Recombinant soluble apyrase APT102 inhibits thrombosis and intimal hyperplasia in vein grafts without adversely affecting hemostasis or re-endothelialization

Background: Occlusion of vein grafts (VGs) after bypass surgery, owing to thrombosis and intimal hyperplasia (IH), is a major clinical problem. Apyrases are enzymes that scavenge extracellular ATP and ADP, and promote adenosine formation at sites of vascular injury, and hence have the potential to inhibit VG pathology. Objectives: To examine the effects of recombinant soluble human apyrase, APT102, on platelets, smooth muscle cells (SMCs) and endothelial cells (ECs) in vitro, and on thrombosis and IH in murine VGs. Methods: SMC and EC proliferation and migration were studied in vitro. Inferior vena cava segments from donor mice were grafted into carotid arteries of recipient mice. Results: APT102 potently inhibited ADP-induced platelet aggregation and VG thrombosis, but it did not impair surgical hemostasis. APT102 did not directly inhibit SMC or EC proliferation, but significantly attenuated the effects of ATP on SMC and EC proliferation. APT102 significantly inhibited SMC migration, but did not inhibit EC migration, which may be mediated, at least in part, by inhibition of SMC, but not EC, migration by adenosine. At 4 weeks after surgery, there was significantly less IH in VGs of APT102-treated mice than in control VGs. APT102 significantly inhibited cell proliferation in VGs, but did not inhibit re-endothelialization. Conclusions: Systemic administration of a recombinant human apyrase inhibits thrombosis and IH in VGs without increasing bleeding or compromising re-endothelialization. These results suggest that APT102 has the potential to become a novel, single-drug treatment strategy to prevent multiple pathologic processes that drive early adverse remodeling and occlusion of VGs.