The purpose of the study is to determine whether, in patients with moderate to severe plaque-type psoriasis, AIN457 administered subcutaneously reduces the severity of psoriasis symptoms and the extent to which the patient's body area is affected by the disease (compared to placebo).

Inclusion Criteria:

• Men or women at least 18 years of age at time of consent

• Chronic plaque-type psoriasis diagnosed for at least 6 months at time of randomization

• At time of randomization, moderate to severe psoriasis as defined by:

  • PASI score of 12 or greater and
  • IGA score of 3 or greater and
  • Body Surface Area (BSA) affected by plaque-type psoriasis of 10 % or greater

• At screening and randomization, chronic plaque-type psoriasis considered inadequately controlled by:

  • topical treatment and/or
  • phototherapy and/or
  • previous systemic therapy

Exclusion Criteria:

• Patients meeting any of the following criteria will be excluded from entry into the study:
• Forms of psoriasis other than chronic plaque-type (e.g., pustular, erythrodermic and guttate psoriasis) at screening or randomization
• Drug-induced psoriasis (i.e. new onset or current exacerbation from beta-blockers, calcium channel inhibitors or lithium) and randomization
• Ongoing use of prohibited psoriasis treatments (e.g., topical or systemic corticosteroids, UV therapy) at randomization. Washout periods detailed in the study protocol have to be adhered to
• Ongoing use of other prohibited treatments at randomization. Washout periods detailed in the study protocol have to be adhered to. All prior concomitant medications must be on a stable dose for at least four weeks before study drug administration
• Known immunosuppression (e.g., AIDS) at screening and / or randomization
• History or evidence of active tuberculosis at screening. All patients will be tested for tuberculosis status using a blood test (QuantiFERON®-TB Gold In-Tube). Patients with evidence of latent tuberculosis may enter the trial after sufficient treatment has been initiated according to local regulations.
• Active systemic infections (other than common cold) during the two weeks before randomization (e.g., hepatitis)
• At screening, history or symptoms of malignancy of any organ system (other than history of basal cell carcinoma and / or up to three squamous cell carcinomas of the skin, if successful treatment has been performed, with no signs of recurrence; actinic keratoses, if present at screening, should be treated according to standard therapy before randomization), treated or untreated, within the past 5 years, regardless of whether there is evidence of local recurrence or metastases
• History of congestive heart failure (NYHA functional classification ≥III) at screening and / or randomization
• History of severe hypersensitivity to any human or humanized biological agents (antibody or soluble receptor) at screening and / or randomization
• Any severe, progressive or uncontrolled medical condition at randomization that in the judgment of the investigator prevents the patient from participating in the study
• Pregnant or nursing (lactating) women