Aug 03, 2025
Metabolic stability assay in rat or dog microsomes
- Nick Lynch1,2
- 1Curlew Research;
- 2ASAP Discovery Consortium
- ASAP Discovery
Protocol Citation: Nick Lynch 2025. Metabolic stability assay in rat or dog microsomes. protocols.io https://dx.doi.org/10.17504/protocols.io.j8nlkrqbxv5r/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: May 25, 2025
Last Modified: August 03, 2025
Protocol Integer ID: 218901
Keywords: metabolic stability, ADME, DMPK, drug discovery, microsome, context of liver microsome, liver microsome, metabolic stability, drug with microsome, metabolizing many drug, cytochrome p450, liver cell, microsome, liver, fraction of liver cell, enzyme system, enzyme, drug, assay, many drug
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Abstract
Metabolic stability, in the context of liver microsomes, refers to how quickly a drug candidate is metabolized (broken down) by the liver's enzyme system, specifically within the microsomes. This is measured by incubating a drug with microsomes and determining how much of the original drug remains after a set time. Microsomes are a fraction of liver cells enriched with enzymes, particularly cytochrome P450 (CYP) enzymes, which are responsible for metabolizing many drugs.
Troubleshooting
Safety warnings
Always wear appropriate PPE for this protocol
Refer to Material Safety Data Sheets for additional safety and handling information.
Summary
The metabolic stability in microsomes is performed in 96-well plate format
This protocol can be used with the following microsomes:
- Rat
- Dog
Sample Preparation
The compounds are incubated in 1 uM concentration in a shaking incubator at 37ºC
The relevant microsomes are diluted to a concentration of 1mg /mL and equilibrated at 37ºC for 10 minutes in the presence of NADPH cofactor
Assay
Biotransformation is initiated by addition of compound and mixing
Standard time-points are used as 0, 5, 10, 15, 25, 35 min, and the final solvent concentrations are 0.99 % methanol and 0.01 % DMSO
At each specified time-point, a sample aliquot (25μL) is removed from the test incubation mixture and combined into a cassette of up to 4 compounds, in 300μL ice cold methanol containing internal standards (Dextromethorphan, Diazepam, Midazolam and Phenacetin), and mixing to stop the reaction
The quenched samples are then centrifuged to precipitate the protein.
Analytical
The supernatants are analyzed by LC-MS/MS using generic analytical methods to measure the test parent compound remaining at each time-point.
Data Analysis
Clearance and half-life are calculated from the elimination rate constant derived from plotting response ratio versus time
Acknowledgements
Grateful to Concept Life Sciences for supplying the original protocol summary