Platelet Inhibition And Patient Outcomes Trial Research Articles

Ticagrelor

The complex mechanism of platelet activation creates an optimal target for pharmacological treatment in patients with acute coronary syndromes. Current antiplatelet medications that are used in addition to aspirin include the thienopyridines, clopidogrel and prasugrel, but there are several limitations to the use of these medications. Clopidogrel and prasugrel irreversibly bind to the P2Y12 receptor, creating a prolonged antiplatelet effect which can be undesirable when surgery is needed. Clopidogrel requires hepatic activation and produces variable platelet inhibition based on genetic polymorphisms. Prasugrel has more consistent platelet inhibition than clopidogrel but carries with it an increased risk of serious bleeds. Ticagrelor is a drug in a new chemical class that reversibly binds the P2Y12 receptor and noncompetitively blocks adenosine diphosphate-induced platelet activation. It was specifically designed to address the limitations of the available antiplatelet agents while maintaining comparable or better antiplatelet effects. It does not require metabolic activation and demonstrates greater platelet inhibition, a faster offset of action and comparable bleeding risk compared to clopidogrel. The pivotal PLATO (The Study of Platelet Inhibition and Patient Outcomes) trial in patients with an acute coronary syndrome demonstrated improved cardiovascular outcomes, including a reduction in myocardial infarctions and vascular events using ticagrelor as compared to clopidogrel with comparable rates of major bleeds. A puzzling finding from that trial was the lack of benefit with ticagrelor in patients enrolled from the United States, which has led to ticagrelor not being approved at this time in this country. The main adverse events with ticagrelor are bleeding and dyspnea, the latter of which is of unclear etiology and of unknown long-term clinical concern. In summary, ticagrelor is an exciting new oral antiplatelet drug that seems to be more efficacious than clopidogrel, with comparable safety. Whether issues of geographic disparities in response and the unusual side effect of dyspnea ultimately prove problematic has yet to be determined. Nonetheless, ticagrelor is a drug that has the potential to change the standard of care of patients with acute coronary syndromes.

Ticagrelor Versus Clopidogrel in Patients With Acute Coronary Syndromes Undergoing Coronary Artery Bypass Surgery: Results From the PLATO (Platelet Inhibition and Patient Outcomes) Trial

The purpose of this study is to evaluate the efficacy and safety of ticagrelor and clopidogrel in patients with acute coronary syndrome undergoing coronary artery bypass graft surgery (CABG), as a post-randomization strategy. Ticagrelor is a novel, reversibly binding, oral, direct-acting P2Y(12)-receptor antagonist. In the PLATO (Platelet Inhibition and Patient Outcomes) trial, which randomized 18,624 patients with acute coronary syndromes, ticagrelor compared with clopidogrel significantly reduced the risk of the primary composite end point of cardiovascular (CV) death, myocardial infarction, or stroke (hazard ratio [HR]: 0.84; 95% confidence interval [CI]: 0.77 to 0.92; p < 0.001). This report investigated the outcomes of patients treated with CABG during the trial. In total, 1,899 patients underwent CABG post-randomization. The protocol recommended ticagrelor/placebo to be withheld for 24 to 72 h and clopidogrel/placebo for 5 days preoperatively. In all, 1,261 patients underwent CABG and were receiving study drug treatment <7 days before surgery. The statistical analysis was based on events occurring from the CABG procedure until the end of the study, excluding 3 patients with CABG after study end. In the 1,261 patient cohort, the relative reduction of primary composite end point at 12 months (10.6% [66 of 629] with ticagrelor versus 13.1% [79 of 629] with clopidogrel; HR: 0.84; 95% CI: 0.60 to 1.16; p = 0.29) was consistent with the results of the whole trial. Total mortality was reduced from 9.7% (58 of 629) to 4.7% (29 of 629; HR: 0.49; 95% CI: 0.32 to 0.77; p < 0.01), CV death from 7.9% (47 of 629) to 4.1% (25 of 629; HR: 0.52; 95% CI: 0.32 to 0.85; p < 0.01), and non-CV death numerically from 2.0% to 0.7% (p = 0.07). There was no significant difference in CABG-related major bleeding between the randomized treatments. In the subgroup of patients undergoing CABG within 7 days after the last study drug intake, ticagrelor compared with clopidogrel was associated with a substantial reduction in total and CV mortality without excess risk of CABG-related bleeding.

Ticagrelor Versus Clopidogrel in Patients With ST-Elevation Acute Coronary Syndromes Intended for Reperfusion With Primary Percutaneous Coronary Intervention

Background— Aspirin and clopidogrel are recommended for patients with acute coronary syndromes (ACS) or undergoing coronary stenting. Ticagrelor, a reversible oral P2Y12-receptor antagonist, provides faster, greater, and more consistent platelet inhibition than clopidogrel and may be useful for patients with acute ST-segment elevation (STE) ACS and planned primary percutaneous coronary intervention. Methods and Result— Platelet Inhibition and Patient Outcomes (PLATO), a randomized, double-blind trial, compared ticagrelor with clopidogrel for the prevention of vascular events in 18 624 ACS patients. This report concerns the 7544 ACS patients with STE or left bundle-branch block allocated to either ticagrelor 180-mg loading dose followed by 90 mg twice daily or clopidogrel 300-mg loading dose (with provision for 300 mg clopidogrel at percutaneous coronary intervention) followed by 75 mg daily for 6 to 12 months. The reduction of the primary end point (myocardial infarction, stroke, or cardiovascular death) with ticagrelor versus clopidogrel (10.8% versus 9.4%; hazard ratio [HR], 0.87; 95% confidence interval, 0.75 to 1.01; P =0.07) was consistent with the overall PLATO results. There was no interaction between presentation with STE/left bundle-branch block and randomized treatment (interaction P =0.29). Ticagrelor reduced several secondary end points, including myocardial infarction alone (HR, 0.80; P =0.03), total mortality (HR, 0.82; P =0.05), and definite stent thrombosis (HR, 0.66; P =0.03). The risk of stroke, low in both groups, was higher with ticagrelor (1.7% versus 1.0%; HR,1.63; 95% confidence interval, 1.07 to 2.48; P =0.02). Ticagrelor did not affect major bleeding (HR, 0.98; P =0.76). Conclusion— In patients with STE-ACS and planned primary percutaneous coronary intervention, the effects of ticagrelor were consistent with those observed in the overall PLATO trial. Clinical Trial Registration— URL: http://www.ClinicalTrials.gov . Unique identifier: NCT00391872.

Randomized Double-Blind Assessment of the ONSET and OFFSET of the Antiplatelet Effects of Ticagrelor Versus Clopidogrel in Patients With Stable Coronary Artery Disease

Background— Ticagrelor is the first reversibly binding oral P2Y 12 receptor antagonist. This is the first study to compare the onset and offset of platelet inhibition (IPA) with ticagrelor using the PLATO (PLATelet inhibition and patient Outcomes) trial loading dose (180 mg) with a high loading dose (600 mg) of clopidogrel. Methods and Results— In a multicenter, randomized, double-blind study, 123 patients with stable coronary artery disease who were taking aspirin therapy (75 to 100 mg/d) received ticagrelor (180-mg load, 90-mg BID maintenance dose [n=57]), clopidogrel (600-mg load, 75-mg/d maintenance dose [n=54]), or placebo (n=12) for 6 weeks. Greater IPA (20 μmol/L ADP, final extent) occurred with ticagrelor than with clopidogrel at 0.5, 1, 2, 4, 8, and 24 hours after loading and at 6 weeks ( P &lt;0.0001 for all); by 2 hours after loading, a greater proportion of patients achieved &gt;50% IPA (98% versus 31%, P &lt;0.0001) and &gt;70% IPA (90% versus 16%, P &lt;0.0001) in the ticagrelor group than in the clopidogrel group, respectively. A faster offset occurred with ticagrelor than with clopidogrel (4-to-72–hour slope [% IPA/h] −1.04 versus −0.48, P &lt;0.0001). At 24 hours after the last dose, mean IPA was 58% for ticagrelor versus 52% for clopidogrel ( P =NS). IPA for ticagrelor on day 3 after the last dose was comparable to clopidogrel at day 5; IPA on day 5 for ticagrelor was similar to clopidogrel on day 7 and did not differ from placebo ( P =NS). Conclusions— Ticagrelor achieved more rapid and greater platelet inhibition than high-loading-dose clopidogrel; this was sustained during the maintenance phase and was faster in offset after drug discontinuation. Clinical Trial Registration Information— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00528411.

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

Results of the PLATelet Inhibition and Patient Outcomes (PLATO) Trial

This article discusses a subset analysis of the larger PLATO trial where ticagrelor was superior to clopidogrel in terms of preventing cardiovascular death, myocardial infarction, or stroke in patients who presented with STEMI and for whom PCI was planned, without causing a significant increase in major bleeding.