Clinical trial NCT02548650
Conditions: Myocardial Infarction Diabetes Mellitus Peripheral Arterial Disease
Keywords: myocardial infarction diabetes mellitus vorapaxar peripheral arterial disease
Sponsor: University of Florida
Start date: 2016-03-25; Completion date: 2019-02-14
Enrollment: 66 participants; Allocation: NON_RANDOMIZED; Intervention model: PARALLEL

Brief summary:
Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor, more frequently clopidogrel, represents the standard of care for the long-term secondary prevention of atherothrombotic events in patients with myocardial infarction (MI) or peripheral arterial disease (PAD). However, rates of ischemic recurrences remain high. Vorapaxar is a protease-activated receptor (PAR)-1 inhibitor, which exerts potent inhibition of thrombin-mediated platelet aggregation. Patients with diabetes mellitus (DM) are known to be at increased risk of recurrent atherothrombotic events, which translates into worse outcomes, despite the use of standard of care therapy. This is in part due to the hyperreactive platelet phenotype, which characterizes DM patients, and to inadequate response to oral antiplatelet agents, including clopidogrel. Therefore, vorapaxar is an attractive treatment option for DM patients with a prior MI. The pharmacodynamic (PD) effects of vorapaxar in DM patients and how these may differentiate from non-DM patients has not been explored. Further, the role of vorapaxar as part of a dual antithrombotic treatment regimen combined with clopidogrel (and stopping aspirin) represents another important area of clinical interest. The proposed prospective, parallel-design study conducted in patients post-MI or with PAD with and without DM will aim the assess the pharmacodynamic effects of vorapaxar in addition to standard DAPT with aspirin and clopidogrel as well as in combination with clopidogrel only following aspirin withdrawal.

Detailed description:
Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor, more frequently clopidogrel, represents the standard of care for the long-term secondary prevention of atherothrombotic events in patients with myocardial infarction (MI) or peripheral arterial disease (PAD). However, rates of ischemic recurrences remain high, in part due to the fact that other platelet signaling pathways, such as thrombin-induced platelet aggregation, continue to be activated. Vorapaxar is a novel, orally active, competitive and slowly reversible protease-activated receptor (PAR)-1 inhibitor, which exerts potent inhibition of thrombin-mediated platelet aggregation. It is approved for clinical use by the Food and Drug Administration for the reduction of thrombotic cardiovascular events in patients with a history of MI or with peripheral arterial disease. Patients with DM are known to be at increased risk of recurrent atherothrombotic events, which translates into worse outcomes, despite the use of standard of care therapy. This is in part due to the hyperreactive platelet phenotype, which characterizes DM patients, and to inadequate response to oral antiplatelet agents, including clopidogrel. Importantly, in DM patients with prior MI included in the TRA 2P trial, vorapaxar reduced the primary composite end point at 3 years by 27% and led to a greater absolute risk reduction compared with those without DM. Therefore, vorapaxar is an attractive treatment option for DM patients with a prior MI. However, to date the PD effects of vorapaxar in DM patients and how these may differentiate from non-DM patients has not been explored. Further, current trends in clinical practice are seeing many patients discontinue aspirin and maintain clopidogrel. Hence, the role of vorapaxar as part of a dual antithrombotic treatment regimen combined with clopidogrel (and stopping aspirin) represents another important area of clinical interest, in order to maximize ischemic protection while reducing the risk of bleeding. The proposed prospective, parallel-design study conducted in patients post-MI or with PAD with and without DM will aim the assess the pharmacodynamic effects of vorapaxar in addition to standard DAPT with aspirin and clopidogrel as well as in combination with clopidogrel only following aspirin withdrawal. Pharmacodynamic assessments will be performed at multiple time point, with different assays exploring multiple pathways of platelet aggregation.

