Safety and efficacy of platelet glycoprotein VI inhibition in acute ischaemic stroke (ACTIMIS): a randomised, double-blind, placebo-controlled, phase 1b/2a trial

Platelets in vascular inflammation: fire-fighters or pyromaniacs?

PURPOSE OF REVIEW

In this review, we aim to highlight recent insights into the mechanisms through which platelets contribute to vascular inflammation. We will discuss how platelets interact with other cellular players in the vascular milieu, their role in shaping inflammatory responses, and the potential therapeutic implications of targeting platelet function in inflammatory vascular diseases.

RECENT FINDINGS

Platelets are essential components in the processes of hemostasis and thrombosis. Their role is now widely acknowledged as far more complex than merely acting as "band-aids" or helping to "clog a pipe". Platelets are now recognized as crucial mediators in inflammatory reactions, particularly in various diseases of the vasculature, where they contribute to the onset and progression of injury. Through their interactions with leukocytes, vascular cells, and by supporting the coagulation cascade, platelets are able to finely regulate the extent and intensity of vascular damage.

SUMMARY

Recent findings underscore the remarkable diversity and functionality of platelets in vascular diseases. Mechanistic studies in preclinical models reveal promising therapeutic opportunities, which require further validation before being translated into clinical practice.

Development and validation of a multi-omics hemorrhagic transformation model based on hyperattenuated imaging markers following mechanical thrombectomy

This study aimed to develop a predictive model integrating clinical, radiomics, and deep learning (DL) features of hyperattenuated imaging markers (HIM) from computed tomography scans immediately following mechanical thrombectomy (MT) to predict hemorrhagic transformation (HT). A total of 239 patients with HIM who underwent MT were enrolled, with 191 patients (80%) in the training cohort and 48 patients (20%) in the validation cohort. Additionally, the model was tested on an internal prospective cohort of 49 patients. A total of 1834 radiomics features and 2048 DL features were extracted from HIM images. Statistical methods, such as analysis of variance, Pearson's correlation coefficient, principal component analysis, and least absolute shrinkage and selection operator, were used to select the most significant features. A K-Nearest Neighbor classifier was employed to develop a combined model integrating clinical, radiomics, and DL features for HT prediction. Model performance was evaluated using metrics such as accuracy, sensitivity, specificity, receiver operating characteristic curves, and area under curve (AUC). In the training, validation, and test cohorts, the combined model achieved AUCs of 0.926, 0.923, and 0.887, respectively, outperforming other models, including clinical, radiomics, and DL models, as well as hybrid models combining subsets of features (Clinical + Radiomics, DL + Radiomics, and Clinical + DL) in predicting HT. The combined model, which integrates clinical, radiomics, and DL features derived from HIM, demonstrated efficacy in noninvasively predicting HT. These findings suggest its potential utility in guiding clinical decision-making for patients with MT.

The critical role of platelets in venous thromboembolism: Pathogenesis, clinical status, and emerging therapeutic strategies

Venous thromboembolism (VTE), encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), is a complex vascular disorder with high morbidity and mortality, driven by Virchow's Triad: blood stasis, hypercoagulability, and endothelial injury. VTE is now recognized as an inflammatory process involving multiple components. Platelets are involved in the process of VTE, contributing to thrombosis initiation, progression, resolution and recurrence through coagulation activation, and interactions with immune and endothelial cells. Anticoagulation remains the cornerstone of VTE treatment; however, antiplatelet agents like aspirin have demonstrated therapeutic potential, particularly following major orthopedic surgeries. Furthermore, emerging platelet-targeted therapies and biomarkers offer new opportunities for improving VTE diagnosis and treatment. This review explores the evolving role of platelets in VTE pathophysiology, assesses current antiplatelet strategies, and highlights novel therapeutic approaches. Advancing platelet research in VTE may lead to safer, more effective interventions, optimizing outcomes for patients with this life-threatening condition.

In situ protein corona-camouflaged supramolecular assemblies remodel thrombotic microenvironment for improved arterial homeostasis

Arterial thrombosis is commonly accompanied by poor recanalization and high recurrence, typically caused by a fibrinolysis-resistant microenvironment. We identify elevated levels of plasminogen activator inhibitor-1 (PAI-1) and, notably, its strong correlation with inflammation in arterial thrombosis. To address this, small molecular inhibitors of PAI-1 and inflammation are used as bioregulators to restore vascular homeostasis. We design a carrier-free supramolecular system based on the bioregulators-tuned self-assembly of a near-infrared thrombus probe, which preferentially forms protein corona in situ to enhance plasma stability. Under acidic conditions and increased shear stress, the supramolecular assemblies disintegrate, enabling site-specific cargo release. In vivo, the probe accumulates 22.8-fold more in the thrombotic than contralateral artery. Functionally, this nanomedicine improves outcomes in mice with carotid artery thrombosis and chronic cerebral ischemia. Mechanistically, it down-regulates NF-κB signaling, inhibits NETosis and glycolysis, and up-regulates cGMP-mediated signaling, thereby alleviating inflammation and promoting fibrinolysis. This study offers an innovative codelivery strategy using supramolecular assemblies to advance therapies for arterial thrombosis.

