Association of CYP2C19 Loss-of-Function Metabolizer Status With Stroke Risk Among Chinese Patients Treated With Ticagrelor-Aspirin vs Clopidogrel-Aspirin

Key Points Question Does CYP2C19 loss-of-function metabolizer status, which blunts metabolism of clopidogrel to its active form, modify the degree of benefit of ticagrelor-aspirin or clopidogrel-aspirin for patients with minor stroke or transient ischemic attack? Findings In this prespecified subgroup analysis of the CHANCE-2 trial, new stroke occurred less often with ticagrelor-aspirin vs clopidogrel-aspirin, irrespective of metabolizer status: 6.0% vs 7.6%, respectively, among patients with intermediate metabolizer status and 5.7% vs 7.5%, respectively, among poor metabolizers. No difference was found in treatment effect between poor and intermediate CYP2C19 metabolizers. Meaning These findings suggest that it may be advisable to consider using ticagrelor-aspirin not only for poor metabolizers but also intermediate metabolizers for patients with transient ischemic attack or minor stroke, although caution should be taken when using ticagrelor added to aspirin due to the risk of any bleeding, particularly mild bleeding.


Introduction
][9][10] As shown in the Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events (CHANCE) trial, the use of clopidogrel plus aspirin reduced the risk of a new stroke compared with aspirin alone only for the subgroup of patients who were not carriers of the CYP2C19 LOF alleles. 8,11e subsequent Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events II (CHANCE-2) trial showed that, among patients with TIA or minor ischemic stroke carrying CYP2C19 LOF alleles who can be treated within 24 hours after the onset of symptoms, the combination of ticagrelor plus aspirin compared with clopidogrel plus aspirin reduced the risk of stroke. 12However, based on the specifics of the CYP2C19 LOF allele, carriers of CYP2C19 LOF alleles can be further divided into 2 groups: intermediate metabolizers (1 LOF carriers) and poor metabolizers (2 LOF carriers). 13Clopidogrel resistance can be overcome by increasing the dose for heterozygous carriers but not for homozygous carriers.The response to clopidogrel may depend on the number of altered alleles of CYP2C19 (gene-dose effect). 14,15Thus, the US Food and Drug Administration-approved drug label (from 2017) gives guidance for CYP2C19 poor metabolizers to use a different platelet P2Y12 inhibitor; however, it does not give dosing guidance for CYP2C19 intermediate metabolizers. 16It is important to understand whether therapy recommendations should differ between intermediate and poor metabolizers with minor stroke and TIA.
The association of the CYP2C19 phenotype, genotype, and LOF alleles with clinical outcomes among patients treated with ticagrelor-aspirin vs clopidogrel-aspirin has not been well defined.This study aimed to describe allele, genotype, and phenotype frequencies for CYP2C19 and evaluate the effect of the CYP2C19 variants on treatment with ticagrelor-aspirin vs clopidogrel-aspirin in terms of prognosis for patients with minor stroke and high-risk TIA.

Trial Design and Oversight
The trial was approved by the ethics committee at Beijing Tiantan Hospital and each participating site (trial protocol and statistical analysis plan in Supplement 1).Written informed consent was provided by all the patients or their representatives before screening.The details of the rationale and design of duration of TIA, and presence or absence of diabetes, with scores ranging from 0 to 7 and higher indicating greater short-term risk]) who were CYP2C19 LOF allele carriers were randomly assigned to receive either ticagrelor (180-mg loading dose on day 1 followed by 90 mg twice daily for days 2-90)

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or clopidogrel (300-mg loading dose on day 1 followed by 75 mg per day for days 2-90) within 24 hours of symptom onset.All patients also received aspirin (75-to 300-mg loading dose followed by 75 mg daily for 21 days).

