FXa Inhibitors Research Articles

Rivaroxaban as a protector of Oxidative Stress-induced Vascular Endothelial Glycocalyx Damage via The IQGAP1/PAR1-2/PI3K/Akt Pathway.

The vascular endothelial glycocalyx, crucial for blood vessel integrity and homeostasis, is vulnerable to oxidative stress, leading to endothelial dysfunction, which strongly correlates with cardiovascular disease (CVD). This study investigates the protective effects of rivaroxaban, a FXa inhibitor, on the glycocalyx under oxidative stress condition. We examined the impact of rivaroxaban on human umbilical vein endothelial cells (HUVECs) exposed to acute and chronic H₂O₂-induced oxidative stress. Rivaroxaban dose-dependently suppressed syndecan-1, a key component of the glycocalyx, shedding from cell surface, and enhanced protease-activated receptor (PAR)1-PAR2/ phosphatidylinositol-3-kinase (PI3K)-dependent cell viability after acute induction of H2O2. This protective effect was linked to the translocation of IQGAP1, a scaffold protein that modulates the actin cytoskeleton, to the perinucleus from the cell membrane. Under chronic H2O2 treatments, rivaroxaban improves cell viability accompanied by an increase in hyaluronidase activities, aiding the turnover and remodeling of hyaluronic acid within the glycocalyx. We identify that rivaroxaban protects against oxidative stress-induced endothelial glycocalyx damage and cell viability through IQGAP1/PAR1-2/PI3K/Akt pathway, offering a potential to be a therapeutic target for CVD prevention.

Examining Downstream Effects of Concizumab in Hemophilia A with a Mathematical Modeling Approach

BackgroundTissue factor pathway inhibitor (TFPI) is an anticoagulant protein that inhibits FXa, the TF-FVIIa-FXa complex, and early forms of the prothrombinase complex. Concizumab is a monoclonal antibody that blocks FXa inhibition by TFPI and reduces bleeding in hemophilia. ObjectivesTo examine how concizumab impacts various reactions of TFPI to restore thrombin generation in hemophilia A using mathematical models. MethodsA compartment model was used to estimate plasma concentrations of free concizumab and its complexes with TFPIα and TFPIβ. Concizumab was integrated into a flow-mediated mathematical model of coagulation and a small injury was simulated under hemophilia A conditions. Simulations were then analyzed to determine how concizumab’s blockade of TFPI anticoagulant activities, specifically the inhibition of FXa in plasma and on platelets, inhibition of TF:VIIa at the subendothelium, and prior sequestration of plasma TFPIα to the endothelium via TFPIβ, altered thrombin generation. ResultsConcizumab improved simulated thrombin generation in hemophilia A by simultaneously altering all three mechanisms of TFPI anticoagulant blockade examined. Concizumab sequesters ∼75% of plasma TFPIα through formation of ternary TFPIα-concizumab-TFPIβ-complexes. For all TF levels, reducing the TFPIα plasma concentration had the largest impact on the lag time followed by blocking TFPIα inhibition of TF:VIIa:FXa and subsequently followed by blocking TFPIα inhibition of FXa in plasma and on the platelet surface. ConclusionsThe effectiveness of concizumab is mediated through blockade of TFPI anticoagulant activities in plasma and on multiple physiological surfaces. An important and previously unrecognized function of concizumab was sequestration of plasma TFPIα to the endothelium.

