A noninferiority confirmatory trial of prasugrel versus clopidogrel in Japanese patients with non-cardioembolic stroke: rationale and study design for a randomized controlled trial – PRASTRO-I trial

An overview of the utility of prasugrel hydrochloride as a treatment option for ischemic stroke

INTRODUCTION

Prasugrel, a potent P2Y12 receptor inhibitor, is not currently recommended in patients with stroke due to a higher rate of recurrent stroke. Prasugrel was associated with comparable efficacy to clopidogrel in reducing the risk of ischemic stroke in a recent phase III study.

AREAS COVERED

The authors provide an overview of the potential role of prasugrel in the management of ischemic stroke. The authors searched PUBMED, MEDLINE, and clinicaltrials.org and recently presented trials at the conferences for clinical trials of prasugrel therapy in patients with stroke and TIA, and important original investigations are reviewed.

EXPERT OPINION

The recent PRASTRO-trials demonstrated comparable outcomes of lower maintenance dose (3.5 mg daily dose) with clopidogrel in East Asian stroke patients, thus can be a credible option as a P2Y12 receptor inhibitor. It can also be considered as a credible option in other races and ethnicities and in other clinical situations that may require DAPT, such as intracranial or carotid stenting. Since prasugrel is associated with a superior antiplatelet effect and is not influenced by genetic polymorphisms, there is no need for platelet function or genetic testing. More work is needed to establish the safety and efficacy of low-dose prasugrel plus aspirin in comparison with currently used clopidogrel plus aspirin in non-East Asian populations.

Blood Pressure Level and Variability During Long-Term Prasugrel or Clopidogrel Medication After Stroke: PRASTRO-I

BACKGROUND AND PURPOSE

High blood pressure increases bleeding risk during treatment with antithrombotic medication. The association between blood pressure levels and the risk of recurrent stroke during long-term secondary stroke prevention with thienopyridines (particularly prasugrel) has not been well studied.

METHODS

This was a post hoc analysis of the randomized, double-blind, multicenter PRASTRO-I trial (Comparison of Prasugrel and Clopidogrel in Japanese Patients With Ischemic Stroke-I). Patients with noncardioembolic stroke were randomly assigned (1:1) to receive prasugrel 3.75 mg/day or clopidogrel 75 mg/day for 96 to 104 weeks. Risks of any ischemic or hemorrhagic stroke, combined ischemic events, and combined bleeding events were determined based on the mean level and visit-to-visit variability, including successive variation, of systolic blood pressure (SBP) throughout the observational period. These risks were also compared between quartiles of mean SBP level and successive variation of SBP.

RESULTS

A total of 3747 patients (age 62.1±8.5 years, 797 women), with a median average SBP level during the observational period of 132.5 mm Hg, were studied. All the risks of any stroke (146 events; hazard ratio, 1.318 [95% CI, 1.094-1.583] per 10-mm Hg increase), ischemic stroke (133 events, 1.219 [1.010-1.466]), hemorrhagic stroke (13 events, 3.247 [1.660-6.296]), ischemic events (142 events, 1.219 [1.020-1.466]), and bleeding events (47 events, 1.629 [1.172-2.261]) correlated with increasing mean SBP overall. Similarly, an increased risk of these events correlated with increasing successive variation of SBP (hazard ratio, 3.078 [95% CI, 2.220-4.225] per 10-mm Hg increase; 3.051 [2.179-4.262]; 3.276 [1.172-9.092]; 2.865 [2.042-4.011]; 2.764 [1.524-5.016], respectively). Event rates did not differ between the clopidogrel and prasugrel groups within each quartile of SBP or successive variation of SBP.

CONCLUSIONS

Both high mean SBP level and high visit-to-visit variability in SBP were significantly associated with the risk of recurrent stroke during long-term medication with either prasugrel or clopidogrel after stroke. Control of hypertension would be important regardless of the type of antiplatelet drugs. Registration: URL: https://www.clinicaltrials.jp; Unique identifier: JapicCTI-111582.

Insights from Experiences on Antiplatelet Drugs in Stroke Prevention: A Review

Reduction of hazard risk of cerebral ischemic event (stroke, transient ischemic attack (TIA)) represents the hard point to be achieved from primary or secondary preventive strategy in the best clinical practice. However, results from clinical trials, recommendations, guidelines, systematic review, expert opinions, and meta-analysis debated on the optimal pharmacotherapy to achieve the objective. Aspirin and a number of antiplatelet agents, alone or in combination, have been considered from large trials focused on stroke prevention. The present review summarizes, discusses results from trials, and focuses on the benefits or disadvantages originating from antiplatelet drugs. Sections of the review were organized to show both benefits or consequences from antiplatelet pharmacotherapy. Conclusively, this review provides a potential synopsis on the most appropriate therapeutic approach for stroke prevention in clinical practice.

Efficacy and Safety of Prasugrel by Stroke Subtype: A Sub-Analysis of the PRASTRO-I Randomized Controlled Trial

Aims: The efficacy of antiplatelet therapy may vary among different disease subtypes. Prasugrel is generally a more potent, consistent, and fast-acting platelet inhibitor than clopidogrel. This sub-analysis of the phase III comparison of PRAsugrel and clopidogrel in Japanese patients with ischemic STROke (PRASTRO-I) trial aimed to assess the differences in efficacy of these treatments for each stroke subtype.

Methods: In the PRASTRO-I trial, a total of 3,753 patients with ischemic stroke were recruited from 224 centers throughout Japan and randomized (1:1) to prasugrel (3.75 mg/day) or clopidogrel (75 mg/day) for 96 weeks. For the sub-analysis, strokes were classified as large-artery atherosclerosis, small-artery occlusion (lacunar), stroke of other etiology, and stroke of undetermined etiology. The cumulative incidence of primary events (ischemic stroke, myocardial infarction, and death from other vascular cause) and hazard ratios (HRs) were calculated for each subgroup.

Results: For patients with large-artery atherosclerosis, the primary event incidence was 3.8% in the prasugrel group and 4.8% in the clopidogrel group (HR 0.79; 95% confidence interval [CI] 0.45–1.41). For patients with small-artery occlusion, the incidence was 3.3% in the prasugrel group and 3.9% in the clopidogrel group (HR 0.82; 95% CI 0.45–1.50). For patients with stroke of undetermined etiology, the incidence was 4.6% in the prasugrel group and 3.0% in the clopidogrel group (HR 1.56; 95% CI 0.90–2.72). The incidence of bleeding was similar across subtypes.

Conclusions: Although statistical significance was not reached, the efficacy of prasugrel was potentially different between stroke subtypes, warranting further studies.