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

作者：Langford Jonathan H^*; Cooper Margaret S; Orchard Kim H

来源：Nuclear Medicine and Biology, 2011, 38(8): 1103-1110.

DOI：10.1016/j.nucmedbio.2011.05.002

• Ligand to antibody ratio
• Co-57
• Chelate to protein ratio
• Radioimmunotherapy
• Bifunctional chelate/antibody conjugate

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 Co-57 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 Co-57 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 Co-57 binding assay and MALDI-TOF MS results.
Conclusion: A detailed method for the Co-57 ligand to antibody test is described that allows a discrete value to be obtained. The assay was validated as fit for purpose against larger values of coefficient of variation <0.20, accuracy +/- 10%, over a permissive range of 0.5-3.0 ligand to antibody ratio.

• 出版日期2011-11