UGT Enzyme Inhibition

Assay SelectionTest SystemIncubation ConditionsInhibitorsAutomation and AnalysisResultsFollowup Studies

Glucuronidation is a major pathway of xenobiotic biotransformation in mammalian species.  Glucuronidation requires the co-factor UDPGA and the reaction is catalyzed by UDP-glucuronosyltransferases (UGTs), which are located predominantly in the endoplasmic reticulum of liver.  Since drug-drug interactions that are at least partly due to inhibition of UGTs have been reported, identification of the UGT(s) involved in the metabolism of a compound can allow for a better DDI prediction.

XenoTech’s study design evaluates drug candidates as direct-acting inhibitors of UGT enzymes in human liver microsomes. Our study design features low protein concentrations and short incubation times to minimize artifacts caused by protein binding, metabolic instability of the test article and excessive metabolism of the marker substrate.

Download XenoTech's UGT Inhibition Informational Flyer Here!

Assay Selection

UGT1A1      17β-Estradiol 3-glucuronidation
UGT1A4      Trifluoperazine glucuronidation
UGT1A6      1-Naphthol glucuronidation
UGT1A9      Propofol glucuronidation
UGT2B7      Morphine 3-glucuronidation

Test System

Dedicated pool of 16 individuals, mixed gender, native human liver microsomes

More Information

XenoTech’s inhibition assays are typically performed with a dedicated pool of human liver microsomes characterized to provide K_m and V_max values for each marker substrate reaction.  This allows the same sample of pooled human liver microsomes (and often the same experimental conditions, for example, protein concentration and incubation time) to be used to study all UGT enzymes of interest.

Incubation Conditions

Typical IC₅₀ incubation conditions  

Protein concentration: ≤0.1 mg/mL

Incubation time: 5 minutes

Inhibitors

Troglitazone

Automation and Analysis

Tecan liquid-handling system or manual incubations available
Validated LC/MS/MS methods
High-throughput Shimadzu autosamplers
Deuterated internal standards for most UGTs
Automated data retrieval and processing
Comprehensive, publication-quality reports
Available as GLP or non-GLP

Results

Direct inhibition IC₅₀ values determined from seven concentrations of the drug candidate.

Followup Studies

Direct Inhibition

K_i determinations: determine K_i value for direct inhibition with multiple concentrations of the drug candidate and marker substrate.