© 2000 American Heart Association, Inc.
Thrombosis |
Comparative In Vitro Efficacy of Different Platelet Glycoprotein IIb/IIIa Antagonists on Platelet-Mediated Clot Strength Induced by Tissue Factor With Use of Thromboelastography
Differentiation Among Glycoprotein IIb/IIIa Antagonists
From DuPont Pharmaceuticals Co (S.A.M., M.S.F.), Wilmington, Del, and William Beaumont Hospital (S.K.), Royal Oak, Mich.
Correspondence to Shaker A. Mousa, PhD, FACC, DuPont Pharmaceuticals Co, 141 and Henry Clay Road, Exp. Station, E400/3470, Wilmington, DE 19880-0400. E-mail shaker.a.mousa{at}dupontpharma.com
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Abstract |
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Abstract—In the present study, the in vitro efficacy of different platelet glycoprotein IIb/IIIa (GPIIb/IIIa) antagonists on platelet-fibrin–mediated clot strength under shear was compared with the antiaggregatory efficacy by using tissue factor (TF) thromboelastography (TEG). The ability of platelets to augment the elastic properties of blood clots under shear conditions was measured by computerized TEG under conditions of maximal platelet activation accelerated by recombinant TF. Under these conditions, platelets significantly enhance clot strength 8-fold (relative to platelet-free fibrin clots). This effect was inhibited to a different extent by various platelet GPIIb/IIIa receptor antagonists; this inhibition appears to be dependent on the transmission of platelet contractile force to fibrin via the GPIIb/IIIa receptors. The GPIIb/IIIa antagonists with high binding affinity for resting and activated platelets and slow platelet dissociation rates (class I) but not those with fast platelet dissociation rates (class II) demonstrated potent and comparable inhibition of platelet aggregation and TF-TEG clot strength. Platelet GPIIb/IIIa antagonists of class I, such as XV459 (free-acid form of roxifiban), DMP802, XV454, and c7E3, demonstrated comparable inhibitory dose responses of TF-TEG clot strength and platelet aggregation, with an IC50 of 50 to 70 nmol/L. In contrast, platelet GPIIb/IIIa antagonists from class II, with comparable antiaggregatory efficacy, such as DMP728, YZ202 (free-acid form of orbofiban), YZ211 (free-acid form of sibrafiban), YZ751, and other antagonists, have a much lower efficacy in altering the strength of TF-mediated clot formation (IC50 >1.0 µmol/L). These data suggest differential efficacy among different GPIIb/IIIa antagonists in inhibiting platelet-fibrin clot retraction despite of equivalent antiaggregatory potency.
Key Words: platelet glycoprotein IIb/IIIa antagonists • binding kinetics • integrins • tissue factor • thromboelastography
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Introduction |
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Intravascular thrombosis is one of the most frequent pathological events and a major cause of morbidity and mortality in western civilization. Critical steps in the development of acute coronary syndromes are the disruption, rupture, or erosion of atherosclerotic plaque and the exposure of surface tissue factor (TF) with the formation of either partially or completely occlusive thrombus under shear.1 2 3 Factors that stimulate thrombosis include vascular damage, stimulation of platelets, and activation of the coagulation cascade. Platelet adhesion to exposed subendothelial surfaces of injured vessels, with subsequent activation, and the resulting platelet-rich clot formation have been shown to be associated with various pathological conditions, including cardiovascular and cerebrovascular thromboembolic disorders, such as unstable angina, myocardial infarction, transient ischemic attack, stroke, and atherosclerosis.3 4
Platelet-fibrinogen interaction is a key step in the pathogenesis of coronary artery thrombosis.1 2 3 4 The clinical benefit of aspirin and the more dramatic antithrombotic effect of intravenous antagonists of the platelet surface glycoprotein IIb/IIIa (GPIIb/IIIa) receptor underscore the importance of platelet involvement in acute coronary ischemia.5 6 7 8 Platelet GPIIb/IIIa blockade with c7E3 (ReoPro) reduces myocardial infarction and death associated with unstable angina and percutaneous transluminal coronary angioplasty.8 Such therapy, however, may be associated with a risk of hemorrhagic complications. There is considerable person-to-person variability in the number of GPIIb/IIIa receptors and their ligand binding functions; in patients with coronary artery disease, enhanced platelet GPIIb/IIIa receptor expression may be a marker for increased thrombotic risk. Furthermore, variable inhibition of GPIIb/IIIa function, which is partly due to differences in platelet count, may occur after the administration of weight-adjusted c7E3. Although conventional light transmittance platelet aggregometry has been used to measure the degree of ex vivo platelet aggregation inhibition in early clinical studies and dose-finding studies, its routine clinical use for dosing in individual patients has not been feasible.9
