Andexanet for Factor Xa Inhibitor-Associated Acute Intracerebral Hemorrhage.

BACKGROUND: Patients with acute intracerebral hemorrhage who are receiving factor Xa inhibitors have a risk of hematoma expansion. The effect of andexanet alfa, an agent that reverses the effects of factor Xa inhibitors, on hematoma volume expansion has not been well studied. METHODS: We randomly assigned, in a 1:1 ratio, patients who had taken factor Xa inhibitors within 15 hours before having an acute intracerebral hemorrhage to receive andexanet or usual care. The primary end point was hemostatic efficacy, defined by expansion of the hematoma volume by 35% or less at 12 hours after baseline, an increase in the score on the National Institutes of Health Stroke Scale of less than 7 points (scores range from 0 to 42, with higher scores indicating worse neurologic deficit) at 12 hours, and no receipt of rescue therapy between 3 hours and 12 hours. Safety end points were thrombotic events and death. RESULTS: A total of 263 patients were assigned to receive andexanet, and 267 to receive usual care. Efficacy was assessed in an interim analysis that included 452 patients, and safety was analyzed in all 530 enrolled patients. Atrial fibrillation was the most common indication for factor Xa inhibitors. Of the patients receiving usual care, 85.5% received prothrombin complex concentrate. Hemostatic efficacy was achieved in 150 of 224 patients (67.0%) receiving andexanet and in 121 of 228 (53.1%) receiving usual care (adjusted difference, 13.4 percentage points; 95% confidence interval [CI], 4.6 to 22.2; P = 0.003). The median reduction from baseline to the 1-to-2-hour nadir in anti-factor Xa activity was 94.5% with andexanet and 26.9% with usual care (P<0.001). Thrombotic events occurred in 27 of 263 patients (10.3%) receiving andexanet and in 15 of 267 (5.6%) receiving usual care (difference, 4.6 percentage points; 95% CI, 0.1 to 9.2; P = 0.048); ischemic stroke occurred in 17 patients (6.5%) and 4 patients (1.5%), respectively. There were no appreciable differences between the groups in the score on the modified Rankin scale or in death within 30 days. CONCLUSIONS: Among patients with intracerebral hemorrhage who were receiving factor Xa inhibitors, andexanet resulted in better control of hematoma expansion than usual care but was associated with thrombotic events, including ischemic stroke. (Funded by Alexion AstraZeneca Rare Disease and others; ANNEXA-I ClinicalTrials.gov number, NCT03661528.).

Cleavage of the syncytial protein of J paramyxovirus is required for its ability to promote cell-cell fusion.

Cell-cell fusion mediated by most paramyxovirus requires fusion protein (F) and attachment protein (H, HN, or G). The F protein is proteolytic cleaved to be fusogenically active. J paramyxovirus (JPV) has a unique feature in the family Paramyxoviridae: It encodes an integral membrane protein, syncytial protein (SP, formerly known as transmembrane protein, TM), which is essential in JPV-promoted cell-cell fusion (i.e., syncytial). In this study, we report that cleavage of SP is essential for its syncytial-promoting activity. We have identified the cleavage site of SP at amino acid residues 172 to 175, LKTG, and deletion of the "LKTG" residues abolished SP protein cleavage and its ability to promote cell-cell fusion. Replacing the cleavage site LKTG with a factor Xa protease cleavage site allows cleavage of the SP with factor Xa protease and restores its ability to promote cell-cell fusion. Furthermore, results from a hemifusion assay indicate that cleavage of SP plays an important role in the progression from the intermediate hemifusion state to a complete fusion. This work indicates that SP has many characteristics of a fusion protein. We propose that SP is likely a cell-cell fusion-promoting protein.

Cryo-EM structure of coagulation factor V short.

Coagulation factor V (fV) is the precursor of activated fV (fVa), an essential component of the prothrombinase complex required for the rapid activation of prothrombin in the penultimate step of the coagulation cascade. In addition, fV regulates the tissue factor pathway inhibitor α (TFPIα) and protein C pathways that inhibit the coagulation response. A recent cryogenic electron microscopy (cryo-EM) structure of fV has revealed the architecture of its A1-A2-B-A3-C1-C2 assembly but left the mechanism that keeps fV in its inactive state unresolved because of an intrinsic disorder in the B domain. A splice variant of fV, fV short, carries a large deletion of the B domain that produces constitutive fVa-like activity and unmasks epitopes for the binding of TFPIα. The cryo-EM structure of fV short was solved at 3.2 Å resolution and revealed the arrangement of the entire A1-A2-B-A3-C1-C2 assembly. The shorter B domain stretches across the entire width of the protein, making contacts with the A1, A2, and A3 domains but suspended over the C1 and C2 domains. In the portion distal to the splice site, several hydrophobic clusters and acidic residues provide a potential binding site for the basic C-terminal end of TFPIα. In fV, these epitopes may bind intramolecularly to the basic region of the B domain. The cryo-EM structure reported in this study advances our understanding of the mechanism that keeps fV in its inactive state, provides new targets for mutagenesis and facilitates future structural analysis of fV short in complex with TFPIα, protein S, and fXa.

