Anti Xa oral anticoagulants inhibit in vivo platelet activation by modulating glycoprotein VI shedding

Efficacy and Safety of Combination Therapy with Low-Dose Rivaroxaban in Patients with Cardiovascular Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objectives: To review the evidence on the effectiveness and safety of low-dose-rivaroxaban 2.5 mg twice daily (LDR) in patients with coronary artery disease (CAD) and/or peripheral artery disease (PAD) taking antiplatelets. Methods: We performed a systematic review and meta-analysis of randomized controlled trials (RCTs). Efficacy endpoints were cardiovascular events (CVEs), myocardial infarction, stroke, all-cause, and cardiovascular death. Any, major, fatal bleeding, and intracranial hemorrhage (ICH) were safety endpoints. Numbers needed to treat (NNT), and numbers needed to harm (NNH) were also calculated. Results: Seven RCTs were included with 45,836 patients: 34,276 with CAD and 11,560 with PAD. Overall, 4247 CVEs and 3082 bleedings were registered. LDR in association with either any antiplatelet drug or aspirin (ASA) alone reduced the risk of CVEs (hazard ratio [HR] 0.86, 95% confidence interval [95%CI] 0.78-0.94) and ischemic stroke (HR 0.68, 95%CI 0.55-0.84). LDR + ASA increased the risk of major bleeding (HR 1.71, 95%CI 1.38-2.11) but no excess of fatal bleeding or ICH was found. The NNT to prevent one CVE for LDR + ASA was 63 (43-103) and the NNH to cause major bleeding was 107 (77-193). Conclusions: The combination of LDR with either antiplatelet drugs or low-dose aspirin reduces CVEs and ischemic stroke in patients with CAD/PAD. There was an increased risk of major bleeding but no excess of fatal or ICH was found. LDR seems to have a favorable net clinical benefit compared to ASA treatment alone.

Ex Vivo Antiplatelet Effects of Oral Anticoagulants

BACKGROUND

The impact of non-vitamin K antagonist oral anticoagulants (NOACs) on platelet function is still unclear. We conducted a comprehensive ex vivo study aimed at assessing the effect of the four currently marketed NOACs on platelet function.

METHODS

We incubated blood samples from healthy donors with concentrations of NOACs (50, 150 and 250 ng/mL), in the range of those achieved in the plasma of patients during therapy. We evaluated generation of thrombin; light transmittance platelet aggregation (LTA) in response to adenosine diphosphate (ADP), thrombin receptor-activating peptide (TRAP), human γ-thrombin (THR) and tissue factor (TF); generation of thromboxane (TX)B2; and expression of protease-activated receptor (PAR)-1 and P-selectin on the platelet surface.

RESULTS

All NOACs concentration-dependently reduced thrombin generation compared with control. THR-induced LTA was suppressed by the addition of dabigatran at any concentration, while TF-induced LTA was reduced by factor-Xa inhibitors. ADP- and TRAP-induced LTA was not modified by NOACs. TXB2 generation was reduced by all NOACs, particularly at the highest concentrations. We found a concentration-dependent increase in PAR-1 expression after incubation with dabigatran, mainly at the highest concentrations, but not with FXa inhibitors; P-selectin expression was not changed by any drugs.

CONCLUSIONS

Treatment with the NOACs is associated with measurable ex vivo changes in platelet function, arguing for antiplatelet effects beyond the well-known anticoagulant activities of these drugs. There are differences, however, among the NOACs, especially between dabigatran and the FXa inhibitors.

Toward Genetic Testing of Rivaroxaban? Insights from a Systematic Review on the Role of Genetic Polymorphism in Rivaroxaban Therapy

BACKGROUND

Investigations into the rivaroxaban response from the perspective of genetic variation have been relatively recent and wide in scope, whereas there is no consensus on the necessity of genetic testing of rivaroxaban. Thus, this systematic review aims to thoroughly evaluate the relationship between genetic polymorphisms and rivaroxaban outcomes.

