Moreover, a tendency was found toward an association between the FOXP3 rs3761548-GT and GG genotypes and asthenia during MTX therapy (GT vs. TT/GG: OR = 3.25, 95% CI = 1.14–9.79; GG vs. TT/GT: OR = 1.12, 95% CI = 0.35–3.53, p = 0.051; Table S20). This evidence concerns the gene FOXP3 and asthenia.