Long-term FXa inhibition attenuates thromboinflammation after acute myocardial infarction and stroke by platelet proteome alteration

Long-term FXa inhibition attenuates thromboinflammation after acute myocardial infarction and stroke by platelet proteome alteration

Characterisation of the pharmacokinetic and pharmacodynamic relationship of milvexian in total knee replacement patients

Abstract Background Milvexian, an oral factor XIa inhibitor, is currently being evaluated in patients at risk for thrombotic events due to atrial fibrillation, ischaemic stroke, or acute coronary syndrome. The exposure-response relationship between clinical efficacy and safety endpoints and milvexian pharmacokinetic (PK) metrics was recently submitted as a separate publication. Characterisation of the relationship between the coagulation pharmacodynamic (PD) markers versus milvexian PK metrics at the patient level has yet to be reported. Purpose This analysis characterised the relationship between the coagulation biomarkers, activated partial thromboplastin time (aPTT) and prothrombin time (PT), and milvexian systemic exposure in patients undergoing total knee replacement (TKR) evaluated in the AXIOMATIC-TKR study. Methods A population pharmacokinetic (PopPK) model was previously developed and characterised the PK of milvexian in TKR patients well. The PK/PD relationships between observed aPTT and PT versus PopPK model estimated time-matched milvexian plasma concentrations via nonlinear mixed effects modeling. The relationship between key clinical safety endpoints (e.g., any bleeding or clinically relevant non-major bleeding) and individual PD marker change (e.g., aPTT ratio to baseline) was also explored. Results The aPTT increased with increasing plasma concentration of milvexian over the range of doses evaluated in the study (25mg QD to 200mg BID). An Emax type of model reasonably characterised the PK/PD relationship between the aPTT and model predicted time-matched milvexian plasma concentration, which is consistent with previously observed relationships in healthy volunteers. No change was observed in PT with increased milvexian exposure. No obvious relationship was identified between any (including clinically relevant non-major) bleeding and aPTT ratio to baseline. Conclusions Increased milvexian exposure is directly correlated with aPTT prolongation over the range of doses evaluated in the TKR study. There was no obvious relationship between any (including clinically relevant non-major) bleeding and aPTT ratio. The PK/PD relationship of aPTT without a parallel relationship in PT distinguishes milvexian, a FXIa inhibitor, from previously studied FXa inhibitors. These analyses were a complementary component in dose selection for the milvexian Phase 3 program. Figure 1. PK/PD relationship between aPTT (left) and PT (right) and estimated time-matched plasma concentration (AXIOMATIC-TKR study)

3-Factor prothrombin complex concentrate versus 4-factor prothrombin complex concentrate for the reversal of oral factor Xa inhibitors.

Multiple agents exist for the reversal of oral Factor Xa inhibitor (FXa) associated bleeding, including Coagulation FXa Recombinant, Inactivated zhzo (andexanet alfa) and 4-factor prothrombin complex concentrate (4F-PCC). While classified as a 3F-PCC product, Profilnine contains up to 35IU of Factor VII (per 100IU of Factor IX) in addition to therapeutic levels of Factors II, IX, and X, and has demonstrated a similar impact on prothrombin time and blood product usage in non-warfarin related bleeding. This was a retrospective, multicenter study at four medical centers of adult patients who presented with major bleeding associated with oral FXa inhibitors and received either 4F-PCC (n = 64) or 3F-PCC (n = 61). The primary outcome was hemostatic effectiveness. Secondary outcomes included the incidence of thromboembolism, in-hospital mortality, and length of stay. The most common indication for reversal was intracranial bleeding. For the primary outcome, 84% of all patients were rated as effective with no difference noted between the groups (p = 0.81). No significant difference between groups was found in the multivariable analysis adjusting for baseline differences between groups including race, total body weight, type of bleeding, and the use of antiplatelet therapy. There was no difference in the length of stay, in-hospital mortality, or the incidence of thromboembolism between the groups. Overall, no significant differences were found in the effectiveness or safety of 4F-PCC and 3F-PCC use in the management of oral FXa inhibitor-associated bleeding. Further investigations are warranted to explore the use of 3F-PCC for this indication and its safety and effectiveness.

Pharmacodynamics of Rivaroxaban and Dabigatran in Adults with Diffuse Large B-Cell Lymphoma Receiving R-CHOP Immunochemotherapy.

