Platelet inhibition during ticagrelor monotherapy versus ticagrelor plus aspirin in patients with coronary artery disease (TEMPLATE study): study protocol for a randomised controlled trial.

BACKGROUND: Dual antiplatelet therapy (DAPT) with aspirin (ASP) and a P2Y12 blocker is currently standard care after percutaneous coronary intervention (PCI) with stent insertion, and aims to inhibit platelet function in order to prevent stent thrombosis. The P2Y12 blocker ticagrelor (TIC) has greater antiplatelet effect than the previously used members of this class, such as clopidogrel. In healthy volunteers, TIC is sufficient to cause strong platelet inhibition, with little additional effect from ASP. Omission of ASP may improve the safety of antiplatelet regimes by reducing bleeding. However, the effect of single antiplatelet treatment with TIC, compared to DAPT with TIC + ASP, has not been studied in detail in patients with coronary artery disease.

METHODS: To compare TIC with TIC + ASP, we have initiated a single centre, open-label randomised controlled trial (TEMPLATE study) in adults receiving DAPT following PCI with a sample size of 110 patients. Patients are invited to join the study when, as part of standard care, they are due to switch from DAPT (ASP + any P2Y12 blocker) to single antiplatelet treatment with ASP alone after 6-12 months. Patients are randomised to receive either TIC or TIC + ASP for 4 weeks. All patients then revert to standard care with ASP alone. Blood samples and clinical data are collected at three study visits: at baseline during treatment with ASP + any P2Y12 blocker (visit 1); approximately 4 weeks after visit 1 during treatment with either TIC or TIC + ASP (visit 2); and approximately 8 weeks after visit 1 when treatment has reverted to ASP alone (visit 3). The primary outcome is the extent of platelet inhibition, measured by light transmission aggregation, flow cytometry, flow chamber and plasma biomarker tests. The primary analysis will compare the extent of platelet inhibition between the TIC and TIC + ASP groups at visit 2, adjusted for baseline platelet reactivity. Secondary analyses will compare the extent of platelet inhibition at visit 2 with that at visit 3.

DISCUSSION: This is the first study to compare in detail the extent of platelet inhibition in patients who are receiving TIC compared with TIC + ASP. The study findings will complement larger-scale trials of the clinical efficacy and safety of TIC compared to TIC + ASP.

TRIAL REGISTRATION: ISRCTN registry, identifier ISRCTN84335288 . Registered on 23 June 2014.