Arms: arm 1: Triple therapy (vorapaxar 2.5mg od plus clopidogrel 75 mg od and aspirin 81 mg od) will be administered for 30 days; then patients will stop aspirin and will take dual treatment (vorapaxar 2.5mg od plus clopidogrel 75 mg od ) for other 30 days. arm 2: Triple therapy (vorapaxar 2.5mg od plus clopidogrel 75 mg od and aspirin 81 mg od) will be administered for 30 days; then patients will stop aspirin and will take dual treatment (vorapaxar 2.5mg od plus clopidogrel 75 mg od ) for other 30 days.
Interventions: intervention 1: Vorapaxar intervention 2: Clopidogrel intervention 3: Aspirin
Intervention descriptions: intervention 1: Triple therapy with DAPT plus vorapaxar (vorapaxar 2.5mg od plus clopidogrel 75 mg od and aspirin 81 mg od) will be administered for 30 days; then patients will stop aspirin and will take dual treatment (vorapaxar 2.5mg od plus clopidogrel 75 mg od ) for other 30 days intervention 2: Triple therapy with DAPT plus vorapaxar (vorapaxar 2.5mg od plus clopidogrel 75 mg od and aspirin 81 mg od) will be administered for 30 days; then patients will stop aspirin and will take dual treatment (vorapaxar 2.5mg od plus clopidogrel 75 mg od ) for other 30 days intervention 3: Triple therapy with DAPT plus vorapaxar(vorapaxar 2.5mg od plus clopidogrel 75 mg od and aspirin 81 mg od) will be administered for 30 days; then patients will stop aspirin and will take dual treatment (vorapaxar 2.5mg od plus clopidogrel 75 mg od ) for other 30 days

Protocol documents:
Prot_SAP_000.pdf: 
1 
 
 
Pharmacodynamic Effects of Vorapaxar as an Add-On Antiplatelet Therapy in 
Patients with and without Diabetes Mellitus: 
the Optimizing anti-Platelet Therapy In diabetes MellitUS (OPTIMUS)-5 Study 
 
NCT02548650 
Protocol version 2, approval date 10/02/2018 
 
 
 
 
 
 
 
Dominick J. Angiolillo, MD, PhD 
University of Florida College of Medicine-Jacksonville 
655 West 8th Street 
Jacksonville, Florida, 32209 
Tel: +1-904-244-3933 
Fax: +1-904-244-3102 
E-mail: dominick.angiolillo@jax.ufl.edu    
 
 
 
 
 


2 
 
 
 
Summary  
Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor, more frequently 
clopidogrel, represents the standard of care for the long-term secondary prevention of 
atherothrombotic events in patients with myocardial infarction (MI) or peripheral arterial disease 
(PAD). However, rates of ischemic recurrences remain high, in part due to the fact that other 
platelet signaling pathways, such as thrombin-induced platelet aggregation, continue to be activated. 
Vorapaxar is a novel, orally active, competitive and slowly reversible protease-activated receptor 
(PAR)-1 inhibitor, which exerts potent inhibition of thrombin-mediated platelet aggregation. It is 
approved for clinical use by the Food and Drug Administration for the reduction of thrombotic 
cardiovascular events in patients with a history of MI or with PAD. Patients with DM are known to 
be at increased risk of recurrent atherothrombotic events, which translates into worse outcomes, 
despite the use of standard of care therapy. This is in part due to the hyperreactive platelet 
phenotype, which characterizes DM patients, and to inadequate response to oral antiplatelet agents, 
including clopidogrel. Importantly, in DM patients with prior MI included in the TRA 2P trial, 
vorapaxar reduced the primary composite end point at 3 years by 27% and led to a greater absolute 
risk reduction compared with those without DM. Therefore, vorapaxar is an attractive treatment 
option for DM patients with a prior MI. However, to date the PD effects of vorapaxar in DM 
patients and how these may differentiate from non-DM patients has not been explored. Further, 
current trends in clinical practice are seeing many patients discontinue aspirin and maintain 
clopidogrel. Hence, the role of vorapaxar as part of a dual antithrombotic treatment regimen 
combined with clopidogrel (and stopping aspirin) represents another important area of clinical 


3 
 
interest, in order to maximize ischemic protection while reducing the risk of bleeding. The proposed 
prospective, parallel-design study conducted in post-MI and PAD patients with and without DM 
will aim the assess the pharmacodynamic effects of vorapaxar in addition to standard DAPT with 
aspirin and clopidogrel as well as in combination with clopidogrel only following aspirin 
withdrawal. Pharmacodynamic assessments will be performed at multiple time point, with different 
assays exploring multiple pathways of platelet aggregation. 


