Author + information
- Received December 3, 2010
- Revision received February 8, 2011
- Accepted March 8, 2011
- Published online April 1, 2011.
- Jean-Philippe Collet, MD, PhD⁎,
- Jean-Sébastien Hulot, MD, PhD†,
- Ghalia Anzaha, BSc⁎,
- Ana Pena, PhD⁎,
- Thomas Chastre, MD⁎,
- Claire Caron, MD‡,
- Johanne Silvain, MD, PhD⁎,
- Guillaume Cayla, MD⁎,
- Anne Bellemain-Appaix, MD⁎,
- Jean-Baptiste Vignalou, MD⁎,
- Sophie Galier, BSc⁎,
- Olivier Barthélémy, MD⁎,
- Farzin Beygui, MD, PhD⁎,
- Vanessa Gallois, BSc⁎,
- Gilles Montalescot, MD, PhD⁎,⁎ (, )
- CLOVIS-2 Investigators
- ↵⁎Reprint requests and correspondence:
Prof. Gilles Montalescot, Bureau 236, Institut de Cardiologie, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013 Paris, France
Objectives This study sought to determine whether the pharmacokinetic (PK) and pharmacodynamic (PD) responses to high or standard clopidogrel loading doses (LDs) differ according to CYP2C19*2 allele.
Background CYP2C19 loss-of-function alleles are associated with reduced responsiveness to standard clopidogrel doses.
Methods Young post-myocardial infarction patients heterozygous (wild type [wt]/*2, n = 43) or homozygous (*2/*2, n = 8) for the CYP2C19*2 genetic variant were matched with patients not carrying the variant (wt/wt, n = 58). All patients were randomized to a 300- or 900-mg clopidogrel LD. The relative reduction in residual platelet aggregation (RR-RPA, %) and the area under the plasma concentration time curve of active metabolite from baseline to 6 h after loading (AUC0-6) were compared according to both LD and CYP2C19*2 carriage.
Results The 300-mg LD led to a gene-dose effect for RR-RPA (−65.7% ± 35.9% in wt/wt vs. −48.0% ± 38.4% in wt/*2 vs. −14.6% ± 32.4% in *2/*2; overall p value = 0.003, p = 0.03 for wt/wt versus wt/*2, p = 0.04 for wt/*2 versus *2/*2) with minor effect in *2/*2 carriers. After the 900-mg LD, the effect of the CYP2C19*2 variant on platelet inhibition was fully compensated in wt/*2 carriers but not in *2/*2 carriers (−83.6% ± 25.8% in wt/wt vs.−77.2% ± 26.9% in wt/*2 vs. −29.5% ± 26.8% in *2/*2; overall p value = 0.0003, p = 0.20 for wt/wt versus wt/*2, p < 0.001 for wt/*2 versus *2/*2). A similar pattern was observed for the active metabolite AUC0-6 according to carriage of CYP2C19*2 for both LDs. There was a significant correlation between PK and PD responses irrespective of the LD.
Conclusions Carriers of CYP2C19*2 display significantly lower responses to clopidogrel with a gene-dose effect. Clopidogrel resistance can be overcome by increasing the dose in heterozygous carriers but not in homozygous carriers. (Clopidogrel and Response Variability Investigation Study 2 [CLOVIS-2]; NCT00822666)
Clopidogrel inhibits the P2Y12 adenosine diphosphate (ADP) receptor on platelets and has been the standard of care in combination with aspirin to prevent cardiovascular events in patients with an acute coronary syndrome (ACS) and/or undergoing percutaneous coronary intervention (PCI). The “one size fits all” treatment strategy with clopidogrel therapy does not take into account the large degree of interindividual pharmacodynamic (PD) responses, and patients with lesser degrees of platelet inhibition and/or higher residual platelet reactivity on clopidogrel are at increased risk of cardiovascular events (1). Several studies have shown that higher clopidogrel loading doses (LDs) result in higher platelet inhibition, faster onset of action, and fewer poor responders in a dose-effect fashion in both clopidogrel-naive and clopidogrel-treated patients (2,3). Although some of these studies suggested that high or very high LDs of clopidogrel afford greater clinical benefit compared with the 300-mg LD (4,5), it is only recently that it has been demonstrated in patients presenting with an ACS and undergoing PCI (6).
