Platelet ACKR3/CXCR7 Favors Anti-Platelet Lipids over an Atherothrombotic Lipidome and Regulates Thrombo-inflammation

Platelet ACKR3/CXCR7 surface expression is enhanced and influences prognosis in coronary artery disease-(CAD) patients, who exhibit a distinct atherothrombotic platelet lipidome. Current investigation validates the potential of ACKR3/CXCR7 in regulating thrombo-inflammatory response, through its impact on the platelet lipidome. CAD patients-(n=230) with enhanced platelet-ACKR3/CXCR7 expression exhibited reduced aggregation. Pharmacological CXCR7-agonist-(VUF11207) significantly reduced pro-thrombotic platelet response in blood from ACS patients-(n=11) ex vivo. CXCR7-agonist administration reduced thrombotic functions and thrombo-inflammatory platelet-leukocyte interactions post myocardial infarction-(MI) and arterial injury in vivo. ACKR3/CXCR7-ligation did not affect surface availability of GPIbα, GPV, GPVI, GPIX, αv-integrin, β3-integrin, coagulation profile-(APTT, PT), bleeding time, plasma-dependent thrombin generation-(thrombinoscopy) or clot formation-(thromboelastography), but counteracted activation-induced phosphatidylserine exposure and procoagulant platelet-assisted thrombin generation. Targeted-(micro-UHPLC-ESI-QTrap-MS/MS) and untargeted-(UHPLC-ESI-QTOF-MS/MS) lipidomics analysis revealed that ACKR3/CXCR7-ligation favored generation of anti-thrombotic lipids-(dihomo-γ-linolenic acid-DGLA, 12-hydroxyeicosatrienoic acid-12-HETrE) over cyclooxygenase-COX-1-(thromboxane-TxA2), or 12-lipoxygenase-LOX-(12-HETE) metabolized pro-thrombotic, and phospholipase derived atherogenic-(lysophosphatidylcholine-LPC) lipids, in healthy subjects and CAD patients, contrary to anti-platelet therapy. Through 12-HETrE, ACKR3/CXCR7-ligation coordinated with Gαs-coupled prostacyclin receptor-(IP) to trigger cAMP-PKA mediated platelet inhibition. ACKR3/CXCR7-ligation reduced generation of lipid agonists-(arachidonic acid-AA,TxA2), lipid signaling intermediates-(lyophosphatidylinositol-LPI, diacylglycerol-DG), which affected calcium mobilization, intracellular signaling, consequently platelet interaction with physiological matrices and thrombo-inflammatory secretion-(IL1β,IFN-γ,TGF-β,IL-8), emphasizing its functional dichotomy from pro-thrombotic CXCR4. Moreover, CXCR7-agonist regulated heparin-induced thrombocytopenia-(HIT)-sera/IgG-induced platelet and neutrophil activation, heparin induced platelet aggregation-(HIPA), generation of COX-1-(TxA2), 12-LOX-(12-HETE) derived thrombo-inflammatory lipids, platelet-neutrophil aggregate formation, and thrombo-inflammatory secretion (sCD40L, IL-1β, IFN-γ, TNF-α, sP-selectin, IL-8, tissue factor-TF) ex vivo. Therefore, ACKR3/CXCR7 may offer a novel therapeutic strategy in acute/chronic thrombo-inflammation exaggerated cardiovascular pathologies, and CAD.

P2Y12 Inhibition in Murine Myocarditis Results in Reduced Platelet Infiltration and Preserved Ejection Fraction

