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Cytochrome P450 2C19 polymorphism is associated with poor
clinical outcomes in coronary artery disease patients
treated with clopidogrel
Bo Jin •Huan-Chun Ni •Wei Shen •
Jian Li •Hai-Ming Shi •Yong Li
Received: 19 February 2010 / Accepted: 2 September 2010 / Published online: 16 September 2010
ÓSpringer Science+Business Media B.V. 2010
Abstract Patients with lesser degrees of platelet inhibi-
tion in response to clopidogrel appear to be at increased
risk for recurrent ischemic events. Cytochrome P450
(CYP) polymorphisms have been proposed as possible
mechanisms for nonresponsiveness to clopidogrel. Published
data on the association between CYP2C19*2 polymor-
phism and atherothrombotic events are inconclusive. To
derive a more precise estimation of the relationship, a
meta-analysis was performed. A total of eight prospective
cohort studies including 2,345 patients carrying CYP2C19*2
variant allele and 5,935 cases with the wild-type genotype
were included in this meta-analysis. Overall, borderline
statistically significantly elevated risk of adverse clinical
events was associated with genotyping 681G[A poly-
morphism (for AA ?GA vs. GG: OR, 1.46; 95% CI, 1.01
to 2.13; P=0.05). The summary odds ratio showed a
significant association between the CYP2C19*2 polymor-
phism and an increased risk of cardiac mortality in the
follow-up period (OR, 2.07; 95% CI, 1.22 to 3.52; P=
0.007). When studies evaluating myocadial infarction, stent
thrombosis, and ischemic stroke, the presence of the vari-
ant allele was associated with significantly increased risks
of recurrent atherothrombotic events. In summary, this
meta-analysis indicated that CYP2C19*2 carrier status is
significantly associated with an increased risk of adverse
cardiovascular events.
Keywords CYP2C19 Meta-analysis Coronary artery
diseases Clopidogrel
Introduction
Coronary artery disease (CAD), although closely related to
life style and environmental factors, is also influenced by
the complex patterns of inheritance [1–3]. The association
between conventional factors and CAD has been thor-
oughly investigated, but the role of genetic markers is still
poorly understood. Genetic polymorphisms could have a
pivotal role in determining individual susceptibility to drug
response in patients with CAD.
Treatment with clopidogrel reduces cardiovascular
death and ischemic complications in patients with CAD
and those undergoing percutaneous coronary intervention
(PCI) and has been widely adopted in clinical practice [4].
The pharmacodynamic response to clopidogrel shows a
wide interindividual variation [5], and patients with lesser
degrees of platelet inhibition in response to clopidogrel
appear to be at increased risk for recurrent ischemic events
[6,7]. New markers for identifying high-risk populations as
well as novel strategies for early detection and preventive
care are urgently needed.
Clopidogrel is a prodrug that requires biotransformation
to an active metabolite by cytochrome P450 (CYP) enzymes
[8]. The genes encoding the CYP enzymes are polymor-
phic, and extensive data have shown that certain alleles
confer reduced enzymatic function [9]. A functional single
nucleotide polymorphism CYP2C19 681G[A (rs4244285)
has been reported by several studies to have a higher rate of
subsequent cardiovascular events than those who were not.
This adverse effect was particularly marked among the
patients undergoing PCI [10]. However, the results are
Bo Jin and Huan-Chun Ni contributed equally to this study and should
be considered as co-first authors.
B. Jin H.-C. Ni W. Shen J. Li H.-M. Shi Y. Li (&)
Department of Cardiology, Huashan Hospital, Fudan University,
12 Middle Urumqi Road, 200040 Shanghai, China
e-mail: liyonghs@yahoo.com.cn
123
Mol Biol Rep (2011) 38:1697–1702
DOI 10.1007/s11033-010-0282-0
inconclusive, partially because of the possible small effect
of the polymorphism on cardiovascular risk and the rela-
tively small sample size in each of published studies.
Therefore, we performed a meta-analysis of the eligible
studies to derive a more precise estimation of this associ-
ation.
Materials and methods
Study search strategy
Prospective cohort studies were identified from PubMed
and Embase database in December 2009 using both elec-
tronic and manual search strategies. We combined search
terms for CYP450 2C19, polymorphism, and clopidogrel,
and we limited the search to English-language studies in
patients with CAD. When more than one of the same
patient population was included in several publications,
only the most recent or complete study was identified in
this meta-analysis.
Inclusion criteria
We identified eligible articles on the basis of 4 inclusion
criteria: (1) prospective cohort study, (2) patients with
coronary artery disease undergoing PCI, (3) patients
receiving clopidogrel, and (4) evaluation of CYP450 2C19
polymorphism and clinical outcomes in target population.
Data extraction
Two reviewers (Jin and Ni) independently extracted data
from all selected studies fulfilling inclusion criteria.
Disagreement was resolved by discussion between the two
reviewers. Data extraction included the first author’s sur-
name, publication date, region origin, demographic data,
target population, treatment protocol, study period, and
genotyping method, respectively. For data not provided in
tabular form or the main text, the required information
were obtained from online data appendix supplementary.