4 
 
Background and Significance 
Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor represents the 
standard of care for the long-term secondary prevention of atherothrombotic events in patients with 
myocardial infarction (MI) [1]. Clopidogrel is the most widely used P2Y12 receptor inhibitor and the 
use of DAPT with aspirin and clopidogrel has consistently demonstrated to reduce the risk of 
thrombotic recurrences in patients with acute coronary syndrome (ACS) [2]. However, despite this 
treatment regimen, rates of ischemic recurrences remain elevated, especially in high risk patients, 
such as those with diabetes mellitus (DM) [2-4]. This is in part due to the fact that other platelet 
signaling pathways, such as thrombin-induced platelet aggregation, continue to be activated and can 
thus contribute to thrombus formation [5,6]. In particular, thrombin is one of the most potent 
platelet activators, and the surface of activated platelets is the main source of circulating thrombin 
[5-7]. Vorapaxar is a novel, orally active, highly selective, competitive and slowly reversible 
protease-activated receptor (PAR)-1 inhibitor, which exerts potent inhibition of thrombin-mediated 
platelet aggregation [8,9]. Pharmacokinetic studies have shown that vorapaxar has a dissociation 
half-life as long as 20 hours which leads to consistent pharmacodynamic (PD) effects [8,9]. 
Importantly, when vorapaxar is added to DAPT, enhanced P2Y12 inhibition has been shown due to 
the potential interplay between purinergic and thrombin-mediated platelet signaling pathways [10]. 
Recently, vorapaxar (2.5 mg once daily) has been approved for clinical use by the US Food and 
Drug Administration (FDA) and by the European Medicines Agency for the reduction of thrombotic 
cardiovascular events in patients with a history of MI or with peripheral arterial disease (PAD), and 
should be used in addition to standard-of-care antiplatelet therapy with aspirin and/or clopidogrel 
[11,12]. These indications are largely attributed to the findings of the TRA 2P-TIMI 50 (Thrombin 
Receptor Antagonist in Secondary Prevention of Atherothrombotic Ischemic Events - Thrombolysis 


5 
 
in Myocardial Infarction 50) trial [13]. In particular, the trial showed that the use of vorapaxar in 
addition to standard antiplatelet therapy was effective in the secondary prevention of recurrent 
thrombotic events (cardiovascular death, MI, or stroke) in patients with previous atherothrombosis, 
particularly those with prior MI and PAD, albeit at the cost of increased bleeding [13,14]. 
Patients with DM are known to be at increased risk of recurrent atherothrombotic events, 
which translates into worse outcomes, despite the use of standard of care therapy [4,15]. This is in 
part due to the hyperreactive platelet phenotype with upregulation of multiple platelet signaling 
pathways, including thrombin, which characterizes patients with DM [4]. Importantly, increased 
platelet reactivity may account for inadequate response (i.e. reduced platelet inhibitory effects) to 
oral antiplatelet agents, including the P2Y12 receptor antagonist clopidogrel, contributing to worse 
outcomes [4]. Notably, in DM patients and prior MI included in the TRA 2P trial, vorapaxar 
reduced the primary composite end point at 3 years by 27% (p=0.002), and led to a greater absolute 
risk reduction (absolute risk difference: -3.50%) compared with those without DM (absolute risk 
difference: -1.36%) with a number needed to treat of 29 [16]. The benefit of vorapaxar was also 
consistent in patients with PAD, although no specific subgroup data are available based on DM 
status [17]. Therefore, patients with DM, characterized by diffuse atherothrombotic disease 
manifestations and enhanced risk of ischemic recurrences, seem particularly attractive for treatment 
with vorapaxar. However, to date the PD effects of vorapaxar in patients with DM, as well as the 
comparative effects of DM versus non-DM patients has not yet been explored. 
Study Rationale and aims 
Despite the encouraging clinical findings from TRA-2P and the potential for an uptake of 
vorapaxar in daily practice, there is limited data on the PD effects of vorapaxar as an add-on therapy 
in key high-risk settings, such as prior MI or PAD patients with DM, where enhanced platelet 


