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Updated: Jun 10, 2026
Characterizing Modulators of Protease-Activated Receptors with a Calcium Mobilization Assay Using a Plate Reader
Published on: May 24, 2024
Mechanism of action and clinical development of platelet thrombin receptor antagonists
Masafumi Ueno1, José Luis Ferreiro, Dominick J Angiolillo
1Division of Cardiology, Department of Medicine, University of Florida College of Medicine-Jacksonville, Shands Jacksonville, 655 West 8th Street, Jacksonville, FL 32209, USA.
Insights
New drugs targeting protease-activated receptor-1 (PAR-1) show promise in preventing atherothrombotic events. These novel antiplatelet agents aim to reduce ischemic events without increasing bleeding risk.
Area of Science:
- Cardiovascular Medicine
- Pharmacology
Background:
- Atherothrombotic disease is a leading global cause of mortality.
- Current dual antiplatelet therapy improves outcomes but carries bleeding risks and high rates of recurrent ischemic events.
Purpose of the Study:
- To review the pharmacologic properties and clinical development of novel platelet thrombin receptor antagonists.
- To highlight protease-activated receptor-1 (PAR-1) antagonists as a promising strategy for atherothrombotic disease.
Main Methods:
- Review of preclinical and clinical trial data for PAR-1 antagonists SCH 530348 and E5555.
- Focus on pharmacologic properties, safety, tolerability, and efficacy in reducing ischemic events.
Main Results:
- Preclinical trials demonstrated antiplatelet effects of SCH 530348 and E5555 without increased bleeding time.
- Phase II trials indicated SCH 530348 is well-tolerated and does not increase bleeding risk when added to standard therapy.
- Ongoing Phase III trials are assessing the efficacy of SCH 530348.
Conclusions:
- Selective PAR-1 inhibition represents a novel therapeutic strategy for atherothrombotic disease.
- PAR-1 antagonists offer potential for reducing ischemic events while mitigating bleeding risk.
- Further clinical development is ongoing for these promising antiplatelet agents.
Abstract:
Atherothrombotic disease is the leading cause of death worldwide. Currently, dual antiplatelet therapy with aspirin and ADP receptor antagonists has shown improved short- and long-term clinical outcomes but is associated with increased bleeding risk, and the rates of recurrent ischemic events still remain high. Selective inhibition of the principal protease-activated receptor (PAR)-1 for thrombin, the most potent platelet activator, represents a promising novel strategy to reduce ischemic events without increasing the risk of bleeding. Two PAR-1 antagonists are currently being tested in clinical trials: SCH 530348 and E5555. Both have demonstrated an antiplatelet effect without increasing bleeding time in preclinical trials. Results of Phase II trials showed that SCH 530348, in addition to standard antiplatelet therapy, was well tolerated and not associated with increased bleeding risk. The safety and tolerability of E5555 is being evaluated in patients with coronary artery disease and non-ST-segment elevation acute coronary syndrome in four Phase II clinical trials. Two large-scale Phase III trials assessing the efficacy of SCH 530348 in addition to the standard of care are currently ongoing. This article provides an overview of the current status of knowledge on platelet thrombin receptor antagonists, focusing on pharmacologic properties and clinical development.
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