ABCC1, ABCG2 and FOXP3: Predictive Biomarkers of Toxicity from Methotrexate Treatment in Patients Diagnosed with Moderate-to-Severe Psoriasis

Background: Methotrexate (MTX) is one of the most extensively used drugs in the treatment of moderate-to-severe psoriasis (PS). However, it frequently must be suspended owing to the toxicity in certain patients. Objective: To evaluate the influence of ABCC1, ABCG2, and FOXP3 in the development of MTX toxicity in PS. Methods: Retrospective cohort study with 101 patients. Five single-nucleotide polymorphisms (SNPs) were genotyped using real-time polymerase chain reaction with TaqMan probes. Results: Patients carrying ABCC1 rs2238476-AG genotype (AG vs. GG: OR = 8.04; 95% CI = 1.48–46.78; p = 0.015); FOXP3 rs376154-GT and GG genotypes (GT vs. TT/GG: OR = 3.86; 95% CI = 1.17–13.92; p = 0.031) and ABCG2 rs13120400-T allele (T vs. CC: OR = 8.33; 95% CI = 1.24–164.79; p = 0.059) showed a higher risk of developing more than one adverse effect. The toxicity analysis by subtypes showed that the ABCC1 rs2238476-AG genotype (AG vs. GG: OR = 8.10; 95% CI = 1.69–46.63; p = 0.011) and FOXP3 rs376154-GT genotype (OR = 4.11; 95% CI = 1.22–15.30; p = 0.027) were associated with the appearance of asthenia. No association of the other ABCC1 polymorphisms (rs35592 and rs246240) with MTX toxicity was found. Conclusion: ABCC1, ABCG2, and FOXP3 polymorphisms can be considered to be risk biomarkers of toxicities in PS patients treated with MTX.