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Medtronic's Drug-Filled Stent: First Data
Results Presented at TCT Show Early Vessel Healing, Drug-Elution Without Polymer
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Medtronic's Drug-Filled Stent (DFS) |
October 13, 2015 -- At the current Transcatheter Cardiovascular Therapeutics (TCT) meeting in San Francisco, the buzzwords in stents are bioresorbable, bioabsorbable, vascular scaffolds (not stents) -- all solutions to the problem of leaving a permanent piece of metal (with or without a plastic coating, called a polymer) in the coronary artery: a piece of metal that may cause inflammation, leading to a reclosure of the vessel; an object that also may impede the back-and-forth motion of the artery as the heart beats.
These adverse events are infrequent and have been reduced significantly since the first generation of drug-eluting stents became available over a decade ago. But these late-term events do occur, so device manufacturers and physicians have been working hard at eliminating these final issues.
Abbott decided to take elimination literally and developed the ABSORB Bioresorbable Vascular Scaffold (BVS) which decomposes and is completely gone at about three years. The main idea behind Absorb is that in the long-term, when the scaffold has disappeared, vasomotion of the affected artery is back to normal, unrestricted by a metal "cage." Also, assuming several stents/scaffolds are placed, Absorb would avoid the "full-metal jacket" situation, where so much metal has been placed that bypass surgery is no longer possible. At yesterday's TCT meeting, one and two years results of ABSORB III and II were presented, along with ABSORB CHINA. The results showed "non-inferiority" with Abbott's 2nd generation drug-eluting metallic stent, considered one of the gold standards of current stent technology. In med-speak, that means that, while the numeric results were not as good, they were not below a pre-specified level: not equivalent to Xience, less good, but not so much as to be called "inferior." Proponents of the technology point out that data from beyond three years is needed to see the benefit of having no residual device in the artery. Also, the implantation technique differs from bare metal stents, because of the thicker struts and other characteristics. But these trials were done with a first generation device. So, stay tuned.
A second strategy is one used by Boston Scientific for its SYNERGY stent, which sports a biodegradable polymer that is bioresorbed in 3-4 months. At this point, the Synergy becomes a bare metal stent, shortening the one year or more period of dual antiplatelet therapy currently recommended for drug-eluting stents with permanent polymers. Again, long-term data will be necessary to determine if these new types of stents produce better outcomes at three, four, and five years.
A third, new, and novel configuration is one that Medtronic started testing back in March. Called a DFS ("drug-filled stent") it is both a drug-eluting stent AND a bare metal stent, utilizing the same stent construction that Medtronic currently uses in its Resolute Integrity and Onyx stents. The stent is fashioned from a single strand of metal that can have several "inner cores." In the DFS, the drug is contained in a reservoir, inside the stent, and slowly eluted through small laser-drilled holes in the metal outer core. So the restenosis-suppressing drug has a chance to work, but then what is left in the artery is a very thin-strutted high performance bare metal stent, which presumably lowers the chances for inflammation and vascular remodeling, something sometimes seen with polymers in drug-eluting stents.
The initial data from the RevElution DFS trial was released yesterday at the TCT. Although this was just a small pilot trial that will ultimately enroll just 100 patients, the results of the first cohort of 6 cases were encouraging. On high resolution OCT imaging, the DFS showed fast, well-controlled strut coverage (over 90% at one month) which allows for faster healing of the endothelium, reducing the need for dual antiplatelet therapy and the risk of stent thrombosis. Additionally there was a low rate of malapposed struts (2%), which dropped by half within one month post-procedure, and neointimal hyperplasia formation was minimal. This is, of course, very early data in a small patient cohort. Further investigation is currently underway.