Efficacy and Safety Outcomes
The primary efficacy and safety outcomes in this analysis were identical to those of the CHANCE-2 trial. 16The primary outcome of the study was any stroke (ischemic or hemorrhagic) within 3 months.
Ischemic stroke was defined as an acute focal infarction of the brain or retina with 1 of the following: sudden onset of a new focal neurologic deficit lasting less than 24 hours with clinical or imaging evidence of infarction, or rapid worsening of an existing focal neurologic deficit lasting 24 hours or more with imaging evidence of new ischemic changes clearly distinct from the index ischemic event.
Hemorrhagic stroke was defined as acute extravasation of blood into the brain parenchyma or subarachnoid space with associated neurologic symptoms.Secondary efficacy outcomes included new stroke within 30 days, composite vascular events (stroke, TIA, myocardial infarction, and vascular death), ischemic stroke, disabling stroke (with a subsequent modified Rankin Scale score of 2 or higher; range, 0-6, with higher scores reflecting worse outcomes) at 90 days.
The primary safety outcome was severe or moderate bleeding events within 3 months, defined by the criteria from the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) trial. 18The secondary safety outcomes were any bleeding, death, adverse events, and severe adverse events through 90 days of follow-up.Severe hemorrhage was defined as fatal or intracranial hemorrhage or other hemorrhage causing hemodynamic compromise requiring blood or fluid replacement, inotropic support, or surgical intervention.
Moderate hemorrhage was defined as bleeding that required transfusion of blood but did not lead to hemodynamic compromise requiring intervention.Any bleeding within 3 months was also reported as a secondary safety outcome in this subgroup study.

Genotyping
The GMEX point-of-

Statistical Analysis
Baseline characteristics are presented by antiplatelet treatment groups (ticagrelor-aspirin or clopidogrel-aspirin) and CYP2C19 phenotype groups (intermediate metabolizers and poor metabolizers).Categorical variables are presented as percentages, and continuous variables as median values with IQRs or mean (SD) values, as appropriate.We performed the analyses according to the intention-to-treat principle for the efficacy and safety outcomes.Interactions between treatment assignment on all outcomes and CYP2C19 phenotype groups were evaluated by including terms for treatment assignment (ticagrelor-aspirin or clopidogrel-aspirin), CYP2C19 phenotype (intermediate metabolizers and poor metabolizers), and treatment × metabolizer status interaction as covariates in Cox proportional hazards regression models or logistic regression models.Interaction terms with a 2-tailed P < .05were considered statistically significant.
Participants were censored at their last follow-up assessment when experiencing a clinical event, at the end of the study, or at the time of withdrawal from the study.When there were multiple events of the same type, the time to the first event was used in the model.The cumulative risks of any ischemic or hemorrhagic event and of bleeding events during the 90-day follow-up were reported as Kaplan-Meier estimates.Cox proportional hazards regression methods were used for calculation of hazard ratios (HRs) and 95% CIs.Differences in time to the first event between study groups within the CYP2C19 phenotypes and genotypes were evaluated using Cox proportional hazards regression models, and HRs were reported with 95% CIs.All statistical analyses were performed with the use of SAS software, version 9.4 (SAS Institute Inc).The study followed the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline.

Allele, Genotype, and Phenotype Frequencies for CYP2C19 and Crude Stroke Risk
Frequency distributions for each allele, genotype, and phenotype for CYP2C19 are shown in Table 2.

Efficacy Outcomes
Table 2 also provides the incidence rates for stroke by CYP2C19 alleles, genotypes, and predicted phenotype.Overall, 341 of 5001 intermediate metabolizers (6.8%) and 93 of 1411 poor metabolizers (6.6%) had a primary efficacy outcome of recurrent stroke at 90 days.As shown in Table 3, 18 the relative risk reduction for the primary end point with ticagrelor-aspirin vs clopidogrel-aspirin was significant among intermediate metabolizers (HR, 0.78 [95% CI, 0.63-0.97])and nonsignificant among poor metabolizers (HR, 0.77 [95% CI, 0.50-1.18];P = .88for treatment × metabolizer status interaction effect).Similar results were observed for the outcomes of composite vascular events, ischemic stroke, and disabling stroke (Table 3). 18Relative risk reductions with ticagrelor-aspirin compared with clopidogrel-aspirin for stroke within 30 days were significant among poor

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Median ABCD 2  b Data are only for the patients who had a TIA.The ABCD 2 score assesses the risk of stroke on the basis of age, blood pressure, clinical features, duration of TIA, and presence or absence of diabetes, with scores ranging from 0 to 7 and higher scores indicating greater short-term risk.
c Medication after onset to before randomization.Various studies have reported that CYP2C19 polymorphisms vary greatly among racial and ethnic groups.In the CHANCE-2 trial, a total of 4572 (41.6%) noncarriers and 6412 (58.4%) carriers of CYP2C19 LOF alleles were identified. 12Compared with White populations, our Chinese population has a high frequency of CYP2C19 LOF alleles, mostly attributable to CYP2C19*2, which was present in 87.7% of patients with CYP2C19 LOF alleles. 20,21[24][25][26] Given this high prevalence of CYP2C19 LOF allele carriers among East Asian populations, there is a need to determine the influence of metabolizer phenotype on antiplatelet therapy allocations and clinical outcomes.The results provide evidence supporting genetic testing that may allow clinicians to personalize antiplatelet therapy, especially for East Asian patient populations, for whom the prevalence of CYP2C19 LOF alleles is high.