6 
 
inhibition by means of PAR-1 blockade, may be more clinically beneficial. Further, given the length 
of the TRA-2P trial (median follow-up of 30 months), many patients were enrolled in the trial while 
on standard DAPT with aspirin and clopidogrel, but then interrupted one antiplatelet agent as per 
standard of care [13]. Although most patients discontinue clopidogrel therapy and continue aspirin, 
current trends in clinical practice are seeing many patients discontinue aspirin and maintain 
clopidogrel, which provides more comprehensive platelet inhibition compared with aspirin [18].  
Hence, the role of vorapaxar as part of a dual antithrombotic treatment regimen combined with 
clopidogrel (and stopping aspirin) represents another important area of clinical interest, in order to 
maximize ischemic protection while reducing the risk of bleeding. Further, the comparative PD 
effects of vorapaxar in addition to different combination of antiplatelet therapy in patients with DM 
versus those without DM is currently unknown. A comprehensive understanding of the PD effects 
of vorapaxar as an add-on therapy will thus be informative to the practicing clinician. Therefore, the 
aim of the proposed investigation is to assess the PD effects of vorapaxar in addition to DAPT with 
aspirin and clopidogrel as well as to antiplatelet therapy with clopidogrel, in the setting of post-MI 
or PAD patients with and without DM.  
Research Plan 
Study Population 
Inclusion criteria: 
1. Patients with a prior MI between 2 weeks and 24 months or with PAD. 
2. On DAPT with low-dose aspirin (81mg od) and clopidogrel (75mg od) as per standard-of-care 
for at least 14 days. 
3. Age ≥ 18 years old. 


7 
 
4. Patients entering the DM cohort will need to have diagnosis of type 2 DM defined according to 
the WHO definition [19], on treatment with oral hypoglycemic agents and/or insulin for at least 
two months, without any changes in regimen. 
 
Exclusion criteria: 
 
1. History of ACS in the previous 2 weeks. 
2. History of stroke, transient ischemic attack, or intracranial hemorrhage. 
3. Active pathological bleeding, history of bleeding events or increased risk of bleeding. 
4. Known severe hepatic impairment. 
5. Type 2 DM on dietary control.  
6. Use of strong CYP3A inhibitors (e.g., ketoconazole, itraconazole, posaconazole, clarithromycin, 
nefazodone, ritonavir, saquinavir, nelfinavir, indinavir, boceprevir, telaprevir, telithromycin and 
conivaptan) or inducers (e.g., rifampin, carbamazepine, St. John’s Wort and phenytoin). 
7. On treatment with any oral anticoagulant (vitamin K antagonists, dabigatran, rivaroxaban, 
apixaban, edoxaban). 
8. On treatment with any antiplatelet agent other than aspirin and clopidogrel in the past 14 days. 
9. Creatinine clearance <30 mL/minute. 
10. Platelet count <80x106/mL 
11. Hemoglobin <10g/dL 
12. Hemodynamic instability 
13. Pregnant females [women of childbearing age must use reliable birth control (i.e. oral 
contraceptives) while participating in the study]. 


8 
 
Research Design  
The proposed investigation will be a prospective parallel-design PD study conducted in 
post-MI or PAD patients with and without DM. Although vorapaxar is approved for use irrespective 
of the timing of the MI, the rationale for including patients after 2 weeks is that this time frame 
allows clopidogrel to exert its full antiplatelet effects [20,21]. 
The study will be performed at the University of Florida Health Science Center at UF Health 
Jacksonville - Division of Cardiology. Patients will be recruited in the Cardiology Clinics of our 
institution and will be screened by Cardiology Research staff, who will verify that all candidates 
meet inclusion and exclusion criteria. Results from blood tests performed within the last 90 days 
will be considered valid for screening purposes. If these are not available, a blood sample will be 
collected for the screening phase. 
After providing written informed consent, patients on DAPT with aspirin and clopidogrel 
meeting study entry criteria will be divide in two groups according to DM status and will receive 
vorapaxar 2.5mg od in addition to DAPT. Triple therapy (vorapaxar 2.5mg od plus clopidogrel 75 
mg od and aspirin 81 mg od) will be administered for 30±5 days; then patients will stop aspirin and 
will take dual treatment (vorapaxar 2.5mg od plus clopidogrel 75 mg od) for other 30±5 days. 
Blood sampling for PD testing will be conducted at 3 time-points: baseline (while patients will be 
on standard DAPT); after 30±5 days of triple therapy; 30±5 days after dual treatment. At each time 
point, blood will be collected before the morning dose of clopidogrel and vorapaxar, in order to 
measure trough levels of platelet inhibition. Although no wash-out period will be performed, the 
risk of carry-over effect is considered low, as the treatment period will be significantly longer than 
the offset of aspirin antiplatelet effect (7-10 days). During study treatment major adverse cardiac 
events (death, MI, stroke, and urgent revascularization procedures) and serious adverse events 


