Switching from Clopidogrel to Prasugrel to Protect Early Invasivetreatment in Acute Coronary

SWITCHing from clOpidogrel to prasugrel to protect early inVasivetrEatment in acute coRonary syndromes: results of the SWITCH OVER trial

F. Ottani et al.

SUPPLEMENTAL MATERIAL

Expandedmethods

Study population

The study population consisted of “naïve of clopidogrel” NSTE-ACS patientsadmitted to the hospital because of chest pain episodes within 24 hours prior toadmission along with the presence of ST- segment shifts or T wave inversion and/orelevation of cardiac markers of necrosis (cardiac troponin T for the present study).Written informed consent was obtained by the attending physician before anystudy procedures are started.

Inclusioncriteria

1)Signedwritteninformedconsent

2)Age of 18 year or older

3)Episode of typical chest pain lasting >10 min occurred withinthe prior 24 hours along with at least one of the following:

a)transient ST- segment elevation ≥1 mm in 2 adjacentECG leads,

b)ST-segment depression ≥0.5 mm in 2 adjacent ECG leads,

c)and/or the presence of T-wave inversion (≥ 3 mm depth),

d)elevation of biomarker of cardiac necrosis (cardiactroponin T)

Exclusioncriteria

1)Patients with a previous history of TIA/stroke (prasugrelcontraindicated)

2)Priorchronicclopidogrel use

3)Planned “upstream treatment” with GPI

4)Need for chronicoralanticoagulation

5)Recentfibrinolyticadministration

6)Increasedbleedingrisk or anaemia

7)Active internal bleeding or history of bleeding diathesis

8)Bodyweight ≤ 60 kg

9)Age ≥75 years

10)Hypersensitivity, intolerance of or allergy to clopidogrel andprasugrel or their excipients

11)Known severe hepatic dysfunction (Child-Pugh C)

12)Women who are known to be pregnant or are breast-feeding

Participation in other research

Patients included in the study were not authorized to participate in another interventional research during their inclusion period to avoid interference of another investigational product.

Study discontinuation

A patient was considered discontinued from the study only ifhe or she withdraws the consent at any time during the study period,he or she is lost to follow-up after exhausting all means of contact.

In the last 2 cases, the status of the patient at the last visit or contact was used for the final analysis. Vital status through public records can be assessed by the local clinical investigator in case of failure of all other ways of contact.

Concomitant treatments

Associated treatments (anti-thrombotic and anti-ischemic agents, statins, etc.) reflected the practices of the study sites and complied with the European Society of Cardiology for the treatment of NSTE-ACS patients corresponding to the eligibility profile of the present study.

The use of GPI was allowed if refractory ischemia occurred during the course of PCI and was defined as the administration of GPI after the initiation of the procedure (defined as the time when the wire passed the lesion) for the management of any one of the following complications: decrement in TIMI flow grade, dissection with decreased flow, distal embolization, side branch closure, abrupt closure of the culprit vessel, clinical instability believed to be due to coronary ischemia and/or thrombotic complications, or prolonged ischemia (e.g. ischemic symptoms or ST-segment changes that develop during the procedures).

Coronary angiography / angioplasty

Coronary angiography was performed using a standard catheterization technique,

via radial (preferred) or femoral approach. Coronary angiography allowed identification of the culprit coronary artery. If thecoronary anatomy was suitable for percutaneous revascularization, the patient was randomized after placing the guiding catheter in the culprit artery. Coronary angioplasty with or without stenting was performed according to the usual procedures utilized by the cardiologist in charge. Use of thrombus aspirationmethods as well as use of bare-metal or drug-eluting stents was left to thediscretion of the attending physician.

Blood sampling

A venous blood sample anticoagulated with sodium citrate 0.109 mol/L (ratio 9:1) was taken from each patient at each time points of Coronary Care Unit admissionafter discarding the first 3-5 ml immediately before the diagnostic coronary catheterization (baseline) and 0.5 (+15min), 1(+15 min), 2(+15 min), 4(+15 min), 6(+15 min), 24(+1 hour), and 48 (+1 hour) hours after randomization.A total of 8blood samples for each enrolled patient were collected.

