Author + information
- Received October 12, 2011
- Revision received December 14, 2011
- Accepted December 20, 2011
- Published online May 8, 2012.
- Antonio Tello-Montoliu, MD, PhD,
- Salvatore D. Tomasello, MD,
- José Luis Ferreiro, MD,
- Masafumi Ueno, MD,
- Naveen Seecheran, MD,
- Bhaloo Desai, PhD,
- Murali Kodali, MD,
- Ronald K. Charlton, PhD,
- Lyndon C. Box, MD,
- Martin M. Zenni, MD,
- Luis A. Guzman, MD,
- Theodore A. Bass, MD and
- Dominick J. Angiolillo, MD, PhD⁎ ()
- ↵⁎Reprint requests and correspondence:
Dr. Dominick J. Angiolillo, Division of Cardiology, University of Florida College of Medicine–Jacksonville, 655 West 8th Street, Jacksonville, Florida 32209
Objectives The purpose of this study is to assess the pharmacodynamic effects of different prasugrel dosing regimens in patients on maintenance prasugrel therapy.
Background There are a growing number of patients on chronic prasugrel therapy regimens, leading to questions about the dosing regimen of prasugrel to administer if percutaneous coronary intervention is required.
Methods This is a prospective pharmacodynamic study in patients (n = 64) receiving maintenance prasugrel therapy who were randomly allocated to a 10 mg, 30 mg, or 60 mg dose of prasugrel. Pharmacodynamic assessments using multiple assays were conducted at 3 timepoints (baseline and 1 h and 4 h after dosing).
Results Intragroup comparisons showed that a 60 mg dose reduced the platelet reactivity index (PRI) after 1 h (p = 0.004) and 4 h (p < 0.001, primary endpoint; p = 0.002 between 1 h and 4 h). A 30 mg dose also reduced PRI levels at 1 h (p = 0.006) and 4 h (p < 0.001; p = 0.044 between 1 h and 4 h). A 10 mg dose was associated with modest pharmacodynamic effects. Intragroup comparisons showed similar findings with VerifyNow-P2Y12 and light transmission aggregometry. Intergroup comparisons showed that a 60 mg dose achieved lower PRI levels than 30 mg at 4 h (p = 0.05), and a numerical trend toward better pharmacodynamic effects at 1 h (p = 0.171). Intergroup comparisons were similar with VerifyNow-P2Y12, but not light transmission aggregometry.
Conclusions For patients on maintenance prasugrel therapy, a 60 mg dosing strategy is associated with faster and higher platelet inhibition compared with lower doses, as assessed by P2Y12 specific assays. (Impact of Prasugrel Re-load on Platelet Aggregation in Patients on Chronic Prasugrel Therapy; NCT01201772)
Dual antiplatelet therapy with aspirin and a P2Y12 receptor inhibitor is recommended for prevention of ischemic events in acute coronary syndrome (ACS) patients and patients undergoing percutaneous coronary interventions (PCI) (1). Prasugrel is a P2Y12 receptor inhibitor approved for the reduction of thrombotic cardiovascular events, including stent thrombosis, in ACS patients undergoing PCI (1,2). The greater ischemic benefit achieved with prasugrel compared with clopidogrel for ACS patients undergoing PCI has led to its increased utilization. However, recurrent atherothrombotic events may still occur in prasugrel-treated patients and may, therefore, necessitate further revascularization procedures. In addition, many patients may require subsequent revascularization due to chronic progression of their coronary atherosclerotic disease or for a staged PCI. Therefore, there is a growing number of patients who are undergoing PCI while on a regimen of chronic prasugrel therapy. That has raised concerns with regard to the optimal dosing of prasugrel in the peri-PCI period.
Study design and patient population
This is a prospective, randomized, open-label study designed to evaluate the pharmacodynamic effects of different prasugrel dosing regimens in patients on prasugrel maintenance therapy. Patients were randomly assigned to 1 of 3 prasugrel dosing regimens in a 1:1:1 fashion: 10 mg, 30 mg, or 60 mg. Prasugrel was administered as 10 mg tablets (Eli Lilly and Co., Indianapolis, Indiana). Blood sampling for pharmacodynamic testing was conducted at 3 timepoints: at baseline, and 1 h and 4 h after prasugrel dosing. The study design is illustrated in Figure 1. Patients were followed up to 7 days after completing the study to assess whether they experienced any adverse events.