Cytochrome P-450 (CYP) isoenzymes contribute substantially to the 2 oxidative steps necessary for the transformation of clopidogrel into its active thiol metabolite (7). Carriers of reduced-function genetic variants *2 to *8 in CYP2C19 gene—the *2 allele being the most frequent variant (>90%), found in one-third of all comers—have lower active metabolite levels and diminished platelet inhibition (8). Carriage of even 1 reduced-function CYP2C19 allele among coronary patients on clopidogrel is associated with an approximately 20% increased risk of cardiovascular death as compared with noncarriers, and an approximately 3-fold increase in the risk of stent thrombosis (9). This hazard seems to be present both early after initiation of clopidogrel therapy and later during long-term secondary prevention.
Recently, the U.S. Food and Drug Administration (FDA) issued a warning suggesting that there is diminished effectiveness of standard doses of clopidogrel in individuals with 2 reduced-function CYP2C19 alleles and that genetic tests may be useful to identify patients at risk and to consider alternative treatment strategies (10). The warning only addresses patients with 2 loss-of-function alleles (*2/*2), representing approximately 2% of Caucasians, 4% of the black population, and up to 20% of Chinese (11). No comment is provided for heterozygous patients (wt/*2), who represent more than 90% of carriers and approximately one-third of the population, although pharmacokinetic (PK) and PD studies have shown that even 1 reduced-function CYP2C19 allele has a significant impact on the response to clopidogrel (8). Whether increasing the dose of clopidogrel in carriers of 1 or 2 CYP2C19 reduced-function alleles can improve the degree of platelet inhibition is unknown (12–14).
To determine whether response to high or standard clopidogrel LDs differs according to the presence of 1 or 2 CYP2C19 reduced-function alleles, we conducted a prospective randomized evaluation of 2 clopidogrel LDs in a gene-based selected population of young post-myocardial infarction (MI) survivors.
Selection of patients
To enter the CLOVIS-2 (Clopidogrel and Response Variability Investigation Study 2) patients were screened from the AFIJI (Appraisal of risk Factors in young Ischemic patients Justifying aggressive Intervention) multicenter registry (n = 566) (15). A total of 292 male patients with DNA samples were genotyped for the CYP2C19*2 genetic variant. All homozygous and heterozygous CYP2C19*2 patients were proposed to participate in the randomized CLOVIS-2 study. Age- and gender-matched homozygous CYP2C19 wild-type (wt)/wt patients (noncarriers) from the same AFIJI program were then recruited with a 1:1 ratio for each heterozygous and a 2:1 ratio for each homozygous patient who was willing to participate. Exclusion criteria were any conditions requiring chronic treatment with nonsteroidal anti-inflammatory drugs or any chronic anticoagulant treatment.
The trial was conducted by the ACTION Academic Research Organization (Institut de Cardiologie–Pitié-Salpêtrière Hospital), sponsored by the Direction de la Recherche Clinique at Assistance Publique-Hôpitaux de Paris (AP-HP) and funded by a public grant from the Programme Hospitalier de Recherche Clinique (PHRC P070117) of the French Ministry of Health. The sponsor had no involvement in the design of the study, data collection, analysis, or the writing of the manuscript. The protocol was approved by the Pitié-Salpêtrière University Hospital Ethics Committee. Written informed consent was obtained from all patients.