Background/Objectives: Rivaroxaban and dabigatran are commonly used for thromboembolic disease management in active cancer patients. However, limited research explores the impact of concurrent chemotherapy on the pharmacodynamics of direct oral anticoagulants (DOAC). The aim of our study was to evaluate the impact of combined chemotherapy with rivaroxaban and dabigatran on the pharmacodynamics in patients with diffuse large B-cell lymphoma (DLBCL).; Methods: This was a prospective, pharmacodynamic study. Eligible subjects were ≥18 years old, diagnosed with DLBCL and initiating R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) immunochemotherapy. The enrolled adults received either rivaroxaban (10 mg once daily) or dabigatran etixalate (110 mg twice daily). Plasma anti-factor Xa (FXa) in participants on rivaroxaban and diluted thrombin time (dTT) in participants on dabigatran were assessed over the dosing interval before and after R-CHOP administration. Pharmacodynamic parameters of rivaroxaban and dabigatran were determined using a non-compartmental analysis.; Results: Twenty-six adults participated, with twelve in the rivaroxaban group and fourteen in the dabigatran group. The mean age was 59 ± 14.4 years. In the rivaroxaban group, the AUEC of FXa inhibition showed no significant change after R-CHOP (mean difference 3.8 ng·h/mL, 95% confidence interval (CI) -155.4 to 163.0, p = 0.96). Similarly, in the dabigatran group, the AUEC of dTT remained unchanged post R-CHOP (mean difference 54.41 ng·h/mL, 95% CI -99.09 to 207.9 ng/mL, p = 0.46). However, the median time-to-peak dTT was significantly faster with R-CHOP (3 h, [min-max, 1.5-8] compared to without it (4 h, [min-max, 3-8], p = 0.04); Conclusions: Concurrent R-CHOP chemotherapy did not significantly impact FXa inhibition by rivaroxaban or dTT by dabigatran. The time-to-peak dTT was faster when dabigatran was administered with R-CHOP.

Monitoring the efficiency of reversal on anti-Xa direct oral anticoagulants using point-of-care viscoelastic testing

Bleeding events in patients receiving direct oral anticoagulation (DOAC) can be life-threatening even at therapeutic DOAC plasma concentrations, as anticoagulation impairs hemostasis and should therefore be identified immediately after hospital admission. The anticoagulatory effects of DOAC are typically not measurable in standard coagulation tests, such as PT or aPTT. Specific calibrated anti-FXa-tests allow specific drug monitoring, but they are too time-consuming for critical bleeding events and are commonly not available for 24 h/7 days in routine care. However, recent advances in point-of-care (POC) viscoelastic testing (VET) have shown a promising approach for rapid and quantitative detection of DOAC plasma concentrations using the Russell viper venom factor V activator (RVV for FXa-inhibitors) test or the ecarin clotting time (thrombin inhibitors). In acute bleeding situations, direct FXa inhibitors can be reversed by specific antidote andexanet alfa or hemostasis can be improved by prothrombin complex factor concentrates (PCCs). After reversal, confirmation of reversal efficacy is often requested, but no routine assays are currently available. Thus, the emergency management of bleeding DOAC patients is usually “blinded” with regard to reversal efficacy. POC VET laboratory assays might therefore also be helpful for measuring DOAC effects after reversal. We present a case series demonstrating the usefulness of RVV-clotting time post-DOAC reversal with andexanet alfa.

Impact of elevated direct factor Xa inhibitor plasma levels on perioperative blood loss in patients undergoing urgent surgery.

