Improved in Vivo Stability of Radioiodinated Rituximab Using an Iodination Linker for Radioimmunotherapy

Eun Jung Kim, Byoung Soo Kim, Dan Bee Choi, Sung Gil Chi, Tae Hyun Choi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Purpose: Directly radioiodinated [131I]-rituximab has been developed as a radioimmunotherapeutic agent in patients with CD20-positive B cell non-Hodgkin's lymphoma. However, there are concerns over its in vivo catabolism and deiodination. A novel radioiodination linker, N-(4-isothiocyanatobenzyl)-2-(3-(tributylstannyl)phenyl) acetamide (IBPA), was synthesized for the preparation of stable radioiodinated proteins. Methods: The authors evaluated the potential of IBPA as a stable radioiodinated linker for rituximab. [125I]-IBPA was purified and conjugated with rituximab, and in vitro stability testing was performed in serum and liver microsomes. In vivo studies were performed after i.v. injection of [125I]-rituximab or [125I]-IBPA-rituximab to nude mice. Results: In in vitro studies, [125I]-IBPA-rituximab was stable in serum and liver microsomes. In static scans, high radioactivity was evident in the thyroid following injection of [125I]-rituximab, but low radioactivity was seen in the thyroid following injection of [125I]-IBPA-rituximab. In biodistribution studies, radioactivity uptake in thyroid glands of [125I]-IBPA-rituximab was decreased by approximately sevenfold compared to [125I]-rituximab. In pharmacokinetics, the half-life of [125I]-rituximab was shorter than that of [125I]-IBPA-rituximab in plasma of nude mice. Conclusions: The authors demonstrate that [125I]-IBPA-rituximab is more stable to metabolic deiodination in vivo than is [125I]-rituximab. Radioiodination of rituximab using IBPA is thus preferable to direct labeling in terms of in vivo stability.

Original languageEnglish
Pages (from-to)287-294
Number of pages8
JournalCancer Biotherapy and Radiopharmaceuticals
Issue number8
Publication statusPublished - 2016 Oct 1

Bibliographical note

Publisher Copyright:
© 2016 Mary Ann Liebert, Inc.


  • CD20
  • N-(4-isothiocyanatobenzyl)-2-(3-(tributylstannyl)phenyl) acetamide (IBPA)
  • deiodination
  • lymphoma
  • radioimmunotherapy
  • rituximab

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Pharmacology
  • Cancer Research


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