WEB EXCLUSIVE - Making Sense of the Volumes of Stent Presentations Made at TCT 2008

Biggest news is results from SYNTAX and HORIZON studies.
By: 
Dave Fornell

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October 21, 2008

The stent wars continued at the Transcatheter Cardiovascular Therapeutics 2008 20th annual symposium last week with scores of study presentations and a steady stream of company press releases from U.S. stent manufacturers, all attempting to explain which platform best serves patients. The biggest stent news from TCT was data analysis from two big stent studies – SYNTAX, which compared DES vs. bypass graft surgery, and HORIZONS, the largest study of acute myocardial infarction (AMI) patients.

Jeff Mirviss, Boston Scientific’s vice president of coronary stent marketing, said SYNTAX showed a much lower incidence of stroke using DES as compared to bypass surgery. There was no difference in the overall death rate or in the number of heart attacks between the two modalities. He said DES showed a lower recovery time rate and an 85 percent chance a patient will not need a second procedure to reopen vessels. Mirviss said this information will help empower doctors to tell their sickest patients stenting is a viable option and the study results will likely help to expand the angioplasty stent market. In addition to the outcomes reported in the study, he notes percutaneous procedures cost less than open chest procedures.

The initial data from the SYTAX study was released in September and analysis of various subsets will continue in the coming months. Mirviss said more information from subsets, possibly including surgical techniques, gender and ethnicity, will be released at ACC in 2009.

The HORIZONS trial examined treatment options for STEMI, or AMI, patients, which make up about 15 percent of the market, Mirviss said. The main component of the trial was to resolve the debate over whether BMS or DES is the best option for these patients, since most of the blockages being treated are caused by vulnerable plaque being dislodged. The study found there was no significant difference in thrombosis rates using DES or BMS.


Other Stent Studies

Data from an independent meta-analysis of Abbott’s SPIRIT II and SPIRIT III randomized clinical trials demonstrated that the XIENCE V everolimus eluting coronary stent continues to deliver clinically significant benefits for patients compared to the TAXUS paclitaxel eluting coronary stent out to two years, said Abbott.

Results were presented at TCT by Gregg W. Stone, M.D., principal investigator of the SPIRIT III trial. In this meta-analysis, which included patients from the U.S., Europe and Asia-Pacific, XIENCE V demonstrated clinical superiority to TAXUS in the endpoints of target vessel failure (TVF) and major adverse cardiac events (MACE) at two years. XIENCE V also demonstrated significantly lower clinical events rates than TAXUS in the key efficacy (target lesion revascularization) and safety components of MACE at two years.

The meta-analysis of 1,302 patients from the SPIRIT II and SPIRIT III trials shows a clinically significant 31 percent reduction in the risk of ischemia-driven target vessel failure compared to TAXUS.

Boston Scientific announced results from an analysis of nearly 7,500 patients from its TAXUS ARRIVE 1 and 2 registries, which are designed to confirm the performance of the TAXUS Express2 paclitaxel-eluting coronary stent in real-world practice. The two-year pooled ARRIVE data showed TAXUS reduced clinical restenosis in patients with diabetes as effectively as in patients without diabetes, with no incremental risk of myocardial infarction or stent thrombosis. Analysis of the data was presented by John M. Lasala, M.D., Ph.D., FACC.

“The ARRIVE diabetic subset data demonstrated that the TAXUS Stent mitigated the adverse effect of diabetes as a risk factor for restenosis and repeat procedures in the patients studied,” said Dr. Lasala, professor of medicine, Washington University School of Medicine in St. Louis. “While the diabetic patients had more cardiac risk factors, comorbidity and higher mortality than non-diabetics, the rates of reintervention, MI and stent thrombosis in the ARRIVE 1 and 2 registries were similar in both groups, regardless of risk profile.”

Boston Scientific also released data for the TAXUS ATLAS clinical program, a series of global, prospective, multi-center, single-arm, historically controlled trials, which evaluate the TAXUS Liberte paclitaxel-eluting stent in a variety of lesions and patient groups. The TAXUS Liberte received FDA approval Oct. 10. Results from the TAXUS ATLAS Workhorse, Direct Stenting, Small Vessel and Long Lesion trials were presented at TCT 2008.

“The TAXUS ATLAS studies reinforce the long-term safety and efficacy of the TAXUS Liberte stent while demonstrating the ability to access complex lesions, said Mark A. Turco, M.D., director of the Center for Cardiac and Vascular Research, Washington Adventist Hospital, and co-principal investigator of the trial. “The data showed significantly reduced restenosis in small vessels and positive results in direct stenting procedures. The positive ATLAS data suggest that improvements in stent design and a reduction in strut thickness may contribute to improved clinical outcomes for patients treated with the TAXUS Liberte stent.”


