Tissue Factor Pathway Inhibitor Research Articles

TFPIα anticoagulant function is highly dependent on protein S in vivo.

Tissue factor pathway inhibitor α (TFPIα) is the major physiological regulator of the initiation of blood coagulation. In vitro, TFPIα anticoagulant function is enhanced by its cofactor, protein S. To define the role of protein S enhancement in TFPIα anticoagulant function in vivo, we blocked endogenous TFPI in mice using a monoclonal antibody (14D1). This caused a profound increase in fibrin deposition using the laser injury thrombosis model. To explore the role of plasma TFPIα in regulating thrombus formation, increasing concentrations of human TFPIα were coinjected with 14D1, which dose-dependently reduced fibrin deposition. Inhibition of protein S cofactor function using recombinant C4b-binding protein β chain significantly reduced the anticoagulant function of human TFPIα in controlling fibrin deposition. We report an in vivo model that is sensitive to the anticoagulant properties of the TFPIα-protein S pathway and show the importance of protein S as a cofactor in the anticoagulant function of TFPIα in vivo.

Effect of tissue factor pathway inhibitor on the pyroptosis of vascular smooth muscle cells induced by angiotensin II.

In recent years, a mass of studies have shown that pyroptosis plays an important role in the proliferation of vascular smooth muscle cells (VSMCs). We investigated whether angiotensin II (Ang II) induces the pyroptosis of rat aortic VSMCs and the role of NOD-like receptor family pyrin domain containing 3 (NLRP3) in this process. Additionally, we explored the effect and related mechanism of recombinant tissue factor pathway inhibitor (rTFPI) in Ang II-induced VSMC pyroptosis. Cultured VSMCs were divided into five groups: control group, Ang II group (1×10-5 mol/L), MCC950 group (NLRP3 inhibitor, 15 nmol/L), Ang II + MCC950 group and Ang II + rTFPI (50 µg/L) group. Cell viability was measured by cell counting kit-8 (CCK8) assays and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays. Propidium iodide (PI) staining and immunofluorescence were performed to determine the pyroptosis of VSMCs. Changes in VSMC ultrastructure were evaluated through transmission electron microscopy. The expression levels of NLRP3, pro-caspase-1, gasdermin D-N (GSDMD-N), and interleukin-1β (IL-1β) were determined by western blot analysis. The cell viability, the positive rate of PI staining, and the expression level of GSDMD detected by immunofluorescence in the Ang II group were higher than that in the control group, whereas they all decreased in Ang II + MCC950 group and Ang II + rTFPI group compared with Ang II group (P<0.05). Electron microscopy analysis revealed less extracellular matrix, increased myofilaments, and decreased endoplasmic reticulum, Golgi complex, and mitochondria in Ang II + rTFPI-treated VSMCs than in Ang II-treated VSMCs. The protein expression levels of the pyroptosis-related molecules NLRP3, pro-caspase-1, GSDMD-N, and IL-1β in Ang II group showed an increasing trend compared with those in control group (P<0.05); however, these expression levels in Ang II + MCC950 and Ang II + rTFPI groups were significantly lower than those in Ang II group (P<0.05). Ang II may induce pyroptosis in VSMCs by activating NLRP3. rTFPI can inhibit Ang II-induced VSMC pyroptosis. Furthermore, rTFPI might exert this effect by inhibiting the NLRP3 pathway and therefore play an important role in the treatment of vascular remodeling induced by hypertension.

Impact of Estetrol Combined with Drospirenone on Blood Coagulation and Fibrinolysis in Patients with Endometriosis: A Multicenter, Randomized, Open-Label, Active-Controlled, Parallel-Group Study.

Venous thromboembolism is a serious safety concern in women using combined oral contraceptives; ethinyl estradiol (EE) is widely used as an estrogen. Estetrol (E4) is a native estrogen with selective tissue activity and exclusively produced by the fetal liver. This study used a multicenter, randomized, open-label, active-controlled, parallel-group design to evaluate the effects of E4 combined with drospirenone (DRSP) on coagulation and fibrinolysis in Japanese patients with endometriosis. Participants were randomized to receive either E4 15 mg/DRSP 3 mg or EE 20 µg/DRSP 3 mg for 12 weeks. E4/DRSP and EE/DRSP were administered orally once a day in a cyclic regimen, ie, 24-day active use followed by a 4-day hormone-free period, and a flexible extended regimen, respectively, and blood coagulation and fibrinolysis markers were measured. The effect on coagulation and fibrinolysis was considerably less in the E4/DRSP group than in the EE/DRSP group. Major anticoagulant proteins, protein S (free, total) and tissue factor pathway inhibitor (free), were reduced following EE/DRSP treatment. Consequently, thrombin generation determined by the activated protein C sensitivity ratio was increased by approximately 4-fold in the EE/DRSP group than in the E4/DRSP group. Eventually, the fibrinolysis cascade was triggered to compensate for disturbed coagulation, and D-dimer levels were 4.7-fold higher in the EE/DRSP group than in the E4/DRSP group. This study demonstrated that the effect of E4/DRSP on the blood coagulation and fibrinolysis cascades was significantly less than that of EE/DRSP in participants with endometriosis, a disease of women of advanced and reproductive age (jRCT2080225090, https://jrct.niph.go.jp/en-latest-detail/jRCT2080225090).

