Background/Purpose: Ixekizumab (IXE) is a high-affinity monoclonal antibody that selectively targets interleukin-17A. Here, we present integrated efficacy data at Week 24 from two phase 3 trials of IXE for the treatment of psoriatic arthritis (PsA).

Methods: Patients with active PsA (SPIRIT-P1) and with prior lack of efficacy or intolerance to TNF-inhibitor(s) (SPIRIT-P2) were randomized to placebo (PBO, N=224), 80 mg IXE every 4 weeks (IXEQ4W, N=229) or every 2 weeks (IXEQ2W, N=226), after a 160 mg starting dose. All patients considered as inadequate responders at Week 16 received rescue therapy (changes in background therapy), while inadequate responders to PBO were also re-randomized to IXEQ4W or IXEQ2W. Continuous data were analyzed using mixed-effects model for repeated measures; categorical data, using a logistic regression model with missing values imputed by non-responder imputation.

Results: At Week 24, significantly more patients treated with either dose of IXE (p<.001) compared to PBO achieved the primary endpoint of ACR 20, as well as ACR 50, ACR 70, and HAQ-DI change from baseline. Treatment with either dose of IXE resulted in significantly more patients achieving resolution of enthesitis (LEI; p<.05) and dactylitis (LDI-B; p<.001) compared to PBO. LDI-B improvements from baseline were also significantly greater (p<.05) for IXE-treated patients versus PBO. Finally, greater skin clearance (via PASI improvement) was significantly higher for IXE-treated patients (p<.001).

Conclusion: Patients treated with either dose regimen of IXE achieved significantly greater improvements in arthritis, physical function, and skin lesions compared to PBO at Week 24.