Heparanase, an endo-β-d-glucuronidase produced by a variety of cells and tissues, cleaves the glycosidic linkage between glucuronic acid (GlcA) and a 3-O- or 6-O-sulfated glucosamine, typified by the disaccharide -[GlcA-GlcNS3S6S]-, which is found within the antithrombin-binding domain of heparan sulfate or heparin. As such, all current forms of heparin are susceptible to degradation by heparanase with neutralization of anticoagulant properties. Here, we have designed a heparanase-resistant, ultralow molecular weight heparin as the structural analogue of fondaparinux that does not contain an internal GlcA residue but otherwise displays potent anticoagulant activity. This heparin oligosaccharide was synthesized following a chemoenzymatic scheme and displays nanomolar anti-FXa activity yet is resistant to heparanase digestion. Inhibition of thrombus formation was further demonstrated after subcutaneous administration of this compound in a murine model of venous thrombosis. Thrombus inhibition was comparable to that observed for enoxaparin with a similar effect on bleeding time.

The enzyme heparanase cleaves heparan sulfate and is involved in a range of human diseases including cancer, inflammation, diabetes, and viral infection. There is a need for a simple and reliable enzymatic assay to allow for the screening of compounds to find inhibitors of heparanase. We have developed an assay that uses the heparinoid fondaparinux as enzyme substrate and detects one of the products of catalysis, which contains a newly formed reducing terminus, with the tetrazolium salt WST-1. Due to the homogenous substrate and single point of cleavage therein, this assay allows for more systematic kinetic analysis of heparanase inhibitors. Here, we provide a detailed method for conducting this assay and also provide information to assist researchers in evaluating whether the assay is performing properly in their laboratories.

Fondaparinux sodium is a chemically synthesized selective factor Xa inhibitor approved for the prevention and treatment of venous thromboembolic events, that is, deep vein thrombosis, pulmonary embolism, and superficial vein thrombosis, in acutely ill (including those affected by COVID-19 or cancer patients) and those undergoing surgeries. Since its approval in 2002, the efficacy and safety of fondaparinux is well demonstrated by many clinical studies, establishing the value of fondaparinux in clinical practice. Some of the advantages with fondaparinux are its chemical nature of synthesis, minimal risk of contamination, 100% absolute bioavailability subcutaneously, instant onset of action, a long half-life, direct renal excretion, fewer adverse reactions when compared with direct oral anticoagulants, and being an ideal alternative in conditions where oral anticoagulants are not approved for use or in patients intolerant to low molecular weight heparins (LMWH). In the last decade, the real-world use of fondaparinux has been explored in other conditions such as acute coronary syndromes, bariatric surgery, in patients developing vaccine-induced immune thrombotic thrombocytopenia (VITT) and in pregnant women with heparin-induced thrombocytopenia (HIT), or those intolerant to LMWH. The emerging data from these studies have culminated in recent updates in the guidelines that recommend the use of fondaparinux under various conditions. This paper aims to review the recent data and the subsequent updates in the recommendations of various guidelines on the use of fondaparinux sodium.

Fondaparinux, a clinically approved anticoagulant pentasaccharide for the treatment of thrombotic diseases, displays better efficacy and biosafety than other heparin-based anticoagulant drugs. However, there is no suitable antidote available for fondaparinux to efficiently manage its potential bleeding risks, thereby precluding its widespread use. Herein, we describe a convergent and stereocontrolled approach to efficiently synthesize an aminopentyl-functionalized pentasaccharide, which is further used to prepare fondaparinux-based biotin conjugates and clusters. Biological activity evaluation demonstrates that the anticoagulant activity of the fondaparinux-based biotin conjugate and trimer is, respectively, neutralized by avidin and protamine as effective antidotes. This work suggests that our synthetic biotin conjugate and trimer have potential for the development of neutralizable and safe anticoagulant drugs.