Statistical analysis
Cochrane Collaboration meta-analysis review methodology
was used for this study. Crude odds ratio (OR) with 95%
confidence interval (CI) was used to assess the strength of
association between CYP450 2C19 polymorphism and
adverse clinical outcomes in CAD patients treated with
clopidogrel. The presence of heterogeneity across trials
was evaluated, Pvalue B0.10 was considered to be sig-
nificant for statistical heterogeneity. The pooled ORs were
performed for dominant model (AA ?GA vs. GG). All
statistical tests were performed with RevMan version 4.2.2
available free from cochrane collaboration (http://www.
cochrane.org/cochrane/hbook/htm).
Results
Study characteristics
A total of eight prospective cohort studies met the inclusion
criteria [11–18]. Totally, 2,345 patients carrying
CYP2C19*2 variant allele and 5,935 cases with the wild-
type genotype were included in this meta-analysis. Table 1
lists the studies identified and their main characteristics. Of
the eight studies, sample sizes ranged from 105 to 2,485.
Furthermore, the study period ranged from 30 days to
15 months. The two study groups according to CYP2C19
genotype were well balanced with respect to baseline
features.
Adverse clinical events
Table 2presents the pooled ORs according to CYP2C19*2
variant on clinical outcomes in this meta-analysis. Overall,
borderline significantly elevated risk of adverse clinical
events was associated with genotyping 681G[A poly-
morphism (for AA ?GA vs. GG: OR, 1.46; 95% CI, 1.01
to 2.13; P=0.05; Fig. 1) when all eligible studies were
pooled into the meta-analysis. The overall heterogeneity
test indicated statistically significant results (I-squared =
70.4%; P=0.001).
Cardiac mortality
Cardiac mortality in the five cohort studies included in the
primary analysis was 1.10% (56 of the 5,080 patients).
Mortality in CYP2C19*2 carriers was 1.77% (25 of the
1,416 patients) and in the noncarriers was 0.85% (31 of
the 3,664 patients). The summary odds ratio showed a
significant association between CYP2C19*2 polymor-
phism and an increased risk of cardiac mortality in the
follow-up period (OR, 2.07; 95% CI, 1.22–3.52; P=
0.007; Fig. 2).
Myocadial infarction
Five studies provided data on no fatal myocardial infarc-
tion, the heterogeneity (I-squared =52.8%; P=0.08) was
detected among studies and data were assessed by the
random effect model. The rate of myocardial infarction in
CYP2C19*2 carriers was 7.91% (112 of the 1,416 patients)
and in the noncarriers was 5.76% (211 of the 3,664
1698 Mol Biol Rep (2011) 38:1697–1702
123
patients). The overall meta-analysis demonstrated that
significantly elevated risk was associated with CYP2C19*2
genotype (for AA ?GA vs. GG: OR, 1.69; 95% CI, 1.09
to 2.61; P=0.02).
Stent thrombosis
In the five cohort studies reporting stent thrombosis data,
3,614 (72.1%) were CYP2C19 wild-type homozygotes
Table 1 Main characteristics of all studies included in the meta-analysis
Study Region CYP2C19
AA/GA/GG
Study population Treatment protocol Study
period
Genotyping
method
Malek et al. [11] Poland 1/20/84 ACS undergoing PCI LD 300 mg or 600 mg;
MD 75 mg clopitogrel
12 months PCR
Trenk et al. [12] Germany 17/228/552 Elective PCI LD 600 mg; MD 75 mg
clopitogrel
12 months TaqMan PCR
Collet et al. [13] France 9/64/186 Myocardial infarction clopitogrel 75 mg per day 6 months TaqMan PCR
Giusti et al. [14] Italy 26/221/525 CAD undergoing PCI LD 600 mg; MD 75 mg
clopitogrel
6 months PCR
Mega et al. [15] America Europe 38/357/
1,064
ACS undergoing PCI LD 300 mg; MD 75 mg
clopitogrel
15 months PCR
Sibbing et al. [16] Germany 47/633/
1,805
CAD undergoing PCI LD 600 mg; MD 75 mg
clopitogrel
30 days TaqMan PCR
Simon et al. [17] French 53/564/
1,561
Myocardial infarction LD 300 mg; MD 75 mg
clopitogrel
12 months SNPlex
Shuldiner et al. [18] USA 4/63/160 Elective PCI LD 300 mg or 600 mg;
MD 75 mg clopitogrel
12 monthss SNPlex
ACS acute coronary syndrome, CAD coronary artery disease, PCI percutaneous coronary intervention, LD loading dose, MD maintenance dose
Table 2 Summary of pooled ORs according to CYP2C19*2 gene variant on clinical outcomes
Comparison Study CYP2C19*2
genotype (Carriers/
Noncarriers)
Pvalue
for hetero-
geneity
Model OR (95% CI) Pvalue for
overall effect
Clinical events 8 2,345/5,935 0.001 R 1.46 [1.01, 2.13] 0.05
Cardiac mortality 5 1,416/3,664 0.14 F 2.07 [1.22, 3.52] 0.007
Myocadial infarction 5 1,416/3,664 0.08 R 1.69 [1.09, 2.61] 0.02
Stent thrombosis 5 1,396/3,614 0.86 F 3.81 [2.27, 6.40] \0.00001
Ischemic stroke 2 1,075/2,869 0.18 F 5.78 [1.62, 20.65] 0.007
Rrandom effect model, Ffixed effect model
Fig. 1 Forest plot of OR according to CYP2C19*2 gene variant on adverse clinical events in the management of clopidogrel from eight trials
(OR, 1.46; 95% CI, 1.01–2.13; P=0.05)
Mol Biol Rep (2011) 38:1697–1702 1699
123
(GG) and 1,396 (27.9%) carried at least one *2 allele
(AA or GA). The cumulative incidence of stent thrombosis
was significantly higher in CYP2C19*2 carriers than in
wild-type subjects (OR, 3.81; 95% CI, 2.27–6.40; P\
0.00001; Fig. 3). Statistical tests indicated no heterogeneity
(I-squared =0%; P=0.86) and data were assessed by the
fixed effect model.
