Enhancing PET Signal at Target Tissue in Vivo: Dendritic and Multimeric Tris(hydroxypyridinone) Conjugates for Molecular Imaging of αvβ3 Integrin Expression with Gallium-68

Bioconjug Chem. 2017 Feb 15;28(2):481-495. doi: 10.1021/acs.bioconjchem.6b00621. Epub 2016 Dec 14.

Abstract

Tris(hydroxypyridinone) chelators conjugated to peptides can rapidly complex the positron-emitting isotope gallium-68 (68Ga) under mild conditions, and the resulting radiotracers can delineate peptide receptor expression at sites of diseased tissue in vivo. We have synthesized a dendritic bifunctional chelator containing nine 1,6-dimethyl-3-hydroxypyridin-4-one groups (SCN-HP9) that can coordinate up to three Ga3+ ions. This derivative has been conjugated to a trimeric peptide (RGD3) containing three peptide groups that target the αvβ3 integrin receptor. The resulting dendritic compound, HP9-RGD3, can be radiolabeled in 97% radiochemical yield at a 3-fold higher specific activity than its homologues HP3-RGD and HP3-RGD3 that contain only a single metal binding site. PET scanning and biodistribution studies show that [68Ga(HP9-RGD3)] demonstrates higher receptor-mediated tumor uptake in animals bearing U87MG tumors that overexpress αvβ3 integrin than [68Ga(HP3-RGD)] and [68Ga(HP3-RGD3)]. However, concomitant nontarget organ retention of [68Ga(HP9-RGD3)] results in low tumor to nontarget organ contrast in PET images. On the other hand, the trimeric peptide homologue containing a single tris(hydroxypyridinone) chelator, [68Ga(HP3-RGD3)], clears nontarget organs and exhibits receptor-mediated uptake in mice bearing tumors and in mice with induced rheumatoid arthritis. PET imaging with [68Ga(HP3-RGD3)] enables clear delineation of αvβ3 integrin receptor expression in vivo.

MeSH terms

  • Animals
  • Arthritis, Rheumatoid / diagnostic imaging
  • Chelating Agents / chemistry*
  • Chelating Agents / pharmacokinetics
  • Female
  • Gallium Radioisotopes / chemistry*
  • Gallium Radioisotopes / pharmacokinetics
  • Integrin alphaVbeta3 / analysis*
  • Joints / diagnostic imaging
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Neoplasms / diagnostic imaging
  • Oligopeptides / chemistry*
  • Oligopeptides / pharmacokinetics
  • Positron-Emission Tomography / methods*
  • Pyridines / chemistry*
  • Pyridines / pharmacokinetics
  • Tissue Distribution

Substances

  • 3-hydroxypyridin-4-one
  • Chelating Agents
  • Gallium Radioisotopes
  • Integrin alphaVbeta3
  • Oligopeptides
  • Pyridines
  • arginyl-glycyl-aspartic acid