Parkinson, Andrew published the artcileAn evaluation of the dilution method for identifying metabolism-dependent inhibitors of cytochrome P450 enzymes, Quality Control of 40180-04-9, the main research area is liver microsome dilution cytochrome P450 inhibitor metabolism.
Metabolism-dependent inhibition (MDI) of cytochrome P 450 is usually assessed in vitro by examining whether the inhibitory potency of a drug candidate increases after a 30-min incubation with human liver microsomes (HLMs). To augment the IC50 shift, many researchers incorporate a dilution step whereby the samples, after being preincubated for 30 min with a high concentration of HLMs (with and without NADPH), are diluted before measuring P 450 activity. In the present study, we show that the greater IC50 shift associated with the dilution method is a consequence of data processing. With the dilution method, IC50 values for direct-acting inhibitors vary with the dilution factor unless they are based on the final (postdilution) inhibitor concentration, whereas the IC50 values for MDIs vary with the dilution factor unless they are based on the initial (predilution) concentration When the latter data are processed on the final inhibitor concentration, as is commonly done, the IC50 values for MDI (shifted IC50 values) decrease by the magnitude of the dilution factor. The lower shifted IC50 values are a consequence of data processing, not enhanced P 450 inactivation. In fact, for many MDIs, increasing the concentration of HLMs actually leads to considerably less P 450 inactivation because of inhibitor depletion and/or binding of the inhibitor to microsomes. A true increase in P 450 inactivation and IC50 shift can be achieved by assessing MDI by a nondilution method and by decreasing the concentration of HLMs. These results have consequences for the conduct of MDI studies and the development of cut-off criteria.
Drug Metabolism and Disposition published new progress about Dilution. 40180-04-9 belongs to class benzothiophene, name is 2-(2,3-Dichloro-4-(thiophene-2-carbonyl)phenoxy)acetic acid, and the molecular formula is C13H8Cl2O4S, Quality Control of 40180-04-9.
Referemce:
Benzothiophene – Wikipedia,
Benzothiophene | C8H6S – PubChem