Previous mouse studies have shown the increased presence of platelets in the myocardium during early stages of myocarditis and their selective detection by MRI. Here, we aimed to depict early myocarditis using molecular contrast-enhanced ultrasound of activated platelets, and to evaluate the impact of a P2Y12 receptor platelet inhibition. Experimental autoimmune myocarditis was induced in BALB/c mice by subcutaneous injection of porcine cardiac myosin and complete Freund adjuvant (CFA). Activated platelets were targeted with microbubbles (MB) coupled to a single-chain antibody that binds to the “ligand-induced binding sites” of the GPIIb/IIIa-receptor (=LIBS-MB). Alongside myocarditis induction, a group of mice received a daily dose of 100 g prasugrel for 1 month. Mice injected with myosin and CFA had a significantly deteriorated ejection fraction and histological inflammation on day 28 compared to mice only injected with myosin. Platelets infiltrated the myocardium before reduction in ejection fraction could be detected by echocardiography. No selective binding of the LIBS-MB contrast agent could be detected by either ultrasound or histology. Prasugrel therapy preserved ejection fraction and significantly reduced platelet aggregates in the myocardium compared to mice without prasugrel therapy. Therefore, P2Y12 inhibition could be a promising early therapeutic target in myocarditis, requiring further investigation.

727 Circadian variations of platelet reactivity on Clopidogrel in patients treated with elective percutaneous coronary intervention

Aims The potential diurnal variations of platelet reactivity in patients on clopidogrel treated with elective percutaneous coronary intervention (PCI) for stable coronary artery disease (CAD) are currently unknown. Methods and results We prospectively enrolled 15 patients with stable CAD treated PCI and on clopidogrel therapy for at least eight days. All patients received their maintenance 75-mg clopidogrel dose at 8 AM. Platelet reactivity was assessed with the Verifynow P2Y12 assay at three different time points (10 AM, 6 PM, and 6 AM). Platelet reactivity is expressed as P2Y12 reaction units (PRU) and PRU thresholds ≥208 and ≥240 were used to define high platelet reactivity (HPR). A significant heterogeneity in diurnal levels of platelet reactivity was found (P = 0.0004), with a peak occurring at the 6 AM assessment. In addition, at the 6 AM evaluation patients showed the highest prevalence of HPR (53.3% of patients with PRU ≥240, 66.7% of patients with PRU ≥208). Conclusions Platelet reactivity in patients with stable CAD treated with PCI and taking clopidogrel in the morning follows a circadian rhythm, thus suggesting that platelet inhibition may not be constant and sufficient throughout the day. Whether an evening or a bis in die administration of clopidogrel may result in a constant and more reliable antiplatelet inhibition, should be investigated in dedicated studies.

Ticagrelor in Acute Coronary Syndromes

<p>The PLATO trial demonstrated significantly lower mortality and myocardial infarction in acute coronary syndrome (ACS) patients treated with ticagrelor and aspirin compared to clopidogrel and aspirin. Ticagrelor is a direct acting P2Y12 receptor antagonist, and is a more potent inhibitor of platelet reactivity than clopidogrel, and this is believed to be the main cause of its superior efficacy in the PLATO trial. A range of factors have been associated with high on-treatment platelet reactivity (HOTPR) on clopidogrel, including genetic factors, drug interactions and clinical risk factors. HOTPR on clopidogrel has been associated with a higher risk of adverse outcomes following ACS. On the basis of the PLATO trial results, and the theoretical limitations associated with clopidogrel, ticagrelor was funded by PHARMAC in July 2013, and has been recommended for use in patients with ACS in New Zealand. This thesis examined the use of ticagrelor in a real world ACS population being managed through Wellington Hospital cardiology department. We examined platelet reactivity in patients treated with ticagrelor compared to clopidogrel, factors associated with clinician choice to use ticagrelor versus clopidogrel and the incidence of side effects of ticagrelor that may have implications for compliance with the drug outside the setting of a randomized controlled trial. We found that ticagrelor significantly reduced both platelet reactivity (30.3 AU ± 17.5 versus 43.7 AU ± 24.8, p= 0.0001) and the proportion of patients classified as having HOTPR (15.9% versus 37.7%, p= 0.0001), in comparison to clopidogrel. The clinical variables associated with HOTPR differ between clopidogrel and ticagrelor, suggesting that different factors were driving residual platelet reactivity on the two agents. Over a 2 year period, clopidogrel (68%) was used more commonly than ticagrelor (42%), and in a different cohort of patients. Patients treated with ticagrelor were younger (61 years ± 10 versus 65 years ± 12, p=0.0001), less likely to present with STEMI (12% versus 31%, p=0.0001), less likely to have a history of prior myocardial infarction (15.8% versus 22.7%, p=0.05), and had lower GRACE (98 ± 24 versus 108 ± 28, p=0.0001) and CRUSADE (25 ± 9 versus 28 ± 12, p=0.001) risk scores compared to those treated with clopidogrel. Prescription of ticagrelor was therefore not driven by clinical risk. Antiplatelet prescription varied significantly according to the patients’ admitting hospital. Bleeding rates on ticagrelor and clopidogrel within 30 days of study enrolment were low and were not significantly different. There was 1 patient on clopidogrel who had the drug discontinued due to bleeding. At 30 day follow up, significantly more patients treated with ticagrelor reported dyspnoea (43.3% versus 27.1%, p=0.001), however discontinuation of the drug due to dyspnoea on ticagrelor was infrequent (1.7%). In this real world cohort of ACS patients, we observed that ticagrelor was associated with more potent platelet inhibition than clopidogrel, but was not associated with factors leading to increased discontinuation at 30 days. Despite the proven benefits of ticagrelor compared to clopidogrel, the majority of patients, including the highest risk patients appear to be preferentially treated with clopidogrel. The causes contributing to underuse of ticagrelor need to be examined and addressed.</p>