Activated platelets exert contractile force; when allowed to interact with polymerizing fibrin, tensile strength is significantly increased.10 11 12 This physical property of activated platelets and fibrin can be measured by computerized thromboelastography (TEG).10 13 In a recent report, the active form of roxifiban, XV459, demonstrated antiplatelet efficacy and specificity to the platelet GPIIb/IIIa receptors; antiaggregatory efficacy depends on the degree of receptor occupancy, the type of agonist used, and its concentration.14 TEG has great advantages over other techniques in measuring clot strength in whole blood (WB) under shear. However, its value in relation to the prediction of clinical outcome still remains to be determined in clinical trials.
The present study was undertaken to characterize the efficacy of comparable antiaggregatory platelet GPIIb/IIIa antagonists with different platelet GPIIb/IIIa binding kinetics on platelet-fibrin clot retraction by use of TF-TEG. Those GPIIb/IIIa antagonists can be classified on the basis of their platelet binding kinetics into 2 classes. Class I includes GPIIb/IIIa antagonists with relatively high and comparable binding equilibrium affinity for resting and activated platelets and slow platelet dissociation rates. In contrast, class II GPIIb/IIIa antagonists include compounds with relatively lower affinity for resting platelets and fast platelet dissociation rates. Examples of class I include roxifiban (XV459), DMP802, XV454 (nonpeptide), and c7E3 (monoclonal antibody), and class II includes DMP728 (cyclic peptide), orbofiban (YZ202), YZ211 (sibrafiban), and YZ751 (nonpeptide).
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Methods |
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Thromboelastography
TEG has been used in various hospital settings since its development by Hartert15 in 1948. The principle of TEG is based on the measurement of the physical viscoelastic characteristics of blood clots. Clot formation was monitored at 37°C in an oscillating plastic cylindrical cuvette ("cup") and a coaxially suspended stationary piston ("pin") with a 1-mm clearance between the surfaces by use of a computerized Thrombelastograph (TEG model 3000, Haemoscope). The cup oscillates 4°45' (1/12 radian) in either direction every 4.5 seconds, with a 1-second mid-cycle stationary period, resulting in a frequency of 0.1 Hz and a maximal shear rate of 0.1 per second. The pin is suspended by a torsion wire that acts as a torque transducer. With clot formation, fibrin fibrils physically link the cup to the pin, and the rotation of the cup, as affected by the viscoelasticity of the clot (transmitted to the pin), is displayed online by using an IBM-compatible personal computer and customized software (Haemoscope Corp). The torque experienced by the pin (relative to the oscillation of the cup) is plotted as a function of time (Figure 1
).
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TEG assesses coagulation by measuring various parameters,
such as the time latency for the initiation of the clot, the
time to initiation of a fixed clot firmness of 
20-mm amplitude, the
kinetics of clot development as measured by the angle (
), and the
maximum amplitude (MA) of the clot. The parameter A
measures the width of the tracing at any point of the MA. Amplitude A
(in millimeters) is a function of clot strength or elasticity. The
amplitude on the TEG tracing is a measure of the rigidity of the clot;
the peak strength or the shear elastic modulus attained by the clot is
a function of clot rigidity and can be calculated from the MA of the
TEG tracing.
The following parameters were measured from the TEG tracing
(Figure 1
): (1) The reaction time (gelation time)
represents the latent period before the establishment of a 3D
fibrin gel network (with measurable rigidity of 2-mm amplitude). (2)
MA (in millimeters) is the peak rigidity manifested by the clot. (3)
Shear elastic modulus or clot strength (G, in dynes per square
centimeter) is defined as G=(5000A)/(100-A).
