Synthesis, in vitro and in vivo evaluation of 3β-[18F]fluorocholic acid for the detection of drug-induced cholestasis in mice

Abstract

IntroductionDrug-induced cholestasis is a liver disorder that might be caused by interference of drugs with the hepatobiliary bile acid transporters. It is important to identify this interference early on in drug development. In this work, Positron Emission Tomography (PET)-imaging with a 18F labeled bile acid analogue was introduced to detect disturbed hepatobiliary transport of bile acids.Methods3β-[18F]fluorocholic acid ([18F]FCA) was prepared by nucleophilic substitution of a mesylated precursor with [18F]fluoride, followed by deprotection with sodium hydroxide. Transport of [18F]FCA was assessed in vitro using CHO-NTCP, HEK-OATP1B1, HEK-OATP1B3 transfected cells and BSEP & MRP2 membrane vesicles. Investigation of [18F]FCA metabolites was performed with primary mouse hepatocytes. Hepatobiliary transport of [18F]FCA was evaluated in vivo in wild-type, rifampicin and bosentan pretreated FVB-mice by dynamic μPET scanning.ResultsRadiosynthesis of [18F]FCA was achieved in a moderate radiochemical yield (8.11 ± 1.94%; non-decay corrected; n = 10) and high radiochemical purity (>99%). FCA was transported by the basolateral bile acid uptake transporters NTCP, OATP1B1 and OATP1B3. For canalicular efflux, BSEP and MRP2 are the relevant bile acid transporters. [18F]FCA was found to be metabolically stable. In vivo, [18F]FCA showed fast hepatic uptake (4.5 ± 0.5 min to reach 71.8 ± 1.2% maximum % ID) and subsequent efflux to the gallbladder and intestines (93.3 ± 6.0% ID after 1 hour). Hepatobiliary transport of [18F]FCA was significantly inhibited by both rifampicin and bosentan.ConclusionA 18F labeled bile acid analogue, [18F]FCA, has been developed that shows transport by NTCP, OATP, MRP2 and BSEP. [18F]FCA can be used as a probe to monitor disturbed hepatobiliary transport in vivo and accumulation of bile acids in blood and liver during drug development.

Imaging techniques to study drug transporter function in vivo

“…Recently, an 18 F-labeled derivative of unconjugated cholic acid (3-[ 18 F]fluorocholic acid, Fig. 2) was shown to be a substrate of Na + -taurocholate co-transporting polypeptide (NTCP, SLC10A1), OATP1B1 (SLCO1B1) and OATP1B3 (SLCO1B3) (De Lombaerde et al, 2017), all of which are known to be involved in hepatocellular bile acid and bile salt uptake (Stieger, 2011). Furthermore, this bile acid derivative inhibited bile salt export pump (BSEP, ABCB11)-mediated taurocholate and MRP2-mediated estradiol-17ß-glucuronide transport.…”

“…Furthermore, this bile acid derivative inhibited bile salt export pump (BSEP, ABCB11)-mediated taurocholate and MRP2-mediated estradiol-17ß-glucuronide transport. In mice, pretreatment with rifampicin or bosentan (Fattinger et al, , 2001Stieger et al, 2000) was shown to interfere with hepatocellular transport of 3-[ 18 F]fluorocholic acid (De Lombaerde et al, 2017).…”

Use of imaging to assess the activity of hepatic transporters

“…3β-[ 18 F]fluorocholic acid ([ 18 F]FCA), was synthesized and shown to be in vitro a substrate of OATP1B1, OATP1B3, NTCP, BSEP, and MRP2 [92]. In vivo studies in mice pre-treated with the NTCP and the BSEP inhibitor bosentan or with rifampicin (prototypical OATP inhibitor) revealed significant changes in the pharmacokinetics of [ 18 F]FCA when these inhibitors were administered [92]. Recently, this radiotracer has also been applied in different mouse models of liver disease [93].…”

N-(4-[18F]fluorobenzyl)cholylglycine, a novel tracer for PET of enterohepatic circulation of bile acids: Radiosynthesis and proof-of-concept studies in rats

“…PET imaging [20][21][22][23][24][25][26], but so far no imaging agent has been reported for imaging of the EHC. In particular,…”