DOP59 Integration of in silico analysis and in vitro functional analysis reveals Tissue Factor Pathway Inhibitor 2 (TFPI2) as a master transcriptional regulator and potential target to impede Infliximab resistance in adult UC patients

Abstract Background Standard biological therapy for moderate-severe cases of UC consists in the use of Infliximab (IFX), an anti-tumour necrosis factor α (anti-TNF-α) targeting agent. However, approximately 40% of the patients do not respond to IFX. While transcriptional alterations have been widely associated with non-response to IFX, the precise factors that regulates this altered gene expression remains poorly understood. The aim of this study was perform a robust in silico analysis to identify master transcriptional regulators (MTRs) which regulate gene expression changes in IFX non-responsive UC patients, followed by perturbation in vitro to establish their functional role in UC pathogenesis. Methods Differentially expressed genes (DEGs) identified from four independent public datasets were applied to the GeneXplain platform to identify transcription factors (TFs) enriched for the DEG’s. This was followed by an upstream analysis to identify MTR’s which regulate expression of these genes through the TFs. We next explored the role of these MTRs in driving UC-associated phenotype, using siRNA-mediated knock-down in a novel IBD-like in vitro system comprising of normal rectal epithelial cells treated with TNFa. Results Over 200 TFs were identified in both upregulated and downregulated genes in IFX non-responders across all data sets. RELA, NANOG, FOSJUN were the top 3 TF’ enriched for upregulated genes in three out of the four datasets. Using the TF data, the upstream analysis identified CXCL8, SELE, PTGS2, FCGR3, TFPI2 as the top five MTRs. Next, we showed that of the 5 MTRs, only TFPI2 (tissue factor pathway inhibitor 2) were significantly upregulated in an IBD-like in vitro model (normal rectal epithelial cell line: CRL1831 +TNFa). siRNA-mediated knock-down of TFPI2 in this model resulted in a significant decrease in genes including TNFAIP6, TNFAIP3, FCGR3B, BIRC3 and CXCL5, all of which were predicted in silico to be upregulated by TFPI2 during the upstream analysis. Intriguingly, we showed that downregulation of TFPI2 resulted in significant amelioration of pro-inflammatory cytokines including IL1β, IFNγ, IL10, IL13, IL6 and IL8. Conclusion Our study for the first time identifies key MTRs such TFPI2 which acts as a master regulator of genes whose upregulation drives poor response to IFX. Therefore, these results warrant further in vitro/ex vivo investigation to rationalise their role of TFPI2 as a potential therapeutic target, whose perturbation in UC patient would likely result in improved response to IFX.

Shifting Paradigms and Arising Concerns in Severe Hemophilia A Treatment.

The management of hemophilia A has undergone a remarkable revolution, in line with technological advancement. In the recent past, the primary concern associated with Factor VIII (FVIII) concentrates was the risk of infections, which is now almost resolved by advanced blood screening and viral inactivation methods. Improving patients' compliance with prophylaxis has become a key focus, as it can lead to improved health outcomes and reduced health care costs in the long term. Recent bioengineering research is directed toward prolonging the recombinant FVIII (rFVIII) coagulant activity and synthesising higher FVIII yields. As an outcome, B-domain deleted, polyethylene glycolated, single-chain, Fc-fused rFVIII, and rFVIIIFc-von Willebrand Factor-XTEN are available for patients. Moreover, emicizumab, a bispecific antibody, is commercially available, whereas fitusiran and tissue factor pathway inhibitor are in clinical trial stages as alternative strategies for patients with inhibitors. With these advancements, noninfectious complications, such as inhibitor development, allergic reactions, and thrombosis, are emerging concerns requiring careful management. In addition, the recent approval of gene therapy is a major milestone toward a permanent cure for hemophilia A. The vast array of treatment options at our disposal today empowers patients and providers alike, to tailor therapeutic regimens to the unique needs of each individual. Despite significant progress in modern treatment options, these highly effective therapies are markedly more expensive than conventional replacement therapy, limiting their access for patients in developing countries.

Urinary tissue factor (uTF), tissue factor pathway inhibitor (TFPI) and plasmin as novel biomarkers in early diagnosis of lupus nephritis

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease, with multi systematic affection. Lupus nephritis (LN) is the most frequent cause of renal damage in SLE patients with variable presentations that may progress to end stage renal failure. Coagulation disorders are frequently reported in SLE and LN with higher mortality rates. Renal biopsy is an invasive process, and the existing indicators for LN diagnosis and activity are unreliable. New urinary biomarkers with significant validity, safety, and accuracy are the current focus of most studies. Our study sought to assess the value of urinary tissue factor (uTF), tissue factor pathway inhibitor (TFPI), and plasmin as biomarkers for the early identification and detection of LN and its activity. This was a cross-sectional study, included 100 subjects (80 SLE patients, and 20 healthy controls), they were recruited from the Internal Medicine department, Rheumatology and Nephrology units and outpatient’s clinics at Assiut University hospital between the period of 2020 and 2022. All patients underwent full history taking, clinical evaluation, and activity scoring calculation and laboratory investigations. The results showed that the best diagnostic accuracy of LN was observed with TFPI (90% accuracy, sensitivity 80% and specificity 95% with p&lt;0.001 at cutoff point of &gt;193.2 ng/ml), followed by uTF (75.4% overall accuracy at cut off point of &gt;12.6 ng/ml, sensitivity 90% and specificity 68% with p&lt; 0.001) and plasmin (70.3% accuracy at cut off point of &gt;30.5 ng/ml, sensitivity 55% and specificity 78% with p&lt; 0.001). Urinary TFPI was the best predictor of LN occurrence with odd ratio of 4.34, (p&lt; 0.001). In conclusion urinary TFPI could be used as a diagnostic marker for LN with high accuracy and an early predictor of LN.

