PB1165 - APAC, a heparin proteoglycan mimic, is a potent von Willebrand Factor-mediated antithrombotic over collagen in a microfluidic blood perfusion system under high shear rate

Background: APAC, a heparin proteoglycan mimic, is a locally acting dual antiplatelet and anticoagulant with selective inhibition against collagen and thrombin. In earlier studies APAC targets vascular injury, binds to von Willebrand factor (VWF) and inhibits collagen/tissue factor mediated platelet (by 50%) and fibrin recruitment (>80%) under arterial blood flow conditions. APAC is also anti-inflammatory, inhibits atherothrombosis and thromboinflammation in several animal models. APAC has entered clinical safety studies in patients with end stage renal disease needing a vascular access (local admin) and healthy volunteers (IV).

Aims: To study the antithrombotic action of APAC on upon collagen under an arterial shear rate conditions of the microfluidic system in vitro.

Methods: According to the microfluidic blood perfusion system (T-TAS), we spiked 1-3 µg/ml of APAC or unfractionated heparin (UFH) in healthy volunteer blood (n=6) anticoagulated with thrombin and FXa inhibitor benzylsulfonyl-D-Arg-Pro-4-amidinobenzylamide. The antiplatelet effect was detected under a shear rate of 1500 1/s over collagen coating. We simultaneously studied the antiplatelet effects of APAC or UFH in platelet aggregation induced by collagen(0.5µg/ml) (CIPA) or ADP(2µM) in citrated (3.2%)-platelet-rich plasma (n=6).

Results: APAC significantly delayed and reduced platelet-rich thrombus formation on the collagen surface. APAC at 1 µg/ml reduced the area under the flow pressure curve (AUC) by 1.9-fold compared with baseline controls. At 3 µg/ml, APAC, abolished thrombus formation completely. In contrast, UFH (1-3 µg/ml) reduced the baseline AUC only modestly by 1.3 to 1.5-fold. APAC inhibited CIPA unlike ADP by 62±31% (mean±SD) and 80±20% at 1 and 3 µg/ml, respectively, vs. vehicle. UFH did not inhibit CIPA.

Conclusion(s): In human blood in vitro, APAC concentration-dependently inhibited VWF-dependent thrombus growth under arterial shear rate conditions upon blocked thrombin and FXa activities. The antiplatelet action of APAC was CIPA specific since ADP was not inhibited. T-TAS method would complement the clinical studies undertaken with APAC.