Factor Xa Research Articles

Synthesis and anticoagulant activity of methyl 2-{2-[2-(4,4,6-trimethyl-2-oxo-4H-pyrrolo[3,2,1-ij]quinolin-1(2H)-ylidene)hydrazineyl]-4-oxothiazol-5(4H)-ylidene}acetates against blood clotting factors Xa, XIa and thrombin

Synthesis and anticoagulant activity of methyl 2-{2-[2-(4,4,6-trimethyl-2-oxo-4H-pyrrolo[3,2,1-ij]quinolin-1(2H)-ylidene)hydrazineyl]-4-oxothiazol-5(4H)-ylidene}acetates against blood clotting factors Xa, XIa and thrombin

In factor Xa inhibitor-related acute ICH, andexanet vs. usual care improved hemostatic efficacy but increased thrombotic events.

Connolly SJ, Sharma M, Cohen AT, et al; ANNEXA-I Investigators. Andexanet for factor Xa inhibitor-associated acute intracerebral hemorrhage. N Engl J Med. 2024;390:1745-1755. 38749032.

Prothrombin complex concentrate for direct factor Xa inhibitor-associated bleeding or before urgent surgery

IntroductionFactor Xa inhibitor (FXaI)-associated bleeding events are common and associated with substantial morbidity. Systematic evaluation of widely available, effective, and affordable FXaI bleed management strategies is needed. Materials and methodsWe conducted a single-center retrospective cohort study of FXaI-treated patients presenting to a tertiary academic medical center from January 2018 to May 2019 who received 25–50 IU/kg 4F-PCC for either FXaI-associated major bleeding or urgent surgery. The primary outcome was hemostatic efficacy, and the safety outcome was the 30-day risk of thromboembolism. ResultsPCC was used to treat FXaI-associated bleeding in 83 cases (79.1 %) and was given before urgent surgery in 22 cases (20.9 %). Sixty-six patients were on apixaban, 38 were on rivaroxaban and one patient was on edoxaban. Intracranial hemorrhage (ICH) and gastrointestinal bleeding accounted for most bleeds (74.7 %). Median interval between last DOAC intake and presentation to triage was 9 h [IQR 5.3–14.8] and median PCC dosing was 40.0 IU/kg [IQR 28.5–46.6]. Forty-two patients (40.0 %) had pre-PCC FXaI levels drawn with median FXaI levels of 114.5 ng/mL [IQR 70.0–175.0]. Effective hemostasis occurred in 66.7 % [95%CI 55.4–76.3] of patients receiving PCC for bleeding and surgical hemostasis was rated as normal in 95.5 % (95%CI 76.5–100.0) for patients having urgent surgery. The 30-day risk of thromboembolism was 7.6 % [95%CI 3.7–14.5] and 22.9 % [95%CI 15.8–31.8] of patients died. ConclusionsPCC for FXaI-associated bleeding was associated with hemostatic efficacy in two-thirds of patients and thromboembolic events were uncommon. PCC represents a promising treatment strategy for FXaI-associated bleeding.

Incident thrombocytopenia and bleeding risk in elderly patients with atrial fibrillation on direct oral anticoagulants: insights from the ATHEROsclerosis in Atrial Fibrillation study

BackgroundThe bleeding risk of patients with atrial fibrillation (AF) changes over time. Most studies thus far evaluated only the baseline bleeding risk with discordant results. The impact of incident thrombocytopenia during direct oral anticoagulant (DOAC) therapy and its relation to bleeding has not been previously investigated. ObjectivesTo investigate the incidence rate of thrombocytopenia and major bleeding (MB) risk in AF patients on DOACs. MethodsProspective ongoing ATHEROsclerosis in Atrial Fibrillation study including patients with nonvalvular AF on DOACs. Incident thrombocytopenia was defined as a platelet count <150 × 109/L. MB events were recorded at each follow-up visit. Gray estimator for competing risk data was used. Estimates are expressed in terms of subdistributional hazard ratios (sHR) and relative 95% CI for MB. ResultsWe enrolled 957 AF patients treated with DOACs (mean age, 77.3 ± 9.0 years; 49.1% women). During a follow-up (median time to censoring 1330 days; 95% CI, 1246-1443), 139 patients developed thrombocytopenia (3.08 per 100 person-years; 95% CI, 2.27-3.89) with no difference between direct thrombin and factor Xa inhibitors. Overall, 179 bleedings occurred, of which 80 were major (3.17 per 100 person-years; 95% CI, 2.34-3.99). Patients sustaining bleedings were more frequently affected by arterial hypertension, heart failure, anemia and had higher CHA2DS2-VASc and HAS-BLED scores. On multivariable Cox analysis, independent risk factors for MB were incident thrombocytopenia (sHR, 12.77; 95% CI, 8.880-18.360; P < .001), and age (sHR, 1.030 per year; 95% CI, 1.010-1.040; P = .002). ConclusionPatients developing thrombocytopenia have an increased risk of MB. Dynamic evaluation of platelet count during follow-up may provide better prognostic value than baseline assessment only.

