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FDA Panel Gives Unanimous Nod to First DES for PAD
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The FDA Circulatory System Devices Panel of the Medical Devices Advisory Committee voted 11-0 for approval of a new paclitaxel-eluting stent designed for the improvement of luminal diameter for the treatment of de novo or restenotic symptomatic vascular disease of the above-the-knee femoral artery.
The self-expanding nitinol stent (Zilver PTX, Cook Medical) is coated on its outer surface with paclitaxel without any polymer, binder or excipient at a dose density of 3 mcg/mm2. If approved, this device would be the first-ever drug-eluting stent available in the United States for the treatment of symptomatic peripheral arterial disease.
The committee unanimously agreed that the stent is safe for use in patients who meet the proposed indication criteria of maximum lesion length of 140 mm per limb and 280 mm per patient. The 11 panel members also voted that there is reasonable assurance that the stent is effective for patients who meet the aforementioned criteria and that the benefits outweigh the risks for use in these patients.
Along with the recommended approval, the advisory committee also discussed whether a post-approval study would be necessary for further safety and efficacy data. The study would require 900 patients and would analyze a non-inferiority comparison of the rate of event-free survival between percutaneous transluminal angioplasty and paclitaxel-eluting stent groups at 5 years. The proposed primary endpoint is event-free survival and the rate of stent fracture, and late stent thrombosis is the proposed secondary endpoint.
Some panel members questioned whether the post-approval study would require a patient population of 900, or if a cohort that large is necessary. Committee member Richard Lange, MD, of the University of Texas Health Science Center, said during the meeting that finishing the 5-year randomized controlled trial would provide enough results for the paclitaxel-eluting stent. “I am less convinced that the long-term data will give us any information we don’t have already,” Lange said. “The current study going on for 5 years probably tells us enough about stent thrombosis.”
John C. Somberg, MD, a panel member from Rush University Medical Center, said a larger study would provide the sponsor with more sufficient data. He suggested continuation of the cohort study, but added that the committee “should advance the idea that there is need for a larger study follow-up that can look for smaller effects, such as stent thrombosis and … whether diabetics have equal benefits with the stent [as] other populations, such as females.”
Other recommended additions for the post-approval study included inclusion of bleeding risks and the addition of more women and patients with diabetes.
Although the FDA is not required to follow the recommendations of advisory committees, it usually does. – by Casey Murphy
Disclosure: The committee members report no relevant financial disclosures.
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I look forward to final FDA approval of the Zilver PTX stent and clinical availability of this device. Although this is not the ‘game-changer’ that DES proved to be in the coronary circulation, the Zilver PTX stent does appear to provide modestly better patency compared with bare nitinol stents in the superficial femoral artery. It is important to keep in mind that lesion lengths in this trial were relatively short and the longest stent available for use in the trial was only 80 mm. We will need further data regarding the safety and effectiveness of Zilver PTX for longer lesions. It will also be interesting to learn more about patterns of restenosis following Zilver PTX.
– John R. Laird, MD
Cardiology Today
Intervention Editorial Board member
Disclosure: Dr. Laird
serves as a consultant/advisory board member for Abbott, Bard, Boston
Scientific, Covidien and Medtronic.