Specific expression and blood kinetics for relaxin 2, lipocalin 2, and tissue factor pathway inhibitor 2 at the canine placenta and pregnant bloods.

In general, humoral factors released from the placenta influence pregnancy progression, but the involvement of the canine placenta is often unidentified. We investigated specific genes in canine placentas and analyzed the blood dynamics of the translated proteins. Furthermore, RNAs are known to be released from placentas embedding in exosomes, a type of extracellular vesicles. Here, the presence of cell-free RNAs in pregnant serums was also confirmed. RNA specimens were purified from the normal healthy dog placentas and applied to RNA-Seq analysis. Expressions of frequent genes were confirmed by RT-PCR using placentas from other individuals and breeds. Relaxin (RLN) 2, lipocalin (LCN) 2, and tissue factor pathway inhibitor (TFPI) 2 were selected as high-expressed and placenta-specific genes. By western blot, the three factors were clearly detected in the pregnant serums. Quantitative analysis revealed that the amount of RLN2 increased significantly from non-pregnancy to day 41 of pregnancy. Regarding LCN2 and TFPI2, the protein serum levels elevated during pregnancy, but the statistical differences were not detected. Exosomes were found in all pregnant serums; however, the percentage was less than 6% in total extracellular vesicles. The cell-free RNA related to RLN2 was detected, but no elevation was confirmed during pregnancy. We found specific genes in the canine placenta and the transition of their translated protein into the blood. These factors may become useful tools for research on canine pregnancy and monitoring of reproductive management. Exosomes and cell-free RNA could not be found to be valid in canine reproduction.

Angiology and hemostasis: what's new in 2023

We discuss four topics among the angiology and hemostasis studies of importance in 2023. The BASIL-2 study provides new data for the management of chronic limb-threatening ischemia by comparing surgical and endovascular treatment. The new classification of antiphospholipid antibody (aPL) syndrome integrates new clinical elements and gives a different weight among the isotype and titer of aPL. Concizumab, an antibody targeting the tissue factor pathway inhibitor, broadens the therapeutic arsenal for hemophilia A and B as evidenced by the results of the EXPLORER 7 study. The PREVENT-CLOT and CASTING study focus on the prevention of thrombosis after trauma, by testing the role of aspirin or the lack of thromboprophylaxis, respectively.

Tissue factor pathway-related biomarkers in liver cancer: activated factor VII–antithrombin complex and tissue factor mRNA levels are associated with mortality

BackgroundTissue factor (TF), the main initiator of the coagulation cascade, plays a role in cancer progression and prognosis. Activated factor VII–antithrombin complex (FVIIa-AT) is considered an indirect marker of TF exposure by reflecting TF-FVIIa interaction. ObjectivesTo assess the link between FVIIa-AT plasma levels, TF messenger RNA (mRNA) expression, and survival in cancer. MethodsTF pathway–related coagulation biomarkers were assessed in 136 patients with cancer (52 with hepatocellular carcinoma, 41 with cholangiocarcinoma, and 43 with colon cancer) undergoing surgical intervention with curative intent. TF mRNA expression analysis in neoplastic vs nonneoplastic liver tissues was evaluated in a subgroup of 91 patients with primary liver cancer. ResultsFVIIa-AT levels were higher in patients with cancer than in 136 sex- and age-matched cancer-free controls. In patients with cancer, high levels of FVIIa-AT and total TF pathway inhibitor were associated with an increased mortality risk after adjustment for confounders, but only FVIIa-AT remained a predictor of mortality by including both FVIIa-AT and total TF pathway inhibitor in Cox regression (hazard ratio, 2.80; 95% CI, 1.23-6.39; the highest vs the lowest quartile). This association remained significant even after adjustment for extracellular vesicle–associated TF-dependent procoagulant activity. In the subgroup of patients with primary liver cancer, patients with high TF mRNA levels had an increased mortality risk compared with that for those with low TF mRNA levels (hazard ratio, 1.92; 95% CI, 1.03-3.57), and there was a consistent correlation among high FVIIa-AT levels, high TF mRNA levels, and increased risk of mortality. ConclusionHigh FVIIa-AT levels may allow the identification of patients with cancer involving high TF expression and predict a higher mortality risk in liver cancer.

Curcumin inhibits the invasion and migration of pancreatic cancer cells by upregulating TFPI-2 to regulate ERK- and JNK-mediated epithelial-mesenchymal transition.