The Prothrombin-Prothrombinase Interaction.

The hemostatic response to vascular injury entails a sequence of proteolytic events where several inactive zymogens of the trypsin family are converted to active proteases. The cascade starts with exposure of tissue factor from the damaged endothelium and culminates with conversion of prothrombin to thrombin in a reaction catalyzed by the prothrombinase complex composed of the enzyme factor Xa, cofactor Va, Ca2+, and phospholipids. This cofactor-dependent activation is paradigmatic of analogous reactions of the blood coagulation and complement cascades, which makes elucidation of its molecular mechanism of broad significance to the large class of trypsin-like zymogens to which prothrombin belongs. Because of its relevance as the most important reaction in the physiological response to vascular injury, as well as the main trigger of pathological thrombotic complications, the mechanism of prothrombin activation has been studied extensively. However, a molecular interpretation of this mechanism has become available only recently from important developments in structural biology. Here we review current knowledge on the prothrombin-prothrombinase interaction and outline future directions for the study of this key reaction of the coagulation cascade.

Final Study Report of Andexanet Alfa for Major Bleeding With Factor Xa Inhibitors.

BACKGROUND: Andexanet alfa is a modified recombinant inactive factor Xa (FXa) designed to reverse FXa inhibitors. ANNEXA-4 (Andexanet Alfa, a Novel Antidote to the Anticoagulation Effects of Factor Xa Inhibitors) was a multicenter, prospective, phase-3b/4, single-group cohort study that evaluated andexanet alfa in patients with acute major bleeding. The results of the final analyses are presented. METHODS: Patients with acute major bleeding within 18 hours of FXa inhibitor administration were enrolled. Co-primary end points were anti-FXa activity change from baseline during andexanet alfa treatment and excellent or good hemostatic efficacy, defined by a scale used in previous reversal studies, at 12 hours. The efficacy population included patients with baseline anti-FXa activity levels above predefined thresholds (≥75 ng/mL for apixaban and rivaroxaban, ≥40 ng/mL for edoxaban, and ≥0.25 IU/mL for enoxaparin; reported in the same units used for calibrators) who were adjudicated as meeting major bleeding criteria (modified International Society on Thrombosis and Haemostasis definition). The safety population included all patients. Major bleeding criteria, hemostatic efficacy, thrombotic events (stratified by occurring before or after restart of either prophylactic [ie, a lower dose, for prevention rather than treatment] or full-dose oral anticoagulation), and deaths were assessed by an independent adjudication committee. Median endogenous thrombin potential at baseline and across the follow-up period was a secondary outcome. RESULTS: There were 479 patients enrolled (mean age, 78 years; 54% male; 86% White); 81% were anticoagulated for atrial fibrillation, and the median time was 11.4 hours since last dose, with 245 (51%) on apixaban, 176 (37%) on rivaroxaban, 36 (8%) on edoxaban, and 22 (5%) on enoxaparin. Bleeding was predominantly intracranial (n=331 [69%]) or gastrointestinal (n=109 [23%]). In evaluable apixaban patients (n=172), median anti-FXa activity decreased from 146.9 ng/mL to 10.0 ng/mL (reduction, 93% [95% CI, 94-93]); in rivaroxaban patients (n=132), it decreased from 214.6 ng/mL to 10.8 ng/mL (94% [95% CI, 95-93]); in edoxaban patients (n=28), it decreased from 121.1 ng/mL to 24.4 ng/mL (71% [95% CI, 82-65); and in enoxaparin patients (n=17), it decreased from 0.48 IU/mL to 0.11 IU/mL (75% [95% CI, 79-67]). Excellent or good hemostasis occurred in 274 of 342 evaluable patients (80% [95% CI, 75-84]). In the safety population, thrombotic events occurred in 50 (10%) patients; in 16 patients, these occurred during treatment with prophylactic anticoagulation that began after the bleeding event. No thrombotic episodes occurred after oral anticoagulation restart. Specific to certain populations, reduction of anti-FXa activity from baseline to nadir significantly predicted hemostatic efficacy in patients with intracranial hemorrhage (area under the receiver operating characteristic curve, 0.62 [95% CI, 0.54-0.70]) and correlated with lower mortality in patients <75 years of age (adjusted P=0.022; unadjusted P=0.003). Median endogenous thrombin potential was within the normal range by the end of andexanet alfa bolus through 24 hours for all FXa inhibitors. CONCLUSIONS: In patients with major bleeding associated with the use of FXa inhibitors, treatment with andexanet alfa reduced anti-FXa activity and was associated with good or excellent hemostatic efficacy in 80% of patients. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT02329327.

