Imatinib Mesylate-Incorporated Nanoparticle-Eluting Stent Attenuates In-Stent Neointimal Formation in Porcine Coronary Arteries

Aim: The use of currently marketed drug-eluting stents (DES) presents safety concerns, including an increased risk for late thrombosis in the range of 0.6% per year in patients, including acute coronary syndrome, which is thought to result from delayed endothelial healing effects. A new DES system targeting vascular smooth muscle cells without adverse effects on endothelial cells is therefore needed. Platelet-derived growth factor (PDGF) plays a central role in the pathogenesis of restenosis; therefore, we hypothesized that imatinib mesylate (PDGF receptor tyrosine kinase inhibitor) encapsulated bioabsorbable polymeric nanoparticle (NP)-eluting stent attenuates in-stent neointima formation. Methods: Effects of imatinib-incorporated NP-eluting stent on neointima formation and endothelial healing were examined in a pig coronary artery stent model. Effects of imatinib-NP were also examined in cultured cells. Results: In a cultured cell study, imatinib-NP attenuated the proliferation of vascular smooth muscle cells associated with inhibition of the target molecule (phosphorylation of PDGF receptor-beta), but showed no effect on endothelial proliferation. In a pig coronary artery stent model, imatinib-NP-eluting stent markedly attenuated in-stent neointima formation and stenosis by approximately 50% as assessed by angiographic, histopathological, and intravascular ultrasound imaging analyses. Imatinib-NP-eluting stent also attenuated MAP kinase activity, but did not affect inflammation and re-endothelialization. Conclusion: These data suggest that suppression of neointima formation by a imatinib-NP-eluting stent holds promise as a molecular-targeting NP delivery system for preventing in-stent restenosis.