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Carboxylesterase (CE) inhibition assay

Understand if your compound is an inhibitor of carboxylesterases.

Carboxylesterase (CE) inhibition is a non-CYP mediated metabolism assay within our portfolio of in vitro ADME screening services. Cyprotex deliver consistent, high quality data with the flexibility to adapt protocols based on specific customer requirements.

Determining potential inhibition of carboxylesterase enzymes

  • Human carboxylesterases (CE) are Phase I drug metabolizing enzymes of the serine hydrolase superfamily. They hydrolyze a variety of ester containing drugs and prodrugs.
  • Carboxylesterase inhibitors may play a role in improved efficacy of compounds inactivated by this class of enzymes and/or reduce the toxicity of agents that are activated by these enzymes.
  • Cyprotex’s carboxylesterase inhibition assay identifies if your compound is an inhibitor of the carboxylesterase (CE) isoform, hCE1, using hCE1-b and hCE1-c recombinant enzymes.
CE inhibitors potentially have dual roles in modulating drug action, by both reducing induced toxicity and/or increasing molecule half-life.

1Hatfield M.J. and Potter P.M. (2011) Expert Opin Ther Pat 21(8); 1159-1171


Carboxylesterase inhibition assay protocol

Test System hCE1-b and/or hCE1-c expressed enzymes
Substrates Trandolapril (hCE1)
Metabolites Trandolaprilat (hCE1)
Test Article Concentrations 0, 0.4, 1, 4, 10, 40 and 100 µM (different concentrations available)
Positive Control Inhibitors Benzil (hCE1)
Test Article Requirements 100 µL of a 40 mM DMSO solution (or equivalent amount in solid)
Analysis Method LC-MS/MS
Data Delivery IC50
Standard error of IC50
% Control at each concentration


Data from the carboxylesterase (CE) inhibition assay

carboxylesterase inhibition
Figure 1
Inhibition of trandolapril (hCE1 substrate) metabolism in recombinant hCE1-b by benzil.


1Hatfield MJ and Potter PM (2011) Carboxylesterase inhibitors. Expert Opin Ther Pat 21(8); 1159-1171

Learn More

Learn more about drug metabolism in chapter 3 of our popular Everything you need to know about ADME guide. 

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