Heparin-induced thrombocytopenia (HIT) is an adverse reaction to heparin products, but not warfarin. HIT usually occurs 5‒10 days after exposure to heparin. Here, we report a case of HIT with multiple thrombotic events and severe thrombocytopenia resulting from intermittent intravenous heparin flushes for maintenance of a newly placed subclavian central venous catheter (CVC) for stem cell transplant. The patient is a woman in her forties with multiple myeloma who presented to the emergency department (ED) with dyspnea, pleuritic-type chest pain, hemoptysis, and worsening left-leg swelling. Heparin had been used to flush the CVC. Her platelet count began dropping approximately one week after insertion. The patient was receiving other medications known to cause thrombocytopenia. She had undergone multiple platelet transfusions. In the ED, her lab results showed thrombocytopenia), anemia; renal insufficiency; and elevated troponin, prothrombin time, and D-dimer levels. Because of the hemoptysis and thrombocytopenia, she initially received platelet transfusion and oxygen. She was found to have deep vein thrombosis of the lower extremity and started a referral to interventional radiology for inferior vena cava (IVC) filter placement. However, further review and consultation of the Benign Hematology service, discussion about the timing of decreased platelet count shortly after CVC placement and heparin administration, and the presence of thrombosis, suggested a high pre-test probability of HIT. Anticoagulation with argatroban was initiated, and IVC filter insertion was canceled. Further workup confirmed HIT diagnosis and saddle pulmonary embolism. During the patient's hospitalization, her platelets continued to improve and reached baseline upon discharge. She was transitioned to fondaparinux at the time of discharge. A few weeks later, she had successful stem cell transplantation. Emergency physicians treating patients with thrombocytopenia receiving heparin, even in small amounts, should consider the possibility of HIT and be familiar with its management.

We describe here the purification and cloning of a codon-optimized form of the snake prothrombin activator ecarin from the saw scaled viper (Echis carinatus) expressed in mammalian cells. Expression of recombinant ecarin (rEcarin) was carried out in human embryonic kidney cells (HEK) cells under conditions for the development and performance of a novel and scalable recombinant snake ecarin to industry standards. Clotting performance of the rEcarin was established in recalcified citrated whole blood, plasma, and fresh whole blood and found to be comparable to native ecarin (N-Ecarin). Furthermore, hemolysis was observed with N-Ecarin at relatively high doses in both recalcified citrated and fresh whole blood, while clotting was not observed with rEcarin, providing an important advantage for the recombinant form. In addition, rEcarin effectively clotted both recalcified citrated whole blood and fresh whole blood containing different anticoagulants including heparin, warfarin, dabigatran, Fondaparinux, rivaroxaban and apixaban, forming firm clots in the blood collection tubes. These results demonstrate that rEcarin efficiently clots normal blood as well as blood spiked with high concentrations of anticoagulants and has great potential as an additive to blood collection tubes to produce high quality serum for analyte analysis in diagnostic medicine.

Aim To study specific features of the parenteral anticoagulant therapy for acute myocardial infarction (MI) in the Russian Federation and to evaluate the consistency of the prescribed parenteral anticoagulant therapy with the effective clinical guidelines.Material and methods REGION-MI, the Russian rEGIstry for acute myOcardial iNfarction, is a multicenter observational study. This registry includes all patients admitted to hospitals with a documented diagnosis of ST-elevation acute MI (STEMI) and non-ST-elevation acute MI (NSTEMI) based on the criteria of the Forth Universal Definition of MI of the European Society of Cardiology. Risk of bleeding was assessed with the Academic Research Consortium for High Bleeding Risk (ARC-HBR) scale, and risk of major bleeding in patients with NSTEMI was additionally assessed with the CRUSADE scale.Results From November 01, 2020 through April 03, 2022, 5025 patients were included into the REGION-MI registry. At primary vascular departments, 70.5% of patients were administered unfractionated heparin (NFH); at regional vascular centers, 37.1 % of patients were administered NFH, 29.6 % enoxaparin, 20,2% NFH in combination with enoxaparin, 6.8 % fondaparinux, 4.2 % NFH in combination with fondaparinux, and 1.9 % nadroparin. At the prehospital stage, NFH was used as an anticoagulant support for the thrombolytic therapy (TLT) in 84% of patients, and low-molecular heparins (LMH) were used in 16 %. At the hospital stage, UFH was administered to 64.4 % of patients, and enoxaparin was administered to 23.9 % of patients. Among the patients who had undergone primary percutaneous coronary intervention (PCI), 40 % received NFH, 25 % enoxaparin, 22 % NFH in combination with enoxaparin, 7 % fondaparinux, and 4 % NFH in combination with fondaparinux. In conservative and invasive tactics of therapy for NSTEMI, NFH was also administered more frequently (43 and 43 %, respectively), followed by (according to frequency of administration) enoxaparin (36 and 34 %, respectively), NFH in combination with enoxaparin (10 and 16 %, respectively), fondaparinux (7 and 6 %, respectively), and NFH in combination with fondaparinux (3 and 1 %, respectively).Conclusion According to the Russian registry of acute MI, REGION-MI, with all strategies for the treatment of MI, parenteral anticoagulants are not prescribed in full consistency with clinical guidelines. The most frequently used parenteral anticoagulant is NFH. Despite the high efficacy and safety of fondaparinux, the frequency of its administration remains unjustifiably low not only in the Russian Federation but also in other countries. The same can be said about the administration of enoxaparin to patients who had received TLT. Attention should be paid to physicians' awareness of recent clinical guidelines, to minimize the prehospital treatment with parenteral anticoagulants, to limit this treatment to the TLT support, and to provide continuity between all stages of medical care.

