Critical Analysis of Thrombocytopenia Associated With Glycoprotein IIb/IIIa Inhibitors and Potential Role of Zalunfiban, a Novel Small Molecule Glycoprotein Inhibitor, in Understanding the Mechanism(s)

Thrombocytopenia is a rare but serious complication of the intravenous glycoprotein IIb/IIIa (GPIIb/IIIa; integrin αIIbβ3) receptor inhibitors (GPIs), abciximab, eptifibatide, and tirofiban. The thrombocytopenia ranges from mild (50 000-100 000 platelets/μL), to severe (20 000 to <50 000/μL), to profound (<20 000/μL). Profound thrombocytopenia appears to occur in <1% of patients receiving their first course of therapy. Thrombocytopenia can be either acute (<24 hours) or delayed (up to ~14 days). Both hemorrhagic and thrombotic complications have been reported in association with thrombocytopenia. Diagnosis requires exclusion of pseudothrombocytopenia and heparin-induced thrombocytopenia. Therapy based on the severity of thrombocytopenia and symptoms may include drug withdrawals and treatment with steroids, intravenous IgG, and platelet transfusions. Abciximab-associated thrombocytopenia is most common and due to either preformed antibodies or antibodies induced in response to abciximab (delayed). Readministration of abciximab is associated with increased risk of thrombocytopenia. Evidence also supports an immune basis for thrombocytopenia associated with the 2 small molecule GPIs. The latter bind αIIbβ3 like the natural ligands and thus induce the receptor to undergo major conformational changes that potentially create neoepitopes. Thrombocytopenia associated with these drugs is also immune-mediated, with antibodies recognizing the αIIbβ3 receptor only in the presence of the drug. It is unclear whether the antibody binding depends on the conformational change and whether the drug contributes directly to the epitope. Zalunfiban, a second-generation subcutaneous small molecule GPI, does not induce the conformational changes; therefore, data from studies of zalunfiban will provide information on the contribution of the conformational changes to the development of GPI-associated thrombocytopenia.

Tirofiban-induced thrombocytopenia

Tirofiban is a small non-peptide ligand-mimetic Glycoprotein (GP) IIb/IIIa inhibitor which can reversibly bind to the arginine-glycine-aspartic acid (RGD) recognition site of GP IIb/IIIa to prevent platelet aggregation. It reduces the incidence of thrombotic cardiovascular events in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). Although generally considered safe, tirofiban has been reported to be associated with thrombocytopenia in several case reports and clinical trials. The pathogenesis for this adverse reaction is not entirely understood, is thought to be due to immune-mediated reaction. This side effect caused by tirofiban is especially concerning given how frequently it is used in the practice of contemporary cardiovascular care. The present review provides an overview of the pathophysiology, clinical presentation, management, and risk factors associated with tirofiban-induced thrombocytopenia.

Current and Future Insights for Optimizing Antithrombotic Therapy to Reduce the Burden of Cardiovascular Ischemic Events in Patients with Acute Coronary Syndrome

The pharmacological treatment strategies for acute coronary syndrome (ACS) in recent years are constantly evolving to develop more potent antithrombotic agents, as reflected by the introduction of more novel P2Y₁₂ receptor inhibitors and anticoagulants to reduce the ischemic risk among ACS patients. Despite the substantial improvements in the current antithrombotic regimen, a noticeable number of ACS patients continue to experience ischemic events. Providing effective ischemic risk reduction while balancing bleeding risk remains a clinical challenge. This updated review discusses the currently approved and widely used antithrombotic agents and explores newer antithrombotic treatment strategies under development for the initial phase of ACS.

Safety and efficacy of a platelet glycoprotein Ib inhibitor for patients with non-ST segment elevation myocardial infarction: A phase Ib/IIa study

STUDY OBJECTIVE

This study aimed to determine the safety and efficacy of a novel GP Ib receptor inhibitor in patients with non-ST segment elevation myocardial infarction (NSTEMI) undergoing percutaneous coronary intervention (PCI).

DESIGN AND SETTING

Multicenter, randomized, double-blind, placebo-controlled, dose-escalating, phase Ib-IIa clinical trial. Eligible patients were randomly assigned to the low-dose (n=20, 2 IU/60 kg), moderate-dose (n=20, 3 IU/60 kg), or high-dose anfibatide group (n=20, 5 IU/60 kg), or the placebo group (n=30). Anfibatide was administered for up to 48 hours along with standard aspirin and clopidogrel therapy.

PATIENTS

Ninety patients with NSTEMI who underwent PCI at six academic hospitals in China.