Data on the perioperative bleeding risk associated with elevated plasma levels of direct factor Xa inhibitors (FXa inhibitors) are limited. This study examines perioperative red blood cell (RBC) loss in patients undergoing urgent surgery with a residual FXa inhibitor level exceeding 100 mcg/L and without preoperative FXa inhibitor reversal. This retrospective analysis includes data from 32 patients who underwent urgent noncardiac surgery between 2018 and 2022. This study aims to analyze perioperative RBC loss in patients undergoing urgent surgery with a residual FXa inhibitor level exceeding 100 mcg/L and without preoperative FXa inhibitor antidote-based reversal or unspecific treatment with 4-factor prothrombin complex concentrate (PCC). All patients were managed using a watch-and-wait strategy. The last determination of FXa inhibitor plasma concentration prior to surgery showed a median of 245 mcg/L (IQR 144-345), with a median time interval of 3.8 h (IQR 2.4-7.2) before incision. Median RBC loss during surgery was 49 mL (IQR 0-253), 189 mL (IQR 104-217) until POD1 and 254 mL (IQR 58-265) until POD3. Only one patient required intraoperative treatment with 4-factor-PCC and none required reversal with andexanet alfa. Linear regression models found no significant influence of FXa inhibitor plasma levels on intraoperative RBC loss. Rivaroxaban was associated with higher RBC loss until postoperative Day 1 compared with apixaban. No thromboembolic events were observed. Despite markedly elevated plasma concentrations of residual direct FXa inhibitors, perioperative RBC loss was limited in patients undergoing urgent noncardiac surgery. The intraoperative watch-and-wait strategy with selective intraoperative FXa inhibitor reversal or treatment only when required appears to be an appropriate approach.

Treatment of atrial fibrillation and venous thromboembolism with factor Xa inhibitors in severely obese patients

BackgroundA paucity of data exists to support the use of factor (F)Xa inhibitors in severely obese patients with a weight of ≥150 kg or body mass index (BMI) of ≥50 kg/m2. ObjectivesThe purpose of this study was to evaluate whether FXa inhibitors are as safe and effective as warfarin for the treatment of atrial fibrillation (AF) and/or venous thromboembolism (VTE) in individuals with a BMI of ≥50 kg/m2 and/or weight of ≥150 kg. MethodsThis was a multicenter retrospective cohort study of severely obese adult patients with AF and/or VTE treated with a FXa inhibitor or warfarin. The primary effectiveness outcome was composite odds of stroke, systemic embolism, or VTE; the primary safety outcome was odds of major bleeding. Secondary outcomes included incidence of stroke or systemic embolism, VTE, major bleeding, clinically relevant nonmajor bleeding, all-cause mortality, change in anticoagulation, and total number of hospital encounters. Outcomes were assessed for 12 months following initiation of study drug. ResultsA total of 1736 patients were included. The mean weight and BMI of the overall cohort were 164.4 kg and 54.6 kg/m2, respectively. There was no difference in odds of stroke, systemic embolism or VTE (odds ratio, 1.005; 95% CI, 0.6-1.68), or major bleeding (odds ratio, 0.9; 95% CI, 0.47-1.7) between groups. ConclusionThese data suggest that apixaban and rivaroxaban are safe and effective alternatives to warfarin for the treatment of AF and/or VTE in individuals with a BMI of ≥50 kg/m2 and/or weight of ≥150 kg.

Chemical Synthesis and Structure-Activity Relationship Studies of the Coagulation Factor Xa Inhibitor Tick Anticoagulant Peptide from the Hematophagous Parasite Ornithodoros moubata.

Tick Anticoagulant Peptide (TAP), a 60-amino acid protein from the soft tick Ornithodoros moubata, inhibits activated coagulation factor X (fXa) with almost absolute specificity. Despite TAP and Bovine Pancreatic Trypsin Inhibitor (BPTI) (i.e., the prototype of the Kunitz-type protease inhibitors) sharing a similar 3D fold and disulphide bond topology, they have remarkably different amino acid sequence (only ~24% sequence identity), thermal stability, folding pathways, protease specificity, and even mechanism of protease inhibition. Here, fully active and correctly folded TAP was produced in reasonably high yields (~20%) by solid-phase peptide chemical synthesis and thoroughly characterised with respect to its chemical identity, disulphide pairing, folding kinetics, conformational dynamics, and fXa inhibition. The versatility of the chemical synthesis was exploited to perform structure-activity relationship studies on TAP by incorporating non-coded amino acids at positions 1 and 3 of the inhibitor. Using Hydrogen-Deuterium Exchange Mass Spectrometry, we found that TAP has a remarkably higher conformational flexibility compared to BPTI, and propose that these different dynamics could impact the different folding pathway and inhibition mechanisms of TAP and BPTI. Hence, the TAP/BPTI pair represents a nice example of divergent evolution, while the relative facility of TAP synthesis could represent a good starting point to design novel synthetic analogues with improved pharmacological profiles.

