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.

Effects of Rheum rhaponticum and Rheum rhabarbarum extracts on haemostatic activity of blood plasma components and endothelial cells in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Traditional medicine recommends the use of Rheum rhaponticum L. and R. rhabarbarum L. to treat over thirty complaints, including disorders related to the cardiovascular system such as heartache, pains in the pericardium, epistaxis and other types of haemorrhage, blood purification as well as disorders of venous circulation. AIM OF THE STUDY: This work was dedicated to examining for the first time the effects of extracts from petioles and roots of R. rhaponticum and R. rhabarbarum, as well as two stilbene compounds (rhapontigenin and rhaponticin) on the haemostatic activity of endothelial cells and functionality of blood plasma components of the haemostatic system. MATERIALS AND METHODS: The study was based on three main experimental modules, including the activity of proteins of the human blood plasma coagulation cascade and the fibrinolytic system as well as analyses of the haemostatic activity of human vascular endothelial cells. Additionally, interactions of the main components of the rhubarb extracts with crucial serine proteases of the coagulation cascade and fibrinolysis (i.e. thrombin, the coagulation factor Xa and plasmin) were analyzed in silico. RESULTS: The examined extracts displayed anticoagulant properties and significantly reduced the tissue factor-induced clotting of human blood plasma (by about 40%). Inhibitory effects of the tested extracts on thrombin and the coagulation factor Xa (FXa) were found as well. For the extracts, the IC50 was ranging from 20.26 to 48.11 µg/ml. Modulatory effects on the haemostatic response of endothelial cells, including the release of von Willebrand factor, tissue-type plasminogen activator and the plasminogen activator inhibitor-1, have been also found. CONCLUSIONS: Our results indicated for the first time that the examined Rheum extracts influenced the haemostatic properties of blood plasma proteins and endothelial cells, with the prevalence of the anticoagulant action. The anticoagulant effect of the investigated extracts may be partly attributed to the inhibition of the FXa and thrombin activities, the key serine proteases of the blood coagulation cascade.

Comparison of Managing Factor Xa Inhibitor to Unfractionated Heparin Transitions by aPTT Versus a Treatment Guideline Utilizing Heparin Anti-Xa Levels.

BACKGROUND: There are inadequate data on the optimal strategy for transitioning factor Xa inhibitors (FXai; apixaban, rivaroxaban) to unfractionated heparin (UFH) infusions. OBJECTIVE: In patients transitioning from an FXai to an UFH infusion, this study compared the safety and efficacy of monitoring UFH infusions using an activated partial thromboplastin time (aPTT) titration scale versus utilizing an UFH-calibrated anti-Xa titration scale aided by a novel institutional guideline. METHODS: A retrospective cohort analysis was conducted on adult patients transitioning from an FXai to an UFH infusion at 2 medical centers from June 1, 2018, to November 1, 2020. One institution utilized aPTT while the other institution primarily used UFH-calibrated anti-Xa. The primary endpoint was a composite of death, major bleeding, or new thrombosis during the hospitalization with a planned noninferiority analysis. Secondary outcomes were also collected including the amount and duration of UFH administered between cohorts. RESULTS: The incidence rate of the primary composite endpoint was 6.3% in the anti-Xa group and 11% in the aPTT group (P < 0.001 for noninferiority, P = 0.138 for superiority) meeting noninferiority criteria. No statistical differences were seen in new thrombosis, major bleeding, or any bleeding. CONCLUSION AND RELEVANCE: This represents the first report of a comparison between aPTT versus anti-Xa monitoring in relation to clinical outcomes for patients transitioning from an FXai to an UFH infusion. A transition guideline primarily utilizing an UFH-calibrated anti-Xa assay appears to be a safe alternative to aPTT monitoring and can aid facilities in the management of patients during these complex transitions.

Activated Factor X Signaling Pathway via Protease-Activated Receptor 2 Is a Novel Therapeutic Target for Preventing Atrial Fibrillation.

