Kit formulation for 99mTc-labeling of recombinant anti-HER2 Affibody molecules with a C-terminally engineered cysteine
Received 10 December 2009; received in revised form 7 February 2010; accepted 23 February 2010. published online 09 April 2010.
Abstract
Introduction
Molecular imaging of human epidermal growth factor receptor type 2 (HER2)-expression in malignant tumors provides potentially important information for patient management. Affibody molecules have shown to be suitable tracers for imaging applications using single photon emission computed tomography or positron emission tomography. Results from an earlier evaluation of the application of site-specific 99mTc-labeling of the Affibody molecule, ZHER2:2395-C, were favorable.
Methods
As a preparation for clinical application of this tracer, we have developed and evaluated a robust single-vial freeze-dried kit, allowing labeling of the Affibody molecule, ZHER2:2395-C, with 99mTc.
Results
The composition of the kit [containing glucoheptonate, EDTA and tin(II)-chloride], as well as the protein amount and the pertechnetate volume were optimized for a high labeling yield (>90%) and minimal presence of reduced hydrolyzed technetium colloids (<1%). The specificity to HER2 receptors, the binding competence and the stability in phosphate-buffered saline and murine serum were verified in vitro. The shelf-life was also evaluated in vitro, showing no reduction in labeling yield or binding capacity to HER2-expressing cells after over 400 days of storage of the single-vial freeze-dried kit.
Conclusions
ZHER2:2395-C labeled with 99mTc using the lyophilized kit was stable and resulted in a favorable biodistribution in an in vivo evaluation in normal Naval Medical Research Institute mice.
aDivision of Nuclear Medicine, Department of Medical Sciences, Uppsala University, SE-751 85, Uppsala, Sweden
bDivision of Biomedical Radiation Sciences, Department of Oncology, Radiology and Clinical Immunology, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
ABSTRACT