Multi-year follow-up of abciximab therapy in three randomized, placebo-controlled trials of percutaneous coronary revascularization

Structure-guided design of pure orthosteric inhibitors of αIIbβ3 that prevent thrombosis but preserve hemostasis

A prevailing dogma is that inhibition of vascular thrombosis by antagonizing platelet integrin αIIbβ3 cannot be achieved without compromising hemostasis, thus causing serious bleeding and increased morbidity and mortality. It is speculated that these adverse outcomes result from drug-induced activating conformational changes in αIIbβ3 but direct proof is lacking. Here, we report the structure-guided design of peptide Hr10 and a modified form of the partial agonist drug tirofiban that act as "pure" antagonists of αIIbβ3, i.e., they no longer induce the conformational changes in αIIbβ3. Both agents inhibit human platelet aggregation but preserve clot retraction. Hr10 and modified tirofiban are as effective as partial agonist drugs in inhibiting vascular thrombosis in humanized mice, but neither causes serious bleeding, establishing a causal link between partial agonism and impaired hemostasis. Pure orthosteric inhibitors of αIIbβ3 may thus provide safer alternatives for human therapy, and valuable tools to probe structure-activity relationships in integrins.

A Review of Antiplatelet Activity of Traditional Medicinal Herbs on Integrative Medicine Studies

Thrombotic events mainly occurred by platelet activation and aggregation. The vascular occlusion causes serious disease states such as unstable angina, ischemic stroke, and heart attack. Due to the pervading of thrombotic diseases, new antiplatelet drugs are necessary for preventing and treating arterial thrombosis without adverse side effects. Traditional medicinal herbs have been used for the treatment of human ailments for a long time. The clinically useful and safe products from traditional medicinal herbs were identified and developed in numerous pharmacological approaches. A complementary system of traditional medicinal herbs is a good candidate for pharmacotherapy. However, it still has a limitation in its function and efficacy. Thus, it is necessary to study the mode of action of traditional medicinal herbs as alternative therapeutic agents. In this review, we focused on our current understanding of the regulatory mechanisms of traditional medicinal herbs in antiplatelet activity and antithrombotic effect of traditional medicinal herbs on platelet function.

Intracoronary high-dose bolus tirofiban administration during complex coronary interventions: A United States-based case series

The GP IIb/IIIa inhibitors (GPIs) rapidly provide therapeutic levels of platelet aggregation inhibition and serve as adjunct pharmacotherapy to oral P2Y12 inhibitors that exhibit a significant delay in onset of action for patients with Acute Coronary Syndrome (ACS). Intracoronary (IC) administration of the high dose bolus (HDB) tirofiban has not been extensively studied. Compared to intravenous delivery, IC administration can lead to higher local drug concentration and, therefore, provide instantaneous disruption of platelet aggregation in the culprit vessel. This report describes the successful resolution of thrombus using IC HDB tirofiban in 7 high-risk coronary interventions with complications such as recurrent thrombosis and cardiogenic shock in ACS patients. This report represents the first case series of IC HDB tirofiban performed in North America and suggests that IC HDB tirofiban may represent an effective and safe strategy to achieve rapid thrombus resolution in ACS patients.

Complications of intracoronary abciximab bolus-only versus standard protocol during percutaneous coronary intervention in acute coronary syndrome

BACKGROUND

Abciximab reduces major adverse cardiac events in patients with ST elevation myocardial infarction undergoing primary percutaneous coronary intervention (pPCI). Standard protocol is intravenous abciximab bolus during PCI plus abciximab infusion for 12-18 h post pPCI. Intracoronary (IC) abciximab bolus administration results in high local drug concentrations and hence it should have higher antiplatelet effect. In this study, we assess the short-term efficacy and safety of IC compared to IV bolus of abciximab in ACS patients during pPCI.

METHODS

We compared the clinical outcomes between the IC (n = 56) and standard protocol (n = 170) group of patients. Primary endpoints included bleeding/vascular/ischemic complications and MACE.

RESULTS

The two groups were similar with respect to baseline characteristics. IC abciximab bolus only reduced bleeding complications, with no moderate bleed versus 7.2% in standard protocol group (p value 0.04). Ischemic/vascular complications had statistically insignificant difference between the two groups.

CONCLUSION

We found no significant difference between IC abciximab bolus only and standard abciximab therapy in terms of ischemic/vascular complications and MACE. But there was higher risk of moderate bleed in standard therapy group. The IC bolus route of abciximab may be superior to the intravenous route. Prospective randomized trials are warranted to validate these findings.

Regulation of smooth muscle cells in development and vascular disease: current therapeutic strategies

Vascular smooth muscle cells (SMCs) exhibit extensive phenotypic diversity and rapid growth during embryonic development, but maintain a quiescent, differentiated state in adult. The pathogenesis of vascular proliferative diseases involves the proliferation and migration of medial vascular SMCs into the vessel intima, possibly reinstating their embryonic gene expression programs. Multiple mitogenic stimuli induce vascular SMC proliferation through cell cycle progression. Therapeutic strategies targeting cell cycle progression and mitogenic stimuli have been developed and evaluated in animal models of atherosclerosis and vascular injury, and several clinical studies. Recent discoveries on the recruitment of vascular progenitor cells to the sites of vascular injury suggest new therapeutic potentials of progenitor cell-based therapies to accelerate re-endothelialization and prevent engraftment of SMC-lineage progenitor cells. Owing to the complex and multifactorial nature of SMC regulation, combinatorial antiproliferative approaches are likely to be used in the future in order to achieve maximal efficacy and reduce toxicity.