Ticagrelor in Acute Coronary Syndromes

<p>The PLATO trial demonstrated significantly lower mortality and myocardial infarction in acute coronary syndrome (ACS) patients treated with ticagrelor and aspirin compared to clopidogrel and aspirin. Ticagrelor is a direct acting P2Y12 receptor antagonist, and is a more potent inhibitor of platelet reactivity than clopidogrel, and this is believed to be the main cause of its superior efficacy in the PLATO trial. A range of factors have been associated with high on-treatment platelet reactivity (HOTPR) on clopidogrel, including genetic factors, drug interactions and clinical risk factors. HOTPR on clopidogrel has been associated with a higher risk of adverse outcomes following ACS. On the basis of the PLATO trial results, and the theoretical limitations associated with clopidogrel, ticagrelor was funded by PHARMAC in July 2013, and has been recommended for use in patients with ACS in New Zealand. This thesis examined the use of ticagrelor in a real world ACS population being managed through Wellington Hospital cardiology department. We examined platelet reactivity in patients treated with ticagrelor compared to clopidogrel, factors associated with clinician choice to use ticagrelor versus clopidogrel and the incidence of side effects of ticagrelor that may have implications for compliance with the drug outside the setting of a randomized controlled trial. We found that ticagrelor significantly reduced both platelet reactivity (30.3 AU ± 17.5 versus 43.7 AU ± 24.8, p= 0.0001) and the proportion of patients classified as having HOTPR (15.9% versus 37.7%, p= 0.0001), in comparison to clopidogrel. The clinical variables associated with HOTPR differ between clopidogrel and ticagrelor, suggesting that different factors were driving residual platelet reactivity on the two agents. Over a 2 year period, clopidogrel (68%) was used more commonly than ticagrelor (42%), and in a different cohort of patients. Patients treated with ticagrelor were younger (61 years ± 10 versus 65 years ± 12, p=0.0001), less likely to present with STEMI (12% versus 31%, p=0.0001), less likely to have a history of prior myocardial infarction (15.8% versus 22.7%, p=0.05), and had lower GRACE (98 ± 24 versus 108 ± 28, p=0.0001) and CRUSADE (25 ± 9 versus 28 ± 12, p=0.001) risk scores compared to those treated with clopidogrel. Prescription of ticagrelor was therefore not driven by clinical risk. Antiplatelet prescription varied significantly according to the patients’ admitting hospital. Bleeding rates on ticagrelor and clopidogrel within 30 days of study enrolment were low and were not significantly different. There was 1 patient on clopidogrel who had the drug discontinued due to bleeding. At 30 day follow up, significantly more patients treated with ticagrelor reported dyspnoea (43.3% versus 27.1%, p=0.001), however discontinuation of the drug due to dyspnoea on ticagrelor was infrequent (1.7%). In this real world cohort of ACS patients, we observed that ticagrelor was associated with more potent platelet inhibition than clopidogrel, but was not associated with factors leading to increased discontinuation at 30 days. Despite the proven benefits of ticagrelor compared to clopidogrel, the majority of patients, including the highest risk patients appear to be preferentially treated with clopidogrel. The causes contributing to underuse of ticagrelor need to be examined and addressed.</p>

