Synthesis and biodistribution of fluorine-18-labeled fluorocyclofenils for imaging the estrogen receptor.

Abstract	C4-[18F]Fluorocyclofenil ([18F]FCF, 6) and C3-[18F]fluoroethylcyclofenil ([18F]FECF, 9), two high-affinity nonsteroidal estrogens, were prepared and investigated as potential agents for imaging estrogen receptors (ERs) in breast tumors. Both of these compounds could be prepared conveniently from alkyl methanesulfonate precursors (5,8) by fluoride displacement reactions, and they were obtained in high radiochemical purity and radiochemical yields, with effective specific activities sufficient for in vivo biodistribution studies. While the biodistribution of [18F]FCF (6) in immature female rats showed no selective target tissue uptake, the biodistribution of [18F]FECF (9) showed selective uptake by the uterus, but this uptake could not be blocked by excess estradiol. The poor in vivo biodistribution of these otherwise high-affinity ligands arouses curiosity, and together with recent results on the biodistribution of other nonsteroidal ligands suggests that factors other than receptor binding affinity are important for in vivo imaging of estrogen target tissues and ER-positive breast tumors.
Authors	Jai Woong Seo, Dae Yoon Chi, Carmen S Dence, Michael J Welch, John A Katzenellenbogen
Journal	Nuclear medicine and biology (Nucl Med Biol) Vol. 34 Issue 4 Pg. 383-90 (May 2007) ISSN: 0969-8051 [Print] United States
PMID	17499727 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References	C3-fluoroethylcyclofenil C4-fluorocyclofenil Estrogen Receptor alpha Estrogen Receptor beta Fluorine Radioisotopes Indicators and Reagents Mesylates Radiopharmaceuticals Receptors, Estrogen Cyclofenil
Topics	Animals Cyclofenil (analogs & derivatives, chemical synthesis, pharmacokinetics) Estrogen Receptor alpha (metabolism) Estrogen Receptor beta (metabolism) Female Fluorine Radioisotopes Indicators and Reagents Isotope Labeling Mesylates (chemical synthesis, chemistry) Positron-Emission Tomography Radiopharmaceuticals (chemical synthesis, pharmacokinetics) Rats Rats, Sprague-Dawley Receptors, Estrogen (metabolism) Tissue Distribution

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