Fondaparinux Sodium: Recent Advances in the Management of Thrombosis.

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.

Anticoagulants as Potential SARS-CoV-2 Mpro Inhibitors for COVID-19 Patients: In Vitro, Molecular Docking, Molecular Dynamics, DFT, and SAR Studies.

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.

When Will Fondaparinux Induce Thrombocytopenia?

The pentasaccharide Fondaparinux, a synthetic selective factor Xa inhibitor, is one of the safest anticoagulants in the heparin family that is recommended as an alternative drug for patients with hypersensitivity to other drugs such as heparin-induced thrombocytopenia (HIT). However, some observations of Fondaparinux-induced thrombocytopenia (FIT) have been reported while others claimed that FIT does not occur in patients with fondaparinux therapy, indicating that the mechanism of FIT remains controversial. Here, we utilized different methodologies including dynamic light scattering, immunosorbent and platelet aggregation assays, confocal laser scanning microscopy, and flow cytometry to gain insights into FIT. We found that at a certain concentration, Fondaparinux formed sufficient large and stable complexes with PF4 that facilitated binding of the HIT-like monoclonal KKO antibody and enhanced platelet aggregation and activation. We proposed a model to describe the role of Fondaparinux concentration in the formation of complexes with platelet factor 4 and how it promotes the binding of KKO. Our results clarify controversial observations of FIT in patients as each contains a dissimilar PF4:Fondaparinux concentration ratio.

The interaction between anti-PF4 antibodies and anticoagulants in vaccine-induced thrombotic thrombocytopenia.

Life-threatening thrombotic events at unusual sites have been reported after vector-based vaccinations against severe acute respiratory syndrome coronavirus 2. This phenomenon is now termed vaccine-induced immune thrombotic thrombocytopenia (VITT). The pathophysiology of VITT is similar to that of heparin-induced thrombocytopenia (HIT) and is associated with platelet-activating antibodies (Abs) against platelet factor 4 (PF4). Therefore, current guidelines suggest nonheparin anticoagulants to treat VITT patients. In this study, we investigated the interactions of heparin, danaparoid, fondaparinux, and argatroban with VITT-Ab/PF4 complexes using an ex vivo model for thrombus formation as well as in vitro assays to analyze Ab binding and platelet activation. We found that immunoglobulin Gs (IgGs) from VITT patients induce increased adherent platelets/thrombus formation in comparison with IgGs from healthy controls. In this ex vivo flow-based model, the procoagulant activity of VITT IgGs was effectively inhibited with danaparoid and argatroban but also by heparin. Interestingly, heparin and danaparoid not only inhibited IgG binding to PF4 but were also able to effectively dissociate the preformed PF4/IgG complexes. Fondaparinux reduced the in vitro generation of procoagulant platelets and thrombus formation; however, it did not affect platelet aggregation. In contrast, argatroban showed no effect on procoagulant platelets and aggregation but significantly inhibited VITT-mediated thrombus formation. Taken together, our data indicate that negatively charged anticoagulants can disrupt VITT-Ab/PF4 interactions, which might serve as an approach to reduce Ab-mediated complications in VITT. Our results should be confirmed, however, in a clinical setting before a recommendation regarding the selection of anticoagulants in VITT patients could be made.

Heparin and SARS-CoV-2: Multiple Pathophysiological Links.

Low molecular weight heparin, enoxaparin, has been one of most used drugs to fight the SARS-CoV-2 pandemic. Pharmacological properties of heparin recognize its specific ability, as with other oligosaccharides and glycosaminoglycan, to bind several types of viruses during their pass through the extracellular matrix of the respiratory tract, as well as its anticoagulant activity to prevent venous thromboembolism. Antithrombotic actions of enoxaparin have been testified both for inpatients with COVID-19 in regular ward and for inpatients in Intensive Care Units (ICUs). Prophylactic doses seem to be able to prevent venous thromboembolism (VTE) in inpatients in the regular ward, while intermediate or therapeutic doses have been frequently adopted for inpatients with COVID-19 in ICU. On the other hand, although we reported several useful actions of heparin for inpatients with COVID-19, an increased rate of bleeding has been recorded, and it may be related to several conditions such as underlying diseases with increased risks of bleeding, increased doses or prolonged administration of heparin, personal trend to bleed, and so on.

Using Nonheparin Anticoagulant to Treat a Near-Fatal Case With Multiple Venous Thrombotic Lesions During ChAdOx1 nCoV-19 Vaccination-Related Vaccine-Induced Immune Thrombotic Thrombocytopenia.

