ACT-128800 in Patients With Moderate to Severe Chronic Plaque Psoriasis

Inclusion Criteria: * Adult males and females aged 18 to 60 years (inclusive) with moderate to severe chronic plaque psoriasis who require systemic treatment. Exclusion Criteria: * Patients with other forms of psoriasis and patients who are currently treated for autoimmune disorders other than psoriasis. * Systemic or topical treatments for psoriasis other than emollients. Ongoing bacterial, viral or fungal infections. History or presence of malignancy. * Additional inclusion and exclusion criteria apply with respect to medical conditions and concomitant treatments which could affect patients' risk from participating in the study.