Genetic Determinants of Genetic Determinants of Response to Clopidogrel and Response to Clopidogrel and

Cardiovascular EventsCardiovascular Events

Nicole Cullen Noon Conference February 4, 2009

BackgroundBackground

Pharmacogenetics Pharmacogenetics Tailoring drug therapy to genetic variantsTailoring drug therapy to genetic variants Decreased adverse events and financial Decreased adverse events and financial

waste by not overdosing (coumadin) or waste by not overdosing (coumadin) or underdosing (clopidogrel)underdosing (clopidogrel)

Clopidogrel Clopidogrel Lack of response (“resistance” to therapy) in Lack of response (“resistance” to therapy) in

5-45%5-45%

Study BackgroundStudy Background

Currently, treatment with clopidogrel and aspirin Currently, treatment with clopidogrel and aspirin is the recommended anti-platelet therapy after is the recommended anti-platelet therapy after an MI to prevent further atherothrombotic event. an MI to prevent further atherothrombotic event. Clopidogrel is part of the standard of care for Clopidogrel is part of the standard of care for after stent placement. after stent placement. Duration of 1 year is usual Duration of 1 year is usual

Known variation in clopidogrel’s biologic activity Known variation in clopidogrel’s biologic activity (antiplatelet effect)(antiplatelet effect)Would these polymorphisms have an effect on Would these polymorphisms have an effect on clinical outcomes in patients post-MI?clinical outcomes in patients post-MI?

Study PopulationStudy Population

Subset from the French Registry of Acute ST-Elevation Subset from the French Registry of Acute ST-Elevation and Non-ST Elevation Myocardial Infarction (FAST-MI) and Non-ST Elevation Myocardial Infarction (FAST-MI)

Patients diagnosed with acute MI, admitted to ICUs between Oct Patients diagnosed with acute MI, admitted to ICUs between Oct 1-Dec 24, 2005 and agreed to participate1-Dec 24, 2005 and agreed to participate

Acute MI: defined by serum markers of myocardial necrosis (CK, Acute MI: defined by serum markers of myocardial necrosis (CK, CK-MB, troponin) >2x upper limit of normal, PLUS sx consistent CK-MB, troponin) >2x upper limit of normal, PLUS sx consistent with acute MI or EKG changes in at least two contiguous leads (Q with acute MI or EKG changes in at least two contiguous leads (Q waves, ST changes)waves, ST changes)

Time from onset of sx to admission to ICU <48hrsTime from onset of sx to admission to ICU <48hrs Age >18 yearsAge >18 years Total 3670 patientsTotal 3670 patients

60% of centers in France that treated pts with acute MIs 60% of centers in France that treated pts with acute MIs participated.participated.

Population (con’t)Population (con’t)

Enrollment in the registry did not affect Enrollment in the registry did not affect treatment decisions by physicianstreatment decisions by physicians

Upon enrollment, 2430 (66%) agreed to Upon enrollment, 2430 (66%) agreed to give blood, and an extra 10cc’s were give blood, and an extra 10cc’s were drawn for DNA banking in anticipation of drawn for DNA banking in anticipation of future researchfuture research

For our study, the subset who were placed For our study, the subset who were placed on clopidogrel as part of their treatment on clopidogrel as part of their treatment were considered (n=2208)were considered (n=2208)

MethodsMethods

Polymorphisms already proven to modulate Polymorphisms already proven to modulate clopidogrel’s absorption, metabolic activation or clopidogrel’s absorption, metabolic activation or biologic activitybiologic activity Some had been proven to decrease the platelet-Some had been proven to decrease the platelet-

inhibitory effect of clopidogrel ex vivoinhibitory effect of clopidogrel ex vivo

DNA analyzed for those specific allelic variants DNA analyzed for those specific allelic variants Genotyped for CYP2C19, CYP3A5, ABCB1, P2RY12 Genotyped for CYP2C19, CYP3A5, ABCB1, P2RY12

and ITGB3. and ITGB3.

Studied whether these were associated with Studied whether these were associated with death or ischemic events in a one year follow-up death or ischemic events in a one year follow-up periodperiod

Absorption, mediated by intestinal efflux pump (ABCB1)

Hepatic metabolization of prodrug by P450 (CYP3A5, CYP2C19)

ADP receptor (P2RY12)

GPIIb/IIIa receptor involved in platelet aggregation (ITGB3)

Methods (con’t)Methods (con’t)

Primary outcomePrimary outcome Composite of death from any causes, nonfatal Composite of death from any causes, nonfatal

MI, or stroke during 1-year of follow-upMI, or stroke during 1-year of follow-up

Follow-up results obtained from patients, Follow-up results obtained from patients, family, physicians, registry officesfamily, physicians, registry offices

