The early clinical course of infliximab treatment in rheumatoid arthritis: results from the REMARK observational study.

Objectives: We aimed to describe patterns of disease activity during infliximab plus methotrexate (MTX) treatment and explore C-reactive protein (CRP) as a potential marker of early response.

Methods: REMARK was a phase IV, open-label, observational study of infliximab-naïve adults with rheumatoid arthritis (RA) who received infliximab 3 mg/kg plus MTX for 14 weeks. Treatment response was evaluated in 3 subgroups: patients with <1 year disease duration who were TNF-inhibitor (TNFi)-naïve, patients with ≥ 1 year disease duration who were TNFi-naïve, and patients who had previous TNFi failure or intolerance. In post hoc analyses, CRP kinetic profiles were analysed by EULAR response (good, moderate, non-response) in REMARK and in an independent replication with data from the ASPIRE study.

Results: In the efficacy-evaluable population (n=662), median 28-joint disease activity score (DAS28) improved from baseline to Week 14 (5.2 vs. 3.6, p<0.0001). Regardless of disease history subgroup, most patients had good or moderate EULAR responses at Weeks 2 (64.9%), 6 (74.1%), and 14 (73.6%). DAS28 and its components did not differ across patient subgroups. Disease flare occurred in 16.2% of patients. CRP levels declined markedly at Week 2, but patients who were EULAR non-responders at Week 14 showed a CRP rebound at Weeks 6 and 14. This CRP pattern was independently replicated in data from ASPIRE. Adverse events were consistent with the known risk profile of infliximab.

Conclusions: Infliximab plus MTX treatment in patients with RA rapidly diminished disease activity. A unique pattern of CRP rebound was found in non-responders early in treatment.