Objectives: To compare efficacy and safety of sarilumab monotherapy with adalimumab monotherapy in patients with active rheumatoid arthritis (RA) who should not continue treatment with methotrexate (MTX) due to intolerance or inadequate response.

Methods: MONARCH was a randomised, active-controlled, double-blind, double-dummy, phase III superiority trial. Patients received sarilumab (200 mg every 2 weeks (q2w)) or adalimumab (40 mg q2w) monotherapy for 24 weeks. The primary end point was change from baseline in 28-joint disease activity score using erythrocyte sedimentation rate (DAS28-ESR) at week 24.

Results: Sarilumab was superior to adalimumab in the primary end point of change from baseline in DAS28-ESR (-3.28 vs -2.20; p<0.0001). Sarilumab-treated patients achieved significantly higher American College of Rheumatology 20/50/70 response rates (sarilumab: 71.7%/45.7%/23.4%; adalimumab: 58.4%/29.7%/11.9%; all p≤0.0074) and had significantly greater improvement in Health Assessment Questionnaire-Disability Index (p=0.0037). Importantly, at week 24, more patients receiving sarilumab compared with adalimumab achieved Clinical Disease Activity Index remission (7.1% vs 2.7%; nominal p=0.0468) and low disease activity (41.8% vs 24.9%; nominal p=0.0005, supplemental analysis). Adverse events occurred in 63.6% (adalimumab) and 64.1% (sarilumab) of patients, the most common being neutropenia and injection site reactions (sarilumab) and headache and worsening RA (adalimumab). Incidences of infections (sarilumab: 28.8%; adalimumab: 27.7%) and serious infections (1.1%, both groups) were similar, despite neutropenia differences.

Conclusions: Sarilumab monotherapy demonstrated superiority to adalimumab monotherapy by improving the signs and symptoms and physical functions in patients with RA who were unable to continue MTX treatment. The safety profiles of both therapies were consistent with anticipated class effects.

Trial registration number: NCT02332590.