Recent Advances in Immunothrombosis and Thromboinflammation

Inflammation and thrombosis are traditionally considered two separate entities of acute host responses to barrier breaks. While inciting inflammatory responses is a prerequisite to fighting invading pathogens and subsequent restoration of tissue homeostasis, thrombus formation is a crucial step of the hemostatic response to prevent blood loss following vascular injury. Though originally designed to protect the host, excessive induction of either inflammatory signaling or thrombus formation and their reciprocal activation contribute to a plethora of disorders, including cardiovascular, autoimmune, and malignant diseases. In this state-of-the-art review, we summarize recent insights into the intricate interplay of inflammation and thrombosis. We focus on the protective aspects of immunothrombosis as well as evidence of detrimental sequelae of thromboinflammation, specifically regarding recent studies that elucidate its pathophysiology beyond coronavirus disease 2019 (COVID-19). We introduce recently identified molecular aspects of key cellular players like neutrophils, monocytes, and platelets that contribute to both immunothrombosis and thromboinflammation. Further, we describe the underlying mechanisms of activation involving circulating plasma proteins and immune complexes. We then illustrate how these factors skew the inflammatory state toward detrimental thromboinflammation across cardiovascular as well as septic and autoimmune inflammatory diseases. Finally, we discuss how the advent of new technologies and the integration with clinical data have been used to investigate the mechanisms and signaling cascades underlying immunothrombosis and thromboinflammation. This review highlights open questions that will need to be addressed by the field to translate our mechanistic understanding into clinically meaningful therapeutic targeting.

Predicting reperfusion injury and functional status after stroke using blood biomarkers: the STROKELABED study

BACKGROUND

Ischemic stroke is a leading cause of disability and mortality, particularly among the elderly. Recanalization therapies, including thrombolysis and thrombectomy, are essential for restoring blood flow and saving ischemic tissue. However, these interventions may trigger reperfusion injury, worsening inflammation and tissue damage, leading to blood-brain-barrier (BBB) disruption, cerebral edema (CE) and adverse functional outcomes. Here we propose a model integrating circulating inflammatory biomarkers with metabolomic and lipoproteomic data able to help clinicians in predicting BBB disruption, CE at 24 h post stroke onset and poor post-stroke functional outcome (Modified Rankin Scale (mRS > 2).

METHODS

Peripheral blood from 87 patients was collected at admission and 24 h after stroke onset. The logistic LASSO regression algorithm was employed to identify the optimal combination of metabolites, lipoprotein-related parameters and circulating biomarkers to discriminate the groups of interest at the two time-points.

RESULTS

Multivariable logistic regression models included as covariates: age, sex, onset-to-treatment time, treatment with lipid-lowering medications before stroke, history of heart failure, history of atrial fibrillation and history of diabetes. The regression models showed that methionine, acetate, GlyA and MMP-2 were significant predictors of BBB disruption, methionine, acetate, TIMP-1 and CXCL-10 predicted 24-hours CE, whereas a poor functional outcome at three months was predicted by CXCL-10, IL-12 and LDL-5.

CONCLUSIONS

As stroke has a heterogeneous pathophysiology, a personalized approach based on biomarkers, as presented in this study, shown to be effective in tackling patient individual risk and could help in developing novel diagnostic, prognostic, and therapeutic neuroprotective strategies for the management of stroke patients.

New targets for antithrombotic medications: seeking to decouple thrombosis from hemostasis

Arterial and venous thromboses are the leading causes of morbidity and mortality worldwide. Numerous antithrombotic agents are currently available with antiplatelet, thrombolytic/fibrinolytic, and anticoagulant activity. However, all the currently available antithrombotic agents carry a risk of bleeding that often prevents their use. This unfavorable risk-benefit profile is particularly challenging for patients with cancer-associated venous thromboembolism, patients with atrial fibrillation at a high risk of bleeding, and patients with end-stage renal disease. Patients with ischemic stroke and acute coronary syndromes have not yet found a favorable risk-benefit profile with anticoagulant therapy to help reduce the residual thromboembolic risk that remains after antiplatelet and lipid therapy. Two emerging classes of antithrombotic agents, factor (F)XI or activated factor Ⅺ (FⅪa) inhibitors and glycoprotein VI inhibitors, have shown promise in their ability to prevent pathologic thrombosis without increasing the risk of hemostatic-related bleeding in phase 2 studies. Among the FⅪ/FXIa inhibitors of coagulation, a parenterally administered monoclonal antibody (abelacimab) and 2 orally administered small molecule inhibitors (asundexian, milvexian) are collectively being studied in patients with atrial fibrillation, cancer-associated venous thromboembolism, acute coronary syndrome, and ischemic stroke. One parenterally administered glycoprotein VI antiplatelet agent (glenzocimab) is currently being studied in patients with ischemic stroke. If shown to be efficacious and safe in ongoing phase 3 studies, both classes of emerging antithrombotic agents have the potential to greatly improve outcomes for patients with challenging thrombotic conditions.

