Because GSTs (GSTM1, GSTP1, and GSTT1) metabolise the original drug or metabolites of steroids, vincristine, anthracycline, methotrexate, cyclophosphamide, and etoposide, correlations between clinical response and GST polymorphisms have also been investigated in different therapeutic modalities, including MTX-containing protocols in patients with SLE, IBD [25,26,27], and malignant diseases, especially leukaemias [28,29,30]. This evidence concerns the gene GSTM1 and systemic lupus erythematosus.