The inhibition of human cytochrome P450s (CYPs) is one of the most common mechanismswhich can lead to drug-drug interactions. The inhibition of CYPs can be reversible or irreversible.Irreversible inhibition usually derives from activation of a drug by CYPs into a reactivemetabolite, which tightly binds to the enzyme active site, leading to a long lasting inactivation.This process is called “suicide inhibition”.The irreversible inactivation usually implies the formation of a covalent bond between themetabolite and the enzyme, which can lead to hapten formation and can in some cases trigger anautoimmune-response.For these reasons it is of utmost importance to study the mechanism of the CYP inhibition ofnew potential drugs as early as possible during the drug discovery process.In this thesis, a strategy to avoid the development of drugs that might cause CYP suicideinhibition in patients is proposed.First, a database with all the chemical entities responsible for suicide inhibition of human andanimal CYPs , was compiled, after a wide literature search. The most common substructuresconsidered responsible for CYP inactivation are highlighted, and named structural alerts.Second, a new screening assay, based on fluorescence, to quantitatively assess time dependentinhibition of CYP3A4 was set and validated. By running this assay, structure-time dependentinhibition relationships were derived for a group of compounds, differently substituted on thefuran ring, a potentially dangerous substructure.Third, two compounds containing a furan ring, -a structural alert- and causing time dependentinhibition on CYP3A4, were used for a series of more specific tests (also using 14C labelledderivatives). The activity of these two compounds as suicide inhibitors of CYP3A4 wasdemonstrated.