Blood clot firmness is an important parameter for in vivo
thrombosis and hemostasis because the clot must stand the shear stress
at the site of vascular injury. TEG can assess the efficacy of
different pharmacological interventions on various factors (coagulation
activation, thrombin generation, fibrin formation, platelet
activation, platelet-fibrin interaction, and fibrin polymerization)
involved in clot formation and retraction. The effect of TF (25 ng) on
the different clot parameters measured by computerized TEG
in human WB is shown in Table 1.
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Blood Sampling
Blood was drawn from consenting volunteers under a protocol
approved by the Human Investigations Committee of William Beaumont
Hospital. By use of the 2-syringe method, samples were drawn through a
21-gauge butterfly needle, and the initial 3 mL blood was discarded. WB
was collected into siliconized Vacutainer tubes (Becton Dickinson)
containing 3.8% trisodium citrate such that a ratio of citrate WB of
1:9 (vol/vol) was maintained. TEG was performed within 3 hours of blood
collection.
Platelet Contribution to Clot Strength
To assess the effect of TF on clot modification, peak clot
strength was measured with and without the addition of TF (25 ng) in
paired samples of WB and platelet-rich plasma (PRP). To document
the contribution of activated platelets to the elastic
modulus of fibrin clots, the effect of platelet number was measured
by serially diluting PRP with platelet-poor plasma (PPP). The
platelet count of each dilution was measured before performing TEG.
TF-triggered TEG was performed with increasing concentrations (0,
0.625, 1.25, 2.5, 5, and 10 µmol/L) along with dimethyl
sulfoxide added to the TEG cups such that the final dimethyl sulfoxide
concentration in each TEG sample was 0.3% (vol/vol). The effect of
GPIIb/IIIa blockade on clot strength was studied by adding increasing
concentrations of c7E3 Fab (abciximab, Centocor), cyclic peptide, and
peptidomimetic and nonpeptide GPIIb/IIIa antagonists
(DuPont) to the TEG cup along with CaCl2 and TF.
The TEG MA for platelets was calculated by subtracting the MA from
a PPP sample determined in 1 TEG well from the MA of WB run
simultaneously in the second TEG well.
Platelet Aggregation
Agonist-induced platelet aggregation was measured as change
in percent light transmission of PRP (platelet count
2x105 per µL). For studying the effect of
GPIIb/IIIa antagonists on platelet aggregation,
increasing concentrations were added to PRP for 5 minutes, after which
10 µmol/L TRAP1–6 (SFLLRN, Peninsula
Labs) was added. The aggregation response was measured as the maximum
response of the increase in light transmission induced by TRAP by using
PPP to establish 100% light transmission.
GPIIb/IIIa Antagonist Binding Affinity to
Activated and Resting Human Platelets
This assay was used to determine the saturable binding of a
compound to platelets by using PRP. Citrated WB (5 mL draw,
Vacutainer tubes containing 3.2% sodium citrate) was collected from
healthy, aspirin-free, human subjects and centrifuged for 10
minutes at 150g at 22°C with a Sorvall RT6000 Table Top
Centrifuge (DuPont). PRP was removed and pooled, and
platelets were counted with a Coulter T540 Hematology
Analyzer. Saline (810 µL, 0.9% USP [Baxter], containing
1 mmol/L calcium chloride) and 40 µL of radiolabeled
[3H]-XV459,
[3H]-XV454, 3H-DMP802,
3H-DMP728, and
[125I]-c7E3 at different concentrations were
added to the assay tubes, followed by 50 µL of PRP (2x10
platelets per milliliter). Samples were incubated for 10 minutes at
22°C. For platelet activation, 100 µL of ADP (10 µmol/L
final concentration) was added to all samples, followed by incubation
for 10 minutes at 22°C (pH of 7.5). Platelets were harvested
through Whatman 934AH GFB filters that had been presoaked (30 minutes)
in 0.2% polyethylenimine. Filters were washed quickly 3 times with 5
mL of ice-cold saline, removed, and placed into scintillation vials.