Integrin αIIbβ3: from discovery to efficacious therapeutic target

From the initial description of platelets in 1882, their propensity to aggregate and to contribute to thrombosis was apparent. Indeed, excessive platelet aggregation is associated with myocardial infarction and other thrombotic diseases whereas Glanzmann thrombasthenia, in which platelet aggregation is reduced, is a bleeding syndrome. Over the last half of the 20th century, many investigators have provided insights into the cellular and molecular basis for platelet aggregation. The major membrane protein on platelets, integrin αIIbβ3, mediates this response by rapidly transiting from its resting to an activated state in which it serves as a receptor for ligands that can bridge platelets together. Monoclonal antibodies, natural products, and small peptides were all shown to inhibit αIIbβ3 dependent platelet aggregation, and these inhibitors became the forerunners of antagonists that proceeded through preclinical testing and into large patient trials to treat acute coronary syndromes, particularly in the context of percutaneous coronary interventions. Three such αIIbβ3 antagonists, abciximab, eptifibatide, and tirofiban, received Food and Drug Administration approval. Over the past 15 years, millions of patients have been treated with these αIIbβ3 antagonists and many lives have been saved by their administration. With the side effect of increased bleeding and the development of new antithrombotic drugs, the use of αIIbβ3 antagonists is waning. Nevertheless, they are still widely used for the prevention of periprocedural thrombosis during percutaneous coronary interventions. This review focuses on the biology of αIIbβ3, the development of its antagonists, and some of the triumphs and shortcomings of αIIbβ3 antagonism.

Antiplatelet and antithrombin strategies in acute coronary syndrome: state-of-the-art review

Antiplatelet and antithrombotic agents significantly alter the clinical course of patients with acute coronary syndrome (ACS) and hence form the bedrock of the management pathway of this closely related continuum of coronary pathologies. The contemporary therapeutic armamentarium for the treatment of ACS now reflects the many technical and pharmacological advances that took place over the last two decades. In the original 1996 American College of Cardiology/ American Heart Association (ACC/AHA) guidelines for the management of acute myocardial infarction, only one antiplatelet agent (Aspirin) and one anticoagulant (unfractionated heparin) were recommended as class I therapies. Since then many newer agents have been developed and approved for routine clinical use in ACS patients. Recent research has focussed on improving efficacy on one hand and reducing bleeding complications on the other. This review focuses on the mechanism, efficacy, safety profile and clinical trial evidence of P2 Y12 receptor antagonist antiplatelet agents, glycoprotein IIb/IIIa receptor inhibitors (GPI), protease-activated receptor-1 (PAR-1) inhibitors, thrombin inhibitor bivalirudin and Factor Xa inhibitors fondaparinaux and rivaroxaban.

Antiplatelet drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

The article describes the mechanisms of action, pharmacokinetics, and pharmacodynamics of aspirin, dipyridamole, cilostazol, the thienopyridines, and the glycoprotein IIb/IIIa antagonists. The relationships among dose, efficacy, and safety are discussed along with a mechanistic overview of results of randomized clinical trials. The article does not provide specific management recommendations but highlights important practical aspects of antiplatelet therapy, including optimal dosing, the variable balance between benefits and risks when antiplatelet therapies are used alone or in combination with other antiplatelet drugs in different clinical settings, and the implications of persistently high platelet reactivity despite such treatment.

Glycoprotein IIb/IIIa inhibitors: an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy

The human glycoprotein (GP)IIb/IIIa belongs to a large family of cation-dependent adhesion molecules known as integrins, which share a common heterodimeric structure. The primary function of GPIIb/IIIa is to aid platelet aggregation by transmitting bidirectional signals across the plasma membrane. Since the GPIIb/IIIa receptor is among the key integrins involved in platelet aggregation and, therefore, thrombus formation, the development of GPIIb/IIIa antagonists (e.g., abciximab, eptifibatide and tirofiban) has become an attractive strategy for antiplatelet therapy with an expected strong and specific effect. All three drugs are administered intravenously, and large-scale clinical trials have demonstrated a clear clinical benefit and good safety profile in high-risk patients, especially those undergoing percutaneous coronary intervention. However, the adverse events related to thrombosis or bleeding are still reported in patients undergoing therapy with GPIIb/IIIa antagonists and reflect a variable interindividual responsiveness. Therefore, some form of laboratory monitoring is required to optimize the effects of a drug or to indicate that it needs replacing with other antithrombotic agents, as well as for identifying and enhancing the platelet inhibition in this subgroup of patients to improve the clinical outcome and reduce bleeding complications. As such, the aim of this article is to provide an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy in patients undergoing therapy with GPIIb/IIIa antagonists.

Prevention of the renarrowing of coronary arteries using drug-eluting stents in the perioperative period: an update

The management of patients scheduled for surgery with a coronary stent, and receiving 1 or more antiplatelet drugs, has many controversies. The premature discontinuation of antiplatelet drugs substantially increases the risk of stent thrombosis (ST), myocardial infarction, and cardiac death, and surgery under an altered platelet function could also lead to an increased risk of bleeding in the perioperative period. Because of the conflict in the recommendations, this article reviews the current antiplatelet protocols after positioning a coronary stent, the evidence of increased risk of ST associated with the withdrawal of antiplatelet drugs and increased bleeding risk associated with its maintenance, the different perioperative antiplatelet protocols when patients are scheduled for surgery or need an urgent operation, and the therapeutic options if excessive bleeding occurs.

A monoclonal antibody against alphaVbeta3 integrin inhibits development of atherosclerotic lesions in diabetic pigs

Atherosclerotic lesions develop and progress more rapidly in diabetic patients than in nondiabetic individuals. This may be caused by accelerated lesion formation in the high-glucose environment of diabetes. Smooth muscle cells (SMCs) cultured in high glucose are more responsive to growth factors such as insulin-like growth factor-1 (IGF-1). This enhanced response to IGF-1 is due in part to increased activation of the alpha(V)beta(3) integrin. We tested whether alpha(V)beta(3) integrin activation was increased in diabetic animals and whether an antibody to beta(3) would inhibit IGF-1 action and development of atherosclerosis. Eight male pigs were made diabetic with streptozotocin and fed a high-fat diet. A F(ab)(2) antibody fragment directed at beta(3) was infused into one femoral artery, whereas the other artery received control F(ab)(2) for 3.5 months. There was a 65 +/- 8% reduction in atherosclerotic lesion area in the arteries treated with F(ab)(2) antibody to beta(3). Phosphorylation of beta(3) was reduced by 75 +/- 18% in vessels treated with the antibody. Shc and mitogen-activated protein kinase phosphorylation, which are required for IGF-1-stimulated SMC proliferation, were also significantly reduced. We conclude that activation of IGF-1 receptor and alpha(V)beta(3)-linked signaling pathways accelerates atherosclerosis in diabetes and that administration of an antibody to beta(3) to diabetic pigs inhibits alpha(V)beta(3) activation, IGF-1-stimulated signaling, and atherosclerotic lesion development. This approach offers a potential therapeutic approach to the treatment of this disorder.

