Effect of everolimus-eluting stents in different vessel sizes (from the pooled FUTURE I and II trials)

Identification of Everolimus Metabolite Patterns in Trough Blood Samples of Kidney Transplant Patients

Everolimus is used as an immunosuppressant after organ transplantation. It is extensively metabolized, mainly by cytochrome P4503A enzymes, resulting in several hydroxylated and demethylated metabolites. The structures of these metabolites after in vitro metabolism of everolimus by human liver microsomes have recently been identified. It was the goal to elucidate the everolimus metabolite patterns in 128 trough blood samples from kidney graft patients using high-performance liquid chromatography (LC)-ion trap mass spectrometry (MS) in combination with analysis of the fragmentation patterns of the metabolites isolated from patient blood and comparison with the metabolites generated in vitro. After identification, concentrations of the metabolites were estimated using LC-MS. Relative to the everolimus concentrations in trough blood samples, metabolite concentrations were [median (range), n = 128] 46-hydroxy 44.1% (0-784%), 24-hydroxy 7.7% (0-85.6%), and 25-hydroxy 14.4% (0-155.4%); 11-Hydroxy, 12-hydroxy, 14-hydroxy, 49-hydroxy, two hydroxy-piperidine everolimus metabolites, 16-O-desmethyl, 16,39-O-didesmethyl, 16,27-O-didesmethyl, and 27,39-O-didesmethyl everolimus were also detected. However, when detectable, concentrations were consistently between the lower limit of detection (0.1 microg/L) and the lower limit of quantification (0.25 microg/L) of our LC-MS assay. In most trough blood samples, the total metabolite concentrations were between 50% and 100% of the everolimus concentrations. The clinical importance of everolimus metabolites in blood of patients including pharmacodynamics, toxicodynamics, and cross-reactivity with the antibodies of immunoassays used for therapeutic drug monitoring remains to be evaluated.

Understanding the drug-eluting stent trials

The advent of intravascular stenting dramatically reduced the incidence of restenosis among patients undergoing percutaneous transluminal coronary angioplasty. However, a substantial percentage of patients, particularly those with risk factors such as diabetes mellitus or complicated lesions, remain at risk for restenosis. Drug-eluting stents overcome this problem by releasing bioactive agents from a polymeric coating directly into the vessel wall, inhibiting the cellular mechanisms of restenosis while avoiding systemic toxicity. Recent data indicate that local targeting of the proliferative process with drug-eluting stents dramatically reduces the risk for restenosis, even among high-risk patients. A range of bioactive coatings are currently available or in late clinical trials. Both sirolimus- and paclitaxel-eluting stents have demonstrated efficacy in a broad range of patient types; early data from clinical trials of second-generation stent coatings, such as everolimus and ABT-578 (zotarolimus), suggest that these agents are also effective in preventing restenosis. This article reviews the pathophysiology of in-stent restenosis and surveys recent key clinical trials of drug-eluting stents.

The next generation of drug-eluting stents: what's on the horizon?

Drug-eluting stents have radically changed the way we treat coronary artery disease. They offer lower restenotic rates compared with the bare metal stents and this enables more challenging and complex lesions to be treated. However, there are still limitations as restenosis has not been completely abolished and there are concerns about stent thrombosis. The next generation stents offer the technology to address these pertinent issues. This review examines the new analogs of the sirolimus family and their use in novel stent platforms, including the use of biodegradable and bioabsorbable materials employed in both stents and on the polymer. "Reservoir stents" that are specially designed to contain layers of drugs in pockets with different release profiles are discussed and an insight into the emerging field of bioengineered stents is highlighted.

Can mTOR inhibitors reduce the risk of late kidney allograft failure?

The most frequent causes of late kidney allograft failure are chronic rejection, nonalloimmune injury and death, all of which may depend on the characteristics of the donor and recipient, but may also be influenced by the type of immunosuppression. Combining calcineurin inhibitors (CNIs) and corticosteroids offers potent immunosuppression, but may also cause side effects leading to progressive graft dysfunction or an increased risk of death. New immunosuppressive strategies may come from the availability of inhibitors of mTOR, a downstream effector of phosphatidylinositol-3 kinase that provides the signal for cell proliferation by phosphorylating a cascade of kinases. Recent trials have shown that it is possible to minimize the dose or withdraw CNIs a few weeks after transplantation when they are combined with mTOR inhibitors and their combination may also make it possible to minimize or avoid the use of corticosteroids. Moreover, by inhibiting the signal for cell proliferation, mTOR inhibitors may reduce the replication of cytomegalovirus inside host cells, prevent transplant vasculopathy, and exert anti-oncogenic activity. All of these characteristics offer a ray of hope for reducing the risk of long-term allograft failure.

Clinical impact of in-stent late loss after drug-eluting coronary stent implantation†

AIMS

Controversy exists about the clinical significance of in-stent late loss (ISLL) after drug-eluting stent (DES) implantation. We sought to clarify whether ISLL after DES implantation is related to a potential clinical impact.

METHODS AND RESULTS

We included in a meta-regression analysis 21 trials (8641 patients) that randomly compared DES with bare-metal stents (BMS). We evaluated the relationship between angiographic behaviour of DES and the clinical impact of using DES instead of BMS in each trial using meta-regression techniques, weighting by the number of patients included in each trial. Mean ISLL in patients allocated to DES and DeltaISLL (difference in ISLL in patients allocated to BMS and DES) were used as angiographic parameters of efficacy of DES. The number of patients needed to be treated (NNT) to prevent one target lesion revascularization (TLR) was used to quantify the clinical impact of using DES instead of BMS. There was a significant relationship between mean ISLL in patients allocated to DES and the clinical benefit of using DES instead of BMS, as measured with the NNT for TLR: NNT for TLR = 6.2 + 18.4 [ISLL-DES] (R = 0.62; P = 0.007). Therefore, a 0.1 mm increase in mean ISLL-DES was associated with a 1.8 increase in NNT for TLR. There was also a significant association between the degree of inhibition of neointimal hyperplasia of DES in comparison with BMS with the NNT for TLR: NNT for TLR = 17.1-11.8 [DeltaISLL] (R = 0.61; P = 0.008). Therefore, a 0.1 mm reduction in ISLL by using DES instead of BMS was associated with a 1.2 decrease in mean NNT for TLR.

CONCLUSION

There is a strong and significant association between the degree of inhibition of neointimal formation with the use of DES and the clinical impact of using DES instead of BMS.