All patients had survived an MI before the age of 45 years, were stable at the time of inclusion, and were all treated with a maintenance dose (MD) of 75 mg of aspirin and/or 75 mg of clopidogrel for at least 3 months. They were randomly assigned (web-centralized randomization procedure) to an open-label LD of 300 or 900 mg of clopidogrel in a 2-period crossover fashion (Fig. 1). All investigations and blood sample timings were identical in the 2 phases of the study. Briefly, patients received an initial load of either 300 or 900 mg according to randomization. Blood was drawn for PD evaluations at baseline before loading and 6 h after drug loading. Blood samples were also collected for PK analyses at baseline, 1, 2, 4, and 6 h post-loading. A clopidogrel 75-mg MD was continued at least 21 days before patients were crossed over to the alternate LD of clopidogrel, and the same measurements were performed again.
Genomic DNA was extracted from peripheral blood and was genotyped using TaqMan Validated SNP assays (C_25986767_70) with the 7900HT sequence Detection System (Applied Biosystems, Courtaboeuf, France). All patients were also genotyped for other loss-of-function CYP2C19 variants (*3, *4, *5, *6) using the same method (TaqMan Validated SNP assays: C_27861809_10; C_30634136_10; C_27861810_10; and C_27531918_10, respectively).
Platelet measurements were performed immediately after venipuncture in a single laboratory blinded to the assigned LD regimen and to the genetic profile of the study patients. Light transmission aggregometry (LTA) (Model 490-4D, Chrono-Log Corporation, Kordia, the Netherlands) and the point-of-care assay (POC) VerifyNow P2Y12 (VN-P2Y12) assay (Accumetrics, San Diego, California) were both used simultaneously at baseline (before the LD) and 6 h after the LD during both phases. Residual platelet aggregation (RPA), which corresponded to the level of aggregation curve (%) measured 6 min after 20 μmol/l ADP-induced platelet aggregation, was selected because it is thought to better reflect P2Y12 function than other measurements (16). The relative reduction (RR) in RPA (RR-RPA, %) 6 h post-LD was defined as (% RPA6 h) − (% RPAbaseline)/(% RPAbaseline) × 100. Pre-specified criteria to define nonevaluable samples were the lack of sufficient signal, hemolysis, PRP platelet count <150,000/μl, and unstable baseline.
For the VN-P2Y12 assay, samples were run in the same laboratory, according to the device package insert. Platelet reaction units (PRU) were reported and correlated to RPA at each time point.
Measure of Plasma Concentration of Active Metabolite
Whole blood was immediately stabilized with 500 mM MPBr (3-methoxyphenacyl bromide) and processed to obtain platelet-poor plasma aliquots, and then stored at −80°C. Plasma concentration of active metabolite isomers stabilized as 3′methoxyacetophenone derivates was determined by a validated electrospray liquid chromatography tandem mass spectrometry method. Data on the active metabolite isomer H4 were reported because isomer H3 was inactive and isomers H1 and H2 were nonquantifiable (17).
The area under the plasma concentration time curve (AUC) from the time of administration of the LD to 6 h (AUC0-6) of active metabolite was computed by noncompartmental methods of analysis with the use of the log-linear trapezoidal method (Phoenix WinNonlin, version 6.0, Pharsight, St. Louis, Missouri).
The primary aim was to evaluate RR-RPA after 300- and 900-mg clopidogrel LDs according to the CYP2C19*2 genotype.
Other endpoints were the rate of high on-treatment platelet reactivity (HOPR) according to established cutoff values for both methods (64.5% for 20 μM ADP, 236 PRU for VN-P2Y12 assay) (1), the relative reduction in platelet aggregation expressed as P2Y12 PRU (RR-PRU) measured with the VN-P2Y12 assay according to CYP2C19*2 genotype, and the correlation between RR-RPA and AUC0-6 for both LDs. An analysis was performed according to clopidogrel pretreatment status.
The sample size was calculated to demonstrate that the administration of a 300-mg LD would produce a 40% lower RR-RPA in carriers of CYP2C19*2 as compared with the effect observed in noncarriers according to a previous difference of 50% reported in healthy volunteers (18). To demonstrate such a difference, the inclusion of 45 carriers was required to yield 90% power with an alpha-risk error of 0.05 and assuming a 20% standard deviation for the difference between regimens.
