Efficacy and safety of a novel nano-porous polymer-free sirolimus- eluting stent in pigs

Background Drug-eluting stents represent a major advance in interventional cardiology. However, the current drug- eluting stents have significant limitations. One of the major problems is very late stent thrombosis, which is likely caused by inflammation and a hypersensitivity reaction related to a polymer on the stent. A polymer-free sirolimus-eluting stent with a unique nano-porous surface has been developed. This study aimed to evaluate this novel polymer-free sirolimus- eluting stent for its efficacy and safety in a pig model. Methods Stents were directly coated with sirolimus （a drug concentration of 2.2 μg/mm2 on the stent surface）. The polymer-free sirolimus-eluting stents （PFSES） were compared to standard polymer-coated sirolimus-eluting stents （PCSES） and bare-metal stents （BMS） in 18 pigs. Results At one month the degree of neointimal hyperplasia was similar between the two sirolimus-eluting stent groups and was significantly less compared to BMS （（1.93±0.51） mm2, （1.57±0.69） mm2 vs. （4.45±1.05） mm2, P 〈0.05）At three months, PFSES maintained the low level of neointima （（2.41±0.99） mm2 vs. （4.32±1.16） mm2, P 〈0.05）, whereas PCSES had developed significant neointimal proliferation similar to BMS. The inflammation level was significantly higher in PCSES when compared with BMS three months post-implantation （2.50±0.55 vs. 0.83±0.75, P 〈0.05） whereas PFSES showed a low level of inflammation comparable to PCSES （1.33±0.52 vs. 2.50±0.55, P 〈0.05）. Conclusion The PFSES is effective and safe. and appears to be suoerior to standard PCSEs.