Six milliliters of DuPont NEN formula 989 per vial was added. The vials
were allowed to stand for 60 minutes, and then they were shaken and
counted by a liquid scintillation counter. Equilibrium binding affinity
for the different radiolabeled GPIIb/IIIa antagonists to
activated and resting human platelets was calculated by
using a Scatchard plot.
Dissociation Rates
Citrated WB (5 mL draw, Vacutainer tubes, containing 3.2%
sodium citrate) was collected from healthy, aspirin-free, human
subjects. Blood samples were divided to be used as WB or to be
centrifuged for 10 minutes (150g). The resulting PRP
was removed, and platelet counts were determined to normalize the
radiolabeled platelets. Designated individual tubes of WB were
treated for 60 minutes, with or without activation (ADP, 100
µmol/L), with 0.04 µmol/L of 3H-XV459.
To help ensure sample viability during this period, the blood was
maintained on a rocker. After this 60-minute incubation period, the
tubes were centrifuged for 10 minutes (150g). The
resulting 3H-radioligand/PRP was
carefully removed and centrifuged an additional 10 minutes
(250g). The resulting PPP was removed, and the
platelet pellet was resuspended
(1.6x108/mL) in fresh PPP. This suspension
(500 µL) was transferred to wells of a 24-well plate (blocked with
5% BSA). To initiate dissociation, 100 µmol/L nonradiolabeled
ligand was added to the wells. At designated time points (0, 2, 15, 30,
60, 90, and 120 minutes), the [3H]- or
[125I]-bound (CPM) GPIIb/IIIa
antagonist to PRP was removed from the wells and
centrifuged for 2 minutes (10 000g). The resulting
platelet pellet was counted with a liquid scintillation counter.
Counts per minute recovered are compared with the control (t=0)
value and are presented as percent bound per
0.8x108 platelets. The dissociation rate was
assessed for the different intervals for the determination of the
half-time (minutes) for the dissociation of platelet-bound
radiolabeled ligand.
Statistical Analysis
Data are expressed as mean±SEM. Data were analyzed by
either paired or group analysis with use of Student
t test or ANOVA when applicable. Differences were considered
significant at P<0.05.
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Results |
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Platelet GPIIb/IIIa Binding Kinetics
Table 2
shows the binding affinity
to activated versus resting platelets. XV459 binds with
high affinity to resting and activated human platelets with
Kd values of 2.52±0.98 and 0.80±0.0.16
nmol/L, respectively. DMP802 and XV454 demonstrated high affinity to
either activated or resting human platelets with a
Kd of 0.2 to 0.50 nmol/L. Similarly, the
chimeric 7E3 demonstrated a comparable affinity for resting and
activated human platelets with
Kd values of 9.1±0.5 and 9.5±0.6 nmol/L,
respectively (Table 2). In contrast, DMP728 binds with high
affinity to activated human platelets with a
Kd of 0.32 and to resting human
platelets with a Kd of 36.0 nmol/L
(Table 2). DMP728, YZ751, YZ211 (sibrafiban), and YZ202
(orbofiban) from class II showed relatively faster dissociation rates
(half-time of 3 to 10 seconds) from resting human platelets.
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Effect of TF on Strength of WB Clot
To study the interaction of platelets with the fibrin network
induced by TF, clot strength was measured with and without maximal TF
(25 ng) activation in WB. TF activation reduced the time latency for
the initiation of the clot and triggered acceleration of clotting in
the presence of PRP but did not augment the clot strength (in dynes per
square centimeter) in the presence of PPP (Figure 2). Both roxifiban and c7E3 blocked
platelet-mediated TF augmentation of clot strength (Figure 2). The TEG MA for platelets was calculated by subtracting
the MA from a PPP sample determined in 1 TEG well from the MA of WB run
simultaneously in the second TEG well. The addition of
abciximab or roxifiban at 100 nmol/L each resulted in maximal
inhibition of platelet aggregation, platelet contractile force,
and platelet MA. Platelet contractile force and MA were
significantly more responsive than was WB MA to the effect of abciximab
and roxifiban, along with its reversal with the addition of fresh
PRP.
