Objective: The Psoriatic Arthritis Long-term Assessment of Clinical Efficacy (PALACE) clinical trial programme findings demonstrated that apremilast, an oral phosphodiesterase 4 inhibitor, is effective for treating psoriatic arthritis (PsA). Enthesitis and dactylitis are difficult-to-treat features of PsA leading to disability and affecting quality of life. PALACE 1, 2 and 3 data were pooled to assess the efficacy of apremilast on enthesitis and dactylitis outcomes in patients with these conditions at baseline.

Methods: Patients with enthesitis (n=945) or dactylitis (n=633) at baseline were analysed after receiving double-blind treatment with placebo, apremilast 30 mg two times per day or apremilast 20 mg two times per day up to 52 weeks and continuing up to 5 years. Data were analysed through 156 weeks. Enthesitis was evaluated by Maastricht Ankylosing Spondylitis Enthesitis Score (MASES) and dactylitis via dactylitis count.

Results: At week 24, patients receiving apremilast 30 mg two times per day demonstrated a significantly greater mean change in enthesitis (-1.3 vs -0.9; p

Conclusion: Apremilast is effective for the treatment of active PsA, including improvements in enthesitis and dactylitis up to 3 years.

Trial registration numbers: NCT01172938, NCT01212757 and NCT01212770.