Emerging Targets, Novel Directions, and Innovative Approaches in Thrombosis Therapy

In clinical practice, antiplatelet, anticoagulant and fibrinolytic drugs are the mainstay of thrombosis treatment, but their potential bleeding side effects limit their widespread use. Therefore, modifying these existing drugs or developing new therapies that mitigate bleeding risks while maintaining their efficacy and utilization is necessary. Since the critical role of platelets in thrombosis is closely related to their cell surface receptors, intracellular signaling pathways and metabolism, current research focuses on these three major classes of platelet targets to develop new antithrombotic drugs. The coagulation cascade has always been the main target of anticoagulant drugs, but since the role of molecules of the contact system is more critical in thrombosis than in hemostasis, molecules targeting the contact system, such as FXIa and FXIIa, have become the main direction of anticoagulant drug research at present. Moreover, since the inflammatory response has been found to be significantly associated with thrombosis in recent years, the development of drugs that target inflammatory pathways, such as inflammasome, has also become a hot topic. This article provides a detailed description of these targets or drug formulations that are currently being investigated, including their mode of action and antithrombotic efficiency, and also points out their existing shortcomings. Moreover, antithrombotic nanomedicines can achieve precise release of drugs, which can greatly improve the thrombolytic efficiency and reduce side effects. In conclusion, this review focuses on summarizing the current new targets and new methods of antithrombotic drug research, hoping to provide a little reference for future related research.

Predictors of poor outcome in acute stroke patients with posterior cerebral artery occlusion and medical management

BACKGROUND AND AIMS

The clinical evolution of acute ischemic stroke patients with isolated proximal posterior cerebral artery (PCA) occlusion treated with medical management alone has been poorly described. We aimed to determine the clinical and radiological factors associated with poor functional outcome in this population.

METHODS

We conducted a multicenter international retrospective study of consecutive stroke patients with isolated occlusion of the first (P1) or second (P2) segment of PCA admitted within 6 h from symptoms onset in 26 stroke centers in France, Switzerland, and the United States, treated with the best medical management alone. Poor functional outcome was defined as a modified Rankin scale (mRS) ⩾2 at 3 months or no return to pre-stroke mRS. The associations between pretreatment variables and poor outcome were studied in univariable and then multivariable analyses, as well as the association between poor outcome and key follow-up radiological variables.

RESULTS

Overall, 585 patients were included. The median age was 74 years (interquartile range (IQR) = 63-83), median National Institutes of Health Stroke Scale (NIHSS) was 6 (3-10), 80% received intravenous thrombolysis (IVT), and 22% and 78% had P1 and P2 occlusions, respectively. Poor outcome occurred in 56% of patients. In multivariable analysis focusing on pretreatment variables, age (adjusted odds ratio (OR) = 1.12 per 5-year increase [95% confidence interval (CI) = 1.05-1.20]; p = 0.001), NIHSS score (aOR = 1.12 per each point increase [1.08-1.18]; p < 0.001), infarct volume (aOR = 1.16 per 5 mL increase [1.07-1.25]; p < 0.001), and the lack of IVT use (aOR = 1.79 [1.10-2.94], p = 0.020) were independently associated with poor outcome. Regarding 24-h follow-up radiological variables, complete recanalization (defined as no clot in the vascular tree at or beyond the primary occlusive lesion, aOR = 0.37 [95% CI = 0.21-0.65], p < 0.001) and parenchymal hematoma occurrence (aOR = 2.37 [95% CI = 1.01-5.56], p = 0.048) were independently associated with poor 3-month outcome.

CONCLUSIONS

Poor outcome occurred in more than half of medically treated PCA-related acute stroke patients. Facilitating IVT use may improve functional outcome. Therapeutic approaches aimed at enhancing recanalization and reducing hemorrhagic transformation need to be studied in clinical trials.

Comparative Effects of Glenzocimab and Eptifibatide on Bleeding Severity in 2 Mouse Models of Intracranial Hemorrhage

BACKGROUND

Antiplatelet drugs represent potential candidates for protecting the penumbral microcirculation during cerebral ischemia and improving the benefits of arterial recanalization in ischemic stroke. Yet while the efficacy of such adjuvant strategies has been shown to be highly time dependent, antiplatelet therapy at the acute phase of ischemic stroke cannot be envisioned until the diagnosis of stroke and its ischemic nature have been confirmed because of the presumed risk of worsening bleeding in case of intracranial hemorrhage (ICH). Here, we investigated this risk for 2 antiplatelet drugs currently being tested in clinical trials for ischemic stroke, glenzocimab and eptifibatide, in 2 mouse models of ICH.

METHODS AND RESULTS

The severity of ICH was assessed in mice humanized for glycoprotein VI treated or not with glenzocimab or eptifibatide at effective dose, in a model of primary ICH caused by unilateral striatal injection of collagenase type VII, and in a model of hyperglycemia-induced hemorrhagic transformation of cerebral ischemia-reperfusion injury. Glenzocimab had no impact on bleeding severity in either model of ICH. Conversely, eptifibatide caused a significant increase in intracranial bleeding in both models, and a drastic increase in death after hyperglycemia-induced hemorrhagic transformation of cerebral ischemia-reperfusion injury.

CONCLUSIONS

Unlike eptifibatide, glenzocimab is safe in the setting of ICH. These results suggest that glenzocimab could be administered upon suspicion of ischemic stroke, before assessment of its ischemic nature, thus opening the way to hastening of treatment initiation.

