This is an exploratory, 4 arm, parallel group, placebo-controlled study comparing three doses of AIN457 to placebo. Subjects with a diagnosis of moderate to severe chronic plaque psoriasis will be randomized to receive either AIN457 at one of the three doses studied or placebo.

Inclusion Criteria:

• Diagnosis of plaque psoriasis for at least 6 months prior to screening. The patients must meet all of the following criterion:

  1. Coverage of the body surface area (BSA) of 10% or more with plaques

  2. A score of 3 or more on the IGA (Investigator Global Assessment) scale

  3. A PASI score of at least 12 at baseline;

     Exclusion Criteria:

• Have forms of psoriasis other than the required "plaque psoriasis"

• Women of childbearing potential

• Recent use of investigational drugs or treatment with other biological therapies (wash-out periods required)

• Previous treatment with this investigational drug

• Subjects with active or history of clinically significant cardiac, kidney or liver abnormalities

Other protocol-defined inclusion/exclusion criteria may have applied.