Pancreatic cancer (PC) is one of the most deadly human malignancies. Curcumin is a natural polyphenolic compound with wide-ranging pharmacological effects. Growing evidence suggests that curcumin has anticancer activity against PC, but the mechanism remains incompletely elucidated. This study aimed to investigate the effects and mechanisms of curcumin on the invasion and migration of PC cells. Effect of curcumin on tissue factor pathway inhibitor (TFPI)-2 mRNA expression in PC cells was initially identified using qRT-PCR. Cytotoxicity of curcumin was assessed with MTT assays and IC50 was calculated. Involvement of ERK and JNK pathways, as well as protein expression of TFPI-2 and epithelial-mesenchymal transition (EMT)-related markers, were detected using immunoblotting. Invasion and migration of PC cells were examined using Transwell assays. TFPI-2 expression was manipulated by transfection with siRNA and shRNA. Rescue assays were used to validate the effect of curcumin on cell invasion and migration via TFPI-2. Curcumin increased the expression of TFPI-2 mRNA and protein in PC cells and attenuated cell invasion and migration. Curcumin also inhibited ERK and JNK pathways and EMT in PC cells. Knockdown of TFPI-2 partially reversed the inhibition of ERK and JNK pathways and EMT by curcumin. Mechanistically, curcumin upregulated TFPI-2, thereby inhibiting the ERK and JNK pathways, leading to the inhibition of EMT in PC cells. Collectively, curcumin inhibits ERK- and JNK-mediated EMT through upregulating TFPI-2, which in turn suppresses the migration and invasion of PC cells. These findings provide new insights into the antitumor mechanism of curcumin.

Coagulopathy and adverse outcomes in hospitalized patients with COVID-19: results from the NOR-Solidarity trial

BackgroundSeveral studies have examined parameters of increased thrombogenicity in COVID-19, but studies examining their association with long-term outcome and potential effects of antiviral agents in hospitalized patients with COVID-19 are scarce. ObjectivesTo evaluate plasma levels of hemostatic proteins during hospitalization in relation to disease severity, treatment modalities, and persistent pulmonary pathology after 3 months. MethodsIn 165 patients with COVID-19 recruited into the NOR-Solidarity trial (NCT04321616) and randomized to treatment with hydroxychloroquine, remdesivir, or standard of care, we analyzed plasma levels of hemostatic proteins during the first 10 days of hospitalization (n = 160) and at 3 months of follow-up (n = 100) by enzyme immunoassay. ResultsOur main findings were as follows: (i) tissue plasminogen activator (tPA) and tissue factor pathway inhibitor (TFPI) were increased in patients with severe disease (ie, the combined endpoint of respiratory failure [Po2-to-FiO2 ratio, <26.6 kPa] or need for treatment at an intensive care unit) during hospitalization. Compared to patients without severe disease, tPA levels were a median of 42% (P < .001), 29% (P = .002), and 36% (P = .015) higher at baseline, 3 to 5 days, and 7 to 10 days, respectively. For TFPI, median levels were 37% (P = .003), 25% (P < .001), and 10% (P = .13) higher in patients with severe disease at these time points, respectively. No changes in thrombin-antithrombin complex; alpha 2-antiplasmin; a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13; or antithrombin were observed in relation to severe disease. (ii) Patients treated with remdesivir had lower levels of TFPI than those in patients treated with standard of care alone. (iii) TFPI levels during hospitalization, but not at 3 months of follow-up, were higher in those with persistent pathology on chest computed tomography imaging 3 months after hospital admission than in those without such pathology. No consistent changes in thrombin-antithrombin complex, alpha 2-antiplasmin, ADAMTS-13, tPA, or antithrombin were observed in relation to pulmonary pathology at 3 months of follow-up. ConclusionTFPI and tPA are associated with severe disease in hospitalized patients with COVID-19. For TFPI, high levels measured during the first 10 days of hospitalization were also associated with persistent pulmonary pathology even 3 months after hospital admittance.

The interplay between tamoxifen and endoxifen plasma concentrations and coagulation parameters in patients with primary breast cancer

BackgroundTamoxifen is an effective treatment for primary breast cancer but increases the risk for venous thromboembolism. Tamoxifen decreases anticoagulant proteins, including antithrombin (AT), protein C (PC) and tissue factor (TF) pathway inhibitor, and enhances thrombin generation (TG). However, the relation between plasma concentrations of both tamoxifen and its active metabolite endoxifen and coagulation remains unknown. MethodsTamoxifen and endoxifen were measured in 141 patients from the prospective open-label intervention TOTAM-study after 3 months (m) and 6 m of tamoxifen treatment. Levels of AT and PC, the procoagulant TF, and TG parameters were determined at both timepoints if samples were available (n = 53–135 per analysis). Levels of coagulation proteins and TG parameters were correlated and compared between: 1) quartiles of tamoxifen and endoxifen levels, and 2) 3 m and 6 m of treatment. ResultsAt 3 m, levels of AT, PC, TF and TG parameters were not associated with tamoxifen nor endoxifen levels. At 6 m, median TF levels were lower in patients in the 3rd (56.6 [33] pg/mL), and 4th (50.1 [19] pg/mL) endoxifen quartiles compared to the 1st (lowest) quartile (76 [69] pg/mL) (P=0.027 and P=0.018, respectively), but no differences in anticoagulant proteins or TG parameters were observed. An increase in circulating TF levels (3 m: 46.0 [15] versus 6 m: 54.4 [39] pg/mL, P < 0.001) and TG parameters was observed at the 6 m treatment timepoint, while AT and PC levels remained stable. ConclusionsOur results indicate that higher tamoxifen and endoxifen levels are not correlated with an increased procoagulant state, suggesting tamoxifen dose escalation does not further promote hypercoagulability.

