Improvement or Worsening of Disease Activity After Switch to Sarilumab in Patients With Rheumatoid Arthritis With a Partial Response to Adalimumab.

Objective: The aim of this study was to assess the effect of switching from adalimumab to sarilumab monotherapy in partial responders with rheumatoid arthritis from the MONARCH randomized trial and its open-label extension (OLE).

Methods: Partial response was defined as improvement in Clinical Disease Activity Index (CDAI) of 12 or 6 units (baseline score: >22 or >10 and ≤22, respectively). Proportions of adalimumab partial responders with meaningful worsening or improvement at OLE weeks 12 and 24 were evaluated using 2 CDAI thresholds (≥6 and ≥12 points), 28-joint Disease Activity Score using erythrocyte sedimentation rate (≥0.6 and ≥1.2 points), Health Assessment Questionnaire Disability Index (≥0.22 and ≥0.30 points), Simple Disease Activity Index (≥7 and ≥13 points), physician and patient global assessments (≥10 and ≥20), and 28-joint swollen and tender joint counts (≥1 and ≥2 joints). Outcomes were analyzed using mixed-effect models with repeated measures for observed cases. The p values were produced using Wilcoxon tests.

Results: Of 369 enrolled patients, 320 (87%) entered the OLE and 155 switched from adalimumab to sarilumab; 59% (91/155) were partial responders. At week 24, 4%-17% and 2%-12% of partial responders experienced a worsening using the lower and higher thresholds, respectively, whereas 47%-78% and 27%-66% experienced improvement.

Conclusions: Partial responders to adalimumab who switched to sarilumab had a low likelihood of experiencing meaningful worsening, with most patients showing meaningful improvement or no change in disease activity. This may help alleviate patients' fears of worsening when considering switching to a treatment with a different mechanism of action.