Patients with plaque psoriasis will be enrolled. They will be dosed with repeated intravenous doses of BTT-1023 or placebo. During the trial, the safety of the treatments and the pharmacokinetics of BTT-1023 will be assessed. The patient allocation to treatment groups will occur at random, and the actual treatment will not be revealed to the investigator or to the patient during the trial.

Inclusion Criteria:

• Plaque psoriasis affecting at least 8% of the body surface area and scoring 8 or higher in the psoriasis area and severity index

Exclusion Criteria:

• Seropositive for infection with human immunodeficiency virus, hepatitis B virus, or hepatitis C virus; Tuberculosis; Acute systemic infection;
• Treatment with a monoclonal antibody therapy within 12 weeks prior to study entry;
• An absolute indication for a known effective treatment