METHODS

The PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Chinese databases were searched to 23 October 2022. We included cohort studies reporting the pharmacogenetic correlation of rivaroxaban. Outcomes measured included efficacy (all-cause mortality, thromboembolic events and coagulation-related tests), safety (major bleeding, clinically relevant non-major bleeding [CRNMB] and any hemorrhage), and pharmacokinetic outcomes. A narrative synthesis was performed to summarize findings from individual studies according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the reporting guideline for Synthesis Without Meta-Analysis.

RESULTS

A total of 12 studies published between 2019 and 2022 involving 1364 patients were included. Ten, one, and six studies focused on the ABCB1, ABCG2, and CYP gene polymorphisms, respectively. Pharmacokinetic outcomes accounted for the majority of the outcomes reported (n = 11), followed by efficacy (n = 5) [including prothrombin time (PT) or international normalized ratio (n = 3), platelet inhibition rate (PIR) or platelet reactivity units (PRUs; n = 1), thromboembolic events (n = 1)], and safety (n = 5) [including major bleeding (n = 2), CRNMB (n = 2), any hemorrhage (n = 1)]. For ABCB1 gene polymorphism, the relationship between PT and ABCB1 rs1045642 was inconsistent across studies, however there was no pharmacogenetic relationship with other efficacy outcomes. Safety associations were found in ABCB1 rs4148738 and major bleeding, ABCB1 rs4148738 and CRNMB, ABCB1 rs1045642 and CRNMB, and ABCB1 rs2032582 and hemorrhage. Pharmacokinetic results were inconsistent among studies. For ABCG2 gene polymorphism, no correlation was observed between ABCG2 rs2231142 and dose-adjusted trough concentration (Cmin/D). For CYP gene polymorphisms, PIR or PRUs have a relationship with CYP2C19 rs12248560, however bleeding or pharmacokinetic effects did not show similar results.

CONCLUSIONS

Currently available data are insufficient to confirm the relationship between clinical or pharmacokinetic outcomes of rivaroxaban and gene polymorphisms. Proactive strategies are advised as a priority in clinical practice rather than detection of SNP genotyping.

CLINICAL TRIALS REGISTRATION

PROSPERO registration number CRD42022347907.

Is It Really Safe to Discontinue Antiplatelet Therapy 12 Months After Percutaneous Coronary Intervention in Patients with Atrial Fibrillation?

The prevalence of AF in patients with coronary artery disease is high. The guidelines from many professional groups, including the European Society of Cardiology, American College of Cardiology/American Heart Association and Heart Rhythm Society, recommend a maximum duration of 12 months of combination single antiplatelet and anticoagulation therapy in patients who undergo percutaneous coronary intervention and who have concurrent AF, followed by anticoagulation alone beyond 1 year. However, the evidence that anticoagulation alone without antiplatelet therapy adequately reduces the well-documented attritional risk of stent thrombosis after coronary stent implantation is relatively sparse, particularly given that very late stent thrombosis (>1 year from stent implantation) is the commonest type. By contrast, the elevated risk of bleeding from combined anticoagulation and antiplatelet therapy is clinically important. The aim of this review is to assess the evidence for long-term anticoagulation alone without antiplatelet therapy 1 year post-percutaneous coronary intervention in patients with AF.

The effect of rivaroxaban on biomarkers in blood and plasma: a review of preclinical and clinical evidence

Rivaroxaban is a direct, oral factor Xa inhibitor that is used for the prevention and treatment of various thromboembolic disorders. Several preclinical and clinical studies have utilized specific molecules as biomarkers to investigate the potential role of rivaroxaban beyond its anticoagulant activity and across a range of biological processes. The aim of this review is to summarize the existing evidence regarding the use of blood-based biomarkers to characterize the effects of rivaroxaban on coagulation and other pathways, including platelet activation, inflammation and endothelial effects. After a literature search using PubMed, almost 100 preclinical and clinical studies were identified that investigated the effects of rivaroxaban using molecular biomarkers. In agreement with the preclinical data, clinical studies reported a trend for reduction in the blood concentrations of D-dimers, thrombin-antithrombin complex and prothrombin fragment 1 + 2 following treatment with rivaroxaban in both healthy individuals and those with various chronic conditions. Preclinical and also some clinical studies have also reported a potential impact of rivaroxaban on the concentrations of platelet activation biomarkers (von Willebrand factor, P-selectin and thrombomodulin), endothelial activation biomarkers (matrix metalloproteinase-9, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) and inflammation biomarkers (interleukin-6, tumor necrosis factor-α and monocyte chemoattractant protein-1). Based on the results of biomarker studies, molecular biomarkers can be used in addition to traditional coagulation assays to increase the understanding of the anticoagulation effects of rivaroxaban. Moreover, there is preliminary evidence to suggest that rivaroxaban may have an impact on the biological pathways of platelet activation, endothelial activation and inflammation; however, owing to paucity of clinical data to investigate the trends reported in preclinical studies, further investigation is required to clarify these observations.

