# Real-world comparative effectiveness of sarilumab versus Janus kinase inhibitors as monotherapy in rheumatoid arthritis

## TL;DR

This study compares the real-world effectiveness of two rheumatoid arthritis treatments, sarilumab and JAK inhibitors, when used without methotrexate, finding similar outcomes but differences in safety and steroid use.

## Contribution

The study provides real-world evidence comparing sarilumab and JAK inhibitors as methotrexate-free monotherapies in rheumatoid arthritis, identifying biomarkers for treatment response and safety differences.

## Key findings

- Sarilumab and JAK inhibitors showed similar drug retention and disease control over 12 months.
- Sarilumab had lower adverse event-related discontinuation and higher glucocorticoid discontinuation in early treatment phases.
- Higher CRP and platelet count with lower hemoglobin predicted better response to sarilumab in younger patients.

## Abstract

Sarilumab (SAR), an interleukin-6 receptor inhibitor (IL-6Ri), and Janus kinase inhibitors (JAKi) are approved options for rheumatoid arthritis (RA) when methotrexate (MTX) cannot be used. Real-world evidence for MTX-free monotherapy remains limited.

We conducted a multicenter retrospective cohort study of RA patients receiving SAR or JAKi as MTX-free monotherapy. To reduce confounding, 1:1 propensity score matching was performed in the overall cohort (n = 252, 126 per group) and separately within treatment-line strata: Phase 2 first-line biologic/targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs: 45 per group), Phase 3 second-line b/tsDMARDs (53 per group), and Phase 3 ≥ third-line b/tsDMARDs (47 per group). Outcomes over 12 months included drug retention, change in Clinical Disease Activity Index (CDAI), glucocorticoid (GC) tapering and discontinuation, low disease activity (LDA, CDAI ≤ 10), and safety profiles. Predictors of LDA were evaluated with logistic regression. This multicenter real-world.

Across matched strata by prior b/tsDMARDs, retention and CDAI change did not differ significantly between SAR and JAKi through 12 months. When classified by cause, adverse events (AEs)-related discontinuation was higher with JAKi, yielding lower AE-specific retention. Both groups demonstrated GC sparing overtime, with a greater increase in GC discontinuation for SAR than for JAKi in Phase 2. Baseline predictors of achieving LDA at 12 months included higher C-reactive protein (CRP) and platelet count (Plt) in both groups, with additional associations of younger age and lower hemoglobin (Hb) in the SAR. In safety analyses, overall AEs were less frequent with SAR than with JAKi, driven by lower risks of infection including herpes zoster, while other categories were similarly infrequent.

SAR and JAKi showed no statistically significant differences in 12-month retention or disease control in MTX-free monotherapy settings. Higher CRP and Plt with lower Hb, particularly in younger patients, identified better response to SAR and support biomarker guided selection between IL-6Ri and JAKi. In Phase 2, GC discontinuation with SAR suggests a practical strategy to reduce AEs while maintaining efficacy. Prospective studies should validate these findings and define actionable thresholds.

The online version contains supplementary material available at 10.1186/s13075-025-03722-5.