The safety and side effects of monoclonal antibodies

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases, as well as a range of new indications. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness and the generation of antibodies. In addition, there are numerous adverse effects of mAbs that are related to their specific targets, including infections and cancer, autoimmune disease, and organ-specific adverse events such as cardiotoxicity. In March 2006, a life-threatening cytokine release syndrome occurred during a first-in-human study with TGN1412 (a CD28-specific superagonist mAb), resulting in a range of recommendations to improve the safety of initial human clinical studies with mAbs. Here, we review some of the adverse effects encountered with mAb therapies, and discuss advances in preclinical testing and antibody technology aimed at minimizing the risk of these events.

Enhanced proliferation and migration of vascular smooth muscle cells in response to vascular injury under hyperglycemic conditions is controlled by beta3 integrin signaling

Atheroma formation and restenosis following percutaneous vascular intervention involve the growth and migration of vascular smooth muscle cells (SMCs) into neointimal lesions, in part due to changes in the extracellular matrix. While some clinical studies have suggested that, in comparison to non-diabetics, beta3 integrin inhibition in diabetic patients confers protection from restenosis, little is known regarding the role of beta3 integrin inhibition on SMC responses in this context. To understand the molecular mechanisms underlying integrin-mediated regulation of SMC function in diabetes, we examined SMC responses in diabetic mice deficient in integrin beta3 and observed that the integrin was required for enhanced proliferation, migration and extracellular regulated kinase (ERK) activation. Hyperglycemia-enhanced membrane recruitment and catalytic activity of PKCbeta in an integrin beta3-dependent manner. Hyperglycemia also promoted SMC filopodia formation and cell migration, both of which required alphaVbeta3, PKCbeta, and ERK activity. Furthermore, the integrin-kinase association was regulated by the alphaVbeta3 integrin ligand thrombospondin and the integrin modulator Rap1 under conditions of hyperglycemia. These results suggest that there are differences in SMC responses to vascular injury depending on the presence or absence of hyperglycemia and that SMC response under hyperglycemic conditions is largely mediated through beta3 integrin signaling.

Management of patients with unstable angina / non-ST-elevation myocardial infarction: a critical review of the 2007 ACC /AHA guidelines

BACKGROUND

In 2007, the American College of Cardiology/American Heart Association (ACC/AHA) published new guidelines for the diagnosis and management of patients with unstable angina/non-ST segment elevation myocardial infarction (UA/NSTEMI). These guidelines include some important updates on the use of clopidogrel, fondaparinux, bivalirudin and low-molecular-weight heparins (LMWHs) all of which have published landmark clinical trials in patients with acute coronary syndromes (ACS) since the publication of the 2002 guidelines. While these 2007 guidelines are more comprehensive and up-to-date compared with the recommendations published in 2002, they also raise many questions for practising emergency physicians and cardiologists.

METHODS

This article presents a critical review of the 2007 ACC/AHA UA/NSTEMI guidelines, highlighting some of the areas of controversy, with the aim of providing some further guidance to practising physicians.

CONCLUSIONS

Despite recent updates to the ACC/AHA UA/NSTEMI guidelines, additional factors need to be taken into consideration in the management of UA/NSTEMI patients. Integrating initial responses with early or selectively invasive strategies and the risks of complications in subsequent procedures require careful consideration. Protocol development within an institution is required to risk-stratify patients rapidly, provide optimum precatheterisation medical management and allow seamless and rapid transitions to the catheterisation laboratory in patients at risk for adverse events.

Tweaking the gain on platelet regulation: the tachykinin connection

Soluble factors such as ADP and thromboxane (TX) A(2) that are secreted or released by platelets at sites of tissue injury, mediate autocrine and paracrine regulation of platelet function, resulting in rapid localised thrombus formation. The suppression of platelet function, particularly through targeting such secondary regulatory mechanisms, that serve to 'fine-tune' the platelet response, has proven effective in the prevention of inappropriate platelet activation that results in thrombosis. The most commonly used anti-platelet approaches (ADP receptor antagonism or inhibition of TXA(2) synthesis), however, lack efficacy in many patients, suggesting the existence of additional uncharacterised mechanisms for the regulation of platelet function. Recent data, which form a focus of this review, have identified peripheral tachykinin peptide family members, such as substance P and the newly identified endokinins, as physiologically important positive feedback regulators of platelet function. The actions of tachykinins that are released from platelets during activation are mediated by the neurokinin-1 receptor. Initial analysis of the role of this receptor in platelet thrombus formation, and thrombosis in the mouse, indicate this to be a promising new target for the development of anti-thrombotic drugs.

The GPIIb/IIIa (integrin alphaIIbbeta3) odyssey: a technology-driven saga of a receptor with twists, turns, and even a bend

Starting 90 years ago with a clinical description by Glanzmann of a bleeding disorder associated with a defect in platelet function, technologic advances helped investigators identify the defect as a mutation(s) in the integrin family receptor, alphaIIbbeta3, which has the capacity to bind fibrinogen (and other ligands) and support platelet-platelet interactions (aggregation). The receptor's activation state was found to be under exquisite control, with activators, inhibitors, and elaborate inside-out signaling mechanisms controlling its conformation. Structural biology has produced high-resolution images defining the ligand binding site at the atomic level. Research on alphaIIbbeta3 has been bidirectional, with basic insights resulting in improved Glanzmann thrombasthenia carrier detection and prenatal diagnosis, assays to identify single nucleotide polymorphisms responsible for alloimmune neonatal thrombocytopenia, and the development of alphaIIbbeta3 antagonists, the first rationally designed antiplatelet agents, to prevent and treat thrombotic cardiovascular disease. The future looks equally bright, with the potential for improved drugs and the application of gene therapy and stem cell biology to address the genetic abnormalities. The alphaIIbbeta3 saga serves as a paradigm of rigorous science growing out of careful clinical observations of a rare disorder yielding both important new scientific information and improved diagnosis, therapy, and prevention of other disorders.

