Pharmacodynamic and Short-term Effects of Half-dose Ticagrelor With or Without Aspirin vs DAPT From Day of PCI in CCS

Six months of aspirin plus clopidogrel remains the recommended antiplatelet regimen after percutaneous coronary intervention (PCI) for chronic coronary syndrome (CCS), with the more potent P2Y₁₂ inhibitors reserved for the acute coronary syndromes (ACS) that produced their pivotal evidence. Yet the contemporary landscape of post-PCI antithrombotic therapy has shifted considerably since PLATO and TRITON-TIMI 38, and the conventional algorithm sits increasingly uneasily with two well-established realities. The first is the now consistent demonstration that aspirin contributes more to bleeding than to ischemic protection in patients adequately treated with a P2Y₁₂ inhibitor. TWILIGHT, TICO, T-PASS, ULTIMATE-DAPT and GLOBAL LEADERS have, in sequence, established that withdrawing aspirin after a defined period of P2Y₁₂-based DAPT reduces clinically relevant bleeding without an excess of ischemic events. Each of these trials, however, retained ticagrelor at the standard 90 mg twice-daily dose, required a run-in of conventional DAPT before aspirin was stopped, and enrolled populations dominated by ACS. The second is the persistent and now mechanistically grounded observation that East-Asian patients tolerate less antithrombotic intensity than the Caucasian populations on whom dose recommendations were calibrated. Ticagrelor exposure is higher in East-Asian patients, baseline platelet reactivity is lower, and the bleeding-to-ischemia ratio is shifted relative to PLATO-era expectations. Pharmacokinetic and pharmacodynamic work in Chinese and Japanese cohorts has shown that ticagrelor 45 mg twice daily - half the standard maintenance dose - yields platelet inhibition statistically indistinguishable from the 90 mg regimen. No randomised trial has yet tested an aspirin-free, half-dose ticagrelor monotherapy strategy initiated at the index PCI in CCS patients. The closest registered protocol of which we are aware (NCT07080684) uses ticagrelor 60 mg twice daily following a one-month DAPT lead-in, with a two-arm design. We therefore conducted a three-arm randomised pilot trial in East-Asian CCS patients to compare standard DAPT, DAPT with half-dose ticagrelor, and aspirin-free half-dose ticagrelor monotherapy from the day of PCI, using the change in P2Y₁₂ reaction units (PRU) as the primary pharmacodynamic readout and twelve-month clinical events as exploratory endpoints.

Inclusion Criteria: * adults with CCS, defined per the 2019 ESC criteria, scheduled for elective PCI on the day after admission * able to provide consent Exclusion Criteria: * ACS at presentation * Prior intolerance to any study drug * Active bleeding or BARC ≥ 3 bleeding within three months, * NYHA IV heart failure * Platelet count below 100 × 10⁹/L * eGFR below 30 mL/min/1.73 m² * Severe hepatic dysfunction * Planned non-cardiac surgery within twelve months * Patient who inabley to provide consent. * Patients in whom PCI was not performed at the index procedure (per protocol)