BACKGROUND: Activated factor X (FXa), which contributes to chronic inflammation via protease-activated receptor 2 (PAR2), might play an important role in atrial fibrillation (AF) arrhythmogenesis. This study aimed to assess whether PAR2 signaling contributes to AF arrhythmogenesis and whether rivaroxaban ameliorates atrial inflammation and prevents AF.Methods and Results:In Study 1, PAR2 deficient (PAR2-/-) and wild-type mice were infused with angiotensin II (Ang II) or a vehicle via an osmotic minipump for 2 weeks. In Study 2, spontaneously hypertensive rats (SHRs) were treated with rivaroxaban, warfarin, or vehicle for 2 weeks after 8 h of right atrial rapid pacing. The AF inducibility and atrial remodeling in both studies were examined. Ang II-treated PAR2-/- mice had a lower incidence of AF and less mRNA expression of collagen1 and collagen3 in the atrium compared to wild-type mice treated with Ang II. Rivaroxaban significantly reduced AF inducibility compared with warfarin or vehicle. In SHRs treated with a vehicle, rapid atrial pacing promoted gene expression of inflammatory and fibrosis-related biomarkers in the atrium. Rivaroxaban, but not warfarin, significantly reduced expression levels of these genes. CONCLUSIONS: The FXa-PAR2 signaling pathway might contribute to AF arrhythmogenesis associated with atrial inflammation. A direct FXa inhibitor, rivaroxaban, could prevent atrial inflammation and reduce AF inducibility, probably by inhibiting the pro-inflammatory activation.

Emergent reversal of oral factor Xa inhibitors with four-factor prothrombin complex concentrate.

BACKGROUND: Controversy exists regarding first-line use of the recently approved reversal agent andexanet alfa due to limitations of the ANEXXA-4 study, thrombotic risks, and high medication acquisition cost. The purpose of this study was to evaluate the safety and effectiveness of 4F-PCC for the reversal of emergent oral fXa inhibitor-related bleeding. Furthermore, we aimed to evaluate a subgroup using strict ANNEXA-4 patient selection criteria. METHODS: This was a retrospective study conducted utilizing chart review of adult patients that received 4F-PCC for oral fXa inhibitor-related bleeding. The primary endpoint was the rate of clinical success defined as achieving excellent or good hemostatic effectiveness following the administration of 4F-PCC. Secondary endpoints included in-hospital mortality and arterial/venous thromboembolism, and cost compared with andexanet alfa. RESULTS: A total of 119 patients were included, with 83 patients in the ANNEXA-4 criteria subgroup. Eighty-five of the 119 patients (71%) required reversal due to intracranial bleeding. Prior to reversal, 70 patients (59%) were taking apixaban and 49 patients (41%) were taking rivaroxaban. Clinical success was achieved in 106 of 119 patients (89%) and 74 of 83 patients (90%) in the strict criteria subgroup. Three of 119 patients (2.5%) had a thrombotic event during hospital stay and the overall mortality rate was 13%. The average cost increase of andexanet alfa compared to 4F-PCC would have been $29,500 per patient. CONCLUSIONS: Administration of 4F-PCC for the reversal of oral fXa inhibitors was effective with relatively low thrombotic risk. Further direct prospective comparison of 4F-PCC to andexanet alfa is warranted.

Low Risk of Traumatic Intracranial Hematoma Expansion with Factor Xa Inhibitors without Andexanet Reversal.

