This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/dta.2250 This article is protected by copyright. All rights reserved. Development and validation of an optical biosensor for rapid monitoring of adalimumab in serum of patients with Crohn’s disease Sumin Bian 1 , Jiadi Lu 2 , Filip Delport 2 , Séverine Vermeire 3 , Dragana Spasic 2 , Jeroen Lammertyn 2 , Ann Gils 1* 1 Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium 2 Department of Biosystems-MeBioS, KU Leuven, Heverlee, Belgium 3 Department of Gastroenterology, University hospitals Leuven, Leuven, Belgium * Author to whom correspondence should be addressed: A. Gils Department of Pharmaceutical and Pharmacological Sciences, KU Leuven Campus Gasthuisberg O&N2, PB 820; Herestraat 49, B-3000 Leuven, Belgium Phone: +32-16-32 34 36; Fax: +32-16-32 34 60 Email: ann.gils@pharm.kuleuven.be Running title: rapid monitoring of adalimumab Abbreviations: CV, coefficient of variation; FO-probe, fiber-optic probe; FO-SPR, fiber-optic surface plasmon resonance; ICC, intraclass coefficient; LLOQ, lower limit of quantification; MA-ADM, monoclonal antibodies towards adalimumab; TDM, Therapeutic drug monitoring; TNFα, tumor necrosis factor-alpha.