Women have less progression of paroxysmal atrial fibrillation: data from the RACE V study

BackgroundSex differences in atrial fibrillation (AF) are observed in terms of comorbidities, symptoms, therapies received, AF progression and cardiovascular complications.MethodsWe assessed the differences in prevalence and the determinants of AF...

Lacticaseibacillus rhamnosus CRL1505 Peptidoglycan Modulates the Inflammation-Coagulation Response Triggered by Poly(I:C) in the Respiratory Tract

Lacticaseibacillus rhamnosus CRL1505 beneficially modulates the inflammation-coagulation response during respiratory viral infections. This study evaluated the capacity of the peptidoglycan obtained from the CRL1505 strain (PG-Lr1505) to modulate the immuno-coagulative response triggered by the viral pathogen-associated molecular pattern poly(I:C) in the respiratory tract. Adult BALB/c mice were nasally treated with PG-Lr1505 for two days. Treated and untreated control mice were then nasally challenged with poly(I:C). Mice received three doses of poly(I:C) with a 24 h rest period between each administration. The immuno-coagulative response was studied after the last administration of poly(I:C). The challenge with poly(I:C) significantly increased blood and respiratory pro-inflammatory mediators, decreased prothrombin activity (PT), and increased von Willebrand factor (vWF) levels in plasma. Furthermore, tissue factor (TF), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM) expressions were increased in the lungs. PG-Lr1505-treated mice showed significant modulation of hemostatic parameters in plasma (PT in %, Control = 71.3 ± 3.8, PG-Lr1505 = 94.0 ± 4.0, p &lt; 0.01) and lungs. Moreover, PG-Lr1505-treated mice demonstrated reduced TF in F4/80 cells from lungs, higher pro-inflammatory mediators, and increased IL-10 compared to poly(I:C) control mice (IL-10 in pg/mL, Control = 379.1 ± 12.1, PG-Lr1505 = 483.9 ± 11.3, p &lt; 0.0001). These changes induced by PG-Lr1505 correlated with a significant reduction in lung tissue damage. Complementary in vitro studies using Raw 264.7 cells confirmed the beneficial effect of PG-Lr1505 on poly(I:C)-induced inflammation, since increased IL-10 expression, as well as reduced damage, production of inflammatory mediators, and hemostatic parameter expressions were observed. In addition, protease-activated receptor-1 (PAR1) activation in lungs and Raw 264.7 cells was observed after TLR3 stimulation, which was differentially modulated by PG-Lr1505. The peptidoglycan from L. rhamnosus CRL1505 is able to regulate inflammation, the procoagulant state, and PAR1 activation in mice and macrophages in the context of the activation of TLR3 signaling pathways, contributing to a beneficial modulation of inflammation-hemostasis crosstalk.

Tissue Factor Pathway Inhibitor (TFPI) Beta and Gamma Isoforms Contribute to Bleeding in Hemophilia Mice

Key Points: Expression of any single TFPI isoform (α, β, or γ) is sufficient for mouse survival.Two-Kunitz domain TFPI isoforms, anchored β and circulating γ, each contribute to hemophilia bleeding.In vivo, TFPIβ is a more potent anticoagulant than TFPIα. Upon injury, tissue factor (TF) triggers coagulation by complexing with factor (F)VIIa to activate FIX and FX, leading to thrombin generation and a fibrin clot. Tissue factor pathway inhibitor limits TF-triggered coagulation. Humans and mice express transcripts encoding for 3-Kunitz domain TFPIα and membrane-anchored 2-Kunitz TFPIβ. Mice also express transcripts encoding untethered, 2-Kunitz TFPIγ. In humans, proteolysis of TFPIα and/or β produces “γ-like” 2-Kunitz TFPI. Hemophilia A and B, caused by deficiency in factors VIII and IX, respectively, are congenital X-linked recessive bleeding disorders that affect an estimated 1.1 million males worldwide. Hemophilia can cause excessive bleeding spontaneously or in response to trauma that can be life-threatening or significantly decrease the quality of life. Approved treatments for hemophilia include factor replacement, bypassing agents, the bispecific antibody Emicizumab, and recently approved gene therapies. Also in development are agents that reduce endogenous anticoagulant activity to counter the procoagulant deficiency of hemophiliacs, including monoclonal antibodies (Mab) to TFPI. These Mab target all TFPI isoforms to improve coagulation and correct bleeding in hemophilia patients, but with some demonstrated thrombosis risk. We investigated if TFPI-isoform-specific inhibition could provide equivalent efficacy which might reduce thrombotic risk. We generated TFPI-isoform-specific exon deletions in mice bred into hemophilia (FVIII-null) background. We find mice expressing any single TFPI isoform (α, β, or γ) appear healthy and reproduce. Our in vivo tail-vein re-bleeding assay is based on serial clot disruptions over 15 minutes, which we have shown is sensitive to anticoagulant and antiplatelet treatment, as well as factor replacement therapy. In this assay, we find C57Bl/6 WT mice clot 25.6 + 0.8 times (mean + SEM), whereas FVIII-null hemophilia mice clot 5.3 +0.4 times. In hemophilia mice, TFPIα-specific deletion is without impact, forming clots 5.1 + 0.8 times, whereas TFPIβ-specific or TFPIγ-specific deletion improves clot formation to 16.8 + 2.0 and 15.2 + 1.5 times, respectively (p&amp;lt;0001). Even hemophilia mice with heterozygotic deletion of the β exon form clots 11.8 + 0.8 times (p&amp;lt;0001). Thus, in vivo 2-Kunitz TFPI isoforms, anchored β and untethered γ each provides greater anticoagulant activity and impact on bleeding than 3-Kunitz TFPIα. Ex vivo plasma-based thrombin generation assays show that TFPIγ provides more anticoagulant activity than TFPIα. As shown in the figure, the deletion of TFPIγ increases thrombin generation to a greater extent than the deletion of TFPIα. The addition of an anti-TFPI antibody that effectively blocks TFPI activity shows a significant increase in endogenous thrombin potential in the plasma of TFPIαβ-deleted (γ-only) mice (370 nM.min), versus TFPIβγ-deleted (α-only) plasma (70 nM.min) and TFPIαγ-deleted (β-only) mice plasma (22 nM.min), (p&amp;lt;0.001). As expected, membrane-anchored TFPIβ is not detected in plasma. It is well established that 3-Kunitz TFPIα is a potent anticoagulant in plasma-based clotting time assays, while truncated 2-Kunitz TFPI, like mouse TFPIγ, appears inactive. Based on such assays, it was unexpected that TFPIγ-only expressing mice thrive, and in vivo, TFPIα is not the dominant endogenous anticoagulant. If mouse models are to be useful in providing insights into human hemostasis and TF-associated diseases, then it is critical to understand the similarities and differences between mice and humans. As humans do not express TFPIγ, the observed impact of depleting circulating 2-Kunitz TFPI on bleeding and thrombin generation in hemophilic mice is unlikely to translate to man. By contrast, our results demonstrating that, in vivo, TFPIβ is a more potent anticoagulant than TFPIα in mice has potential therapeutic implications in humans.