Measurements ofresidual platelet reactivity

Vasodilator-stimulated phosphoprotein (VASP) phosphorylation

VASP phosphorylation analyses were performed within 48 hours from blood collection, using Platelet P2Y12 VASP assay (BiocytexInc, DiagnosticaStago, Asnières, France) according to the manufacturer’s instructions. Briefly, blood samples were incubated with PGE1 alone or in combination with ADP, fixed, permeabilized, and then labelled with a specific primary monoclonal antibody, followed by a secondary fluorescein isothiocyanate-conjugated polyclonal goat antimouse Ig antibody. Analyses were performed using a FC 500 flow cytometer (Beckman Coulter, Milano, IT).

PGE1 increases VASP-P levels by stimulation of adenylate cyclase, while the addition of ADP through the interaction with P2Y12 receptor reduces VASP-P levels of PGE1-stimulated platelets.

The degree of residual P2Y12 receptor activity is proportional to the platelet reactivity index (PRI), calculated from the median fluorescence intensity (MFI), reflecting VASP phosphorylation of samples incubated with PGE1 or PGE1 plus ADP, according to the formula: PRI = [MFI(PGE1) –MFI(PGE1+ADP)]/ MFI(PGE1) x 100.

The Verify-Now system (Accumetrics, San Diego, California, USA), a turbidimetry-basedoptical detection device that measures platelet inducedagglutination in whole blood in a systemcontaining fibrinogen-coated beads. By using the cartridge of Verify-Now P2Y12 assay, there is a channel able to measure specific inhibition of the ADP P2Y12receptor. This channel contains a mix of ADP andprostaglandin E1 to reduce non-specific contribution of the other ADP receptor, P2Y1.

The assay is based upon the ability of activated platelets to bind fibrinogen coated microparticleswhich aggregate in proportion to the number of GP IIb/IIIa receptors expressed. 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).

Study end-points and sample size calculation.

The primary study end point was the difference of PRI values between the highest prasugrel LD (G3) versus the control group (G4) at 4 hours after randomization, followed by hierarchical testing comparing PRI differences G4 versus G2 and G4 versus G1 at 4 hours after randomization.Secondary end points were: 1) PRI changes over time up to 48 hours across the 4 treatment groups; 2) PRU changes over time up to 48 hours across the 4 treatment groups; 3) the proportion of patients with HPR across the four groups at 4 hours. On the basis of previous studies(1,2), the following assumptions were made for the sample size calculation: i) on average, there would have been no significant differences among baseline values across the 4 groups after clopidogrelpretreatment, and ii) the highest prasugrel LD (G3) would result in a maximal absolute mean decrease of PRI 30% compared with controls (G4). Assuming a common standard deviation (SD) of 22%, the sample size had to be 21 patients in each study group, to have a 85% power at two-sided 0.05 alfa-level (nQuery advisor, version 6.0, Statistical Solutions) to detect the expected decrease in PRI. Taking into account possibledrop-outs and pre-analytical variables that may affect the integrity of the samples, the total number of the patients was increased to 100 (25 patients per group).

All patients were followed for 30 days to report for the clinical secondary endpoint, a composite of death, recurrent MI and urgent target vessel revascularization, and for safety, a composite of major and minor haemorrhagic events. All reported potential clinical events were adjudicated by 2 independent cardiologists blinded to the randomized treatment. Death was defined as mortality from all causes, and MI was classified according to the Third Universal Definition of Myocardial Infarction(3). High-sensitivity cardiac troponin levels were tested at hospital admission, 6, 12 hours thereafter to define the index event as myocardial infarction, and before and 24 hours after PCI to define post-procedural MI (i.e. type 4a MI). Bleeding was classified according to the Thrombolysis in Myocardial Infarction criteria (4).

Additionaltables

On-line table1. VASP PRI and VN-P2Y12 PRU at the different time pointsin the 4 treatment groups