Soluble Platelet Release Factors as Biomarkers for Cardiovascular Disease

Platelets are the main players in thrombotic diseases, where activated platelets not only mediate thrombus formation but also are involved in multiple interactions with vascular cells, inflammatory components, and the coagulation system. Although in vitro reactivity of platelets provides information on the function of circulating platelets, it is not a full reflection of the in vivo activation state, which may be relevant for thrombotic risk assessment in various disease conditions. Therefore, studying release markers of activated platelets in plasma is of interest. While this type of study has been done for decades, there are several new discoveries that highlight the need for a critical assessment of the available tests and indications for platelet release products. First, new insights have shown that platelets are not only prominent players in arterial vascular disease, but also in venous thromboembolism and atrial fibrillation. Second, knowledge of the platelet proteome has dramatically expanded over the past years, which contributed to an increasing array of tests for proteins released and shed from platelets upon activation. Identification of changes in the level of plasma biomarkers associated with upcoming thromboembolic events allows timely and individualized adjustment of the treatment strategy to prevent disease aggravation. Therefore, biomarkers of platelet activation may become a valuable instrument for acute event prognosis. In this narrative review based on a systematic search of the literature, we summarize the process of platelet activation and release products, discuss the clinical context in which platelet release products have been measured as well as the potential clinical relevance.

Rivaroxaban reduces thromboxane induced platelet aggregation - the forgotten Compass Arm?

Background: Recent guidelines only recommend 'vascular dose' rivaroxaban in combination with aspirin in chronic coronary syndrome (CCS) patients with high risk of ischemic events However, in the COMPASS trial, a reduction of MACCE appeared for low-dose rivaroxaban alone compared to aspirin as well. It was recently shown that FXa induces platelet aggregation via protease activated receptor 1 (PAR-1) which is in turn attenuated by rivaroxaban. However, a potential impact of rivaroxaban on TX B2 formation is unclear.Methods and Results: TX B2 levels were measured in supernatant from washed platelets after FXa (52 µg/ml) induced platelet aggregation. TX B2 levels were significantly higher in supernatant from FXa-stimulated platelets compared to unstimulated control (Control 23.53 ± 14.15 ng/ml vs. FXa stimulated 77.4 ± 64.14 ng/ml; p = .0025). This effect was abolished in the presence of 100pM rivaroxaban (Control 23.53 ± 14.15 ng/ml vs. FXa stimulated and rivaroxaban 22.15 ± 24.74 ng/ml; p = .5142). Next, we investigated the effects of 100pM rivaroxaban on platelet aggregation induced by U46619 (TX receptor agonist) using light transmission aggregometry. Platelet aggregation quantified by maximum of aggregation (MoA%) was significantly lower in presence of rivaroxaban (U46619 40.18 ± 20.51% vs. U46619+ rivaroxaban 19.26 ± 15.46%; p = .0274).Conclusion: Our results indicate direct effects of rivaroxaban on the cyclooxygenase-1- TX axis during platelet aggregation. Hence, it seems reasonable that the 'forgotten compass arm' (rivaroxaban alone) might be an alternative to the rivaroxaban plus aspirin combination in CCS patients.

Long-Term Risk of Major Adverse Cardiac Events in Atrial Fibrillation Patients on Direct Oral Anticoagulants

OBJECTIVE

To determine the association between direct oral anticoagulant (DOAC) use and risk of major adverse cardiac events (MACEs) in patients with atrial fibrillation (AF).

