Evaluation of [11C]laniquidar as a tracer of P-glycoprotein: radiosynthesis and biodistribution in rats.
At present, P-glycoprotein (P-gp) function can be studied using positron emission tomography (PET) together with a labelled P-gp substrate such as R-[11C]verapamil. Such a tracer is, however, less suitable for investigating P-gp (over)expression. Laniquidar is a third-generation P-gp inhibitor, which has been used in clinic trials for modulating multidrug resistance transporters. The purpose of the present study was to develop the radiosynthesis of [11C]laniquidar and to assess its suitability as a tracer of P-gp expression. The radiosynthesis of [11C]laniquidar was performed by methylation of the carboxylic acid precursor with [11C]CH3I. The product was purified by HPLC and reformulated over a tC18 Seppak, yielding a sterile solution of [11C]laniquidar in saline. For evaluating [11C]laniquidar, rats were injected with 20 MBq [11C]laniquidar via a tail vein and sacrificed at 5, 15, 30 and 60 min after injection. Several tissues and distinct brain regions were dissected and counted for radioactivity. In addition, uptake of [11C]laniquidar in rats pretreated with cyclosporine A and valspodar (PSC 833) was determined at 30 min after injection. Finally, the metabolic profile of [11C]laniquidar in plasma was determined. [11C]Laniquidar could be synthesized in moderate yields with high specific activity. Uptake in brain was low, but significantly increased after administration of cyclosporine A. Valspodar did not have any effect on cerebral uptake of [11C]laniquidar. In vivo rate of metabolism was relatively low. Further kinetic studies are needed to investigate the antagonistic behaviour of [11C]laniquidar at tracer level.
Luurtsema
Gert
G
Department of Nuclear Medicine and PET Research, VU University Medical Centre, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. g.luurtsema@vumc.nl
Schuit
Robert C
RC
Klok
Rob P
RP
Verbeek
Joost
J
Leysen
Josée E
JE
Lammertsma
Adriaan A
AA
Windhorst
Albert D
AD
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001552:Benzazepines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics*; D001667:Binding, Competitive; D002250:Carbon Radioisotopes / Q000737:chemistry; D016572:Cyclosporine / Q000494:pharmacology; D003524:Cyclosporins / Q000494:pharmacology; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics*; D011849:Radioactive Tracers; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D001552:Benzazepines; D002250:Carbon Radioisotopes; D003524:Cyclosporins; D011804:Quinolines; D011849:Radioactive Tracers; D016572:Cyclosporine; C411474:laniquidar; C070272:valspodar