Direct Oral Anticoagulants Versus Warfarin Across the Spectrum of Kidney Function: Patient-Level Network Meta-Analyses From COMBINE AF.

BACKGROUND: There is uncertainty surrounding the use of direct oral anticoagulants (DOACs) in patients with kidney dysfunction. METHODS: Using the COMBINE AF (A Collaboration Between Multiple Institutions to Better Investigate Non-Vitamin K Antagonist Oral Anticoagulant Use in Atrial Fibrillation) database (data from RE-LY [Randomized Evaluation of Long-term Anticoagulation Therapy], ROCKET AF [Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared With Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation], ARISTOTLE [Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation], and ENGAGE AF-TIMI 48 [Effective Anticoagulation With Factor Xa Next Generation in Atrial Fibrillation-Thrombolysis in Myocardial Infarction 48]), we performed an individual patient-level network meta-analysis to evaluate the safety and efficacy of DOACs versus warfarin across continuous creatinine clearance (CrCl). A multivariable Cox model including treatment-by-CrCl interaction with random effects was fitted to estimate hazard ratios for paired treatment strategies (standard-dose DOAC, lower-dose DOAC, and warfarin). Outcomes included stroke and systemic embolism (S/SE), major bleeding, intracranial hemorrhage (ICH), and death. RESULTS: Among 71 683 patients (mean age, 70.6±9.4 years; 37.3% female; median follow-up, 23.1 months), the mean CrCl was 75.5±30.5 mL/min. The incidence of S/SE, major bleeding, ICH, and death increased significantly with worsening kidney function. Across continuous CrCl values down to 25 mL/min, the hazard of major bleeding did not change for patients randomized to standard-dose DOACs compared with those randomized to warfarin (Pinteraction=0.61). Compared with warfarin, standard-dose DOAC use resulted in a significantly lower hazard of ICH at CrCl values <122 mL/min, with a trend for increased safety with DOAC as CrCl decreased (6.2% decrease in hazard ratio per 10-mL/min decrease in CrCl; Pinteraction=0.08). Compared with warfarin, standard-dose DOAC use resulted in a significantly lower hazard of S/SE with CrCl <87 mL/min, with a significant treatment-by-CrCl effect (4.8% decrease in hazard ratio per 10-mL/min decrease in CrCl; Pinteraction=0.01). The hazard of death was significantly lower with standard-dose DOACs for patients with CrCl <77 mL/min, with a trend toward increasing benefit with lower CrCl (2.1% decrease in hazard ratio per 10-mL/min decrease in CrCl; Pinteraction=0.08). Use of lower-dose rather than standard-dose DOACs was not associated with a significant difference in incident bleeding or ICH in patients with reduced kidney function but was associated with a higher incidence4 of death and S/SE. CONCLUSIONS: Standard-dose DOACs are safer and more effective than warfarin down to a CrCl of at least 25 mL/min. Lower-dose DOACs do not significantly lower the incidence of bleeding or ICH compared with standard-dose DOACs but are associated with a higher incidence of S/SE and death. These findings support the use of standard-dose DOACs over warfarin in patients with kidney dysfunction.

New anticoagulant protein from medicinal leech.