PATIENTS AND METHODS

This study is a single-center prospective observational cohort study including 2366 outpatients with non-valvular AF on treatment with DOACs or vitamin K antagonists (VKAs) from February 2008 for patients on VKA and September 2013 for patients on novel oral anticoagulants. The primary endpoint was the incidence of MACE including fatal and non-fatal myocardial infarction (MI), cardiac revascularization, and cardiovascular death.

RESULTS

The mean age was 75.1±9.0 years; 44.7% were women. During a mean follow-up of 33.3±21.9 months (6567 patients/years) 133 MACEs occurred (2.03%/year): 79 MI/cardiac revascularization and 54 cardiovascular deaths. Of these, 101 were on VKAs (2.42%/year) and 32 on DOACs (1.34%/year; log-rank test P=.040). This difference was evident also considering MI alone (1.53%/year and 0.63%/year in the VKA and DOAC group, respectively, log-rank test P=.009). At multivariable Cox proportional hazard regression analysis, use of DOACs was associated with a lower risk of MACE (hazard ratio, 0.636; 95% CI, 0.417 to 0.970; P=.036) and MI (hazard ratio, 0.497; 95% CI, 0.276 to 0.896; p=.020). Sensitivity analysis showed that this association was consistent in younger patients (<75 years), in patients with anemia, and in those without chronic obstructive pulmonary disease and heart failure. We also found that both dabigatran and apixaban/rivaroxaban were associated with a lower rate of MACE, with similar efficacy between full and low doses.

CONCLUSION

DOACs are associated with a lower risk of MACE in patients with AF independently from dosage.

Different DOACs Control Inflammation in Cardiac Ischemia-Reperfusion Differently

RATIONALE

While thrombin is the key protease in thrombus formation, other coagulation proteases, such as fXa (factor Xa) or aPC (activated protein C), independently modulate intracellular signaling via partially distinct receptors.

OBJECTIVES

To study the differential effects of fXa or fIIa (factor IIa) inhibition on gene expression and inflammation in myocardial ischemia-reperfusion injury.

METHODS AND RESULTS

Mice were treated with a direct fIIa inhibitor (fIIai) or direct fXa inhibitor (fXai) at doses that induced comparable anticoagulant effects ex vivo and in vivo (tail-bleeding assay and FeCl₃-induced thrombosis). Myocardial ischemia-reperfusion injury was induced via left anterior descending ligation. We determined infarct size and in vivo aPC generation, analyzed gene expression by RNA sequencing, and performed immunoblotting and ELISA. The signaling-only 3K3A-aPC variant and inhibitory antibodies that blocked all or only the anticoagulant function of aPC were used to determine the role of aPC. Doses of fIIai and fXai that induced comparable anticoagulant effects resulted in a comparable reduction in infarct size. However, unbiased gene expression analyses revealed marked differences, including pathways related to sterile inflammation and inflammasome regulation. fXai but not fIIai inhibited sterile inflammation by reducing the expression of proinflammatory cytokines (IL [interleukin]-1β, IL-6, and TNFα [tumor necrosis factor alpha]), as well as NF-κB (nuclear factor kappa B) and inflammasome activation. This anti-inflammatory effect was associated with reduced myocardial fibrosis 28 days post-myocardial ischemia-reperfusion injury. Mechanistically, in vivo aPC generation was higher with fXai than with fIIai. Inhibition of the anticoagulant and signaling properties of aPC abolished the anti-inflammatory effect associated with fXai, while inhibiting only the anticoagulant function of aPC had no effect. Combining 3K3A-aPC with fIIai reduced the inflammatory response, mimicking the fXai-associated effect.

CONCLUSIONS

We showed that specific inhibition of coagulation via direct oral anticoagulants had differential effects on gene expression and inflammation, despite comparable anticoagulant effects and infarct sizes. Targeting individual coagulation proteases induces specific cellular responses unrelated to their anticoagulant effect.

