Baricitinib further enhances disease-modifying effects by uncoupling the link between disease activity and joint structural progression in patients with rheumatoid arthritis

Objectives To evaluate if baricitinib, a Janus kinase inhibitor, further enhances disease-modifying effects by uncoupling the link between disease activity and structural damage progression in patients with rheumatoid arthritis (RA) using two phase III randomised, double-blinded trials. Methods In RA-BEAM, patients with established RA and inadequate response to methotrexate (MTX-IR) received placebo (PBO), baricitinib 4 mg or adalimumab 40 mg on background MTX. In RA-BEGIN, conventional synthetic disease-modifying antirheumatic drug (csDMARD)-naive patients received MTX, baricitinib 4 mg or baricitinib 4 mg plus MTX. Using linear regression analyses, joint damage progression (assessed by change from baseline in van der Heijde modification of the Total Sharp Score) was compared between treatment groups for patients achieving certain disease activity states by the Clinical Disease Activity Index. Time-averaged postbaseline responses were used to week 24 (RA-BEAM) and week 52 (RA-BEGIN). Results For MTX-IR patients, structural damage progression was reduced regardless of disease activity states in baricitinib-treated patients (p=0.6), whereas in PBO patients there was a clear dependence on disease activity states, being significantly lower in those who achieved remission/low disease activity (REM/LDA) compared with moderate/high disease activity (MDA/HDA) (p=0.02). Furthermore, the baricitinib MDA/HDA group had less damage progression than the PBO MDA/HDA group (p<0.001). For csDMARD-naive patients, progression was lower in REM/LDA versus MDA/HDA within the MTX group (p<0.001). However, for baricitinib+MTX (p=0.5) or baricitinib monotherapy (p=0.07), progression was similar regardless of disease activity. In MDA/HDA groups, progression was lower with baricitinib+MTX (p<0.001) and numerically lower with baricitinib monotherapy (p=0.07) versus MTX. C reactive protein (<= 5 mg/L and >5 mg/L) sensitivity analyses supported the primary findings. Conclusions Baricitinib reduces structural damage progression versus PBO with background MTX and/or MTX, even in patients with MDA/HDA, showing a disease-modifying effect across all disease activity states.