The saliva of the medicinal leech contains various anticoagulants. Some of them, such as hirudin, are well known. However, it is reasonable to believe that not all anticoagulant proteins from medicinal leech saliva have been identified. We previously performed a comprehensive study of the transcriptome, genome, and proteome of leech salivary gland cells, which led to the discovery of several previously unknown hypothetical proteins that may have anticoagulant properties. Subsequently, we obtained a series of recombinant proteins and investigated their impact on coagulation in in vitro assays. We identified a previously undescribed protein that exhibited a high ability to suppress coagulation. The His-tagged recombinant protein was expressed in Escherichia coli and purified using metal chelate chromatography. To determine its activity, commonly used coagulation methods were used: activated partial thromboplastin time, prothrombin time, and thrombin inhibition clotting assay. Clotting and chromogenic assays for factor Xa inhibition were performed to evaluate anti-Xa activity. We used recombinant hirudin as a control anticoagulant protein in all experiments. The new protein showed significantly greater inhibition of coagulation than hirudin at the same molar concentrations in the activated partial thrombin time assay. However, hirudin demonstrated better results in the direct thrombin inhibition test, although the tested protein also exhibited the ability to inhibit thrombin. The chromogenic analysis of factor Xa inhibition revealed no activity, whereas the clotting test for factor Xa showed the opposite result. Thus, a new powerful anticoagulant protein has been discovered in the medicinal leech. This protein is homologous to antistatin, with 28 % identical amino acid residues. The recombinant protein was expressed in E. coli. This protein is capable of directly inhibiting thrombin, and based on indirect evidence, other proteases of the blood coagulation cascade have been identified.

Cryo-EM structure of the prothrombin-prothrombinase complex.

The intrinsic and extrinsic pathways of the coagulation cascade converge to a common step where the prothrombinase complex, comprising the enzyme factor Xa (fXa), the cofactor fVa, Ca2+ and phospholipids, activates the zymogen prothrombin to the protease thrombin. The reaction entails cleavage at 2 sites, R271 and R320, generating the intermediates prethrombin 2 and meizothrombin, respectively. The molecular basis of these interactions that are central to hemostasis remains elusive. We solved 2 cryogenic electron microscopy (cryo-EM) structures of the fVa-fXa complex, 1 free on nanodiscs at 5.3-Å resolution and the other bound to prothrombin at near atomic 4.1-Å resolution. In the prothrombin-fVa-fXa complex, the Gla domains of fXa and prothrombin align on a plane with the C1 and C2 domains of fVa for interaction with membranes. Prothrombin and fXa emerge from this plane in curved conformations that bring their protease domains in contact with each other against the A2 domain of fVa. The 672ESTVMATRKMHDRLEPEDEE691 segment of the A2 domain closes on the protease domain of fXa like a lid to fix orientation of the active site. The 696YDYQNRL702 segment binds to prothrombin and establishes the pathway of activation by sequestering R271 against D697 and directing R320 toward the active site of fXa. The cryo-EM structure provides a molecular view of prothrombin activation along the meizothrombin pathway and suggests a mechanism for cleavage at the alternative R271 site. The findings advance our basic knowledge of a key step of coagulation and bear broad relevance to other interactions in the blood.

Mapping the prothrombin-binding site of pseutarin C by site-directed PEGylation.

The prothrombinase complex processes prothrombin to thrombin through sequential cleavage at Arg320 followed by Arg271 when cofactor, factor (f) Va, protease, fXa, and substrate, prothrombin, are all bound to the same membrane surface. In the absence of the membrane or cofactor, cleavage occurs in the opposite order. For the less favorable cleavage site at Arg320 to be cleaved first, it is thought that prothrombin docks on fVa in a way that presents Arg320 and hides Arg271 from the active site of fXa. Based on the crystal structure of the prothrombinase complex from the venom of the Australian eastern brown snake, pseutarin C, we modeled an initial prothrombin docking mode, which involved an interaction with discrete portions of the A1 and A2 domains of fV and the loop connecting the 2 domains, known as the a1-loop. We interrogated the proposed interface by site-directed PEGylation and by swapping the a1-loop in pseutarin C with that of human fV and fVIII and measuring the effect on rate and pathway of thrombin generation. PEGylation of residues within our proposed binding site greatly reduced the rate of thrombin generation, without affecting the pathway, whereas those outside the proposed interface had no effect. PEGylation of residues within the a1-loop also reduced the rate of thrombin generation. The sequence of the a1-loop was found to play a critical role in prothrombin binding and in the presentation of Arg320 for initial cleavage.

Dysregulated platelet function in patients with postacute sequelae of COVID-19.

