FDA Approval of the Zilver PTX Drug-Eluting Stent: An Interview with Gary M. Ansel, MD

In follow-up for the 2012 VEITHsymposium, Vascular Disease Management spoke about the recent FDA approval of the Zilver PTX drug-eluting stent (Cook Medical) for treatment of peripheral artery disease with Gary M. Ansel, MD, who, along with Michael Dake, MD, was co-principal investigator for a randomized trial that studied the Zilver PTX stent.

Q: Could you please describe the condition and patients that the newly approved stent is able to treat?

A: The Zilver PTX is a chemically covered superficial femoral and proximal popliteal artery stent typically used for patients with atherosclerotic peripheral vascular diasease that have symptoms of claudication or rest pain. 

Q: What had the limitations been for vascular specialists who were not able to use this stent in the United States?

A: The current limitation for endovascular specialists in the United States is that most of the procedures that we do are associated with a significant risk of restenosis, especially in this vascular bed, and depending on the particular artery characteristics, such as length of blockage or total occlusion, those restenosis rates can range from 30% up to 80% with current technologies.

Q: What advantages does the Zilver PTX stent offer over methods used to date?

A: Zilver PTX offers reduction in the number of patients who need to have a repeat procedure up to 3 years. There have been two trials; one was the Zilver PTX trial in the United States and Japan, for the typical shorter superficial femoral artery lesions seen in device approval studies in the United States, though it was a randomized trial comparing the Zilver PTX stent to optimal angioplasty. 

There was also a much larger registry trial that was done in Europe that looked at the potential for generalization of the usage of the stent and more typical and complex disease such as longer lesions, restenotic lesions, more heavily calcified lesions and such. 

And the European randomized trial has shown that at 3 years we reduced the need for repeat procedures significantly so that less than 30% of patients at 3 years needed another treatment. This is quite different than what we’ve had even at a year for most of the current technologies. 

Q: What is the most important point about this stent for vascular specialists to know?

A: The first thing is that the need for repeat procedures, which we call TLR or treatment of lesion restenosis, is much lower than we’ve seen in previously utilized trials. This is one of the few randomized trials that really showed this. 

One of the other things we noticed in an early look at trial data is that the pattern of restenosis appears to be much more focal or less diffuse than the typical bare metal stent restenosis, and this may allow for simpler retreatment even when it does need to be done. 

Also, patients may be less symptomatic if the disease that returns is less complex or less diffuse. This should allow for higher flow rate, like our bypasses, where if we get a blockage before it closes it is usually just the one at the end, and that allows for a lot more flow than if there’s a blockage throughout a bypass graft. So, the treatment appears to be associated with less retreatment, and the process of retreatment when it does occur seems to be a much more simple one. 

The results from the randomized trial also seem to be very similar to the registry done in Europe with much more complex lesions. If you lay the curves on patency and repeat procedures on top of each other from the two trials there doesn’t appear to be too much difference.  

Another nice benefit that we found in the trial is that diabetics did not seem to have a higher restenosis rate than nondiabetics, it was equally effective in diabetics and nondiabetics, which is a very exciting finding for this trial as well. 

Q: You spoke about the Zilver PTX stent at VEITHsymposium in November. So, it must have been a nice surprise to hear of the FDA approval while the conference was under way.  

A:  Yes; we’d been waiting for that approval for a long time, so it was a nice surprise. We were wondering if it was ever going to come about. We’re one of the last developed countries to get approval even though we did the trial, so we’re very excited about the agency giving us approval to use the device in our patients and are excited about getting it in our hands. 

Like any approval process it will probably lead to some conflict because no company can supply all of the demands of the physicians when there’s been a delay in getting approval, so I’m sure Cook Medical will be rolling this out over the next 6 to 9 months to get as many physicians access to the device as possible. 

Q: Is there anything else you’d like to add? 

A:  One of the important questions that comes up is whether antiplatelet therapy will be necessary for a year, like we do with coronary stents, because that’s always a source of angst among physicians, who ask, “If I put this in, am I relegating my patients to a need for antiplatelet therapy for a year?”  That’s what’s nice and different about the peripheral vasculature:  the trial only required antiplatelet therapy for 2 months, so there doesn’t seem to be a need for a year-long antiplatelet therapy to maintain its patency.  

Gary M. Ansel, MD, is the Director for the Critical Limb Care Center at Riverside Methodist Hospital in Columbus, Ohio, and Assistant Clinical Professor of Medicine in the department of internal medicine at the University of Toledo Medical Center (formerly Medical College of Ohio). 

Dr. Ansel received his medical degree from the Ohio State University where he also completed a postgraduate research fellowship in cardiology. Dr. Ansel received post-fellowship training in peripheral-vascular intervention at the Ochsner Clinic in New Orleans. 

Dr. Ansel was previously a member of the Peripheral Vascular Committee for the American College of Cardiology, and is a member of numerous professional societies. He has contributed to several journals such as the New England Journal of Medicine, Circulation, Journal of Endovascular Therapy and the American Journal of Cardiology. 

Dr. Ansel has also contributed numerous book chapters. Dr. Ansel is past president and a founding board member of the Vascular InterVentional Advances Conference (VIVA), which is a non-profit organization dedicated to the education and research of vascular disease. 

Dr. Ansel reports receiving royalties not related to this product as well as consultancy to Cook Medical. 

Editor's note: For more on the 3-year results of this trial, see the video interview with co-principal investigator Michael Dake, MD.