Reduced-dose prasugrel monotherapy without aspirin after PCI with the SYNERGY stent in East Asian patients presenting with chronic coronary syndromes or non-ST-elevation acute coronary syndromes: rationale and design of the ASET Japan pilot study

The Acetyl Salicylic Elimination Trial (ASET) Japan pilot study is a multicentre, single-arm, open-label, proof-of-concept study with a stopping rule based on the occurrence of definite stent thrombosis. This study aims to demonstrate the feasibility and safety of low-dose prasugrel monotherapy following percutaneous coronary intervention (PCI) in Japanese patients presenting with chronic coronary syndromes (CCS) or non-ST-elevation acute coronary syndromes (NSTE-ACS). Four hundred patients with a SYNTAX score <23 requiring PCI due to CCS or NSTE-ACS will be screened and considered eligible for the study. The enrolment is planned in two phases: 1) 200 patients presenting with CCS, followed by 2) 200 patients presenting with NSTE-ACS. After optimal PCI with implantation of a SYNERGY (Boston Scientific) stent, patients will be enrolled and loaded with prasugrel 20 mg, followed by a maintenance dose of prasugrel 3.75 mg once daily without aspirin continued for 3 months in Phase 1 (CCS patients), and for 12 months in Phase 2 (NSTE-ACS patients). After these follow-up periods, prasugrel will be replaced by standard antiplatelet therapy according to local practice. The primary endpoint is a composite of cardiac death, target vessel myocardial infarction, or definite stent thrombosis after the index procedure. The primary bleeding endpoint is any Bleeding Academic Research Consortium type 3 or 5 bleeding occurring within 3 months of the index PCI for CCS patients, or 12 months for NSTE-ACS patients. The ASET Japan study is designed to demonstrate the feasibility and safety of reduced-dose prasugrel monotherapy after PCI in East Asian patients with acute and chronic coronary syndromes.