Clinical, Laboratory Aspects and Management of Factor X Deficiency.

Coagulation factor X (FX), originally named Stuart-Prower factor, plays a pivotal role in the coagulation cascade, activating thrombin to promote platelet plug formation and prevent excess blood loss. Genetic variants in F10 may lead to FX deficiency and to impaired coagulation. FX variants are phenotypically classified as being type I, with the concomitant reduction of FX coagulant activity and FX antigen levels or type II, corresponding to a reduction in activity with normal antigen plasma levels. Patients affected with FX deficiency tend to be one of the most seriously affected among those with rare bleeding disorders. They show a variable bleeding tendency strongly associated with FX coagulant activity levels in plasma and may present, in the severe form of the deficiency, life-threatening symptoms such as gastrointestinal and umbilical stump bleeding and intracranial hemorrhages or central nervous system bleeding. Treatment of FX deficiency was originally based on the replacement of the missing factor using fresh frozen plasma, cryoprecipitate and prothrombin complex concentrates; however, a plasma-derived concentrate, shown to be safe and effective in clinical trials, is now available. In addition, novel nonreplacement therapy such as small interference RNA, gene therapy, drug repurposing, and gene editing may also represent novel therapeutic approaches for FX deficiency, but further, much focused studies are needed before considering this emerging therapy in such patients.

Milvexian vs apixaban for stroke prevention in atrial fibrillation: The LIBREXIA atrial fibrillation trial rationale and design

Direct oral anticoagulants are the standard of care for stroke prevention in eligible patients with atrial fibrillation and atrial flutter; however, bleeding remains a significant concern, limiting their use. Milvexian is an oral Factor XIa inhibitor that may offer similar anticoagulant efficacy with less bleeding risk. LIBREXIA AF (NCT05757869) is a global phase III, randomized, double-blind, parallel-group, event-driven trial to compare milvexian with apixaban in participants with atrial fibrillation or atrial flutter. Participants are randomly assigned to milvexian 100 mg or apixaban (5 mg or 2.5 mg per label indication) twice daily. The primary efficacy objective is to evaluate if milvexian is noninferior to apixaban for the prevention of stroke and systemic embolism. The principal safety objective is to evaluate if milvexian is superior to apixaban in reducing the endpoint of International Society of Thrombosis and Hemostasis (ISTH) major bleeding events and the composite endpoint of ISTH major and clinically relevant nonmajor (CRNM) bleeding events. In total, 15,500 participants from approximately 1,000 sites in over 30 countries are planned to be enrolled. They will be followed until both 430 primary efficacy outcome events and 530 principal safety events are observed, which is estimated to take approximately 4 years. The LIBREXIA AF study will determine the efficacy and safety of the oral Factor XIa inhibitor milvexian compared with apixaban in participants with either atrial fibrillation or atrial flutter. ClinicalTrials.gov NCT05757869.

The first-in-human study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of the factor XI monoclonal antibody SHR-2004 in healthy subjects

