Inclusion Criteria:

• Understand and voluntarily sign an informed consent form
• ≥18 years of age at the time of signing the informed consent form
• Able to adhere to the study visit schedule and other protocol requirements.

• Diagnosis of chronic, stable plaque psoriasis at least 6 months prior to screening as defined by:

  1. PASI score ≥ 12
  2. BSA ≥ 10%
• Candidate for photo/systemic therapy
• In good health as judged by the investigator, based on medical history, physical examination, 12-lead ECG, serum chemistry, hematology, immunology, and urinalysis
• Meet all laboratory criteria as defined per
• Females of childbearing potential (FCBP) must have a negative urine pregnancy test at screening (Visit 1). In addition, sexually active FCBP must agree to use TWO of the following adequate forms of contraception methods. A FCBP must agree to have pregnancy tests every 4 weeks while on study medication
• Males (including those who have had a vasectomy) must agree to use barrier contraception (latex condoms) when engaging in reproductive sexual activity with FCBP while on study medication and for 84 days after taking the last dose of study medication

Exclusion Criteria:

• History of clinically significant disease(as determined by the investigator)
• Pregnant or breastfeeding
• History of active mycobacterial infection within 3 years
• History of Human Immunodeficiency Virus (HIV) infection
• Congenital and acquired immunodeficiencies
• Hepatitis B surface antigen positive or Hepatitis B core antibody positive at screening
• Antibodies to Hepatitis C at screening
• Malignancy or history of malignancy except for treated [i.e., cured] basal-cell skin carcinomas
• Any condition, including the presence of laboratory abnormalities, that places the subject at unacceptable risk if he/she were to participate in the study or confounds the ability to interpret data from the study
• Psoriasis flare within 4 weeks of screening
• Topical therapy within 2 weeks of randomization
• Systemic therapy for psoriasis within 4 weeks of randomization
• Use of phototherapy within 4 weeks of randomization (i.e., UVB, PUVA)
• Adalimumab, etanercept, efalizumab or infliximab within 12 weeks of randomization
• Alefacept within 24 weeks of randomization
• Investigational drug within 4 weeks of randomization, or 5 pharmacokinetic/pharmacodynamic half lives, if known (whichever is longer)
• Prolonged sun exposure or use of tanning booths or other ultraviolet light sources