Hemostatic imbalance underlying preterm delivery in COVID-19 convalescent patients

Aim: to study the role of the hemostatic system in pretem delivery in pregnant women who have had COVID-19 in the gestation period from 14 to 16 weeks.Materials and Methods. A prospective single-center observational study was conducted by enrolling 63 pregnant women with verified COVID-19 at 14–16 weeks of gestation. The main group consisted of 37 patients with preterm birth (PB), comparison group – 26 patients labour activity that occurred at least at gestational age of 37 weeks. Clinical and anamnestic data and dynamic changes in fibrinogen and D-dimer level, activity of tissue factor (TF), tissue factor pathway inhibitor (TFPI), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA) were analyzed; thrombin generation assay (TGA) was performed.Results. It was found that severity of COVID-19 infection did not determine the timing of delivery that depended on patient comorbid condition. All PB observations (37 out of 63, 58.7 %) were caused by decompensated placental function manifested by acute obstetrical complications: increasing intrauterine fetal hypoxia (64.9 %) along with intrauterine growth retardation (51.4 %), severe preeclampsia (13.5 %) and premature abruption of the normally located placenta (5.0 %). In both study groups, COVID-19 experienced at 14–16 weeks of pregnancy was associated with coagulation and fibrinolytic imbalances. At the same time, at least 6 weeks post-COVID-19 infection, patients with PB had higher level of the “Peak thrombin” vs. comparison group (3050 vs. 2527 pmol/L; p = 0.0433). Also, patients with term vs. preterm delivery had TF activity decreased significantly: by 47.1% and 28.1%, respectively (p = 0.0546). Patients in preterm delivery group were characterized by fibrinolytic imbalance. At the first time point, suppressed fibrinolysis (PAI-1 level – 18.4 vs. 12.5 ng/ml in the comparison group; p = 0.0209) was concomitant with elevated level of u-PA (1.5 vs. 0.55 ng/ml in comparison group, p = 0.0015), which suggests a potential prolonged immunoinflammatory response in patients with PB. Magnitude of fibrinogen concentration and D-dimer level during post-COVID-19 follow-up study was within the reference values specific to gestational age.Conclusion. A significant increase in coagulation potential was found and verified by elevated activity of tissue factor and potential to thrombin generation in COVID-19 convalescent patients. In the case of preterm delivery, there was an imbalance in fibrinolysis system revealed by decreased blood fibrinolytic activity elevating along with increasing gestational age.

Marstacimab, an Anti-Tissue Factor Pathway Inhibitor, in Participants with Hemophilia Α or B, with and without Inhibitors: An Integrated Analysis of Safety