BACKGROUND: Andexanet alfa, a novel anticoagulation reversal agent for factor Xa inhibitors, was recently approved. Traumatic intracranial hemorrhage presents a prime target for this drug. The Novel Antidote to the Anticoagulation Effects of Factor Xa Inhibitors study established the efficacy of andexanet alfa in reversing factor Xa inhibitors. However, the association between anticoagulation reversal and traumatic intracranial hemorrhage progression is not well understood. The objective of this study was to determine progression rates of patients with traumatic intracranial hemorrhage on factor Xa inhibitors prior to hospitalization who were managed without the use of andexanet alfa. METHODS: A retrospective cohort study was performed between 2016 and 2019 at a single institution. An institutional traumatic brain injury (TBI) registry was queried. Patients with recorded use of apixaban or rivaroxaban <18 hours before injury were included. The primary study outcome was <35% increase in hemorrhage volume or thickness on repeated head computed tomography (CT) scans. RESULTS: We identified 25 patients meeting the inclusion criteria. Two patients were excluded because of a lack of necessary CT data. Twelve patients (52%) were receiving apixaban, and 11 were (48%) on rivaroxaban. On admission CT scan, 14 patients had subdural hematoma, 6 had traumatic intraparenchymal hemorrhage, and 3 had subarachnoid hemorrhage. Anticoagulation reversal was attempted in 17 patients (74%), primarily using 4-factor prothrombin complex concentrate. Twenty patients (87%) were adjudicated as having excellent or good hemostasis on repeat imaging. CONCLUSIONS: Our results indicate that patients on factor Xa inhibitors with complicated mild TBI have a similar intracranial hemorrhage progression rate to patients who are not anticoagulated or anticoagulated with a reversible agent. The hemostatic outcomes in our cohort were similar to those reported after andexanet alfa administration.

Management of epistaxis in patients on novel oral anticoagulation therapy.

BACKGROUND: Individuals on anticoagulation therapy are at increased risk of bleeding, including epistaxis. There is a lack of available reversal agents for novel oral anticoagulation therapy. OBJECTIVE: This paper reviews the current literature on epistaxis in the context of novel oral anticoagulation use, in order to recommend guidelines on management. METHOD: A comprehensive search of published literature was conducted to identify all relevant articles published up to April 2019. RESULTS: Patients on oral anticoagulation therapy are over-represented in individuals with epistaxis. Those on novel oral anticoagulation therapy were more likely to relapse compared to patients on classic oral anticoagulants or non-anticoagulated patients. Idarucizumab is an effective antidote for bleeding associated with dabigatran use. Recommendations for epistaxis management in patients on novel oral anticoagulation therapy are outlined. CONCLUSION: Clinicians need to be aware of the potential severity of epistaxis and the increased likelihood of recurrence. High-quality studies are required to determine the efficacy and safety of andexanet alfa and ciraparantag, as well as non-specific reversal agents.

An online dual-enzyme co-immobilized microreactor based on capillary electrophoresis for enzyme kinetics assays and screening of dual-target inhibitors against thrombin and factor Xa.

In this study, an online capillary electrophoresis (CE) based dual-enzyme (thrombin and factor Xa) co-immobilized microreactor (THR-FXa IMER) was constructed for studying enzyme kinetics and screening dual-target inhibitors against THR and FXa with the aid of the polydopamine/graphene oxide (PDA/GO) coating. Based on the developed THR-FXa IMER, the Michaelis-Menten constants (Km) of THR and FXa were calculated to be 187.26 and 48.80 µM, respectively. The inhibition constants (Ki) for two known inhibitors, argatroban and rivaroxaban, on THR and FXa were determined to be 14.73 and 0.41 nM, respectively. In addition, after 30 consecutive runs, the enzymes' activity was remained 98% of the initial immobilized activity for both THR and FXa, which shows that the constructed IMER has good stability and repeatability. Finally, the developed method was successfully applied to screen dual-target inhibitors against THR and FXa from 30 small molecular compounds. Among them, 10 compounds such as salvianolic acid C and epigallocatechin gallate (EGCG) have dual-enzyme inhibitory activity, and 2 compounds named saikosaponin A and oleuropein have single THR inhibitory activity, 5 compounds such as rosemary acid and salvianolic acid B have single FXa inhibitory activity. Finally, the molecular interactions between enzyme and potential inhibitors were further verified via the molecular docking, and a new compound with a theoretically good coagulation inhibition effect was designed by the scaffold hopping study. In summary, the developed THR-FXa IMER is a reliable method for screening THR and/or FXa inhibitors.

Current Strategies for the Management of Bleeding Associated with Direct Oral Anticoagulants and a Review of Investigational Reversal Agents.

