What Should we Learn from the POPular Study? Neal Kleiman Director Cardiac Catheterization Laboratory Methodist DeBakey Heart Center Professor of Medicine Weill Medical College of Cornell University

The Three Principles Platelet ‘activity’ studies suggest that in patients who are clopidogrel-dependent, measures of platelet activity predict subsequent events

If this is really the case, then therapeutic decisions might be made based on platelet ‘activity’ studies. Increase clopidogrel dose Use newer P2Y12 antagonists and accept increased risk of bleeding Add cilostazol Substitute surgery for PCI

Some studies are hard to do, some aren’t. LTA requires tech, centrifuging, and nephelometic measurements. VerifyNow requires no pipette and can be done at the bedside or in the CCL. PFA-100 requires little time, but is a fairly bulky machine. Plateletworks requires little time and is a whole blood CBC assay. Measuring adhesion to collagen fibrils and subsequent aggregation is incredibly painful and results are difficult to standardize.

What Do Activated Platelets Do? Activation Prothrombin 1 4 Va Thrombin Vasoconstrictors + Fibrinogen Xa 2 3 Mitogens + Growth Factors Aggregation Adhesion 6-8-98

Evidence that pre mRNA is Spliced in Activated Circulating Platelets, i.e. IL-1 b is Synthesized De Novo IL-1 b is a cytokine that upregulates many of the genes involved in inflammation Denis, Cell:2005: 122: 379

Correlation Coefficients Between Assays Lordkipanidze, M. et al. Eur Heart J 2008 0:ehn419v1-9; doi:10.1093/eurheartj/ehn419

Gray lines represent 95% CIs for agreement Bland-Altman Plots of Agreement Between Assays Gray lines represent 95% CIs for agreement k varied from 0.06 to 0.36 Lordkipanidze, M. et al. Eur Heart J 2008 29:2877-2885; doi:10.1093/eurheartj/ehn419

Inter-individual Variability: Clopidogrel 600 mg 100 y=35.28 + 29.09 * e-1.072* x r2=0.101 80 n = 1001 600 mg Clopidogrel 60 Maximal Aggregation 5 µmol/L ADP (%) 40 20 2 4 6 8 10 Time from Loading Dose to Catheterization (hr) Hochholzer W et al. Circulation. 2005;111:2560-2564. 10

10% ↑ in aggregation  OR 1.32 (1.04-1.61) of 30 d MACE Prospective Study of ADP Induced Aggregation in Patients Loaded with 600 mg of Clopidogrel 802 Patients; 19 events in 15 pts @ 30 d Aggregation in response to 5 mM ADP 30 Day MACE (%) ↑ Age ↑ BMI ↑ % with Diabetes ↑ Active smokers 10% ↑ in aggregation  OR 1.32 (1.04-1.61) of 30 d MACE Hochholzer: JACC;2006: 48:1742

Effect of CYP2C19 Haplotypes on Ex vivo and Clinical Responses to Clopidogrel Mega, NEJM: 2009;360:354-362

U Mass Study of Cox-1 Dependent and Independent Markers of Platelet Activity 682 Patients presenting for diagnostic catheterization 34% also on clopidogrel Followed for death/MI/revasc for 18-24 months Frelinger, A. L. et al. Circulation 2009;120:2586-2596

POPular Study Consecutive patients on clopidogrel undergoing elective stent implantation N=1069 (~2/3 DES) LTA 5 mM ADP n=1049 LTA 5 mM ADP n=1051 VerifyNow P2Y12 n=1052 IMPACT-R N=910 IMPACT-R ADP N=910 PFA-100 COL/ADP N=812 Primary Endpoint – 1 Y Death, MI, Stent Thrombosis, or Stroke Safety EP – 1 Y Major and Minor Bleeding (TIMI grade)

POPular – Assays Tested Light transmittance aggregometry 5 and 20 mM ADP in PRP VerifyNow P2Y12 assay Agglutination test Plateletworks Whole blood platelet count IMPACT-R Cone and platen viscometer w and w/o ADP PFA-100 Shear stress (narrow aperture)

Cutoff Values Derived from ROC and 1 Year Outcomes Cutoff Value (HPR vs NPR) LTA 5 mM ADP 42.9% LTA 20 mM ADP 64.5% VerifyNow ADP 236 PRU Plateletworks 80.5% IMPACT-R 8.4 SC IMPACT-R ADP 3.0 SC PFA-100 COL/ADP 116 s Innovance PFA 299 s

POPular—Prediction of the Composite Outcome Logistic regression model incorporating clinical and procedural risk factors  AUC = 0.72 AUC P LTA 5 mM ADP 0.74 0.004 LTA 20 mM ADP 0.73 <0.0001 VerifyNow P2Y12 Plateletworks 0.78 0.001 IMPACT-R 0.72 0.17 IMPACT-R -ADP 0.92 PFA-100 0.15 Innovance PFA P2Y 0.24

POPular -Bleeding No assay predicted hemorrhage

What’s Required to WRAP the Package (1)? Reproducibility Prediction of a therapeutic resonse Biologic plausibility Are we measuring a function of platelet activity that affects the outcomes? What is the temporal stability of the estimates? Is the estimate independent of clinical status? Is a single measurement of platelet ‘activity’ likely to predict an event that occurs one year later?

Reported Drug-Drug Interactions with Antiplatelet Regimens Mechanism Rantidine Aspirin ↓ ↓ Absorption Atorvastatin Clopidogrel ↓ CYP3A4 Omeprazole ↓ CYP2C19 Caffeine ↑ ↑ cAMP level Ibuprofen Blockade of Ser529 Ca++ Block. Rifampin ↑ CYP3A4

Temporal Variation in Aspirin Resistance Among Survivors of Suspected Acute MI ASA Resistance Baseline N=46 1 Year F/U N=17 AMI (n=37) 43% (95% CI: 27% - 59%) 11% (95% CI 1% - 21%) No AMI (n=150) 20% (95% CI 14%-26%) 9% (95% CI 5% - 13%) Poulsen: Thrombosis Research: 2007: 120: 477

What Should we Learn from POPULAR? Confirmation of an association between high platelet reactivity and common ischemic events. Attempt to establish appropriate cutoff points for each test. Suggestion that platelet reactivity measurements may not be so independent of traditional clinical and procedural markers.

What Have We Yet to Learn from POPular? Remaining Needs Validation of the determined cutpoints in another dataset. To determine whether prediction of HPR with one assay also predicts HPR with other assays. Are they identifying the same patients? Need to demonstrate a benefit for therapy guided by the assays.