Prasugrel
10 mg LD / Prasugrel
30 mg LD / Prasugrel
60 mg LD / Clopidogrel 75mg LD / Difference (%)
Clopidogrel – Prasugrel
VASP PRImean (SD) / Meandifference
(95% CI) / p-value
Baseline / 74 (11) / 69 (20) / 64 (21) / 73(22) / G1: -1 (-18/15)
G2: 4 (-12/20)
G3: 9 (-7/25) / 1.00
1.00
0.77
30 minafter R / 65 (22) / 61 (24) / 47 (27) / 71 (22) / G1: 6 (-13/26)
G2: 10 (-9/29)
G3: 24(4/44) / 1.00
0.95
0.009
1 hour after R / 61 (21) / 43 (27) / 14 (12) / 65 (21) / G1: 5(-14/23)
G2: 22(4/41)
G3: 51(32/70) / 1.00
0.009
0.0001
2 hours after R / 57 (22) / 32 (25) / 7 (12) / 63 (25) / G1: 6(-12/25)
G2: 31(13/49)
G3: 56(38/75) / 1.00
0.0001
0.0001
4 hours after R / 54 (24) / 19 (20) / 5 (7) / 63 (25) / G1: 9(-8/26)
G2: 43(27/60)
G3: 58(40/75) / 0.87
0.0001
0.0001
6 hours after R / 49 (24) / 19 (20) / 5 (6) / 62 (30) / G1: 13(-4/31)
G2: 43(27/60)
G3: 58(40/75) / 0.24
0.0001
0.0001
24 hours after R / 45 (22) / 17 (17) / 6 (7) / 60 (30) / G1: 15(-4/34)
G2: 43(23/62)
G3: 54(34/73) / 0.23
0.0001
0.0001
48 hours after R / 32 (19) / 13 (9) / 8 (6) / 63 (23) / G1: 31(14/47)
G2: 50(33/67)
G3: 56(39/73) / 0.001
0.0001
0.0001
VN-P2Y12 PRU, Mean (SD) / Meandifference
(95% CI) / p-value
Baseline / 184 (71) / 191 (88) / 184 (71) / 193 (73) / G1-6(-61/48)
G2:2 (-53/57)
G3:9(-46/64) / 1.00
1.00
1.00
30 minafter R / 204 (50) / 188 (84) / 160 (83) / 197 (88) / G1: -7(-66/52)
G2: 9(-50/69)
G3: 37(-22/96) / 1.00
1.00
0.59
1 hour after R / 172 (73) / 139 (100) / 70 (71) / 178 (73) / G1: 6(-56/67)
G2: 39(-24/101)
G3: 108(46/169 / 1.00
0.58
0.0001
2 hours after R / 146 (64) / 101 (84) / 41 (50) / 172 (90) / G1: 26(31/82)
G2: 71(14/129)
G3: 131(74/187) / 1.00
0.007
0.0001
4 hours after R / 129 (75) / 63 (56) / 30 (35) / 154 (84) / G1: 25(-25/75)
G2:92(41/143)
G3:124(73/175) / 1.00
0.0001
0.0001
6 hours after R / 96 (61) / 53 (57) / 14 (23) / 154 (85) / G1: 59(12/105)
G2: 102(53/150)
G3: 140(92/187) / 0.006
0.0001
0.0001
24 hours after R / 80 (65) / 44 (34) / 26 (23) / 155 (84) / G1: 74(29/120)
G2: 111(64/158)
G3: 129(83/175) / 0.0001
0.0001
0.000
48 hours after R / 67 (43) / 32 (31) / 32 (23) / 128 (75) / G1: 60(21/100)
G2: 96(57/135)
G3: 96 (55/137) / 0.001
0.001
0.001

Abbreviations: LD = loading dose; PRI = plateletreactivityindex (%); PRU = P2Y12reactionunit; R = randomization.

The mixed linear model using time as a fixedfactorwasused to evaluateall intra-groupcomparisons and the Scheffèapproachwasused to adjust for multiple comparisons.

On-line Table 2. Clinicaleventsatday 30
OverallPopulation / Prasugrel
LD 10 mg / Prasugrel
LD 30 mg / Prasugrel
LD 60 mg / Clopidogrel
Patients (n) / 99 / 25 / 25 / 25 / 24
Efficacy
Composite end-point* / 6 / 2 / 1 / 2 / 2
Death / 0 / 0 / 0 / 0 / 0
MI† / 6 / 2 / 1 / 1 / 2
Stroke / 0 / 0 / 0 / 0 / 0
TVR / 0 / 0 / 0 / 0 / 0
Safety
Composite end-point / 1 / 0 / 0 / 1 / 0
Major bleeding / 1 / 0 / 0 / 1 / 0
Minor bleeding / 0 / 0 / 0 / 0 / 0

* Composite of “all-cause” death, recurrent MI and TVR.†Codedaccording to Universal Definition of MyocardialInfarction (alleventsweretype 4a myocardialinfarction).