Abstract 1122‐000231: A Review of Effect of Ticagrelor on Platelet Inhibition in Clopidogrel Non‐Responders Undergoing Neuroendovascular Procedure

Introduction : Neuroendovascular procedures are becoming more routine in the treatment of intracranial conditions such as aneurysms, arterial stenosis, and ischemic stroke. These patients are frequently treated with antiplatelet agents prior to the procedure to prevent thrombotic complications. The combination of aspirin and a P2Y12 inhibitor such as clopidogrel is often initiated days before elective procedures or as loading doses for emergent procedures. However, some patients may still experience post procedural thrombotic or hemorrhagic complications which may be related to platelet inhibition. Methods : A retrospective review of patients who underwent a neuroendovascular procedure from 1/2017 to 12/2019 in a single tertiary care academic hospital. Procedures included flow‐diverting stent placement for aneurysms, intracranial, and cervical carotid artery stenting. Patients undergoing elective procedure were started on Aspirin and Clopidogrel 75 mg daily. Patients undergoing emergent procedures were given loading doses of Aspirin (650 mg) and Clopidogrel (600 mg). P2Y12 assay was checked prior to receiving Platelet inhibitor and from 3–6 hours after Clopidogrel loading dose. Optimal platelet inhibition was classified as reduction in P2Y12 assay by at least 60%. Patients with suboptimal platelet inhibition <60% were given Ticagrelor loading dose (180 mg) and P2y12 assay was rechecked. Patients who did not have complete chart information, patients with AFib requiring DOAC and patients previously on ADP inhibitors, were excluded from analysis. Results : Total neuroendovascular procedures requiring stents were 687 over the period of 3 years. mean age of patients was 61 years. This neuroendovascular procedure consisted of aneurysm stenting (239), aneurysm stent‐assisted coiling 112, intracranial stent for failed mechanical thrombectomy 62, carotid artery stent 108. Suboptimal platelet inhibition was noted in 54% (282) of 523 patients after receiving Clopidogrel. After receiving Ticagrelor, optimal inhibition was noted in 80% (226) of 282 patients with median increase of 26%. 62 patients with suboptimal response to Ticagrelor, 47 were started on Prasugrel. Thrombotic complications were noted in 7 patients, 6 of them were noted to have <50% platelet inhibition. Hemorrhagic complications were noted in 17 patients, amongst them >70% platelet inhibition was noted in 14 patients with mean P2Y12 value of 59. Conclusions : Patients receiving P2Y12 ADP antiplatelet therapy may have suboptimal platelet inhibition which results in increased thrombotic risk. Patients who have significant platelet inhibition (>70%) after loading dose are at increased risk for hemorrhagic complications. Better platelet inhibition was achieved with Ticagrelor in Clopidogrel hypo‐response patients. In patients with Clopidogrel hyper‐response, dosing was changed to half the dose or alternate day to reduce hemorrhagic complications. As the use of endovascular therapies requiring dual anti‐platelet agents becomes more established, there is an increasing need to develop titration protocols that minimize the risk of thrombotic and hemorrhagic events based on platelet inhibition.

Abstract 1122‐000043: Vorapaxar as An Alternative for Ticagrelor Resistance in Neuroendovascular Intervention