Bolus-only versus bolus + infusion of glycoprotein IIb/IIIa inhibitors during percutaneous coronary intervention

BACKGROUND

The present study was done to analyze if glycoprotein IIb/IIIa inhibitors (GPI) bolus-only will reduce vascular/bleeding complications and cost with similar major adverse cardiac events (MACE) when compared with GPI bolus + infusion. Evidence-based therapy of GPI inhibitors during percutaneous coronary intervention (PCI) incorporates intravenous bolus followed by 12 to 18 hours of infusion. However, GPI bolus + infusion may increase vascular/bleeding complications and may not reduce MACE when compared with GPI bolus-only.

METHODS

From January 1, 2003, to December 31, 2004, 2,629 consecutive patients received GPI during PCI at a single center. Of these, 1,064 patients received GPI bolus + infusion in 2003 and were compared with 1,565 patients that received GPI bolus-only in 2004. Baseline characteristics were similar in both groups.

RESULTS

Patients receiving GPI bolus-only had reduced vascular/bleeding complications when compared with bolus + infusion (4.9% vs 7%, P < .05, odds ratio 0.62, 95% confidence interval 0.45-0.89). Furthermore, ischemic complications were similar in both groups, including periprocedural creatine kinase-MB enzyme release (12.8% vs 15.3%, P = NS), MACE at 30 days (3.2% vs 3%, P = NS), and death and myocardial infarction at 1 year (7.1% vs 7.8%, P = NS). In addition, GPI bolus-only reduced cost in US dollars ($323 vs $706, P < .001) and increased ambulatory PCI (13.1% vs 3.2%, P < .01), with reduced length of stay (1.1 vs 1.6 days, P < .01), when compared with GPI bolus + infusion.

CONCLUSIONS

Glycoprotein inhibitor bolus-only reduces vascular/bleeding complications with similar MACE and reduced cost when compared with GPI bolus + infusion. In addition, GPI bolus-only improved ambulatory PCI and reduced length of stay. These results are consistent with a safer and cost-effective strategy for bolus-only when GPI therapy is considered during PCI.

Antiplatelet drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article about currently available antiplatelet drugs is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the mechanism of action, pharmacokinetics, and pharmacodynamics of aspirin, reversible cyclooxygenase inhibitors, thienopyridines, and integrin alphaIIbbeta3 receptor antagonists. The relationships among dose, efficacy, and safety are thoroughly discussed, with a mechanistic overview of randomized clinical trials. The article does not provide specific management recommendations; however, it does highlight important practical aspects related to antiplatelet therapy, including the optimal dose of aspirin, the variable balance of benefits and hazards in different clinical settings, and the issue of interindividual variability in response to antiplatelet drugs.

Future innovations in anti-platelet therapies

Platelets have long been recognized to be of central importance in haemostasis, but their participation in pathological conditions such as thrombosis, atherosclerosis and inflammation is now also well established. The platelet has therefore become a key target in therapies to combat cardiovascular disease. Anti-platelet therapies are used widely, but current approaches lack efficacy in a proportion of patients, and are associated with side effects including problem bleeding. In the last decade, substantial progress has been made in understanding the regulation of platelet function, including the characterization of new ligands, platelet-specific receptors and cell signalling pathways. It is anticipated this progress will impact positively on the future innovations towards more effective and safer anti-platelet agents. In this review, the mechanisms of platelet regulation and current anti-platelet therapies are introduced, and strong, and some more speculative, potential candidate target molecules for future anti-platelet drug development are discussed.

One-year clinical outcome after abciximab bolus-only compared with abciximab bolus and 12-hour infusion in the Randomized EArly Discharge after Transradial Stenting of CoronarY Arteries (EASY) Study

BACKGROUND

Long-term clinical follow-up has shown a significant benefit after percutaneous coronary intervention (PCI) for abciximab bolus followed by 12-hour infusion over placebo or bolus-only. With contemporary techniques and clopidogrel pretreatment, it is unknown whether the 12-hour infusion is still associated with a clinical benefit. The purpose of this study is to compare 6- and 12-month clinical outcomes in patients treated after PCI with abciximab bolus-only and abciximab bolus followed by 12-hour infusion.

METHODS

After a bolus of abciximab (0.25 mg/kg) and uncomplicated transradial coronary stenting, 1,005 patients were randomized either to same-day discharge and no infusion of abciximab (bolus-only group, n = 504) or to overnight hospitalization and 12 hours (0.125 microg/[kg min]) of abciximab infusion (bolus + infusion group, n = 501). The rate of major adverse cardiovascular events (MACE) was evaluated at 30 days, 6 months, and 12 months.

RESULTS

At 30 days, the rate of MACE including death, myocardial infarction, and target vessel revascularization was similar in the 2 groups: 1.4% in the bolus-only group versus 1.8% in the bolus + infusion group (P = .63). At 6 months, the MACE rate was 5.6% in the 2 randomized groups. At 12 months, the MACE rate was also similar in both groups: 8.7% in the bolus-only group and 9.2% in the bolus + infusion group (hazard ratio 0.97, 95% CI 0.79-1.20, P = .80). Similar efficacy was also observed in several subgroups including higher-risk patients such as those with elevated troponin T before PCI.

CONCLUSIONS

In patients pretreated with clopidogrel and undergoing uncomplicated coronary artery stenting, there is no difference in the 6- and 12-month outcomes between patients treated with abciximab bolus-only versus those treated with bolus + infusion, a finding consistent with the initial 30-day outcomes.

In vitro and in vivo evidence for shear-induced activation of latent transforming growth factor-beta1

Transforming growth factor-beta1 (TGF-beta1) has potent physiologic and pathologic effects on a variety of cell types at subnanomolar concentrations. Platelets contain 40 times as much TGF-beta1 as other cells and secrete it as an inactive (latent) form in complex with latency-associated peptide (LAP), which is disulfide bonded via Cys33 to latent TGF-beta binding protein 1 (LTBP-1). Little is known about how latent TGF-beta1 becomes activated in vivo. Here we show that TGF-beta1 released from platelets or fibroblasts undergoes dramatic activation when subjected to stirring or shear forces, providing a potential mechanism for physiologic control. Thiol-disulfide exchange appears to contribute to the process based on the effects of thiol-reactive reagents and differences in thiol labeling of TGF-beta1 before and after stirring or shear. Activation required the presence of LTBP, as TGF-beta1 contained in complex with only LAP could not be activated by stirring when studied as either a recombinant purified protein complex or in the platelet releasates or sera of mice engineered to contain an LAP C33S mutation. Release and activation of latent TGF-beta1 in vivo was demonstrated in a mouse model 5 minutes after thrombus formation. These data potentially provide a novel mechanism for in vivo activation of TGF-beta1.