OBJECTIVES: To describe the successful recovery from multiple and life-threatening venous thrombosis after ChAdOx1 nCoV-19 vaccination. DESIGN: Case report. SETTING: University Hospital. PATIENT: Few days after the first dose of the ChAdOx1 nCoV-19 vaccine, a 21-year-old woman experienced massive thrombosis in the deep and superficial cerebral veins together with seizures, neurologic focal deficit, and thrombocytopenia. In the neurointensive care unit, her condition worsened despite early decompressive craniectomy. She developed bilateral segmental pulmonary embolism, left hepatic, and left external iliac venous thrombosis. INTERVENTION: Argatroban (0.5-2.2 µg/kg/min) and high-dose IV immunoglobulin (1 g/kg/d for 2 consecutive days) were initiated on day 6 after admission. With these therapies, there was a gradual resolution of multiple sites of venous thrombosis, and platelet count returned to normal. The patient left the ICU with full consciousness, expressive aphasia, and right hemiparesis. CONCLUSIONS: This case of vaccine-induced immune thrombotic thrombocytopenia shows that a good outcome can be obtained even with multiple and life-threatening venous thrombotic lesions. Argatroban and high-dose IV immunoglobulin along with management of severe cerebral venous thrombosis played a major role in this epilogue.

Anticoagulation for COVID-19 Patients: A Bird's-Eye View.

Coronavirus disease 2019 (COVID-19) is a systemic disease that can be life-threatening involving immune and inflammatory responses, and that can result in potentially lethal complications, including venous thrombo-embolism (VTE). Forming an integrative approach to thrombo-prophylaxis and coagulation treatment for COVID-19 patients ensues. We aim at reviewing the literature for anticoagulation in the setting of COVID-19 infection to provide a summary on anticoagulation for this patient population. COVID-19 infection is associated with a state of continuous inflammation, which results in macrophage activation syndrome and an increased rate of thrombosis. Risk assessment models to predict the risk of thrombosis in critically ill patients have not yet been validated. Currently published guidelines suggest the use of prophylactic intensity over intermediate intensity or therapeutic intensity anticoagulant for patients with critical illness or acute illness related to COVID-19 infection. Critically ill COVID-19 patients who are diagnosed with acute VTE are considered to have a provoking factor, and, therefore, treatment duration should be at least 3 months. Patients with proximal deep venous thrombosis or pulmonary embolism should receive parenteral over oral anticoagulants with low-molecular-weight heparin or fondaparinux preferred over unfractionated heparin. In patients with impending hemodynamic compromise due to PE, and who are not at increased risk for bleeding, reperfusion may be necessary. Internists should remain updated on new emerging evidence regarding anticoagulation for COVID-19 patients. Awaiting these findings, we invite internists to perform individualized decisions that are unique for every patient and to base them on clinical judgment for risk assessment.

Edoxaban for the treatment of pulmonary embolism in hospitalized COVID-19 patients.

PURPOSE: We aimed to investigate the clinical performance of edoxaban for the treatment of pulmonary embolism (PE) in hospitalized COVID-19 patients. METHODS: We conducted a retrospective analysis selecting hospitalized patients with COVID-19 admitted to our Institution from 20 May 2020 to 20 November 2020 with computer tomography (CT) detected PE at admission, treated with edoxaban after initial parenteral therapy. Clinical outcomes were compared between patients with and without ARDS at admission and between those with and without CT confirmed PE resolution. RESULTS: 50 patients were included. Mean follow-up was 42.5 ± 10 days. No baseline differences were found between patients with ARDS (30%) and those without ARDS at admission. Patients with PE resolution (84%) were younger (P = 0.03), had a shorter duration of fondaparinux therapy (9.9 ± 3.8 vs 15.8 ± 7.5 days; P = 0.0015) and length of hospitalization (36 ± 8 vs 46 ± 9 days: P = 0.0023) compared with those without PE resolution. 2 patients experienced major bleedings. At multivariate analysis the time to edoxaban switch was the only predictor of the PE resolution (HR: 0.92; 95% C.I. 0.86 to 0.99). CONCLUSION: Edoxaban was an effective and safe treatment for acute PE in COVID-19 setting.

COVID-19 vaccine-induced immune thrombotic thrombocytopenia: A review of the potential mechanisms and proposed management.

With over 600 million coronavirus (COVID-19) vaccine doses administered globally, adverse events are constantly monitored. Recently however, reports of thrombosis and thrombocytopenia following vaccination with the ChAdOx1 nCoV-19 vaccine have emerged. This paper aims to review the available literature and guidelines pertaining to vaccine-induced immune thrombotic thrombocytopenia (VITT) and the proposed guidelines, while offering a potential approach that unifies the available evidence. While the risk of VITT remains extremely low and the benefits outweigh the risks, experimental studies are needed to clarify the pathophysiology behind VITT and possibly decrease the risk of thrombosis and other adverse events occurring. However, treatment should not be delayed in suspected cases, and IV immunoglobulin and non-heparin anticoagulation should be initiated.

