Cook Medical’s first-of-a-kind Zilver PTX percutaneous paclitaxel-eluting peripheral stent received unanimous and enthusiastic support from the FDA’s Circulatory System Devices panel last week.

The Oct. 14 panel voted 11-0 that the device demonstrated a reasonable assurance of safety and effectiveness compared to standard treatment of percutaneous transluminal angioplasty, and that the overall benefits of the device outweigh the risks for patients with peripheral vascular disease affecting the superficial femoral artery.

“I would like to really applaud the sponsor, not only for your excellent presentations, but for bringing a technology forward that will not just benefit, but greatly benefit and enhance, the health of people who are troubled by a very compelling disorder,” said Clyde Yancy, the panel chairman and chief of cardiology at Northwestern University Fienberg School of Medicine.

“I’ve been to many panel meetings, and this is one of the clearer, well-put together meetings,” agreed Valluvan Jeevanandam, chief of cardiac and thoracic surgery at The University of Chicago Medical Center.

If FDA approves the stent, it would be the first drug-eluting stent in the U.S. indicated to treat superficial femoral arteries. Cook gained a CE mark in June 2009, and the stent is available in 48 countries around the world. Current bare-metal stents on the U.S. market approved for use in femoral arteries are Bard’s LifeStent and W.L. Gore’s Viabahn .

The Zilver PTX would be the first drug-eluting stent in the U.S. indicated to treat superficial femoral arteries. (Photo: Cook Medical)

The Zilver PTX would be the first drug-eluting stent in the U.S. indicated to treat superficial femoral arteries. (Photo: Cook Medical)

The standard of care for femoral artery disease is angioplasty, with provisional stenting as a backup. But Cook’s pivotal study assessed its drug-eluting stent as a component of first-line angioplasty therapy.

Cook Medical estimates that 120,000 superficial femoral artery stenting procedures take place in the U.S. every year. The peripheral stenting market will continue to grow as the baby-boom generation ages and diabetes prevalence rises, contributing to an increased rate of peripheral artery disease, says Rob Lyles, VP and global leader of Cook’s Peripheral Intervention business unit. (See “ Also see "Cook Medical Makes Progress In Peripheral Stent Space" - Medtech Insight, 24 January, 2011. ” – “The Gray Sheet” Jan. 24, 2011.)

Both the panel and FDA agreed that the firm’s randomized, controlled trial met its primary safety and efficacy endpoints. The 479-patient trial compared treatment of restenotic lesions of the femoropopliteal artery of up to 14 centimeters in length using the Zilver PTX stent against standard of care of angioplasty and provisional bare-metal stenting.

Cook’s PMA was primarily supported by one-year results from the clinical trial, which showed a 90.4% event-free survival rate, compared to 82.6% in patients randomized to standard angioplasty, and an 83.1% patency rate.

Cook’s two-year trial data also showed an 86.6% event-free survival rate, compared to 77.7% survival for patients randomized to angioplasty, and 81.2% primary patency for Zilver PTX patients.

Additionally, Cook conducted an overseas registry of 787 subjects with restenotic lesions of the femoropopliteal artery with no restriction of lesion length.

The panel supported the sponsor’s proposed indication for use statement, but inserted that the Zilver stent should be indicated to treat de novo or restenotic symptomatic lesions in “native” vascular disease. The sponsor agreed with the proposed addition.

The advisors recommended that the only listed contraindication on labeling should be for pregnant women. The panel also suggested that three precautions be added: a low risk of stent fracture for which there is uncertain clinical significance; the lower likelihood of successful patency in longer lesions; and a warning to patients with bleeding disorders who are unable to take anti-platelet therapy.

Post-Approval Study Triggers Some Debate

While the panel agreed that the sponsor’s pre-market data was very strong, they debated the appropriate criteria for the firm’s proposed post-approval study.

The sponsor has outlined a five-year follow-up study of patients who were enrolled in the pre-market randomized trial. But FDA argues that the proposal does not include enough patients to evaluate the incidence of rare events, such as stent fracture and late stent thrombosis. A total of 900 patients would be needed, officials said.

This would require the sponsor to enroll additional subjects and potentially go back to the patients included in the global registry to gain informed consent to collect follow-up data.

The majority of the panel agreed that more patients should be enrolled in the post-approval study, preferably patients based in the U.S. The advisors also recommended that the registry patients should be re-consented.

Additionally, they recommended that the post-approval study should track the incidence of bleeding in patients, and specifically follow the results of female and diabetic patients.

However, there should be “no overtly focused effort to specifically recruit women or diabetic patients,” Yancy clarified.

By Rebecca Kern

Cook’s Zilver PTX Peripheral Drug-Eluting Stent Sails Through FDA Panel

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