Toxicol Res.  2013 Mar;29(1):21-25.

Biodistribution of 99mTc Labeled Integrin Antagonist

  • 1RI-Biomics Research & Development Team, Korea Atomic Energy Research Institute, Jeonbuk, Korea.
  • 2Division of Biologics Research, Korea Food and Drug Administration, Osong, Chungbuk, Korea.
  • 3Bio-nanotechnology Research Center, Korea Food Research Institute, Sungnam, Korea.
  • 4Nuclear Medicine Department and Radiology Department, Warren G. Magnuson Clinical Center, NIH, Bethesda, MD 20892, USA.


The selective targeting of an integrin alphavbeta3 receptor using radioligands may enable the assessment of angiogenesis and integrin alphavbeta3 receptor status in tumors. The aim of this research was to label a peptidomimetic integrin alphavbeta3 antagonist (PIA) with 99mTc(CO)3 and to test its receptor targeting properties in nude mice bearing receptor-positive tumors. PIA was reacted with tris-succinimidyl aminotriacetate (TSAT) (20 mM) as a PIA per TSAT. The product, PIA-aminodiacetic acid (ADA), was radiolabeled with [99mTc(CO)3(H2O)3](+1), and purified sequentially on a Sep-Pak C-18 cartridge followed by a Sep-Pak QMA anion exchange cartridge. Using gradient C-18 reverse-phase HPLC, the radiochemical purity of 99mTc(CO)3-ADA-PIA (retention time, 10.5 min) was confirmed to be > 95%. Biodistribution analysis was performed in nude mice (n = 5 per time point) bearing receptor-positive M21 human melanoma xenografts. The mice were administered 99mTc(CO)3-ADA-PIA intravenously. The animals were euthanized at 0.33, 1, and 2 hr after injection for the biodistribution study. A separate group of mice were also co-injected with 200 microg of PIA and euthanized at 1 hr to quantify tumor uptake. 99mTc(CO)3-ADA-PIA was stable in phosphate buffer for 21 hr, but at 3 and 6 hr, 7.9 and 11.5% of the radioactivity was lost as histidine, respectively. In tumor bearing mice, 99mTc(CO)3-ADA-PIA accumulated rapidly in a receptor-positive tumor with a peak uptake at 20 min, and rapid clearance from blood occurring primarily through the hepatobiliary system. At 20 min, the tumor-to-blood ratio was 1.8. At 1 hr, the tumor uptake was 0.47% injected dose (ID)/g, but decreased to 0.12% ID/g when co-injected with an excess amount of PIA, indicating that accumulation was receptor mediated. These results demonstrate successful 99mTc labeling of a peptidomimetic integrin antagonist that accumulated in a tumor via receptor-specific binding. However, tumor uptake was very low because of low blood concentrations that likely resulted from rapid uptake of the agent into the hepatobiliary system. This study suggests that for 99mTc(CO)3-ADA-PIA to be useful as a tumor detection agent, it will be necessary to improve receptor binding affinity and increase the hydrophilicity of the product to minimize rapid hepatobiliary uptake.


Peptidomimetic integrin alphavbeta3 antagonist; 99mTc tricarbonyl precursor; Biodistribution

MeSH Terms

Chromatography, High Pressure Liquid
Hydrophobic and Hydrophilic Interactions
Integrin alphaVbeta3
Mice, Nude
Transplantation, Heterologous
Integrin alphaVbeta3
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