Impact of bivalirudin on outcomes after percutaneous coronary revascularization with drug-eluting stents

BACKGROUND

The direct thrombin inhibitor bivalirudin has been found to be noninferior to heparin plus planned glycoprotein (GP) IIb/IIIa blockade in the prevention of acute ischemic end points and 1-year mortality after percutaneous coronary intervention (PCI) with bare metal stents. We investigated whether long-term outcomes after bivalirudin use remained comparable to heparin plus GP IIb/IIIa blockade in current clinical practice of drug-eluting stent use.

METHODS

Using the 2004-2005 Cornell Angioplasty Registry, we studied 2504 consecutive patients undergoing urgent or elective PCI with periprocedural use of bivalirudin or heparin plus GP IIb/IIIa platelet inhibitors. Patients presenting with an acute ST-elevation myocardial infarction (MI) < or = 24 hours, thrombolytic therapy < or = 7 days, hemodynamic instability/shock, or renal insufficiency were excluded.

RESULTS

Of the study cohort, 1340 patients (54%) received bivalirudin and 1164 patients (46%) received heparin plus GP IIb/IIIa blockade. The incidence of inhospital mortality (0.3% vs 0.2%, P = .692), MI (6.6% vs 8.1%, P = .191), and combined end point of death, stroke, emergent coronary artery bypass graft/PCI, and MI (6.9% vs 8.3%, P = .199) was similar in the bivalirudin and heparin plus GP IIb/IIIa inhibitor groups. There was a lower incidence of major (0.7% vs 1.9%, P = .012) and minor bleeding (9.6% vs 15.6%, P < .001) in the bivalirudin versus heparin plus GP IIb/IIIa inhibitor group. Mean clinical follow-up was 24.8 +/- 7.7 months. At follow-up, there were 87 (6.5%) deaths in the bivalirudin group versus 42 (3.6%) in the heparin plus GP IIb/IIIa inhibitor group (hazard ratio 1.87, 95% CI 1.30-2.71, P = .001). After a propensity score adjusted multivariate Cox analysis, bivalirudin use was associated with a nonsignificant trend toward increased long-term mortality (hazard ratio 1.45, 95% CI 0.98-2.16, P = .065).

CONCLUSIONS

Compared with heparin plus GP IIb/IIIa inhibition, routine use of bivalirudin as the procedural anticoagulant in contemporary PCI with drug-eluting stents was associated with lower rates of inhospital complications and similar long-term all-cause mortality.

Temporal Trends, Safety, and Efficacy of Bivalirudin in Elective Percutaneous Coronary Intervention: Insights from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium

OBJECTIVE

To evaluate the safety and efficacy of bivalirudin based therapy among patients undergoing percutaneous coronary intervention (PCI) for stable coronary artery disease in a large multicenter registry.

BACKGROUND

The REPLACE I trial demonstrated the non-inferiority of a strategy of bivalirudin compared with heparin and glycoprotein (GP) IIbIIIa inhibition in patients undergoing PCI. There is a paucity of outcome data with bivalirudin use in the setting of real-world PCI practice.

METHODS

We evaluated the outcome of 11,719 patients who underwent elective PCI for stable coronary artery disease (CAD) from 2002 to 2004 in a large regional consortium, and who were treated with bivalirudin (n = 2051) or with heparin and GP IIbIIIa inhibitors (n = 9,668). The primary endpoints were transfusion and in-hospital major adverse cardiovascular events (MACE) defined as the composite of death, MI, stroke, and any coronary artery bypass grafting (CABG) or target lesion revascularization.

RESULTS

Compared with patients who received heparin plus GP IIbIIIa inhibitors, patients who received bivalirudin had a similar incidence of post-procedural MI, stroke, in-hospital death, MACE (2.88 vs. 2.48, P = 0.30), or transfusion (2.83% vs. 2.41%, P = 0.27). Patients at greater risk of bleeding were more likely to be treated with bivalirudin. After adjusting for the propensity to receive bivalirudin and for baseline co-morbidities, there was no difference in the odds of MACE or the need for transfusion between the two groups.

CONCLUSION

Compared with heparin plus GP IIbIIIa inhibition, use of bivalirudin in patients undergoing PCI for stable CAD is associated with similar ischemic and bleeding complications. Given the ease of administration and lower cost, bivalirudin provides an attractive treatment option in this patient population.

Platelet inhibitors in non-ST-segment elevation acute coronary syndromes and percutaneous coronary intervention: glycoprotein IIb/IIIa inhibitors, clopidogrel, or both?

