Technical Protocol for High-Dose 131I Labeling According to IODO-GEN–Coated MAb Method
| Step | Procedure |
|---|---|
| 1 | Gaseous 131I and 131mXe are removed by suction |
| 2 | 131I solution in delivery vial is adjusted to 1 mL with 1 mmol/L NaOH (activities up to 4.4 GBq [i.e., 600 μL])* |
| 3 | 131I activity is added to wobbling reaction vial† |
| 04 | 10 μL ascorbic acid solution (1.41 mg/mL) are added‡ |
| 5 | After 1 min, 200 μL 1 mol/L phosphate buffer, pH 7.2, are added |
| 6 | 5 mg MAb in 5 mL phosphate buffer, pH 6.8, are added |
| 7 | 35 μL freshly prepared IODO-GEN/MeCN solution (1 mg/mL) are added into reaction mixture (start of reaction, t = 0)§ |
| 8 | At t = 3 min, 100 μL ascorbic acid solution (25 mg/mL, pH 5) are added |
| 9 | At t = 8 min, 50 μL 20% HSA are added |
| 10 | At t = 12 min, reaction mixture is purified (three PD-10 columns; eluent, 0.9% NaCl/ascorbic acid [5 mg/mL], pH 5) |
| 11 | 400 μL 20% HSA are added to 9-mL product vial |
| 12 | Sample is taken under sterile conditions (for determination of radiochemical purity, immunoreactivity, and integrity [HPLC and SDS-PAGE]) |
| 13 | Final product is formulated for clinical use (21-mL infusion volume) |
↵* For activities between 4.4 and 8.8 GBq, delivery vial volume must be adjusted to 2 mL. Labeling should be carried out in reaction volume of 12 mL, in which case all following chemical quantities must be multiplied by factor of 2.
↵† 4.4 GBq (120 mCi) 131I is equivalent to 54.6 nmol I (7.4 nmol 131I and 47.2 nmol 127I).
↵‡ 14.1 μg (80 nmol) ascorbic acid can reduce 26.7 nmol IO3− (i.e. when roughly half of 4.4-GBq 131I batch would be present as IO3−). Theoretically (no aging), 80 nmol ascorbic acid can reduce 20 nmol (8.7 μg) IODO-GEN.
↵§ 35 μg (80 nmol) IODO-GEN corresponds to 320 nmol N-Cl groups.
t = time.