BACKGROUND: The management of life-threatening bleeding in patients who are receiving direct oral anticoagulants (DOACs) is a serious medical concern. OBJECTIVE: This review provides a concise, balanced overview of the current and future approaches for reversing the anticoagulation effects of DOACs, particularly factor Xa (FXa) inhibitors. DISCUSSION: The anticoagulant activity of the direct thrombin inhibitor dabigatran can be reversed by idarucizumab, but until recently, options for the management of major bleeding in patients who were receiving FXa inhibitors were limited to nonspecific strategies, including supplementation of clotting factors with prothrombin complex concentrates (PCCs) or activated PCCs for attenuating anticoagulation effects. They appear as a treatment option in many hospital guidelines despite the lack of approval by the U.S. Food and Drug Administration and the lack of rigorous medical evidence supporting their use in this setting. The development of specific reversal agents may provide improved strategies for the management of bleeding. Andexanet alfa is a modified FXa molecule approved in the United States to reverse the anticoagulant effects of FXa inhibitors (rivaroxaban and apixaban) in patients with life-threatening or uncontrolled bleeding. Ciraparantag is a small-molecule inhibitor of multiple anticoagulants that has been investigated in healthy subjects. CONCLUSION: The current guidelines for management of DOAC-associated bleeding are being updated to reflect that the reversal agent for rivaroxaban and apixaban is now available. For other FXa inhibitors, in the absence of a reversal agent, nonspecific strategies that include PCCs are recommended. The population of patients anticoagulated with DOACs is growing, and we hope that specific reversal agents will improve the approach to management of major bleeding in this population.

Real-world utilization of andexanet alfa.

OBJECTIVE: In 2018, the FDA approved andexanet alfa for the reversal of life-threatening hemorrhages in patients anticoagulated with apixaban or rivaroxaban. Yet, cost-effective factor Xa inhibitor reversal remains controversial. The objective of this study was to describe real world utilization of andexanet alfa. METHODS: This was a retrospective case series of patients receiving andexanet alfa between July 28, 2018 and April 29, 2019 at a large academic health system. Baseline demographics, anticoagulant type and reversal, as well as brain imaging were collected. Primary endpoints were stability of hematoma for intracranial hemorrhage (ICH), and hemostatic effectiveness for patients undergoing surgical procedures. Secondary endpoints were thromboembolism and 30 day mortality. RESULTS: Of the 25 patients evaluated, 13 received andexanet alfa for ICH. Eleven of the 13 had follow-up imaging available and stability was observed in 90.9%. Three patients received andexanet alfa for reversal prior to surgical procedures, and 100% hemostatic effectiveness was achieved. Nine patients received andexanet alfa for reversal of extracranial bleeding, including gastrointestinal bleed (n=4). There were no thrombotic events in our cohort, and 30 day mortality was 24%. Sixty-four percent of patients would have met exclusion criteria for the ANNEXA-4 trial. CONCLUSION: This is the largest series to date describing real-world utilization of andexanet alfa. Our series showed hemostatic efficacy in 90.9% of patients with ICH, and 100% in patients undergoing surgical procedures. There were no thrombotic complications. Yet, larger and comparative studies are needed to clarify the optimal agent and patient selection for reversal of factor Xa inhibitors.

A Systematic and Evidence-Based Review of Published and Pending Reports of Andexanet Alfa.

Andexanet alfa is the newly approved factor Xa inhibitor reversal agent for the treatment of life-threatening or uncontrolled bleeding from apixaban or rivaroxaban. This decoy protein directly binds factor Xa inhibitors reversing their action. A systematic and evidence-based evaluation of the available clinical trials is lacking in the literature. This research will provide a systematic and evidence-based evaluation of published clinical trials for andexanet alfa. It will also present an evaluation of active research. Reports of research were identified through multiple databases using search terms andexanet alfa, andexanet, or PRT064445. The level of evidence and strength of recommendation were accomplished using the Strength of Recommendation Taxonomy. There are 2 published articles presenting 3 clinical trials. Two trials had a low level of evidence and the third trial, a preliminary report of results, showed a moderate level of evidence. The review of active research found 3 unique studies and a preliminary results study. The level of evidence is low for 2 of these studies, moderate for a third, and potentially high for the fourth. The strength of recommendation for all 6 studies is a C. Four of the studies present disease-oriented evidence resulting in a low level of evidence. Another study is unblinded and uncontrolled but presents patient-oriented evidence resulting in a moderate level of evidence. Only one study could score high because the outcome is patient-oriented evidence, and it could achieve follow-up of 80%. There is a need for well-controlled and blinded evaluation to improve the recommendation strength.