The role of glycoprotein (Gp) IIb/IIIa receptor antagonists remains controversial and these agents are infrequently utilized during non-ST-segment elevation acute coronary syndromes (NSTE-ACS) despite American Heart Association/American College of Cardiology guidelines. Despite recommendations, the NRMI-4 (National Registry of Myocardial Infarction 4) and CRUSADE (Can rapid risk stratification of unstable angina patients suppress adverse outcomes with early implementation of the ACC/AHA guidelines?) registries observed that only 25%-32% of eligible patients received early Gp IIb/IIIa therapy, despite a 6.3% absolute mortality reduction in NRMI-4 and a 2% absolute mortality reduction in CRUSADE. A pooled analysis of Gp IIb/IIIa data from these registries suggest a major reduction in mortality (Odds Ratio = 0.43, 95% Confidence Index 0.25-0.74, p = 0.002) with early Gp IIb/IIIa therapy, yet clinicians fail to utilize this option in NSTE-ACS. The evidence-based approach to NSTE-ACS involves aspirin, clopidogrel, low-molecular weight heparins, or unfractionated heparin in concert with Gp IIb/Ila receptor antagonists, however, newer percutaneous coronary intervention (PCI)-based trials challenge current recommendations. Novel strategies emerging in NSTE-ACS include omitting Gp IIb/Ila inhibitors altogether or using Gp IIb/IIIa inhibitors with higher doses of clopidogrel in selected patients. The ISAR-REACT (Intracoronary stenting and antithrombotic regimen-Rapid early action for coronary treatment) and ISAR-SWEET (ISAR-Is abciximab a superior way to eliminate elevated thrombotic risk in diabetics) trials question the value of abciximab when 600 mg of clopidogrel concurrently administered during PCI. The CLEAR-PLATELETS (Clopidogrel loading with eptifibatide to arrest the reactivity of platelets) and PEACE (Platelet activity extinction in non-Q-wave MI with ASA, clopidogrel, and eptifibatide) trials suggest more durable platelet inhibition when Gp IIb/IIIa inhibitors are used with higher doses clopidogrel. The ISAR-COOL (ISAR: Cooling off strategy) trial found no difference in ischemic outcomes when Gp IIb/IIIa inhibitors were excluded and ARMYDA-2 (Antiplatelet therapy for reduction of myocardial damage during angioplasty) suggested higher doses of clopidogrel are more appropriate during PCI when Gp IIb/IIIa inhibitors are not utilized. This constellation of new trials forces reconsideration of current recommendations in regards to patient risk stratification, choice of antithrombotic therapy, doses, and timing. These new data will impact emerging guidelines and updates are currently in progress.

Benefit of bolus-only platelet glycoprotein IIb/IIIa inhibition during percutaneous coronary intervention: insights from the very early outcomes in the Evaluation of 7E3 for the Prevention of Ischemic Complications (EPIC) trial

BACKGROUND

Platelet glycoprotein IIb/IIIa inhibitors are administered during percutaneous coronary intervention as a bolus followed by infusion. The need for an infusion was established by the Evaluation of 7E3 for the Prevention of Ischemic Complications (EPIC) trial conducted during the percutaneous transluminal coronary balloon angioplasty (PTCA) era, when the threat of acute thrombotic complications prevailed over concerns regarding bleeding, and stenting was considered an adverse event.

METHODS

The EPIC trial randomized high-risk PTCA patients to 3 arms: placebo, abciximab bolus only, and abciximab bolus plus infusion. The present analysis of the EPIC outcomes was done at 6-hour intervals during the first 24 hours after PTCA to identify any early benefit derived from the abciximab bolus-only arm.

RESULTS

At 6 hours after randomization, the primary composite end point of death, myocardial infarction, or urgent intervention was significantly reduced by 46% with abciximab bolus-only compared with placebo (2.9% vs 5.3%; P = .022), which is mainly due to a reduced rate of urgent intervention. There was also a numerical but not statistically significant reduction in myocardial infarction rate using abciximab bolus-only compared with placebo. A lower bleeding rate in the bolus-only arm compared with bolus plus infusion has been reported.

CONCLUSIONS

As stenting and thienopyridine use have become routine, there has been a decrease in the incidence of acute closure and an increasing concern for bleeding complications after percutaneous coronary intervention, which potentially may be addressed by adopting a bolus-only glycoprotein IIb/IIIa inhibitor strategy. The early protective ischemic effect of abciximab bolus-only observed in the EPIC trial may be relevant in this regard.

Antithrombotic therapy for percutaneous coronary intervention

This article outlines the antiplatelet and antithrombotic therapy used in contemporary percutaneous coronary interventions. It is a comprehensive review of past and present pharmacologic agents and includes a discussion of the more promising potential future therapies. The clinical trials that provide the basis for the current standard of care are provided, as are ongoing trials that will likely shape the future standard. This article is not intended to provide a detailed discussion of precise mechanistic or structural features of each agent but to serve as a practical clinical guide to the interventionalist when choosing specific pharmacotherapies for specific patients in the catheterization laboratory.

Reconstitution of CD39 in liposomes amplifies nucleoside triphosphate diphosphohydrolase activity and restores thromboregulatory properties

BACKGROUND

CD39 (nucleoside triphosphate diphosphohydrolase [NTPDase-1]) expressed on the luminal surface of endothelial cells rapidly metabolizes extracellular adenosine triphosphate (ATP) and adenosine diphosphate (ADP) to adenosine monophosphate (AMP), and abrogates platelet reactivity. Optimization of CD39 enzymatic activity appears dependent upon the expression of both transmembrane domains within plasma membranes. Thus, motivation exists to examine therapeutic antiplatelet formulations that consist of liposomal CD39.

METHODS

Full-length human CD39 was produced by using a yeast expression system, purified, and reconstituted within lipid vesicles. The catalytic efficiency (kcat/Km) of CD39-mediated phosphohydrolysis of ADP and ATP was determined both for detergent-solubilized and protein-reconstituted CD39 within lipid membranes. The capacity of CD39-containing lipid vesicles to inhibit platelet activation induced by ADP, collagen, or thrombin was determined in vitro by platelet aggregometry. A murine model of thromboplastin-induced thromboembolism was used to determine the effectiveness of intravenous liposomal CD39 in limiting platelet consumption and mortality.

RESULTS

Reconstitution of human CD39 in lipid vesicles was associated with a decrease in Km of nearly an order of magnitude over the detergent-solubilized form. There was a concomitant increase in both ADPase and ATPase catalytic efficiencies (kcat/Km ADPase: sol CD39: 2.7 x 10(6) vs liposomal CD39: 1.4 x 10(7) min/ M; kcat/Km ATPase: sol CD39: 7.2 x 10(6) vs liposomal CD39: 2.0 x10(7) min/M). Furthermore, CD39 lipid vesicles effectively inhibited platelet aggregation when activated by ADP, collagen, or thrombin, and also promoted platelet disaggregation (60.4% +/- 6.1%). Treatment with CD39 lipid vesicles preserved platelet counts after thromboplastin injection (pretreatment, 906.8 +/- 42.9 platelets/microm3; empty vesicles, 278.6 +/- 34.8 platelets/microm3; CD39 vesicles, 563.6 +/- 42.2 platelets/microm3; n = 10 mice/test group; P < .0001). In parallel survival studies, liposomal CD39 reduced mortality from 73% to 33% (P < or = .05; n = 12 mice/experimental test group, n = 15 mice/control test group).

