LABELING CYCLIC GLYCOPROTEIN IIB IIIA RECEPTOR ANTAGONISTS WITH TC-99M BY THE PREFORMED CHELATE APPROACH - EFFECTS OF CHELATORS ON PROPERTIES OF [TC-99M]CHELATOR-PEPTIDE CONJUGATES/

Several cyclic GPIIb/IIIa receptor antagonists were labeled with Tc-99 m by the preformed chelate approach using chelators such as H(4)L1 [4, 5-bis(mercaptoacetamido)pentanoic acid], H(4)L2 [3,4-bis-(mercaptoacet amido)benzoic acid], H(3)L3 [2-(mercapto)ethylaminoacetyl-L-cysteine], H(4)L4 [N-(mercaptoacetyl)glycylglycylglycine], H(4)L5 [N-[2-(mercapt o)propionyl]glycylglycylglycine], and H(4)L6 mercapto)propionyl]glycyl glycyl-gamma-aminobutyric acid]. In this approach, the [Tc-99m]chelato r complexes are formed first, followed by the activation of the carbox ylic group on the complex by formation of its tetrafluorophenol (TFP) ester and the conjugation of the TFP ester with an amino group of a cy clic GPIIb/IIIa receptor antagonist. The Tc-99m-labeled cyclic GPIIb/I IIa receptor antagonists were characterized by radio-HPLC (high-perfor mance liquid chromatography); differences in lipophilicity of the [Tc- 99m]chelator-peptide conjugate are attributable to the effects of both the cyclic peptide and the chelator.