PAX Studies Highlight Polymer-Free DES Success

SAN FRANCISCO, CALIF.—Outcomes from the PAX-A, PAX-B and BI-PAX trials showed superior stent strut coverage and less strut malapposition at 9 months and no stent thrombosis at 12 months for polymer-free DES compared with polymer-based paclitaxel-eluting stents. Researchers also previewed early results of a new preclinical polymer-free DES.

Ricardo A. Costa, MD, of Instituto Dante Pazzanese de Cardiologia in São Paulo, Brazil, presented the PAX results at TCT 2011. PAX-A was a small first-in-man study comparing outcomes for 16 patients assigned to a polymer-free DES (Amazonia PAX, Minvasys)  with those of 15 patients assigned to paclitaxel-eluting stents (Taxus Liberté, Boston Scientific). At 4 months, the polymer-free DES was associated with similar in-stent late lumen loss (0.77 mm vs. 0.42 mm; P=.20) and percent volume obstruction (19.2% vs. 9.3%; P=.08) compared with Taxus Liberté.

In  PAX-B, a multicenter registry of 103 patients, 9-month  rates of cardiac death (0%), any MI (3.9%) and stent thrombosis (0%) remained unchanged from the in-hospital outcomes, though any TLR/TVR increased from 0% in-hospital to 19.7%.

“Overall, there was sustained safety in both studies, including absence of cardiac death or thrombotic events with [the] Amazonia PAX non-polymeric drug-coated stent,” Costa said. “Ongoing studies are evaluating the impact of this technology in the real-world setting.”

Similarly, 12-month outcomes in BI-PAX, a multicenter registry of 101 patients receiving a polymer-free dedicated bifurcation DES, showed a low rate of cardiac death, with no cases of non-cardiac death, MI or stent thrombosis.

“In the per protocol population, binary restenosis rates at 9 months were 13.8% in the main branch and 12.8% in the side branch with overall in-bifurcation restenosis of 18.4%,” Costa said. “Furthermore, cumulative ischemia-driven TLR rate was 9.5%, which was the secondary endpoint.”

In other early results, preclinical device outcomes with the reservoir-based, polymer-free sirolimus-eluting Cre8 stent demonstrated complete and uniform endothelialization at 7 days, and suppression of neointimal proliferation at 30 days was maintained at 90 days with minimal inflammatory response. According to Didier Carrié, MD, PhD, of Hôpital de Rangueil in Toulouse, France, 12-month outcomes from the NEXT trial evaluating Cre8 for endpoints including TLR and late lumen loss are slated to be presented in a late-breaking abstract session Friday morning.