Objective. Apremilast, an oral phosphodiesterase 4 inhibitor, downregulates intracellular inflammatory mediator synthesis by elevating cyclic adenosine monophosphate levels. The PALACE 2 trial evaluated apremilast efficacy and safety in patients with active psoriatic arthritis (PsA) despite prior conventional disease-modifying antirheumatic drugs and/or biologic therapy. Methods. Eligible patients were randomized (1: 1: 1) to placebo, apremilast 20 mg BID, or apremilast 30 mg BID. At Week 16, patients with swollen and tender joint count improvement20% improvement in American College of Rheumatology response criteria (ACR20) at Week 16. Results. In the intent-to-treat population (N = 484), ACR20 at Week 16 was achieved by more patients receiving apremilast 20 mg BID [37.4% (p = 0.0002)] and 30 mg BID [32.1% (p = 0.0060)] versus placebo (18.9%). Clinically meaningful improvements in signs and symptoms of PsA, physical function, and psoriasis were observed with apremilast through Week 52. The most common adverse events were diarrhea, nausea, headache, and upper respiratory tract infection. Diarrhea and nausea generally occurred early and usually resolved spontaneously with continued treatment. Laboratory abnormalities were infrequent and transient. Conclusion. Apremilast demonstrated clinical improvements in PsA for up to 52 weeks, including signs and symptoms, physical function, and psoriasis. No new safety signals were observed. ClinicalTrials.gov identifier: NCT01212757.