Preparation of an anticoagulant polyethersulfone membrane by immobilizing FXa inhibitors with a polydopamine coating

Anticoagulation treatment for patients with high bleeding risk during hemodialysis is challenging. Contact between the dialysis membrane and the blood leads to protein adsorption and activation of the coagulation cascade reaction. Activated coagulation Factor X (FXa) plays a central role in thrombogenesis, but anticoagulant modification of the dialysis membrane is rarely targeted at FXa. In this study, we constructed an anticoagulant membrane using the polydopamine coating method to graft FXa inhibitors (apixaban and rivaroxaban) on the membrane surface. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the membranes. The apixaban- and rivaroxaban-modified membranes showed lower water contact angles, decreased albumin protein adsorption, and suppressed platelet adhesion and activation compared to the unmodified PES membranes. Moreover, the modified membranes prolonged the blood clotting times in both the intrinsic and extrinsic coagulation pathways and inhibited FXa generation and complement activation, which suggested that the modified membrane enhanced biocompatibility and antithrombotic properties through the inhibition of FXa. Targeting FXa to design antithrombotic HD membranes or other blood contact materials might have great application potential.

Blood Lines: Intraspecific and Interspecific Variations in Anticoagulant Actions of Agkistrodon Viperid Venoms.

This study investigated the intraspecific and interspecific variability in the venom effects of Agkistrodon viperid snake species and subspecies (eleven venoms total) on plasma clotting times, fibrinogen levels, and fibrin clot strength. Significant delays in plasma clotting time were observed for A. conanti, A. contortrix mokasen, A. contortrix phaeogaster, A. howardgloydi, A. piscivorus leucostoma, and A. piscivorus piscivorus. Notably, the phylogenetically disjunct lineages A. conanti, A. contortrix mokasen, and A. howardgloydi exhibited the most potent anticoagulant effects, indicating the independent amplification of a basal trait. Inhibition assays with the activated clotting enzymes Factors XIa, IXa, Xa, and IIa (thrombin) revealed that FXa inhibition is another basal trait amplified independently on multiple occasions within the genus, but with A. howardgloydi, notably more potent than all others. Phospholipid degradation and zymogen destruction were identified as mechanisms underlying the variability in venom effects observed experimentally and in previous clinical reports. Thromboelastography demonstrated that the venoms did not clot fibrinogen directly but affected fibrin clot strength by damaging fibrinogen and that thrombin was subsequently only able to cleave into weak, unstable clots. The ability to activate Protein C, an endogenous anticoagulant enzyme, varied across species, with some venoms exceeding that of A. contortrix contortrix, which previously yielded the protein diagnostic agent Protac®. Phylogenetic analysis suggested that both fibrinogen degradation and Protein C activation were each amplified multiple times within the genus, albeit with negative correlation between these two modes of action. This study highlights the evolutionary, clinical, and biodiscovery implications of venom variability in the Agkistrodon species, underscoring their dynamic evolution, emphasising the need for tailored clinical approaches, and highlighting the potential for novel diagnostic and therapeutic developments inspired by the unique properties of snake venoms.