Interplay between platelets and coagulation: from protective haemostasis to pathological arterial thrombosis

Haemostasis refers to the physiological process aimed at repairing vessel injury and preventing bleeding. It involves four interlinked stages culminating in the formation of a platelet-fibrin haemostatic plug that is eventually dissolved once the vessel heals. In contrast, arterial thrombosis is a pathological condition resulting from atheroma exposure, triggering the formation of a platelet-rich thrombus that may obstruct blood flow, leading to the clinical manifestations of ischaemic cardiovascular disease. The following review will provide a comprehensive overview of the finely regulated endogenous antithrombotic mechanisms responsible for maintaining the haemostatic balance and preventing intravascular thrombosis. Thereafter, it will further detail the different stages and mechanisms governing the intricate interplay between the vessel, platelets, and the coagulation cascade in haemostasis, highlighting the most recent advances in platelet biology and function, to further elucidate the differential traits and players contributing to pathological arterial thrombus growth. The review will also delve into the impact of emerging cardiovascular risk factors on tilting the haemostatic balance towards a pro-thrombotic state, thereby increasing the patient's vulnerability to thrombotic events. Finally, it will underscore the importance of early screening for subclinical atherosclerosis through advanced imaging technologies capable of quantifying plaque burden and metabolic activity since they may set the stage for an increased thrombotic risk. Implementing proactive interventions to halt atherosclerosis progression or inducing its regression at early stages is crucial for preserving haemostasis and reducing the likelihood of ischaemic atherothrombotic disease.

Pharmacotherapeutic options for coronary thrombosis treatment: where are we today?

INTRODUCTION

Advances in pharmacotherapy for coronary thrombosis treatment and prevention have transformed the clinical outcomes of patients with coronary artery disease but increased the complexity of therapeutic decision-making. Improvements in percutaneous coronary intervention techniques and stent design have reduced the incidence of thrombotic complications, which consequently has increased the challenge of adequately powering clinical trials of novel antithrombotic strategies for efficacy outcomes. Knowledge of the pathophysiology of coronary thrombosis and the characteristics of antithrombotic drugs can help with therapeutic decisions.

AREAS COVERED

This review covers the pathophysiology of coronary thrombosis and the mechanisms of action of drugs developed for its treatment, provides an overview of the key issues in decision-making, and highlights key areas for further work in order to guide clinicians on how to individualize risk management and address gaps in the evidence base.

EXPERT OPINION

Individualization of antithrombotic therapy regimens has become a vital part of optimizing risk management in people with coronary thrombosis. A critical appraisal of the strengths and limitations of available drugs and the evidence supporting the use of different antithrombotic combinations is intended to provide direction to clinicians and point the way toward further improvements in pharmacotherapy for coronary thrombosis treatment and prevention.

Interfacility Transfer for Thrombectomy: A Promising Therapeutic Window

Currently, most acute ischemic stroke patients presenting with a large vessel occlusion are first evaluated at a nonthrombectomy-capable center before transfer to a comprehensive stroke center that performs thrombectomy. Interfacility transfer is a complex process that requires extensive coordination between the referring, transporting, and receiving facilities. As a result, long delays are common, contributing to poor clinical outcomes. In this review, we summarize the accumulating literature about the clinical as well as radiological-infarct growth, collateral change, arterial recanalization, and hemorrhagic transformation-changes during interfacility transfer for thrombectomy. Recent evidence shows that clinical/radiological changes during transfer are heterogeneous across patients and impact long-term functional outcomes, highlighting the urgent need to optimize care during this time window. We review some of the most promising therapeutic strategies-for example, penumbral protection to reduce infarct growth-that may improve clinical outcome in patients being transferred to thrombectomy-capable centers. Finally, we discuss key methodological considerations for designing clinical trials aimed at reducing infarct growth during transfer.

GPVI-mediated thrombus stabilization of shear-induced platelet aggregates in a microfluidic stenosis

Supraphysiological shear rates (>2000 s-1) amplify von Willebrand factor unfurling and increase platelet activation and adhesion. These elevated shear rates and shear rate gradients also play a role in shear-induced platelet aggregation (SIPA). The primary objective of this study is to investigate the contributions of major binding receptors to platelet deposition and SIPA in a stenotic model. Microfluidic channels with stenotic contractions ranging from 0% to 75% are fabricated and coated with human type I collagen at 100 μg/mL. Fresh human blood is reconstituted to 40% hematocrit and treated to stain platelets. Platelet receptors αIIbβ3, GPIb, or GPVI are blocked with inhibitory antibodies or proteins to reduce platelet function under flow at 500, 1000, 5000, or 10,000 s-1 over 5 min of perfusion. Additional validation experiments are performed by dual-blocking receptors and performing coagulability testing by rotational thromboelastometry. Control samples exhibit SIPA correlating to increasing shear rate and increasing stenotic contraction. Inhibition of αIIbβ3 or GPIb receptors causes a nearly total reduction in platelet adhesion and a loss of aggregation at >1000 s-1. GPVI inhibition does not notably reduce platelet adhesion at 500 or 1000 s-1 but affects microthrombus stability at 5000-10,000 s-1 following aggregation formation in 50%-75% stenotic channels. Inhibition of von Willebrand factor-binding receptors completely blocks adhesion and aggregation at shear rates >1000 s-1. Inhibition of GPVI reduces platelet adhesion at 5000-10,000 s-1 but renders thrombi susceptible to fragmentation. This study yields further insight into mechanisms regulating rapid growth and stabilization of arterial thrombi at supraphysiological shear rates.

