99mTc-labeling of peptidomimetic antagonist to selectively target αvβ3 receptor-positive tumor: Comparison of PDA and EEDA as co-ligands

In Soo Shin, Jin Soo Maeng, Beom Su Jang, Eric You, Kenneth Cheng, King C.P. Li, Bradford Wood, Jorge A. Carrasquillo, S. Narasimhan Danthi, Chang H. Paik

Research output: Contribution to journalArticle

Abstract

Objectives: The aim of this research was to synthesize radiolabeled peptidomimetic integrin αvβ3 antagonist with 99mTc for rapid targeting of integrin αvβ3 receptors in tumor to produce a high tumor to background ratio. Methods: The amino terminus of 4-[2-(3,4,5,6-tetra-hydropyrimidin-2-ylamino)-ethyloxy]benzoyl-2-(S)-[N-(3-amino--neopenta-1-carbamyl)]-aminoethylsulfonyl-amino-β-alanine hydrochloride (IAC) was conjugated with N-hydroxysuccinimide ester of HYNIC and labeled with 99mTc using tricine with either 1,5-pyridinedicarboxylic acid (PDA) or ethylenediamine-N,N′-diacetic acid (EDDA) as the co-ligand. The products, 99mTcEDDA2/HYNIC-IAC (P1) and 99mTc PDA (tricin)/HYNIC-IAC (P2) were subjected to in vitro serum stability, receptor-binding, biodistribution and imaging studies. Results: P1 and P2 were synthesized with an overall yield of >80%. P1 was slightly more stable than P2 when incubated in serum at 37 oC for 18 hrs (84 vs 77% intact). The In vitro receptor-binding of P1 was higher than that of P2 (78.02 ±13.48 vs 51.05 ± 14.05%) when incubated with αvβ3 at a molar excess (0.8 μM). This receptor binding was completely blocked by a molar excess of an unlabeled peptidomimetic antagonist. Their differences shown in serum stability and the receptor-binding appeared to be related to their biological behaviors in tumor uptake and retention; the 1 h tumor uptakes of P1 and P2 were 3.17±0.52 and 2.13±0.17 % ID/g, respectively. P1 was retained in the tumor longer than P2. P1 was excreted primarily through the renal system whereas P2 complex was excreted equally via both renal and hepatobiliary systems. Thus, P1 was retained in the whole-body with 27.25 ± 3.67% ID at 4 h whereas 54.04 ± 3.57% ID of P2 remained in the whole-body at 4 h. This higher whole-body retention of P2 appeared to be resulted from a higher amount of radioactivity retained in liver and intestine. These findings were supported by imaging studies showing higher tumor-toabdominal contrast for P1 than for P2 at 3 h postinjection. Conclusions: P1 showed good tumor targeting properties with a rapid tumor uptake, prolonged tumor retention and fast whole-body clearance kinetics. These findings warrant further investigation of the HYNIC method of 99mTc labeling of other peptidomimetic antagonists using EDDA as a coligand.

Original languageEnglish (US)
Pages (from-to)1-8
Number of pages8
JournalCurrent Radiopharmaceuticals
Volume3
Issue number1
DOIs
StatePublished - Jul 12 2010
Externally publishedYes

Keywords

  • Antagonist
  • EDDA and PDA as co-ligand
  • Hynic method of Tc-labeling
  • Peptidomimetic αβ
  • Tumor imaging

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Pharmacology

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