Continuous variables were expressed as mean ± SD unless otherwise stated, and categorical variables as frequencies and percentages. Baseline characteristics of patients by genotypes were compared using the chi-square test for categorical variables, and Student t test or 1-way analysis of variance for continuous variables as appropriate. For RPA measures, data were included for subjects with evaluable RPA measurements at baseline and 6 h in both phases. The PD response to clopidogrel was primarily defined as RR-RPA (%) to adjust for pre-treatment status with clopidogrel MD. After checking for the absence of carryover effect, the comparison between clopidogrel response across genotype groups and the 2 LDs tested (300-mg vs. 900-mg LD) was evaluated by the Kruskall-Wallis test. Two-sided unpaired Wilcoxon test was then used to compare endpoints between 2 genotypes. Only patients who successfully completed the 2 treatment periods of the study were considered for analysis. A similar approach was used for the PK response defined as AUC from the time of administration of the LD to 6 h. The clopidogrel PK/PD relationship was evaluated by nonlinear regression analysis. The best fit was obtained with hyperbolic decay model with a baseline of the following form: E = ab/b + AUC0-6. The effect (E) was RR-RPA obtained after 300-mg and 900-mg LDs.
Comparisons are expressed as univariate hazard ratios and 95% confidence intervals, including the entire duration of follow-up. All analyses were performed with the use of SAS software, version 9.1 (SAS Institute, Cary, North Carolina). All p values are 2 sided.
A total of 43 heterozygous carriers (wt/*2) were matched in a 1:1 ratio with 43 wt homozygous (wt/wt) patients, and 8 (6.6%) homozygous carriers (*2/*2) were matched in a 1:2 ratio with 16 wt homozygous (wt/wt) patients, constituting then a population of 110 coronary patients to be randomized to 1 or the other LD of clopidogrel. Fifty-five patients started with the 300-mg LD regimen and 55 with the 900-mg LD regimen. At the final stage, 106 completed the 2 periods of the randomized CLOVIS-2 study (58 wt/wt, 41 wt/*2, and 7 *2/*2, respectively). Four patients were heterozygous carriers of the CYP2C19*4 variant, whereas CYP2C19*3, -*5, or -*6 was not found in any of the patients. In the overall genotyped patients, there was no deviation from the expected proportions of genotypes predicted by the Hardy-Weinberg equilibrium for polymorphisms (p > 0.40).
Baseline characteristics were representative of a typical young MI population. No statistical difference between the randomized sequences was found, including for the baseline value of RPA (data not shown). A total of 86 patients were treated by a MD of clopidogrel at baseline and for at least 3 months prior to entering the study. Naive patients (n = 20) prior to randomization were not treated with a MD between the 2 sequences. Patients had a high prevalence of familial history of coronary artery disease. Baseline characteristics were well balanced between the 2 groups defined by CYP2C19*2 genotypes (Table 1).