Incidence of deep vein thrombosis through an ultrasound surveillance protocol in patients with COVID-19 pneumonia in non-ICU setting: A multicenter prospective study.

OBJECTIVE: The aim of this study was to assess the incidence of deep vein thrombosis (DVT) of the lower limbs, using serial compression ultrasound (CUS) surveillance, in acutely ill patients with COVID-19 pneumonia admitted to a non-ICU setting. METHODS: Multicenter, prospective study of patients with COVID-19 pneumonia admitted to Internal Medicine units. All patients were screened for DVT of the lower limbs with serial CUS. Anticoagulation was defined as: low dose (enoxaparin 20-40 mg/day or fondaparinux 1.5-2.5 mg/day); intermediate dose (enoxaparin 60-80 mg/day); high dose (enoxaparin 120-160 mg or fondaparinux 5-10 mg/day or oral anticoagulation). The primary end-point of the study was the diagnosis of DVT by CUS. RESULTS: Over a two-month period, 227 consecutive patients with moderate-severe COVID-19 pneumonia were enrolled. The incidence of DVT was 13.7% (6.2% proximal, 7.5% distal), mostly asymptomatic. All patients received anticoagulation (enoxaparin 95.6%) at the following doses: low 57.3%, intermediate 22.9%, high 19.8%. Patients with and without DVT had similar characteristics, and no difference in anticoagulant regimen was observed. DVT patients were older (mean 77±9.6 vs 71±13.1 years; p = 0.042) and had higher peak D-dimer levels (5403 vs 1723 ng/mL; p = 0.004). At ROC analysis peak D-dimer level >2000 ng/mL (AUC 0.703; 95% CI 0.572-0.834; p = 0.004) was the most accurate cut-off value able to predict DVT (RR 3.74; 95%CI 1.27-10, p = 0.016). CONCLUSIONS: The incidence of DVT in acutely ill patients with COVID-19 pneumonia is relevant. A surveillance protocol by serial CUS of the lower limbs is useful to timely identify DVT that would go otherwise largely undetected.

Thrombin generation in patients with COVID-19 with and without thromboprophylaxis.

OBJECTIVES: Thrombin generation (TG) with and without thrombomodulin (TM) was evaluated in COVID-19 patients with different disease severity and thromboprophylaxis regimen, in order to understand the prothrombotic profile. METHODS: We enrolled consecutive patients with confirmed diagnosis of COVID-19 admitted to Medical Departments (MD) or Intensive Care Units (ICU), and 54 healthy controls. RESULTS: Eighty-nine patients were included (mean age 60.4±16.1 years, 68.5% male); 33.7% admitted to ICU. Twenty-four patients (26.9%) were enrolled before thromboprophylaxis administration; 45 patients (50.6%) received standard and 20 (22.5%) intermediate sub-therapeutic dose thromboprophylaxis. Overall, patients with COVID-19 showed a TG profile comparable to that of healthy subjects (i.e. comparable peak height, endogenous thrombin potential [ETP] with and without TM). The only exception was lag time and time to peak, prolonged in COVID-19 patients vs. controls. MD patients showed a similar TG profile to healthy controls, and ICU patients showed significantly decrease ETP (p=0.030) compared to MD. As for thromboprophylaxis, TG profile was significantly increased in COVID-19 patients without thromboprophylaxis vs. controls and vs. those with thromboprophylaxis. In this latter group, ETP inhibition was significantly decreased (p=0.0003) and positively correlated with anti-Xa activity (r=0.49, p=0.0017). However, patients with thromboprophylaxis had similar TG profile vs. controls. Intermediate dose thromboprophylaxis more effectively inhibited TG in severe COVID-19 patients by increasing ETP inhibition via ETP with TM reduction vs. standard dose. CONCLUSIONS: COVID-19 patients showed increased TG at diagnosis. Standard thromboprophylaxis reduced TG to levels of healthy controls. Intermediate sub-therapeutic thromboprophylaxis more effectively inhibited TG by decreasing ETP with TM.

Fondaparinux Use in Patients With COVID-19: A Preliminary Multicenter Real-World Experience.