ABSTRACT Background Inhibiting the coagulation factor XI (FXI) is a novel strategy for prevention and treatment of thromboembolism without affecting extrinsic coagulation pathways. SHR-2004 is a humanized monoclonal antibody that selectively binds to FXI and factor XIa (FXIa). Research design & methods This randomized, double-blind, dose-escalation, placebo-controlled study evaluated SHR-2004 administered either intravenously (i.v.; Part A) or subcutaneously (s.c.; Part B). In Part A, 24 subjects received a single i.v. dose of SHR-2004 (0.1, 0.3, or 1.0 mg/kg) or placebo. In Part B, 40 subjects received a single s.c. dose of SHR-2004 (0.5, 1.0, 3.0, or 4.5 mg/kg) or placebo. Results SHR-2004 was well tolerated. Plasma exposure to SHR-2004 increased in a dose-dependent manner. The geometric mean half-time ranged from 11.6 to 13.0 days. FXI activity decreased, and the activated partial thromboplastin time (APTT) was prolonged after i.v. and s.c. administration in a dose- and time-dependent manner. FXI activity was nearly completely abolished immediately after administering the highest i.v. dose, with the average APTT prolonged to nearly three times of baseline. Conclusion SHR-2004 is a promising candidate for further development as an anticoagulant drug that exerts effective anticoagulation with minimal risk of bleeding. Clinical trial registration www.clinicaltrials.gov identifier is NCT05369767.

Proteogenomics-guided functional venomics resolves the toxin arsenal and activity of Deinagkistrodon acutus venom

Snakebite primarily impacts rural communities of Africa, Asia, and Latin America. The sharp-nosed viper (Deinagkistrodon acutus) is among the snakes of highest medical importance in Asia. Despite various studies on its venom using modern venomics techniques, a comprehensive understanding of composition and function of this species' venom remains lacking. We combined proteogenomics with extensive bioactivity profiling to present the first genome-level catalogue of D. acutus venom proteins and their exochemistry. Our analysis identified an unusually simple venom containing 45 components from 20 distinct protein families. Relative toxin abundances indicate that C-type lectin and C-type lectin-related protein (CTL), snake venom metalloproteinase (svMP), snake venom serine protease (svSP), and phospholipase A2 (PLA2) constitute 90 % of the venom. Bioassays targeting key aspects of viperid envenomation showed considerable concentration-dependent cytotoxicity, particularly in kidney and lung cells, and potent protease and PLA2 activity. Factor Xa and thrombin activities were minor, and no plasmin activity was observed. Effects on haemolysis, intracellular calcium (Ca2+) release, and nitric oxide (NO) synthesis were negligible. Our analysis provides the first holistic genome-based overview of the toxin arsenal of D. acutus, predicting the molecular and functional basis of its life-threatening effects, and opens novel avenues for treating envenomation by this highly dangerous snake.

Coagulation factor XI regulates endothelial cell permeability and barrier function in vitro and in vivo

AbstractLoss of endothelial barrier function contributes to the pathophysiology of many inflammatory diseases. Coagulation factor XI (FXI) plays a regulatory role in inflammation. Although activation of FXI increases vascular permeability in vivo, the mechanism by which FXI or its activated form FXIa disrupts endothelial barrier function is unknown. We investigated the role of FXIa in human umbilical vein endothelial cell (HUVEC) or human aortic endothelial cell (HAEC) permeability. The expression patterns of vascular endothelial (VE)-cadherin and other proteins of interest were examined by western blot or immunofluorescence. Endothelial cell permeability was analyzed by Transwell assay. We demonstrate that FXIa increases endothelial cell permeability by inducing cleavage of the VE-cadherin extracellular domain, releasing a soluble fragment. The activation of a disintegrin and metalloproteinase 10 (ADAM10) mediates the FXIa-dependent cleavage of VE-cadherin, because adding an ADAM10 inhibitor prevented the cleavage of VE-cadherin induced by FXIa. The binding of FXIa with plasminogen activator inhibitor 1 and very low–density lipoprotein receptor on HUVEC or HAEC surfaces activates vascular endothelial growth receptor factor 2 (VEGFR2). The activation of VEGFR2 triggers the mitogen-activated protein kinase (MAPK) signaling pathway and promotes the expression of active ADAM10 on the cell surface. In a pilot experiment using an established baboon model of sepsis, the inhibition of FXI activation significantly decreased the levels of soluble VE-cadherin to preserve barrier function. This study reveals a novel pathway by which FXIa regulates vascular permeability. The effect of FXIa on barrier function may be another way by which FXIa contributes to the development of inflammatory diseases.

