title: Comparative in vivo behavior studies of cyclen-based copper-64 complexes: regioselective synthesis, X-ray structure, radiochemistry, log P, and biodistribution.
abstract: The in vivo behavior of copper(II)-cyclen complexes was modified via substitution of the parent ligand with two different substituents, 4-tert-butylbenzyl and acetate. This was achieved by using same synthetic strategy (regioselective protection/first alkylation/deprotection/second alkylation) to give nine cyclen derivatives. The X-ray structure of [Cu(2c)Cl]+ (2c = 1-(4-tert-butylbenzyl)-1,4,7,10-tetraazacyclododecane) showed that the chlorine ion from the reaction mixture occupied the remaining apical position of a square pyramidal coordination environment of these Cu-cyclen complexes. Eight out of nine compounds were labeled with 64Cu in high radiochemical purity. log P measurements showed that the lipophilicities of the copper complexes were increased dramatically by attaching hydrophobic substituents on the nitrogen atoms of cyclen. Conversely, as the number of acetate groups increased, the lipophilicity was decreased. The biodistribution of Cu-cyclen complexes was found to be influenced mostly by the overall charge of the complexes rather than their lipophilicity. Positively charged (+2) complexes showed high blood retention at early time points with sluggish clearance from liver by 24 h. The attachment of even one acetate group onto cyclen accelerated blood and liver clearance dramatically compared to +2 charged Cu(II) complexes. Neutral trans-substituted Cu-4 showed the best clearance and lowest retention of doses from all organs most time, followed by -1 charged complex Cu-2. Trans-substituted complexes structure isomers Cu-3 and Cu-4 showed better clearance and lower retention from all organs than their cis-counterparts Cu-5 and Cu-6.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, Campus Box 8225, 510 South Kingshighway Boulevard, St. Louis, Missouri 63110, USA.
authors.forename: Jeongsoo
authors.initials: J
authors.lastname: Yoo
authors.forename: David E
authors.initials: DE
authors.lastname: Reichert
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Welch
mesh_terms: D000818:Animals; D003301:Copper Radioisotopes; D018360:Crystallography, X-Ray; D000080027:Cyclams; D005260:Female; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014018:Tissue Distribution
chemical_list: D003301:Copper Radioisotopes; D000080027:Cyclams; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; C038072:cyclen