Pharmacodynamic and clinical efficacy of reduced ticagrelor maintenance doses in patients with coronary artery disease

Diurnal Variability of Platelet Aggregation in Patients with Myocardial Infarction Treated with Prasugrel and Ticagrelor

Background: Contemporary antiplatelet treatment in acute myocardial infarction (AMI) is based on one of two P2Y12 receptor inhibitors, prasugrel or ticagrelor. The aim of this study was to compare diurnal variability of platelet reactivity between patients receiving prasugrel and ticagrelor during the initial phase of maintenance treatment after AMI. Methods: It was a prospective, two-center, pharmacodynamic, observational study. Blood for platelet testing was sampled at four time points on day four after AMI (8:00, 12:00, 16:00, 20:00). Diurnal variability of platelet reactivity was expressed as a coefficient of variation (CV) of the above-mentioned measurements. Results: 73 invasively-treated patients were enrolled (ticagrelor: n = 47, prasugrel: n = 26). CV was greater in patients treated with ticagrelor compared with prasugrel according to a VASP assay (47.8 [31.6–64.6]% vs. 21.3 [12.9–25.5]%, p < 0.001), while no statistical differences were detected when the CVs of platelet aggregation according to Multiplate were compared between ticagrelor- and prasugrel-treated patients. Ticagrelor-treated patients showed more pronounced platelet inhibition than prasugrel at 16:00 and 20:00 (VASP_16:00: 20.6 ± 15.0 vs. 24.9 ± 12.8 PRI, p = 0.049; VASP_20:00: 18.6 ± 17.7 vs. 26.0 ± 11.7 PRI, p = 0.002). Conclusions: Ticagrelor shows greater diurnal variability in platelet aggregation than prasugrel during the initial maintenance phase of AMI treatment, and this is due to the continuous increase of platelet inhibition after the morning maintenance dose. Both drugs provide an adequate antiplatelet effect early after AMI. Evaluation of the clinical significance of these findings warrants further investigation.

A new approach to ticagrelor-based de-escalation of antiplatelet therapy after acute coronary syndrome. A rationale for a randomized, double-blind, placebo-controlled, investigator-initiated, multicenter clinical study

The risk of ischemic events gradually decreases after acute coronary syndrome (ACS), reaching a stable level after 1 month, while the risk of bleeding remains steady during the whole period of dual antiplatelet treatment (DAPT). Several de-escalation strategies of antiplatelet treatment aiming to enhance safety of DAPT without depriving it of its efficacy have been evaluated so far. We hypothesized that reduction of the ticagrelor maintenance dose 1 month after ACS and its continuation until 12 months after ACS may improve adherence to antiplatelet treatment due to better tolerability compared with the standard dose of ticagrelor. Moreover, improved safety of treatment and preserved anti-ischemic benefit may also be expected with additional acetylsalicylic acid (ASA) withdrawal. To evaluate these hypotheses, we designed the Evaluating Safety and Efficacy of Two Ticagrelor-based De-escalation Antiplatelet Strategies in Acute Coronary Syndrome - a randomized clinical trial (ELECTRA-SIRIO 2), to assess the influence of ticagrelor dose reduction with or without continuation of ASA versus DAPT with standard dose ticagrelor in reducing clinically relevant bleeding and maintaining anti-ischemic efficacy in ACS patients. The study was designed as a phase III, randomized, multicenter, double-blind, investigator-initiated clinical study with a 12-month follow-up (ClinicalTrials.gov Identifier: NCT04718025; EudraCT number: 2020-005130-15).