Patients were screened at the outpatient clinics of our institution and considered eligible for the study if they were between 18 and 74 years of age and were receiving treatment with prasugrel 10 mg/day for at least 14 days. All patients were receiving aspirin 81 mg/day. Exclusion criteria for this study included active bleeding, prior cerebrovascular event, body weight <60 kg, age >75 years, clinical instability after the index event, use of oral anticoagulation agent, platelet count <100×106/μl, hemoglobin <10 g/dl, creatinine >2 mg/dl, hepatic enzymes >2.5 times the upper limit of normal, or pregnant/lactating female. The study was approved by our institutional review board, and all subjects provided written informed consent.
Blood sampling and pharmacodynamic tests
Patients withheld their dose of prasugrel the morning of their scheduled visit so that their last maintenance dose of prasugrel was 18 h to 24 h before baseline blood sampling to enable determination of trough levels of platelet reactivity. Citrated blood samples were processed by laboratory personnel blinded to treatment assignment. Platelet function assays included flow cytometric analysis of the phosphorylation status of the vasodilator-stimulated phosphoprotein (VASP) assay (Biocytex, Marseille, France), the VerifyNow P2Y12 (VN-P2Y12) assay (Accumetrics, San Diego, California), and light transmission aggregometry (LTA [Chrono-Log Corp., Havertown, Pennsylvania]). All assays were performed according to standard protocols as previously described. In brief, the VASP assay was used to determine the platelet reactivity index (PRI) (3,4). The VN-P2Y12 assay is a rapid whole blood point-of-care device that reports results as P2Y12 reaction units (PRU) and percent inhibition of platelet aggregation (%IPA) (3,4). The LTA was performed after 5 μmol/l and 20 μmol/l adenosine diphosphate stimuli, and results were reported as percentage maximum platelet aggregation (3,4).
Conformity to the normal distribution was evaluated for continuous variables with the Kolmogorov-Smirnov test. For baseline characteristics, continuous variables were expressed as mean ± SD, and categorical variables were expressed as frequencies and percentages. A repeated measures analysis of variance (ANOVA) model was used to evaluate the primary endpoint and all other intragroup comparisons. An analysis of covariance (ANCOVA) method with a general linear model, using the baseline value of the corresponding platelet function test as a covariate, was used to evaluate all exploratory between-groups comparisons. No adjustments for multiple comparisons were made. Results are reported as least-square mean ± SEM for the detailed analyses. Missing data were not imputed. In addition, p values for trend analyses to assess platelet reactivity when increasing loading dose (10 mg, 30 mg, and 60 mg) was performed with a polynomial contrast with the ANOVA method, considering loading dose as a categorical variable with an ordinal scale. A 2-tailed p value of <0.05 was considered to indicate a statistically significant difference for all the analyses performed. Statistical analysis was performed using SPSS version 16.0 software (SPSS Inc., Chicago, Illinois).
The primary endpoint was the comparison of PRI values between baseline and 4 h after reloading with 60 mg of prasugrel. Assuming a standard deviation of 18%, we would be able to detect an intragroup difference of 15% in PRI with 20 patients, with 90% power and a 2-tailed alpha value <0.05. The same sample size was used for the exploratory analyses performed in the 10 mg and 30 mg arms. Thus, considering a dropout rate of approximately of 8%, randomization of as many as 65 patients was allowed to ensure that complete pharmacodynamic data from 20 patients in each group were available for analysis.
Seventy-seven patients on maintenance prasugrel therapy were screened. Of these, 65 were randomized; 1 patient was withdrawn after randomization due to anemia identified after baseline blood sampling. Therefore, 64 patients (10 mg; n = 22; 30 mg, n = 21; and 60 mg, n = 21) completed the study. Patient disposition is illustrated in Figure 2. Baseline characteristics are described in Table 1. No bleeding complications or other adverse events were observed up to 7 days after study termination.