Direct Rivaroxaban-Induced Factor XA Inhibition Proves to be Cardioprotective in Rats.

BACKGROUND: Acute myocardial infarction is a leading cause of death worldwide. Though highly beneficial, reperfusion of myocardium is associated with reperfusion injury. While indirect inhibition of Factor Xa has been shown to attenuate myocardial ischemia-reperfusion (I/R) injury, the underlying mechanism remains unclear. Our study sought to evaluate the effect of rivaroxaban (RIV), a direct inhibitor of Factor Xa, on myocardial I/R injury and determine its cellular targets. EXPERIMENTAL APPROACH: We used a rat model of 40-min coronary ligation followed by reperfusion. RIV (3 mg/kg) was given per os 1 h before reperfusion. Infarct size and myocardial proteic expression of survival pathways were assessed at 120 and 30 min of reperfusion, respectively. Plasmatic levels of P-selectin and von Willebrand factor were measured at 60 min of reperfusion. Cellular RIV effects were assessed using hypoxia-reoxygenation (H/R) models on human umbilical vein endothelial cells and on rat cardiomyoblasts (H9c2 cell line). KEY RESULTS: RIV decreased infarct size by 21% (42.9% vs. 54.2% in RIV-treated rats and controls respectively, P < 0.05) at blood concentrations similar to human therapeutic (387.7 ±â€Š152.3 ng/mL) levels. RIV had no effect on H/R-induced modulation of endothelial phenotype, nor did it alter myocardial activation of reperfusion injury salvage kinase and survivor activating factor enhancement pathways at 30 min after reperfusion. However, RIV exerted a cytoprotective effect on H9c2 cells submitted to H/R. CONCLUSIONS: RIV decreased myocardial I/R injury in rats at concentrations similar to human therapeutic ones. This protection was not associated with endothelial phenotype modulation but rather with potential direct cytoprotection on cardiomyocytes.

Antidotes for reversal of direct oral anticoagulants.

The main advantage of the direct oral anticoagulants over vitamin K antagonists is reduced rates of major bleeding, especially intracranial hemorrhage. While use of different clotting factor supplements have been used in patients with direct oral anticoagulant induced major bleeding or when there is need for urgent surgery, the lack of preclinical and clinical data are concerning. Idarucizumab is a specific antibody developed with a 350-fold greater affinity for dabigatran than its pharmacologic target thrombin. Andexanet is a modified factor Xa molecule that binds the direct and indirect Xa inhibitors without being enzymatically active. Ciraparantag, has potential to reverse the anticoagulant activity of multiple agents. The pharmacology, preclinical, and clinical data that have developed these specific antidotes are reviewed in this manuscript.

Bodyweight-adjusted rivaroxaban for children with venous thromboembolism (EINSTEIN-Jr): results from three multicentre, single-arm, phase 2 studies.