Factor XI inhibitors: a new option for the prevention and treatment of cancer-associated thrombosis

Venous thromboembolism (VTE) is a relatively common complication in cancer patients with potentially dire consequences. Anticoagulants are the mainstay of treatment of cancer-associated VTE. The anticoagulants most often used are low-molecular-weight heparin (LMWH) and direct oral factor (F) Xa inhibitors, which include apixaban, edoxaban, and rivaroxaban. Most guidelines recommend primary VTE prophylaxis with LMWH, apixaban, or rivaroxaban after abdominal or pelvic cancer surgery, or in high-risk ambulatory cancer patients. Both oral FXa inhibitors and LMWH have limitations. LMWH requires daily subcutaneous injections, and because of its renal clearance, its use may be problematic in patients with severe kidney disease. The risk of bleeding with oral FXa inhibitors may be higher than with LMWH in patients with intraluminal gastrointestinal or genitourinary cancers. Other problems with oral FXa inhibitors include potential drug-drug interactions and dosing issues in patients with thrombocytopenia or severe kidney or liver disease. Therefore, there remains a need for convenient and safer anticoagulants for VTE treatment in cancer patients. FXI has emerged as a potentially safer target for anticoagulants than FXa because FXI is essential for thrombosis, but mostly dispensable for hemostasis. This review summarizes the currently available therapeutic options for cancer-associated VTE, highlights knowledge gaps, and discusses the potential of FXI inhibitors to address key unmet clinical needs in this vulnerable patient population.

Activated factor X stimulates atrial endothelial cells and tissues to promote remodelling responses through AT1R/NADPH oxidases/SGLT1/2.

Atrial fibrillation (AF), the most common cardiac arrhythmia favouring ischemic stroke and heart failure involves left atrial remodelling, fibrosis and a complex interplay between cardiovascular risk factors. This study examined whether activated factor X (FXa) induces pro-remodelling and pro-fibrotic responses in atrial endothelial cells (AECs) and human atrial tissues and determined the underlying mechanisms. AECs collected from porcine hearts and human right atrial appendages (RAA) from patients undergoing heart surgery. Protein expression levels were assessed by Western blot and immunofluorescence staining, mRNA levels by RT-qPCR, formation of reactive oxygen species (ROS) and NO using fluorescent probes, thrombin and angiotensin II generation by specific assays, fibrosis by Sirius red staining and senescence by senescence-associated beta-galactosidase (SA-β-gal) activity. In AECs, FXa increased ROS formation, senescence (SA-β-gal activity, p53, p21), angiotensin II generation and the expression of pro-inflammatory (VCAM-1, MCP-1), pro-thrombotic (tissue factor), pro-fibrotic (TGF-β and collagen-1/3a) and pro-remodelling (MMP-2/9) markers whereas eNOS levels and NO formation were reduced. These effects were prevented by inhibitors of FXa but not thrombin, protease-activated receptors antagonists (PAR-1/2) and inhibitors of NADPH oxidases, ACE, AT1R, SGLT1/SGLT2. FXa also increased expression levels of ACE1, AT1R, SGLT1/2 proteins which were prevented by SGLT1/2 inhibitors. Human RAA showed tissue factor mRNA levels that correlated with markers of endothelial activation, pro-remodelling and pro-fibrotic responses and SGLT1/2 mRNA levels. They also showed protein expression levels of ACE1, AT1R, p22phox, SGLT1/2, and immunofluorescence signals of nitrotyrosine and SGLT1/2 colocalized with those of CD31. FXa increased oxidative stress levels which were prevented by inhibitors of the AT1R/NADPH oxidases/SGLT1/2 pathway. FXa promotes oxidative stress triggering premature endothelial senescence and dysfunction associated with pro-thrombotic, pro-remodelling and pro-fibrotic responses in AECs and human RAA involving the AT1R/NADPH oxidases/SGLT1/2 pro-oxidant pathway. Targeting this pathway may be of interest to prevent atrial remodelling and the progression of atrial fibrillation substrate.

