1. DEBATE Should We Tailor Antiplatelet Therapy Based on Platelet Function Testing and Genotyping? No! (At least, not yet)
Peter Berger, MD
Director, Center for Clinical Studies
Interventional Cardiologist
Geisinger Clinic
CRT 2/09

2. Peter B. Berger, MD DISCLOSURES Consulting Fees
Accumetrics, Daiichi Sankyo, Inc. and Eli Lilly and Company, Boehringer Ingelheim, Novartis, Portola Pharmaceuticals, Inc., AstraZeneca, Guerbet
Grants/Contracted Research
ThromboVision, Inc., Helena, AstraZeneca, Haemoscope, The Medicines Company, Corgenix, Daiichi Sankyo, Inc. and Eli Lilly and Company
Ownership Interest (Stocks, Stock Options or Other Ownership Interest)
Lumen Biomedical, Inc.

3. Platelet Function Testing
Definition of clopidogrel “resistance” or hyporesponsiveness
Which device? Results differ between devices
What cut point? Not known for many devices; often identified retrospectively
Able to detect response to therapy? Many are not
Drug-drug interactions Uniformly misleading
What to do, how to treat? Being studied; not yet known

4. Responsive to Clopidogrel
Two studies indicated that the greatest determinant of post-treatment reactivity is pre-treatment reactivity (Michelson et al, Gurbel et al)
Other studies have shown that an important determinant of pre-treatment reactivity is atherosclerotic burden
Do we need to perform post-treatment platelet function testing?
Should we just treat pts at higher baseline risk more aggressively? CP

5. Breet NJ et al JAMA 2010. In press
The POPular Study
Enrolled 1069 consecutive pts on clopidogrel undergoing elective PCI
On-treatment platelet reactivity measured by
light transmittance aggregometry (LTA),
the VerifyNow P2Y12 assay
Plateletworks assay
IMPACT-R (with and without pre-stimulation with adenosine diphosphate [ADP])
PFA-100 System (with the Dade PFA Collagen/ADP Test Cartridge and the novel INNOVANCE PFA P2Y)
Cut-off values for HPR were established by receiver- operator characteristic curve analysis
Breet NJ et al JAMA In press

6. The POPular Study
At one-year, the 1o endpoint of all-cause death, non-fatal MI, stent thrombosis and ischemic stroke occurred more frequently in pts with HPR as assessed by
LTA (11.7% vs 6.0%, p=0.0009) with 5 μmol/L ADP LTA
LTA (12.0% vs 6.2%, p=0.001) using 20 μmol/L ADP
VerifyNow P2Y12 assay (13.3% vs 5.7%, p<0.0001)
Plateletworks assay (12.6% vs 6.1%, p=0.005)
The IMPACT-R and Dade PFA Collagen/ADP Test Cartridge were unable to discriminate between pts with and without events at 1 year
Breet NJ et al JAMA In press

7. Would never perform as well if used prospectively in the next data set
The POPular Study
The cut-off values used in this study for high on- treatment platelet reactivity were established by analyzing receiver operating characteristic curves
Would never perform as well if used prospectively in the next data set
Breet NJ et al JAMA In press

8. Odds Ratios for the 1o Endpoint at One Year LTA 5 µmolar ADP18 8 4 2 1 .5
.25
P for model <0.001
Quintile of reactivity
Breet NJ et al JAMA In press

9. K-M Curves for 1o Endpoint at One Year
LTA 5 µmolar ADP
Event
Rate, % 15
High 10 5
Low
Log Rank <0.001
Breet NJ et al JAMA In press

10. The predictive accuracy of even these tests was only modest
The POPular Study
The predictive accuracy of even these tests was only modest
None of the tests correlated with TIMI major or minor bleeding
Breet NJ et al JAMA In press

11. The Problem of Those Drug-Drug Interaction Studies
Nearly all or all studies have indicated a reduction in aggregability when clopidogrel is administered with certain statins (ie, atorvastatin), calcium channel blockers, and proton pump inhibitors
Proper subgroup analyses from randomized trials (CREDO, CHARISMA, TRITON, etc.) indicate that there is not a clinically significant reduction in clinical efficacy (or increase in bleeding) among patients on clopidogrel taking these other drugs CP

12. COGENT Aspirin Non-STEMI, STEMI, or Elective Stent n=3627
Clopidogrel 75 mg
and Placebo
Clopidogrel 75 mg
and
Omeprazole (Prilosec) 20 mg
Planned enrollment: 5000; stopped due to bankruptcy
Mean follow-up 133 days (maximum, 362 days)