CONCLUSIONS

Incorporation of solubilized CD39 into a lipid bilayer restores enzyme activity and optimizes thromboregulatory potential. Treatment with CD39 in liposomal formulations decreased mortality in a murine model of thromboplastin-induced thromboembolism by limiting intravascular platelet aggregation and thrombosis.

Use of glycoprotein IIb/IIIa inhibitors in unstable angina and non-ST-elevation myocardial infarction

Acute coronary syndromes (ACS) are a major cause of morbidity and mortality in Western society. The commonest underlying pathology is the coronary atherosclerotic plaque complicated by thrombosis. Platelets play a central role. As the glycoprotein IIb/IIIa receptor is involved in the final step of platelet thrombus formation development and investigation of its blockage in ACS is at the fore. Initial hospital management of ACS occur in the ED setting. The present article outlines the above topics and clarifies the place of glycoprotein IIb/IIIa receptor inhibition in ED.

Three-year duration of benefit from abciximab in patients receiving stents for acute myocardial infarction in the randomized double-blind ADMIRAL study

AIMS

The Abciximab Before Direct Angioplasty and Stenting in Myocardial Infarction Regarding Acute and Long-term Follow-up (ADMIRAL) study demonstrated that early inhibition of the platelet glycoprotein IIb/IIIa (GP IIb/IIIa) receptor with abciximab led to improved coronary patency, left ventricular function, and clinical outcomes. The current long-term follow-up study evaluated the durability of the positive outcomes.

METHODS AND RESULTS

The randomized double-blind ADMIRAL trial enrolled 300 patients who received either abciximab plus stenting or placebo plus stenting for the treatment of ST-elevation myocardial infarction (STEMI). Abciximab (bolus of 0.25 mg/kg body weight, followed by 12 h infusion of 0.125 microg/kg per min) was administered to 149 patients, whereas 151 patients received placebo. Long-term follow-up was conducted in a blinded manner by either patient chart review or telephone interview. Long-term follow-up data were obtained on 288 patients (96%). After 3 years, using an intent-to-treat analysis, the outcome of all-cause mortality occurred in 9.1% of abciximab-treated patients when compared with 12.2% of placebo patients, absolute and relative risk reductions of 3.1 and 25%, respectively (P=0.36). Parallel Kaplan-Meier curves were observed for the cumulative incidence of death or re-infarction, which was reduced from 16.9% in the placebo group to 11.8% in the abciximab group, absolute and relative risk reductions of 5.1 and 30%, respectively (P=0.20). Rates of recurrent ischaemia were significantly reduced from 21.7 to 11.5% (P=0.05).

CONCLUSION

Adjunctive abciximab to primary stenting for STEMI elicits favourable clinical outcomes with the same absolute risk reductions of hard clinical outcomes from 30 days up to 3 years of follow-up.

Pharmacological basis of different targets for the treatment of atherosclerosis

The development of atherosclerotic plaque is a highly regulated and complex process which occurs as a result of structural and functional alterations in endothelial cells, smooth muscle cells (SMCs), monocytes/macrophages, T-lymphocytes and platelets. The plaque formation in the coronary arteries or rupture of the plaque in the peripheral vasculature in latter stages of atherosclerosis triggers the onset of acute ischemic events involving myocardium. Although lipid lowering with statins has been established as an important therapy for the treatment of atherosclerosis, partially beneficial effects of statins beyond decreasing lipid levels has shifted the focus to develop newer drugs that can affect directly the process of atherosclerosis. Blockade of renin angiotensin system, augmentation of nitric oxide availability, reduction of Ca(2+) influx, prevention of oxidative stress as well as attenuation of inflammation, platelet activation and SMC proliferation have been recognized as targets for drug treatment to control the development, progression and management of atherosclerosis. A major challenge for future drug development is to formulate a combination therapy affecting different targets to improve the treatment of atherosclerosis.

Mortality at 1 year for the direct comparison of tirofiban and abciximab during percutaneous coronary revascularization: do tirofiban and ReoPro give similar efficacy outcomes at trial 1-year follow-up

AIMS

Compared with placebo, abciximab has been associated with mortality reduction at late follow-up. The TARGET trial was performed to test whether tirofiban and abciximab provide similar efficacy outcomes among patients undergoing non-emergent, stent-based percutaneous coronary intervention. We report here the 1-year mortality of the study population.

METHODS AND RESULTS

In 18 countries at 149 hospitals, 4,809 patients undergoing elective or urgent stent implantation were randomly assigned a bolus and infusion of tirofiban or abciximab. Ischaemic events were assessed at 30 days and 6 months and mortality was assessed at 1 year. We previously reported that abciximab was superior to tirofiban considering the composite rate of death or myocardial infarction at 30 days among all patients and at 6 months among those with an acute coronary syndrome (ACS). At 1-year follow-up death occurred in 46 (1.9%) patients who received tirofiban and 42 (1.7%) patients who received abciximab (hazard ratio 1.10, 95% CI 0.72-1.67; P=0.660). Mortality rates for patients with ACS were 2.3% with tirofiban vs. 2.2% with abciximab (hazard ratio 1.03, 95% CI 0.64-1.67; P=0.897) and those without ACS were 1.4 vs. 1.0% (hazard ratio 1.32, 95% CI 0.56-3.13; P=0.530).

CONCLUSION

At 1 year, tirofiban provided a similar level of survival benefit compared with abciximab.

Use of bivalirudin during percutaneous coronary intervention in patients with diabetes mellitus: an analysis from the randomized evaluation in percutaneous coronary intervention linking angiomax to reduced clinical events (REPLACE)-2 trial

OBJECTIVES

The objective of this study was to confirm that the efficacy and safety of percutaneous coronary intervention (PCI) in diabetic patients are not compromised by a bivalirudin-based antithrombotic strategy.

