To compare the efficacy and safety of brodalumab, an interleukin-17 receptor subunit A inhibitor, with placebo, in patients with psoriatic arthritis (PsA).Adult patients with active PsA and inadequate response to, or intolerance to, conventional treatment were enrolled into two phase III studies (NCT02029495 and NCT02024646) and randomised 1:1:1 to receive subcutaneous brodalumab 140 mg or 210 mg or placebo at weeks 0, 1 and every 2 weeks up to 24 weeks. About 30% of patients had prior use of biologics. The primary endpoint for both studies was the American College of Rheumatology 20 (ACR20) response at week 16.962 patients were randomised across the studies prior to early termination due to sponsor decision. The primary endpoint was met in both studies. Based on comparable design and eligibility criteria, data from both studies were pooled. Significantly more patients achieved ACR20 at week 16 in both brodalumab treatment groups (45.8% and 47.9% for 140 mg and 210 mg, respectively) versus placebo (20.9%) (p<0.0001). Similar results were observed at week 24. Significantly higher proportions of patients receiving brodalumab achieved ACR50/70, Psoriasis Area and Severity Index 75/90/100 and resolution of dactylitis and enthesitis versus placebo (p<0.01). Adverse event rates were similar across treatments at week 16 (54.4%, 51.6% and 54.5% for placebo, brodalumab 140 mg and 210 mg, respectively). No new safety signals were reported.Brodalumab was associated with rapid and significant improvements in signs and symptoms of PsA versus placebo. Brodalumab was well tolerated, with a safety profile consistent with other interleukin-17 inhibitors.