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Updated: Mar 18, 2026

An Adoptive Transfer Model of Rheumatoid Arthritis in Mice
Published on: June 6, 2025
Immunogenicity of tocilizumab in patients with rheumatoid arthritis
Johanna Sigaux1, Moustafa Hamze2, Claire Daien3
1Service de rhumatologie, hôpital de Bicêtre, hôpitaux universitaires Paris Sud, Assistance publique-Hôpitaux de Paris, 78, rue du Général-Leclerc, 94275 Le Kremlin-Bicêtre, France; Inserm U1184, université Paris Sud, 91400 Orsay, France; Labex LERMIT, 94270 Le Kremlin-Bicêtre, France.
Objective:
The immunogenicity of tocilizumab (TCZ) has been poorly studied. We assessed the immunogenicity of TCZ and serum TCZ trough levels in rheumatoid arthritis (RA) patients and the preexisting TCZ-specific CD4+ T cell repertoire in healthy controls.
Methods:
Anti-drug antibodies (ADAs) to TCZ and serum TCZ trough levels in RA patients were assessed at different times by ELISA. Frequencies of naive anti-TCZ CD4+ precursors were studied in healthy controls.
Results:
In total, 91 samples from 40 RA patients were analyzed: 21 patients within the first 6 months after treatment initiation and 19 during follow-up after a mean TCZ treatment duration of 21±13 months. None of the 91 samples showed persistent ADAs to TCZ. Only 3 RA patients showed transient and low titers of anti-TCZ ADAs. Serum TCZ trough levels were associated with neither patient characteristics (gender, body mass index) nor disease activity and were identical for patients with and without co-treatment with methotrexate. Three of 9 healthy donors showed preexisting TZC-specific CD4+ T cells at a low level.
Conclusion:
Serum TCZ trough levels were not affected by patient characteristics. The occurrence of ADAs to TCZ was a rare event. Because healthy donors show the same frequency of naive TCZ-specific and infliximab-specific CD4+ T cell precursors, the low prevalence of ADAs to TCZ might result from interleukin-6 blockade.
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