Celgene International’s oral small-molecule inhibitor of phosphodiesterase 4 (PDE4), apremilast, has met the primary endpoint of ACR20 in a PALACE-1 study, the first of three pivotal phase III studies.

The double-blind, multi-centre, placebo-controlled, parallel-group trial, which has enrolled 500 patients suffering with psoriatic arthritis, were randomised 1:1:1 to receive either apremilast, 20mg BID, 30mg BID, or identically-appearing placebo for 24 weeks.

The study’s primary endpoint is the proportion of patients in each treatment group who achieved the American College of Rheumatology criteria for 20% improvement (ACR20) compared to baseline at week 16.

Secondary endpoints included other measures of signs and symptoms, physical function and patient-reported outcomes.

The study’s overall safety profile was consistent in comparison to the previous phase II programme, and tolerability was improved.

The study also met ACR50 and ACR70 endpoints through week 24 in patients from the active treatment arms and also maintained significant improvements.

The PALACE-1 study is ongoing and the study extension remains blinded until all patients complete week 52, according to the company.

Two pivotal randomised, placebo-controlled phase III studies (PALACE 2 and PALACE 3) of apremilast are expected in the third quarter of 2012.

The company said results of two pivotal (ESTEEM 1 and 2) studies of apremilast, which are ongoing in more than 1,200 patients with moderate-to-severe psoriasis, are expected to be received by the end of 2012.

The company is planning to submit combined PALACE study new drug application (NDA) in the first half of 2013, while sNDA and combined MAA in the second half of 2013.