9 
 
(bleeding and other adverse events) will be collected in each group. Bleeding will be defined by the 
BARC (Bleeding Academic Research Consortium) definition [22].  
After study completion, patients will resume antiplatelet treatment regimen at the discretion 
of the treating physician. A flow diagram of the study design is illustrated below.  
 
 
Laboratory assessments 
Peripheral venous blood samples (20 mL) will be drawn through a short venous catheter 
inserted into a forearm vein and collected in citrate, EDTA, and serum tubes as appropriate for 
assessments. The first 2-4 mL of blood will be discarded to avoid spontaneous platelet activation. 
Blood sampling for PD will be performed at 3 time points as indicated above in the study design 
section. Various PD assays will be performed as described below. Given the potential interplay 


10 
 
between PAR-1 and P2Y12 mediated signaling, assessments specific for both pathways will be 
conducted [10]: 
1. 
Light transmittance aggregometry (LTA)  
2. 
Whole blood vasodilator-stimulated phosphoprotein (VASP) 
3. 
VerifyNow P2Y12 
4. 
Thrombelastograph Coagulation Analyzer TEG 6s Series system (CORA® system) 
5. 
Serum thromboxane B2 
 
Description of laboratory assays 
1) Light transmittance aggregometry (LTA): Platelet aggregation will be performed using LTA 
according to standard protocols. Blood will be collected in citrated (3.8%) tubes. LTA will be 
assessed using platelet rich plasma (PRP) by the turbidimetric method in a 2-channel aggregometer 
(Chrono-Log 490 Model, Chrono-Log Corp., Havertown) as previously described [23,24]. Platelet 
agonists will include AA (1 mM), collagen (3µg/ml), ADP (5 and 20 µM), TRAP (15 μM), and a 
combination of 2 µg/ml collagen-related peptide + 5 µM ADP + 15 µM TRAP (CAT). The reagent 
cocktail CAT will allow to assess the overall platelet response to a combination of agonists that 
leads to activation of multiple platelet pathways. PRP will be obtained as a supernatant after 
centrifugation of citrated blood at 1000 rpm for 10 minutes. The isolated PRP will be kept at 37° C 
before use. Platelet poor plasma (PPP) will be obtained by a second centrifugation of the blood 
fraction at 2800 rpm for 10 minutes. Light transmission will be adjusted to 0% with the PRP and to 
100% for the PPP for each measurement. Curves will be recorded for 6 minutes and platelet 
aggregation will be determined as the maximal percent change (MPA) in light transmittance from 
baseline using PPP as a reference. 


11 
 
2) Whole blood vasodilator-stimulated phosphoprotein (VASP): VASP phosphorylation (VASP-P) 
is a marker of P2Y12 receptor reactivity. VASP will be assessed according to standard protocol 
using labeled monoclonal antibodies by flow cytometry with the Platelet VASP-FCM kit (Biocytex 
Inc., Marseille, France) as previously described [25]. PGE1 increases VASP-P levels by stimulation 
of adenylate cyclase. Binding of ADP to P2Y12 leads to Gi-coupled inhibition of adenylate cyclase. 
Therefore, the addition of ADP to PGE1-stimulated platelets reduces PGE1-induced VASP-P 
levels. If P2Y12 receptors are successfully inhibited by inhibitors, addition of ADP will not reduce 
the PGE1-stimulated VASP-P levels. The platelet reactivity ratio (PRI) will be calculated after 
measuring VASP-P levels after stimulation with PGE1 (MFI PGE1) and also PGE1 + ADP (MFI 
PGE1 + ADP). The P2Y12 reactivity ratio = ([MFI PGE1] – [MFI PGE1 + ADP]/[MFI PGE1]) x 
100%. 
3) VerifyNow (VN) P2Y12: The VerifyNow System is a turbidimetric based optical detection 
system which measures platelet induced aggregation as an increase in light transmittance 
(Accumetrics, San Diego, CA) and will be utilized according to manufacturer’s instructions, as 
previously described [25]. The assay is based on microbead agglutination and uses specific reagents 
for the pathways of interest. The VN-P2Y12 assay, by combining ADP+PGE1, measures changes in 
platelet function specific to P2Y12 receptor inhibitors. The assay is based upon the ability of 
activated platelets to bind fibrinogen. Fibrinogen-coated microparticles aggregate in proportion to 
the number of GP IIb/IIIa receptors expressed. Microbead aggregation is more rapid and 
reproducible if platelets are activated; therefore the reagents are incorporated into the assay channel 
to induce platelet activation without fibrin formation. Light transmittance increases as activated 
platelets bind and aggregate fibrinogen-coated beads. The instrument measures this change in 
optical signal and reports results in P2Y12 Reaction Units (PRU). 