BACKGROUND: Rivaroxaban has been shown to be efficacious for treatment of venous thromboembolism in adults, and has a reduced risk of bleeding compared with standard anticoagulants. We aimed to develop paediatric rivaroxaban regimens for the treatment of venous thromboembolism in children and adolescents. METHODS: In this phase 2 programme, we did three studies to evaluate rivaroxaban treatment in children younger than 6 months, aged 6 months to 5 years, and aged 6-17 years. Our studies used a multicentre, single-arm design at 54 sites in Australia, Europe, Israel, Japan, and north America. We included children with objectively confirmed venous thromboembolism previously treated with low-molecular weight heparin, fondaparinux, or a vitamin K antagonist for at least 2 months or, in children who had catheter-related venous thromboembolism for at least 6 weeks. We administered rivaroxaban orally in a bodyweight-adjusted 20 mg-equivalent dose, based on physiologically-based pharmacokinetic modelling predictions and EINSTEIN-Jr phase 1 data in young adults, in either a once-daily (tablets; for those aged 6-17 years), twice-daily (in suspension; for those aged 6 months to 11 years), or three times-daily (in suspension; for those younger than 6 months) dosing regimen for 30 days (or 7 days for those younger than 6 months). The primary aim was to define rivaroxaban treatment regimens that match the target adult exposure range. The principal safety outcome was major bleeding and clinically relevant non-major bleeding. Analyses were per-protocol. The predefined efficacy outcomes were symptomatic recurrent venous thromboembolism, asymptomatic deterioration on repeat imaging at the end of the study treatment period. These trials are registered at ClinicalTrials.gov, numbers NCT02564718, NCT02309411, and NCT02234843. FINDINGS: Between Feb 11, 2013, and Dec 20, 2017, we enrolled 93 children (ten children younger than 6 months; 15 children aged 6 months to 1 year; 25 children aged 2-5 years; 32 children aged 6-11 years; and 11 children aged 12-17 years) into our study. 89 (96%) children completed study treatment (30 days of treatment, or 7 days in those younger than 6 months), and 93 (100%) children received at least one dose of study treatment and were evaluable for the primary endpoints. None of the children had a major bleed, and four (4%, 95% CI 1·2-10·6) of these children had a clinically relevant non-major bleed (three children aged 12-17 years with menorrhagia and one child aged 6-11 years with gingival bleeding). We found no symptomatic recurrent venous thromboembolism in any patients (0%, 0·0-3·9). 24 (32%) of 75 patients with repeat imaging had their thrombotic burden resolved, 43 (57%) patients improved, and eight (11%) patients were unchanged. No patient deteriorated. We confirmed therapeutic rivaroxaban exposures with once-daily dosing in children with bodyweights of at least 30 kg and with twice-daily dosing in children with bodyweights of at least 20 kg and less than 30 kg. Children with low bodyweights (<20 kg, particularly <12 kg) showed low exposures so, for future studies, rivaroxaban dosages were revised for these weight categories, to match the target adult exposure range. 61 (66%) of 93 children had adverse events during the study. Pyrexia was the most common adverse event (ten [11%] events), and anaemia and neutropenia or febrile neutropenia were the most frequent grade 3 or worse events (four [4%] events each). No children died or were discontinued from rivaroxaban because of adverse events. INTERPRETATION: Treatment with bodyweight-adjusted rivaroxaban appears to be safe in children. The treatment regimens that we confirmed in children with bodyweights of at least 20 kg and the revised treatment regimens that we predicted in those with bodyweights less than 20 kg will be evaluated in the EINSTEIN-Jr phase 3 trial in children with acute venous thromboembolism. FUNDING: Bayer AG, Janssen Research and Development.

Characterization of active anticoagulant fraction and a fibrin(ogen)olytic serine protease from leaves of Clerodendrum colebrookianum, a traditional ethno-medicinal plant used to reduce hypertension.