Safety Outcomes
It is well established that patients carrying LOF CYP2C19 alleles have a reduced capacity to metabolize clopidogrel to its active form and that polymorphisms of the CYP2C19 genotype partially explain the variability in response to clopidogrel.Several studies have shown that the effectiveness of clopidogrel for secondary stroke prevention is reduced among CYP2C19 LOF carriers. 8,9,27-29A previously published meta-analysis also found that the carriers of 1 or 2 CYP2C19 LOF alleles display a significantly increased risk of stroke and composite vascular events compared with noncarriers among patients with ischemic stroke or TIA treated with clopidogrel. 10Ticagrelor is one of the alternative agents for this population. 30wever, the magnitude of any additional benefit of ticagrelor over clopidogrel between carriers of 2 and 1 CYP2C19 LOF alleles is unclear.The present study found ticagrelor-aspirin to be superior to clopidogrel-aspirin among patients with ischemic stroke regardless of whether they had 1 (intermediate  30 in which ticagrelor was associated with a greater risk of severe hemorrhage.In the current analysis, no increase in the incidence of severe or moderate bleeding was reported in the ticagrelor-aspirin group among patients carrying either 1 or 2 CYP2C19 LOF alleles.This difference may be partly due to the use of single antiplatelet therapy in the control group in the THALES study.The incidence of severe or moderate bleeding therefore cannot be underestimated for patients treated with ticagrelor-aspirin.

Limitations
Our study has several limitations.First, noncarriers of CYP2C19 LOF alleles were not included in the CHANCE-2 trial, and the relative effectiveness of ticagrelor among this population remains unknown.
The differences between ticagrelor-aspirin and clopidogrel-aspirin in CYP2C19 normal metabolizers should be explored in future studies.Second, this study was a subgroup analysis, which may increase the possibility of type I error, and had much less statistical power to identify subgroup effects, so our results require confirmation by other studies.Third, this study evaluated only the effect of different CYP2C19 genotypes on the clinical efficacy of ticagrelor-aspirin compared with clopidogrel-aspirin among patients receiving the drugs after stroke or TIA.The CYP2C19 genotype contributed importantly to the heterogeneity of clopidogrel response; however, there was still a gap between the CYP2C19 genotype and clopidogrel's response.Associations with clopidogrel response and clinical outcomes were not clarified by this study.Fourth, all patients in the CHANCE-2 trial were Chinese, which may limit the generalizability of the findings to other populations.

Conclusions
In this prespecified secondary analysis of the CHANCE-2 randomized clinical trial, we found no treatment-by-metabolizer status interaction.The relative clinical efficacy and safety of ticagreloraspirin vs clopidogrel-aspirin were similar across CYP2C19 phenotypes that defined intermediate and poor metabolizers.The absolute reduction in new stroke events, the composite end point of clinical vascular events, and individual ischemic stroke events within 3 months were similar in each genotyping group.

Table 1 .
P = .32for treatment × metabolizer status interaction effect).The cumulative risk of new stroke among patients with different metabolizer status by treatment assignment are shown in the Figure.The efficacy outcomes of ticagrelor-aspirin compared with clopidogrel-aspirin among patients with different CYP2C19 genotypes are shown in eTable 2 and eFigure 2 in Supplement 2. The efficacy of outcomes of metabolizer status among patients with different treatments are shown in eTable 3 in Supplement 2. Baseline Characteristics of the Patients with Different CYP2C19 Phenotypes Ticagrelor Therapy and Loss-of-Function CYP2C19 Genotype JAMA Network Open.2023;6(6):e2317037.doi:10.1001/jamanetworkopen.2023.17037(Reprinted) June 6, 2023 4/12 Downloaded From: https://jamanetwork.com/ on 09/23/2023

