Radiosynthesis and in vivo evaluation of 1-[18F]fluoroelacridar as a positron emission tomography tracer for P-glycoprotein and breast cancer resistance protein
作者:Bernd Dörner、Claudia Kuntner、Jens P. Bankstahl、Thomas Wanek、Marion Bankstahl、Johann Stanek、Julia Müllauer、Florian Bauer、Severin Mairinger、Wolfgang Löscher、Donald W. Miller、Peter Chiba、Markus Müller、Thomas Erker、Oliver Langer
DOI:10.1016/j.bmc.2011.02.039
日期:2011.4
Aim of this study was to label the potent dual P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) inhibitor elacridar (1) with F-18 to provide a positron emission tomography (PET) radiotracer to visualize Pgp and BCRP. A series of new 1- and 2-halogen- and nitro-substituted derivatives of 1 (4a-e) was synthesized as precursor molecules and reference compounds for radiolabelling and shown to display comparable in vitro potency to 1 in increasing rhodamine 123 accumulation in a cell line overexpressing human Pgp (MDCKII-MDR1). 1-[F-18]fluoroelacridar ([F-18]4b) was synthesized in a decay-corrected radiochemical yield of 1.7 +/- 0.9% by a 1-step no-carrier added nucleophilic aromatic F-18-substitution of 1-nitro precursor 4c. Small-animal PET imaging of [F-18]4b was performed in naive rats, before and after administration of unlabelled 1 (5 mg/kg, n = 3), as well as in wild-type and Mdr1a/b((-/-)) Bcrp1((-/-)) mice (n = 3). In PET experiments in rats, administration of unlabelled 1 increased brain activity uptake by a factor of 9.5 (p = 0.0002, 2-tailed Student's t-test), whereas blood activity levels remained unchanged. In Mdr1a/b((-/-)) Bcrp1((-/-)) mice, the mean brain-to-blood ratio of activity at 60 min after tracer injection was 7.6 times higher as compared to wild-type animals (p = 0.0002). HPLC analysis of rat brain tissue extracts collected at 40 min after injection of [F-18]4b revealed that 93 +/- 7% of total radioactivity in brain was in the form of unchanged [F-18] 4b. In conclusion, the in vivo behavior of [F-18]4b was found to be similar to previously described [C-11]1 suggesting transport of [F-18]4b by Pgp and/or BCRP at the rodent BBB. However, low radiochemical yields and a significant degree of in vivo defluorination will limit the utility of [F-18]4b as a PET tracer. (C) 2011 Elsevier Ltd. All rights reserved.