Preclinical evaluation of a novel abluminal surface coated sirolimus eluting stent with biodegradable polymer matrix

BACKGROUND: Second generation of drug eluting stents (DES) has attempted to improve safety using abluminal sirolimus drug delivery with biodegradable polymers matrix. The present preclinical study was designed to investigate the safety and efficacy profile of Abluminus™ stents (SES). This is a new coronary stent with sirolimus and biodegradable polymer matrix coated on abluminal stent and balloon surface. METHODS: SES were compared with two controls: bare metal stent (BMS) and BMS + polymer coated stents (PC). All devices (40 stents) were implanted in porcine coronary arteries with primary endpoint of endothelialization at 7 days and subsequent histological and morphometric evaluations at 7, 30 and 90 days. RESULTS: Early endothelialization at seven days was complete in all stents. Histology at 30 days revealed minimum inflammation in all groups and increased at 90 days in PC group while it was absent at 180 days. Thirty day morphometry showed significantly reduction of neointimal area in Abluminus™ (SES 0.96±0.48 mm(2); BMS 1.83±0.34 mm(2); PC 1.76±0.55 mm(2); P<0.05); after 90 days neointimal area was 1.10±0.54 mm(2) for SES; 1.92±0.36 mm(2) for BMS; and 1.94±0.48 mm(2) for PC; P<0.05). Neointimal thickness at 30 and 90 days respectively was 0.15±0.07 and 0.18±0.10 mm for SES, 0.57±0.08 and 0.61±0.09 mm for BMS and 0.52±0.09 and 0.59±0.08 mm, P<0.001 for PC group. CONCLUSIONS: The most significant experimental evidence appears to be earlier endothelialization at 7 days for SES which led to safety of the device. Efficacy of the device was also observed by a reduced neointimal thickness and minimized inflammatory score at all follow-ups. Termination of antiplatelet at 30 days has not shown any further complications. Polymer thickness was almost in negligible amount at 180 days with no inflammation

Excipient:Drug Dose Determination for Neointimal Hyperplasia as Assessed by Optical Coherence Tomography and Histopathology in Porcine Coronary Arteries after Sirolimus-Eluting Balloon Employment

ABSTRACTBackgroundMagic Touch™ is a sirolimus-based nano-carrier eluting balloon. This study aimed to find the excipient:drug ratio with the greatest capacity to inhibit neointimal proliferation 28 days after the use of this balloon and following bare-metal stenting in porcine coronary arteries.MethodsFourteen domestic pigs who received coronary bare-metal stent implants followed by dilation (60seconds) using balloons with excipient:sirolimus ratios of 1:1, 0.5:1, 0.25:1, and 1:0 or a control balloon were evaluated. After 28 days, neointimal hyperplasia was assessed by optical coherence tomography and histopathology.ResultsThe rate of neointimal hyperplasia as assessed by optical coherence tomography and histomorphometry was 32.2% and 35.1%, 28.1% and 33.4%, 17.3% and 20.9%, 28.6% and 30.2%, and 37.9% and 42.3% in the 0.25:1, 0.5:1, 1:1, and 1:0 excipient:sirolimus ratio groups and the control balloon group, respectively (P=0.03 for excipient:sirolimus 1:1 versus control balloon). The neointimal interstrut thickness (mm) was 0.23, 0.30, 0.16, 0.24, and 0.30 in the 0.25:1, 0.5:1, 1:1, and 1:0 excipient:sirolimus ratio groups and the control balloon group, respectively (P < 0.01 for excipient:sirolimus 1:1 versus control balloon). The inflammation, injury, and fibrin deposition scores were low, and there were no significant differences among the groups.ConclusionsThere was a stepwise increase in the inhibitory efficacy of neointimal proliferation as the excipient concentration increased. The lowest efficacy was observed with the 0.25:1 excipient:sirolimus formulation, and the greatest inhibition was observed with the 1:1 excipient:sirolimus formulation. The 1:1 excipient:sirolimus formulation significantly reduced neointimal proliferation when compared to the control group, with low inflammation and injury scores

Emerging technologies: Polymer-free phospholipid encapsulated sirolimus nanocarriers for the controlled release of drug from a stent-plus-balloon or a stand-alone balloon catheter

Drug-eluting stents have proven to be effective in reducing the risk of late restenosis. In order to achieve a controlled and prolonged release of the antiproliferative agent, current drug-eluting stents utilise various biodegradable as well as non-erodible polymeric blends to coat the stent surface and to serve as drug carriers. The utilisation of polymeric compounds in current drug-eluting stents may eventually limit their performance as well as their clinical applicability due to the potential induction of undesirable local reactions. The development of alternative, polymer-free drug carriers has the potential to overcome some of the limitations of current drug-eluting stent formulations. Moreover, improvements in drug carriers may also result in an expansion of the technological possibilities for other intravascular drug delivery systems, such as metal-free or even implant-free solutions. This article describes the structure and the preclinical validation profile of a novel phospholipid encapsulated sirolimus nanocarrier, used as a coating in two formulations: a coronary stent-plus-balloon system and a stand-alone balloon catheter. The nanoparticles provided a stable, even and homogenous coating to the devices in both formulations. Dose-finding studies allowed the most appropriate identification of the best nanoparticle structure associated with an extremely efficient transfer of drug to all layers of the vessel wall, achieving high tissue concentrations that persisted days after the application, with low systemic drug leaks