Relación entre los polimorfismos genéticos relacionados con el transporte celular, poliglutamación y metabolismo del metotrexato y la respuesta terapéutica en artritis reumatoide

Resumo

Methotrexate (MTX) is the first-choice treatment in rheumatoid arthritis (RA). There is a high variability in the therapeutic response. We conducted a case-control study nested in a cohort of 301 RA patients treated with MTX in monotherapy with the aim to explore the influence of clinical characteristics and different polymorphisms related to transport and metabolic pathways of MTX on the therapeutic response. The outcome variables were the response (low activity and remission measured by DAS28PCR) and MTX toxicity. We studied the SNPs ABCB1_C3435T, GGH_T16C, FPG_G2782A, MTHFR_C677T, MTHFR_A1298C, AMPD1_C34T, ADA_A534G and ITPA_C94A, and variables related to the patient, the disease and the treatment. In a cohort representative of severe RA, half of the patients, especially women, smokers and with more baseline severity, did not reach a sufficient response with monotherapy. Adverse events, gastrointestinal, neurological and hepatic mainly, were recorded in 50% of patients, which caused the suspension of MTX in an 18% of the total. Toxicity was associated to women, younger age and comorbidity. Most of the SNPs studied have been associated with some outcome measure, highlighting the association of MTHFR_1298ACc with poor response and MTHFR_677TCc with good response. Some SNPs showed a protective effect for toxicity, but, in general, they were frequently associated with global (MTHFR_677CTc, GGH_16TCc) and hepatic (MTHFR_1298ACc, ADA_534AGc) toxicity, especially in men. Genetic association studies should take into account the sex of patients and other clinical variables. Smoking is the main modifiable risk factor of MTX response.