Pharmacodynamic response to clopidogrel according to the CYP2C19*2 genetic variant
Baseline RPA and maximal platelet aggregation (MPA) differed significantly according to CYP2C19*2 carriage in patients on 75-mg clopidogrel MD (n = 86) with a significant gene-dose effect (Tables 2 and 3).⇓ The lowest average RPA/MPA was observed in wt/wt patients, and the highest in patients with 2 CYP2C19 reduced-function alleles (*2/*2) (Fig. 2). A similar pattern was observed when measuring the P2Y12 PRU (Table 3). These differences were not observed in clopidogrel-naive patients. The effect of the LD was then assessed in the whole population irrespective of clopidogrel pre-treatment prior to loading (n = 106). There was a stepwise decrease of RR-RPA from wt/wt to carriers, with a significant gene-dose effect following the 300-mg LD (Fig. 3). The maximal RR-RPA was observed in wt/wt and was significantly lower in carriers with an intermediate effect in wt/*2. Indeed, whereas the 300-mg LD resulted in a significant reduction in platelet aggregation in wt/wt and wt/*2 patients, there was no detectable effect on RPA or MPA in *2/*2 carriers (RPA/MPA [%]: 65.43 ± 11.23 and 67.27 ± 10.60 before vs. 60.10 ± 28.75 and 66.97 ± 23.91 after loading, respectively, p = ns for both measurements). The 900-mg LD blunted the effect of the CYP2C19*2 variant on RR-RPA in wt/*2, which did not differ from wt/wt (Fig. 3). In contrast, there was little effect of the 900-mg LD in *2/*2 carriers. Further statistical analyses according to CYP2C19*2 genotype confirmed that a gene-dose effect was observed following the 300-mg LD but not following the 900-mg LD (Fig. 3). This pattern was also observed when considering MPA (data not shown).
The magnitude of change in RR-RPA according to CYP2C19*2 carriage appeared to be similar in patients treated by a MD of clopidogrel (n = 86) and in clopidogrel-naive patients (n = 20) (Tables 2 and 3), and there was no significant interaction of pre-treatment status and CYP2C19*2 carriage on all PD parameters. Pharmacodynamic response evaluated by the POC VN-P2Y12 assay led to a similar pattern as with ADP-induced RPA (LTA) with respect to genetic variants and LDs (Table 3). The prevalence of HOPR, defined according to LTA established cutoff values (1), increased with respect to the number of reduced-function CYP2C19 alleles, although it was blunted after administration of the 900-mg LD in patients carrying a single allele (Table 2). HOPR was much less frequent according to the established cutoff of PRU (>235) with no significant gene-dose effect as observed with LTA (Table 3). No statistically significant differences were observed by sequence or period, and there was no treatment–period interaction, suggesting no carryover effect.
Carriers of the CYP2C19*2 variant displayed reduced plasma concentration of the active metabolite compared with wt/wt, with a significant gene-dose effect after exposition to both LDs (Fig. 4). There was no detectable difference in active metabolites levels achieved after 300-mg LD between wt/*2 and *2/*2 (p = 0.13). Compared with the levels observed after a 300-mg LD, the 900-mg LD led to a 2-fold increase in active metabolite concentration in wt/wt and wt/*2 patients (Fig. 4). This concentration was also increased by 1.5-fold in *2/*2 patients. The gene-dose effect was present with both LDs but was stronger with the 900-mg LD. Interestingly, *2/*2 carriers still displayed a reduced PK response after 900-mg LD, with similar levels to those measured after the 300-mg LD in wt/*2 carriers. There was no influence of clopidogrel pre-treatment status (Table 4).
There was a significant and similar relationship between active metabolite plasma concentrations (AUC0-6, in ng · h/ml) and RR-RPA following both LDs (Figs. 5A and 5B) with a right shift of the 900-mg LD curve. The lowest AUC0-6 (<10 ng · h/ml) values were associated with a great variability of PD, which was not observed with the 900-mg LD. The PK/PD relationship suggests that isomer H4 metabolite AUC0-6 >20 ng · h/ml is necessary to obtain a meaningful inhibitory effect of clopidogrel loading, although this latter remains still highly variable. Such levels were more likely achieved in wt/wt patients and/or after 900-mg LD. An isomer H4 metabolite AUC0-6>50 ng · h/ml was associated with maximal antiplatelet effect.
By pairing patients according to their genetic background and by assessing simultaneously PD and PK responses after exposure to 2 different clopidogrel doses randomly allocated, we demonstrate that carriage of the loss-of-function CYP2C19*2 variant is associated with: 1) a gene-dose response to a standard clopidogrel 300-mg LD and 75-mg MD; and 2) a correction of the genetic trait effect by using a higher dose of the drug, which is, however, limited to heterozygous patients. Indeed, in wt/*2 heterozygous patients, the 900-mg LD totally compensated for the genetic deficiency on both the active metabolite concentration and platelet inhibition, which finally did not differ from wt/wt patients. In contrast, *2/*2 carriers still displayed a reduced PK/PD response with the 900-mg LD.
