Multicentre, randomised, open-label, parallel-group study evaluating the efficacy and safety of ixekizumab versus adalimumab in patients with psoriatic arthritis naïve to biological disease-modifying antirheumatic drug: final results by week 52

Objectives: SPIRIT head-to-head (H2H) is a 52-week (Wk) trial comparing ixekizumab (IXE) with adalimumab (ADA) for simultaneous American College of Rheumatology (ACR)50 and Psoriasis Area and Severity Index (PASI)100 responses in 566 patients (distributed evenly across both groups) with psoriatic arthritis (PsA). IXE was superior to ADA for this primary end point at Wk24. We aimed to determine the final efficacy and safety results through Wk52 including a prespecified subgroup analysis of concomitant conventional synthetic disease-modifying anti-rheumatic drugs (csDMARD) use.

Methods: SPIRIT-H2H is a Wk52 multicentre, open-label, blinded-assessor study comparing IXE and ADA in bionaïve patients with PsA. Patients were randomised 1:1 to IXE or ADA with stratification by concomitant csDMARD use and presence of moderate-to-severe plaque psoriasis. Prespecified end points at Wk24 and Wk52 included musculoskeletal, psoriasis, quality-of life outcomes, subgroup analyses and safety.

Results: A significantly higher proportion of patients treated with IXE versus ADA simultaneously achieved ACR50 and PASI100 (39% vs 26%, p<0.001), PASI100 (64% vs 41%, p<0.001) at Wk52. Efficacy of IXE and ADA was similar at Wk52 for ACR50 (49.8% vs 49.8%, p=0.924), treat-to-target outcomes, enthesitis and dactylitis resolution. Responses to IXE were consistent irrespective of concomitant csDMARD use. Significantly more patients on IXE monotherapy versus ADA monotherapy had simultaneous ACR50 and PASI100 (38% vs 19%, p=0.007), and PASI100 responses (66% vs 35%, p<0.001) at Wk52. There were no new safety findings for IXE or ADA.

Conclusions: IXE provided significantly greater simultaneous joint and skin improvement than ADA through Wk52 in bionaïve patients with PsA. IXE showed better efficacy on psoriasis and performed at least as well as ADA on musculoskeletal manifestations. IXE efficacy was consistent irrespective of concomitant csDMARD use.

Trial registration number: NCT03151551.