Ischemic stroke
Overall ischemic stroke rate in the two cohort studies was
0.25% (10 of the 3,944). As described in Table 2, the meta-
analysis demonstrated that CYP2C19*2 carriers had a
higher rate of ischemic stroke in CAD patients treated with
clopidogrel (OR, 5.78; 95% CI, 1.62–20.65; P=0.007).
Discussion
Platelet activation plays a pivotal role in the development
of arterial thrombosis and subsequent cardiovascular events
[19]. Treatment with the thienopyridine clopidogrel is
frequently used in CAD patients to reduce ischemic
complications [20]. However, there has been a growing
appreciation of the variability in the pharmacological as
well as the clinical response to clopidogrel. The mecha-
nisms leading to a poor response to clopidogrel have not
yet been fully elucidated and are most likely multifactorial,
with genetic polymorphisms in CYP genes explaining
some of this variation [21]. Therefore, genetic suscepti-
bility to cardiovascular events has been a research focus in
scientific community.
Clopidogrel, as a prodrug, is known to require metabo-
lism before it can inhibit adenosine-diphosphate-induced
platelet aggregation. Growing evidence reveals that the loss
of function polymorphisms of CYP2C19 is associated with
decreased exposure to the active metabolite of clopidogrel
[22]. The present meta-analysis performed on over 8000
patients with CAD under clopidogrel treatment shows that
patients carrying at least one CYP2C19*2 allele have a
borderline significantly higher risk of adverse clinical
events compared with the noncarriers. Furthermore, high
on-clopidogrel platelet reactivity increases the risk of car-
diac death and myocardial infarction following percuta-
neous coronary intervention, which is mainly associated
with single nucleotide polymorphism 681G [A. In patients
Fig. 3 Cumulative OR estimate of stent thrombosis in CYP2C19*2 carriers when compared with noncarriers (OR, 3.81; 95% CI, 2.27–6.40;
P\0.00001)
Fig. 2 The overall cardiac mortality analysis demonstrated that significantly increased risk was associated with CYP2C19*2 polymorphism
(OR, 2.07; 95% CI, 1.22–3.52; P=0.007)
1700 Mol Biol Rep (2011) 38:1697–1702
123
who received coronary stenting, we also noted a marked
higher rate of stent thrombosis in patients carrying at least
one CYP2C19*2 allele.
Moreover, our data show that in patients with CAD
treated with clopidogrel, the genetic variants in CYP2C19
were associated with ischemic stroke that was fivefold
greater than the rate in patients with wild-type homozy-
gotes. The difference may in part be explained by the
genetic variants altered the pharmacokinetics and sub-
stantially attenuated the antiplatelet effect of clopidogrel
[23].
The present study derives a more precise estimation of
the association between CYP2C19*2 polymorphism and
poor clinical outcomes. It is logical to consider whether
CYP2C19*2 carriers as high-risk population can be identi-
fied prior to an intensified antiplatelet treatment in patients
scheduled for coronary stent placement. High clopidogrel
maintenance dosing or the use of novel and more potent
P2Y12 receptor antagonists may be potential treatment
options for tailored antiplatelet therapy in CYP2C19*2 car-
riers [24].
The pooled results that we report should be interpreted
with some caution. The primary endpoints and writing
styles varied across eight original articles, so prespecified
data were partly extracted from cohort studies for statistical
analysis. Heterogeneity is a potential problem when inter-
preting the results of all meta-analyses. The publication
bias, favouring the publication of positive studies, also
cannot be excluded.
In conclusion, this meta-analysis indicated that CYP2
C19*2 carrier status is significantly associated with an
increased risk of adverse cardiovascular events. However,
larger sample studies including different ethnic groups with
careful matching between carriers and noncarriers should
be considered in further association studies to confirm the
results from our meta-analysis.
Acknowledgments We gratefully acknowledge Dr. Ying Shan for
her editorial suggestions for the article. This study was supported in
part by the 11th Five-year National Science Project on Chronic Heart
Failure in China (2006BAI01A04).
Conflict of interest The authors have no conflicts of interest to
disclose.
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