Radiosynthesis and in vivo evaluation of 1-[18F]fluoroelacridar as a positron emission tomography tracer for P-glycoprotein and breast cancer resistance protein
摘要:
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.
Synthesis of New Acridone Derivatives, Inhibitors of NS3 Helicase, Which Efficiently and Specifically Inhibit Subgenomic HCV Replication
摘要:
A new goup of acridone derivatives, obtained by reaction of acridone-4-carboxylic acid derivatives with aromatic amines, was tested to determine the inhibitory properties toward the NS3 helicase of hepatitis C virus (HCV). Six compounds inhibited the NS3 helicase at low concentrations (IC(50) from 1.5 to 20 mu M). The acridone derivatives probably act via intercalation into double-stranded nucleic acids with a strong specificity for double-stranded RNA, although an interaction with the enzyme cannot be excluded. Testing in the subgenomic HCV replicon system revealed that compounds 10 and 13 are efficient RNA replication inhibitors, with EC(50) of 3.5 and 1 mu M and therapeutic indexes of > 28 and 20, respectively. Compound 16, with EC(50) < 1 mu M and TI > 1000, is extremely specific and practically noncytotoxic at the concentrations tested, proving that the acridone derivatives may be regarded as potential antiviral agents. Although the mechanism of action of 16 in the replicon system remains unclear, it is the key lead compound for further development of anti-HCV drugs.