ADME in vitro screen

Chapter 4 Mass Spectrometry for In Vitro ADME Screening.99... 

Table 15.1). As a multiple-task instrument, the QTRAP may serve as the LC—MS platform of choice in certain DMPK and bioanalysis laboratories. Specific examples of these laboratories would include (1) bioanalytical laboratories where detection of plasma metabolites or in vitro ADME screening are also performed (2) drug metabolism laboratories where metabolite identification and/or in vitro ADME screening are conducted, and (3) small bioanalysis and drug metabolism laboratories where quantitative and qualitative analyses of drugs and/or metabolites are routinely conducted with limited numbers of LC—MS instruments and scientists. 

Examples of LC-MS Support of in vitro ADME Screening Assays... 

Metabolic Stability Metabolic stability assays are the most widely used in vitro ADME screening assay. Metabolism is the body s major mechanism of detoxification of foreign compounds (xenobiotics) such as drug molecules. Common metabolic reactions can be categorized as (1) phase I reactions, which are direct modifications such as oxidation and (2) phase II reactions, which are conjugations such as glucuronidation. As a result of these metabolic conversions, xenobiotics become polar metabolites which can be cleared more... 

Bioanalytical support for DDI assays with EC-MS is distinctively different from support for most other ADME screens in that only the probe metabolite (instead of all test compounds) is monitored in all samples. As a result, no MS/MS method optimization (other than that for the probe metabolite) is needed. On the other hand, the EC-MS/MS sample burden for CYP inhibition assays is probably the heaviest among all in vitro ADME screening assays, as CYP assays are typically conducted in 384-well plates and involve full IC50 (half maximal inhibitory concentration) curves, and many times in a time-dependent fashion to measure inhibition potentials for both the test compound and its metabohte(s). As a result, bioanalytical research for CYP inhibition support has mostly focused on improving sample analysis speed and throughput. (Data handling and report generation are now mostly automated and do not represent a bottle neck.) Several assay and bioanalytical approaches used either individually or in combination have been reported for CYP inhibition sample analysis. One approach is to incubate multiple substrates for multiple isozymes in the same well, and use an SRM method with multiple MS/MS transitions to analyze all the metabolites and assess the inhibition... 

In-vitro ADME Screens + P450 Inhibition screen... 

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