Noncanonical Effects of Oral Thrombin and Factor Xa Inhibitors in Platelet Activation and Arterial Thrombosis

Nonvitamin K oral anticoagulants (NOACs) or direct oral anticoagulants comprise inhibitors of factor Xa (rivaroxaban, apixaban, edoxaban) or factor IIa (dabigatran). Both classes efficiently interfere with the final or penultimate step of the coagulation cascade and showed superior net clinical benefit compared with vitamin K antagonists for prevention of thromboembolic events in patients with AF and for prevention and therapy of deep vein thrombosis and pulmonary embolism. None the less, accumulating data suggested, that there may be differences regarding the frequency of atherothrombotic cardiovascular events between NOACs. Thus, the optimal individualized NOAC for each patient remains a matter of debate. Against this background, some basic and translational analyses emphasized NOAC effects that impact on platelet activity and arterial thrombus formation beyond inhibition of plasmatic coagulation. In this review, we will provide an overview of the available clinical and translational evidence for so-called noncanonical NOAC effects on platelet activation and arterial thrombosis.

MT in anticoagulated patients

Mechanical thrombectomy (MT) is one of the main treatments for acute ischemic stroke (AIS) in patients on effective anticoagulation. The use of direct oral anticoagulants (DOA) has increased, given their efficacy and safety profile compared to vitamin K antagonists (VKA). We compared procedural and clinical outcomes of MT in patients on DOA and VKA treatment before stroke onset. We analyzed 2 groups from the Endovascular Treatment in Ischemic Stroke prospective registry: patients on DOA and patients on VKA treated by MT without thrombolysis. Generalized linear mixed models including center as random effect were used to compare angiographic (rates of reperfusion at end of procedure, number of passes >2, procedural complications) and clinical (favorable and excellent outcome, 90-day all-cause mortality, and hemorrhagic complications) outcomes according to anticoagulation subgroups. Comparisons were adjusted for prespecified confounders (age, admission NIH Stroke Scale score) as well as for meaningful baseline between-group differences. Among 221 patients included, more DOA-treated patients (n = 115, 52%) achieved successful (modified Thrombolysis in Cerebral Infarction score [mTICI] 2b/3) or near complete (mTICI 2c/3) reperfusion at the procedure end than did VKA-treated patients, with an adjusted odds ratio (OR) for DOA vs VKA of 3.27 (95% confidence interval [CI], 1.40–7.65) and 2.00 (95% CI, 1.08–3.73), respectively. DOA-treated patients had a lower 90-day mortality risk with an adjusted OR of 0.47 (95% CI, 0.24–0.89) and a better excellent outcome OR of 2.40 (1.10–5.27). There was no significant between-group difference in hemorrhagic or procedural complications. The study highlights the benefits of DOA compared to VKA. Regarding mortality, excellent outcomes, and recanalization rate, DOA appears to provide a favorable setting for MT treatment in AIS.

Rivaroxaban Reduces Arterial Thrombosis by Inhibition of FXa-Driven Platelet Activation via Protease Activated Receptor-1

RATIONALE

A reduced rate of myocardial infarction has been reported in patients with atrial fibrillation treated with FXa (factor Xa) inhibitors including rivaroxaban compared with vitamin K antagonists. At the same time, low-dose rivaroxaban has been shown to reduce mortality and atherothrombotic events in patients with coronary artery disease. Yet, the mechanisms underlying this reduction remain unknown.

OBJECTIVE

In this study, we hypothesized that rivaroxaban's antithrombotic potential is linked to a hitherto unknown rivaroxaban effect that impacts on platelet reactivity and arterial thrombosis.

METHODS AND RESULTS

In this study, we identified FXa as potent, direct agonist of the PAR-1 (protease-activated receptor 1), leading to platelet activation and thrombus formation, which can be inhibited by rivaroxaban. We found that rivaroxaban reduced arterial thrombus stability in a mouse model of arterial thrombosis using intravital microscopy. For in vitro studies, atrial fibrillation patients on permanent rivaroxaban treatment for stroke prevention, respective controls, and patients with new-onset atrial fibrillation before and after first intake of rivaroxaban (time series analysis) were recruited. Platelet aggregation responses, as well as thrombus formation under arterial flow conditions on collagen and atherosclerotic plaque material, were attenuated by rivaroxaban. We show that rivaroxaban's antiplatelet effect is plasma dependent but independent of thrombin and rivaroxaban's anticoagulatory capacity.