Recent meta-analyses have suggested that heterozygous and homozygous carriers of the reduced-function CYP2C19*2 allele experience diminished clinical effectiveness of clopidogrel after PCI and/or ACS (9). Heterozygous carriers of the CYP2C19 reduced-function allele represent the vast majority of carriers and are at significantly higher risk of adverse cardiovascular events as compared with wt/wt patients. Homozygous *2/*2 carriers are also at higher risk than wt/*2 but with overlapping confidence intervals of the point estimates. These clinical data are now supported by the results of our CLOVIS-2 randomized study, designed with an enrichment strategy in which patients were selected according to the presence of the CYP2C19*2 genetic variant, allowing a more accurate evaluation of 1 versus 2 reduced-function CYP2C19 alleles. Clopidogrel MDs and LDs have an incremental PK/PD effect according to the presence of 1 or 2 CYP2C19*2 alleles. The consistent findings on PK and PD with the 75-mg MD and 2 different LDs strongly suggest a gene-dose effect of the CYP2C19*2 variant and possibly a codominant effect.
CLOVIS-2 evaluated the effect of 2 different LDs in a randomized fashion according to the presence of the reduced-function CYP2C19*2 allele. The labeled 300-mg LD appears adequate in the majority of patients with the wt/wt genotype but appears insufficient in carriers of at least 1 reduced-function CYP2C19*2 allele. The 900-mg LD was chosen because it was shown to be superior to both 300 and 600 mg to reduce poor clopidogrel response, in both naive patients and patients already taking 75 mg/day clopidogrel (2,3). Importantly, in contrast to a previous study looking at the effect of 600-mg LD (19), it has been demonstrated that in the dose range of 900 mg, there was no limitation due to intestinal absorption (2). CLOVIS-2 further demonstrates that we can overcome genetic resistance to clopidogrel in heterozygous wt/*2 carriers already on a clopidogrel MD by using this 900-mg LD. Indeed, PD and PK responses in wt/*2 carriers significantly differ from that of wt/wt patients with the standard clopidogrel dosing regimen but are normalized with the 900-mg LD. This further extends our previous report on a high clopidogrel MD to overcome poor responsiveness in wt/*2 patients (12).
CLOVIS-2 also demonstrates that *2/*2 carriers responded poorly to both LDs suggesting a profile of complete resistance to clopidogrel. This further supports that a strategy of an increased clopidogrel-dose regimen is ineffective, as previously reported in patients who survived a stent thrombosis and who have both persistent HOPR and a genetic profile of resistance (13). These patients deserve alternative therapy and should be switched to novel and more effective P2Y12 inhibitors such as prasugrel, although no definitive conclusion can be drawn, given the small number of *2/*2 patients and a better response in pre-treated patients versus naive patients (13). Altogether, these results suggest that therapy individualized on the genetic profile is possible with standard treatment in homozygous wt/wt patients, increased clopidogrel dosing in heterozygous wt/*2 carriers, and new P2Y12 antagonists in homozygous *2/*2 carriers, to reach an appropriate range of P2Y12 inhibition in all patients. Although the evidence base for such an option currently does not exist, these new data may help in interpreting the recommendations recently released by the American College of Cardiology/American Heart Association on pharmacogenetic testing to identify patients' altered clopidogrel metabolism (20). The CLOVIS-2 study also suggests that a study design with genotype enrichment in a population at risk is feasible and may represent a novel approach for evaluating personalized medicine.
