KEY MESSAGE The available evidence related to the safety of combination therapy with LEF and MTX in patients with RA is limited and inconclusive. [...] SUMMARY OF FINDINGS The literature search identified two systematic reviews 5,6 examining the efficacy and toxicity of combination therapy of MTX and non-biologic DMARD compared to either LEF or MTX alone. [...] Systematic reviews and meta-analyses The characteristics of the systematic reviews are summarized in table 1. The safety outcome, author’s conclusions and limitations of the systematic reviews are summarized in table 2. The systematic review by Katchamart et al.6 included 19 RCTs of which only one RCT compared DMARDS relevant to the research question of this report. [...] The major endpoints analyzed were improvement of clinical outcomes [as defined by the American College of Rheumatology (ACR) or the European League against Rheumatism (EULAR)], improvement of the patients’ Health Related Quality of Life (HRQoL) and incidence of side effects. [...] Safety of Leflunomide and Methotrexate as Combination Therapy for Rheumatoid Arthritis 5 Non-randomized studies Curtis et al 20108 conducted a cohort study using the Consortium of Rheumatology Researchers of North America (CORRONA) data base to determine the relationship between the use of DMARD medication and the incidence of ALT and aspartate transaminase (AST) elevations.