A new high affinity technetium analogue of bombesin containing DTPA as a pharmacokinetic modifier

Kuo Shyan Lin, Andrew Luu, Kwamena E. Baidoo, Hossein Hashemzadeh-Gargari, Ming Kai Chen, Roberto Pili, Martin Pomper, Michael Carducci, Henry N. Wagner

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Abstract

The bombesin (BN)/gastrin-releasing peptide (GRP) receptor is expressed in high density on the cell surface of a variety of tumors. This makes the receptors accessible as a molecular target for the detection of lesions in which they are expressed. In this study, we describe a high affinity hydrophilic 99mTc-labeled BN analogue, [DTPA1, Lys3( 99mTc-Hx-DADT), Tyr4]BN, having diethylenetriaminepentaacetic acid (DTPA), as a build-in pharmacokinetic modifier, to direct its excretion through the urinary system in order to lower abdominal background activity. In vitro binding studies using [ 125I-TyT4] BN (Kd, 0.1 nM) and human prostate cancer PC-3 cell membranes showed that the inhibition constant (Ki) of [DTPA1, Lys3(99Tc-Hx-DADT), Tyr 4]BN was 19.9 ± 8.0 nM. Biodistribution studies in normal mice showed fast blood clearance (0.15 ± 0.01% ID/g, 4 h postinjection), low intestinal accumulation (9.16 ± 2.35% ID/g, 4 h postinjection), and significant uptake in BN/GRP receptor rich tissues such as the pancreas (21.83 ± 2.88% ID/g, 15 min postinjection). The pancreas/blood, pancreas/muscle, and pancreas/liver ratios were highest at 2 h postinjection at 23, 74, and 8.4, respectively. The uptake in the pancreas could be blocked by BN (11.96 ± 1.17 vs 0.65 ± 0.16% ID/g), partially blocked by neuromedin B (11.96 ± 1.17 vs 6.66 ± 0.51% ID/g), but not affected by somatostatin (11.96 ± 1.17 vs 12.91 ± 2.53% ID/g), indicating that the binding of [DTPA1, Lys3(99mTc-Hx-DADT), Tyr 4]BN to the receptors was specific. Scintigraphic imaging of human PC-3 prostate cancer xenografts in SCID mice gave a high target to nontarget ratio on the image. Thus, [DTPA1, Lys3( 99mTc-Hx-DADT), Tyr4]BN has the potential for imaging BN/GRP receptor-positive lesions.

Original languageEnglish (US)
Pages (from-to)1416-1423
Number of pages8
JournalBioconjugate Chemistry
Volume15
Issue number6
DOIs
StatePublished - Nov 1 2004

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ASJC Scopus subject areas

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

Cite this

Lin, K. S., Luu, A., Baidoo, K. E., Hashemzadeh-Gargari, H., Chen, M. K., Pili, R., Pomper, M., Carducci, M., & Wagner, H. N. (2004). A new high affinity technetium analogue of bombesin containing DTPA as a pharmacokinetic modifier. Bioconjugate Chemistry, 15(6), 1416-1423. https://doi.org/10.1021/bc0498267