Date: Sunday, November 8, 2015
Session Type: ACR Poster Session A
Session Time: 9:00AM-11:00AM
Biological compounds have belonged to the therapeutic options for the treatment of rheumatoid arthritis for about 15 years. The application of biological substances is subject to a risk of developing antibodies against these structures, causing adverse events or loss of efficacy. It was the aim of the study to analyse the clinical relevance of anti-drug antibodies and drug levels in the course of a long term treatment of patients with rheumatoid arthritis with etanercept (ETN).
In this retrospective analysis, 508 serum samples from 102 RA patients (84 female/18 male, mean age 50.8±1.5 years, mean disease duration 10.8±0.8 years) were obtained after 6, 12, 24, 36 and 48 months of treatment with ETN, and selected for determination of anti-ETN antibodies and drug levels. If available, serum samples obtained at least 2 weeks after discontinuation of ETN treatment (due to side effects, non-response, remission or surgery) were used for analysis to exclude any interference of high drug levels with the anti-drug antibody assay. For the determination of anti-ETN and ETN levels, Promonitor® – assays (Proteomika, Spain) were used according to the manufacturer’s instructions.
Mean baseline disease activity (DAS28) of 5.77±0.11 decreased to 3.72±0.14, 3.46±0.12, 3.43±0.15 and 3.16±0.15 after 6, 12, 24 and 48 months of ETN treatment. No anti-ETN antibodies were found at any time point, neither in the course of treatment nor in samples from 72 of these patients obtained at least two weeks after discontinuation of ETN treatment (mean 51±3.9 months, range 18-120 months).
Mean ETN serum levels were 3.58±0.17µg/ml, 4.33±0.24µg/ml, 4.22±0.29µg/ml, 4.21±0.27 and 4.66±0.42µg/ml after 6, 12, 24, 36 and 48 months respectively. ETN levels remained stable in most patients, mean levels between individual patients ranged between 0.9 and 9.91µg/ml. In the lower quartile of patients with mean ETN level <2.5µg/ml, the DAS28 decreased from 5.46±0.26 to 3.79±0.19 (-1.67), 4.06±0.45 (-1.40), and 3.74±0.40 (-1.72) after 6, 24 and 48 months. A stronger DAS28 improvement was found in the upper quartile >5.07µg/ml from 6.10±0.21 to 3.74±0.33 (-2.36), 3.19±0.23 (-2.91), and 3.03±0.19 (-3.07) respectively.
Our study confirms the lack of anti-drug antibodies in a large cohort of RA patients in the course of a long-term treatment with ETN. The absence of anti-ETN antibodies in serum samples after discontinuation of therapy confirms this result by exclusion of false negative results resulting from interference with high ETN levels in the course of treatment.
ETN serum levels are subject to strong variations between individual patients. A significant reduction of disease activity was found in each quartile, the greatest mean reduction was observed in the group with the highest ETN serum levels.
To cite this abstract in AMA style:Drynda S, Kekow J. Clinical Relevance of Etanercept Levels and Anti-Etanercept Antibodies in Long-Term Treatment of Rheumatoid Arthritis Patients [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/clinical-relevance-of-etanercept-levels-and-anti-etanercept-antibodies-in-long-term-treatment-of-rheumatoid-arthritis-patients/. Accessed October 19, 2021.
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