[Cerebrolysin and the optimal timing of anticoagulation resumption in stroke: combined post hoc survival analysis of the CEREHETIS trial]

OBJECTIVE

To evaluate the effect of Cerebrolysin on hazard dynamics of hemorrhagic transformation (HT) and identify optimal anticoagulation therapy (AT) resumption timing in stroke patients, stratified by the Hemorrhagic Transformation Index (HTI).

MATERIAL AND METHODS

A post hoc survival analysis of the CEREHETIS trial (ISRCTN87656744) included patients with middle cerebral artery infarctions. The intervention group (IG, n=91) received Cerebrolysin with intravenous thrombolysis (IVT) and standard care, while the control group (CG, n=147) received IVT and standard care alone. Additionally, a validation cohort (VC, n=248) from an observational study was analyzed. Patients were stratified into low-risk (HT=0), high-risk (HTI=1-4), and very-high-risk (HTI=5-8, VC only) groups. Symptomatic HT and any HT within 14 days post-stroke were defined as failure events. Hazard dynamics were modeled using a Gompertz parametric survival approach, with a hazard threshold (0.6% per day) estimating safe AT resumption timing.

RESULTS

Cerebrolysin significantly reduced risk of symptomatic HT (HR 0.245; 95% CI 0.072-0.837; p=0.02) and any HT (HR 0.543; 95% CI 0.297-0.991; p=0.032). The compounding effect peaked on day 1 and persisted through days 7-10 in very-high-risk patients (HTI=5-8). In high-risk patients (HTI=1-4), Cerebrolysin mitigated the compounding effect and reduced hazard levels to the threshold by day 2, compared to days 3-5 in the CG and VC. The hazardous period extended to day 10 in HTI=5-8. In low-risk patients (HTI=0), hazard levels remained below the threshold from day 1, with no measurable impact of Cerebrolysin on HT.

CONCLUSION

AT may be safely resumed within 48 h in low-risk patients (HTI=0), on days 3-5 in high-risk patients (HTI=1-4), and on day 10 in very-high-risk patients (HTI=5-8) without symptomatic HT. Cerebrolysin mitigates the compounding effect, reduces HT risk, and facilitates earlier, safer AT resumption in high-risk patients (HTI=1-4) by day 2 post-stroke, supporting its role in personalized stroke management.

Platelet signaling in immune landscape: comprehensive mechanism and clinical therapy

Platelets are essential for blood clotting and maintaining normal hemostasis. In pathological conditions, platelets are increasingly recognized as crucial regulatory factors in various immune-mediated inflammatory diseases. Resting platelets are induced by various factors such as immune complexes through Fc receptors, platelet-targeting autoantibodies and other platelet-activating stimuli. Platelet activation in immunological processes involves the release of immune activation stimuli, antigen presentation and interaction with immune cells. Platelets participate in both the innate immune system (neutrophils, monocytes/macrophages, dendritic cells (DCs) and Natural Killer (NK) cells and the adaptive immune system (T and B cells). Clinical therapeutic strategies include targeting platelet activation, platelet-immune cell interaction and platelet-endothelial cell interaction, which display positive development prospects. Understanding the mechanisms of platelets in immunity is important, and developing targeted modulations of these mechanisms will pave the way for promising therapeutic strategies.

Ischemia/reperfusion injury in acute human and experimental stroke: focus on thrombo-inflammatory mechanisms and treatments

BACKGROUND

Despite high recanalization rates of > 90% after endovascular thrombectomy (EVT) clinical outcome in around 50% of treated acute ischemic stroke (AIS) patients is still poor. Novel treatments augmenting the beneficial effects of recanalization are eagerly awaited, but this requires mechanistic insights to explain and overcome futile recanalization.

MAIN BODY

At least two mechanisms contribute to futile recanalization after cerebral large vessel occlusions (LVO): (i) the no reflow phenomenon as evidenced by randomly distributed areas without return of blood flow despite reperfusion of large cerebral arteries, and (ii) ischemia/reperfusion (I/R) injury, the paradoxically harmful aspect of blood flow return in transiently ischemic organs. There is accumulating evidence from experimental stroke models that platelets and leukocytes interact and partly obstruct the microvasculature under LVO, and that platelet-driven inflammation (designated thrombo-inflammation) extends into the reperfusion phase and causes I/R injury. Blocking of platelet glycoprotein receptors (GP) Ib and GPVI ameliorated inflammation and I/R injury providing novel therapeutic options. Recently, MRI studies confirmed a significant, up to 40% infarct expansion after recanalization in AIS thereby proofing the existance of I/R injury in the human brain. Moreover, analysis of minute samples of ischemic arterial blood aspirated directly from the pial cerebral collateral circulation under LVO during the routine EVT procedure confirmed platelet activation and platelet-driven leukocyte accumulation in AIS and, thus, the principal transferability of pathophysiological stroke mechanisms from rodents to man. Two recently published clinical phase 1b/2a trials targeted (thrombo-) inflammation in AIS: The ACTIMIS trial targeting platelet GPVI by glenzocimab provided encouraging safety signals in AIS similar to the ApTOLL trial targeting toll-like receptor 4, a central receptor guiding stroke-induced innate immunity. However, both studies were not powered to show clinical efficacy.