There were no differences in baseline PRI between groups (p = 0.577). Intragroup comparisons showed that PRI significantly reduced after a 60 mg and 30 mg prasugrel dose, but not with a 10 mg dose. In particular, prasugrel 60 mg reduced PRI levels at 1 h (p = 0.004) and 4 h (p < 0.001 between baseline and 4 h; p = 0.002 between 1 h and 4 h). Similarly, prasugrel 30 mg reduced PRI levels at 1 h (p = 0.006) and 4 h (p < 0.001, between baseline and 4 h; p = 0.044 between 1 h and 4 h). However, the use of prasugrel 10 mg was associated with a nonsignificant reduction in PRI, at 1 h (p = 0.355) and at 4 h (p = 0.776 from baseline; p = 0.458 between 1 h and 4 h). Intergroup comparisons showed that at 1 h after dosing, PRI levels were reduced significantly using 60 mg, whereas there was a large, but nonsignificant, decrease with a 30 mg versus a 10 mg dose (p = 0.058); there were no significant differences in PRI levels between 60 mg and 30 mg at 1 h (p = 0.171). At 4 h after dosing, 60 mg and 30 mg continued to have lower PRI levels than 10 mg (60 mg vs. 10 mg, p < 0.001; 30 mg vs. 10 mg, p < 0.001); in addition, 60 mg prasugrel was associated with lower PRI compared with 30 mg (p = 0.05). Trend analyses observed better platelet inhibitory effects with higher prasugrel doses at both 1 h and 4 h (Fig. 3).
Similar results were observed with the VN-P2Y12 assay. Intragroup comparisons showed enhanced platelet inhibitory effects with prasugrel 60 mg and 30 mg, as measured by both PRU and %IPA, at 1 h and 4 h (Table 2). Prasugrel 10 mg was associated with modest platelet inhibitory effects, which reached statistical significance at 4 h. Intergroup comparisons showed that prasugrel 60 mg and 30 mg doses had lower PRU and higher %IPA at 1 h and 4 h after dosing compared with prasugrel 10 mg. Prasugrel 60 mg was associated with significantly lower PRU and higher %IPA levels compared with 30 mg at 1 h. Although platelet inhibitory effects increased over time with the 60 mg and 30 mg doses, the differences in PRU and %IPA were no longer statistically significant at 4 h (Figs. 4A and 4B).
Similar to VN-P2Y12 testing, intragroup comparisons showed marked platelet inhibitory effects as assessed by LTA with prasugrel 60 mg and 30 mg at 1 h and 4 h, and modest effects—which, however, reached statistical significance at 4 h—with prasugrel 10 mg (Table 2). Intergroup comparisons showed that prasugrel 60 mg and 30 mg both achieved greater reduction in maximal percentage platelet aggregation compared with 10 mg at 1 h and 4 h. Although prasugrel 60 mg was associated with lower platelet reactivity compared with 30 mg at both 1 h and 4 h, this did not reach statistical significance (Figs. 5A and 5B).
The introduction into clinical practice of the third-generation thienopyridine prasugrel has led to questions about the optimal dosing regimen of this agent for patients undergoing PCI who are already receiving chronic treatment. In particular, concerns about the adequacy of platelet inhibition if no additional load is given as well as the potential for increased risk of bleeding with reloading have emerged. A parallel scenario came forward several years ago for patients on a regimen of chronic clopidogrel therapy who were undergoing PCI (5,6). The present investigation is novel in that it evaluates the pharmacodynamic impact of different prasugrel dosing regimens on patients receiving chronic prasugrel therapy. Patients were randomly allocated to 3 different regimens, and findings showed that the use of a 30 mg or 60 mg dose of prasugrel was associated with enhanced platelet inhibitory effects during the entire course of the study compared with a 10 mg dose, for which only modest effects were observed. Importantly, these effects occurred rapidly, with significant differences observed 1 h after dosing. Further, we observed that a 60 mg dosing regimen was associated with enhanced platelet inhibition compared with 30 mg at various timepoints when assessed with P2Y12-specific assays. Ultimately, a 60 mg dose was associated with rapid effects as demonstrated by the levels of platelet reactivity achieved at 1 h, which were either similar or greater than those achieved by a 30 mg dose at 4 h.
To date, various studies have assessed the pharmacodynamic effects of prasugrel therapy in ACS patients who had been already on treatment with clopidogrel and have demonstrated that switching to prasugrel is associated with enhanced platelet inhibition and that this can be achieved more promptly (within 2 h) and with greater potency using a 60 mg compared with a 10 mg dose (4,7). Although a prasugrel 15 mg maintenance dose is associated with more potent platelet inhibition compared with a 10 mg dose, this increased minimal bleeding rates, which represents the rationale for using 10 mg prasugrel (2,8). Overall, there is evidence to suggest that there is room for further increase in platelet inhibition in patients on 10 mg therapy after the administration of a prasugrel loading dose, as confirmed in this study. Moreover, more potent and prompt effects were observed with a 60 mg dose compared with a 30 mg dose when assessed by VASP-PRI and VN-P2Y12, but not with LTA. These differences may be attributed to VASP-PRI and VN-P2Y12 being more specific to assess the effects on P2Y12 receptor signaling, while adenosine diphosphate induced LTA results are more reflective of overall purinergic-mediated platelet aggregation (9,10).
