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WASHINGTON -- The Orsiro stent -- a hybrid sirolimus-eluting device featuring a biodegradable polymer -- did not definitively match durable-polymer stents in terms of efficacy for chronic total occlusions (CTOs), according to a late-breaking trial presented at the annual meeting.

Nine months after implantation, the Orsiro failed to meet criteria for non-inferiority versus the everolimus-eluting Xience Prime or Xpedition stents for in-segment low late loss (0.13 mm versus 0.02 mm, P=0.11 for non-inferiority). In-stent late lumen loss was more comparable between groups (0.12 versus 0.07, P=0.52), according to , of St. Antonius Hospital in the Netherlands, and collaborators of the PRISON IV randomized trial.

Their study was simultaneously published online in .

These numbers don't advance the position of biodegradable polymers any further, said , of University of Texas Southwestern Medical Center in Dallas, a panelist at a TCT press conference. "The study just reinforces that we already have a high performance platform."

Yet some expressed reluctance to close the book on the Orsiro and other hybrid stents.

"The effect has to be seen long-term," said fellow discussant , of Wellmont CVA Heart Institute in Kingsport, Tenn. "Before we abandon this therapy, these were good results -- it's just that the other one was so good."

"This raises the issue of how we define non-inferiority. The performance of both devices was very good," agreed , of New York-Presbyterian/Columbia University Medical Center, during the session.

Twelve-month clinical outcomes indicated higher rates of binary restenosis with the Orsiro (8.0% versus 2.1% versus Xience, P=0.028). Its 60-micron strut thickness did not appear to confer any advantages, given that groups shared similar odds of:

• Reocclusion (2.2% versus 1.4%, P=0.68)
• Clinically indicated target lesion revascularization (9.2% versus 4.0%, P=0.08)
• Target vessel failure (9.9% versus 6.6%, P=0.35)
• Stent thrombosis (0.7% versus 0.7%, P=1.0)

Teeuwen's investigation included 330 patients who were treated at eight European centers. Participants were randomized to receive Orsiro or Xience stents for their CTOs. Baseline characteristics were well-matched with the exception of a higher J-CTO score among everolimus-eluting stent recipients (2.0 versus 1.8 for Orsiro, P=0.03).

"We need to focus on CTOs with our stent technology. We need to focus on treating a really large plaque burden requiring a large radial force while using thin struts to avoid in-stent restenosis," said Teeuwen in face of PRISON IV's disappointing findings.

Collagenase Aids in CTO Tx

In a separate study of another technology for CTO treatment, a collagen-busting enzyme injected the day before percutaneous coronary intervention (PCI) of a CTO helped wire crossing and was associated with a favorable safety profile, according to another TCT late-breaker.

Phase 2 data for the TOSCA-5 study showed that successful wire crossing rates were similar whether patients got MZ-004 collagenase or a placebo. Soft-wire crossing, however, was noted more frequently with MZ-004 collagenase (0% for placebo versus 17% for 900 mcg dose and 29% for 1,200 mcg dose, P=0.03), reported , of St. Michael's Hospital in Toronto.

cleaves human collagen at multiple sites. The multicenter TOSCA-5 trial randomized 75 CTO patients undergoing PCI to placebo or one of the two MZ-004 collagenase doses in a 1:2:2 ratio.

PCI was equally likely to be successful between control and experimental arms (64% for placebo versus 60% and 65% with the two drug doses), and there were no significant differences between groups in terms of imaging time, radiation dose, or contrast volume.

"MZ-004 collagenase pre-treatment appears to enable antegrade soft wire crossing of chronic coronary occlusions," Buller concluded, adding that it "may increase overall antegrade wire crossing rates."

Safety data looked promising for the collagenase, with no repeat revascularizations, MIs, or deaths within 30 days. Recipients of placebo, on the other hand, exhibited a 7% rate of MI.

Peri-procedural myonecrosis occurred in 13% of the placebo, 7% of the low-dose collagenase, and 13% of the higher-dose treatment groups. These events were all associated with side branch occlusion or -- with a 1,200 mcg dose combined with stiff wires -- perforation. No differences were observed with perforation or significant effusion among patients.