Table 2 .
Distribution and Event Rates of New Stroke by Genotypes or Metabolizer Phenotype among poor metabolizers (a nonsignificant 23% relative risk reduction).We found no difference in treatment effect between poor and intermediate CYP2C19 metabolizers.Compared with clopidogrelaspirin, ticagrelor-aspirin demonstrated superior potency for prevention of stroke events among both intermediate metabolizers and poor metabolizers.Furthermore, the benefits of treatment with ticagrelor over clopidogrel were achieved without resulting in a significant increase in the incidence of severe or moderate bleeding among intermediate or poor metabolizers.Our study demonstrates a Patients with at least two *2 or *3 alleles (*2/*2, *2/*3, or *3/*3) according to point-of-care genotyping were classified as poor metabolizers and those with one *2 or *3 allele (*1/*2 or *1/*3) were classified as intermediate metabolizers.JAMA Network Open | NeurologyTicagrelor Therapy and Loss-of-Function CYP2C19 Genotype JAMA Network Open.2023;6(6):e2317037.doi:10.1001/jamanetworkopen.2023.17037(Reprinted) June 6, 2023 6/12 Downloaded From: https://jamanetwork.com/ on 09/23/2023 that relative risk reductions for the primary end point and key secondary cardiovascular outcomes were similar regardless of CYP2C19 phenotype.

Table 3 .
31sociation of Ticagrelor-Aspirin vs Clopidogrel-Aspirin With Clinical Outcomes Stratified by CYP2C19 Metabolizer Status Severe or moderate bleeding and mild bleeding were defined in accordance with the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries 18 criteria.metabolizers)ormorethan1(poormetabolizers)nonfunctionalcopyof CYP2C19.Intermediate metabolizers showed no differences in safety or efficacy from poor metabolizers; the 2 groups could be categorized as a single entity for use of ticagrelor-aspirin for secondary prevention.Intermediate metabolizers are able to process some clopidogrel, so they receive partial benefit from the treatment, while poor metabolizers process little or no clopidogrel, so they receive very limited benefit from it.However, in the CHANCE trial, the rate of stroke was 9.4% (17 of 181) for poor metabolizers and 9.5% (63 of 664) for intermediate metabolizers treated with clopidogrel.8InPOINT(Platelet-OrientedInhibition in New TIA and Minor Ischemic Stroke Trial), the rate of stroke was 0% (0 of 11) for poor metabolizers and 3.3% (3 of 92) for intermediate metabolizers treated with clopidogrel.26Therewasnolargegap in stroke risk between poor metabolizers and intermediate metabolizers with minor stroke and TIA treated with clopidogrel, although events were rare in POINT due to limited genotyping and a lower prevalence of LOF alleles.Thus, similar benefits may occur with ticagrelor for both populations.The 2022 update of the Clinical Pharmacogenetics Implementation Consortium has already increased the strength of recommendation to avoid standard-dose (75 mg) clopidogrel if possible and use prasugrel or ticagrelor at the standard dose if there is no contraindication (from moderate to strong) for CYP2C19 intermediate metabolizers when considering clopidogrel for cardiovascular indications.31Forneurovascularindications, the recommendation (with moderate strength) is to consider an alternative P2Y12 inhibitor at the standard dose if clinically indicated and there is no contraindication.As shown in our study, intermediate metabolizers with minor stroke or TIA had a similar efficacy with ticagrelor compared with clopidogrel, which might partly support the use of an alternative P2Y12 inhibitor not only for poor metabolizers but also for intermediate metabolizers when considering clopidogrel for neurovascular indications.The data from our study indicated that, for patients with minor stroke or TIA, ticagrelor is an alternative to clopidogrel for poor metabolizers as well as for intermediate metabolizers.The absolute risk of severe or moderate bleeding was low in both treatment groups, and the risk among those treated with ticagrelor-aspirin was not significantly greater than that among those treated with clopidogrel-aspirin regardless of phenotypes for CYP2C19 polymorphism.This finding differs with the observations in The Acute Stroke or Transient Ischemic Attack Treated With Ticagrelor and Aspirin for Prevention of Stroke and Death (THALES) trial, a Composite vascular events comprise ischemic stroke, hemorrhagic stroke, transient ischemic attack, myocardial infarction, and vascular death.bA stroke was defined as disabling if the patient had a subsequent modified Rankin scale score greater than 1 (indicating death or any degree of disability).c JAMA Network Open.2023;6(6):e2317037.doi:10.1001/jamanetworkopen.2023.17037(Reprinted) June 6, 2023 8/12 Downloaded From: https://jamanetwork.com/ on 09/23/2023 Ticagrelor Therapy and Loss-of-Function CYP2C19 Genotype JAMA Network Open.2023;6(6):e2317037.doi:10.1001/jamanetworkopen.2023.17037(Reprinted) June 6, 2023 9/12 Downloaded From: https://jamanetwork.com/ on 09/23/2023