Effect of different anticoagulants and antiplatelets on intraoral bleeding time during professional oral hygiene session

ObjectivePatients with thromboembolic problems, prosthetic valves, or coagulation issues are commonly prescribed anticoagulants and antiplatelets. Anticoagulant and antiplatelet medication might constitute a challenge for dentists and dental hygienists since possible prolonged bleeding might interfere with dental procedures. The aim of the present study was to examine the bleeding durations associated with various anticoagulants and antiplatelets during professional dental hygiene sessions, utilizing a modified Ivy test adapted for the oral context.Materials and methodsNinety-three consecutive patients undergoing professional oral hygiene were recruited. Debridement during oral hygiene was performed using ultrasonic mechanical instrumentation, and bleeding sites were assessed and treated with gentle pressure using sterile gauzes. The time for bleeding cessation was recorded. Patients were categorized into six groups based on their drug intake, Control: no anticoagulants or antiplatelets DTI: direct thrombin inhibitors (dabigatran) AntiXa: directa factor Xa inhibitors (endoxaban, apixaban, rivaroxaban) VKA: vitamin K antagonists (warfarin, acenocoumarol) SAPT: single anti-platelet therapy (acetylsalicylic acid or clopidogrel) DAPT: dual anti-platelet therapy (acetylsalicylic acid and clopidogrel). Bleeding time was measured in seconds and mean values were assessed among the different groups. Differences between groups were investigated with Kruskal-Wallis test followed by Dunn’s post-hoc correction for multiple comparisons or two-way ANOVA followed by Dunnett post-hoc;ResultsControl patients presented the lowest bleeding time 50 s, followed by AntiXa (98), SAPT (105), DTI (120), DAPT (190) and VKA (203). A statistically significant difference was present among control and DTI (p = 0.004), VKA (p < 0.001), DAPT (p < 0.001).ConclusionsBased on the present outcomes, an increased risk of prolonged bleeding emerged in patients taking VKA and DAPT.Clinical significancebleeding did not interfere with the oral hygiene session The optimal period for dental treatment of these patients should be 2–3 h before the next dose, without the need to temporarily suspend the medication.

Milvexian: An Oral, Bioavailable Factor XIa Inhibitor.

Direct oral anticoagulants have a dose-dependent increased bleeding risk which limits use in certain populations. Studies in both animals and humans with inherited variations in factor XI levels provide a theoretical basis for a drug target capable of addressing current unmet needs. Milvexian is an oral factor XIa inhibitor that has the potential to provide robust anticoagulant effect without increased bleeding compared with current standard of care. Several key studies in the preclinical, phase I, and phase II stages have reported promising safety data in venous thromboembolism and stroke prevention without compromising hemostasis. The planned phase III trials will examine the efficacy of milvexian for prevention of thrombotic events in patients with acute stroke, acute coronary syndrome, and atrial fibrillation.

Kinetic analysis of prothrombinase assembly and substrate delivery mechanisms

Prothrombinase complex, composed of coagulation factors Xa (FXa) and Va (FVa) is a major enzyme of the blood coagulation network that produces thrombin via activation of its inactive precursor prothrombin (FII) on the surface of phospholipid membranes. However, pathways and mechanisms of prothrombinase formation and substrate delivery are still discussed. Here we designed a novel mathematical model that considered different potential pathways of FXa or FII binding (from the membrane or from solution) and analyzed the kinetics of thrombin formation in the presence of a wide range of reactants concentrations. We observed the inhibitory effect of large FVa concentrations and this effect was phospholipid concentration-dependent. We predicted that efficient FII activation occurred via formation of the ternary complex, in which FVa, FXa and FII were in the membrane-bound state. Prothrombin delivery was mostly membrane-dependent, but delivery from solution was predominant under conditions of phospholipid deficiency or FXa/FVa excess. Likewise, FXa delivery from solution was predominant in the case of FVa excess, but high FII did not switch the FXa delivery to the solution-dependent one. Additionally, the FXa delivery pathway did not depend on the phospholipid concentration, being the membrane-dependent one even in case of the phospholipid deficiency. These results suggest a flexible mechanism of prothrombinase functioning which utilizes different complex formation and even inhibitory mechanisms depending on conditions.

An Inhibitory Single-Domain Antibody against Protein Z-Dependent Protease Inhibitor Promotes Thrombin Generation in Severe Hemophilia A and FXI Deficiency.

