Preparation of 111In labeled radiopharmaceuticals using radio-labeling kit developed by the National Cancer Institute (NCI)

Objectives In order to reduce the cost per dose of radiopharmaceuticals and increase the national applicability of molecular imaging, NCI has developed a kit for radionuclide labeling. We are currently evaluating this kit with some clinically important CHX-A” conjugated antibodies.

Methods Three CHX-A” conjugated antibodies (Human IgG, trastuzumab, and cetuximab) were investigated. A general labeling procedure was established after successful radio-labeling of trastuzumab-CHX-A” with 111In. The kit vials were brought to room temperature before use. To the empty reaction vial 300 microliters of sodium acetate buffer (1.2 times the volume of the 111Indium chloride) was transferred and coated the entire inner surface of the reaction vial by gentle rolling. Approximately 6 mCi of 111Indium chloride solution (250 microliters) was mixed in the reaction vial. After 1 mg trastuzumab-CHX-A” (200 microliters + 200 microliters sodium acetate rinse) was added to the reaction vial, the labeling reaction proceeded at room temperature for 30 minutes. The calculated volume of formulation buffer (reach a final volume of 5 mL) was transferred to the reaction vial and gently inverted to avoid foaming.

Results Radiochemical purity was > 96 %. Size exclusion chromatography monitored at 280 nm showed one single coincidental UV/radiation peak with a retention time of 22 minutes. We are currently employing this radio-labeling method to a wide range of CHX-A” chelated antibodies to determine the cross effectiveness of this technique. A detailed labeling procedure along with all quality control testing results will be presented.

Conclusions Our preliminary radiolabeling studies showed that this kit can be used in radiolabeling to produce clinical grade radiopharmaceuticals

Research Support Funded by NCI Contract No. HHSN261200800001E