CONCLUSIONS

The fact that the significance of I/R injury in AIS has recently been formally established and given the decisive role of platelet-leukocytes interactions herein, new avenues for adjunct stroke treatments emerge. Adjusted study designs to increase the probability of success are of outmost importance and we look forward from what can be learned from the so far unpublished, presumbably negative ACTISAFE and MOST trials.

The humanized platelet glycoprotein VI Fab inhibitor EMA601 protects from arterial thrombosis and ischaemic stroke in mice

BACKGROUND AND AIMS

Glycoprotein VI (GPVI) is a platelet collagen/fibrin(ogen) receptor and an emerging pharmacological target for the treatment of thrombotic and thrombo-inflammatory diseases, notably ischaemic stroke. A first anti-human GPVI (hGPVI) antibody Fab-fragment (ACT017/glenzocimab, KD: 4.1 nM) recently passed a clinical phase 1b/2a study in patients with acute ischaemic stroke and was found to be well tolerated, safe, and potentially beneficial. In this study, a novel humanized anti-GPVI antibody Fab-fragment (EMA601; KD: 0.195 nM) was developed that inhibits hGPVI function with very high potency in vitro and in vivo.

METHODS

Fab-fragments of the mouse anti-hGPVI IgG Emf6.1 were tested for functional GPVI inhibition in human platelets and in hGPVI expressing (hGP6tg/tg) mouse platelets. The in vivo effect of Emf6.1Fab was assessed in a tail bleeding assay, an arterial thrombosis model and the transient middle cerebral artery occlusion (tMCAO) model of ischaemic stroke. Using complementary-determining region grafting, a humanized version of Emf6.1Fab (EMA601) was generated. Emf6.1Fab/EMA601 interaction with hGPVI was mapped in array format and kinetics and quantified by bio-layer interferometry.

RESULTS

Emf6.1Fab (KD: 0.427 nM) blocked GPVI function in human and hGP6tg/tg mouse platelets in multiple assays in vitro at concentrations ≥5 µg/mL. Emf6.1Fab (4 mg/kg)-treated hGP6tg/tg mice showed potent hGPVI inhibition ex vivo and were profoundly protected from arterial thrombosis as well as from cerebral infarct growth after tMCAO, whereas tail-bleeding times remained unaffected. Emf6.1Fab binds to a so far undescribed membrane proximal epitope in GPVI. The humanized variant EMA601 displayed further increased affinity for hGPVI (KD: 0.195 nM) and fully inhibited the receptor at 0.5 µg/mL, corresponding to a >50-fold potency compared with ACT017.

CONCLUSIONS

EMA601 is a conceptually novel and promising anti-platelet agent to efficiently prevent or treat arterial thrombosis and thrombo-inflammatory pathologies in humans at risk.

GP VI-Mediated Platelet Activation and Procoagulant Activity Aggravate Inflammation and Aortic Wall Remodeling in Abdominal Aortic Aneurysm

BACKGROUND

Platelets play an important role in cardiovascular and cerebrovascular diseases. Abdominal aortic aneurysm (AAA) is a highly lethal, atherosclerosis-related disease with characteristic features of progressive dilatation of the abdominal aorta and degradation of the vessel wall, accompanied by chronic inflammation. Platelet activation and procoagulant activity play a decisive role in the AAA pathology as they might trigger AAA development in both mice and humans.

METHODS

The present study investigated the impact of the major platelet collagen receptor GP (platelet glycoprotein) VI in pathophysiological processes underlying AAA initiation and progression. For experimental AAA induction in mice, PPE (porcine pancreatic elastase) and the external PPE model were used.

RESULTS

Genetic deletion of GP VI offered protection of mice against aortic diameter expansion in experimental AAA. Mechanistically, GP VI deficiency resulted in decreased inflammation with reduced infiltration of neutrophils and platelets into the aortic wall. Furthermore, remodeling of the aortic wall was improved in the absence of GP VI, as indicated by reduced MMP (matrix metalloproteinase)-2/9 and OPN (osteopontin) plasma levels and an enhanced α-SMA (α-smooth muscle actin) content within the aortic wall, accompanied by reduced cell apoptosis. Consequently, an elevation in intima/media thickness and elastin content was observed in GP VI-deficient PPE mice, resulting in a significantly reduced aortic diameter expansion and reduced aneurysm incidence. In patients with AAA, enhanced plasma levels of soluble GP VI and fibrin, as well as fibrin accumulation within the intraluminal thrombus might serve as new biomarkers to detect AAA early. Moreover, we hypothesize that GP VI might play a role in procoagulant activity and thrombus stabilization via binding to fibrin.

CONCLUSIONS

In conclusion, our results emphasize the potential need for a GP VI-targeted antiplatelet therapy to reduce AAA initiation and progression, as well as to protect patients with AAA from aortic rupture.

