Related Experiment Video
Updated: Jun 6, 2025
Preparing a 68Ga-labeled Arginine Glycine Aspartate RGD-peptide for Angiogenesis
Published on: January 7, 2019
Three Is a Magic Number: Tailored Clickable Chelators Used to Determine Optimal RGD-Peptide Multiplicity in
Tim Rheinfrank1, Viktor Lebruška2, Stefan Stangl1
1Department of Nuclear Medicine, TUM University Hospital and Central Institute for Translational Cancer Research, (TranslaTUM), School of Medicine, Technical University Munich, 81675 Munich, Germany.
Abstract:
The cellular adhesion receptor αvβ6-integrin is highly expressed in many cancers, e.g., pancreatic, lung, head-and-neck, cervical, bladder, and esophageal carcinoma. Multimerization of αvβ6-integrin-specific RGD peptides increases the target affinity and retention but affects biodistribution and pharmacokinetics. Amide formation of the terminal carboxylic acid moieties of the square-symmetrical bifunctional chelator DOTPI with 3-azidopropylamine yields derivatives with 4, 3, and 2 terminal azides and zero, 1, and 2 remaining carboxylic acids, respectively, whereby formation of the 2-cis-isomer is preferred according to NMR investigation of the Eu(III)-complexes. Cu(II)-catalyzed alkyne-azide cycloaddition (CuAAC) of the alkyne-functionalized αvβ6-integrin binding peptide cyclo[YRGDLAYp(NMe)K(pent-4-ynoic amide)] (Tyr2) yields the respective di-, tri-, and tetrameric conjugates for Lu-177-labeling. In mice bearing αvβ6-integrin-expressing xenografts of H2009 (human lung adenocarcinoma) cells, the Lu-177-labeled trimer's tumor-to-blood ratio of 112 exceeds that of the tetramer (10.4) and the dimer (54). Co-infusion of gelofusine (succinylated gelatin) reduces the renal uptake of the trimer by 89%, resulting in a 10-fold better tumor-to-kidney ratio, while no improvement of that ratio is observed with arginine/lysine, para-aminohippuric acid (PAH), and hydroxyethyl starch (HES) coinfusions. Since the Lu-177-labeled Tyr2-trimer outperforms the dimer and the tetramer, such trimers are considered the best lead structures for the ongoing development of αvβ6-integrin targeted anticancer theranostics.
Insights
Multimerized peptides targeting alpha-v-beta-6 integrin show promise for cancer theranostics. The Lu-177 labeled trimer demonstrated superior tumor targeting and reduced kidney uptake, making it a lead candidate for development.
Area of Science:
- Oncology
- Radiochemistry
- Bioconjugation Chemistry
Background:
- Alpha-v-beta-6 integrin (αvβ6) is a cellular adhesion receptor overexpressed in various carcinomas, including lung, pancreatic, and head-and-neck cancers.
- Multimerization of αvβ6-specific peptides enhances target affinity and retention but can negatively impact biodistribution and pharmacokinetics.
- Development of targeted radiopharmaceuticals requires optimization of peptide conjugates for effective delivery and reduced off-target accumulation.
Purpose of the Study:
- To synthesize and evaluate multimeric αvβ6-integrin-targeting peptide conjugates for potential use in cancer theranostics.
- To investigate the impact of different multimerization states (dimer, trimer, tetramer) on targeting efficacy and biodistribution.
- To assess the utility of coinfusion agents in mitigating off-target uptake, particularly in the kidneys.
Main Methods:
- Synthesis of alkyne-functionalized αvβ6-binding peptide (Tyr2) and its conjugation with a bifunctional chelator (DOTPI) to create dimeric, trimeric, and tetrameric constructs via copper-catalyzed alkyne-azide cycloaddition (CuAAC).
- Labeling of the peptide conjugates with Lutetium-177 (Lu-177).
- In vivo evaluation in mice bearing αvβ6-integrin-expressing human lung adenocarcinoma xenografts, assessing tumor uptake, biodistribution, and the effect of coinfusion agents like gelofusine.
Main Results:
- The Lu-177-labeled Tyr2-trimer exhibited a significantly higher tumor-to-blood ratio (112) compared to the tetramer (10.4) and dimer (54).
- Co-infusion with gelofusine reduced the trimer's renal uptake by 89%, improving the tumor-to-kidney ratio tenfold.
- Other coinfusion agents (arginine/lysine, PAH, HES) did not show comparable improvements in the tumor-to-kidney ratio.
Conclusions:
- The Lu-177-labeled Tyr2-trimer demonstrates superior tumor targeting and favorable biodistribution compared to its dimer and tetramer counterparts.
- Gelofusine coinfusion is an effective strategy to reduce renal accumulation of the trimer conjugate, enhancing its therapeutic potential.
- The Tyr2-trimer represents a promising lead structure for developing αvβ6-integrin-targeted theranostic agents for cancer treatment.
