Barcelona, Spain, 31 August 2009: Drug-eluting stents (DES), which slowly release medication to inhibit the build-up of scar tissue, have proved very successful in preventing restenosis (renarrowing) of stented coronary arteries. However, several studies have shown persistent risk of blood clot formation inside DES over a longer time period after implantation than observed with bare metal stents. Additionally, recent serial angiographic studies have reported that scar tissue accumulation can be seen up for up to two years after implantation of DES. There is increasing evidence that the risk of both late in-stent blood clot and neo-intimal scar formation may be caused by a delayed healing process or a persisting inflammatory response to the permanent polymer used to control drug-release from the surface of stent.
The ISAR-TEST-4 study is a randomised trial designed and conducted at two tertiary referral cardiology centres – Deutsches Herzzentrum and 1. Medizinische Klinik, Klinikum rechts der Isar, Technische Universität, both in Munich, Germany – with the aim of assessing the efficacy and safety of a biodegradable polymer DES in a non-selected cohort of patients undergoing PCI in de novo native-vessel coronary lesions. First results indicate that safety and efficacy outcomes at one year are comparable with those of permanent polymer-based drug-eluting stents
Patients were randomly assigned to receive either a biodegradable polymer DES (n = 1299) or a permanent polymer DES (Cypher, n = 652, or Xience, n = 652). The primary endpoint was a composite of cardiac death, myocardial infarction (MI) related to the target vessel, or revascularisation related to the target lesion (TLR) at one year.
The biodegradable polymer DES was developed in the setting of the Individualized Drug-Eluting Stent System to Abrogate Restenosis (ISAR) project. The stent platform consists of a sand-blasted, stainless-steel stent that is coated on-site with a mixture of rapamycin, biodegradable polymer, and shellac resin (a biocompatible resin widely used in the coating of medical tablets).
Primary endpoint results showed that the biodegradable polymer DES was non-inferior to the permanent polymer DES (a rate of 13.8% vs 14.4%, Pnon-inferiority 0.005; RR 0.96, 95% CI 0.78-1.17, Psuperiority=0.66). No significant difference was observed between the biodegradable and permanent polymer DES according to cardiac death or MI (6.3% vs 6.2%, P=0.94), TLR (8.8% vs. 9.4%, P=0.58) or stent thrombosis (definite/probable: 1.0% vs. 1.5%, P=0.29). Nor was there a significant difference in subgroup analysis of the biodegradable polymer DES versus the individual permanent polymer DES arms.
Investigator Dr Julinda Mehilli from the Deutsches Herzzentrum in Munich, said: “The one-year clinical efficacy of the biodegradable polymer rapamycin-eluting stent is comparable to permanent polymer-based DES. These results now provide a framework for testing the potential clinical advantage of biodegradable polymer DES over the medium- to long-term.”