12 
 
4) TEG 6s Series system (CORA® system): the TEG 6s system (Haemonetics Corporation, 
Braintree, MA, USA) will be used according to manufacture instructions [26]. In brief, the CORA® 
system is a new generation portable thrombelastography technology able to evaluate all phases of 
hemostasis, including time to clot formation, rate of clot formation, strength of clot and residual clot 
strength due to antiplatelet drugs, rate of clot lysis. Disposable assay cartridges contain all of the 
components necessary to allow the analyzer to prepare samples and perform hemostasis tests. The 
analyzer automatically draws the blood into the active area of the cartridge, meters the exact amount 
required for the test, and mixes it with the reagents spotted in the cartridge. The analyzer then 
monitors the harmonic motion of a pendant drop of blood in response to external vibration. As the 
sample transitions from a liquid state to a gel-like state during clotting, the modulus of elasticity and 
resonant frequency increase. The instrument measures these variations in resonant frequency during 
clotting and lysis. The results are displayed in a table and on a graphical tracing that reflects a 
hemostasis profile of clot formation. The resulting hemostasis profile is a measure of the time it 
takes for the first measurable clot to be formed, the kinetics of clot formation, the strength of the 
clot, and the breakdown of the clot, or fibrinolysis. In particular, the PlateletMapping Cartridge are 
used to assess platelet function in patients who have received platelet inhibiting drugs. The 
PlateletMapping assay consists of a set of agonists, ADP and arachidonic acid (AA) platelet 
agonists together with ActivatorF, which can measure the inhibition of platelet function. This assay 
specifically determines the MA (Maximum Amplitude, a measure of clot strength) and the 
reduction in MA due to antiplatelet therapy and reports it as a percentage of reduction in clot 
strength. The assay uses AA and ADP agonists to generate test results that reflect the inhibiting 
effects of antiplatelet agents such as TxA2 Inhibitors (e.g., aspirin) and ADP P2Y12 inhibitors (e.g., 
clopidogrel). Since thrombin (present in blood samples) is the primary and most potent activator of 


13 
 
platelets, its activity must be inhibited with heparin so that the platelet activating effects of ADP and 
AA can be measured. Since thrombin has been rendered inactive by heparin, activatorF is used to 
replace thrombin’s role in the conversion of fibrinogen to fibrin and Factor XIII to Factor XIIIa. 
Thus, with this cross-linked fibrin network as the foundation, additional clot strength due to 
platelet-fibrin bonding related to ADP and AA platelet receptor activation can be measured. The 
HKH reagent, a combination of kaolin and heparinase, generates test data for the uninhibited MA 
resulting from thrombin activation of the blood sample, while the heparinase neutralizes the effects 
of heparin. The HKH test provides measures of R (Reaction time; the amount of time between the 
start of the test and the beginning of coagulation), K (the speed of formation of the clot from R time 
to a specific clot strength), Angle (the speed of clot strengthening), LY30 (Percent lysis 30 minutes 
after MA is finalized) and MA parameters; The activatorF test provides the contribution of fibrin to 
the overall strength of the clot.  This test value is used in the calculation of aggregation/inhibition 
for MA ADP and MA AA. The AA and ADP test provide measures of MA, percent inhibition and 
percent aggregation. 
5) Serum thromboxane B2: The concentration of serum thromboxane B2 (TXB2) will be measured 
by using the TXB2 EIA kit (Cayman Chemical Company, Ann Arbor, MI) according to the 
instructions of the manufacturer, as previously described [27]. Briefly, samples will be diluted with 
EIA buffer to bring their concentrations within the range of the standard curve. No other 
purification will be performed on any of the samples. A standard curve will be established by serial 
dilution of TXB2 between 1000 pg/mL and 7.8 pg/mL using EIA buffer as the matrix. The 
concentration of TXB2 in the samples will be calculated from a logistic 4-parameter fit of the 
standard concentrations versus percentage bound/maximum bound. 
 