BACKGROUND: Postacute sequelae of COVID-19 (PASC), also referred to as "Long COVID", sometimes follows COVID-19, a disease caused by SARS-CoV-2. Although SARS-CoV-2 is well known to promote a prothrombotic state, less is known about the thrombosis risk in PASC. Our objective was to evaluate platelet function and thrombotic potential in patients following recovery from SARS-CoV-2, but with clear symptoms of patients with PASC. METHODS: patients with PASC and matched healthy controls were enrolled in the study on average 15 months after documented SARS-CoV-2 infection. Platelet activation was evaluated by light transmission aggregometry (LTA) and flow cytometry in response to platelet surface receptor agonists. Thrombosis in platelet-deplete plasma was evaluated by Factor Xa activity. A microfluidics system assessed thrombosis in whole blood under shear stress conditions. RESULTS: A mild increase in platelet aggregation in patients with PASC through the thromboxane receptor was observed, and platelet activation through the glycoprotein VI (GPVI) receptor was decreased in patients with PASC compared to age- and sex-matched healthy controls. Thrombosis under shear conditions as well as Factor Xa activity were reduced in patients with PASC. Plasma from patients with PASC was an extremely potent activator of washed, healthy platelets - a phenomenon not observed when stimulating healthy platelets after incubation with plasma from healthy individuals. CONCLUSIONS: patients with PASC show dysregulated responses in platelets and coagulation in plasma, likely caused by a circulating molecule that promotes thrombosis. A hitherto undescribed protective response appears to exist in patients with PASC to counterbalance ongoing thrombosis that is common to SARS-CoV-2 infection.

Andexanet alpha versus four-factor prothrombin complex concentrate in DOACs anticoagulation reversal: an updated systematic review and meta-analysis.

BACKGROUND: There is currently a lack of evidence for the comparative effectiveness of Andexanet alpha and four-factor prothrombin complex concentrate (4F-PCC) in anticoagulation reversal of direct oral anticoagulants (DOACs). The primary aim of our systematic review was to verify which drug is more effective in reducing short-term all-cause mortality. The secondary aim was to determine which of the two reverting strategies is less affected by thromboembolic events. METHODS: A systematic review and meta-analysis was performed. RESULTS: Twenty-two studies were analysed in the systematic review and quantitative synthesis. In all-cause short-term mortality, Andexanet alpha showed a risk ratio (RR) of 0.71(95% CI 0.37-1.34) in RCTs and PSMs, compared to 4F-PCC (I2 = 81%). Considering the retrospective studies, the pooled RR resulted in 0.84 (95% CI 0.69-1.01) for the common effects model and 0.82 (95% CI 0.63-1.07) for the random effects model (I2 = 34.2%). Regarding the incidence of thromboembolic events, for RCTs and PSMs, the common and the random effects model exhibited a RR of 1.74 (95% CI 1.09-2.77), and 1.71 (95% CI 1.01-2.89), respectively, for Andexanet alpha compared to 4F-PCC (I2 = 0%). Considering the retrospective studies, the pooled RR resulted in 1.21 (95% CI 0.87-1.69) for the common effects model and 1.18 (95% CI 0.86-1.62) for the random effects model (I2 = 0%). CONCLUSION: Considering a large group of both retrospective and controlled studies, Andexanet alpha did not show a statistically significant advantage over 4F-PCC in terms of mortality. In the analysis of the controlled studies alone, Andexanet alpha is associated with an increased risk of thromboembolic events. CLINICAL TRIAL REGISTRATION: PROSPERO: International prospective register of systematic reviews, 2024, CRD42024548768.

Antithrombin supplementation attenuates heparin resistance in plasma spiked with Gla-domainless factor Xa S195A in vitro.

BACKGROUND: Andexanet alfa is a Gla-domainless mutant (S195A) factor Xa (GDXa) approved for acute reversal of oral factor Xa inhibitors. Cardiac surgery patients exposed to andexanet before cardiopulmonary bypass often exhibit severe heparin resistance. There is a paucity of data on the effectiveness and optimal dosage of antithrombin use in this setting. The objective of this study was to evaluate the in vitro effect of increased heparin with antithrombin levels on attenuating heparin resistance induced by GDXa. METHODS: Heparinised normal pooled plasma and cardiopulmonary bypass plasma were spiked with GDXa 4 µM. Tissue factor-activated thrombin generation was used to assess heparin reversal effects of GDXa and restoration of anticoagulation with additional heparin with and without antithrombin. Serum thrombin-antithrombin complex, antithrombin activity, and tissue factor pathway inhibitor were also measured in tissue factor-activated, recalcified cardiopulmonary bypass plasma spiked with GDXa. RESULTS: In normal pooled plasma, GDXa-induced heparin reversal was mitigated by maintaining a high heparin concentration (12 U ml-1) and supplementing antithrombin (1.5-4.5 µM) based on peak and velocity of thrombin generation. Heparin reversal by GDXa was also demonstrated in cardiopulmonary bypass plasma, but supplementing both heparin (8 U ml-1) and antithrombin (3 µM) attenuated GDXa-induced changes in peak and velocity of thrombin generation by 72.5% and 72.2%, respectively. High heparin and antithrombin levels attenuated thrombin-antithrombin complex formation in tissue factor-activated, GDXa-spiked cardiopulmonary bypass plasma by 85.7%, but tissue factor pathway inhibitor remained depleted compared with control cardiopulmonary bypass plasma. CONCLUSIONS: Simultaneous supplementation of heparin and antithrombin mitigate GDXa-induced heparin resistance by compensating for the loss of tissue factor pathway inhibitor.

