Ixekizumab Demonstrates Consistent Efficacy Versus Adalimumab in Biologic Disease-Modifying Anti-rheumatic Drug-Naïve Psoriatic Arthritis Patients Regardless of Psoriasis Severity: 52-Week Post Hoc Results from SPIRIT-H2H

Introduction Ixekizumab, a selective interleukin-17A antagonist, was compared with adalimumab in the SPIRIT-H2H study (NCT03151551) in patients with psoriatic arthritis (PsA) and concomitant psoriasis. This post hoc analysis reports outcomes to week 52 in patients from SPIRIT-H2H, stratified by baseline psoriasis severity. Methods SPIRIT-H2H was a 52-week, multicenter, randomized, open-label, rater-blinded, parallel-group study of biologic disease-modifying antirheumatic drug (DMARD)-naïve patients ( N = 566) with PsA and active psoriasis (≥ 3% body surface area involvement). Patients were randomized to ixekizumab or adalimumab (1:1) with stratification by baseline concomitant use of conventional synthetic DMARDs and psoriasis severity (with/without moderate-to-severe psoriasis). Patients received on-label dosing according to psoriasis severity. The primary endpoint was the proportion of patients simultaneously achieving ≥ 50% improvement in American College of Rheumatology criteria (ACR50) and 100% improvement in Psoriasis Area Severity Index (PASI100) at week 24. Secondary endpoints included musculoskeletal, disease activity (defined by composite indices), skin and nail, quality of life and safety outcomes. In this post hoc analysis, primary and secondary endpoints of SPIRIT-H2H were analyzed by baseline psoriasis severity. Results A greater proportion of patients achieved the combined endpoint of ACR50 + PASI100 and PASI100 with ixekizumab compared with adalimumab at weeks 24 and 52, regardless of baseline psoriasis severity. ACR response rates were similar for ixekizumab and adalimumab across both patient subgroups. For musculoskeletal outcomes, similar efficacy was seen for ixekizumab and adalimumab, but ixekizumab showed greater responses for skin outcomes regardless of psoriasis severity. The safety profiles of ixekizumab and adalimumab were consistent between subgroups. Conclusions Regardless of baseline psoriasis severity, ixekizumab demonstrated greater efficacy than adalimumab with respect to simultaneous achievement of ACR50 + PASI100, and showed consistent and sustained efficacy across PsA-related domains. It also demonstrated higher response rates for skin outcomes. These subgroup analyses highlight the efficacy of ixekizumab in patients with PsA irrespective of the severity of concomitant psoriasis.