14 
 
Study endpoints and sample size calculation 
The primary end point of our study is the comparison of CAT-induced MPA measured by 
LTA between vorapaxar plus DAPT and vorapaxar plus clopidogrel. We hypothesize that vorapaxar 
in addition to single antiplatelet therapy with clopidogrel will be non-inferior to vorapaxar in 
addition to DAPT with aspirin and clopidogrel in MPA after 30±5 days of treatment in both DM 
and non-DM patients.  Under the assumption of 0 difference in mean CAT-induced MPA between 
vorapaxar plus clopidogrel and vorapaxar plus DAPT and a common standard deviation of 13%, a 
sample size of 28 patients per group allows for the 95% confidence interval (CI) to stay within ± 
10% with a 80% power and alpha=0.025. Considering the two groups (DM and non-DM), a total of 
56 patients with valid primary end point data will need to be included. Assuming up to 40% rate of 
invalid results due to haemolysis or drop-out, up to 79 patients will need to be enrolled. Non-
inferiority will be assessed using a 95% CI of the difference in mean MPA between the 2 arms. As 
there are no preliminary data in this setting, the 10% non-inferiority margin was arbitrarily defined. 
Mean values of platelet aggregation and variability were estimated based on previous data of 
vorapaxar in addition to DAPT with aspirin and clopidogrel [24]. This approach is in agreement 
with recommendations for pilot investigations [28]. 
Other objectives will include the comparisons between DM and non-DM patients of all PD 
parameters measured by multiple assays, and the comparisons between levels of platelet inhibition 
achieved by DAPT (baseline therapy) versus levels achieved by antiplatelet therapy including 
vorapaxar. The effects of additive inhibition of the thrombin-mediated platelet activation pathway, 
with or without aspirin therapy, on serum thromboxane levels will also be evaluated. 
Statistical analysis plan  


15 
 
Categorical variables will be expressed as frequencies and percentages. Continuous 
variables will be presented as mean ± SD or median [IQR]. Continuous variables will be analyzed 
for normal distribution with the Kolmogorov-Smirnov test. Comparisons between categorical 
variables will be performed using two-tailed Fisher’s exact test or the Pearson's chi-square test. 
Student´s t test, Mann-Whitney U-test and Wilcoxon test will be used to compare continuous 
variables when appropriate. An analysis of covariance (ANCOVA) method with a general linear 
model, using baseline variables significantly different between groups as covariates, will be used to 
evaluate the overall difference between groups and all between-groups comparisons, in line with 
other PD studies [25]. Student´s t test or Wilcoxon test will be used to evaluate intragroup 
comparisons. Non-inferiority will be assessed using a 95% CI of the difference in mean MA 
between vorapaxar plus prasugrel/ticagrelor and vorapaxar plus DAPT. 
A p-value of <0.025 will be considered to be statistically significant for the non-inferiority 
analysis. A 2-tailed p value of < 0.05 is considered to indicate a statistically significant difference 
for all the other analyses performed. Statistical analysis will be performed by our group using SPSS 
v22.0 software (SPSS Inc. Chicago, IL).  
Publication Strategy/Additional Information  
Study subjects will be identified first (months 1-16): we expect to enroll 4 subjects monthly 
and complete enrollment in 16 months (total: 64 subjects enrolled). Months 17-18 will be implied 
for statistical analysis and months 19-20 for manuscript preparation. We intend to present data at a 
major scientific meeting at completion of the study. 
We anticipate no major problems with the described protocol since the approach is a straight 
forward prospective study and is based on well-established methods. However, since there is limited 
experience with vorapaxar to define platelet function, variability may be higher than expected and 