Background and objectives: Cementless total hip arthroplasty is a common surgical procedure and perioperative thromboprophylaxis is used to prevent deep vein thrombosis or pulmonary embolism. Osseointegration is important for long-term implant survival, and there is no research on the effect of different thromboprophylaxis agents on the process of osseointegration. Materials and Methods: Seventy rats were allocated as follows: Group I (control group), Group II (enoxaparin), Group III (nadroparin), and Group IV (fondaparinux). Ovariectomy was performed on all subjects, followed by the introduction of an intramedullary titanium implant into the femur. Thromboprophylaxis was administered accordingly to each treatment group for 35 days postoperatively. Results: Group I had statistically significantly lower anti-Xa levels compared to treatment groups. Micro-CT analysis showed that nadroparin had lower values compared to control in bone volume (0.12 vs. 0.21, p = 0.01) and percent bone volume (1.46 vs. 1.93, p = 0.047). The pull-out test showed statistically significant differences between the control group (8.81 N) compared to enoxaparin, nadroparin, and fondaparinux groups (4.53 N, 4 N and 4.07 N, respectively). Nadroparin had a lower histological cortical bone tissue and a higher width of fibrous tissue (27.49 μm and 86.9 μm) at the peri-implant area, compared to control (43.2 μm and 39.2 μm), enoxaparin (39.6 μm and 24 μm), and fondaparinux (36.2 μm and 32.7 μm). Conclusions: Short-term administration of enoxaparin, nadroparin, and fondaparinux can reduce the osseointegration of titanium implants, with nadroparin having the most negative effect. These results show that enoxaparin and fondaparinux are preferred to be administered due to a lesser negative impact on the initial implant fixation.

(1) Background: Prion-like transcellular spreading of tau pathology in Alzheimer's disease (AD) is mediated by tau binding to the cell-surface glycan heparan sulfate (HS). However, the structural determinants for tau-HS interaction are not well understood. (2) Methods and Results: Binding-site mapping using NMR showed two major binding regions in full-length tau responsible for heparin interaction. Thus, two tau constructs, tau PRR2* and tau R2*, were designed to investigate the molecular details at the tau-heparin binding interface. The 2D 1H-15N HSQC of tau PRR2* and tau R2* lacked dispersion, which is characteristic for intrinsically disordered proteins. NMR titration of Arixtra into 15N-labeled tau R2* induced large chemical shift perturbations (CSPs) in 275VQIINK280 and downstream residues K281-D283, in which L282 and I278 displayed the largest shifts. NMR titration of Arixtra into 15N-labeled tau PRR2* induced the largest CSPs for residue R209 followed by residues S210 and R211. Residue-based CSP fitting showed that tau PRR2*-Arixtra interaction had a much stronger binding affinity (0.37-0.67 mM) than that of tau R2*-Arixtra (1.90-5.12 mM) interaction. (3) Conclusions: Our results suggested that PRR2 is a crucial domain for tau-heparin and tau-HS interaction.