Comparative analysis of andexanet alfa and prothrombin complex concentrate in reversing anticoagulation by rivaroxaban ex vivo.

BACKGROUND: The comparative effectiveness of the specific antidote andexanet alfa vs the nonspecific therapy four-factor prothrombin complex concentrates (4F-PCCs) as reversal agents for direct factor Xa (FXa) inhibitors in severely bleeding patients is unclear. We hypothesised that specific reversal using andexanet alfa would be more effective than a high dose of PCC (50 IU kg-1) for reversing the FXa inhibitor rivaroxaban. METHODS: The reversal potential of andexanet alfa, various 4F-PCCs, and activated PCC was investigated ex vivo in human blood anticoagulated with rivaroxaban (37.5, 75, 150, and 300 ng ml-1) using a panel of coagulation parameters, including conventional coagulation assays, thrombin generation, and a newly developed viscoelastometric device. We simulated in vivo conditions of coagulation activation and fibrin formation using flow chamber experiments of thrombogenicity potential under arterial flow conditions. RESULTS: The 4F-PCCs normalised clotting profiles only at low rivaroxaban concentrations, whereas andexanet alfa and activated PCC significantly shortened clotting time at all rivaroxaban concentrations. Only andexanet alfa restored thrombin generation to baseline. Flow chamber results showed that various 4F-PCCs concentration-dependently restored clot formation. CONCLUSIONS: In contrast to thrombin generation measurements, haemostatic reversal of rivaroxaban using high-dose 4F-PCCs exhibited similar efficacy as andexanet alfa in flow chamber experiments. The haemostatic effects of 4F-PCCs and andexanet alfa in the context of bleeding patients taking FXa inhibitors requires further study.

Andexanet alfa or prothrombin complex concentrate for acute reversal of oral factor Xa inhibitors: monitoring of antidote effects.

This study in vitro comprehensively assessed reversal of the anticoagulant effects of rivaroxaban, an oral factor Xa inhibitor, using andexanet alfa and various prothrombin complex concentrate (PCC) products in a battery of tests. In static coagulation assays, andexanet alpha outperformed PCCs except for activated PCC being more effective in standard coagulation times. However, in a flow chamber model mimicking arterial shear, both andexanet alpha and high-concentration PCC restored fibrin formation, but not platelet adhesion. In the Russell's viper venom test and anti-Xa assay, only andexanet alpha could be tested for efficacy. The antidote effects of andexanet alpha and PCCs in restoring coagulation can be qualitatively or selectively demonstrated using in vitro coagulation tests.

Hepatocyte-secreted DPP4 in obesity promotes adipose inflammation and insulin resistance.

Obesity-induced metabolic disease involves functional integration among several organs via circulating factors, but little is known about crosstalk between liver and visceral adipose tissue (VAT). In obesity, VAT becomes populated with inflammatory adipose tissue macrophages (ATMs). In obese humans, there is a close correlation between adipose tissue inflammation and insulin resistance, and in obese mice, blocking systemic or ATM inflammation improves insulin sensitivity. However, processes that promote pathological adipose tissue inflammation in obesity are incompletely understood. Here we show that obesity in mice stimulates hepatocytes to synthesize and secrete dipeptidyl peptidase 4 (DPP4), which acts with plasma factor Xa to inflame ATMs. Silencing expression of DPP4 in hepatocytes suppresses inflammation of VAT and insulin resistance; however, a similar effect is not seen with the orally administered DPP4 inhibitor sitagliptin. Inflammation and insulin resistance are also suppressed by silencing expression of caveolin-1 or PAR2 in ATMs; these proteins mediate the actions of DPP4 and factor Xa, respectively. Thus, hepatocyte DPP4 promotes VAT inflammation and insulin resistance in obesity, and targeting this pathway may have metabolic benefits that are distinct from those observed with oral DPP4 inhibitors.