Background: Marstacimab (PF-06741086) targets tissue factor pathway inhibitor (TFPI) to restore hemostasis via the extrinsic pathway of blood coagulation. In phase 1/2 studies, long-term subcutaneous (SC) administration of marstacimab reduced bleeding episodes in adults with severe hemophilia A (HA) or hemophilia B (HB) (factor VIII or factor IX [FIX] ˂1%, respectively), with or without inhibitors. BASIS, the pivotal phase 3 study of marstacimab in adolescents and adults with severe HA (&amp;lt;1%) or moderately severe to severe (FIX ≤2%) HB, is ongoing. Given the potential risk for thrombotic and thromboembolic complications with novel non-factor-based agents, integrated safety analysis of studies of such agents are of interest. Wereport an integrated analysis of marstacimab safety in participants with HA or HB. Methods: Data from participants in the phase 1b/2 study (NCT02974855), its long-term follow-up (LTFU; NCT03363321), the pivotal phase 3 BASIS study (NCT03938792), and its long-term extension (LTE; NCT05145127) were included. In the phase 1b/2 study, male participants (N=26) with severe HA or HB, with or without inhibitors, were assigned to escalating weekly SC doses of marstacimab based on inhibitor status (without inhibitors: 300 mg, a single 300-mg loading dose with subsequent 150-mg doses, or 450 mg; with inhibitors: 300 mg). In the BASIS study, male participants (N=163) with severe HA or moderately severe to severe HB, with or without inhibitors, received a single SC 300-mg loading dose followed by once-weekly 150 mg in the 12-month active treatment phase (ATP). Adverse events (AEs), serious adverse events (SAEs), and AEs of special interest (AESI), including thromboembolic events and injection site reactions (ISRs), were monitored. Results: Overall, 144 unique participants received marstacimab and were included in this analysis: 28 in the phase 1b/2 study (median treatment duration, 2.8 [range, 1.2-3.0] months) and its LTFU (15.0 [1.2-16.4] months) and 116 in the BASIS study (12.1 [0.9-13.1] months) and its LTE (6.4 [1.1-16.1] months; overall BASIS + LTE, 17.3 [0.9-28.2] months). Demographics, baseline characteristics, and marstacimab treatment and dosing ( Table 1) and a summary of safety are shown in Table 2. There were no treatment-related SAEs in the phase 1b/2 study and 1 treatment-related SAE (peripheral swelling) in the BASIS study and its LTE. There were no deaths in any study. There were no AEs related to thromboembolism during treatment in participants with HA or HB across the marstacimab clinical program. Adverse drug reactions were consistent across studies. In the BASIS study and its LTE, ISRs (n=13, 11.2%) tended to be transient and mild in severity and did not lead to discontinuation from the study: other reactions were also mild: pruritus (n=4, 3.4%); rash (n=1, 0.9%) and headache (n=8, 6.9%). One participant, with a history of hemorrhoids, in the BASIS ATP had a grade 2 event of thrombosed hemorrhoids considered related to marstacimab (a local inflammation event, not related to any other thromboembolic event; dose was not interrupted or changed due to this event). No clinically important findings in laboratory values were associated with marstacimab. In the BASIS ATP, antidrug antibodies (ADAs) developed in 23/112 participants (20.5% incidence; titers were low and resolved in 22/23 participants by end of study); 6/23 were positive for neutralizing antibodies (NAbs; titers were transient and resolved by the end of study). In the LTE, ADA developed in 1/44 (2.3%) participants; the ADA titer was negative prior to marstacimab but positive at the end of the main study (titer = 2.48), positive at Day 180 in the LTE (titer = 2.41), and the participant tested negative for NAbs at both timepoints. No differences in the marstacimab safety profile, as determined by AEs, SAEs, AESIs, and discontinuations due to AEs, were reported in ADA positive or negative participants. Across the BASIS study and its LTE, 18 participants had a marstacimab dose escalation from 150 mg to 300 mg; 8/18 (44.4%) had AEs, all mild or moderate in severity and there were no AEs or SAEs leading to treatment discontinuation. Conclusion: Once-weekly SC marstacimab was well tolerated in participants with severe HA or moderately severe to severe HB, without inhibitors, with a low rate and mild severity of ISRs, transient ADAs, and no thromboembolic events with continuous treatment up to 28 months in the phase 3 program.

Efficacy and Safety of the Anti-Tissue Factor Pathway Inhibitor Marstacimab in Participants with Severe Hemophilia without Inhibitors: Results from the Phase 3 Basis Trial