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The effect of TF (25 ng) on the dynamics of clot formation in human WB
assessed by use of TEG is shown in Figure 3 (top tracing), and the effect of c7E3
(abciximab) on TF (25 ng)–induced clot formation in human WB assessed
by use of TEG is shown in Figure 3 (middle tracing).
Additionally, a comparable efficacy for c7E3 (class I) in inhibiting
platelet aggregation induced by TRAP and clot formation induced by
TF is shown in Figure 3 (bottom).
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A representative tracing of the effect of class I
versus class II platelet GPIIb/IIIa antagonists on clot
retraction mediated by TF-TEG is shown (Figure 4).
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Effect of Different GPIIb/IIIa Receptor Antagonists on
TF-TEG Clot Strength Compared With Turbidometric Platelet
Aggregation
Increasing concentrations of GPIIb/IIIa antagonists
impaired the rate of increase in shear elastic modulus force (developed
without prolonging the time latency for the initiation of the clot by
TF-activated WB clots) to a different degree depending on
binding kinetics of the GPIIb/IIIa antagonist. The degree
of platelet inhibition by c7E3, roxifiban, DMP802, and XV454 was
similar whether measured by TF-TEG or TRAP-induced aggregation (Table 3). In contrast, DMP728, orbofiban
(YZ202), YZ211 (sibrafiban), and YZ751, which are lower affinity
antagonists for resting platelets with relatively
faster platelet dissociation rates (3 to 10 seconds), demonstrated
lower affinity in altering clot structure compared with their potent
antiaggregatory efficacy. LM609 (a monoclonal antibody) and XT199,
small molecule nonpeptide antagonists for
vß3 integrin, were
without any effect on either platelet aggregation or
TF-TEG–mediated clot strength (Table 3). Thus, under the
conditions of our TEG assay, c7E3, DMP802, roxifiban (XV459), and XV454
blocked the contribution of platelets to the physical properties of
the fibrin clot (Figure 5).
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TEG has been used to monitor hemostatic disorders in cardiovascular surgery.16 17 18 TEG has been used in cardiopulmonary surgery to predict bleeding and monitor the effectiveness of blood transfusions.19 TEG was recently modified and computerized to provide a greater level of precision.13 In the present study, the utility of TEG in determining the efficacy of different platelet GPIIb/IIIa antagonists was assessed. The final step in platelet aggregate formation is mediated exclusively by the GPIIb/IIIa receptor. Various large-scale phase III clinical trials have illustrated the usefulness of ReoPro in the treatment of coronary interventions.20 21 22 Additionally, other selective GPIIb/IIIa antagonists, including integrilin, tirofiban (Aggrastat), and lamifiban, are in advanced stages of clinical development and are aimed primarily for intravenous use in the treatment and prevention of acute ischemic heart diseases.23 24 25 The Integrilin to Minimize Platelet Aggregation and Coronary Thrombosis-II (IMPACT II) and Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) trials with integrilin and the Randomized Efficacy Study of Tirofiban for Outcomes and Restenosis (RESTORE) trial with tirofiban (Aggrastat) as well as other trials have demonstrated significant clinical benefits in acute ischemic syndromes. Clinical studies with orally active GPIIb/IIIa antagonists, including xemilofiban, orbofiban (YZ202), lotrafiban, and lefradafiban, have demonstrated oral antiplatelet activity in humans when administered 2 to 3 times per day.26 27 28 29 30 Roxifiban (DMP754) and its active free-acid form, XV459, have distinct platelet GPIIb/IIIa binding characteristics along with a potent in vitro antiplatelet efficacy regardless of the activator or the anticoagulant (citrate versus heparin).31 32 Recently, clinical development programs involving xemilofiban, orbofiban (YZ202), and sibrafiban (YZ211) were halted because of lack of clinical benefits.
