One-year clinical outcome of aspirin-free prasugrel monotherapy following stent implantation in patients with chronic coronary syndrome: insight from ASET-JAPAN study
Authors: Miyashita K , Muramatsu T , Ishibashi Y , Nakazawa G , Okamura T , Kogame N , Asano T , Nakatani S , Morino Y , Katagiri Y , Tanabe K , Ozaki Y , Kozuma K , Serruys P , Onuma Y 
Published: October 2024

Abstract

Background
Single antiplatelet therapy with a potent P2Y12 inhibitor without aspirin after coronary stent implantation may provide an adequate balance between ischemic and bleeding risks in selected patients. The 3-month follow-up of the Acetyl-Salicylic Elimination Trial (ASET)-Japan pilot study demonstrated the feasibility and safety of Prasugrel monotherapy without aspirin after successful percutaneous coronary intervention (PCI) in selected patients with chronic coronary syndrome (CCS).

Purpose
The current study aimed to evaluate the 1-year clinical outcome in the ASET-Japan.

Methods
The ASET-Japan pilot study was designed to demonstrate the feasibility and safety of the approved dose of prasugrel monotherapy in Japan without aspirin after optimal PCI with a platinum-chromium everolimus-eluting stent in CCS population. After successful procedure, all patients were treated with a locally approved maintenance dose of 3.75 mg/day of Prasugrel monotherapy up to 3-month. After 3-month, the choice of antiplatelet therapy was left to the discretion of the investigators. Patients were followed up to 1 year. The target lesion-related endpoint was a composite of cardiac death, spontaneous target-vessel myocardial infarction (MI) &gt;48 h after the index PCI or clinical-driven target lesion revascularisation. Patient-Oriented Composite Endpoint (POCE) was defined as a composite of all cause mortality, any stroke, any MI and any revascularisation. Spontaneous MI was defined according to Forth universal definition. The event rate was estimated by the Kaplan-Meier method. The event was adjudicated by an independent clinical event committee.

Results
A total of 208 patients were enrolled in the study. The average anatomical SYNTAX score was 7.96 (±4.6). After procedure, prasugrel monotherapy was immediately initiated. After 3-month, Prasugrel monotherapy was continued in 88.6% up to 1-year. Aspirin monotherapy was prescribed to 10 patients (5.0%), while 6 patients (3.0%) were on DAPT at 1-year. All-cause mortality rate was 1.49%, with no occurrence of cardiovascular death. Revascularisation occurred in 4.0% (n=8) with no occurrence of TLR, while one patient (0.5%) underwent a clinical driven target vessel revascularisation. In summary, 7 out of 8 revascularisations were non-target vessel revascularisation (6 clinically-driven non-TVR). Spontaneous non TV-MI occured in 0.5% (n=1) of patients. There was no definite/probable stent thrombosis up to 1 year. The target lesion related endpoint rate at 1-year was 0%, whereas 1-year POCE rate was 7.0% (n=14).

Conclusion
Discontinuation of Aspirin and Prasugrel monotherapy at a low maintenance dose of 3.75 mg/day following an angiographically successful stent deployment was feasible and safe in selected patients with CCS and low SYNTAX score. This safety profile is confirmed at 1 year while the investigators, in their large majority and at their own discretion, had maintained the prasugrel treatment.