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Automated functional characterization of radiolabeled antibodies: a time-resolved approach

Wang, Ellena,*; Björkelund, Hannab,c,*; Mihaylova, Dessislavaa; Hagemann, Urs B.a; Karlsson, Jennya; Malmqvist, Magnusb,c,d; Buijs, Josb,c; Abrahmsén, Larsa; Andersson, Karlb,c,d

Nuclear Medicine Communications: July 2014 - Volume 35 - Issue 7 - p 767–776
doi: 10.1097/MNM.0000000000000117
Original Articles

Background The number of radiolabeled monoclonal antibodies (mAbs) used for medical imaging and cancer therapy is increasing. The required chemical modification for attaching a radioactive label and all associated treatment may lead to a damaged mAb subpopulation. This paper describes a novel method, concentration through kinetics (CTK), for rapid assessment of the concentration of immunoreactive mAb and the specific radioactivity, based on monitoring binding kinetics.

Methods The interaction of radiolabeled mAb with either the antigen or a general mAb binder such as Protein A was monitored in real time using the instrument LigandTracer. As the curvature of the binding trace has a distinct shape based on the interaction kinetics and concentration of the functional mAb, the immunoreactive mAb concentration could be calculated through reverse kinetic fitting of the binding curves, using software developed for this project. The specific activity, describing the degree of radioactive labeling, was determined through the use of calibrated signal intensities.

Results The performance of the CTK assay was evaluated on the basis of various mAb-based interaction systems and assay formats, and it was shown that the assay can provide accurate and repeatable results for immunoreactive concentration and specific activity, with both accuracy and relative SD values below 15%.

Conclusion By applying reverse kinetics on real-time binding traces it is possible to estimate the functional concentration and specific activity of radiolabeled mAb. The CTK assay may in the future be included as a complement to current quality assessment methods of radiolabeled mAbs.

aAlgeta ASA, Oslo, Norway

bBiomedical Radiation Sciences, Uppsala University

cRidgeview Instruments AB, Vänge

dRidgeview Diagnostics AB, Uppsala, Sweden

* Ellen Wang and Hanna Björkelund contributed equally to the writing of this article.

Correspondence to Hanna Björkelund, PhD, Ridgeview Instruments AB, Skillsta 4, SE-740 20 Vänge, Sweden Tel: +46 708 927 856; fax: +46 18 471 3432; e-mail:

Received December 11, 2013

Accepted March 3, 2014

© 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins