“Ticagrelor versus Clopidogrel in Patients with Acute Coronary Syndromes”
by The Study of Platelet Inhibition and Patient Outcomes (PLATO) investigators
N Engl J Med. 2009 Sep 10;361(11):1045-57. [free full text]
In patients with acute coronary syndrome (ACS), with or without ST-segment elevation, clinical practice guidelines recommend dual antiplatelet therapy with aspirin plus one of either clopidogrel, prasugrel, or ticagrelor to reduce risk of thrombosis. The 2009 PLATO trial was designed to determine whether ticagrelor was superior to clopidogrel for the prevention of vascular events and death in patients presenting with ACS as well as whether this potential benefit came with an increased risk of major bleeding events.
Patients hospitalized for ACS with or without ST-elevations with symptom onset during the previous 24 hours.
If there were no ST-elevations, patients were required to have at least 2 of 3 of the following: ST change reflecting ischemia, elevated cardiac biomarkers (i.e. troponin), or one of several risk factors (age ≥ 60, prior MI/CABG, CAD w/ ≥ 50% stenosis in ≥ 2 vessels, prior ischemic stroke/TIA/carotid stenosis ≥ 50%, DM, PAD, CrCl < 60)
Intervention: ticagrelor 180mg loading dose followed by 90mg BID + aspirin
Comparison: clopidogrel 300mg loading dose followed by 75mg daily + aspirin
Primary: composite of death from vascular causes, MI, or CVA
- major bleeding (fatal bleeding, intracranial bleeding, intrapericardial bleeding w/ tamponade, hemorrhagic shock, decline of Hgb < 5.0, or requiring transfusion of 4 units pRBC)
- all-cause mortality, MI, or stroke
- composite of death from vascular mortality, MI, stroke, recurrent severe ischemia, recurrent ischemia, TIA, or other arterial thrombotic event
- stent thrombosis
18,624 patients from 862 centers in 43 countries were recruited and enrolled in the study. 9,333 were randomized to the ticagrelor group, and 9291 were randomized to the clopidogrel group. Patients were followed for up to 12 months.
The two treatment groups did not statistically differ in baseline characteristics, non-study medications following randomization, or procedures following randomization. Both groups started the study drug at a median of 11.3 hours after the onset of chest pain.
The primary end point (death from vascular causes, MI, or CVA) occurred less often in the ticagrelor group than in the clopidogrel group – 9.8% vs 11.7% (HR 0.77 – 0.92; p < 0.001; NNT = 52.6).
The groups did not significantly differ in terms of major bleeding – 11.6% vs. 11.2% (HR 1.04; 95% CI 0.95 – 1.13; p = 0.43).
Patients who received ticagrelor trended toward an increased rate of intracranial bleeding (26 [0.3%] vs. 14 [0.2%], p = 0.06), including a statistically significant increase in fatal intracranial bleeding (11 [0.1%] vs. 1 [0.01%], p = 0.02) as well as non-CABG bleeding (4.5% vs. 3.8%, p = 0.03). However, there were fewer episodes of other types of fatal bleeding in the ticagrelor group.
Regarding other secondary outcomes, ticagrelor performed better in:
- composite of all-cause, MI, or stroke – 10.2% vs. 12.3% (HR 0.84; 95% CI 0.77 – 0.92; p < 0.001; NNT 47.6)
- composite of death from vascular causes, MI, stroke, severe recurrent ischemia, recurrent ischemia, TIA, or other arterial thrombotic event – 14.6% vs. 16.7% (HR 0.88; 95% CI 0.81 – 0.95; p < 0.001; NNT 47.6)
- stent thrombosis – 1.3% vs. 1.9% (HR 0.67; 95% CI 0.50-0.91; p = 0.009, NNT = 167).
Dyspnea was more common in the ticagrelor group than in the clopidogrel group (13.8% vs 7.8%, p < 0.001). There was a higher incidence of ventricular pauses in the first week in the ticagrelor group relative to the clopidogrel group; however, the two groups did not differ in incidence of syncope or pacemaker implantation. Discontinuation of study drug due to adverse event was more common in the ticagrelor group (7.4% vs. 6.0%). Ticagrelor was also associated with elevations in uric acid and creatinine.
PLATO demonstrated that treatment of ACS with ticagrelor (vs. clopidogrel) significantly reduced the rate of death from vascular causes, MI, or stroke, without increasing the risk of major bleeding.
Although ticagrelor patients did demonstrate higher rates of intracranial and non-CABG bleeding, this bleeding did not qualify as “major bleeding.” They also complained more frequently of dyspnea (a known adverse effect of the drug). Discontinuation of ticagrelor due to dyspnea occurred in 0.9% of patients. Due to this risk of dyspnea, as well as the risk of elevated serum uric acid and creatinine, caution should be used in those with a history of COPD, asthma, CHF, gout, and CKD who are considering using ticagrelor.
Strengths of this study include that it was a double-blind, randomized controlled trial with a large patient population. Weaknesses include that the study was funded by AstraZeneca, manufacturers of Brilinta (the brand name of ticagrelor). Also, the study drug did not perform as well in North American sites or underweight patients, yet the authors do not offer clear explanations as to why.
Patients with a high risk of thrombosis and a low risk of bleeding may benefit most from ticagrelor. Ticagrelor has a mortality benefit when compared to clopidogrel. But ticagrelor should be used with caution in those with pulmonary disease (e.g. COPD or asthma), CKD, and heart block (due to association with ventricular pauses).
Drug cost: At time of study. Ticagrelor: $108/month; Clopidogrel: $26/month
1. Wiki Journal Club
2. 2 Minute Medicine
3. UpToDate, “Long-term antiplatelet therapy after coronary artery stenting in stable patients”
4. 2016 ACC/AHA Guideline Focused Update on Duration of Dual Antiplatelet Therapy in Patients with Coronary Artery Disease
Summary by Patrick Miller, MD