To examine the clinical and ultrasonographic (US) outcomes of reducing methotrexate (MTX) dosage upon initiating adalimumab (ADA) in MTX-inadequate responders with moderately to severely active rheumatoid arthritis (RA).
MUSICA (NCT01185288) was a double-blind, randomized, parallel-arm study of 309 patients with RA receiving MTX ≥ 15 mg/week for ≥ 12 weeks before screening. Patients were randomized to high dosage (20 mg/week) or low dosage (7.5 mg/week) MTX; all patients received 40 mg open-label ADA every other week for 24 weeks. The primary endpoint was Week 24 mean 28-joint Disease Activity Score based on C-reactive protein (DAS28-CRP) to test for noninferiority of low-dosage MTX using a 15% margin. US images were scored using a 10-joint semiquantitative system incorporating OMERACT definitions for pathology, assessing synovial hypertrophy, vascularity, and bony erosions.
Rapid improvement in clinical indices was observed in both groups after addition of ADA. The difference in mean DAS28-CRP (0.37, 95% CI 0.07-0.66) comparing low-dosage (4.12, 95% CI 3.88-4.34) versus high-dosage MTX (3.75, 95% CI 3.52-3.97) was statistically significant and non-inferiority was not met. Statistically significant differences were not detected for most clinical, functional, and US outcomes. Pharmacokinetic and safety profiles were similar.
In MUSICA, Week 24 mean DAS28-CRP, the primary endpoint, did not meet non-inferiority for the low-dosage MTX group. Although the differences between the 2 MTX dosage groups were small, our study findings did not support routine MTX reduction in MTX inadequate responders initiating ADA.