Medtronic's hopes that its drug-coated stent Endeavor (zotarolimus) might escape the safety debate dogging rival products have been dented ahead of a meeting later today to review the marketing application for the device.

Documents published by the US Food and Drug Administration reviewer for Medtronic's dossiers suggest that, at least in the agency's eyes, Endeavor is slightly more likely to be associated with one form of thrombosis than Boston Scientific's Taxus (paclitaxel) device, one of two drug-eluting stents currently on the US market.

The FDA's Circulatory Systems Devices advisory panel ismeeting today and

tomorrow to assess the Endeavor dossier. Thrombosis, death and myocardial infarction were the three main concerns raised at an FDA advisory panel meeting held towards the end of last year to discuss the safety of Taxus and Johnson & Johnson's competing product Cypher(sirolimus).

That meeting was prompted by two studies presented at the World Congress of Cardiology earlier in the year, when two studies suggested that DES were linked to increased risk compared with their bare metal counterparts, although a subsequent pooled analysis from all DES studies found an increase in thrombosis, but no increase in cardiovascular events.

The FDA documents suggest that in one of pivotal studies of the new stent (Endeavor IV), 0.8% of patients who received Medtronic's stent suffered a thrombosis within nine months of implantation - compared with 0.1% of Taxus patients. That study also found that Endeavor did not perform as well as Taxus on a secondary angiographic endpoint.

Although the data had been presented previously, Medtronic shares dipped a little under 3% on the news, but have since staged something of a recovery.

Thrombosis finding 'not significant': Medtronic

For its part, Medtronic believes that the thrombosis finding highlighted by

the FDA is neither statistically-significant nor clinically relevant, and it

is true that 'late' thrombosis - a year or more after implantation - is the

type that cardiologists are most concerned about. The FDA is also

considering whether differences between DES trials in thrombosis rates could be accounted for by differences in the use of antiplatelet therapy.

All that aside, a lot is riding on the outcome of the advisory meeting.

Medtronic's bid to wrest market share from Cypher and Taxus would be made much easier if it could set Endeavor to one side of the ongoing DES safety debate, which has already forced the DES market into a retreat from a height of more than $5 billion a year. Sales of both Cypher and Taxus fell by around a third in the second quarter of 2007 as cardiologists have started to switch patients to older, bare-metal stents.

Medtronic needs a strong endorsement from the FDA panel if it is to see a

good return on its investment in Endeavor, particularly as other potential

competitors, notably Abbott Laboratories with its Xience V product, are also nearing the market in the USA.