The use of heparin has been shown to decrease the mortality in hospitalized patients with severe COVID-19. The aim of our study was to evaluate the clinical impact of venous thromboembolism prophylaxis with fondaparinux versus enoxaparin among 100 hospitalized COVID-19 patients. The incidence of pulmonary embolism, deep venous thrombosis, major bleeding (MB), clinically relevant non-MB, acute respiratory distress syndrome, and in-hospital mortality was compared between patients on fondaparinux versus enoxaparin therapy. The 2 groups were homogeneous for demographic, laboratory, and clinical characteristics. In a median follow-up of 28 (IQR: 12-45) days, no statistically significant difference in venous thromboembolism (14.5% vs. 5.3%; P = 0.20), MB and clinically relevant non-MB (3.2% vs. 5.3%, P = 0.76), ARDS (17.7% vs. 15.8%; P = 0.83), and in-hospital mortality (9.7% vs. 10.5%; P = 0.97) has been shown between the enoxaparin group versus the fondaparinux group. Our preliminary results support the hypothesis of a safe and effective use of fondaparinux among patients with COVID-19 hospitalized in internal medicine units.

Venous thromboembolism in COVID-19: systematic review of reported risks and current guidelines.

AIMS OF THE STUDY: Many centres have noticed a high number of venous thromboembolism (VTE) events among critically ill inpatients with COVID-19 pneumonia. The aims of this study were (1) to summarise the reported risk of VTE associated with COVID-19 infections and (2) to summarise guidance documents on thromboprophylaxis in COVID-19 patients, in a systematic review. METHODS: We systematically searched for peer-reviewed evidence on the risk of VTE in patients with COVID-19, in PubMed, Embase and Twitter, and for guidelines or guidance documents for thromboprophylaxis, from international or national societies relevant to the field of thrombosis and haemostasis, up to April 30 2020. RESULTS: We found 11 studies (1 clinical trial, 7 retrospective cohorts and 3 prospective cohorts), which included a range of 16 to 388 in patients with COVID-19 (total of 1369 inpatients). The diagnoses of COVID-19 and VTE were of high quality, but the follow-up was often unclear. Most studies reported universal in-hospital thromboprophylaxis. Among all inpatients and among intensive care unit (ICU) inpatients with COVID-19, reported risks of VTE were 4.4–8.2% (three studies) and 0–35.3% (six studies), respectively. Two studies at least partially screened for VTE in ICU inpatients with COVID-19, and found risks of 24.7–53.8%. We found 12 guidelines for thromboprophylaxis of COVID-19 patients. The majority suggested universal pharmacological thromboprophylaxis in all COVID-19 inpatients, but there was heterogeneity in the suggested intensity of thromboprophylaxis: seven advised considering intensified doses of heparin according to the clinical or biological severity of the disease, especially in the ICU setting. CONCLUSIONS: Venous thromboembolism very commonly complicates the clinical course of inpatients with COVID-19, despite thromboprophylaxis. The risk appears highest among critically ill inpatients. We found no estimates of risks among outpatients. Many questions remain unresolved, as delineated by the heterogeneity of national and international guidelines. This situation calls for fast randomised clinical trials, comparing different schemes of thromboprophylaxis in COVID-19 inpatients.

Incidence of deep vein thrombosis among non-ICU patients hospitalized for COVID-19 despite pharmacological thromboprophylaxis.

BACKGROUND: A remarkably high incidence of venous thromboembolism (VTE) has been reported among critically ill patients with COVID-19 assisted in the intensive care unit (ICU). However, VTE burden among non-ICU patients hospitalized for COVID-19 that receive guideline-recommended thromboprophylaxis is unknown. OBJECTIVES: To determine the incidence of VTE among non-ICU patients hospitalized for COVID-19 that receive pharmacological thromboprophylaxis. METHODS: We performed a systematic screening for the diagnosis of deep vein thrombosis (DVT) by lower limb vein compression ultrasonography (CUS) in consecutive non-ICU patients hospitalized for COVID-19, independent of the presence of signs or symptoms of DVT. All patients were receiving pharmacological thromboprophylaxis with either enoxaparin or fondaparinux. RESULTS: The population that we screened consisted of 84 consecutive patients, with a mean age of 67.6 ± 13.5 years and a mean Padua Prediction Score of 5.1 ± 1.6. Seventy-two patients (85.7%) had respiratory insufficiency, required oxygen supplementation, and had reduced mobility or were bedridden. In this cohort, we found 10 cases of DVT, with an incidence of 11.9% (95% confidence interval [CI] 4.98-18.82). Of these, 2 were proximal DVT (incidence rate 2.4%, 95% CI -0.87-5.67) and 8 were distal DVT (incidence rate 9.5%, 95% CI 3.23-5.77). Significant differences between subjects with and without DVT were D-dimer > 3000 µg/L (P < .05), current or previous cancer (P < .05), and need of high flow nasal oxygen therapy and/or non-invasive ventilation (P < .01). CONCLUSIONS: DVT may occur among non-ICU patients hospitalized for COVID-19, despite guideline-recommended thromboprophylaxis.