Minimally modified human blood coagulation factor X to bypass direct factor Xa inhibitors

BackgroundDirect oral factor (F)Xa inhibitors are widely used as alternatives to conventional vitamin K antagonists in managing venous thromboembolism and nonvalvular atrial fibrillation. Unfortunately, bleeding-related adverse events remain a major concern in clinical practice. In case of bleeding or emergency surgery, rapid-onset reversal agents may be required to counteract the anticoagulant activity. ObjectivesThe ability of FXa variants to bypass the direct oral FXa inhibitors was assessed. MethodsHuman FXa variants were generated through substitution of phenylalanine 174 (F174) for either alanine, isoleucine, or serine. FXa variants were stably expressed in HEK293 cells and purified to homogeneity using ion-exchange chromatography. ResultsF174-substituted human FX variants demonstrated efficacy in restoring thrombin generation in plasma containing direct FXa inhibitors (apixaban, rivaroxaban, edoxaban). Their ability to bypass the anticoagulant effects stems from a significantly reduced sensitivity for the direct FXa inhibitors due to a decrease in binding affinity determined using molecular dynamics simulations and free energy computation. Furthermore, F174 modification resulted in a partial loss of inhibition by tissue factor pathway inhibitor, enhancing the procoagulant effect of F174-substituted FX. Consequently, the F174A- and F174S-substituted FX variants effectively counteracted the effects of 2 widely used anticoagulants, apixaban and rivaroxaban, in plasma of atrial fibrillation and venous thromboembolism patients. ConclusionThese human FX variants have the potential to serve as a rescue reversal strategy to overcome the effect of direct FXa inhibitors in case of life-threatening bleeding events or emergency surgical interventions.

Abstract 3095: Characterization Of Interactions Between Skeletal Muscle Myosin And Activated Factor XI

Background: We recently demonstrated that the procoagulant activity of skeletal muscle myosin (SkM) involved the binding of coagulation factor (F) XI to enhance FXI activation by thrombin. However, the impact of SkM on the enzymatic activities of activated FXI (FXIa) remains unclear. Aims: Determine the influence of SkM interactions on the expression of FXIa activities. Methods: Binding studies between FXIa and SkM were conducted using biolayer interferometry (BLI). Kallikrein, a FXIa homolog, served as a negative control. The interactions between SkM and FXIa were investigated through fluorescence spectroscopy using dansyl-labeled FXIa. Chromogenic assays for FXIIa were employed to measure FXII activation by FXIa. Tissue factor pathway inhibitor (TFPI) inactivation by FXIa was assessed by determining FXa inhibition by TFPI using FX chromogenic assays. Quantification of complement factor H (CFH) cleavage by FXIa as well as FV activation by FXIa were carried out using SDS PAGE and Coomassie blue staining. Results: BLI data showed that SkM exhibited a high binding affinity for FXIa with a dissociation constant of 1.6 nM, whereas SkM did not bind kallikrein. The addition of SkM induced a 9 nm shift in the emission spectrum of dansyl-labeled FXIa. The presence of SkM increased the rate of feedback FXII activation by FXIa but not by kallikrein. The addition of SkM inhibitors, trifluoperazine and blebbistatin, reduced the enhancement effect of SkM on the ability of FXIa to activate FXII. Furthermore, SkM increased the rate of enzymatic inactivation of TFPI by FXIa, the rate of cleavage of CFH by FXIa, and the rate of activation of FV by FXIa. Conclusions: SkM binds with high affinity to FXIa and serves as a co-factor to enhance multiple different enzymatic activities of FXIa. Future work is needed to examine the multiple procoagulant activities of SkM in the setting of hemostasis and acute trauma.

Ex Vivo Antiplatelet Effects of Oral Anticoagulants.

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. 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. 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. 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.

