Synthesis, in vitro and in vivo small-animal SPECT evaluation of novel technetium labeled bile acid analogues to study (altered) hepatic transporter function

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• 作者：Sara Neyt^a ; ^{sara.neyt@ugent.be" class="auth_mail" title="E-mail the corresponding author} ; Maarten Vliegen^b ; Bjorn Verreet^b ; Stef De Lombaerde^a ; Kim Braeckman^c ; Christian Vanhove^c ; Maarten Thomas Huisman^b ; Caroline Dumolyn^a ; Ken Kersemans^a ; Fabian Hulpia^d ; Serge Van Calenbergh^d ; Geert Mannens^b ; Filip De Vos^a
• 关键词：Bile acid analogues ; Technetium ; Drug induced cholestasis ; Small-animal SPECT ; Hepatobiliary imaging
• 刊名：Nuclear Medicine and Biology
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：43
• 期：10
• 页码：642-649
• 全文大小：923 K

文摘

Hepatobiliary transport mechanisms are crucial for the excretion of substrate toxic compounds. Drugs can inhibit these transporters, which can lead to drug–drug interactions causing toxicity. Therefore, it is important to assess this early during the development of new drug candidates. The aim of the current study is the (radio)synthesis, in vitro and in vivo evaluation of a technetium labeled chenodeoxycholic and cholic acid analogue: [^99mTc]-DTPA-CDCA and [^99m]Tc-DTPA-CA, respectively, as biomarker for disturbed transporter functionality.

Methods

[99mTc]-DTPA-CDCA([^99mTc]-3a) and [99mTc]-DTPA-CA ([^99mTc]-3b) were synthesized and evaluated in vitro and in vivo. Uptake of both tracers was investigated in NTCP, OCT1, OATP1B1, OATP1B3 transfected cell lines. K_m and V_max values were determined and compared to [^99mTc]-mebrofenin ([^99mTc]-MEB). Efflux was investigated by means of CTRL, MRP2 and BSEP transfected inside-out vesicles. Metabolite analysis was performed using pooled human liver S9. Wild type (n = 3) and rifampicin treated (n = 3) mice were intravenously injected with 37 MBq of tracer. After dynamic small-animal SPECT and short CT acquisitions, time–activity curves of heart, liver, gallbladder and intestines were obtained.

Results

We demonstrated that OATP1B1 and OATP1B3 are the involved uptake transporters of both compounds. Both tracers show a higher affinity compared to [^99mTc]-MEB, but are in a similar range as endogenous bile acids for OATP1B1 and OATP1B3. [^99mTc]-3a shows higher affinities compared to [^99mTc]-3b. V_max values were lower compared to [^99mTc]-MEB, but in the same range as endogenous bile acids. MRP2 was identified as efflux transporter. Less than 7% of both radiotracers was metabolized in the liver. In vitro results were confirmed by in vivo results. Uptake in the liver and efflux to gallbladder + intestines and urinary bladder of both tracers was observed. Transport was inhibited by rifampicin.

Conclusion

The involved transporters were identified; both tracers are taken up in the hepatocytes by OATP1B1 andOATP1B3 with K_m and V_max values in the same range as endogenous bile acids and are secreted into bile canaliculi via MRP2. Dynamic small-animal SPECT imaging can be a useful noninvasive method of visualizing and quantifying hepatobiliary transporter functionality and disturbances thereof in vivo, which could predict drug pharmacokinetics.