Platelet P2Y12 receptor blockade is pivotal in ACS patients undergoing PCI (11). In clopidogrel-treated patients undergoing PCI, high platelet reactivity is associated with ischemic events (9,10), suggesting the need for more aggressive antithrombotic treatment, such as a reload, if these patients undergo subsequent revascularization procedures. Randomized studies showed clopidogrel reloading to be associated with further platelet inhibition and a reduction in ischemic events, including stent thrombosis (12,13). Therefore, the results of the present pharmacodynamic investigation using prasugrel may also have potential clinical implications. Further, prasugrel-treated patients may still present with high platelet reactivity, making them at risk for atherothrombotic recurrences (14). These findings, as well as the lower levels of platelet inhibition with prasugrel during maintenance therapy compared with that achieved after acute loading (3,4,7,8), support that patients on chronic therapy may require additional dosing in the peri-PCI setting. Although the optimal level of platelet inhibition required to minimize ischemic complications in patients undergoing PCI remains elusive, numerous studies support the importance of enhanced platelet inhibition in the peri-PCI period (9,10). Our observations showing that a 60 mg dose consistently showed more prompt and potent platelet inhibitory effects by P2Y12 specific assays suggest the potential for a clinical application of this dosing regimen for patients on maintenance prasugrel therapy who require PCI.
This investigation was powered to assess intragroup comparisons but not intergroup comparisons. Therefore, the latter results should be considered as exploratory. In addition, our pharmacodynamic study was not conducted in patients undergoing PCI and was not powered to assess safety or efficacy. Hence, the lack of bleeding complications, including extrapolations to arterial access site complications, in this study should be interpreted with caution.
For patients on a maintenance prasugrel therapy regimen, prasugrel reloading with a 60 mg dose is associated with more rapid and enhanced platelet inhibition compared with lower doses as assessed by P2Y12 specific assays. The clinical implications of prasugrel reloading in patients on maintenance prasugrel therapy undergoing PCI warrant further investigation.
This investigator-initiated study was funded by a research grant provided by Daiichi Sankyo and by LillyUSA to the University of Florida College of Medicine, Jacksonville (Principal Investigator: Dominick J. Angiolillo, MD, PhD). Dr. Tello-Montoliu is a recipient of a scholarship financed by the Ministry of Education (Spain), through the National Human Resources Mobility I-D i 2008–2011 National Plan 2008–2011. Dr. Ferreiro has received honoraria for lectures from Eli Lilly Co. and Daiichi Sankyo, Inc. Dr. Box is on the Speaker's Bureau of and has received honoraria from AstraZeneca. Dr. Zenni has received honoraria for being on the Speaker's Bureau for Eli Lilly and Co. and Daiichi Sankyo, Inc. Dr. Guzman has received consulting fees from AstraZeneca and Merit Medical; and is on Speaker's Bureau of AstraZeneca. Dr. Angiolillo has received honoraria for lectures from Bristol-Myers Squibb, Sanofi-Aventis, Eli Lilly and Co., Daiichi Sankyo, Inc., and AstraZeneca; has received consulting fees from Bristol-Myers Squibb, Sanofi-Aventis, Eli Lilly and Co., Daiichi Sankyo, Inc., The Medicines Company, Portola, Novartis, Medicure, Accumetrics, Arena Pharmaceuticals, Abbott Vascular, AstraZeneca, Merck, and Evolva; and has received research grants from Bristol-Myers Squibb, Sanofi-Aventis, GlaxoSmithKline, Otsuka, Eli Lilly and Co., Daiichi Sankyo, Inc., The Medicines Company, Portola, Accumetrics, Schering-Plough, AstraZeneca, and Eisai. All other authors have reported they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- acute coronary syndrome
- light transmission aggregometry
- percutaneous coronary intervention
- platelet reactivity index
- P2Y12 reaction units
- vasodilator-stimulated phosphoprotein
- Received October 12, 2011.
- Revision received December 14, 2011.
- Accepted December 20, 2011.
- American College of Cardiology Foundation
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