Evaluation of a maleimido derivative of CHX-A″ DTPA for site-specific labeling of affibody molecules

Vladimir Tolmachev, Heng Xu, Helena Wållberg, Sara Ahlgren, Magnus Hjertman, Anna Sjöberg, Mattias Sandström, Lars Abrahmsén, Martin W. Brechbiel, Anna Orlova

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)

Abstract

Affibody molecules are a new class of small targeting proteins based on a common three-helix bundle structure. Affibody molecules binding a desired target may be selected using phage-display technology. An Affibody molecule Z HER2:342 binding with subnanomolar affinity to the tumor antigen HER2 has recently been developed for radionuclide imaging in vivo. Introduction of a single cysteine into the cysteine-free Affibody scaffold provides a unique thiol group for site-specific labeling of recombinant Affibody molecules. The recently developed maleimido-CHX-A″ DTPA was site-specifically conjugated at the C-terminal cysteine of ZHER2:2395-C, a variant of Z HER2:342, providing a homogeneous conjugate with a dissociation constant of 56 pM. The yield of labeling with 111In was >99% after 10 min at room temperature. In vitro cell tests demonstrated specific binding of 111In-CHX-A″ DTPA-Z2395-C to HER2-expressing cell-line SKOV-3 and good cellular retention of radioactivity. In normal mice, the conjugate demonstrated rapid clearance from all nonspecific organs except kidney. In mice bearing SKOV-3 xenografts, the tumor uptake of 111In-CHX-A″ DTPA-Z2395-C was 17.3 ± 4.8% IA/g and the tumor-to-blood ratio 86 ± 46 (4 h postinjection). HER2-expressing xenografts were clearly visualized 1 h postinjection. In conclusion, coupling of maleimido-CHX-A″ DTPA to cysteine-containing Affibody molecules provides a well-defined uniform conjugate, which can be rapidly labeled at room temperature and provides high-contrast imaging of molecular targets in vivo.

Original languageEnglish
Pages (from-to)1579-1587
Number of pages9
JournalBioconjugate Chemistry
Volume19
Issue number8
DOIs
Publication statusPublished - Aug 2008
Externally publishedYes

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Biomedical Engineering
  • Pharmacology
  • Pharmaceutical Science
  • Organic Chemistry

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