The ultimate radiochemical nightmare: upon radio-iodination of Botulinum neurotoxin A, the introduced iodine atom itself seems to be fatal for the bioactivity of this macromolecule

EJNMMI Research

Table 2 Results of iodination of cetuximab with increasing amount of ¹²⁵ I

Cetuximab (μg)	¹²⁵ I (MBq)	Labelling efficiency (%)	Radiochemical purity (%)	Immunoreactivity (%)	¹²⁵ I/mAb molar ratio ^a
50	15.0	71.4	99.1	95.2	0.40
50	48.4	75.2	99.7	ND	1.36
50	73.1	81.9	99.3	96.9	2.29
50	112.2	72.9	99.8	ND	3.05
50	150.0	77.0	99.4	96.8	4.30

Conditions: 2.5 μg IODOGEN, 250 μL reaction volume and 90-s reaction time. ND = not determined.
^a100 MBq ¹²⁵I corresponds with 1.24 nmol I atoms.