16 
 
we cannot currently perform a detailed sample size calculation. We anticipate adding this to the 
protocol after inclusion of the study population has been completed. If the sample size after one 
year is estimated to be too small, additional patients will be included. This approach is in agreement 
with recommendations for pilot investigations [28]. 
Possible Discomforts and Risk 
In clinical trials, the most common clinical side effects of vorapaxar were anemia (5%), 
depression (2.4%) and rash (2.2%) [13,20]. The most important adverse effect associated with the 
use of vorapaxar is bleeding. The risk of TIMI clinically significant bleeding with vorapaxar is 
15.8% and 11.1% with placebo (HR 1.46; 95% CI, 1.36-1.57, p<0.001); the risk of TIMI non-
CABG-related major bleeding with vorapaxar is 2.8% and 1.8% with placebo (HR 1.46; 95% CI, 
1.22-1.75, p<0.001); the risk of intracranial bleeding (intracerebral, subdural or epidural) with 
vorapaxar is 1% vs 0.5% with placebo (HR 1.94; 95% CI 1.39-2.70; p <0.001) [13]. However, such 
bleeding prevalence occurred in the setting of long-term (3 years) trial, while our study is limited to 
only approximately 60 days of vorapaxar therapy. We have also excluded from the study patients at 
increased risk of bleeding complications [11,12,29]. Moreover, the use of vorapaxar in this study is 
limited to the intended for use population at low risk of bleeding. All clinical events described 
above, if they were to occur, as well as death, myocardial infarction, stroke, and urgent 
revascularization procedure with PCI or coronary artery bypass grafting will be recorded. Bleeding 
data will be collected using BARC definitions [22]. Clinical events will be evaluated by a local 
committee, comprised of 2 faculty members (2 cardiologists), not directly involved in the research. 
In the event of a report of a serious adverse event (major bleeding – defined as life-threatening: 
fatal, symptomatic intracranial hemorrhage, leading to a drop in hemoglobin of at least 5 g/dL, 
significant hypotension requiring intravenous inotropes, requiring surgical intervention, or requiring 


17 
 
transfusion of 4 or more units of blood; non–life-threatening: substantially disabling, intraocular 
bleeding leading to vision loss, or requiring at least 2 units of blood; thrombocytopenia <50,000 ) 
the local committee will meet and antiplatelet treatment management will be managed according to 
physician recommendation. 
Definition of Adverse Events 
An adverse event is any unintended or undesirable experience that occurs during the course 
of the clinical investigation whether or not it is considered to be therapy related.  This includes any 
newly occurring event or previous condition that has increased in severity or frequency since the 
initiation of study treatment.  Adverse events will be followed until resolution while the patient 
remains on-study.  Once the patient is removed from study, events thought to be related to the study 
therapy will be followed until resolution or until the patient starts a new treatment regimen. 
Serious Adverse Events (SAE): An adverse event occurring while on study and considered 
related (reasonable possibility that the study treatment caused the adverse experience) to the study 
treatment that results in any of the following outcomes: 
- Death 
- A life-threatening adverse experience. 
- A persistent or significant disability, incapacity, or is a congenital anomaly, or birth  
defect. 
- Requires inpatient hospitalization, or prolongation of existing hospitalization. 
 
The definition of serious adverse event also includes ‘important medical event’.  Medical 
and scientific judgment should be exercised in deciding whether expedited reporting is appropriate 
in other situations, such as important medical events that may not be immediately life-threatening or 


18 
 
result in death or hospitalization but may jeopardize the patient and/or may require medical or 
surgical intervention to prevent one of the other outcomes listed in the definition above.  These 
should also usually be considered serious.  Examples of such events are intensive treatment in an 
emergency room or at home for allergic bronchospasm; blood dyscrasias or convulsions that do not 
result in hospitalization; or development of drug dependency or drug abuse. 
Possible benefits 
The present investigation is aimed to evaluate the PD effects of vorapaxar as an add-on 
therapy to standard antiplatelet treatment in patients with previous MI or PAD. This study is not 
designed to evaluate differences in clinical benefit. However, differences in antiplatelet profiles 
may potentially prompt further investigations of the clinical implication of this difference by means 
of a larger scale clinical study.   
Potential Financial Risks or Benefits 
 
None 
Conflict of Interest 
Dr. Angiolillo is a consultant for Merck, the maker of vorapaxar. 


19 
 
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