Ixekizumab, an interleukin-17A specific monoclonal antibody, for the treatment of biologic-naive patients with active psoriatic arthritis: results from the 24-week randomised, double-blind, placebo-controlled and active (adalimumab)-controlled period of the phase III trial SPIRIT-P1.

Objective: To assess the safety and efficacy of ixekizumab, a monoclonal antibody that inhibits interleukin-17A, in a double-blind phase III trial enrolling patients with active psoriatic arthritis (PsA).

Methods: Patients naive to biologic therapy with active PsA were randomised to subcutaneous injections of placebo (N=106), adalimumab 40 mg once every 2 weeks (active reference; N=101), ixekizumab 80 mg once every 2 weeks (IXEQ2W) (N=103), or ixekizumab 80 mg once every 4 weeks (IXEQ4W) (N=107). Both ixekizumab regimens included a 160-mg starting dose. The primary objective was to assess the superiority of IXEQ2W or IXEQ4W versus placebo as measured by the proportion of patients achieving an American College of Rheumatology 20 (ACR20) response at week 24.

Results: Significantly more patients treated with ixekizumab achieved an ACR20 response with IXEQ2W (62.1%) or IXEQ4W (57.9%) than placebo (30.2%) (p≤0.001; non-responder imputation method). Disease activity and functional disability were significantly improved with both ixekizumab doses versus placebo at weeks 12 and 24, and there was significantly less progression of structural damage at week 24 (p≤0.01). Clearance of plaque psoriasis was greater with ixekizumab than placebo (p≤0.001). Efficacy results with adalimumab, the active reference arm, showed significant improvements versus placebo. Treatment-emergent adverse events were more frequent with ixekizumab (65.7-66.4%) and adalimumab (64.4%) than placebo (47.2%) (p<0.05).

Conclusions: In biologic-naive patients with active PsA, ixekizumab treatment resulted in improvements in disease activity and physical function, as well as in the inhibition of structural damage progression. Overall, adverse events were more frequent in all active groups compared with placebo.

Trial Registration Number: NCT01695239; EudraCT2011-002326-49; Results.