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Development and validation of the 57Co assay for determining the ligand to antibody ratio in bifunctional chelate/antibody conjugates for use in radioimmunotherapy

Record type: Article

Introduction
The ligand to antibody ratio is an important characteristic of a chelate/antibody conjugate. It has been widely reported that if the ratio is too high, there will be detrimental effects on immunoreactivity and biodistribution; conversely, if the ratio is too low, the radionuclide may not bind efficiently, and the stability and the specific activity will be reduced. There are little published data on the accuracy or precision of the 57Co assay. The UK Clinical Trials Regulations state that “systems with procedures that assure the quality of every aspect of the trial should be implemented”. The aims of this study were to assess the reliability and accuracy of the 57Co binding assay and validate it against defined criteria.

Method
Thirty-two serial assays were assessed for reliability. Two batches of conjugated antibody were also analysed by matrix-assisted laser desorption/ionisation time of flight (MALDI-TOF) mass spectrometry (MS) to allow the comparison of the functional test with a physical method.

Results
Reliability: The coefficient of variation was 0.13. Accuracy: There was 9% variation between the 57Co binding assay and MALDI-TOF MS results.

Conclusion
A detailed method for the 57Co ligand to antibody test is described that allows a discrete value to be obtained. The assay was validated as fit for purpose against target values of coefficient of variation <0.20, accuracy±10%, over a permissive range of 0.5–3.0 ligand to antibody ratio.

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Citation

Langford, Jonathan H., Cooper, Margaret S. and Orchard, Kim H. (2011) Development and validation of the 57Co assay for determining the ligand to antibody ratio in bifunctional chelate/antibody conjugates for use in radioimmunotherapy Nuclear Medicine and Biology, 38, (8), pp. 1103-1110. (doi:10.1016/j.nucmedbio.2011.05.002).

More information

Published date: November 2011
Organisations: Cancer Sciences

Identifiers

Local EPrints ID: 341424
URI: http://eprints.soton.ac.uk/id/eprint/341424
ISSN: 0969-8051
PURE UUID: 8b662b89-a87f-4974-9b17-5ccf166f85f2
ORCID for Kim H. Orchard: ORCID iD orcid.org/0000-0003-2276-3925

Catalogue record

Date deposited: 25 Jul 2012 11:12
Last modified: 18 Jul 2017 05:36

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Contributors

Author: Jonathan H. Langford
Author: Margaret S. Cooper
Author: Kim H. Orchard ORCID iD

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