13. Composite Cardiovascular Events
COGENT Trial
1.00
N=3627
Placebo: 67 events; 1821 at risk Treated: 69 events; 1806 at risk
0.98
HR= % CI=0.70;1.51
0.96
Survival Probability
0.94
Placebo
0.92
Omeprazole (Prilosec)
0.90 30 60 90
120
150
180
210
240
270
300
330
360
390
Time (Days)
Adjusted with Cox Proportional Hazards Model for
NSAID use and positive H. pylori status.
Bhatt D, et al. TCT; 9/09; SF, CA

14. COGENT No. of Events Clopidogrel with: Placebo Omeprazole N=3627
Mean follow-up 133 days (maximum, 362 days)
Omeprazole
N=3627
No. of
Events
136 adjudicated CV events; 105 adjudicated GI events. 14 events not yet been adjudicated.
Bhatt D et al TCT 9/09

15. Platelet function testing GenotypingCP

16. Genetic vs. Platelet Function Testing
Complex interplay between genes, baseline characteristics, and the clinical presentation
Some patients (~50%?) with a loss of function allele have a “normal” response: what is their risk?
Some patients with wild type alleles are hyporesponders; what is their risk? CP

17. Clopidogrel ~2% of ingested clopidogrel ultimately bound to platelets
Small changes in metabolism could potentially have enormous effects
25 polymorphic variants of the CYP2C19 gene have been identified so far
One of the most common (allelic frequency of 15% - 30%) is designated CYP2C19*2 CP

18. Clopidogrel
The totality of CYP2C19 polymorphism data suggest that it may identify those at increased risk for thrombosis or bleeding with clopidogrel
Does knowing the genetic makeup of 1 CYP enzyme provide enough information to identify pts outside the therapeutic window of clopidogrel and justify altering therapy?
Shuldiner AR et al JAMA 2009;302:849-57 CP

19. Clopidogrel
In 1 analysis, the CYP2C19*2 genotype explained only 12% of the variation in response to clopidogrel
a uniquely homogeneous and healthy white population taking no other medications
What about other potential environmental and genetic factors affecting the numerous steps involved in the generation of the active metabolite of clopidogrel
Are there other potentially important factors?
Shuldiner AR et al JAMA 2009;302:849-57 CP

20. Absorption (>50% of administered dose)
Genetic and Environmental Factors That Influence the Generation of the Active Metabolite of Clopidogrel
Absorption (>50% of administered dose)
Metabolism (Since primarily hepatic, all processes below are influenced by liver disease; also by inflammatory states)
Hydrolysis (converts ~85% of absorbed prodrug to carboxylate, an inactive metabolite)
1st oxidative step (converts clopidogrel to 2-oxo- clopidogrel)
2nd oxidative step (conversion of 2-oxo-clopidogrel to the active metabolite) CP

21. Genetic and Environmental Factors That Influence the Generation of the Active Metabolite of Clopidogrel
Absorption (>50% of administered dose) Patient compliance Proximity to and type of meal Previous gastric surgery Transmembrane transporter MDR1/P-glycoprotein (also called ABCB1) Genetic polymorphisms: >40 identified SNPs Drug inducers (eg, colchicine, insulin, methotrexate) Environmental and drug inhibitors (eg, orange and grapefruit juices, green tea, garlic, quinidine, nicardipine, amiodarone) Crushed vs whole tablet
Steinhubl SR Circulation SNP data from % conversion data from Kazui et al Drug Metab Dispos. 2010;38:92-9

22. Genetic and Environmental Factors That Influence the Generation of the
Active Metabolite of Clopidogrel
Metabolism (Since primarily hepatic, all processes below are influenced by liver disease; also by inflammatory states) Hydrolysis (converts ~85% of absorbed prodrug to carboxylate, an inactive metabolite) HCE Genetic polymorphisms: 16 indentified SNPs Drug inhibitors (eg, procainamide) Alcohol ingestion 1st oxidative step (converts clopidogrel to 2-oxo-clopidogrel) CYP1A2 (responsible for ~36% of conversion) Genetic polymorphisms: 16 identified SNPs Environmental and drug inducers (eg, tobacco, char-grilled meat, insulin, omeprazole, St John’s wort) Environmental and drug inhibitors (eg, caffeine, grapefruit juice, verapamil, fluoroquinolones)
Steinhubl SR Circulation SNP data from % conversion data from Kazui et al Drug Metab Dispos. 2010;38:92-9