BACKGROUND

Previous studies have shown a survival benefit with use of platelet glycoprotein (GP) IIb/IIIa inhibitors in diabetic patients undergoing PCI. The Randomized Evaluation in Percutaneous Coronary Intervention Linking Angiomax to Reduced Clinical Events (REPLACE)-2 trial showed the non-inferiority of a strategy of bivalirudin with provisional GP IIb/IIIa inhibition compared with routine GP IIb/IIIa inhibition. The relative efficacy of these two strategies in diabetic patients has not been studied.

METHODS

We evaluated the diabetic patients enrolled in the REPLACE-2 trial to assess the impact of these antithrombotic strategies on the short- and long-term outcome after PCI.

RESULTS

The REPLACE-2 trial enrolled 1,624 diabetic patients and 4,368 non-diabetic patients. Compared with non-diabetic patients, diabetic patients had similar short-term outcome but higher mortality at 1 year (3.06% vs. 1.85%, p = 0.004). There was no difference in short-term or long-term ischemic events among the diabetic patients randomized to the two arms. Specifically, the 1-year mortality rate was non-significantly lower in the bivalirudin arm, suggesting no differential survival impact of the two strategies (2.3% vs. 3.9%). There was less minor bleeding in the bivalirudin arm in diabetic patients (12.6% vs. 24.4%, p < 0.001), whereas no difference was seen in the incidence of major bleeding (3.0% vs. 3.3%, p = 0.69).

CONCLUSIONS

Compared with routine GP IIb/IIIa inhibition, the use of bivalirudin with provisional GP IIb/IIIa inhibitors in diabetic patients is associated with no differences in clinical outcomes at 30 days, a trend toward lesser mortality at 1 year, and a reduction in minor bleeding.

Choice of GPIIb/IIIa antagonist in percutaneous coronary intervention: how should economic criteria be factored in?

OBJECTIVE

Three GPIIb/IIIa antagonists are available in the market. In France, as in many countries, their acquisition costs strongly differ. The objective of this study was to analyze how economic criteria-beyond the acquisition cost-should be factored in, when choosing a GPIIb/IIIa antagonist.

METHOD

Both clinical and economic papers on the use of GPIIb/IIIa antagonists in percutaneous coronary interventions published in peer-review journals from 1994 to 2002 were reviewed and analyzed.

RESULTS

Cost differentials between products strongly vary from one 'cost concept' to another, i.e., acquisition cost, administration cost, hospital cost, net treatment cost. The comparison of efficacy is even more complicated, as most of the time only indirect comparisons are available, based on different clinical studies, with different durations and definitions of outcomes. Finally, cost-effectiveness ratios range from US dollar 10,695 per avoided event for eptifibatide (IMPACT II study) to US dollar 74,047 for tirofiban (RESTORE study).

CONCLUSION

The concept of cost, inevitably entering into the choice of a medicinal strategy, must be used with caution. The amplitude of the difference between products, and the product favored by the difference, vary according to the cost concept retained.

Effectiveness and safety of bivalirudin during percutaneous coronary intervention in a single medical center

A recent large-scale, randomized trial demonstrated the noninferiority of a strategy of bivalirudin with provisional glycoprotein (GP) IIb/IIIa inhibition compared with routine GP IIb/IIIa inhibition. There is a paucity of outcome data with bivalirudin use in the setting of real-world experience. We evaluated 6,996 patients who underwent percutaneous coronary intervention between January 2001 and December 2004 to compare early and late outcomes with a bivalirudin-based antithrombotic regimen with those with a heparin-based regimen. Propensity adjustment was performed to correct for baseline differences in patient characteristics. Bivalirudin-based therapy was used in 1,070 patients, heparin only in 801 patients, and heparin plus GP IIb/IIIa inhibitors in 5,125 patients. Compared with patients who received heparin or those who received heparin plus GP IIb/IIIa inhibitors, patients who received bivalirudin had lower incidences of bleeding (blood transfusion rate 1.7% vs 4.0%, p <0.001) and periprocedural myonecrosis (creatine kinase-MB >5 times the upper limit of normal 2.7% vs 4.3%, p = 0.016). Differences in bleeding end points remained significant after adjusting for the propensity to receive bivalirudin, but there was no difference in ischemic events. There was no difference in unadjusted long-term survival rate (log-rank test p = 0.46, total number of deaths 412, mean follow-up 17 months) or in propensity-adjusted long-term survival rate (hazard ratio 1.37, 95% confidence interval 0.90 to 2.08, p = 0.14). Compared with heparin with or without GP IIb/IIIa inhibition, the use of bivalirudin in a large consecutive patient registry at a tertiary care center was associated with fewer bleeding events and no evident increase in the incidence of ischemic complications.

One year outcomes with abciximab vs. placebo during percutaneous coronary intervention after pre-treatment with clopidogrel†

AIMS

In the Intracoronary Stenting and Antithrombotic Regimen-Rapid Early Action for Coronary Treatment Trial, the use of abciximab in patients undergoing percutaneous coronary intervention (PCI) after pretreatment with 600 mg clopidogrel for >2 h was associated with no clinically measurable benefit at 30 days. We assessed whether there was any clinical benefit from abciximab at 1 year follow-up.

METHODS AND RESULTS

After pre-treatment with 600 mg clopidogrel, a total of 2159 patients undergoing PCI for stable or unstable angina without marked ST-segment shifts or positive biomarkers were randomly assigned to receive abciximab or placebo. The occurrence of the composite endpoint of death, myocardial infarction, or target vessel revascularization was assessed at 1 year after randomization. At 1 year, the composite endpoint occurred in 23.8% of the patients in each group [relative risk (RR), 1.01; 95% confidence interval (CI), 0.85-1.20; P=0.92]. The combined incidence of death and myocardial infarction was 6.0% in the abciximab group and 6.4% in the placebo group (RR, 0.94; 95% CI, 0.67-1.32; P=0.73). The mortality rate was 2.1% in the abciximab group and 2.4% in the placebo group (RR, 0.88; 95% CI, 0.50-1.54; P=0.66). No trend towards clinical benefit was observed with abciximab at 1 year in any subgroup analysed.

CONCLUSION

In patients with a low-to-intermediate risk profile undergoing PCI after pre-treatment with a 600 mg clopidogrel for at least 2 h, the use of abciximab offers no additional clinical benefit at 1 year.