Protein Z-dependent protease inhibitor (ZPI) is an anticoagulant serpin that targets factor Xa (FXa) in the presence of protein Z (PZ), and factor XIa (FXIa). In factor-VIII-deficient mice, PZ or ZPI gene knock-out mitigates the bleeding phenotype, and pharmacological inhibition of PZ enhances thrombin generation in plasma from patients with hemophilia. To develop a single-domain antibody (sdAb) directed against ZPI to inhibit its anticoagulant activity. We screened for anti-ZPI sdAbs in a llama-derived phage display immune library of sdAbs. The sdAbs that bound ZPI were produced and purified for characterization. The binding of sdAbs to ZPI or other serpins was evaluated using ELISAs, and ZPI inhibition was measured in an anti-FXa or anti-FXIa chromogenic assay. The sdAbs's procoagulant activity was assessed in a thrombin generation assay in normal plasma, factor VIII- and FXI-deficient plasma. Of the four sdAbs found to bind to ZPI, one (referred to as ZPI-sdAb2) dose-dependently inhibited ZPI's anti-FXa and anti-FXIa activities with a mean half-maximal inhibitory concentration of 1.8 and 1.3 µM, respectively. ZPI-sdAb2 did not cross-react with other plasma serpins, such as antithrombin and α1-antitrypsin. ZPI-sdAb2 induced a significant increase in thrombin generation in plasma samples from healthy donors, patients with severe hemophilia A, and patients with FXI deficiency. ZPI-sdAb2 is the first specific, direct ZPI inhibitor found to exhibit procoagulant activity in plasma. This sdAb might have potential as a treatment for hemophilia or other bleeding disorders.

Beyond Anticoagulation: A Comprehensive Review of Non-Vitamin K Oral Anticoagulants (NOACs) in Inflammation and Protease-Activated Receptor Signaling.

Non-vitamin K oral anticoagulants (NOACs) have revolutionized anticoagulant therapy, offering improved safety and efficacy over traditional agents like warfarin. This review comprehensively examines the dual roles of NOACs-apixaban, rivaroxaban, edoxaban, and dabigatran-not only as anticoagulants, but also as modulators of inflammation via protease-activated receptor (PAR) signaling. We highlight the unique pharmacotherapeutic properties of each NOAC, supported by key clinical trials demonstrating their effectiveness in preventing thromboembolic events. Beyond their established anticoagulant roles, emerging research suggests that NOACs influence inflammation through PAR signaling pathways, implicating factors such as factor Xa (FXa) and thrombin in the modulation of inflammatory responses. This review synthesizes current evidence on the anti-inflammatory potential of NOACs, exploring their impact on inflammatory markers and conditions like atherosclerosis and diabetes. By delineating the mechanisms by which NOACs mediate anti-inflammatory effects, this work aims to expand their therapeutic utility, offering new perspectives for managing inflammatory diseases. Our findings underscore the broader clinical implications of NOACs, advocating for their consideration in therapeutic strategies aimed at addressing inflammation-related pathologies. This comprehensive synthesis not only enhances understanding of NOACs' multifaceted roles, but also paves the way for future research and clinical applications in inflammation and cardiovascular health.

Apixaban Use in Patients with Kidney Impairment: A Review of Pharmacokinetic, Interventional, and Observational Study Data.

Chronic kidney disease (CKD) remains a significant global health issue and is a leading cause of mortality worldwide. Patients with CKD have an increased risk of developing atrial fibrillation (AF) and venous thromboembolism (VTE). While direct oral anticoagulants (DOACs) have become a standard of care for anticoagulation (AC) in patients with AF and VTE, the appropriate use of these agents in comorbid kidney impairment warrants detailed discussion. This scientific narrative review summarizes the effectiveness and safety of apixaban use in patients with renal dysfunction by assessing the current published pharmacokinetic, interventional, observational, and guideline data. Apixaban is a highly selective, orally active, direct inhibitor of factor Xa, with well-established pharmacokinetics and consistent clinical outcomes across a broad range of patient populations, including those with kidney impairment. Overall, the scientific literature has shown that apixaban has a favorable clinical efficacy and safety profile compared with vitamin K antagonists for patients with AF or VTE and comorbid kidney impairment. These data support the approved label dosing strategy of apixaban in reducing the risk of stroke/systemic embolism in patients with nonvalvular AF and in treating VTE across all ranges of kidney function. Both clinician experience and knowledge of patient-specific factors may be required in the management of comorbid patients with advanced CKD or those requiring dialysis, as data on these patients are limited.