Objective Venous thromboembolism (VTE) is a common cancer complication. Patients with cancer have a high risk of recurrent VTE and bleeding. We analyzed the effectiveness of VTE treatment via subcutaneous fondaparinux injection for patients with and without cancer. Methods and Materials This study included 260 inpatients who had received fondaparinux therapy. Fondaparinux's therapeutic effect was quantitatively and qualitatively evaluated by imaging tests. To quantitatively evaluate the deep vein thrombosis (DVT) clot burden of the lower limbs, we calculated the quantitative ultrasound thrombosis (QUT) score, which was devised by our institution. Results There were 80 and 180 patients with and without cancer, respectively. The QUT score significantly reduced after treatment in both groups (cancer: 6.70±4.37 vs. 4.19±4.17, p<0.001; noncancer: 7.08±4.37 vs. 4.17±3.94, p<0.001). The changes in the QUT score showed no significant difference between the 2 groups (cancer: 2.23±3.09; noncancer: 3.04±3.45, p=0.06). In addition, the quantitative evaluation of pulmonary thromboembolism (PTE) after treatment showed that PTE decreased or disappeared in 38/40 patients (95.0%) in the cancer group and 55/63 patients (87.3%) in the noncancer group, indicating no significant difference in the improvement rate between the groups. Conclusion Fondaparinux was effective for VTE both in patients with and without cancer, with no significant differences in the changes in the QUT score. However, the change in the QUT score was smaller in patients with cancer than in those without cancer, suggesting that the efficacy of fondaparinux might be diminished in patients with cancer.

In this article, 34 anticoagulant drugs were screened in silico against the main protease (Mpro) of SARS-CoV-2 using molecular docking tools. Idraparinux, fondaparinux, eptifibatide, heparin, and ticagrelor demonstrated the highest binding affinities towards SARS-CoV-2 Mpro. A molecular dynamics study at 200 ns was also carried out for the most promising anticoagulants to provide insights into the dynamic and thermodynamic properties of promising compounds. Moreover, a quantum mechanical study was also conducted which helped us to attest to some of the molecular docking and dynamics findings. A biological evaluation (in vitro) of the most promising compounds was also performed by carrying out the MTT cytotoxicity assay and the crystal violet assay in order to assess inhibitory concentration 50 (IC50). It is worth noting that ticagrelor displayed the highest intrinsic potential for the inhibition of SARS-CoV-2 with an IC50 value of 5.60 µM and a safety index of 25.33. In addition, fondaparinux sodium and dabigatran showed promising inhibitory activities with IC50 values of 8.60 and 9.40 µM, respectively, and demonstrated safety indexes of 17.60 and 15.10, respectively. Moreover, the inhibitory potential of the SARS-CoV-2 Mpro enzyme was investigated by utilizing the SARS-CoV-2 Mpro assay and using tipranavir as a reference standard. Interestingly, promising SARS-CoV-2 Mpro inhibitory potential was attained for fondaparinux sodium with an IC50 value of 2.36 µM, surpassing the reference tipranavir (IC50 = 7.38 µM) by more than three-fold. Furthermore, highly eligible SARS-CoV-2 Mpro inhibitory potential was attained for dabigatran with an IC50 value of 10.59 µM. Finally, an SAR was discussed, counting on the findings of both in vitro and in silico approaches.

This case report aims to describe the first report of bilateral aseptic cavernous sinus thrombosis (CST) with a recent history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. A 50-year-old woman presented with bilateral proptosis, decreased vision, and ophthalmoplegia 16 days following CoronaVac® vaccine. The visual acuity of the left eye was 20/150, while the right eye was no light perception with a hyperemic optic nerve head. She had a history of hyperthyroidism and currently on warfarin consumption. Laboratory results depicted elevated free T4, free T3, international normalized ratio, and low protein S and C. Magnetic resonance imaging showed bilateral CST, and high-dose methylprednisolone along with fondaparinux was given. The symptoms were significantly resolved, with the visual acuity of the left eye being improved to 20/20 but not the right eye. Bilateral CST has not been previously reported following inactivated SARS-CoV-2 vaccination. The underlying systemic conditions should be taken into consideration for the possibility of the inactivated SARS-CoV-2 vaccine-related event.

