Preparation of the iodine-124 derivative of the Bolton-Hunter reagent ([<sup>124</sup>I]I-SHPP) and its use for labelling a VEGF antibody as a PET tracer
Glaser M., Carroll VA., Collingridge DR., Aboagye EO., Price P., Bicknell R., Harris AL., Luthra SK., Brady F.
This study describes the radioiodination of an antibody specific to the vascular endothelial growth factor (VEGF), VG76e, with [ 124 I]iodine to obtain a novel PET tracer for measurement of angiogenesis. In vitro binding assays showed a significantly higher immunoreactive fraction with the protein labelling reagent N-succinimidyl 3-(4-hydroxy-5-[ 125 I]iodophenyl) propionate ([ 125 I]Bolton-Hunter reagent, [ 125 I]I-SHPP) (34.0 ± 4.0%) as compared with N-succinimidyl 3-[ 125 I]iodobenzoate (10.9 ± 6.4%) or direct radioiodination using [ 125 I]iodide and IodoGen (3.1 ± 3.0%). Consequently, the cyclotron-produced positron-emitting [ 124 I]iodine (T 1/2 = 4.2 days) was employed to prepare [ 124 I]I-SHPP. Using an improved radioiodination methodology, [ 124 I]I-SHPP was prepared from sodium [ 124 I] iodide with IodoGen at pH 6.5. The [ 124 I]Bolton-Hunter reagent was isolated with 25-58% ( n = 3) radiochemical yield and 88-95% (n = 3) radiochemical purity by the conventional extraction procedure. The conjugate of VG76e with [ 124 I]I-SHPP was prepared with 17-18% (n=3) labelling efficiency and 98% radiochemical purity. The immunoreactive fraction was determined to be 33.5% (n = 2). Copyright © 2002 John Wiley & Sons, Ltd.