CONCLUSIONS

Here, we identified FXa as potent platelet agonist that acts through PAR-1. Therefore, rivaroxaban exerts an antiplatelet effect that together with its well-known potent anticoagulatory capacity might lead to reduced frequency of atherothrombotic events and improved outcome in patients.

Non-vitamin K oral anticoagulants (NOAC) and the risk of myocardial infarction: Differences between factor IIa and factor Xa inhibition?

Guidelines already recommend non-vitamin K oral anticoagulants (NOAC) over vitamin-K antagonists (VKA) for stroke prevention in patients with atrial fibrillation. However, recommendations are lacking with respect to which NOAC to use. At the moment, NOACs may employ two different molecular mechanisms: Factor IIa inhibition (dabigatran) and factor Xa inhibition (apixaban, edoxaban, rivaroxaban). The focus of this review is to compare and contrast potential differences between factor IIa- and factor Xa inhibition with respect to risk of myocardial infarction and to detail underlying mechanisms.

Major adverse cardiovascular events in non-valvular atrial fibrillation with chronic obstructive pulmonary disease: the ARAPACIS study

Chronic obstructive pulmonary disease (COPD) increases the risk of mortality in non-valvular atrial fibrillation (NVAF) patients. Data on the relationship of COPD to major cardiovascular events (MACE) in AF have not been defined. The aim of the study is to assess the predictive value of COPD on incident MACE in NVAF patients over a 3-year follow-up. In the Atrial Fibrillation Registry for Ankle-Brachial Index Prevalence Assessment-Collaborative Italian Study (ARAPACIS) cohort, we evaluate the impact of COPD on the following clinical endpoints: MACE (including vascular death, fatal/non-fatal MI and stroke/TIA), cardiovascular (CV) death and all-cause mortality. Among 2027 NVAF patients, patients with COPD (9%) are more commonly male, elderly and at higher thromboembolic risk. During a median 36.0 months follow-up, 186 patients experienced MACE: vascular death (n = 72), MI (n = 57), stroke/TIA (n = 57). All major outcomes (including stroke/TIA, MI, vascular death, and all-cause death) are centrally adjudicated. Kaplan-Meier curves show that NVAF patients with COPD are at higher risk for MACE (p < 0.001), CV death (p < 0.001) and all-cause death (p < 0.001). On Cox proportional hazard analysis, COPD is an independent predictor of MACE (Hazard ratio [HR] 1.77, 95% Confidence Intervals [CI] 1.20-2.61; p = 0.004), CV death (HR 2.73, 95% CI 1.76-4.23; p < 0.0001) and all-cause death (HR 2.16, 95% CI 1.48-3.16; p < 0.0001). COPD is an independent predictor of MACE, CV death and all-cause death during a long-term follow-up of NVAF patients.

Atherothrombosis and Oxidative Stress: Mechanisms and Management in Elderly

SIGNIFICANCE

The incidence of cardiovascular events (CVEs) increases with age, representing the main cause of death in an elderly population. Aging is associated with overproduction of reactive oxygen species (ROS), which may affect clotting and platelet activation, and impair endothelial function, thus predisposing elderly patients to thrombotic complications. Recent Advances: There is increasing evidence to suggest that aging is associated with an imbalance between oxidative stress and antioxidant status. Thus, upregulation of ROS-producing enzymes such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and myeloperoxidase, along with downregulation of antioxidant enzymes, such as superoxide dismutase and glutathione peroxidase, occurs during aging. This imbalance may predispose to thrombosis by enhancing platelet and clotting activation and eliciting endothelial dysfunction. Recently, gut-derived products, such as trimethylamine N-oxide (TMAO) and lipopolysaccharide, are emerging as novel atherosclerotic risk factors, and gut microbiota composition has been shown to change by aging, and may concur with the increased cardiovascular risk in the elderly.

CRITICAL ISSUES

Antioxidant treatment is ineffective in patients at risk or with cardiovascular disease. Further, anti-thrombotic treatment seems to work less in the elderly population.

FUTURE DIRECTIONS

Interventional trials with antioxidants targeting enzymes implicated in aging-related atherothrombosis are warranted to explore whether modulation of redox status is effective in lowering CVEs in the elderly. Antioxid. Redox Signal. 27, 1083-1124.