric acid esters 3 months prior to study day 1 and during conduct of study Anti-inflammatory substances, NSAIDs 2 weeks prior to study day 1 and during conduct of study Biologics 6 months prior to study day 1 and during conduct of study Planned initiation of, or changes to concomitant medication that could affect Psoriasis (e.g. beta blockers, anti-malaria drugs, lithium) 8 weeks before study start and during study

• Topical treatment of all other body regions with corticosteroids or immunosuppressants where more than 20 % of the body surface area is treated
• Treatment with any non-marketed drug substance within 4 weeks prior to study day 1
• Topical treatment of the test area without adequate time for washout
• Diseases:

Skin infections caused by bacteria, viruses or fungi, including but not limited to tuberculosis, syphilis or varicella zoster infection Parasitic infections Rosacea, perioral dermatitis in test area Moderate or severe illness within the last two weeks before first exposure Other known infectious diseases (e.g. hepatitis or AIDS) Other skin diseases that may confound the evaluation of psoriasis

• Known hypersensitivity to any ingredients of the study drugs,
• Known calcium metabolism disorders
• History of malignancy of any organ system
• Severe impairment of liver or kidney function
• Pregnancy or lactation
• Participation in a clinical trial within the last 30 days prior to the start of this study