MEASUREMENTS AND MAIN RESULTS

All three doses of anfibatide showed dose-dependent antiplatelet activity as measured by ex vivo platelet aggregation at 5 minutes, 24 hours, and 48 hours during infusion, and 4 hours post-infusion compared with placebo. Higher inhibition of platelet aggregation occurred in all anfibatide groups compared with the placebo group. The post-procedural TIMI grade flow, myocardial blush grade, and corrected TIMI frame count were not significantly different among the four groups. Thirty-day mortality, non-fatal myocardial infarction, and major bleeding were rare and comparable between patients who received anfibatide and placebo. There was no significant difference in the platelet count among the groups during follow-up.

CONCLUSIONS

This study shows that intravenous administration of the platelet receptor GP Ib antagonist anfibatide is feasible and safe to inhibit platelet aggregation without increasing the risk of bleeding and thrombocytopenia in patients with NSTEMI undergoing PCI.

Pharmacokinetics, pharmacodynamics, and tolerability of subcutaneous administration of a novel glycoprotein IIb/IIIa inhibitor, RUC-4, in patients with ST-segment elevation myocardial infarction

BACKGROUND

Pre-hospital platelet inhibition in patients with ST-segment elevation myocardial infarction (STEMI) may improve outcomes. RUC-4 is a novel, second-generation glycoprotein IIb/IIIa inhibitor designed for first-point-of-medical-contact treatment for STEMI by subcutaneous injection.

AIMS

The open-label, phase 2A, CEL-02 trial aimed to assess the pharmacodynamics (PD), pharmacokinetics (PK), and tolerability of RUC-4 in STEMI patients undergoing primary PCI (pPCI).

METHODS

A total of 27 STEMI patients received a weight-adjusted subcutaneous injection of RUC-4 before pPCI in escalating doses (0.075 mg/kg [n=8], 0.090 mg/kg [n=9], or 0.110 mg/kg [n=10]).

RESULTS

The primary PD endpoint of high-grade (≥77%) inhibition of the VerifyNow iso-TRAP assay at 15 minutes was met in 3/8, 7/8, and 7/8 patients in the three cohorts with a dose-response relationship (mean inhibition [min - max] of 77.5% [65.7%-90.6%], 87.5% [73.8%-93.1%], and 91.7% [76.4%-99.3%], respectively; ptrend=0.002). Fifty percent (50%) inhibition remained after 89.1 (38.0-129.7), 104.2 (17.6-190.8), and 112.4 (19.7-205.0) minutes. Injection site reactions or bruising were observed in 1 (4%) and 11 (41%) patients, respectively. Mild access-site haematomas occurred in 6 (22%), and severe access-site haematomas occurred in 2 patients (7%). No thrombocytopaenia was observed within 72 hours post dose.

CONCLUSIONS

In patients with STEMI, a single subcutaneous dose of RUC-4 at 0.075, 0.090, and 0.110 mg/kg showed dose-response high-grade inhibition of platelet function within 15 minutes.

Efficacy and safety of abciximab versus tirofiban in addition to ticagrelor in STEMI patients undergoing primary percutaneous intervention

Platelet glycoprotein IIb/IIIa inhibitors (GPIs) have been part of the adjuvant treatment of acute coronary syndrome for years. However, real-life data regarding the efficacy and safety of GPIs under the current indications are lacking in the setting of potent platelet inhibition. The objectives were to assess the efficacy and safety of abciximab versus tirofiban in patients with ST-elevation acute myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI) and pretreated with ticagrelor, and to identify independent predictor factors of efficacy, bleeding and platelet drop. Three hundred sixty-two patients were divided by GPI administered. Clinical, laboratory, angiographic and outcome characteristics were compared. The primary objective was a composite efficacy endpoint (death from any cause, nonfatal myocardial infarction and nonfatal stroke) at 30 days. The secondary objectives were its individual components, safety (bleeding) and the impact on platelet count during hospital stay. The composite efficacy endpoint was similar in the abciximab and tirofiban groups (6.1% vs 7.3%; p = .632). There were also no differences in cardiovascular death (2.5% vs 2.4%; p = .958), nonfatal myocardial infarction (3% vs 4.3%; p = .521) and nonfatal stroke (0.5% vs 1.8%; p = .332). Tirofiban administration was associated with a higher incidence of bleeding (11.6% vs 22%; p = .008) with no differences in BARC ≥ 3b bleeding (3.6 vs 2.5%; p = .760). In STEMI patients undergoing PPCI with ticagrelor, abciximab and tirofiban had similar rates in the composite efficacy endpoint at 30 days. The 30-day bleeding rate was significantly higher in the tirofiban group. Tirofiban administration was an independent predictor of both bleeding and platelet count drop.