Emerging Adjuvant Thrombolytic Therapies for Acute Ischemic Stroke Reperfusion

Thrombolytic therapies for acute ischemic stroke are widely available but only result in recanalization early enough, to be therapeutically useful, in 10% to 30% of cases. This large gap in treatment effectiveness could be filled by novel therapies that can increase the effectiveness of thrombus clearance without significantly increasing the risk of harm. This focused update will describe the current state of emerging adjuvant treatments for acute ischemic stroke reperfusion. We focus on new treatments that are designed to (1) target different components that make up a stroke thrombus, (2) enhance endogenous fibrinolytic systems, (3) reduce stagnant blood flow, and (4) improve recanalization of distal thrombi and postendovascular thrombectomy.

One immune cell to bind them all: platelet contribution to neurodegenerative disease

Alzheimer's disease (AD) and related dementias (ADRD) collectively affect a significant portion of the aging population worldwide. The pathological progression of AD involves not only the classical hallmarks of amyloid beta (Aβ) plaque buildup and neurofibrillary tangle development but also the effects of vasculature and chronic inflammatory processes. Recently, platelets have emerged as central players in systemic and neuroinflammation. Studies have shown that patients with altered platelet receptor expression exhibit accelerated cognitive decline independent of traditional risk factors. Additionally, platelets from AD patients exhibit heightened unstimulated activation compared to control groups. Platelet granules contain crucial AD-related proteins like tau and amyloid precursor protein (APP). Dysregulation of platelet exocytosis contributes to disease phenotypes characterized by increased bleeding, stroke, and cognitive decline risk. Recent studies have indicated that these effects are not associated with the quantity of platelets present in circulation. This underscores the hypothesis that disruptions in platelet-mediated inflammation and healing processes may play a crucial role in the development of ADRD. A thorough look at platelets, encompassing their receptors, secreted molecules, and diverse roles in inflammatory interactions with other cells in the circulatory system in AD and ADRD, holds promising prospects for disease management and intervention. This review discusses the pivotal roles of platelets in ADRD.

Soluble Glycoprotein VI Levels Assessed Locally within the Extra- and Intracerebral Circulation in Hyper-Acute Thromboembolic Stroke: A Pilot Study

Background: Severe acute ischemic stroke (AIS) is mainly caused by thromboembolism originating from symptomatic carotid artery (ICA) stenosis or in the heart due to atrial fibrillation. Glycoprotein VI (GPVI), a principal platelet receptor, facilitates platelet adherence and thrombus formation at sites of vascular injury such as symptomatic ICA stenosis. The shedding of GPVI from the platelet surface releases soluble GPVI (sGPVI) into the circulation. Here, we aimed to determine whether sGPVI can serve as a local biomarker to differentiate between local atherosclerotic and systemic cardiac thromboembolism in AIS. Methods: We conducted a cohort study involving 105 patients undergoing emergency endovascular thrombectomy (EVT) for anterior circulation stroke. First, sGPVI concentrations were measured in systemic arterial plasma samples collected at the ipsilateral ICA level, including groups with significantly (≥50%) stenotic and non-stenotic arteries. A second sample, taken from the intracerebral pial circulation, was used to assess GPVI shedding locally within the ischemic brain. Results: Our analysis revealed no significant increase in systemic sGPVI levels in patients with symptomatic ≥ 50% ICA stenosis (3.2 [95% CI 1.5-5.0] ng/mL; n = 33) compared with stroke patients without significant ICA stenosis (3.2 [95% CI 2.3-4.2] ng/mL; n = 72). Additionally, pial blood samples, reflecting intravascular molecular conditions during collateral flow, showed similar sGPVI levels when compared to the systemic ICA samples in both groups. Conclusions: Our findings indicate that GPVI is not locally cleaved and shed into the bloodstream in significant amounts during hyper-acute ischemic stroke, neither at the level of symptomatic ICA nor intracranially during collateral blood supply. Therefore, sGPVI does not appear to be suitable as a local stroke biomarker despite strong evidence of a major role for GPVI-signaling in stroke pathophysiology.

Mendelian Randomization and Bayesian Colocalization Analysis Implicate Glycoprotein VI as a Potential Drug Target for Cardioembolic Stroke in South Asian Populations

BACKGROUND

Circulating plasma proteins are clinically useful biomarkers for stroke risk. We examined the causal links between plasma proteins and stroke risk in individuals of South Asian ancestry.