The CLOVIS-2 study shows that the association between the presence of a reduced-function CYP allele and platelet inhibition is primarily due to reduced plasma exposure to the active metabolite of clopidogrel. We confirm a significant gene-dose effect of CYP2C19*2 and a drug-dose effect in these patients, both at the PK and PD levels. The clopidogrel active metabolite is a mixture of 4 unstable diastereoisomers, which remain a technical challenge to measure, especially if clopidogrel is used as the reference to establish the calibration curve (17). To avoid such limitations, concentrations of individual stabilized isomers were determined, and the H4 isomer, the only diastereoisomer of clinical relevance for documenting the PK profile of clopidogrel's active metabolite, was taken into account using a method that was validated in compliance with the FDA guidelines.
Our results provide new insights in the understanding of clopidogrel metabolism. The use of a higher LD in CYP2C19-deficient patients (i.e., *2/*2) results in an increase in the isomer H4 active metabolite levels (from 9.94 ± 2.88 ng · h/ml to 15.84 ± 5.26 ng · h/ml for 300-mg and 900-mg LDs, respectively, p = 0.007, see Fig. 4), suggesting a CYP2C19-independent metabolic pathway that could be linked to other cytochromes such as CYP3A4 or CYP1A2 (7). Of interest, this increase in isomer H4 active metabolite with 900 mg reaches levels identical to those measured with 300 mg in wt/*2 patients but does not translate into a similar degree of platelet inhibition measured either with LTA or the POC VN-P2Y12 assay. This disconnect between PK and PD remains to be elucidated, and could possibly be related to other unknown active metabolites via the CYP2C19-dependent pathway. This may explain also why low isomer H4 levels weakly predict the antiplatelet effect irrespective of the PD assay (21). It should be acknowledged that the correlation between PK and PD responses does not reflect the association in a single population but rather reflects the effect of CYP2C19*2 carriage.
First, 80% of our study population were white patients, so these results might be relevant to only whites although the effects of CYP2C19 reduced-function alleles on platelet inhibition with clopidogrel appear to be consistent irrespective of ethnicity. Second, whether our findings obtained in a young post-MI population can be extrapolated to elderly patients with comorbidities, where clopidogrel has more modest efficacy, remains to be established. Third, whether a double MD of clopidogrel (150 mg), a dose that leads to significantly increased platelet inhibition and decreased rate of HOPR but with no established clinical benefit (6), may overcome the effect of the *2 allele is unlikely, given the lack of effect of the 300-mg LD and recent findings of the ACCEL-DOUBLE (Accelerated Platelet Inhibition by a Double Dose of Clopidogrel According to Gene Polymorphism) trial (22). A loading dose higher than 900 mg was not evaluated, given our study design and prior results of the RELOAD (Reload with Clopidogrel Before Coronary Angioplasty in Subjects Treated Long Term with Dual Antiplatelet Therapy) study showing no significant difference in platelet inhibition between 300- and 600-mg reloading strategies in patients on a MD of clopidogrel (2). In addition, LDs higher than 900 mg have a very modest effect on clopidogrel response in *2/*2 carriers (23). The number of homozygous carriers is low and could not be increased in this genotype enrichment study design, and this may account for the different distribution of baseline characteristics through the genotype groups. Sample size calculation was performed irrespective of the allele carriage status as opposed to statistical analyses that were performed ignoring the matching process by randomized tests for pragmatic reason given the recent FDA warning on the CYP2C19*2 carriage status. Finally, evaluations of clinical outcome and of hyper response were omitted, given the limited study population, and would deserve further evaluation.
The CLOVIS-2 investigation answers many of the concerns raised by the FDA (10) and may help interpreting the American College of Cardiology/American Heart Association recommendations on pharmacogenetic testing to identify patients' altered clopidogrel metabolism (20). A high clopidogrel dose can overcome poor response to the drug in heterozygous carriers of the CYP2C19*2 genetic variant but not in homozygous carriers, who probably deserve alternative therapy. CLOVIS-2 results suggest a codominant effect of this loss-of-function allele and that genotyping of thienopyridine-eligible patients may help individualize antiplatelet therapy, something being tested now in prospective studies (Genotyping Infarct Patients to Adjust and Normalize Thienopyridine Treatment [NCT01134380]; Genotype Guided Comparison of Clopidogrel and Prasugrel Outcomes study [NCT00995514)]; and TARGET-PCI [Thrombocyte Activity Reassessment and GEnoTyping for PCI] NCT01177592)).
