Objective To compare the effects of interleukin-6 (IL-6) receptor and tumour necrosis factor inhibition on inducing repair of existing bone erosions in patients with very early rheumatoid arthritis (RA).
Methods Prospective non-randomised observational study in patients with active erosive RA with inadequate response to methotrexate (MTX) receiving either tocilizumab (TOC) monotherapy or adalimumab (ADA) with MTX for 52 weeks. Erosion volumes were assessed in metacarpal heads (MCH) and the radius by high-resolution peripheral quantitative CT at baseline and after 52 weeks. Clinical response was monitored using Clinical Disease Activity Index, Simple Disease Activity Index and Disease Activity Score 28-erythrocyte sedimentation rate (DAS28-ESR) scores every 12 weeks.
Results TOC (N=33) and ADA/MTX (N=33) treatment groups were balanced for age, sex, body mass index, comorbidities, disease and activity, functional state, autoantibody status, baseline bone damage and baseline bone biomarkers. Both TOC (DAS28-ESR: baseline: 6.2±0.5; 52 weeks: 2.3±1.0) and ADA/MTX (6.3±0.6; 2.8±1.2) significantly reduced disease activity. Erosion volumes significantly decreased in the MCH and radius of patients with RA treated with TOC (p<0.001) but not in patients treated with ADA/MTX (p=0.77), where they remained stable in size. Mean decrease in erosion volume in TOC-treated patients was −1.0±1.1 mm3 and −3.3±5.9 mm3 in the MCH and radius of TOC-treated patients, respectively, and −0.05±0.9 mm3 and −0.08±4.1 mm3 in patients treated with ADA/MTX.
Conclusions The REBONE study shows that TOC monotherapy achieves more pronounced repair of existing bone erosions than ADA/MTX. Hence, IL-6 is a central factor for the disturbed bone homeostasis in the joints of patients with RA.
- rheumatoid arthritis
- bone erosion
- tumor necrosis factor
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Handling editor Josef S Smolen
Contributors SF recruited the patients and performed the CT scans. SK and AR read the images. RK and CF collected the data and performed the statistical analysis. JR and GS wrote the manuscript.
Funding REBONE study is an investigator-initiated study that was in part supported by a grant from Chugai.
Competing interests None declared.
Patient consent for publication Parental/guardian consent obtained
Ethics approval The study was approved by the institutional review board of the University Clinic of Erlangen (324_16B and 334_18B).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information.