Zilver Stent Seen as Welcome Addition to PAD Armamentarium
The US Food and Drug Administration’s (FDA) approval last week of the first drug-eluting stent (DES) for treatment of superficial femoropopliteal artery (SFA) disease expands therapeutic options and has the potential to improve quality of life for patients who otherwise have had few treatment choices.
The agency issued its favorable decision for the polymer-free paclitaxel-eluting Zilver PTX stent (Cook Medical, Bloomington, IN) on November 15, 2012.
In a telephone interview with TCTMD, Christopher J. White, MD, of the Ochsner Heart and Vascular Institute (New Orleans, LA), said that patients with SFA disease can now be treated similarly to those with coronary artery disease and can expect good long-term outcomes.
One lesson learned from the research that went into the approval process is that “these vascular beds are different and require a different level of attention when it comes to intervention,” Dr. White said. “In the past all we’ve been able to do for these patients is take a shot with the bare-metal stent or balloon [angioplasty], and then if [the artery] closed down they went on to surgery. You’re talking about multiple interventions, and amputations in many cases.”
The self-expanding nitinol stent is indicated for improving luminal diameter in de novo or restenotic symptomatic lesions in arteries with a reference vessel diameter of 4 mm to 7 mm and total lesion lengths up to 140 mm per limb and 280 mm per patient. Initially, Zilver PTX will be available in 80 mm lengths in 6 mm and 7 mm diameters, with the possibility of overlapping 2 stents in order to treat longer lesions up to 140 mm. The FDA approval also includes 40 mm and 60 mm lengths, which will be introduced to the United States early in 2013.
Trials Demonstrate High Patency, Stent Safety
Primary data supporting the safety and efficacy of the stent came from a multinational randomized trial as well as the Zilver PTX Registry Study.
In the trial, Michael D. Dake, MD, of the Stanford University School of Medicine (Stanford, CA), randomized 479 patients with symptomatic femoropopliteal disease and Rutherford class 2 or above to treatment with the Zilver stent (n = 241) or balloon angioplasty (n = 238). Among patients assigned to angioplasty, results were suboptimal in 120, and these patients underwent a second randomization to provisional stenting with Zilver PTX (n = 61) or a bare-metal Zilver stent (n = 59). The 2 devices have identical platforms.
At 12 months, the patency rate was higher in the Zilver group compared with balloon angioplasty (83% vs. 33%). Among patients who failed angioplasty and underwent provisional stenting with Zilver PTX, the patency rate was 90% at 12 months vs. 73% for those treated with BMS. At 24 months, event-free survival among those randomized to Zilver PTX in the first round was 86.6%.
In the separate registry study led by William A. Gray, MD, of Columbia University Medical Center (New York, NY), 787 patients with symptomatic above-the-knee SFA disease received 1 or more (up to 4) Zilver stents for a single or multiple lesions. At 12 months, the primary endpoint of survival free from amputation or TLR was 87%. Stent fractures were observed in 1.5% of patients but did not result in any detectable clinical consequences. Among patients with 24-month follow-up, the event-free survival rate was 80%.
In both studies, the most common major adverse event was restenosis requiring additional treatment to re-establish adequate flow in the artery. As part of the approval, the FDA is requiring Cook Medical to conduct a 5-year post-approval study of 900 patients treated with Zilver PTX to further monitor safety and efficacy.
Great, But Why the Wait?
According to Dr. White, the FDA approval “has been a long time coming.” The device received CE Mark approval in 2009 and is available in more than 50 markets outside the United States, he noted.
The delay raises the question of whether the FDA is “conducting [its] business appropriately [or] requiring redundant information in cases like this,” he commented.
“Nothing else really works in the leg. So when you have a device like this that has the promise for advancing the field, which the randomized trials demonstrated, you do wonder why it took so long for this to become available here. There are pathways where the device can be released and data can continue to be collected so that safety signals can be looked for,” Dr. White emphasized. “I don’t think the FDA takes enough advantage of that process.”
Dr. White said the approval of the Zilver stent is meaningful for many clinicians and patients because the rate of limb amputation in SFA patients is high. “Once patients lose a limb, they have rapid loss of function and rapid demise,” he added. “Our efforts in these patients have to be centered on preserving the limb and preserving function and walking ability.”
But approval is only the first hurdle for the new stent, Dr. White said. The next will be pricing and coverage decisions to determine who gets this type of intervention and who does not.
Note: Dr. Gray is a faculty member of the Cardiovascular Research Foundation, which owns and operates TCTMD.
1. Cook Medical. Cook Medical’s Zilver PTX earns FDA approval as first drug-eluting stent in U.S. to treat peripheral arterial disease [press release]. http://www.cookmedical.com/newsDetail.do?id=7733. Published November 15, 2012. Accessed November 19, 2012.
2. US Food and Drug Administration. FDA approves first drug-eluting stent to treat peripheral arterial disease [press release]. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm327068.htm. Published November 15, 2012. Accessed November 19, 2012.
3. US Food and Drug Administration. Brief Summary of the Circulatory System Devices Panel Meeting. http://www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/MedicalDevices/Medical
DevicesAdvisoryCommittee/CirculatorySystemDevicesPanel/UCM275925.pdf. Published October 13, 2011. Accessed November 19, 2012.
- Dr. White reports no relevant conflicts of interest.
- Drs. Dake and Ansel report serving as paid consultants for Cook Medical and global principal investigators for the Zilver PTX clinical trial.