This is a study of a new oral drug used for the treatment of psoriasis. All subjects will get active medication, there is no placebo arm.

Inclusion Criteria:

• Male or female of non-childbearing potential (at least 2 years post-menopausal or undergone successful surgical sterilization at least 1 year before inclusion)
• Presence of moderate to severe plaque psoriasis with a PASI of at least 5

Exclusion Criteria:

• Pustular, guttate or other non-plaque forms of psoriasis or psoriatic arthritis
• Significant coexisting hepatic, renal, or bone marrow disease, hyperlipidemia, chronic pancreatitis, osteoporosis, or a history indicating adrenal cortex dysfunction or any other serious disease (including cancer and subjects known to be HIV positive)
• History of heart failure, myocardial infarction within the past six months, cardiac arrhythmia, or under treatment for heart disorders
• Clinically significant abnormal ECG-intervals or morphology of the ECG; QT or QTc >470 ms in females or >450 ms in males
• Use of vitamin A (>1000 µg/day), phenytoin, carbamazepine, warfarin, rifampicin, tetracyclines, ketoconazole, itraconazole, astemizole, terfenadine, cisapride, anti-psychotics, anti-depressants, lithium, antimalarials, alpha-blocking drugs, angiotensin-converting enzyme inhibitors, cyclosporin A, glucocorticosteroids and non-steroidal anti-inflammatory drugs, non-potassium-sparing diuretics
• Previous use of any systemic immunomodulatory therapy (biologicals) or psoriasis vaccine
• Use of other systemic therapy for psoriasis (e.g. PUVA, systemic steroids, cyclosporin A, methotrexate, retinoids) within four weeks prior to Visit 2
• Use of UV therapy or excessive UV exposure or topical therapy for psoriasis other than bland emollients within two weeks prior to Visit 2