Key words: G protein-coupled receptors, proteinase activated receptors, pharmacology, cell biology Research Group: New Medicines Fundamentals, New Medicines Target Validation

Thrombin-mediated platelet activation and aggregation occurs through a class of G-Protein coupled receptors (GPCRs) called proteinase-activated receptors (PARs). PAR1 and PAR4 are responsible for the thrombin-mediated activity in human platelets that precedes thrombus formation. As such, these have become desirable anti-platelet targets for cardiovascular therapies. Current drugs that target PARs include small molecule competitive PAR1 antagonist Vorapaxar [1]. However, the outcome of clinical trials for Vorapaxar revealed an increased risk of intracranial haemorrhage in patients which has limited its clinical use [2]. This has led to the development of new ways to target this receptor family. A class of compounds known as pepducins have been developed to allosterically modulate PAR activity [3]. PZ-128 is the first example of a pepducin to enter clinical trials as a potential anti-platelet therapy, having passed Phase I trials as a PAR1 inhibitor [4]. We have recently developed a new generation of pepducin that targets PAR4 as an alternative anti-platelet strategy.

Project aim
The aim of this project is to functionally screen the library of PAR4 pepducins in mammalian cell line models and conduct platelet function assays to determine their anti-platelet potential.

Cell signalling assays, Western blotting, confocal microscopy

1. Chackalamannil, S., et al., Discovery of a novel, orally active himbacine-based thrombin receptor antagonist (SCH 530348) with potent antiplatelet activity. J Med Chem, 2008. 51(11): p. 3061-4.
2. Morrow, D.A., et al., Vorapaxar in the secondary prevention of atherothrombotic events. N Engl J Med, 2012. 366(15): p. 1404-13.
3. Covic, L., et al., Pepducin-based intervention of thrombin-receptor signaling and systemic platelet activation. Nat Med, 2002. 8(10): p. 1161-5.
4. Gurbel, P.A., et al., Cell-Penetrating Pepducin Therapy Targeting PAR1 in Subjects With Coronary Artery Disease. Arterioscler Thromb Vasc Biol, 2016. 36(1): p. 189-97.