© 2015 The Authors. British Journal of Dermatology published by John Wiley & Sons Ltd on behalf of British Association of Dermatologists. Background Apremilast, an oral phosphodiesterase 4 inhibitor, regulates immune responses associated with psoriasis. Objectives ESTEEM 2 evaluated the efficacy and safety of apremilast 30 mg twice daily for moderate-to-severe plaque psoriasis. Methods This phase III, double-blind, placebo-controlled trial randomized adults to apremilast or placebo (2: 1). At week 16, placebo patients switched to apremilast. At week 32, apremilast patients achieving ≥ 50% reduction in Psoriasis Area and Severity Index (PASI 50) were rerandomized (1: 1) to continue apremilast or receive placebo. Upon loss of 50% of PASI improvement obtained at week 32, patients rerandomized to placebo resumed apremilast. Results The modified intention-to-treat population (full analysis set) included 137 placebo and 274 apremilast patients. At week 16, significantly more apremilast patients achieved PASI 75 (28·8%), PASI 50 (55·5%) and static Physician's Global Assessment score of 0 or 1 (20·4%) vs. placebo (5·8%, 19·7%, 4·4%, respectively; P < 0·001). Most patients rerandomized to apremilast at week 32 had a PASI 50 response at week 52 (80%). Patients treated with apremilast showed significant improvements in quality of life (as assessed by the Dermatology Life Quality Index) and pruritus at week 16 compared with placebo (P < 0·001). The exposure-adjusted incidence of adverse events did not increase with continued apremilast treatment for up to 52 weeks. The most common adverse events were nausea, diarrhoea, nasopharyngitis and upper respiratory tract infection. Conclusions Apremilast was effective in the treatment of moderate-to-severe plaque psoriasis over 52 weeks.