Evaluation of Endothelial ProGenitor Cell Capture Sirolimus-Eluting Stent by Optical Coherence Tomography: the COMBO Stent 36-months Clinical End-point Extension Study (EGO-COMBO Clinical End-point Extension Study Beyond 36 Months)

The Genous Stent (the EPC Capture R-stent, OrbusNeich Medical Inc., Fort Lauderdale, FL) is commercially available and has been used extensively in standard coronary intervention in the treatment of more than 200 patients with critical coronary stenoses at Queen Mary Hospital. The COMBO Stent (OrbusNeich Medical Inc., Fort Lauderdale, FL) is an improved version of the Genous Stent and is now widely available for clinical use in all Hong Kong hospitals. To date, more than 300 patients in Queen Mary Hospital have received the COMBO stent as treatment for their coronary artery disease, and all of them remained stable clinically.

The Genous Stent is a bio-engineered 316L stainless steel coronary stent with a biocompatible coating having specific CD34 antibody on the inner surface. CD34 is a surface antigen present on circulating endothelial progenitor cell (EPC). It will be bonded to the CD34 antibody, resulting in capturing of the EPC onto the stent surface and differentiation into endothelial layer. Animal model has demonstrated that a functional endothelial layer could be formed as soon as 24 to 48 hours after Genous stent implantation (1). The HEALING-FIM registry has shown that Genous stent is clinically safe and effective in the treatment of coronary stenosis (2). Recent reports have further confirmed its efficacy in patients with acute coronary syndrome requiring urgent revascularization (3,4).

The COMBO Stent is an improved version of the Genous Stent. The stent delivers a drug called sirolimus to the treated coronary blood vessel. This stent also incorporates a CD34 antibody coating that is designed to promote the healing of the treated coronary artery by catching endothelial progenitor cells from circulating blood as they pass through the stent. These cells are pro-healing and will help the blood vessel wall to heal over the stent more quickly and restore normal tissue function in the stented area. The combination of these two technologies in this new Combo stent is expected to produce even better clinical results, which are published in the REMEDEE Study.

Pre-clinical animal study has already shown the Combo Stent promoted endothelialization and reduced neointima formation, as assessed by both optical coherence tomography (OCT) and histopathology (5). However, such beneficial endothelial coverage as assessed by OCT has never been documented in human subjects, and has been addressed by previous study protocol: the EGO Study (IRB: UW 10-256), EGO-COMBO Pilot Study (UW 10-342) and EGO-COMBO angiographic extension study (UW 12-472). Queen Mary Hospital is currently the single cardiac centre worldwide with such vast experience in using the COMBO stent for percutaneous coronary intervention, together with intracoronary OCT to profile the stent's healing progress and subsequent neo-intimal growth and behaviour.

This current study protocol serves as an extension study to evaluate the long term clinical safety and efficacy of COMBO stent beyond 36 months post-implantation.