Characterization of an andexanet alfa administration protocol guided by drug-specific quantitative anti-Xa assays.

Following FDA approval in 2018, consensus guidelines recommend andexanet alfa as first-line therapy for the management of life-threatening or uncontrollable bleeding in patients taking oral factor Xa (FXa) inhibitors. Dosing is based on the specific FXa inhibitor and dose, and the time elapsed since the patient's last administration of the medication. Additionally, at our institution, anti-FXa screens and drug-specific assays are obtained to guide subsequent dosing based on institution protocol. The objective of this study was to evaluate andexanet alfa utilization based on anti-Xa and FXa-inhibitor-specific assays and assess associated outcomes. This was a retrospective, single-center study aimed to describe the use of anti-FXa and specific direct oral anticoagulant assays to guide the utilization and administration of andexanet alfa. Secondary endpoints evaluated included thrombotic events during index hospitalization, hospital length of stay, hospital mortality, and discharge disposition. Overall, most patients were prescribed apixaban for atrial fibrillation and received andexanet alfa for reversal of intracranial hemorrhage in the emergency department. In general, DOAC-specific assays were concordant with last known times; however, there appears to be minimal correlation with DOAC-specific assay levels and survival. There were 9 thrombotic events (8.7%) in 8 patients. In this cohort, collection of an anti-FXa assay screen was a practical strategy to guide reversal with andexanet alfa; however, the addition of DOAC-specific assay levels may not enhance clinical utility.

The 3-O-sulfation of heparan sulfate modulates protein binding and lyase degradation.

Humans express seven heparan sulfate (HS) 3-O-sulfotransferases that differ in substrate specificity and tissue expression. Although genetic studies have indicated that 3-O-sulfated HS modulates many biological processes, ligand requirements for proteins engaging with HS modified by 3-O-sulfate (3-OS) have been difficult to determine. In particular, the context in which the 3-OS group needs to be presented for binding is largely unknown. We describe herein a modular synthetic approach that can provide structurally diverse HS oligosaccharides with and without 3-OS. The methodology was employed to prepare 27 hexasaccharides that were printed as a glycan microarray to examine ligand requirements of a wide range of HS-binding proteins. The binding selectivity of antithrombin-III (AT-III) compared well with anti-Factor Xa activity supporting robustness of the array technology. Many of the other examined HS-binding proteins required an IdoA2S-GlcNS3S6S sequon for binding but exhibited variable dependence for the 2-OS and 6-OS moieties, and a GlcA or IdoA2S residue neighboring the central GlcNS3S. The HS oligosaccharides were also examined as inhibitors of cell entry by herpes simplex virus type 1, which, surprisingly, showed a lack of dependence of 3-OS, indicating that, instead of glycoprotein D (gD), they competitively bind to gB and gC. The compounds were also used to examine substrate specificities of heparin lyases, which are enzymes used for depolymerization of HS/heparin for sequence determination and production of therapeutic heparins. It was found that cleavage by lyase II is influenced by 3-OS, while digestion by lyase I is only affected by 2-OS. Lyase III exhibited sensitivity to both 3-OS and 2-OS.

Four-factor prothrombin complex concentrate versus andexanet alfa for direct oral anticoagulant reversal.

BACKGROUND: Optimal reversal agent for direct oral anticoagulant (DOAC)-associated major bleeding has not been described. Before the approval of andexanet alfa (AA) in 2018, 4-factor prothrombin complex concentrate (4F-PCC) was recommended by major guidelines. Currently, AA is recommended as the first-line agent by most guidelines. With a paucity of literature comparing the 2 agents, there is clinical value in assessing hemostatic efficacy and safety of the 2 agents. OBJECTIVE: This study aimed to evaluate hemostatic efficacy and safety of AA and 4F-PCC in all DOAC-associated major bleedings. METHODS: A multicenter, retrospective chart review was performed of adult subjects who were admitted for a DOAC-associated major bleeding and received 4F-PCC from February 2018 to May 2019 or AA from May 2019 to September 2021. Some of the exclusion criteria included not receiving a DOAC, receiving multiple reversal agents during the same hospitalization, receiving reversal for any nonmajor bleeding indication, and not receiving the full dose of a reversal agent. The primary outcome was hemostatic efficacy 24 hours after the end of the reversal agent administration. Secondary outcomes included time to administration, hospital mortality, length of stay, need for surgery, and need for additional blood product. Safety outcome was incidence of thrombotic events. RESULTS: There were 99 subjects included in the 4F-PCC group and 84 subjects in the AA group. Hemostatic efficacy was achieved in 69 subjects (69.7%) in the 4F-PCC group and 63 subjects (75%) in the AA group (P = 0.927). In-hospital mortality was seen in 20 subjects (20.2%) in the 4F-PCC group and 10 subjects (11.9%) in the AA group. Thrombotic events were seen in 7 subjects (7.1%) in the 4F-PCC group and 6 subjects (7.1%) in the AA group. CONCLUSIONS: There were no significant differences in hemostatic efficacy, in-hospital mortality, and number of thrombotic events between 4F-PCC and AA.

