CD&D National Editor

Ever since the initial identification of problems with drug-eluting stent (DES) technology, the race has been on to develop solutions and alternatives, with a focus on some of the features of DES which may produce thrombosis that is, blood clotting that is often more serious in DES use. Still unknown is the source of these thrombotic events: the particular drug used, the polymer to attach drug to stent, the stent itself, or some combination of these as the possibilities.

Focusing on eliminating one of these possible culprits, the polymer, is MIV Therapeutics (MIVT; Atlanta). MIVT made a presentation at the BMO Capital Markets 2008 Focus on Healthcare Conference in New York in early August, reporting "excellent" safety and efficacy results at 12-month clinical follow-up for all 15 patients in its VESTASYNC I Trial. The trial is a first-in-man (FIM) study looking at the company's VESTAsync polymer-free DES.

In addition, the company reported the use of intravascular ultrasound and quantitative coronary angiography (QCA) in examining all of these patients at nine-month follow-up. This examination showed no difference from the safety and efficacy data on 11- and 12-patient nine-month data presented at the annual meeting of the American College of Cardiology (Washington) in March.

The report at that meeting was that at nine-month follow-up, late loss in a cohort of 11 patients implanted with the VESTAsync was 0.37 mm, and no late thrombosis or major adverse coronary events were reported.

Dr. Mark Landy, president/CEO of MIVT, told Cardiovascular Devices & Drugs that the report at the BMO conference marked the close-out of the one-year "invasive" phase of the trial, referring to the invasive nature of the catheter procedure necessary to evaluate healing at the stent site. The trial will proceed for another year in a "clinical" phase, meaning either in-office or telephonic evaluation of the status of the patients in the trial. Besides expressing general satisfaction with the report, suggesting strong product progress, Landy said, "The most interesting thing is that most of the patients have been off Plavix for at least eight months," a fact suggesting a game-changing opportunity for DES technology and for MIVT.

The need to put DES-implanted patients on the anti-coagulant Plavix has been a complicating factor in the use of these devices. Many of the cases of thrombosis have been associated with patients not being prescribed an anti-coagulant, or failure of patients to be compliant with the drug regimen, generally required up to a minimum of one year, and backed by a strong recommendation from the FDA.

Additionally, given the drug's high cost, the need for the anti-coagulant regimen has been an economic barrier to DES use.

Landy said that following implantation with the VESTAsync the patients were prescribed Plavix for four months and then, following the invasive assessment, for one additional month, and then taken off. "Clinically [the patients] were doing well and we were able to see how the stent was healing. We were able to get a qualitative and quantitative understanding of how the healing process was going," he said.

The avoidance of a polymer in the company's stent is made possible by MIVT's development of new coating systems. In particular, it has developed a coating based on hydroxyapatite (HAp), an organic material which the company says has demonstrated safety and biocompatibility in vivo. This coating, MIVT says, protects surrounding tissue from potentially harmful interactions with bare-metal stents.

The presentation at the BMO conference followed the company's report in late May that it had begun enrolling patients in a registration trial of the VESTAsync polymer-free DES and that it had "accelerated" the timeline for this effort, called VESTASYNC II. VESTSYNC II will compare the use of the VESTAsync nano-porous HAp-coated DES (in 90 patients), with the VESTAcor (in 30 patients), the company's nanoporous Hap-coated stent, which contains no drug. The primary endpoint is late lumen loss as measured by quantitative coronary angiography at nine months. Secondary endpoints will include major adverse cardiac events and volumetric obstruction.

VIMT said it expects that the results of this trial will be the basis for a regulatory foiling in Europe and anticipated submission to the FDA. Landy told CD&D that the potential timeline for submission to the FDA has not been established. The company says the coating also could be used in other implantable devices that could benefit from "highly customizable drug-release profiles."

The company has developed a research agreement with the University of British Columbia (Vancouver, British Columbia) and has received a government grant for its research program on the "Development of Novel Drug-Eluting Composite Coatings for Cardiovascular Stents," under the Canadian National Research Council-Industrial Research Assistance Program.

MIVT's intellectual property portfolio includes patents held by the university, from which it has obtained exclusive licenses. Key patent applications have been filed in various countries, other than the U.S., it says.