Introduction : Perioperative dual‐antiplatelet therapy (DAPT) for flow diversion (FD) limits thromboembolic complications. Practice of DAPT varies across the neuroendovascular field but typically includes aspirin and an ADP receptor antagonist such as clopidogrel, prasugrel, or ticagrelor. Unfortunately, resistance to DAPT medications remains a concern for neuroendovascular intervention, and there is a current lack of standard alternatives for such resistance. The main goal of this abstract is to discuss ticagrelor resistance and to inform possible therapeutic options. Methods : We report a case of vorapaxar treated FD for an intracranial aneurysm in a patient with ticagrelor resistance. FD was deployed for a left internal carotid artery (ICA) blister aneurysm and bilateral ICA dissecting pseudoaneurysms (Figure 1). We also provide a narrative review on previous reports of ticagrelor resistance and associated treatment responses. We used the keywords: “ticagrelor,” “resistance,” “hypo‐response,” “stent thrombosis,” and “aneurysm.” These were implemented in various combinations with Boolean operators in three databases: PubMed, Ovid MEDLINE, and Ovid EMBASE. Results : During a complicated clinical course, the patient had three thromboembolic complications while on DAPT with ticagrelor or prasugrel leading to transition of antiplatelet therapy to vorapaxar. Thromboelastography with platelet mapping (TEG‐PM) routinely demonstrated inadequate platelet inhibition, which was confirmed with platelet function analyzer‐100. Initial TEG‐PM results were 0.0% ADP receptor inhibition and MA‐ADP of 62.2 mm. Repeat angiograms also indicated thromboembolic formation after each of the three events (Figure 1). After introduction of vorapaxar, the patient had adequate platelet inhibition with TEG‐PM results of 49.1% ADP receptor inhibition and MA‐ADP of 48.3 mm. At 84 days follow‐up, the patient was fully recovered with complete occlusion of the aneurysms. In a narrative review of the literature, there were ten previously reported cases of ticagrelor resistance or hypo‐response: three cases in the neuroendovascular literature and seven cases in the cardiovascular literature. Among all of the cases, there was a variability in protocol for treating patients with suggested ticagrelor resistance. All three neuroendovascular cases either employed another ADP receptor antagonist in hopes that the resistance would not generalize or eliminated DAPT altogether and settled for aspirin alone. In some of the cardiovascular cases, ticagrelor was even continued after patients exhibited laboratory evidence of resistance or hypo‐response. Conclusions : Given the paucity of cases describing ticagrelor resistance or hypo‐response in the neuroendovascular and cardiovascular literature, management of DAPT should remain a multifactorial decision depending on the clinical situation. Moreover, we need to consider therapeutic alternatives for cases of resistance such as thrombin receptor antagonists, specifically PAR1 receptor antagonists like vorapaxar. High quality randomized controlled trials are needed to elucidate the safety and efficacy of vorapaxar in neuroendovascular procedures.

Triglyceride glucose index influences platelet reactivity in acute ischemic stroke patients

Aim Insulin resistance was reported to increase the risk of ischemic stroke, which can be assessed by the triglyceride glucose (TyG) index. However, it remains unclear whether the TyG index influences the platelet reactivity during the treatment of ischemic patients. Methods Ischemic stroke patients receiving dual antiplatelet therapy (DAPT) within 48 h onset were consecutively included. The TyG index was calculated as ln (fasting triglyceride [mg/dL] × fasting glucose [mg/dL]/2). The top quartile of TyG index was defined as insulin resistance. The platelet reactivity was assessed by thromboelastography. The platelet inhibition rate induced by arachidonic acid (AA) or adenosine diphosphate (ADP) was used to confirm the high residual on-treatment platelet reactivity (HRPR) to aspirin or clopidogrel, respectively. The association between TyG index and platelet reactivity was assessed by Kruskal–Wallis test. The independent risk factors of HRPR were determined by multivariate logistic regression analysis. Results A total of 1002 patients were included and divided into 4 groups by quartiles of the TyG index (< 2.02; 2.02–2.27; 2.27–2.52; ≥2.52). The findings demonstrated that the maximum intensity of the clot increased, but the AA-induced platelet inhibition rate decreased, depending on the TyG index quartiles. No significant difference was found in the ADP-induced platelet inhibition rate among groups. The prevalence of aspirin HRPR increased depending on the TyG index quartile. Unlike the non-insulin resistance group, the insulin resistance group was independently associated with aspirin HRPR (OR = 1.689, 95% CI 1.14 to 2.51, P = 0.009). Conclusions In acute ischemic stroke patients taking DAPT, the elevation of the TyG index is associated with enhanced platelet reactivity and higher prevalence of aspirin HRPR. Insulin resistance assessed by the TyG index could be an independent risk factor for aspirin HRPR.