Why thromboembolism occurs in some patients with thrombocytopenia and treatment strategies

Platelets play such an important role in the process of thrombosis that patients with thrombocytopenia generally have an increased risk of bleeding. However, abnormal thrombotic events can sometimes occur in patients with thrombocytopenia, which is unusual and inexplicable. The treatments for thrombocytopenia and thromboembolism are usually contradictory. This review introduces the mechanisms of thromboembolism in patients with different types of thrombocytopenia and outlines treatment recommendations for the prevention and treatment of thrombosis. According to the cause of thrombocytopenia, this article addresses four etiologies, including inherited thrombocytopenia (Myh9-related disease, ANKRD26-associated thrombocytopenia, Glanzmann thrombasthenia, Bernard-Soulier syndrome), thrombotic microangiopathy (thrombotic thrombocytopenic purpura, atypical hemolytic uremic syndrome, hemolytic uremic syndrome, Hemolysis Elevated Liver enzymes and Low Platelets syndrome, disseminated intravascular coagulation), autoimmune-related thrombocytopenia (immune thrombocytopenic purpura, antiphospholipid syndrome, systemic lupus erythematosus), and acquired thrombocytopenia (Infection-induced thrombocytopenia and drug-induced thrombocytopenia, heparin-induced thrombocytopenia). We hope to provide more evidence for clinical applications and future research.

Recurrent stent thrombosis in a patient with acute coronary syndrome and ischemic colitis: between life-threatening thrombosis and life-threatening bleeding

Complete blood count should always be considered to tailor diagnosis and appropriate management in patients with acute ischemic heart disease. We present a challenging case of recurrent acute coronary syndrome, in the context of very high thrombotic risk due to concomitant inflammatory disease. Although no general guidelines exist for the switch between antiplatelet agents, particularly in the acute setting, in specific cases, the availability of different orally- and i.v.-acting agents and platelet function tests may allow to discriminate among multiple possible mechanisms of drug failure or side effects in the individual patient.

Dual anti-platelet therapy following percutaneous coronary intervention in a population of patients with thrombocytopenia at baseline: a meta-analysis

Background

In this meta-analysis, we aimed to systematically compare the post percutaneous coronary interventional (PCI) adverse bleeding events, stent thrombosis, stroke and other cardiovascular outcomes in a population of patients with and without thrombocytopenia at baseline who were followed up on dual antiplatelet therapy (DAPT).

Methods

Relevant English language articles which were published before June 2019 were retrieved from MEDLINE, http://www.ClinicalTrials.com, EMBASE, Cochrane central, and Google scholar briefly using specific terms such as percutaneous coronary intervention or dual antiplatelet therapy, and thrombocytopenia. All the participants were followed up on DAPT following discharge. Specific endpoints including bleeding events, stent thrombosis, stroke and other adverse cardiovascular events were assessed. The latest version of the RevMan software was used for the statistical assessment. Odd ratios (OR) with 95% confidence intervals (CI) based on a fixed or a random statistical model were used to represent the data graphically.

Results

A total number of 118,945 participants (from 8 studies) were included with 37,753 suffering from thrombocytopenia at baseline. Our results showed post procedural bleeding (OR: 1.89, 95% CI: 1.16–3.07; P = 0.01), access site bleeding (OR: 1.66, 95% CI: 1.15–2.39; P = 0.006), intra-cranial bleeding (OR: 1.78, 95% CI: 1.30–2.43; P = 0.0003), gastro-intestinal bleeding (OR: 1.44, 95% CI: 1.14–1.82; P = 0.002) and any major bleeding (OR: 1.67, 95% CI: 1.42–1.97; P = 0.00001) to be significantly higher in thrombocytopenic patients treated with DAPT after PCI. Total stroke (OR: 1.45, 95% CI: 1.18–1.78; P = 0.0004) specifically hemorrhagic stroke (OR: 1.67, 95% CI: 1.30–2.14; P = 0.0001) was also significantly higher in these patients with thrombocytopenia at baseline. All-cause mortality and major adverse cardiac events were also significantly higher. However, overall total stent thrombosis (OR: 1.18, 95% CI: 0.90–1.55; P = 0.24) including definite and probable stent thrombosis were not significantly different compared to the control group.

Conclusions

According to the results of this analysis, DAPT might have to be cautiously be used following PCI in a population of patients with thrombocytopenia at baseline due to the significantly higher bleeding rate including gastro-intestinal, intra-cranial bleeding and hemorrhagic stroke. Hence, special care might have to be taken when considering anti-platelet agents following PCI in these high risk patients. However, considering the present limitations of this analysis, this hypothesis will have to be confirmed in future trials.