Follow-up at 1 year for 99.2% of patients Follow-up at 1 year for 99.2% of patients initially enrolledinitially enrolled

Statistical AnalysisStatistical Analysis

ΧΧ22 to test for polymorphism deviation from Hardy- to test for polymorphism deviation from Hardy-Weinberg equilibriumWeinberg equilibrium

Population did not deviate from those previously reported for Population did not deviate from those previously reported for white populationswhite populations

Univariate cox proportional-hazards model to compare Univariate cox proportional-hazards model to compare baseline demographics, clinical characteristics and baseline demographics, clinical characteristics and therapeutic management during hospitalization therapeutic management during hospitalization

Variables considered to have important prognostic value were Variables considered to have important prognostic value were tested in a multivariable, stepwise, forward Cox proportional-tested in a multivariable, stepwise, forward Cox proportional-hazards model for association with the primary outcomehazards model for association with the primary outcome

Results expressed as hazard ratios from these Cox Results expressed as hazard ratios from these Cox models, using 95% CIsmodels, using 95% CIs

Baseline Characteristics/ In-Baseline Characteristics/ In-hospital treatmenthospital treatment

•Event group

•Older, HTN, DM, MI, stroke, PCI, CHF

•Less frequently reperfusion therapy (PCI or fibrinolysis)

•Less likely receive statins, BB, ACEIs, IIb/IIIa inhibitors, heparin while in hospital

Results – Allelic FrequenciesResults – Allelic Frequencies

Rates of CYP3A5, P2RY12, ITGB3, and Rates of CYP3A5, P2RY12, ITGB3, and individual CYP2C19 variants did not differ individual CYP2C19 variants did not differ significantly between groupssignificantly between groups

Frequency of ABCB1 variant allele and Frequency of ABCB1 variant allele and combined CYP2C19 loss of function alleles DID combined CYP2C19 loss of function alleles DID differ significantly between the two groups.differ significantly between the two groups. ABCB1 variants (TT 29 vs. 26%, CT 51 vs. 48%. ABCB1 variants (TT 29 vs. 26%, CT 51 vs. 48%.

p=0.04)p=0.04) CYP2C19 with two variant LOF alleles (4% vs. 2%, CYP2C19 with two variant LOF alleles (4% vs. 2%,

p=0.045)p=0.045)

Results – PredictorsResults – Predictors

Starting at the beginning of the study, the ABCB1 variant and two CYP2C19 LOF variants carried a significant increase in risk for an outcome event during the year (p=0.007 and p=0.003, respectively)

-Remained significant after adjusting for the risk factors and treatments listed in original table

ABCB1: Event rate 15.5% vs 10.7%, adjusted hazard ratio 1.72, 95% CI 1.20-2.47

For CYP2C19: Event rate 21.5% vs 13.3%, adjusted hazard ratio 1.98, 95% CI 1.10-3.58 (After propensity-score matching, risk of outcome was even higher – HR 2.14, 95% CI 1.09-4.17)

Results - InteractionsResults - Interactions

Addition of omeprazole or other PPIs (known to be Addition of omeprazole or other PPIs (known to be CYP2C19 inhibitors) had no significant effect on the CYP2C19 inhibitors) had no significant effect on the clinical response to clopidogrel, as evaluated by CV clinical response to clopidogrel, as evaluated by CV eventseventsCYP2C19*17 (associated with very rapid CYP2C19 CYP2C19*17 (associated with very rapid CYP2C19 activity) also had no effectactivity) also had no effectThe presence of ABCB1 variant along with two The presence of ABCB1 variant along with two CYP2C19 LOF alleles had the highest risk of events CYP2C19 LOF alleles had the highest risk of events (adjusted hazard ratio 5.31, 95% CI 2.13-13.20, (adjusted hazard ratio 5.31, 95% CI 2.13-13.20, p=0.009)p=0.009)In the subset who underwent PCI during hospitalization, In the subset who underwent PCI during hospitalization, the adjusted risk of an outcome was significantly the adjusted risk of an outcome was significantly different only for CYP2C19 two LOF alleles – 3.58x different only for CYP2C19 two LOF alleles – 3.58x those of wild-type. 95% CI 1.71-7.51, p=0.005.those of wild-type. 95% CI 1.71-7.51, p=0.005.

Author ConclusionsAuthor Conclusions

Two of the candidate genes were linked to an Two of the candidate genes were linked to an increased rate of CV eventsincreased rate of CV events ABCB1 (absorption)ABCB1 (absorption) CYP2C19 (metabolism)CYP2C19 (metabolism)

This effect was particularly marked in the This effect was particularly marked in the subgroup of pts who underwent PCI during subgroup of pts who underwent PCI during hospitalization (for two CYP2C19 variant alleles hospitalization (for two CYP2C19 variant alleles only)only)Significantly worse risk profile at admission for Significantly worse risk profile at admission for those who had an event, but no significant those who had an event, but no significant difference in the risk profile or treatment given difference in the risk profile or treatment given between those with and without allelic variantsbetween those with and without allelic variants

Flaws?Flaws?