Formulation Optimization and Characterization of Solid Lipid Nanoparticles of Apixaban.

Unpredictable situations such as clotting of blood, deep vein thrombosis, and pulmonary embolism arise in the body, which is the leading cause of mortality. Such conditions generally arise after surgery as well as after treatment with oral anticoagulant agents. Apixaban is a novel oral anticoagulant widely recommended for the prevention and treatment of strokes and blood clots suffering from nonvalvular atrial fibrillation by suppressing factor Xa. Apixaban has a log P of 2.71 with poor solubility and reported maximum bioavailability of approximately 50%. Hence, the current research mainly focused on the improvement of solubility, bioavailability, and therapeutic efficacy of Apixaban via solid lipid nanoparticles (SLN). The SLN was developed using the hot-homogenization method using a high-pressure homogenizer. The drug-lipid compatibility study was assessed by the FTIR, and the thermal analysis was performed using differential scanning calorimetry (DSC). During the scrutiny of lipids, the highest solubility of Apixaban was estimated in the glyceryl monostearate, hence selected for the formulation. Moreover, the colloidal solution was stabilized by the polyethylene glycol 200. The Design of Expert software (Version 13, Stat-Ease) was implemented for the optimization analysis by considering the 3-independent factors and 2-dependent parameters. The Patents on the SLN are Indian 202321053691, U.S. Patent, 10,973,798B2, U.S. Patent, U.S. Patent 2021/0069121A1, U.S. Patent 2022/0151945A1. Box-Behnken design was applied along with ANOVA, which showed a p-value less than 0.05 for the dependent parameters such as particle size and entrapment efficiency (p-value: 0.0476 and 0.0379). The optimized batch F10 showed a particle size of 167.1 nm, -19.5 mV zeta potential, and an entrapment efficiency of 87.32%. The optimized batch F10 was lyophilized and analyzed by Scanning electron microscopy (SEM), which showed a particle size of 130 nm. The solid powder was filled into the capsule for oral delivery. The marked improvement in solubility and bioavailability was achieved with F10- loaded Apixaban via Solid lipid nanoparticles. Moreover, the sustained released profile also minimizes the unseen complications that occur due to the clotting of blood.

Structural, Biochemical Characterization and Molecular Mechanism of Cerastokunin: A New Kunitz-Type Peptide with Potential Inhibition of Thrombin, Factor Xa and Platelets.

The current investigation focused on separating Cerastes cerastes venom to produce the first Kunitz-type peptide. Based on its anti-trypsin effect, Cerastokunin, a 7.75kDa peptide, was purified until homogenity by three steps of chromatography. Cerastokunin was found to include 67 amino acid residues that were obtained by de novo sequencing using LC-MALDI-MSMS. Upon alignment with Kunitz-type peptides, there was a high degree of similarity. Cerastokunin's 3D structure had 12% α-helices and 21% β-strands with pI 8.48. Cerastokunin showed a potent anticoagulant effect by inhibiting the protease activity of thrombin and trypsin as well as blocking the intrinsic and extrinsic coagulation pathways. In both PT and aPPT, Cerastokunin increased the blood clotting time in a dose-dependent way. Using Lys48 and Gln192 for direct binding, Cerastokunin inhibited thrombin, Factor Xa and trypsin as shown by molecular docking. Cerastokunin exhibited a dose-response blockade of PARs-dependent pathway platelet once stimulated by thrombin. An increased concentration of Cerastokunin resulted in a larger decrease of tail thrombus in the mice-carrageenan model in an in vivo investigation when compared to the effects of antithrombotic medications. At all Cerastokunin doses up to 6mg/kg, no in vivo toxicity was seen in challenged mice over the trial's duration.

Use of protease substrate specificity screening in the rational design of selective protease inhibitors with unnatural amino acids: Application to HGFA, matriptase, and hepsin.

