Platelet-derived growth factor receptor antagonist STI571 (imatinib mesylate) inhibits human vascular smooth muscle proliferation and migration in vitro but not in vivo.

BACKGROUND

Cell-specific inhibition of vascular smooth muscle cells, the primary constituent of neointima following arterial injury, without deleterious effects on vascular endothelial cell function may be a critical requirement for drug-eluting stents that are not prone to excess late thrombosis. We hypothesized that imatinib mesylate (Gleevec, Glivec, formerly known as STI571), a relatively selective inhibitor of protein tyrosine kinases including platelet-derived growth factor receptor (PDGFR), would inhibit hCASMC proliferation and migration in vitro with little effect on endothelial cell proliferation and prevent restenosis in a swine balloon injury model.

METHODS

Proliferation and migration of stimulated human vascular smooth muscle and endothelial cells were quantified in cell culture in the presence of imatinib (0.001 to 10 M). Imatinib-loaded drug-eluting stents were implanted in swine coronary arteries after predilatation with an oversized balloon, and neointimal proliferation was measured by quantitative angiography and histopathology.

RESULTS

Increasing doses of imatinib-inhibited autophosphorylation of the PDGFR and its downstream effects of proliferation and migration of human CASMC in a dose-responsive manner, yet had no effect on stimulated human aortic endothelial cells. However, imatinib-eluting stents had no effect on neointimal proliferation and restenosis in a standard porcine in-stent restenosis model compared to bare-metal or unloaded polymer-coated stents.

CONCLUSION

We conclude that imatinib is a potent inhibitor of proliferation and migration of human vascular smooth muscle cells in vitro, but has no effect on human vascular endothelial cell proliferation. However, the lack of an in vivo effect on neointimal proliferation in a standard porcine coronary overstretch model does not support the use of imatinib mesylate for localized drug delivery in the prevention of in-stent restenosis.