Key

Inclusion Criteria:

- Meeting classification criteria for psoriatic arthritis for a duration of disease of
at least 3 months

- Prior failure (inefficacy or intolerance) of therapy with disease-modifying
antirheumatic drugs; if patient had prior failure of methotrexate, he or she must
have been taking at least 15 mg per week for at least 2 months

- If recent failure(inefficacy or intolerance) of a tumor necrosis factor α-blockade
compound, participant must be washed out prior to first dose: 56 days for infliximab
and 28 days for etanercept and adalimumab

- Disease activity as defined by a tender joint count of ≥3, swollen joint count of ≥3,
and clinically detectable synovitis at screening and Day 01 (prior to infusion)

- Active psoriasis with a qualifying target lesion ≥2 cm in diameter

- Able to undergo magnetic resonance imaging

- Use of appropriate birth control by women of child bearing potential (WOCBP)

Key Exclusion Criteria:

- WOCBP who are unwilling or unable to use an acceptable method to avoid pregnancy for
the entire study period and for up to 10 weeks after the last dose of investigational
product

- Women who are pregnant or breastfeeding or who plan to become pregnant or to start
breastfeeding during the duration of the study

- Women with a positive pregnancy test on enrollment or prior to investigational
product administration.

- Participants scheduled for or anticipating joint replacement surgery.

- Those with a recent history of clinically significant drug or alcohol abuse

- Concomitant illness that in the investigator's opinion is likely to require systemic
glucocorticosteroid therapy during the study (for example: moderate to severe asthma)

- Current symptoms of severe, progressive, or uncontrolled renal, hepatic, hematologic,
pulmonary, cardiac, neurologic, ophthalmologic, or cerebral disease.

- Unwillingness or inability to undergo screening based on current local or country
guidelines/standards to evaluate the presence of cancer

- Cancer within the last 5 years

- Current malignancy or signs of possible malignancy detected by screening procedures
for which the workup to exclude malignancy has not been completed or malignancy
cannot be excluded

- At risk for or history (within 3 years) of tuberculosis

- Any serious bacterial infection within the last 3 months, not treated and resolved
with antibiotics, or any chronic bacterial infection (such as, but not limited to,
chronic pyelonephritis, osteomyelitis, and bronchiectasis)

- Evidence of active or latent bacterial or viral infection infections at the time of
potential enrollment

- Herpes zoster or cytomegalovirus resolving less than 2 months prior to signing
informed consent

- Receipt of any live vaccines within 3 months of the anticipated first dose of study
medication or anticipation of the need for a live vaccine at any time during and for
3 months after the duration of the study

Long-term period participants: Must have met eligibility criteria for short-term period
and completed short-term (24-week) period of the study