Cytochrome P450 family 3 subfamily A member 4 (CYP3A4) and ATP-binding cassette sub-family B member 1 (P-gp) (CYP3A4 / P-gp)

Cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) constitute a fundamental biochemical barrier that governs the absorption, distribution, and elimination of a vast array of pharmacological agents [1, 2]. CYP3A4 is the most significant phase I drug-metabolizing enzyme in humans, primarily located in the liver and intestinal mucosa, where it oxidizes approximately 50% of all clinical drugs [1, 3]. P-gp, an ATP-dependent efflux pump encoded by the ABCB1 gene, is co-localized with CYP3A4 in the intestine and also found in the blood-brain barrier, where it actively transports substrates out of cells to prevent systemic or tissue-specific accumulation [2, 4]. These two proteins exhibit overlapping substrate specificity and work in a synergistic manner; P-gp-mediated efflux can increase the residence time of a drug in the enterocyte, thereby enhancing its exposure to CYP3A4-mediated metabolism [5, 6]. This interplay is a critical determinant of oral bioavailability and a major source of clinically significant drug-drug interactions, as the inhibition or induction of this system can lead to either toxic drug levels or therapeutic failure [7, 8]. Consequently, evaluating the interaction of new chemical entities with the CYP3A4/P-gp axis is a mandatory component of modern drug development and safety assessment [7].

Other names

CYP3A4P-gpMDR1ABCB1Cytochrome P450 family 3 subfamily A member 4ATP-binding cassette sub-family B member 1Multidrug resistance protein 1P-glycoprotein 1

The system is modulated through competitive and non-competitive inhibition, transcriptional induction (primarily via the Pregnane X Receptor), and substrate-level competition for oxidative metabolism and ATP-dependent efflux.