A chemoenzymatic approach, mimicking the biosynthetic pathway of heparin and heparan sulfate (HS), has been well developed to prepare a series of structurally well-defined heparin oligosaccharides with excellent anticoagulant activity in good overall yields. The current chemoenzymatic synthesis typically begins with an unnatural glycosyl acceptor, p-nitrophenyl glucuronide (GlcA-PNP), which is convenient for detection recovery and purification, although it affords heparin molecules with undesirable structure characteristics. Herein, we describe a facile chemoenzymatic strategy assisted by the specific cleavage of heparinase III for the highly efficient synthesis of an unmodified heparin heptasaccharide which demonstrated potent anticoagulant activity in vitro and commensurate pharmacokinetic profiles with fondaparinux. This successful generic strategy is applicable to the scalable synthesis of diverse HS/heparin molecules with completely natural structural features as promising therapeutic agents.

Background: Venous thromboembolism (VTE) remains one of the leading causes of maternal morbidity and mortality, with postpartum period carrying the greatest risk. Perinatal thromboprophylaxis is often administered based on risk-factor assessment. Low molecular weight heparin has a proven safety profile in the obstetrics population, however, its porcine-derived content may lead to reduced uptake amongst certain religious groups. We aimed to evaluate the safety of fondaparinux as an alternative postpartum thromboprophylaxis. Methods: We conducted a prospective, single arm, open label study from September 2017 until March 2018. Women who fulfilled the criteria for post natal thromboprophylaxis based on the 2015 RCOG guidelines were recruited. Each patient received subcutaneous injection of Fondaparinux, 2.5 mg daily for 10 days. A telephone interview was conducted on day 10 post delivery. Each woman was subsequently reviewed in the outpatient clinic 6 weeks postpartum. The primary outcome measure was occurrence of pulmonary embolism or deep vein thrombosis suggestive by clinical symptoms and assessment. Secondary outcome measures were allergic reaction and bleeding tendency such as secondary post-partum haemorrhage, spinal site bleeding and wound haematoma. Allergic reaction and bleeding tendency in neonates were also recorded. Results: Sixty women were included in the analysis. There were no VTE cases amongst our cohort. No major bleeding was recorded. Two patients (3.3%) had wound haematoma, one of which occurred 3 weeks post delivery. No adverse effect in neonates was noted. Conclusion: Fondaparinux is a safe alternative thromboprophylaxis for postpartum women.

Venous thromboembolism (VTE) is a common complication in patients hospitalized for acute medical illnesses. Therefore, medical inpatients require a careful VTE and bleeding risk assessment to drive optimal strategies for VTE prevention. Low molecular weight heparin and fondaparinux have long been used for inhospital prophylaxis for patients at increased risk of VTE. The selection of patients who require post-discharge prophylaxis, and the role of direct oral anticoagulants remain debated. New molecules currently under development may contribute to improve the risk benefit of VTE prevention in this setting.

Limited evidence exists to guide the management of recurrent thrombosis occurring despite therapeutic anticoagulation in patients with thrombotic antiphospholipid syndrome (APS). In this case series, fondaparinux, with or without an antiplatelet agent, provided an effective and safe option in three patients with thrombotic APS, all two triple and one single positive for antiphospholipid antibodies, who had recurrent venous and/or arterial thromboembolism. Rituximab was also used in all patients. Recurrent events occurred despite therapeutic anticoagulation, including at high-intensity, with warfarin and subsequent low-molecular-weight heparin. There were no major bleeding events. Adjunctive therapies used for thrombosis included catheter-directed thrombolysis and rituximab.