23. Genetic and Environmental Factors That Influence the Generation of the
Active Metabolite of Clopidogrel
Metabolism, continued 1st oxidative step (continued) CYP2B6 Genetic polymorphisms: 29 identified SNPs Drug inducers (eg, carbamazepine, glucocorticoids, rifampin) Drug inhibitors (eg, SSRIs, estradiol) CYP2C19 (responsible for 45% of conversion) Genetic polymorphisms: 25 identified SNPs Drug inducers, eg, prednisone, rifampin, St John’s wort Drug inhibitors, eg, proton pump inhibitors, SSRIs, cimetidine, indomethacin
Steinhubl SR Circulation SNP data from % conversion data from Kazui et al Drug Metab Dispos. 2010;38:92-9

24. Genetic and Environmental Factors That Influence the Generation of the
Active Metabolite of Clopidogrel
2nd oxidative step (conversion of 2-oxo-clopidogrel to the active metabolite) CYP2B6 (responsible for ~33% of conversion) Genetic and drug influences: see above CYP2C9 (responsible for ~7% of conversion) Genetic polymorphisms: 34 identified SNPs Drug inducers (eg, carbamazepine, rifampin, St John’s wort) Drug inhibitors (eg, fluconazole, valproic acid, amiodarone) CYP2C19 (responsible for ~20% of conversion) Genetic and drug influences: see above CYP3A4 (responsible for ~40% of conversion) Genetic polymorphisms: 20 identified SNPs Drug inducers (eg, aspirin, barbiturates, rifampin, St John’s wort) Environmental and drug inhibitors (eg, verapamil, lipophilic statins, macrolide antibiotics, fluconazole, protease inhibitors, grapefruit juice..)
Steinhubl SR Circulation SNP data from % conversion data from Kazui et al Drug Metab Dispos. 2010;38:92-9

25. Clopidogrel “Resistance” Over Time
Non-responders (%)
Gurbel P, Circulation 2003;107:2908

26. Genetic vs. Platelet Function Testing
What about the practical consideration that it takes days to get the results of genotyping?
Should we then switch therapy? CP

27. G R A V T A S
Successful PCI with DES without major complication or GPIIb/IIIa use
VerifyNow P2Y12 Assay hours post-PCI
PRU ≥ 230?
Yes No
Responder
Non-Responder
Random Selection R
ACS A B C
N = 1100
N = 1100
N = 583
“Tailored Therapy”
clopidogrel 600-mg*, then
clopidogrel 150-mg/day
“Standard Therapy”
placebo loading dose, then clopidogrel 75mg +placebo/day
“Standard Therapy”
placebo loading dose clopidogrel 75mg +placebo/day
Clinical Follow-up And Platelet Function Assessment at 30 days, 6M
Primary Endpoint: 6 month CV Death, Non-Fatal MI, ARC definite/prob ST
Safety Endpoint: GUSTO Moderate or Severe Bleeding
Price MJ et al, Am Heart J 2009

28. CYP2C19 CYP3A5 CYP2B6 CYP3A4 ABCB1 P2RY12 IRS-1 PAR-1
Exploring the Synergy Between Genetic and Platelet Function Testing
PLATELET FUNCTION: VerifyNow P2Y12 at GRAVITAS index procedure (post standard-dose clopidogrel) and after 30 days, 6 months of study drug
AND
GENOTYPE: Genetic panel from blood sample drawn at time of GRAVITAS platelet function testing or follow-up
CYP2C19 CYP3A5 CYP2B6 CYP3A4 ABCB1 P2RY12 IRS-1 PAR-1
Baseline clinical characteristics (e.g., DM)
Concomitant Meds (e.g., PPIs)
Independent determinants of residual platelet reactivity (PRU) on standard clopidogrel therapy
Independent determinants of incremental response to high-dose clopidogrel (change in PRU) in non-responders to standard therapy
SCRIPPS CLINIC
Funded through an investigator-initiated grant to Scripps Genomic Institute from BMS/sanofi aventis

29. Resistance To Aspirin and Clopidogrel Conclusions
Neither functional nor genetic testing is yet appropriate for routine use to guide antiplatelet therapy
It may be in the future
We have a lot to learn between now and then CP