Background:Marstacimab (PF-06741086) is a monoclonal antibody targeted to the tissue factor pathway inhibitor protein to improve hemostasis via the extrinsic pathway of blood coagulation. Previous phase 1/2 studies demonstrated the efficacy and safety of long-term administration of marstacimab up to 450 mg weekly for reducing bleeding episodes in adults with severe hemophilia A (HA) or hemophilia B (HB), with or without inhibitors, compared with on-demand (OD) therapy. We evaluated the efficacy and safety of marstacimab in participants with severe HA or moderately severe to severe HB without inhibitors compared with previous factor replacement therapy. Methods: BASIS (NCT03938792) is an open-label, multicenter, pivotal phase 3 study that enrolled male participants aged ≥12 to ˂75 y with severe HA (factor [F] VIII ˂1%) or moderately severe to severe (FIX ≤2%) HB, with or without inhibitors. Following screening, participants entered a 6-month observational phase (OP) and were categorized by factor replacement treatment: (1) OD or (2) routine prophylaxis (RP). Participants who completed the OP crossed over to 12-month active treatment phase (ATP) and received a single subcutaneous loading dose of 300 mg followed by once weekly 150 mg marstacimab. Primary endpoints were annualized bleeding rate (ABR) for treated bleeds and safety outcomes. Secondary endpoints included incidence of various types of breakthrough bleeds and health-related quality of life (HRQoL) measures. Participants who completed the ATP were eligible to enroll in the long-term extension (LTE) study. Informed consent/ethics committee approvals were obtained. Results for participants without inhibitors are presented. Results: Participants (N=128; 108 adults, 20 adolescents) with HA or HB without inhibitors entered the OP (OD: HA n=29, HB n=8; RP: n=72, HB n=19); of these, 116 entered the ATP. The median age was 30 [range, 13-66] y, most participants were White (50.8%) or Asian (47.7%) and predominately from Europe and India (51.6%). At baseline, 89 participants (69.5%; OD: n=36; RP: n=53) had ≥1 target joint. Mean (range) duration of marstacimab treatment was 12.1 (11.5-13.1) months for OD and 11.6 (0.9-12.8) months for RP. Eighty-eight participants entered the LTE (OD: HA n=22, HB n=7; RP: HA n=45; HB n=13). Data were not available by the cutoff date for 1 RP participant and was not included in the LTE safety analysis set. The mean (range) treatment duration in the LTE was 8.0 (1.2-14.5) months for OD and 6.5 (1.1-16.1) months for RP. In the phase 3 study, the OD group reported 12 (36.4%) adverse events (AEs) during ATP vs 9 (24.3%) in OP whereas the RP group reported 62 (74.7%) AEs in ATP vs 20 (22.0%) in OP. Both groups reported more treatment-related AEs during ATP ( Table 1). ADAs developed in 23/112 participants (20.5% incidence), of which titers were low and resolved in 22 participants by end of study. One RP participant discontinued due to a non-treatment-related SAE, and no deaths or thromboembolic events were recorded in the phase 3 study or the LTE. Mean (95% CI) ABR for treated bleeds was reduced for OD (91.6% [88.1-94.1%]) and RP (35.2% [5.6-55.6%]) participants over the 12-month ATP and marstacimab demonstrated superiority vs OD (P&amp;lt;0.001) and non-inferiority and superiority vs RP (P=0.0376) therapy. Marstacimab was also associated with significant reductions in ABR across all breakthrough bleed categories vs OD, and numerical reductions vs RP (non-inferiority). Overall, mean ABR declined over the first 6 months of ATP, which continued to Month 12 (data not shown). Bleed rates for an additional 16 months of follow-up in the LTE were consistent with those observed during the first 12 months of treatment in the phase 3 study ( Table 2). The ABR reductions observed with marstacimab during ATP were consistent across hemophilia types and age groups for OD and were generally consistent across hemophilia types and age groups for RP, with all point estimates for a difference &amp;lt;2.5 (non-inferiority margin for the ABR of treated bleeds). HRQoL parameters demonstrated non-significant improvements vs OD therapy and non-inferiority vs RP therapy. Conclusion: Compared with previous OD or RP therapy, once weekly subcutaneous marstacimab was safe and effective for reducing bleeding events in participants with severe HA or moderately severe to severe HB without inhibitors beyond 12 months in the phase 3 study and up to an additional 16 months in the LTE study.

Statins Effects on Blood Clotting: A Review.

Statins are powerful lipid-lowering drugs that inhibit cholesterol biosynthesis via downregulation of hydroxymethylglutaryl coenzyme-A reductase, which are largely used in patients with or at risk of cardiovascular disease. Available data on thromboembolic disease include primary and secondary prevention as well as bleeding and mortality rates in statin users during anticoagulation for VTE. Experimental studies indicate that statins alter blood clotting at various levels. Statins produce anticoagulant effects via downregulation of tissue factor expression and enhanced endothelial thrombomodulin expression resulting in reduced thrombin generation. Statins impair fibrinogen cleavage and reduce thrombin generation. A reduction of factor V and factor XIII activation has been observed in patients treated with statins. It is postulated that the mechanisms involved are downregulation of factor V and activated factor V, modulation of the protein C pathway and alteration of the tissue factor pathway inhibitor. Clinical and experimental studies have shown that statins exert antiplatelet effects through early and delayed inhibition of platelet activation, adhesion and aggregation. It has been postulated that statin-induced anticoagulant effects can explain, at least partially, a reduction in primary and secondary VTE and death. Evidence supporting the use of statins for prevention of arterial thrombosis-related cardiovascular events is robust, but their role in VTE remains to be further elucidated. In this review, we present biological evidence and experimental data supporting the ability of statins to directly interfere with the clotting system.

Structural architecture of the acidic region of the B domain of coagulation factor V

BackgroundCoagulation factor (F)V features an A1-A2-B-A3-C1-C2 domain organization and functions as the inactive precursor of FVa, a component of the prothrombinase complex required for rapid thrombin generation in the penultimate step of the coagulation cascade. An intramolecular interaction within the large B domain (residues 710-1545) involves the basic region (BR, residues 963-1008) and acidic region (AR, residues 1493-1537) and locks FV in its inactive state. However, structural information on this important regulatory interaction or on the separate architecture of the AR and BR remains elusive due to conformational disorder of the B domain. ObjectivesTo reveal the structure of the BR-AR interaction or of its separate components. MethodsThe structure of FV is solved by cryogenic electron microscopy. ResultsA new 3.05 Å resolution cryogenic electron microscopy structure of FV confirms the overall organization of the A and C domains but resolves the segment 1507 to 1545 within a largely disordered B domain. The segment contains most of the AR and is organized as recently reported in FV short, a spliced variant of FV with a significantly shorter and less disordered B domain. ConclusionThe similar architecture of the AR in FV and FV short provides structural context for physiologically important interactions of this region with the BR in FV and with the basic C-terminal end of tissue factor pathway inhibitor α in FV short.