Clot formation is initiated by thrombin-induced cleavage of
fibrinopeptide A from fibrinogen. The resultant fibrin
monomers spontaneously polymerize to form fibril strands that undergo
linear extension, branching, and lateral association, leading to the
formation of a 3D network of fibrin fibers.10 11 12 A unique
property of network structures is that they behave as rigid elastic
solids, capable of resisting deforming shear stress. This resistance to
deformation can be measured by elastic modulus, an index of clot
strength. Unlike conventional coagulation tests (like the prothrombin
time and partial thromboplastin time) that are based only on the time
to the onset of clot formation, TEG allows acquisition of quantitative
information, allowing measurement of the maximal strength attained by
clots. Via the GPIIb/IIIa receptor, platelets bind fibrin(ogen) and
modulate the viscoelastic properties of clots. Our results have
demonstrated that clot strength in TF-TEG is clearly a function of
platelet concentration and that platelets augment clot strength
8-fold under shear. Different platelet GPIIb/IIIa
antagonists (class I versus class II) behaved with distinct
efficacy in inhibiting platelet-fibrin–mediated clot strength by
use of TF-TEG under shear.
The addition of abciximab or roxifiban at 100 nmol/L each resulted in maximal inhibition of platelet aggregation, platelet contractile force, and platelet MA. Platelet contractile force and MA were significantly more responsive than WB MA to the effects of abciximab and roxifiban, along with its reversal with the addition of fresh PRP. This is in agreement with an earlier report on the effects of abciximab on platelet contractile force by use of TEG.33
TEG is being used in monitoring platelet function and risk of hemorrhage during and after cardiopulmonary bypass surgery.16 17 18 19 TEG has been shown to be a reliable coagulation monitoring system that can guide blood product transfusion in cardiac surgery. Additionally, our present study suggests the potential value of TEG in differentiating among different platelet GPIIb/IIIa antagonists.
In conclusion, a comparable inhibitory dose response for GPIIb/IIIa (class I) antagonists with high affinity for resting platelets and relatively slow dissociation rates (c7E3, XV459, XV454, DMP802, and others) in inhibiting clot strength (TF-TEG) and TRAP-induced platelet aggregation has been demonstrated. In contrast, GPIIb/IIIa (class II) antagonists with relatively lower affinity for resting human platelets along with relatively fast platelet dissociation rates from human platelets, such as DMP728, YZ202, YZ751, and others, have a much lower efficacy in inhibiting clot strength with the use of TF-TEG under shear. These data suggest that not all GPIIb/IIIa antagonists are equal with regard to their efficacy in inhibiting platelet-fibrin clot under shear, which might explain their potential differences in attaining different levels of clinical benefits.
Received May 26, 1999; accepted November 19, 1999.
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References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Fuster V, Steele PM, Chesebro JH. Role of platelets and thrombosis in coronary atherosclerotic disease and sudden death. J Am Coll Cardiol. 1985;5:175B–184B.
2. Hamm CW, Bliefield W, Kupper W, Lorenz RL, Weber PC, Wober W. Biochemical evidence of platelet activation in patients with persistent unstable angina. J Am Coll Cardiol. 1987;10:998–1004.[Abstract]
3.
Willerson JT, Golino P, Eidt J, Campbell WB, Buja LM.
Specific platelet mediators and unstable coronary artery
lesions: experimental evidence and potential clinical implications.
Circulation. 1989;80:198–205.
4.
Davies MJ, Thomas AC. Plaque fissuring-the cause
of acute myocardial infarction, sudden ischemic death, and
crescendo angina. Br Heart J. 1985;53:363–373.
5. Ashby B, Daniel JL, Smith JB. Mechanisms of platelet activation and inhibition. Hematol Oncol Clin North Am.. 1990;4:1–26.[Medline] [Order article via Infotrieve]
6.
Pytela R, Pierschbacher MS, Ginsberg MH, Plow EF,
Ruoslahti E. Platelet membrane glycoprotein IIb/IIIa:
member of a family of RGD specific adhesion receptors.
Science. 1986;231:1559–1562.
7.
Andrieux A, Hudry-Clergion G, Ryckewaert J-J, Chapel
A, Ginsberg MH, Plow EF, Margueire G. Amino acid sequences in
fibrinogen mediating its interaction with its platelet receptor,
GPIIb/IIIa. J Biol Chem. 1989;264:9258–9264.