The press release from Medtronic, Inc. follows:
Medtronic Drug-Filled Stent Shows Promising Initial Results Following First Implants
Presented for the First Time at TCT, Early Results from the RevElution Trial Demonstrate Early Vessel Healing and Controlled, Polymer-Free Drug Elution in Patients Treated with the Novel Next-Generation Stent
October 12, 2015 -- Dublin and San Francisco -- Medtronic plc (NYSE: MDT) unveiled today new data from the first implants of its novel Drug-Filled Stent (DFS) at the Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium. The early results from an initial subset of patients in the RevElution Trial show that the DFS achieved rapid and well-controlled stent coverage. The unique DFS is designed to eliminate potential drawbacks experienced with bioabsorbable polymers and polymer-free technologies, such as inflammation due to polymer degradation, and uncontrolled drug release in the absence of a polymer.
"The novel DFS truly represents an innovative stent platform with advanced stent manufacturing to optimize clinical performance without the need of a polymer," said Stephen Worthley, professor at the Royal Adelaide Hospital in Adelaide, Australia and co-principal investigator of the DFS trial who performed the first implants in the study and presented the data at TCT. "These patients implanted with the DFS have shown very promising early outcomes of strut coverage and healing that indicate the new platform may provide many clinical benefits, including shorter DAPT duration, and we look forward to evaluating how well the stent continues to perform throughout the trial."
The Optical Coherence Tomography (OCT) data from the Trial demonstrate an early healing profile with an average of 90 percent strut coverage (new cell growth over stent struts) at one month, with a low rate of malapposed struts (2 percent) across the six patients analyzed. The rate of malapposed struts dropped by 50 percent within one month post-procedure, further demonstrating the stent's ability to allow for rapid healing within the vessel. Importantly, the data also showed minimal neointimal hyperplasia (NIH) formation.
The DFS is built on the proven platform of the Resolute Integrity(TM) DES with Continuous Sinusoid Technology (a unique Medtronic method of stent manufacturing that forms one single strand of wire into a sinusoidal wave enabling a continuous range of motion), as well as the next-generation Resolute Onyx(TM) DES with CoreWire Technology that allows it to have a denser core metal surrounded by a cobalt alloy outer layer for thinner struts with enhanced radiopacity (visibility during imaging).
The new DFS features a novel tri-layer wire design, which allows the inner sacrificial layer to become a lumen continuously coated with drug. The drug (sirolimus) is contained on the inside of the stent and is released from a single continuous inner lumen through multiple laser-drilled holes on the abluminal side (outer surface) of the stent. This allows for a controlled and sustained polymer-free drug elution over a desired period of time directly into the arterial wall thereby potentially avoiding chronic inflammation and adverse vascular responses. In patients with complex lesions, containing the drug on the inside of the stent protects the coating to reduce concerns related to coating durability during tracking.
"Through our collaboration with interventional cardiologists from around the world to advance our coronary portfolio together, we believe the drug-filled stent represents a significant breakthrough in stent design and engineering that helps address current and next-generation technology challenges," said Jason Weidman, vice president and general manager of the Coronary and Renal Denervation business, which is part of the Cardiac and Vascular Group at Medtronic.
The global DFS study is underway at multiple sites in geographies including Australia and Brazil. The study will enroll 100 patients and will evaluate late lumen loss as measured by quantitative coronary angiography. The Drug-Filled Stent is available for investigational use only outside of the United States.
In collaboration with leading clinicians, researchers and scientists worldwide, Medtronic offers the broadest range of innovative medical technology for the interventional and surgical treatment of cardiovascular disease and cardiac arrhythmias. The company strives to offer products and services that deliver clinical and economic value to healthcare consumers and providers around the world.
About Medtronic
Medtronic plc (www.medtronic.com), headquartered in Dublin, Ireland, is among the world's largest medical technology, services and solutions companies - alleviating pain, restoring health and extending life for millions of people around the world. Medtronic employs more than 85,000 people worldwide, serving physicians, hospitals and patients in more than 160 countries. The company is focused on collaborating with stakeholders around the world to take healthcare Further, Together.
Any forward-looking statements are subject to risks and uncertainties such as those described in Medtronic's periodic reports on file with the Securities and Exchange Commission. Actual results may differ materially from anticipated results.
Reported by Burt Cohen, October 13, 2015 |
