Inclusion Criteria:

• Subject has a clinical diagnosis of psoriasis for at least 6 months prior to the Screening, as determined by subject interview of his/her medical history and confirmation of diagnosis through physical examination by the investigator
• Subject must have stable plaque psoriasis for at least 2 months prior to the Screening, as determined by subject interview of his/her medical history
• Subject has moderate to severely active plaque psoriasis at Baseline defined as: BSA (Body Surface Area) > 10% and a Psoriasis Area and Severity Index (PASI) > 12
• Subject has active psoriasis despite treatment with topical agents
• Subject has failed to respond to, is intolerant to or unable to access phototherapy

• Subject has failed to respond to, is intolerant to or has contraindication for at least two of the following therapies:

  • CyA (Cyclosporine A)
  • MTX (Methotrexate)
  • Oral retinoid

• If female, subject is either not of childbearing potential, defined as postmenopausal for at least 1 year or surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy), or is of childbearing potential and practicing one of the following methods of birth control:

  • Condoms, sponge, foams, jellies, diaphragm or intrauterine device (IUD)
  • Contraceptives (oral or parenteral) for three months (90 days) prior to study drug administration
  • A vasectomized partner
  • Total abstinence from sexual intercourse
• If female and of childbearing potential, the result of a serum pregnancy test performed at Screening is negative
• Able and willing to self-administer sc injections or has available qualified person(s) to administer sc injections
• Able and willing to give written informed consent and comply with the requirements of the study protocol

Exclusion Criteria:

• Subject has other active skin diseases or skin infections (bacterial, fungal, or viral) that may interfere with the evaluation of psoriasis or compromise the subject's safety
• Subject has erythrodermic psoriasis, generalized or localized pustular psoriasis, medication-induced or medication-exacerbated psoriasis, or new onset guttate psoriasis as the primary morphology of their psoriasis
• Subject has a history of an allergic reaction or significant sensitivity to constituents of adalimumab
• Investigational agents not mentioned must be discontinued at least 30 days or 5 half-lives prior to the Baseline visit (whichever is longer)

• Topical therapies:

  • Subject started receiving a new topical therapy within the last four weeks prior to the Baseline visit for areas other than the palms, soles of feet, axilla and groin.
  • Dose(s) and regimen(s) of topical therapy(ies) that the subject is receiving at the Baseline visit, for areas other than the palms, soles of feet, axilla and groin, was (were) increased during the four weeks that preceded the Baseline visit.
  • Subject is likely to require the initiation of a new topical therapy for the treatment of psoriasis such as corticosteroids, vitamin D analogs, or retinoids during the first 16 weeks that will follow the Baseline visit. (During the first 16 weeks that will follow the Baseline visit, initiation of topical therapies are allowed for the palms, soles of feet, axilla and groin area only).

• Oral or injectable corticosteroids therapies:

  • Subject started receiving oral or injectable doses of corticosteroids within the last four weeks prior to the Baseline visit.
  • Dose(s) and regimen(s) of corticosteroids therapy(ies) that the subject is receiving at the Baseline visit, was (were) increased during the four weeks that preceded the Baseline visit.
  • Subject is likely to require the initiation of oral or injectable dose of corticosteroids therapies for the treatment of psoriasis during the first 16 weeks that will follow the Baseline visit.

• Phototherapies

  • Subject started being treated with UVB phototherapy, within the last four weeks prior to the Baseline visit.
  • Regimen(s) of concomitant UVB phototherapy that the subject is receiving at the Baseline visit was (were) increased during the four weeks that preceded the Baseline visit.
  • Subject is likely to require the initiation of UVB therapy during the first 16 weeks that will follow the Baseline visit.
  • Subject was treated with psoralen UVA (PUVA) phototherapy within the last four weeks prior to the Baseline visit.
  • Subject is likely to require PUVA phototherapy during the course of the study.
  • Subject cannot avoid excessive sun exposure or the use of tanning booths for at least 2 weeks prior to Baseline and during the first 16 weeks that will follow the Baseline visit.

• Systemic Therapies:

  • Subject has been initiated on a new systemic agent for the treatment of psoriasis within the last four weeks prior to the Baseline visit.
  • Dose(s) and regimen(s) of systemic therapy(ies) that the subject is receiving at the Baseline visit, was (were) increased during the four weeks that preceded the Baseline visit.
  • Subject is likely to require the initiation of systemic therapy, other than adalimumab, for the treatment of psoriasis during the first 16 weeks that will follow the Baseline visit.
  • Subject has been treated with systemic calcineurin inhibitors (cyclosporin, FK506 and others) within the last four weeks prior to the Baseline visit.
  • Subject is likely to receive systemic calcineurin inhibitors during the course of the study.
  • Subject has received Anakinra/Kineret within the last 2 weeks prior to the Baseline visit and is likely to receive Anakinra/Kineret during the course of the study.

• Subject cannot discontinue the following systemic psoriasis therapies:

  • Alefacept must be discontinued at least 12 weeks prior to the Baseline visit.
  • Efalizumab must be discontinued at least 6 weeks prior to the Baseline visit.
  • Infliximab must be discontinued at least 8 weeks prior to the Baseline visit.
  • Etanercept must be discontinued at least 3 weeks prior to the Baseline visit.

• Subject has a history of cancer or lymphoproliferative disease other than:

  • Successfully and completely treated Cervical dysplasia, with no recurrence within the last five years.
• Has a history of uncontrolled diabetes, unstable ischemic heart disease, congestive heart failure, New York Heart Association (NYHA) III, IV, recent stroke (within three months), chronic leg ulcer and any other condition (e.g., indwelling urinary catheter) which, in the opinion of the Investigator, would put the subject at risk by participation in the protocol or who would make the subject unsuitable for the study.
• Positive serology for hepatitis B indicating acute or chronic infection.
• Currently taking or likely to begin anti-retroviral therapy at any time during the course of the study.
• Subject is known to have immune deficiency, history of human immunodeficiency virus (HIV) or is immunocompromised.
• Persistent or recurrent or severe infections requiring hospitalization or treatment with intra-venous (IV) antibiotics within 30 days, or oral antibiotics within 14 days, prior to Baseline.
• Female subjects who are pregnant or breastfeeding.
• Has a history of clinically significant drug or alcohol abuse in the last year.
• Previous diagnosis or signs of central nervous system demyelinating diseases (e.g., optic neuritis, visual disturbance, gait disorder/ataxia, facial paresis, apraxia).
• History of active tuberculosis (TB), history of histoplasmosis or listeriosis.
• Has latent TB (positive purified protein derivative (PPD) skin test, two-step PPD when applicable, and chest X-ray indicative of TB) or has other risk factors for the activation of latent TB, e.g. previous exposure to TB, and has not initiated TB prophylaxis prior to the first adalimumab treatment. In either case, the Abbott Medical Advisor must be contacted before initiating the study treatment.
• Subjects will be excluded if the CXR is found to have changes suggestive of old healed tuberculous lesion (e.g. calcified nodule, fibrotic scar, apical or basilar pleural thickening etc.).