8. Topol EJ, Plow EF. Clinical trials of platelet receptor inhibitors. Thromb Haemost. 1993;70:94–98.[Medline] [Order article via Infotrieve]
9. Nicholson NS, Panzer-Knodle SG, Haas NF, Taite BB, Szalony JA, Page JD, Feigen LP, Lansky DM, Salyers AK. Assessment of platelet function assays. Am Heart J. 1998;135(pt 2, suppl)S170–S178.
10.
Cohen K, Gerrard JM, White JG. Ultrastructure of clots
during isometric contraction. J Cell Biol. 1982;93:775–483.
11.
Brasten JV, Jerome WG, Hantgan RR. Uncoupling fibrin
from integrin receptors hastens fibrinolysis at the
platelet-fibrin interface. Blood. 1994;83:982–990.
12.
Hantgan RR, Taylor RG, Lewis JC. Platelets interact
with fibrin only after activation. Blood. 1985;65:1299–1308.
13. Reid TJ, Greilich PE, Carr ME, Alving BM. Quantitative clot retraction: a method assessing the function of fresh and stored platelets and GPIIb/IIIa receptors. Blood. 1994;84:1839–1847.
14. Mousa SA, Forsythe M, Lorelli W, Bozarth J, Xue C-B, Wityak J, Sielecki TM, Olson R, Degrado W, Kapil R, Hussain M, Wexler R, Thoolen M, Reilly TM. Novel nonpeptide antiplatelet GPIIb/IIIa receptor antagonist, DMP754: receptor binding affinity and specificity. Coron Artery Dis. 1996;7:767–774[Medline] [Order article via Infotrieve]
15. Hartert H. Blutgerinnungstudien mit der Thromboelastograpie, einem ueuen Untersuchungsverfahren. Klin Wochenschr. 1948;26:577–583.[Medline] [Order article via Infotrieve]
16. Essell JH, Martin TJ, Salinas J, Thompson JM, Smith VC. Comparison of thromboelastography to bleeding time and standard coagulation tests in patients after cardiopulmonary bypass. J Cardiothorac Vasc Anesth. 1993;7:410–415.[Medline] [Order article via Infotrieve]
17. Muller N, Popov-Cenic S, Buttner W, Kladetsky RG, Egil H. Studies of fibrinolytic and coagulation factors during open heart surgery, II: postoperative tendency and changes in the coagulation system. Thromb Res. 1975;7:589–598.[Medline] [Order article via Infotrieve]
18. Spiess BD, Tuman KJ, McCarthy RJ, DeLaria GA, Schillo R, Ivankovich AD. Thromboelastography as an indicator of post-cardiopulmonary bypass coagulopathies. J Clin Monit. 1987;3:25–30.[Medline] [Order article via Infotrieve]
19. Spiess BD, Gillies BS, Chandler W, Verrier E. Changes in transfusion therapy and reexploration rate after institution of a blood management program in cardiac surgical patients. J Cardiothorac Vasc Anesth. 1995;9:168–173.[Medline] [Order article via Infotrieve]
20.
The EPIC Investigators. Use of a monoclonal antibody
directed against the glycoprotein IIb/IIIa receptor in
high-risk coronary angioplasty. N Engl J
Med. 1994;330:956–961.
21. Kleiman NS, Ohman EM, Califf RM, George BS, Kereiakes D, Aguirre FV, Weisman H, Schaible T, Topol EJ. Profound inhibition of platelet aggregation with monoclonal antibody c7E3 after thrombolytic therapy: results of the thrombolysis and angioplasty in myocardial infarction (TAMI) 8 pilot study. J Am Coll Cardiol. 1993;22:381–389.[Abstract]
22. Topol EJ, Califf RM, Weisman HF, Ellis SG, Tcheng JE, Worley S, Ivanhoe R, George BS, Fintal D, Weston M, Sigmon K, Anderson KM, Lee KL, Willerson JT, EPIC Investigators. Randomized trial of coronary intervention with antibody against platelet GPIIb/IIIa integrin for reduction of clinical restenosis: results at six months. Lancet. 1994;343:881–886.[Medline] [Order article via Infotrieve]
23.
