ZOMAXX I: Mixed Results With Zotarolimus-eluting Stent
Zotarolimus-eluting stent achieved noninferiority endpoints, but in-stent late loss increased.
The ZoMaxx zotarolimus-eluting stent (Abbott Vascular Devices) failed to achieve its noninferiority endpoint of in-segment late loss in a comparison with the paclitaxel-eluting Taxus stent, according to Bernard Chevalier, MD, of the Centre Cardiologie du Nord in St. Denis, France.
In a late-breaking presentation, the median 9-month in-segment late loss was 0.29 mm with ZoMaxx (Abbott Vascular Devices) vs. 0.22 mm with Taxus (Boston Scientific). The result exceeded the protocol-specified noninferiority margin of limit 0.25 mm by 0.02 mm, and therefore did not meet the primary endpoint.
In addition, the ZoMaxx stent demonstrated worse results according to several secondary parameters (Table).
Differences in target lesion revascularization (8.0% with ZoMaxx vs. 4.1% with Taxus), target vessel revascularization (8.5% for ZoMaxx vs. 6.6% for Taxus) and target vessel failure (12.6% vs. for ZoMaxx vs. 9.6% for Taxus) were not significant.
The ZoMaxx stent was highly deliverable, with 99% lesion and device success; there was no late-acquired incomplete stent apposition. The stent was shown to be safe, with a low overall rate of stent thrombosis (0.5%) and an absence of late stent thrombosis.
Overall rates of major adverse cardiac events were comparable between the two stents: 12.6% in the ZoMaxx cohort vs. 9.6% in the Taxus cohort.
The ZOMAXX I trial enrolled 401 patients, with 396 eligible for intent-to-treat analysis (199 patients randomized to ZoMaxx and 197 to Taxus).
The results indicate that in-segment late loss may not be an appropriate endpoint in head-to-head trials of drug-eluting stents, said commentator David Cohen, MD, of the Mid-America Heart Institute. Measurements taken to determine late loss are not from the same location and do not reflect the in-stent stenosis that is more indicative of ischemia, resulting in a discordance between clinical and statistical results, Cohen said. Better endpoints for future trials would be in-stent late loss and in-segment percent diameter stenosis.
ZOMAXX I also showed that preclinical testing of drug-eluting stents cannot reliably predict human response. Zotarolimus is similar to sirolimus, with similar elution kinetics, but the stent showed significant differences in inhibition of neointimal proliferation.