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An observational study of patients with active rheumatoid arthritis (RA) or spondyloarthritis (SpA) experiencing secondary failure to TNF inhibitor (TNFi) therapy showed that (secondary) loss of efficacy to a TNFi was associated with anti-drug antibodies in less than 30% of patients.
Investigators analyzed and compared 570 patients treated with etanercept (ETN), infliximab (INF) or adalimumab (ADL). Compared with SpA (n = 294) patients, RA patients (n = 276) were more likely to be female (80 vs 39%), older (56 vs 48 years), on DMARDs (83 vs 47%) and had slightly longer disease control for longer (202 vs 170 weeks) before their secondary TNFi failure.
No anti-drug antibodies were found with ETN, but were seen INF (27.1%) and ADA (29.0%) treated patients; 81% of these had no detectable serum drug levels.
While significiantly more SpA (31.3%) patients had anti-INF antibodies than RA (21.1%; P = 0.014), there were few patients patients developing anti-drug antibodies while on concomitant DMARDs (16.5%) compared to those on on monotherapy (26.4%; P < 0.05).
While these data show the potential impact of anti-drug antibodies in the loss of TNFi, efficacy, it appears to be a minor role (<30% of patients) and is not otherwise explained by concomitant DMARD use or the disorder under treatment. Secondarly anti-TNF failure appears to have multiple etiologies.