PRISM-PLUS Study Investigators. Inhibition of the
platelet glycoprotein IIb/IIIa receptor with tirofiban
in unstable angina and non-Q-wave myocardial infarction: platelet
receptor inhibition in ischemic syndrome management in patients
limited by unstable signs and symptoms. N Engl J
Med. 1998;338:1488–1497.
24.
Tcheng JE, Harrington RA, Kottke-Marchant K, Kleiman
NS, Ellis SG, Kereiakes DJ, Mick MJ, Navetta FI, Smith JE, Worley SJ,
Miller JA, Joseph DM, Sigmon KN, Kitt MM, du Mee CP, Califf RM, Topol
EJ. Multicenter, randomized, double-blind, placebo-controlled trial of
the platelet integrin glycoprotein IIb/IIIa blocker,
integrilin in elective coronary intervention: IMPACT
investigators. Circulation. 1995;91:2151–2157.
25. Théroux P, Kouz S, Knudtson ML, et al. A randomized double-blind controlled trial with the non-peptide platelet GPIIb/IIIa antagonist RO 44–9883 in unstable angina. Circulation. 1994;90(suppl I):I-232. Abstract.
26.
Simpfendorfer C, Kottke-Marchant K, Lowrie M, Anders
RJ, Burns DM, Miller DP, Cove CS, DeFranco AC, Ellis SG, Moliterno DJ,
Raymond RE, Sutton JM, Topol EJ. First chronic platelet
glycoprotein IIb/IIIa integrin blockade: a randomized,
placebo-controlled pilot study of xemilofiban in unstable angina with
percutaneous coronary interventions.
Circulation. 1997;96:76–81.
27.
Muller TH, Weisenberger H, Brickl R, Narjes H,
Himmelsbach F, Krause J. Profound and sustained inhibition of
platelet aggregation by fradafiban, nonpeptide platelet
glycoprotein IIb/IIIa antagonist, and its
orally active prodrug, lefradafiban, in men. Circulation. 1997;96:1130–1138.
28.
Cannon CP, McCabe CH, Borzak S, Henry TD, Tischler MD,
Mueller HS, Feldman R, Palmeri ST, Ault K, Hamilton SA, et al.
Randomized trial of an oral platelet glycoprotein
IIb/IIIa antagonist, sibrafiban, in patients after an acute
coronary syndrome: results of the TIMI 12 trial:
thrombolysis in myocardial infarction.
Circulation. 1998;97:340–349.
29. Harrington RA, Graffagnino C, Armstrong PW, Joseph D, Card TL, et al. Dose-finding and tolerability of a new oral platelet GPIIb/IIIa inhibitor, SB 214857, in patients with coronary artery and cerebrovascular disease: the APLAUD results. Circulation. 1998;98(suppl I):I-251. Abstract.
30. Mousa SA, Topol EJ. Novel antiplatelet therapies: recent advances in the development of platelet GPIIb/IIIa receptor antagonists. In: Serruys PW, Holmes D, eds. Current Review of Interventional Cardiology. 3rd ed. Philadelphia, Pa: Current Medicine; 1997;13:114–129.
31.
Mousa SA, Bozarth J, Lorelli W, Forsythe M, Thoolen M,
Slee A, Reilly T, Friedman P. Discovery of novel orally active
non-peptide platelet GPIIb/IIIa receptor antagonist,
DMP754: comparative platelet binding profiles with c7E3.
J Pharmacol Exp Ther. 1998;286:1277–1284.
32. Mousa SA, Wityak J. Orally active isoxazoline GPIIb/IIIa antagonists. Cardiovasc Drug Rev. 1998;16:48–61.
33. Greilich PE, Alving BM, Longnecker D, Carr ME Jr, Whitten CW, Chang AS, Reid TJ. Near-site monitoring of the antiplatelet drug abciximab using the Hemodyne analyzer and modified thrombelastograph. J Cardiothorac Vasc Anesth. 1999;13:58–64.[Medline] [Order article via Infotrieve]
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