Optimal quality (131)I-monoclonal antibodies on high-dose labeling in a large reaction volume and temporarily coating the antibody with IODO-GEN.

Abstract

UNLABELLED:

A novel, facile procedure for efficient coupling of high doses of (131)I to monoclonal antibodies (MAbs) was developed with minimal chemical and radiation damage.

METHODS:

To diminish the radiation and chemical burden during labeling, iodination was performed in a large reaction volume and by temporarily coating the MAb with a minimal amount of IODO-GEN. The MAb was coated by injection of IODO-GEN (dissolved in acetonitrile [MeCN]) into the aqueous MAb solution, and the coating was subsequently removed by addition of ascorbic acid. For chemoprotection before, during, and after PD-10 purification of the (131)I-MAbs, ascorbic acid and human serum albumin were used. The effects of autoradiolysis in the starting (131)I solution were countered by treatment with NaOH and ascorbic acid. For this so-called IODO-GEN-coated MAb method, the sensitive chimeric MAb MOv18 (c-MOv18) and the more robust murine MAbs K928 and E48 were used. The high-dose (131)I-labeled MAbs were characterized for radiochemical purity and MAb integrity by thin-layer chromatography, high-performance liquid chromatography, and sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by phosphor imager quantification. The high-dose (131)I-labeled MAbs were also characterized for immunoreactivity. The radiopharmacokinetics and biodistribution of (131)I-c-MOv18 were analyzed in human tumor-bearing nude mice. For comparison, (131)I-c-MOv18 batches were made using the conventional chloramine-T or IODO-GEN-coated vial method.

RESULTS:

Conventional high-dose labeling of 5 mg c-MOv18 with 4.4 GBq (131)I resulted in a labeling yield of 60%, a radiochemical purity of 90%, an immunoreactive fraction of 25% (72% being the maximum in the assay used), and the presence of aggregation and degradation products. Using similar amounts of (131)I and MAb in the IODO-GEN-coated MAb method, 85%-89% overall radiochemical yield, at least 99.7% radiochemical purity, and full preservation of MAb integrity and immunoreactivity were achieved. For this labeling, 5 mg MAb were coated with 35 microg IODO-GEN during 3 min in a reaction volume of 6 mL. Also, biodistribution was optimal, and tumor accumulation was superior to that of coinjected (125)I-c-MOv18 labeled according to the conventional IODO-GEN-coated vial method.

CONCLUSION:

A new, facile, high-dose (131)I-labeling method was developed for production of (131)I-labeled MAbs with optimal quality for use in clinical radioimmunotherapy.

• Authors: G W Visser, R P Klok, J W Gebbinck, T ter Linden, G A van Dongen, C F Molthoff
• Journal: Journal of nuclear medicine : official publication, Society of Nuclear Medicine (J Nucl Med) Vol. 42 Issue 3 Pg. 509-19 (Mar 2001) ISSN: 0161-5505 [Print] United States
• PMID: 11337531 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Monoclonal
• Carrier Proteins
• Folate Receptors, GPI-Anchored
• Indicators and Reagents
• Iodine Radioisotopes
• Neoplasm Proteins
• Receptors, Cell Surface
• 1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril
• Urea

Topics

• Animals
• Antibodies, Monoclonal (immunology, pharmacokinetics, therapeutic use)
• Carrier Proteins (immunology)
• Female
• Folate Receptors, GPI-Anchored
• Indicators and Reagents
• Iodine Radioisotopes (pharmacokinetics, therapeutic use)
• Mice
• Mice, Nude
• Neoplasm Proteins (immunology)
• Ovarian Neoplasms (immunology, radiotherapy)
• Radioimmunotherapy
• Receptors, Cell Surface
• Tissue Distribution
• Urea (analogs & derivatives)