Debate Over Endeavor’s Short Elution Time

There were mixed comments in TCT sessions about Medtronic’s Endeavor DES, which elutes all its drug in about two weeks, while other DES brands continue eluting 100 days or more. Critics argue longer drug elution helps prevent new tissue growth, which will reduce in-stent restenosis. However, Daniel Beach, Medtronic Cardiovascular’s director of communications, said the reason for this quick elution is to get the patient through the immediate period of scar formation following an intervention. After elution, he said healthy tissue regrowth is then encouraged to cover the stent struts so DES polymers are no longer exposed. Beach said this helps cut irritation along the vessel walls, which should cut the rates of late-stent thrombosis.

Five-year results from the ENDEAVOR-I trial data showed target lesion revascularizations (TLR) stop increasing at three years. Endeavor is at TLR rates of 7.2 percent in years three and four of the study, while longer-eluting stents showed rates of 9.2 percent. Randomized controlled trials of other drug-eluting stents show a continued increase in TLR, reducing the durability of benefit. The ENDEAVOR-I TLR plateau is replicated on a larger scale in ENDEAVOR-II trial, the device’s pivotal study. In the ENDEVOR II Trials Beach said Medtronic hopes this lower rate continues or drops further in the years to come to help justify the short drug elution.

For those who would rather stick with a long-eluting stent, Beach said Medtronic offers the Endeavor Resolute in Europe now, which uses a longer-eluting polymer. Beach said the Resolute will likely have FDA approval by 2012.

In the RESOLUTE IDE trial, only two patients required repeat procedures – a 1.5 percent rate of TLR at two years following implant, according to data released at TCT 2008. There were no instances of stent thrombosis among the 130 study subjects – all of whom received an Endeavor Resolute DES – through 24 months of follow-up.

Two-year results from the ENDEAVOR-IV clinical trial shows the Endeavor is associated with statistically fewer heart attacks than Boston Scientific’s Taxus DES, Medtronic said. Martin B. Leon, M.D., founder and chairman emeritus of the Cardiovascular Research Foundation and principal investigator of ENDEAVOR-IV, presented the results at TCT 2008.

“Through two years of follow up in the ENDEAVOR-IV clinical trial, the Endeavor drug-eluting stent has proven to be statistically safer than Taxus on the important measure of myocardial infarction, and no different in terms of efficacy as measured by the need for repeat procedures,” said Dr. Leon.

In ENDEAVOR-IV, only one of the Endeavor patients out of 742 experienced a very late stent thrombosis, compared to six of the Taxus739 patients.


What’s Next?

There was a lot of information presented at TCT on bioabsorbable stents. Abbott is developing drug-eluting stents using a bioabsorbable polymer coating, on which the drugs they elute is imbedded. By removing the polymers, Abbott hopes to eliminate the inflammation of vessel walls they cause, which should help eliminate in-stent thrombosis. Abbott hopes to have CE Mark for this stent by 2012 and FDA approval sometime afterwards.

Abbott announced two-year data from 30 patients in its ABSORB clinical trial, demonstrating its bioabsorbable DES successfully treated coronary artery disease and was absorbed into the walls of treated arteries within two years, leaving behind blood vessels that appeared to move and function similar to unstented arteries. Patients followed out to two years experienced no stent thrombosis and no new major adverse cardiac events.

Cordis showed off its new works-in-progress stent technology that uses struts covered in holes. Current DES stent technology takes bare metal stents and covers them in a polymer to hold anti-growth drugs to the superstructure. Cordis said the new reservoir eluting stents (RES) will eliminate the need for this surface coating and instead the drug/polymer mixture will be inside hundreds of tiny holes along the struts. Cordis said it wants to use a bioresorbable matrix so no polymers are left behind after about 90 days. The company said it could program the stent reservoirs for single drug release or multi-drug release on one or both sides of the struts.

A similar stent system has also been developed by Conor Medsystems, which started enrolling patients in March for its first clinical trial in Europe.

Mirviss said Boston Scientific’s third-generation stent, the Taxus Element, is entering clinical trials. The new stent uses a platinum chromium scaffold, which is supposed to be more flexible, stronger and easier to see in fluoro images than Boston’s previous generations of stainless steel and cobalt chromium stents.

Another issue to watch is the expiration of Abbott’s patent on its rapid exchange (RX) delivery system, the most widely used type of delivery system because it provides physicians additional flexibility to work as single operators during stent procedures. Medtronic’s sent must be delivered on an over-the-wire system that is not compatible with RX. Medtronic is already planning to launch its own versions of the RX based delivery system after the patent expires, which is supposed to be on Oct. 29.

However, Abbott has already filed for a one-year patent extension, which was temporarily granted Oct. 17 by the U.S. Patent and Trademark Office. A decision is still pending on Abbott’s request to extend the patent until 2011 to account for time it took to develop and get FDA approval for its Xience stent, which uses the system.

October 2008