The study by Lee et al, including nine articles involving 1275 RA patients, reported that patients carrying the ABCB1 C3435T may have an increased risk of MTX-related toxicity (TC vs. TT + CC; OR = 0.483, 95 % CI = 0.259–0.900, p = 0.022), but such a SNP does not predict RA susceptibility nor responsiveness to DMARDs [93]. This evidence concerns the gene ABCB1 and rheumatoid arthritis.