The authors acknowledge Unité de Recherche Clinique of the Pitié-Salpêtrière Hospital for data monitoring, and Fabrice Hurbin, Phd, for discussion and interpretation of active metabolite dosages.
This work was sponsored by the Direction de la Recherche Clinique at Assistance Publique-Hôpitaux de Paris (AP-HP) and funded by a public grant from the French Ministry of Health (PHRC P070117). Prof. Collet has received research grants (to the institution) from Bristol-Myers Squibb, Sanofi-Aventis, Eli Lilly, Guerbet Medical, Medtronic, Boston Scientific, Cordis, Stago, Fondation de France, INSERM, Fédération Française de Cardiologie, and Société Française de Cardiologie; and has served as a consultant to and received lecture fees from Sanofi-Aventis, Eli Lilly, and Bristol-Myers Squibb. Dr. Hulot reports receiving research grant support from Fondation de France, INSERM, Federation Francaise de Cardiologie, Biotronik, and Medco Research Institute; consulting fees from Biotronik and Medco Health Solutions; and lecture fees from Sanofi-Aventis, Daiichi Sankyo, Eli Lilly, and Bristol-Myers Squibb. Dr. Caron is an employee of Sanofi-Aventis. Dr. Silvain has received research grants (to institution) from Sanofi-Aventis, Daiichi Sankyo, Eli Lilly, INSERM, Fédération Française de Cardiologie, and Société Française de Cardiologie; has served as a consultant to Daiichi Sankyo and Eli Lilly; and has received lecture fees from AstraZeneca, Daiichi Sankyo, and Eli Lilly. Dr. Cayla has received research grants (to institution) from Sanofi-Aventis and Fédération Française de Cardiologie; has served as a consultant to Eli Lilly and Daiichi Sankyo; and has received lecture fees from Eli Lilly, Daiichi Sankyo, Servier, and Abbott. Dr. Beygui has received speaker honoraria from Pfizer, Astellas, Sanofi-Aventis, and Roche. Prof. Montalescot has received research grants from Abbott Vascular, AstraZeneca, Bristol-Myers Squibb, Sanofi-Aventis, Servier, Eli Lilly, Guerbet Medical, Medtronic, Boston Scientific, Cordis, Stago, Centocor, Fondation de France, INSERM, Fédération Française de Cardiologie, Société Française de Cardiologie, ITC Edison, and Pfizer; has received consulting or lecture fees from AstraZeneca, Bayer, Cardiovascular Research Foundation, Cleveland Clinic Research Foundation, Duke Institute, Europa, Lead-up, GlaxoSmithKline, Institut de Cardiologie de Montreal, Nanospheres, Pfizer, and the TIMI Study Group. Sanofi-Aventis, Eli Lilly, Bristol-Myers Squibb, The Medicines Company, Schering-Plough, Portola, Novartis, Menarini, Eisai, Daiichi-Sankyo, Bayer, and Boehringer Ingelheim. All other authors have reported that they have no relationships to disclose. Prof. Collet and Dr. Hulot contributed equally to this work
- Abbreviations and Acronyms
- acute coronary syndrome(s)
- area under the plasma concentration time curve
- Food and Drug Administration
- high on-treatment platelet reactivity
- loading dose
- light transmission aggregometry
- maintenance dose
- myocardial infarction
- maximal platelet aggregation
- percutaneous coronary intervention
- point of care
- platelet reaction unit
- residual platelet aggregation
- relative reduction
- wild type
- Received December 3, 2010.
- Revision received February 8, 2011.
- Accepted March 8, 2011.
- American College of Cardiology Foundation
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