2-Diethylaminoethyl-2,2-diphenylvalerate-HCl (SKF525A) Revisited: Comparative Cytochrome P450 Inhibition in Human Liver Microsomes by SKF525A, Its Metabolites, and SKF-Acid and SKF-Alcohol

Abstract

ABSTRACT:When incubated with human liver microsomes, 2-diethylaminoethyl-2,2-diphenylvalerate-HCl (SKF525A) undergoes cytochrome P450 (P450)-dependent oxidative N-deethylation to the secondary amine metabolite 2-ethylaminoethyl-2,2-diphenylvalerate (SKF8742). P450-selective inhibitors indicated CYP3As catalyzed this reaction, and the deethylation rate correlated best with the CYP3A activity across a range of human liver microsomes. SKF525A and its metabolite and primary amine analog all inhibited CYP2B6-, CYP2C9-, CYP2C19-, CYP2D6-, and CYP3A-selective reactions to varying degrees but had little effect on CYP1A2, CYP2A6, and CYP2E1 reactions. Only the inhibition of CYP3A showed major enhancement when the inhibitors were preincubated with NADPH-fortified microsomes, and the extent of metabolic intermediate (MI) complex formation approximated typical CYP3A content. Two "lost with time" SKF525A derivatives devoid of the ethylamine moiety, 2,2-diphenylpropylethanol (SKF-Alcohol) and 2,2-diphenylpropylacetic acid (SKF-Acid) did not form an MI complex and were identified as selective inhibitors of CYP2C9. Although without detectable metabolism, their CYP2C9 inhibition fitted best with a competitive mechanism. Thus, not all the human P450s are inhibited by SKF525A and related compounds, and the mechanisms contributing to those that are inhibited vary with the isoform. P450 MI-complex formation only seems to play a role with CYP3As.

Substrates, Inducers, Inhibitors and Structure-Activity Relationships of Human Cytochrome P450 2C9 and Implications in Drug Development

“…SKF525A and its metabolite SKF8742 and primary amine analog inhibited CYP2C9 in vitro [1411]. Olomoucine II, a cyclindependent kinase inhibitor used as a potential antineoplastic agent, significantly inhibited CYP2C9 with an IC 50 of 39.1 M in vitro [1412].…”

A Comparison of the In Vitro Inhibitory Effects of Thelephoric Acid and SKF-525A on Human Cytochrome P450 Activity

“…However, it does not strongly inhibit all CYP family members (Emoto et al ., 2003; Franklin and Hathaway, 2008). In particular, SKF-525A has been reported to weakly inhibit recombinant human CYP1A2 and CYP2E1 within the concentration range of 100–1,200 μM (Emoto et al ., 2003).…”

Whatever Happened to the Epoxyeicosatrienoic Acid-Like Endothelium-Derived Hyperpolarizing Factor? The Identification of Novel Classes of Lipid Mediators and Their Role in Vascular Homeostasis

“…There are fewer in vivo studies available, but it seems that blood pressurelowering actions of x-3 PUFAs are absent in mice lacking the gene which encodes the pore-forming b-subunit of the BK channel (63). While it is tempting to speculate that the effects described in wild-type mice in the latter paper could be attributed to the production of the epoxides from EPA and DHA, the effects were insensitive to SKF525A, which rather unselectively targets several different CYP enzymes, for example, CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A (53), and can affect nicotinic receptor activation (157). An alternative means of increasing PUFA epoxide levels is to inhibit the sEH, and in a model of angiotensin IIinduced hypertension where animals were supplemented with an EPA-/DHA-rich diet in combination with an sEH inhibitor-the antihypertensive effects of DHA/EPA were potentiated (163).…”