Andexanet Alfa (Ondexxya)


 CADTH reimbursement reviews are comprehensive assessments of the clinical effectiveness and cost-effectiveness, as well as patient and clinician perspectives, of a drug or drug class.
 The assessments inform non-binding recommendations that help guide the reimbursement decisions of Canada's federal, provincial, and territorial governments, with the exception of Quebec.
 This review assesses andexanet alfa (Ondexxya), 200 mg, powder for solution for infusion, IV infusion.
 Indication: For adult patients treated with FXa inhibitors (rivaroxaban or apixaban) when rapid reversal of anticoagulation is needed due to life-threatening or uncontrolled bleeding.

Interruption of perivascular and perirenal adipose tissue thromboinflammation rescues prediabetic cardioautonomic and renovascular deterioration.

The cardiovascular and renovascular complications of metabolic deterioration are associated with localized adipose tissue dysfunction. We have previously demonstrated that metabolic impairment delineated the heightened vulnerability of both the perivascular (PVAT) and perirenal adipose tissue (PRAT) depots to hypoxia and inflammation, predisposing to cardioautonomic, vascular and renal deterioration. Interventions either addressing underlying metabolic disturbances or halting adipose tissue dysfunction rescued the observed pathological and functional manifestations. Several lines of evidence implicate adipose tissue thromboinflammation, which entails the activation of the proinflammatory properties of the blood clotting cascade, in the pathogenesis of metabolic and cardiovascular diseases. Despite offering valuable tools to interrupt the thromboinflammatory cycle, there exists a significant knowledge gap regarding the potential pleiotropic effects of anticoagulant drugs on adipose inflammation and cardiovascular function. As such, a systemic investigation of the consequences of PVAT and PRAT thromboinflammation and its interruption in the context of metabolic disease has not been attempted. Here, using an established prediabetic rat model, we demonstrate that metabolic disturbances are associated with PVAT and PRAT thromboinflammation in addition to cardioautonomic, vascular and renal functional decline. Administration of rivaroxaban, a FXa inhibitor, reduced PVAT and PRAT thromboinflammation and ameliorated the cardioautonomic, vascular and renal deterioration associated with prediabetes. Our present work outlines the involvement of PVAT and PRAT thromboinflammation during early metabolic derangement and offers novel perspectives into targeting adipose tissue thrombo-inflammatory pathways for the management its complications in future translational efforts.

The use of andexanet alpha in the Polish setting: An interdisciplinary protocol. Expert consensus statement of the Polish Cardiac Society.

Andexanet alfa (AA) is a recombinant inactive analog of human activated factor X (FXa), effectively reversing the effects of its inhibitors - rivaroxaban and apixaban, which are available in Poland. The drug was approved for clinical use registration after the publication of the results of the ANNEXA-4 trial (Andexanet Alfa, a Novel Antidote to the Anticoagulation Effects of FXa Inhibitors 4), in which its efficacy in restoring hemostasis in life-threatening hemorrhages in patients receiving using the aforementioned anticoagulants was demonstrated. Hence, AA is now recommended for patients on apixaban or rivaroxaban therapy with massive and uncontrollable hemorrhages, including hemorrhagic strokes (HS) and gastrointestinal bleeding. Drug-specific chromogenic anti-Xa assays are generally best suited for estimating rivaroxaban and apixaban plasma levels, aside from direct assessment of their concentrations. The absence of anti-Xa activity, determined using these assays, allows us to rule out the presence of clinically relevant plasma concentrations of any FXa inhibitor. On the other hand, the dose of AA should not be modified based on the results of coagulation tests, as it depends solely on the time that elapsed since the last dose of FXa inhibitor and oon the dose and type of FXa inhibitor. AA is administered as an intravenous (i.v.) bolus, followed by an i.v. infusion of the drug. The maximum reversal of anti-Xa activity occurs within two minutes of the end of the bolus treatment, with the continuation of the continuous i.v. infusion allowing the effect to be maintained for up to two hours afterwards. Because anticoagulant activity can reappear after the infusion is completed, it is currently unclear at what point after AA administration FXa inhibitors or heparin should be re-administered. In Poland AA is starting to become available and its urgent need to administer it to patients with severe bleeding on apixaban or rivaroxaban.