PF797 APAC, A DUAL ANTIPLATELET AND ANTICOAGULANT ‐ TOWARDS A LOCAL, VASCULAR TARGETING ANTITHROMBOTIC
Authors: Jouppila A. , Barreiro K. , Tulamo R. , Parry M. , Albäck A. , Lassila R. 
Published: June 2019

Background:

APAC, is developed as a mimic of heparin proteoglycans, and has unique antiplatelet and anticoagulant action (collagen and thrombin) in several in vitro and in vivo models (Lassila & Jouppila, Semin Thromb Hemost, 2014). APAC as the only anticoagulant in blood inhibits both platelet and fibrin accumulation on collagen and tissue factor under a high shear rate (1000 1/s), and retains primary adhesion (Chen et al. Thromb Res, 2018). Moreover, APAC protects kidneys from ischemic reperfusion injury (Tuuminen et al. Clin Exp Nephrol 2017). APAC is eliminated via kidneys and liver as unfractionated heparin.

Aims:

We present APAC and its antithrombotic data on platelet aggregation and global coagulation in

vitro, vascular targeting and antithrombotic role in vivo, including toxicology margins.

Methods:

1. Blood was collected from healthy volunteers. APAC was studied in human platelet aggregation in response to collagen and ristocetin in whole blood (Multiplate), platelet‐rich plasma (PRP) and in rotational thromboelastometry (ROTEM) compared with citrated (3.2%) blood and spiking. APAC's antiplatelet efficacy with acetylsalicylic acid (ASA) was estimated in collagen‐, arachidonic acid (AA)‐ or ADP‐induced platelet aggregation in PRP or whole blood, 2. Porcine arterio‐venous fistula of femoral arterial and venous anastomosis sites and balloon denudation of iliac and carotid arteries were exposed to biotin‐labelled APAC to study APAC binding and localization. 3. Single and repeated dose toxicology of rodents and monkeys was assessed.

Results:

APAC dose‐dependently attenuates platelet aggregation to collagen and ristocetin, unlike heparin, in citrated whole blood at 150 μg/mL by 58 ± 15% (n = 6) (mean ± SD) and by 25 ± 2%, respectively. In PRP, inhibition of collagen‐induced aggregation was 55 ± 31% at 1 μg/mL APAC and 85 ± 11% at 30 μg/mL APAC (n = 9). APAC alone, also dose‐dependently attenuated aggregation and ROTEM variables in whole blood. In ROTEM, APAC alone (at 3–16 μg/mL) reduces intrinsic pathway of coagulation (INTEM), and acts as a broad platelet‐dependent procoagulant. ASA dose‐dependently inhibited collagen‐induced platelet aggregation, clearly potentiated by APAC requiring up to 4‐fold higher collagen concentration to induce aggregation in PRP. In turn, ADP‐ or AA‐induced aggregation was unaffected. APAC co‐localized with Von Willebrand Factor and laminin in porcine arterial injuries, but not with intact endothelium, which stained positive for PECAM or podocalyxin. Upon targeting vessels, APAC locally decreased platelet accumulation and overt thrombosis in a rat model of anastomosis, but retained at anastomosis sites despite high shear blood flow. Single and multiple (7–14 day) doses (3–20 mg/kg in monkeys and rodents) indicate wide safety without APAC accumulation in the toxicology program.

Summary/Conclusion:

APAC, inhibits collagen‐ and ristocetin‐, but not ADP‐induced, platelet aggregation in citrated blood and PRP, and synergizes with ASA. In citrated whole blood, and if used as a sole anticoagulant, APAC globally attenuates platelet procoagulant activity and fibrin elasticity. With APAC's unique profile, local integration and inhibition of platelet‐mediated thrombosis may benefit vascular interventions.