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Tocilizumab (TCZ) has been approved for giant cell arteritis (GCA). Interleukin-6 (IL-6) receptor blockade suppresses clinical disease and is steroid sparing.1 2 Since IL-6 induces the acute-phase response, the clinically used inflammation markers (C reactive protein (CRP), erythrocyte sedimentation rate (ESR)) are suppressed during TCZ treatment. Whether serum IL-6 is useful in monitoring disease activity and detecting infections in TCZ-treated GCA is unknown.
We longitudinally measured IL-6 in 23 patients with intravenous TCZ–treated GCA, two patients with polymyalgia rheumatica and one patient with Takayasu arteritis of our GCA cohort (EKBB-239/09), and in 13/26 patients additionally before TCZ treatment. Patient characteristics are shown in table 1. At each visit, clinical and laboratory parameters (white blood cell (WBC), CRP, ESR) were assessed. Relapse was defined as the need for treatment intensification following new or increasing symptoms, or rising CRP/ESR not otherwise explained.2
During TCZ therapy, CRP, ESR and WBC rapidly declined and were sustainably suppressed. IL-6 levels rose and remained elevated throughout TCZ treatment (figure 1). Daily prednisone doses were successfully tapered after TCZ was initiated (figure 1C). During 23.8 patient-years of TCZ therapy, eight infections were documented with available IL-6 levels (online supplementary table S1). IL-6, but not CRP, ESR …
CTB and BR-C contributed equally.
Handling editor Josef S Smolen
Contributors CTB collected the data, analysed data and drafted the manuscript. BR-C collected the data, analysed data and drafted the manuscript. MR has analysed data and contributed to the manuscript writing. TM recruited patients and contributed to the manuscript writing. TD designed the study, analysed data and drafted the manuscript.
Funding This work was funded by the Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (grant no. SNSF PZ00P3-173517) and the ‘Margot und Erich Goldschmidt & Peter René Jacobson-Stiftung’ (both to CTB). MR is supported by a professorship of the Swiss National Science Foundation (PP00P3_173186).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data are available as online supplementary data.
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