cytochrome P450
cytochrome P450
Overview
Cytochrome P450 (CYP) refers to a large superfamily of heme-containing enzymes that catalyze oxidative metabolism of a wide range of endogenous compounds and xenobiotics. In humans, CYP enzymes are central to drug biotransformation, steroid and lipid metabolism, and the clearance or activation of many therapeutic agents. Because of this broad substrate specificity, cytochrome P450 proteins are among the most important determinants of pharmacokinetics, drug–drug interactions, and interindividual variability in drug response.
Clinically, specific CYP isoforms such as CYP3A4, CYP2C9, CYP2D6, CYP1A2, and CYP11A1 are frequently studied as drug-metabolizing or biosynthetic targets. Their activity can be altered by genetic polymorphism, enzyme inhibition, induction, or tissue-specific expression changes. As a result, cytochrome P450 enzymes are routinely evaluated in drug development, toxicity screening, and precision medicine, particularly in relation to compounds such as midazolam, omeprazole, tolbutamide, fluconazole, clopidogrel, and oral contraceptives.
Focus of Latest Publications
Recent publications have continued to examine cytochrome P450 in the context of drug metabolism, pharmacokinetic variability, and drug–drug interactions. A clinical study combined with physiologically based pharmacokinetic modeling evaluated siponimod elimination in the presence of the CYP3A4 inhibitor clarithromycin and found only minimal changes in exposure, supporting the conclusion that there was no clinically relevant interaction. The updated model estimated a low CYP3A4 fraction metabolized and predicted no clinically relevant interaction with moderate or strong CYP3A4 inhibitors across CYP2C9 genotypes, although fluconazole was predicted to increase siponimod exposure more substantially in the CYP2C922 genotype.
Genotype-dependent CYP activity has also been investigated in antiplatelet therapy. In patients with recurrent ischemic stroke receiving clopidogrel monotherapy, combined genotyping of multiple enzymes showed that CYP2C19 intermediate and poor metabolism were associated with clopidogrel resistance in patients with normal ABCB1 efflux activity, while CYP2C9 intermediate and poor metabolism were associated with resistance among patients with normal CYP2C19 metabolism. These findings were interpreted as supporting the need for clinical guidance beyond CYP2C19 alone, including consideration of ABCB1 and CYP2C9.
Other recent work has focused on CYP-mediated bioactivation and inhibition in translational and experimental settings. An intravenous micellar formulation of clopidogrel was designed to enhance hepatic exposure and CYP450-mediated activation, producing a faster onset of the active metabolite and stronger antiplatelet effects than conventional oral dosing. In a separate medicinal chemistry study, new CYP11A1 inhibitors were developed for castration-resistant prostate cancer; one compound showed potent inhibitory activity and improved selectivity against CYP1A2, CYP2C9, and CYP2D6 relative to the reference candidate. A review of humanized liver chimeric mice further highlighted these models as tools for predicting human CYP3A and CYP2C9-mediated drug–drug interactions and drug clearance.
Cytochrome P450 has also appeared in toxicology and computational screening studies. zearalenone-14-glucoside was reported to form a self-assembled supramolecular gel and to cause stronger tissue toxicity than zearalenone, with proteomic evidence indicating that this effect was achieved by depleting cytochrome P450. In an in silico breast cancer study, garlic-derived organosulfur compounds were screened against multiple biomarkers, and only Z-ajoene was predicted to inhibit CYP2C9, suggesting a possible basis for drug–drug interaction risk.