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Background <p>The αvβ6 integrin has emerged as a valuable target for theranostic applications in nuclear medicine with high applicability across a variety of cancers, including head-and-neck, lung, breast, and pancreatic carcinomas. [⁶⁸Ga]Ga-Trivehexin is a prominent example of a diagnostic tracer targeting this integrin. In this work, we aimed to expand on this concept by developing FSC(PEG4-αvβ6)₃, a novel tracer that retains the Trivehexin design, but features PEGylated spacers and replaces the TRAP chelator with Fusarinine C (FSC), enabling labelling with Zirconium-89 in addition to Gallium-68. Preclinical characterization of [⁶⁸Ga]Ga/[⁸⁹Zr]Zr-FSC(PEG4-αvβ6)₃ included affinity determination towards the αvβ6 integrin and cellular uptake studies in αvβ6-positive H2009 cells. A subcutaneously xenografted H2009 tumor model was used to assess the PET imaging potential and biodistribution at early time points with the Gallium-68 labelled compound, and at later time points (up to 6 days post-injection) with the Zirconium-89 labelled version.</p> Results <p>While [⁶⁸Ga]Ga-FSC(PEG4-αvβ6)₃ exhibited moderate binding to αvβ6, its affinity, cellular internalization, and tumor uptake <i>in vivo</i> were lower compared to [⁶⁸Ga]Ga-Trivehexin. Notably, this decreased target engagement was associated with reduced nonspecific binding, which we primarily attributed to the incorporation of PEGylated linkers. Despite indication of <i>in vivo</i> degradation of [⁸⁹Zr]Zr-FSC(PEG4-αvβ6)₃, still a meaningful evaluation of pharmacokinetics and biodistribution at extended time points was feasible, revealing prolonged tumor persistence up to 6 days post-injection.</p> Conclusions <p>FSC(PEG4-αvβ6)₃ represents the first-generation tracer targeting the αvβ6 integrin based on the multifunctional chelator Fusarinine C, thereby expanding the repertoire of radionuclides applicable from Gallium-68 to Zirconium-89. Following further optimization, this novel class of compounds holds significant promise for enabling clinical translation and advancing the development of next-generation αvβ6-directed imaging agents.</p>

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Synthesis and preclinical development of a novel 68Ga/89Zr-Labelled ανβ6-integrin targeting trimer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月5日

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  • Giacomo Gariglio,
  • Fernando A Patiño Álvarez,
  • Maximilian A Zierke,
  • Stefan Stangl,
  • Tim Rheinfrank,
  • Nadine Holzleitner,
  • Susanne Kossatz,
  • Clemens Decristoforo

摘要

Background

The αvβ6 integrin has emerged as a valuable target for theranostic applications in nuclear medicine with high applicability across a variety of cancers, including head-and-neck, lung, breast, and pancreatic carcinomas. [⁶⁸Ga]Ga-Trivehexin is a prominent example of a diagnostic tracer targeting this integrin. In this work, we aimed to expand on this concept by developing FSC(PEG4-αvβ6)₃, a novel tracer that retains the Trivehexin design, but features PEGylated spacers and replaces the TRAP chelator with Fusarinine C (FSC), enabling labelling with Zirconium-89 in addition to Gallium-68. Preclinical characterization of [⁶⁸Ga]Ga/[⁸⁹Zr]Zr-FSC(PEG4-αvβ6)₃ included affinity determination towards the αvβ6 integrin and cellular uptake studies in αvβ6-positive H2009 cells. A subcutaneously xenografted H2009 tumor model was used to assess the PET imaging potential and biodistribution at early time points with the Gallium-68 labelled compound, and at later time points (up to 6 days post-injection) with the Zirconium-89 labelled version.

Results

While [⁶⁸Ga]Ga-FSC(PEG4-αvβ6)₃ exhibited moderate binding to αvβ6, its affinity, cellular internalization, and tumor uptake in vivo were lower compared to [⁶⁸Ga]Ga-Trivehexin. Notably, this decreased target engagement was associated with reduced nonspecific binding, which we primarily attributed to the incorporation of PEGylated linkers. Despite indication of in vivo degradation of [⁸⁹Zr]Zr-FSC(PEG4-αvβ6)₃, still a meaningful evaluation of pharmacokinetics and biodistribution at extended time points was feasible, revealing prolonged tumor persistence up to 6 days post-injection.

Conclusions

FSC(PEG4-αvβ6)₃ represents the first-generation tracer targeting the αvβ6 integrin based on the multifunctional chelator Fusarinine C, thereby expanding the repertoire of radionuclides applicable from Gallium-68 to Zirconium-89. Following further optimization, this novel class of compounds holds significant promise for enabling clinical translation and advancing the development of next-generation αvβ6-directed imaging agents.