The effect of methotrexate on tumour necrosis factor concentrations in etanercept-treated rheumatoid arthritis patients

Objectives Recently, we demonstrated that early low concentrations of circulating, adalimumab-bound TNF in RA patients treated with adalimumab was associated with future anti-drug antibody formation. Furthermore, low TNF was associated with less frequent baseline MTX use. This is remarkable, because of the anti-inflammatory effects of MTX and a potential inhibiting effect on cytokine production. We hypothesized an indirect effect of non-MTX use...