‡ Composite of TIMI major and minor bleeding

Abbreviations: LD= loading dose; MI = myocardialinfarction; TVR = urgent target vessel revascularization

On-line Table 3. Hemoglobin, plateletcount and serum creatinine across the 4 treatment groups
Prasugrel
10 mg LD / Prasugrel
30 mg LD / Prasugrel
60 mg LD / Clopidogrel
Patients (n) / 25 / 25 / 25 / 24
Hemoglobin
(gr/dL)
baseline / 15.1(1.4) / 14.4(1.7) / 14.4(1.3) / 14.8 (1.5)
24 h after PCI / 15.5(2.4) / 13.6(1.8) / 13.8(1.3) / 13.8(1.7)
at hospital discharge / 14.3(1.8) / 13.1(1.9) / 13.4(1.0) / 13.4(1.8)
Plateletcount
(109/L)
baseline / 221(48) / 235(90) / 216(61) / 210(56)
24 h after PCI / 202 (34) / 225(86) / 197(61) / 193(42)
at hospital discharge / 192(37) / 222(75) / 201(55) / 175(28)
Creatinine
(mg/dL)
baseline / 0.95(0.17) / 0.88 (0.32) / 0.88(0.15) / 0.88(0.24)
24 h after PCI / 0.93(0.16) / 1.3 (1.17) / 0.88(0.14) / 0.90(0.16)
at hospital discharge / 0.99(0.19) / 0.99(0.33) / 0.85(0.10) / 0.97(0.15)

Abbreviations: h = hours; LD = loading dose; n = number; PCI = percutaneouscoronaryinterventions

Additional figures

On-line figure 1

On-line figure 2

On-line figure 2 panel B

On-line figure 3

Additional figure legend

On-line figure 1

Patients flow diagram. Pharmacodynamicpopulationconsisted of allrandomizedpatientswhoweretested for plateletfunction. PD = pharmacodynamic.

On-line figure 2

Panel A

Individualvalues of plateletreactivityacross time points and comparison of high on treatment plateletreactivityrates. IndividualvaluesareP2Y12 reactionunits (PRU) at baseline and 30 minutes, 1, 2, 4, 6, 24, 48 hours afterrandomizationacross the 4 treatment groups. Superimposed bar chartsrepresentmean ± SD. The high on treatment plateletreactivitythresholds (PRI>50%) isshown by the dotted line.

Panel B

Time course of plateletinhibitionassessed by Verify_Nowacross the 4 treatment groups. Data are estimatedmarginalmeans± SE. The multivariate analysis of covariance P-valuerefers to the overalldifference in valuesacross the 4groupsadjusted for baseline values of plateletreactivityunits. P-values are provided for intergroupcomparison. Yellow line: G1 (prasugrel LD 10 mg); green line: G2 (prasugrel LD 30 mg); blue line: G3 (prasugrel LD 60 mg); purple line: G4 (clopidogrelLD 75 mg; controls).

Abbreviations: EEMs = EstimatedMarginalMeans; h = hours; R = Randomization; % = percent

On-line figure 3

Overall association between PRU from VN-P2Y12 and percent PRI from VASP after prasugrel LDs and clopidogrel at 4 hour time point (primary PD efficacy end-point of the trial). Correlation coefficient was calculated by the Pearson method.

Additional references

1.Michelson AD, Frelinger AL, 3rd, Braunwald E et al. Pharmacodynamic assessment of platelet inhibition by prasugrel vs. clopidogrel in the TRITON-TIMI 38 trial. Eur Heart J 2009;30:1753-63.

2.Payne CD, Li YG, Brandt JT et al. Switching directly to prasugrel from clopidogrel results in greater inhibition of platelet aggregation in aspirin-treated subjects. Platelets 2008;19:275-81.

3.Thygesen K, Alpert JS, Jaffe AS et al. Third universal definition of myocardial infarction. Eur Heart J 2012;33:2551-67.

4.Mehran R, Rao SV, Bhatt DL et al. Standardized bleeding definitions for cardiovascular clinical trials: a consensus report from the Bleeding Academic Research Consortium. Circulation 2011;123:2736-47.

1