Four-factor prothrombin complex concentrate versus andexanet alfa for the reversal of traumatic brain injuries.

BACKGROUND: Andexanet alfa was approved in 2018 for reversal of direct oral anticoagulants but due to issues of cost and access, four-factor prothrombin complex concentrate (4F-PCC) continues to be used for this indication. The objective of this study is to evaluate outcomes of reversal with these agents in patients with isolated traumatic brain injuries (TBI). METHODS: This is a retrospective review of 35 trauma centres from 2014 to 2021. Patients were included with an Abbreviated Injury Scale (AIS)>2 for head and having received andexanet alfa or 4F-PCC within 24 hours of admission. Patients were excluded if P2Y12 inhibitor use or AIS>2 outside of head. Primary outcome includes rate of mortality/hospice at hospital discharge. Secondary outcomes include a composite of serious hospital complications. A subgroup analysis of severe TBI patients (AIS head 4 or 5) was completed. Multivariable logistic regression was used to account for differences in comorbidities and TBI severity. RESULTS: 4F-PCC was given to 265 patients with another 59 receiving andexanet alfa. Patients in the andexanet alfa group were more likely to have an AIS head score of 5 (47.5% vs 26.1%; p<0.005). After adjusting for severity of TBI and comorbidities with regard to tomortality/hospice, there were 15 (25.4%) patients in the andexanet alfa group and 49 (18.5%) in the 4F-PCC group (OR 1.34; 95% CI 0.67 to 2.71). This remained consistent when looking at severe patients with TBI with 12 (28.6%) andexanet alfa patients and 37 (28.7%) 4F-PCC patients (OR 0.93 (95% CI 0.40 to 2.16)). Severe hospital complications were also similar between groups with 5 (8.5%) andexanet alfa patients as compared with 21 (7.9%) 4F-PCC patients (OR 1.01; 95% CI 0.36 to 2.88). CONCLUSION: There was no firm conclusion on the treatment effect in mortality/hospice or serious complications among isolated TBI patients reversed with 4F-PCC as compared with andexanet alfa.

Design, Synthesis, and Evaluation of New Hybrid Derivatives of 5,6-Dihydro-4H-pyrrolo[3,2,1-ij]quinolin-2(1H)-one as Potential Dual Inhibitors of Blood Coagulation Factors Xa and XIa.

Cardiovascular diseases caused by blood coagulation system disorders are one of the leading causes of morbidity and mortality in the world. Research shows that blood clotting factors are involved in these thrombotic processes. Among them, factor Xa occupies a key position in the blood coagulation cascade. Another coagulation factor, XIa, is also a promising target because its inhibition can suppress thrombosis with a limited contribution to normal hemostasis. In this regard, the development of dual inhibitors as new generation anticoagulants is an urgent problem. Here we report the synthesis and evaluation of novel potential dual inhibitors of coagulation factors Xa and XIa. Based on the principles of molecular design, we selected a series of compounds that combine in their structure fragments of pyrrolo[3,2,1-ij]quinolin-2-one and thiazole, connected through a hydrazine linker. The production of new hybrid molecules was carried out using a two-stage method. The reaction of 5,6-dihydropyrrolo[3,2,1-ij]quinoline-1,2-diones with thiosemicarbazide gave the corresponding hydrazinocarbothioamides. The reaction of the latter with DMAD led to the target methyl 2-(4-oxo-2-(2-(2-oxo-5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-1(2H)-ylidene)hydrazineyl)thiazol-5(4H)-ylidene)acetates in high yields. In vitro testing of the synthesized molecules revealed that ten of them showed high inhibition values for both the coagulation factors Xa and XIa, and the IC50 value for some compounds was also assessed. The resulting structures were also tested for their ability to inhibit thrombin.