INTRODUCTION: Psoriatic arthritis (PsA) is a spondyloarthritis that occurs in up 
to 30% of psoriasis patients. Patients with PsA are at risk for decreased 
quality of life due to both joint and skin symptoms, impaired physical function 
and disease progression. Treatments include non-steroidal anti-inflammatory 
drugs, conventional systemic disease-modifying anti-rheumatic drugs (DMARDs) 
such as methotrexate, and biologic agents, including tumor necrosis factor-α 
inhibitors. The most recently introduced treatment option is apremilast, an oral 
phosphodiesterase 4 inhibitor.
METHODS: This review provides an in-depth discussion of apremilast's mechanism 
of action, and evidence of its clinical efficacy and safety from the Psoriatic 
Arthritis Long-term Assessment of Clinical Efficacy (PALACE) phase III pivotal 
clinical trials (PALACE 1, 2, and 3).
RESULTS: These trials demonstrate that apremilast is effective for the treatment 
of active PsA, despite prior conventional DMARDs or biologic treatment. The 
primary efficacy end point, a 20% improvement from baseline in modified American 
College of Rheumatology response criteria at Week 16, was achieved by 
significantly greater proportions of patients treated with apremilast 20 mg 
twice daily (BID) and apremilast 30 mg BID versus placebo in PALACE 1, 2, and 3. 
Improvements in this and other clinical and patient-reported end points, 
including swollen and tender joint counts, Psoriasis Area and Severity Index 
score, physical function, and quality of life, were maintained, extending over 
52 weeks of treatment among patients initially randomized to apremilast. 
Apremilast's safety profile has been acceptable, with diarrhea and nausea being 
the most common adverse events, with no evidence for an increased risk of 
infection or need for laboratory monitoring. The PALACE pivotal data indicate 
that apremilast presents a new option for the treatment of PsA that may be 
appropriate for use early in the treatment ladder. Ongoing PALACE open-label 
extension trials of up to 4 years will characterize the long-term clinical 
effects and safety of apremilast therapy.
FUNDING: Celgene Corporation, Summit, NJ, USA.