METHODS AND RESULTS

We applied proteome-wide Mendelian randomization and colocalization approaches to understand causality of 2922 plasma proteins on stroke risk in individuals of South Asian ancestry. We obtained genetic instruments (proxies) for plasma proteins from the UK Biobank (N=920). Genome-wide association studies summary data for strokes (N≤11 312) were sourced from GIGASTROKE consortium. Our primary approach involved the Wald ratio or inverse-variance-weighted methods, with statistical significance set at false discovery rate <0.1. Additionally, a Bayesian colocalization approach assessed shared causal variants among proteome, transcriptome, and stroke phenotypes to minimize bias from linkage disequilibrium. We found evidence of a potential causal effect of plasma GP6 (glycoprotein VI) levels on cardioembolic stroke (odds ratio [OR]Wald ratio=2.53 [95% CI, 1.59-4.03]; P=9.2×10-5, false discovery rate=0.059). Generalized Mendelian randomization accounting for correlated single nucleotide polymorphisms (SNPs), with the P value threshold at P<5×10-8 and clumped at r2=0.3, showed consistent direction of effect of GP6 on cardioembolic stroke (ORgeneralized inverse-variance-weighted=2.21 [95% CI, 1.46-3.33]; P=1.6×10-4). Colocalization analysis indicated that plasma GP6 levels colocalize with cardioembolic stroke (posterior probability=91.4%). Multitrait colocalization combining transcriptome, proteome, and cardioembolic stroke showed moderate to strong evidence that these 2 traits colocalize with GP6 expression in the coronary artery and brain tissues (multitrait posterior probability>50%). The potential causal effect of GP6 on cardioembolic stroke was not significant in European populations (ORinverse-variance-weighted=1.08 [95% CI, 0.93-1.26]; P=0.29).

CONCLUSIONS

Our joint Mendelian randomization and colocalization analyses suggest that genetically predicted GP6 is potentially causally associated with cardioembolic stroke risk in individuals of South Asian ancestry. As genetic data on individuals of South Asian ancestry increase, future Mendelian randomization studies with larger sample size for plasma GP6 levels should be implemented to further validate our findings. Additionally, clinical studies will be necessary to verify GP6 as a therapeutic target for cardioembolic stroke in South Asians.

GPVI inhibition: Advancing antithrombotic therapy in cardiovascular disease

Glycoprotein (GP) VI (GPVI) plays a major role in thrombosis but not haemostasis, making it a promising antithrombotic target. The primary role of GPVI on the surface of platelets is a signalling receptor for collagen, which is one of the most potent thrombotic sub-endothelial components that is exposed by atherosclerotic plaque rupture. Inhibition of GPVI has therefore been investigated as a strategy for treatment and prevention of atherothrombosis, such as during stroke and acute coronary syndromes. A range of specific GPVI inhibitors have been characterized, and two of these inhibitors, glenzocimab and revacept, have completed Phase II clinical trials in ischaemic stroke. In this review, we summarize mechanisms of GPVI activation and the latest progress of clinically tested GPVI inhibitors, including their mechanisms of action. By focusing on what is known about GPVI activation, we also discuss whether alternate strategies could be used to target GPVI.

Modifying platelets at their birth: anti-thrombotic therapy without haemorrhage

Cardiovascular disease is a leading cause of death. The current approach to the prevention of arterial thrombosis in cardiovascular disease is dependent on the use of therapies which inhibit the activation of platelets. Predictably these are associated with an increased risk of haemorrhage which causes significant morbidity. The thrombotic potential of an activated platelet is modifiable; being determined before thrombopoiesis. Increased megakaryocyte ploidy is associated with larger and more active platelets carrying an increased risk of thrombosis. The reduction in the ploidy of megakaryocytes is therefore a novel area of therapeutic interest for reducing thrombosis. We propose a new therapeutic approach for the prevention and treatment of thrombosis by targeting the reduction in ploidy of megakaryocytes. We examine the role of a receptor mediated event causing megakaryocytes to increase ploidy, the potential for targeting the molecular mechanisms underpinning megakaryocyte endomitosis and the existence of two separate regulatory pathways to maintain haemostasis by altering the thrombotic potential of platelets as targets for novel therapeutic approaches producing haemostatically competent platelets which are not prothrombotic.

Acute ischemic STROKE - from laboratory to the Patient's BED (STROKELABED): A translational approach to reperfusion injury. Study Protocol

Cerebral edema (CE) and hemorrhagic transformation (HT) are frequent and unpredictable events in patients with acute ischemic stroke (AIS), even when an effective vessel recanalization has been achieved. These complications, related to blood-brain barrier (BBB) disruption, remain difficult to prevent or treat and may offset the beneficial effect of recanalization, and lead to poor outcomes. The aim of this translational study is to evaluate the association of circulating and imaging biomarkers with subsequent CE and HT in stroke patients with the dual purpose of investigating possible predictors as well as molecular dynamics underpinning those events and functional outcomes. Concurrently, the preclinical study will develop a new mouse model of middle cerebral artery (MCA) occlusion and recanalization to explore BBB alterations and their potentially harmful effects on tissue. The clinical section of the study is based on a single-center observational design enrolling consecutive patients with AIS in the anterior circulation territory, treated with recanalization therapies from October 1, 2015 to May 31, 2020. The study will employ an innovative evaluation of routine CT scans: in fact, we will assess and quantify the presence of CE and HT after stroke in CT scans at 24 h, through the quantification of anatomical distortion (AD), a measure of CE and HT. We will investigate the relationship of AD and several blood biomarkers of inflammation and extracellular matrix, with functional outcomes at 3 months. In parallel, we will employ a newly developed mouse model of stroke and recanalization, to investigate the emergence of BBB changes 24 h after the stroke onset. The close interaction between clinical and preclinical research can enhance our understanding of findings from each branch of research, enabling a deeper interpretation of the underlying mechanisms of reperfusion injury following recanalization treatment for AIS.