Host cell proteases such as TMPRSS2 are critical determinants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) tropism and pathogenesis. Here, we show that antithrombin (AT), an endogenous serine protease inhibitor regulating coagulation, is a broad-spectrum inhibitor of coronavirus infection. Molecular docking and enzyme activity assays demonstrate that AT binds and inhibits TMPRSS2, a serine protease that primes the Spike proteins of coronaviruses for subsequent fusion. Consequently, AT blocks entry driven by the Spikes of SARS-CoV, MERS-CoV, hCoV-229E, SARS-CoV-2 and its variants of concern including Omicron, and suppresses lung cell infection with genuine SARS-CoV-2. Thus, AT is an endogenous inhibitor of SARS-CoV-2 that may be involved in COVID-19 pathogenesis. We further demonstrate that activation of AT by anticoagulants, such as heparin or fondaparinux, increases the anti-TMPRSS2 and anti-SARS-CoV-2 activity of AT, suggesting that repurposing of native and activated AT for COVID-19 treatment should be explored.

Anticoagulation is the cornerstone of cancer-associated VTE treatment, including vitamin K antagonists (VKA), unfractionated heparin (UFH), fondaparinux, low-molecular-weight heparins (LMWH) and direct oral anticoagulants (DOACs). The goals of anticoagulant therapy in cancer patients with cancer-associated thrombosis (CAT) are to improve symptoms, reduce risk of recurrent VTE or fatal pulmonary embolism (PE), and decrease the risk of post-thrombotic syndrome (PTS) and chronic thromboembolic pulmonary hypertension. Although LMWH have been the standard of care for a long time for VTE treatment in cancer patients, showing superiority over the classic VKA, in the recent years the landscape of anticoagulant therapy has significantly changed with the inclusion of DOACs in this population.

The optimal anticoagulation strategy for venous thromboembolism (VTE) prevention among COVID-19 patients, hospitalized or in the community setting, is still challenging and largely based on real-world evidence.

Hospital-associated venous thromboembolism (HA-VTE) is a major cause of morbidity and mortality and is internationally recognized as a significant patient safety issue. While cirrhosis was traditionally considered to predispose to bleeding, these patients are also at an increased risk of VTE, with an associated increase in mortality. Hospitalization rates of patients with cirrhosis are increasing, and decisions regarding thromboprophylaxis are complex due to the uncertain balance between thrombosis and bleeding risk. This is further accentuated by derangements of hemostasis in patients with cirrhosis that are often considered contraindications to pharmacological thromboprophylaxis. Due to the strict inclusion and exclusion criteria of seminal studies of VTE risk assessment and thromboprophylaxis, there is limited data to guide decision making in this patient group. This guidance document reviews the incidence and risk factors for HA-VTE in patients with cirrhosis, outlines evidence to inform the use of thromboprophylaxis, and provides pragmatic recommendations on VTE prevention for hospitalized patients with cirrhosis. In brief, in hospitalized patients with cirrhosis: We suggest inclusion of portal vein thrombosis as a distinct clinically important endpoint for future studies. We recommend against the use of thrombocytopenia and/or prolongation of prothrombin time/international normalized ratio as absolute contraindications to anticoagulant thromboprophylaxis. We suggest anticoagulant thromboprophylaxis in line with local protocols and suggest low molecular weight heparin (LMWH) or fondaparinux over unfractionated heparin (UFH). In renal impairment, we suggest LMWH over UFH. For critically ill patients, we suggest case-by-case consideration of thromboprophylaxis. We recommend research to refine VTE risk stratification, and to establish the optimal dosing and duration of thromboprophylaxis.

A male patient aged 50 years, presented with a swelling in the right leg which had occurred five days before hospital admission. This was associated with pain in the swollen leg. The patient had a history of femoral double lumen catheter (DLC) insertion for hemodialysis. On physical examination, Wong Baker's scale was 3, Wells' score was 3, and the patient had edematous, red, and warm right lower extremity. Laboratory results showed anemia (Hb 11.4 g/dl), leukocytosis (27.99 x 103/ul), increased blood urea nitrogen (BUN) (60 mg/dl), increased serum creatinine (9.93 mg/dl), hyperkalemia (6 mmol/l), urine leukocytes +3; 15-20/hpf. Lower extremity ultrasound revealed diffuse deep vein thrombosis (DVT). After the diagnosis of DVT, the patient was treated with fondaparinux injection and warfarin as an anticoagulant for six days. Our results show that treatment was effective in reducing swelling and pain in the right leg, that disappeared after a three months´ treatment.