Incidence, Predictors, and Outcomes of Acquired Thrombocytopenia After Percutaneous Coronary Intervention: A Pooled, Patient-Level Analysis of the CHAMPION Trials (Cangrelor Versus Standard Therapy to Achieve Optimal Management of Platelet Inhibition)

BACKGROUND

The influence of cangrelor on the incidence and outcomes of post-percutaneous coronary intervention (PCI) thrombocytopenia is not defined. We aimed to explore the incidence, predictors, and clinical impact of thrombocytopenia after PCI in cangrelor-treated patients.

METHODS AND RESULTS

This was a pooled, patient-level analysis of the CHAMPION trials (Cangrelor Versus Standard Therapy to Achieve Optimal Management of Platelet Inhibition), which compared cangrelor with clopidogrel for prevention of thrombotic complications during and after PCI. Acquired thrombocytopenia was defined as either a drop in platelet count to <100 000 after PCI or a drop of >50% between baseline and a follow-up. The main efficacy outcome was major adverse cardiac events. The primary safety outcome was noncoronary artery bypass grafting-related Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries-defined severe bleeding at 48 hours. Patients (23 783) were enrolled, and 3009 (12.7%) received a GPI (glycoprotein IIb/IIIa inhibitor). Acquired thrombocytopenia occurred in 200 patients (0.8%). The adjusted rate of major adverse cardiovascular events at 48 hours was significantly higher in patients who developed thrombocytopenia compared with those who did not (odds ratio, 3.00; 95% confidence interval, 1.89-4.69; P<0.001), as was major bleeding (odds ratio, 14.71; 95% confidence interval, 5.96-36.30; P<0.001). GPI use was the strongest independent predictor of acquired thrombocytopenia (odds ratio, 2.93; 95% confidence interval, 2.15-3.97; P<0.0001). There was no difference in the rate of acquired thrombocytopenia in patients randomized to cangrelor or clopidogrel.

CONCLUSIONS

Acquired thrombocytopenia after PCI is strongly associated with substantial early morbidity and mortality, as well as major bleeding. GPI use is a significant predictor of thrombocytopenia. Cangrelor is not associated with acquired thrombocytopenia, and its clinical efficacy and safety is consistent irrespective of thrombocytopenia occurrence.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifiers: NCT00305162, NCT00385138, and NCT01156571.

Tirofiban-Induced Thrombocytopenia Occurring with Crohn’s Disease

A 69-year-old man, with severe refractory Crohn's disease, presented with acute coronary syndrome that required angioplasty. He developed severe tirofiban-induced thrombocytopenia (TIT) heralded by type I allergic reaction that required steroids and a combination of antihistamine H1 and antihistamine H2 for symptomatic management. The thrombocytopenia spontaneously resolved uneventfully in 48 hours thereafter. This case report suggests a possible association between TIT and inflammatory bowel disease. Therefore, strict monitoring of the platelet count is required in patients who develop allergic reactions to tirofiban.

The effect of targeted temperature management on coagulation parameters and bleeding events after out-of-hospital cardiac arrest of presumed cardiac cause

AIMS

Targeted temperature management (TTM) is part of the standard treatment of comatose patients after out-of-hospital cardiac arrest (OHCA) to attenuate neurological injury. In other clinical settings, hypothermia promotes coagulopathy leading to an increase in bleeding and thrombosis tendency. Thus, concern has been raised as to whether TTM can be applied safely, as acute myocardial infarction requiring primary percutaneous coronary intervention (PCI) with the need of effective antiplatelet therapy is frequent following OHCA. This study investigated the influence of TTM at 33 or 36°C on various laboratory and coagulation parameters.

METHODS AND RESULTS

In this single-center predefined substudy of the TTM trial, 171 patients were randomized to TTM at either 33 or 36°C in the postresuscitation phase. The two subgroups were compared regarding standard laboratory coagulation parameters, thrombelastography (TEG), bleeding, and stent thrombosis events. Platelet counts were lower in the TTM33-group compared to TTM36 (p=0.009), but neither standard coagulation nor TEG-parameters showed any difference between the groups. TEG revealed a normocoagulable state in the majority of patients, while approximately 20% of the population presented as hypercoagulable. Adverse events included 38 bleeding events, one stent thrombosis, and one reinfarction, with no significant difference between the groups.

CONCLUSIONS

There was no evidence supporting the assumption that TTM at 33°C was associated with impaired hemostasis or increased the frequency of adverse bleeding and thrombotic events compared to TTM at 36°C. We found that TTM at either temperature can safely be applied in the postresuscitation phase after acute myocardial infarction and primary PCI.