ETHNOPHARMACOLOGICAL RELEVANCE: Cardiovascular diseases are the major cause of mortality and morbidity, causing over 17.9 million deaths a year worldwide. Currently used therapy is often having side effects and expensive, dietary interventions and alternative medicines are required. Clerodendrum colebrookianum has been used to treat cardiac hypertension but anticoagulant potency was not evaluated. AIM OF THE STUDY: To characterize an active anticoagulant fraction (AAFCC) and a 30 kDa fibrin(ogen)olytic serine protease (clerofibrase) isolated from aqueous leave extract of C. colebrookianum. MATERIALS AND METHODS: AAFCC/clerofibrase was subjected to extensive biochemical and pharmacological characterization including LC-MS/MS, amino acid compositional and GC-MS analyses. Interaction between clerofibrase with fibrinogen was studied by spectrofluorometric analysis. In vitro thrombolytic, antiplatelet and cytotoxicity assay were performed. In vivo toxicity, anticoagulant, defibrinogen and antithrombotic activities were determined on Swiss albino mice. RESULTS: The in vitro anticoagulant activity of AAFCC was found to be superior to heparin and clerofibrase and comparable to Nattokinase and warfarin. The proteomics and amino acid composition analyses suggest that clerofibrase is a previously uncharacterized novel plant protease capable of degrading the -αß chains of fibrinogen/fibrin. AAFCC/clerofibrase exerts their anticoagulant action via fibrinogenolytic activity and partially by antiplatelet activity albeit they have no effect on thrombin and FXa inhibition. The spectrofluorometric analysis revealed the binding of clerofibrase to fibrinogen but not to thrombin and FXa. The phytochemical constituents and bioactive components of AAFCC were characterized by biochemical, and GC-MS analyses. The AAFCC and clerofibrase inhibited collagen/ADP-induced mammalian platelet aggregation, showed in vitro thrombolytic activity, and non-cytotoxic to mammalian cells. The AAFCC showed and dose-dependent in vivo plasma defibrinogenating and anticoagulant activities and inhibited k-carrageen-induced thrombus formation in the tails of mice. CONCLUSION: The potent in vivo anticoagulant and antithrombotic effects of AAFCC suggests its pharmacological significance as herbal anticoagulant drug for the prevention and/or treatment of hyperfibrinogenemia- and thrombosis associated cardiovascular disorders.

Induction and Impact of Anti-Drug Responses Elicited by a Human Recombinant Coagulation Factor FXaI16L in Preclinical Species.

This paper presents a systemic investigation of ADA development and ADA impact of a human coagulation factor in nonclinical species during drug development and provides insights into potential implications in human if a similar ADA occurs. FXaI16L-induced ADA response was characterized in monkey, mouse, rat, and dog in different studies, and ADA effects on pharmacokinetic and/or pharmacodynamics of FXaI16L were further examined in ADA-negative and ADA-positive animals. After repeated administrations, FXaI16L elicited a dose and exposure day-dependent ADA response which ranged from no response to a transient or persistent response. Increase in exposure day and increase in dose generally enhanced ADA incidence except for a decrease in ADA incidence was observed in monkeys after repeated high-dose administrations. The observable ADA impact on pharmacokinetics was only found in some ADA+ animals and included decrease in clearance and increase in systemic exposure but no increase in half-life. In addition, no or limited effect on pharmacodynamics by ADA was observed. The earliest ADA response was observed after three exposure days, marked elevation of drug exposure was observed in some animals at log titer > 2.0, and the highest antibody titer excited was about 4 (Log10) in all species. A correlation between ADA induction and accumulative exposure after various repeat treatments in different species was found for FXaI16L. In addition, potential immunogenicity risk and mitigation of ADA in clinics are discussed.

The Non-Vitamin K Antagonist Oral Anticoagulants in Heart Disease: Section V-Special Situations.

Non-vitamin K antagonist oral anticoagulants (NOACs) include dabigatran, which inhibits thrombin, and apixaban, betrixaban, edoxaban and rivaroxaban, which inhibit factor Xa. In large clinical trials comparing the NOACs with the vitamin K antagonist (VKA) warfarin, dabigatran, apixaban, rivaroxaban and edoxaban were at least as effective for stroke prevention in atrial fibrillation and for treatment of venous thromboembolism, but were associated with less intracranial bleeding. In addition, the NOACs are more convenient to administer than VKAs because they can be given in fixed doses without routine coagulation monitoring. Consequently, the NOACs are now replacing VKAs for these indications, and their use is increasing. Although, as a class, the NOACs have a favourable benefit-risk profile compared with VKAs, choosing among them is complicated because they have not been compared in head-to-head trials. Therefore, selection depends on the results of the individual trials, renal function, the potential for drug-drug interactions and preference for once- or twice-daily dosing. In addition, several 'special situations' were not adequately studied in the dedicated clinical trials. For these situations, knowledge of the unique pharmacological features of the various NOACs and judicious cross-trial comparison can help inform prescription choices. The purpose of this position article is therefore to help clinicians choose the right anticoagulant for the right patient at the right dose by reviewing a variety of special situations not widely studied in clinical trials.