AstraZeneca, Biosensors, and The Medicines Company.

BACKGROUND: Patients at high risk for bleeding who undergo percutaneous coronary intervention (PCI) often receive bare-metal stents followed by 1 month of dual antiplatelet therapy. We studied a polymer-free and carrier-free drug-coated stent that transfers umirolimus (also known as biolimus A9), a highly lipophilic sirolimus analogue, into the vessel wall over a period of 1 month. METHODS: In a randomized, double-blind trial, we compared the drug-coated stent with a very similar bare-metal stent in patients with a high risk of bleeding who underwent PCI. All patients received 1 month of dual antiplatelet therapy. The primary safety end point, tested for both noninferiority and superiority, was a composite of cardiac death, myocardial infarction, or stent thrombosis. The primary efficacy end point was clinically driven target-lesion revascularization. RESULTS: We enrolled 2466 patients. At 390 days, the primary safety end point had occurred in 112 patients (9.4%) in the drug-coated-stent group and in 154 patients (12.9%) in the bare-metal-stent group (risk difference, -3.6 percentage points; 95% confidence interval [CI], -6.1 to -1.0; hazard ratio, 0.71; 95% CI, 0.56 to 0.91; P<0.001 for noninferiority and P=0.005 for superiority). During the same time period, clinically driven target-lesion revascularization was needed in 59 patients (5.1%) in the drug-coated-stent group and in 113 patients (9.8%) in the baremetal-stent group (risk difference, -4.8 percentage points; 95% CI, -6.9 to -2.6; hazard ratio, 0.50; 95% CI, 0.37 to 0.69; P<0.001). CONCLUSIONS: Among patients at high risk for bleeding who underwent PCI, a polymer-free umirolimus-coated stent was superior to a bare-metal stent with respect to the primary safety and efficacy end points when used with a 1-month course of dual antiplatelet therapy. (Funded by Biosensors Europe; LEADERS FREE ClinicalTrials.gov number, NCT01623180.).

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Cytochrome P450 (CYP) monooxygenases catalyze the oxidation of a large number of endogenous compounds and the majority of ingested environmental chemicals, leading to their elimination and often to their metabolic activation to toxic products. This enzyme system therefore provides our primary defense against xenobiotics and is a major determinant in the therapeutic efficacy of pharmacological agents. To evaluate the importance of hepatic P450s in normal homeostasis, drug pharmacology, and chemical toxicity, we have conditionally deleted the essential electron transfer protein, NADH:ferrihemoprotein reductase (EC 1.6.2.4, cytochrome P450 reductase, CPR) in the liver, resulting in essentially complete ablation of hepatic microsomal P450 activity. Hepatic CPR-null mice could no longer break down cholesterol because of their inability to produce bile acids, and whereas hepatic lipid levels were significantly increased, circulating levels of cholesterol and triglycerides were severely reduced. Loss of hepatic P450 activity resulted in a 5-fold increase in P450 protein, indicating the existence of a negative feedback pathway regulating P450 expression. Profound changes in the in vivo metabolism of pentobarbital and acetaminophen indicated that extrahepatic metabolism does not play a major role in the disposition of these compounds. Hepatic CPR-null mice developed normally and were able to breed, indicating that hepatic microsomal P450-mediated steroid hormone metabolism is not essential for fertility, demonstrating that a major evolutionary role for hepatic P450s is to protect mammals from their environment. The hepatic cytochrome P450 (CYP)1 -dependent monoxygenase system plays a central role in mammalian defense against harmful environmental chemicals (1); it is also a major determinant of the half-life and pharmacological properties of therapeutic drugs and in certain cases, mediates the activation of drugs, toxins, and carcinogens to their ultimate toxic species (2, 3). Several other functions have been ascribed to hepatic P450s, including control of cholesterol and steroid hormone metabolism and bile acid biosynthesis (4). However, for certain of these pathways, the exact role of P450s in normal homeostasis is unknown.Over the last four decades, there have been significant advances in understanding the functions, genetics, and regulation of these enzymes and more recently their structure (5). However, a great deal remains to be learned about the expression and regulation of P450s, and their endogenous function(s), particularly in individual tissues. The size and diversity of the P450 multigene family results in great difficulties in dissecting out the function(s) of individual enzymes, particularly as many of those involved in foreign compound metabolism exhibit overlapping substrate specificities and may be expressed to a greater or lesser extent in almost every cell and tissue. The contribution that P450s in any particular tissue make to the overall pharmacokinetics of a drug is still, in the majority of cases,...