Inhibition of the proteolytic processing of hepatocyte growth factor (HGF) and macrophage stimulating protein (MSP) is an attractive approach for the drug discovery of novel anticancer therapeutics which prevent tumor progression and metastasis. Here, we utilized an improved and expanded version of positional scanning of substrate combinatorial libraries (PS-SCL) technique called HyCoSuL to optimize peptidomimetic inhibitors of the HGF/MSP activating serine proteases, HGFA, matriptase, and hepsin. These inhibitors have an electrophilic ketone serine trapping warhead and thus form a reversible covalent bond to the protease. We demonstrate that by varying the P2, P3, and P4 positions of the inhibitor with unnatural amino acids based on the protease substrate preferences learned from HyCoSuL, we can predictably modify the potency and selectivity of the inhibitor. We identified the tetrapeptide JH-1144 (8) as a single digit nM inhibitor of HGFA, matriptase and hepsin with excellent selectivity over Factor Xa and thrombin. These unnatural peptides have increased metabolic stability relative to natural peptides of similar structure. The tripeptide inhibitor PK-1-89 (2) has excellent pharmacokinetics in mice with good compound exposure out to 24 h. In addition, we obtained an X-ray structure of the inhibitor MM1132 (15) bound to matriptase revealing an interesting binding conformation useful for future inhibitor design.

Rapid and ordered cleavage of prothrombin by Hopsarin D in the absence of phospholipid membranes

BackgroundThrombin is produced by the prothrombinase complex, composed of factor (f)Xa and fVa on a phospholipid (PL) membrane surface. Snakes of the Elapidae family have venom versions of these factors that cause coagulopathy in prey. Group C venoms contain both fⅩa and fⅤa orthologues. Group D venoms only contain a fXa orthologue and hijack fⅤa of the prey. Hopsarin D (HopD) is the venom fⅩa of the Stephen’s banded snake (Hoplocephalus stephensii). ObjectivesWe set out to address the following: does HopD bind to human fⅤa with high affinity in the absence of PL? Does it process prothrombin through the meizothrombin pathway? Is the order of cleavage PL-dependent? Can HopD activate fⅤ? MethodsWe produced and characterized full-length and truncated HopD. ResultsHopD is only able to clot plasma that contains fⅤ and competes with human fⅩa for fⅤa binding. HopD binds to both human fⅤa and fⅤ with high affinity (dissociation constant, ∼10 nM), in contrast to fⅩa. HopD processes prothrombin down the meizothrombin route in the absence and presence of PL. Although HopD can bind to fⅤ, conversion to fⅤa is necessary for prothrombin processing. HopD initiates clotting in the blood of prey by activating fⅤ. ConclusionHopD binds to fⅤa with high affinity and rapidly activates prothrombin in the absence of PL, exclusively through the meizothrombin intermediate. HopD binds with high affinity to both fⅤa and fⅤ, suggesting that the B-domain does not sterically block fⅩa binding, but inhibits productive interaction in another way, and additionally prevents prothrombin binding.

Neutrophil extracellular traps induce intrahepatic thrombotic tendency and liver damage in cholestatic liver disease.

Cholestatic liver diseases induce local and systemic hypercoagulation, with neutrophil extracellular traps (NETs) serving as major drivers. These NETs have been linked to decreased liver function in patients with obstructive jaundice. However, the impact of NETs on liver hypercoagulation in cholestatic liver disease remains unknown. We utilized bile duct ligation to create experimental mice and analyzed NETs formation in the liver. Fibrin deposition, tissue factor expression, and inflammation in the liver were visualized through western blot and immunohistochemical techniques. LSECs were incubated with isolated NETs, and we detected endothelial procoagulant activity using coagulation protein production assays and measuring endothelial permeability. In both in vivo and in vitro settings, DNase I was applied to clarify the effect of NETs on intrahepatic hypercoagulability, hepatotoxicity, LSEC, and macrophage activation or injury. Bile duct ligation mice exhibited significantly increased levels of NETs in liver tissue, accompanied by neutrophil infiltration, tissue necrosis, fibrin deposition, and thrombophilia compared to sham mice. Notably, NETs resulted in phosphatidylserine and tissue factor exposure on LSEC, enhancing coagulation Factor Xa and thrombin production. The enhanced procoagulant activity could be reversed by degrading NETs with DNase I. Additionally, NETs-induced permeability changes in LSECs, characterized by increased VE-cadherin expression and F-actin retraction, which could be rescued by DNase I. Meanwhile, NET formation is associated with KC activation and the formation of inflammatory factors. NETs promote intrahepatic activation of coagulation and inflammation, leading to liver tissue injury. Strategies targeting NET formation may offer a potential therapeutic approach for treating cholestatic liver disease.