title: Preparation, 99mTc-labeling, and in vitro characterization of HYNIC and N3S modified RC-160 and [Tyr3]octreotide.
abstract: The synthesis of conjugates of two somatostatin analogues, RC-160 and [Tyr3]octreotide with different bifunctional chelators for labeling with Tc-99m, is described. Conjugates with hydrazinonicotinamide (HYNIC) and two N3S compounds (benzoyl MAG3 and a N3S adipate derivative) were prepared on a small scale with high purity allowing evaluation of different bifunctional chelators on the same peptide without extensive peptide synthesis. High in vitro stability and retained binding affinity was found for all conjugates except for the N3S adipate. Peptide conjugates could be labeled at high specific activities (>1 Ci/micromol) with 99mTc, and different coligands were explored for the HYNIC conjugates. The resulting radiolabeled complexes were highly stable and showed binding affinity to somatostatin receptors in the nanomolar range. Varying labeling yield, stability, lipophilicity, and isomerism were found for different coligands used for labeling HYNIC conjugates, with lower lipophilicity, higher stability, and fewer coordination isomers for EDDA and tricine/nicotinic acid as ternary coligand compared to tricine. In particular, HYNIC complexes showed promising results for further in vivo evaluation.
authors.affiliation: Nuclear Medicine Research Laboratory, St. Bartholomews hospital, West Smithfield, London EC1 7BE, U.K.
authors.forename: C
authors.initials: C
authors.lastname: Decristoforo
authors.forename: S J
authors.initials: SJ
authors.lastname: Mather
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism; D001667:Binding, Competitive; D002460:Cell Line; D002614:Chelating Agents; D003432:Cross-Linking Reagents; D005998:Glycine / Q000031:analogs & derivatives / Q000737:chemistry; D006801:Humans; D006834:Hydrazines / Q000737:chemistry*; D066298:In Vitro Techniques; D051379:Mice; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000737:chemistry; D015282:Octreotide / Q000737:chemistry* / Q000378:metabolism; D051381:Rats; D017481:Receptors, Somatostatin / Q000378:metabolism; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D013667:Technetium; D014443:Tyrosine / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D002614:Chelating Agents; D003432:Cross-Linking Reagents; D006834:Hydrazines; D017481:Receptors, Somatostatin; C117288:hydrazino nicotinamide; D009536:Niacinamide; C051458:vapreotide; D014443:Tyrosine; D013004:Somatostatin; D013667:Technetium; C111010:S-benzoylmercaptoacetyltriglycine; D015282:Octreotide; D005998:Glycine