Radiohalogenation of Monoclonal Antibodies: Experiences with Radioiodination of Monoclonal Antibodies for Radioimmunotherapy

At the National Institutes of Health, an apparatus was developed to radiolabel monoclonal antibodies for use in both imaging and radioimmuno-therapy. Up to 600 mCi of I-131 can be safely handled in this labeling hood which is shown schematically in Figure 1. The hood was designed so that two iodinations could be performed at the same time. Often these include specific and nonspecific (isotype matched) antibodies. To construct the apparatus, a standard fume hood was reinforced with steel and a steel frame was assembled inside the hood to support standard two inch lead bricks. The frame itself has two doors of steel encased lead. The entire apparatus is covered by a plexiglass safety box which has on its upper surface four fan and charcoal filter units to trap volatilized radioiodine. The internal components of the apparatus include a reaction vessel, a Sephadex gel filtration chromatography column, a gamma detector, product and waste vials, tubing and three-way stopcocks connecting these items, and a peristaltic pump. Small bore arterial pressure tubing (internal volume of 0.55 ml per 12 inch segment) with luer lock fittings connect the reaction vial to the column and the column to the product and waste vials. The reaction vial sits in a lead pig on top of a flat vortex mixer whose speed is controlled by a variable voltage supply. The peristaltic pump in the system is capable of driving fluid through the relatively rigid arterial pressure tubing at a rate of 1 ml per minute.