Relation between ABCB1 gene and actual P-glycoprotein Relation between ABCB1 gene and actual P-glycoprotein expression (the drug-efflux transporter encoded by that gene) still expression (the drug-efflux transporter encoded by that gene) still controversialcontroversialClinical factors such as obesity, insulin resistance, and the nature of Clinical factors such as obesity, insulin resistance, and the nature of the coronary event also contribute to the variability of the clopidogrel the coronary event also contribute to the variability of the clopidogrel response (BMI and DM were considered in baseline characteristics response (BMI and DM were considered in baseline characteristics of this study, but not specifics of MI)of this study, but not specifics of MI)Different doses in the study (could loss of effect in the genetic Different doses in the study (could loss of effect in the genetic variants be overcome by increasing the dose?) variants be overcome by increasing the dose?)

Mean loading dose 300mg PO qday, mean discharge dose 75mg PO Mean loading dose 300mg PO qday, mean discharge dose 75mg PO qdayqday

Observational study – can’t tell cause and effectObservational study – can’t tell cause and effectCould ABCB1 and CYP2C19 polymorphisms affect Could ABCB1 and CYP2C19 polymorphisms affect artherothrombosis directly rather than acting through modulation of artherothrombosis directly rather than acting through modulation of clopidogrel response? No effect seen in subgroup of pts who clopidogrel response? No effect seen in subgroup of pts who contributed blood but did not receive clopidogrelcontributed blood but did not receive clopidogrelCould genetic response to clopidogrel have been different in the Could genetic response to clopidogrel have been different in the absence of these other medications?absence of these other medications?

Where to go from here?Where to go from here?

Is genotyping rather than repeated platelet monitoring (or Is genotyping rather than repeated platelet monitoring (or no platelet monitoring) a realistic, affordable way to no platelet monitoring) a realistic, affordable way to identify patients at high frisk for recurrent identify patients at high frisk for recurrent atherothrombotic events?atherothrombotic events?How many people are we talking?How many people are we talking?

30% of population carriers for a CYP2C19 LOF allele30% of population carriers for a CYP2C19 LOF allele Based on this study, CYP2C19 for two variant alleles, 0.03% Based on this study, CYP2C19 for two variant alleles, 0.03%

Implications for other drugs, such as coumadinImplications for other drugs, such as coumadinPrasugrel (another P2RY12 inhibitor) on the horizon, Prasugrel (another P2RY12 inhibitor) on the horizon, although not yet approved by the FDA. although not yet approved by the FDA.

Skips the need for hepatic metabolismSkips the need for hepatic metabolism

The million dollar question:The million dollar question:

What our clients say...What our clients say...

"I just wanted to call and tell you that my physician switched "I just wanted to call and tell you that my physician switched my medications based on my test results, and I cannot describe my medications based on my test results, and I cannot describe how much better I feel. You have made a believer out of me, my how much better I feel. You have made a believer out of me, my family, and my physician. I hope this testing becomes routine family, and my physician. I hope this testing becomes routine before anyone is placed on long term medication."before anyone is placed on long term medication."- PY, - PY, EirieEirie, CO, CO

CostCost

Costs $260 for a “single pathway” test, looking at Costs $260 for a “single pathway” test, looking at CYP2C19CYP2C19Insurance reimbursement forms provided Insurance reimbursement forms provided Patient and/or doctor have to fight with the insurance Patient and/or doctor have to fight with the insurance

companycompany

Interesting related infoInteresting related info

In another study published in the same issue of NEJM, In another study published in the same issue of NEJM, Mega et al. studied the association between CYP genetic Mega et al. studied the association between CYP genetic variants and CV outcomes in pts presenting with ACS variants and CV outcomes in pts presenting with ACS who were treated with clopidogrel (TRIJTON-TIMI trial)who were treated with clopidogrel (TRIJTON-TIMI trial)

Found that in healthy subjects, carriers of at least one CYP2C19 Found that in healthy subjects, carriers of at least one CYP2C19 LOF allele had decreased levels of the active clopidogrel LOF allele had decreased levels of the active clopidogrel metabolitemetabolite

Less reduction in platelet aggregationLess reduction in platelet aggregation Risk of stent thrombosis 3x higherRisk of stent thrombosis 3x higher Increased risk of death from CV causes, MI or strokeIncreased risk of death from CV causes, MI or stroke

Both this study and Mega showed increased level of CV Both this study and Mega showed increased level of CV events particularly marked in pts undergoing PCIevents particularly marked in pts undergoing PCI

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