BSEP and MRP inhibition is in our portfolio of in vitro drug transporter services. Cyprotex delivers consistent, high quality data in line with our published transporter strategy review, for either your early stage screening projects or your later stage regulatory studies according to FDA, EMA, PMDA and ICH guidance.

The impact of BSEP and MRP inhibition and their measurement in vitro:

• BSEP (bile salt export pump; ABCB11) is an ATP binding cassette (ABC) efflux transporter located on the canalicular membrane of hepatocytes¹.
• BSEP is the major transporter for the secretion of bile acids from hepatocytes into bile in humans¹.
• Bile secretory failure results in cholestasis. Bile secretory failure may be a result of:
  • Mutations in the gene encoding for BSEP which have been associated with cholestatic liver diseases of varying severity including progressive familial intrahepatic cholestasis type 2 (PFIC-2) and benign recurrent intrahepatic cholestasis type 2 (BRIC-2)².
  • Direct inhibition of BSEP by xenobiotics or drugs leading to acquired cholestasis and drug-induced liver injury (DILI)³.
• Because of the link between BSEP inhibition and initiation of cholestatic DILI, the European Medicines Agency Guideline on the Investigation of Drug Interactions (2012) recommends in vitro screening of BSEP inhibition. If inhibition is observed then adequate biochemical monitoring including serum bile salts should be assessed during drug development⁴. Furthermore, the International Transporter Consortium recommends proactive evaluation and understanding of BSEP inhibition in drug discovery and development in order to aid internal decision making on the risk of DILI^5,6.
• MRP2 (multidrug resistance associated protein 2; ABCC2), MRP3 (ABCC3) and MRP4 (ABCC4) are ATP binding cassette (ABC) efflux transporters located on the canalicular membrane (MRP2) or sinusoidal membrane (MRP3, MRP4) of hepatocytes ^5,6.
• MRP2 transports conjugated bile acids from hepatocytes into bile, whereas MRP3 and MRP4 are able to transport bile acids from hepatocytes into blood⁵.
• MRP3 and MRP4 efflux transporters are upregulated under cholestatic conditions suggesting they provide a protective role against bile acid-mediated hepatotoxicity by alleviating increases in intracellular bile acid concentrations, which may occur as a result of impaired biliary excretion due to inhibition of BSEP^5,6,7.
• Understanding whether a compound is able to inhibit MRP transporters may therefore provide useful additional information towards helping evaluate the risk of DILI.
• Cyprotex offers BSEP, MRP2, MRP3 and MRP4 inhibition assays which investigate inhibition of the uptake of prototypical probe substrates (taurocholic acid for BSEP, estradiol 17β-D-glucuronide for MRP2 and MRP3, and dehydroepiandrosterone sulfate for MRP4) into inside-out membrane vesicles overexpressing the human ABC-transporter of interest.

_{1) Wang L et al., (2002) The role of bile salt export pump mutations in progressive familial intrahepatic cholestasis type II. J Clin Invest 110(7); 965-972
2) Dawson PA, Lan T, and Rao A. (2009) Bile acid transporters. Journal of Lipid Research 50(12); 2340-2357
3) Stieger B (2010) Role of the bile salt export pump, BSEP, in acquired forms of cholestasis. Drug Metab Rev 42(3); 437-445
4) The European Medicines Agency (EMA) Guideline on the Investigation of Drug Interactions (Adopted 2012)
5) Kenna JG et al., (2018) Can bile salt export pump inhibition testing in drug discovery and development reduce liver injury risk? An International Transporter Consortium perspective. Clin Pharmacol Ther 104(5); 916-932
6) Zamek-Gliszczynski MJ et al., (2018) Transporters in drug development: 2018 ITC recommendations for transporters of emerging clinical importance. Clin Pharmacol Ther 104(5); 890-899
7) Morgan RE et al., (2013) A multifactorial approach to hepatobiliary transporter assessment enables improved therapeutic compound development, Toxicol Sci 136; 216-241}