To evaluate the effect of subcutaneous (s.c.) secukinumab, an interleukin-17A inhibitor, on clinical signs and symptoms and radiographic progression in patients with psoriatic arthritis (PsA). Adults (n=996) with active PsA were randomised 2:2:2:3 to s.c. secukinumab 300 mg or 150 mg with loading dose (LD), 150 mg without LD or placebo. All groups received secukinumab or placebo at baseline, weeks 1, 2 and 3 and then every 4 weeks from week 4. The primary endpoint was the proportion of patients achieving an American College of Rheumatology 20 (ACR20) response at week 16. Significantly more patients achieved an ACR20 response at week 16 with secukinumab 300 mg with LD (62.6%), 150 mg with LD (55.5%) or 150 mg without LD (59.5%) than placebo (27.4%) (p<0.0001 for all; non-responder imputation). Radiographic progression, as measured by van der Heijde-modified total Sharp score, was significantly inhibited at week 24 in all secukinumab arms versus placebo (p 0.01 for 300 mg with LD and 150 mg without LD and p<0.05 for 150 mg with LD; linear extrapolation). Adverse event rates at week 24 were similar across treatment arms: 63.1% (300 mg with LD), 62.7% (150 mg with LD), 61.1% (150 mg without LD) and 62.0% (placebo). No deaths or new safety signals were reported. S.c. secukinumab 300 mg and 150 mg with and without LD significantly improved clinical signs and symptoms and inhibited radiographic structural progression versus placebo at week 24 in patients with PsA. NCT02404350; Results.