Thrombotic events in severe FXII deficiency in comparison with unaffected family members during a long observation period

Factor XI/XIa inhibitors: a potential solution to anticoagulation dilemmas

INTRODUCTION

Antithrombotic therapy is the cornerstone of stroke prevention, but standard of care therapies are underutilized and use is limited by bleeding rates, drug interactions, and renal elimination. Factor XI/XIa (FXI/XIa) inhibitors are a novel anticoagulation class that purportedly target thrombosis more than hemostasis, thereby raising the hope of reducing bleeding consequences while maintaining efficacy.

AREAS COVERED

This review covers the mechanistic rationale for FXI/XIa inhibitors, describes the various molecule sub-classes, addresses barriers to current anticoagulation use, and reviews clinical trial data to date for this novel class of anticoagulants.

EXPERT OPINION

FXI/XIa inhibitors offer several advantages over DOACs in stroke prevention such as reduced bleeding, fewer drug interactions, and less renal elimination. However, clinical trials must demonstrate non-inferior efficacy and improved safety compared to DOACs. Additional barriers to use will include cost, inadequacy of antidotes, and overall anticoagulant underutilization. The potential for a small molecule or monoclonal antibody to reach the clinic is very high.

Synthesis, Biological Evaluation and Reversal of Sulfonated Di- and Triblock Copolymers as Novel Parenteral Anticoagulants

Despite targeting different coagulation cascade sites, all Food and Drug Administration-approved anticoagulants present an elevated risk of bleeding, including potentially life-threatening intracranial hemorrhage. Existing studies have not thoroughly investigated the efficacy and safety of sulfonate polymers in animal models and fully elucidate the precise mechanisms by which these polymers act. The activity and safety of sulfonated di- and triblock copolymers containing poly(sodium styrenesulfonate) (PSSS), poly(sodium 2-acrylamido-2-methylpropanesulfonate) (PAMPS), poly(ethylene glycol) (PEG), poly(sodium methacrylate) (PMAAS), poly(acrylic acid) (PAA), and poly(sodium 11-acrylamidoundecanoate) (PAaU) blocks are synthesized and assessed. PSSS-based copolymers exhibit greater anticoagulant activity than PAMPS-based ones. Their activity is mainly affected by the total concentration of sulfonate groups and molecular weight. PEG-containing copolymers demonstrate a better safety profile than PAA-containing ones. The selected copolymer PEG47-PSSS32 exhibits potent anticoagulant activity in rodents after subcutaneous and intravenous administration. Heparin Binding Copolymer (HBC) completely reverses the anticoagulant activity of polymer in rat and human plasma. No interaction with platelets is observed. Selected copolymer targets mainly factor XII and fibrinogen, and to a lesser extent factors X, IX, VIII, and II, suggesting potential application in blood-contacting biomaterials for anticoagulation purposes. Further studies are needed to explore its therapeutic applications fully.

Factor XI Inhibitors: perspectives in primary and secondary prevention of ischemic stroke

Stroke is one of the most common causes of mortality and disability worldwide. Antithrombotic therapy represents the mainstay in primary and secondary prevention, both in cardioembolic and non-cardioembolic stroke. Particularly, direct oral anticoagulants play a crucial role in atrial fibrillation, the most common cause of cardioembolic stroke, whereas single or dual antiplatelet therapy is preferred in non-cardioembolic stroke. However, the limitations related to the residual risk of cardioembolic or cerebrovascular events, and the risk of major bleeding, still represent unmet medical needs. To overcome them, new drugs inhibiting Factor XI (FXI) and Factor XII have been proposed, with a selective inhibition of contact pathway of coagulation, delineating a new anticoagulant approach. This review provides a summary of the currently available evidence and future perspectives on FXI inhibitors, that can represent an additional therapeutic option in the primary and secondary prevention of cardioembolic and non-cardioembolic ischemic stroke, also in challenging therapeutic contexts.

A single-center study of patients with rare isolated acquired clotting factor deficiencies other than acquired hemophilia A

Background

Isolated acquired clotting factor deficiencies (ACFDs) are mainly caused by the existence of anti-factor antibodies or adsorption of clotting factors onto substances such as amyloid. Besides acquired factor (F)VIII deficiency (acquired hemophilia A), the remaining factor deficiencies are rare and diverse, posing challenges in both diagnosis and management.

Objectives

To describe different features of isolated ACFDs to improve our understanding of these diseases and provide practical recommendations for their management.

Methods

Clinical characteristics of patients with isolated acquired FII, FV, FIX, FX, FXI, FXII, FXIII, and von Willebrand factor deficiencies were collected from a single center between July 1997 and December 2021 and analyzed retrospectively.

Results

A total of 54 rare isolated ACFD patients were enrolled in our study, mainly including 20 acquired FV deficiency patients and 16 acquired FX deficiency patients. The median age at diagnosis of all rare isolated ACFD patients was 55 years. The median time to diagnose all rare isolated ACFD patients was 60 days. Ten (18.5%) rare isolated ACFD patients had no bleeding and 2 (3.7%) rare isolated ACFD patients showed venous thromboembolism. Hemostatic treatment was applied to 41 (41/54; 75.9%) rare isolated ACFD patients. Thirty-seven (68.5%) rare isolated ACFD patients received immunosuppressive therapy, and 10 (18.5%) rare isolated ACFD patients received chemotherapy targeting primary diseases. Twenty-two (61.9%) rare isolated ACFD patients achieved complete remission, and 9 (21.4%) rare isolated ACFD patients died.

Conclusion

Rare isolated ACFDs are underestimated, associated with delayed diagnosis, and lack effective therapy. Clinicians should raise awareness for recognizing and managing rare isolated ACFD patients to avoid morbidity and mortality.

Polyphosphate as an antithrombotic target and hemostatic agent

Polyphosphate (PolyP) is a polymer comprised of linear phosphate units connected by phosphate anhydride bonds. PolyP exists in a diverse range of eukaryotes and prokaryotes with varied chain lengths ranging from six to thousands of phosphate units. Upon activation, human platelets and neutrophils release short-chain PolyP, along with other components, to initiate the coagulation pathway. Long-chain PolyP derived from cellular or bacterial organelles exhibits higher proinflammatory and procoagulant effects compared to short-chain PolyP. Notably, PolyP has been identified as a low-hemorrhagic antithrombotic target since neutralizing plasma PolyP suppresses the thrombotic process without impairing the hemostatic functions. As an inorganic polymer without uniform steric configuration, PolyP is typically targeted by cationic polymers or recombinant polyphosphatases rather than conventional antibodies, small-molecule compounds, or peptides. Additionally, because of its procoagulant property, PolyP has been incorporated in wound-dressing materials to facilitate blood hemostasis. This review summarizes current studies on PolyP as a low-hemorrhagic antithrombotic target and the development of hemostatic materials based on PolyP.

Friend or Foe: Factor XII Deficiency Discovered Incidentally during Management of NSTEMI

Factor XII (FXII) deficiency is a rare coagulopathy that typically goes undiagnosed due to the lack of abnormal bleeding or thrombosis. However, the accompanying prolonged activated partial thromboplastin time (aPTT) can create difficulties with maintaining therapeutic anticoagulation in the setting of acute coronary syndrome (ACS). Here, we present the case of a 52-year-old man presenting with chest pain and diagnosed with an NSTEMI but also found with a prolonged baseline aPTT ultimately secondary to FXII deficiency. Here, we discuss the diagnostic work-up of an isolated prolonged aPTT to identify possible etiologies, such as FXII deficiency, and ultimately inform ACS management.

New pharmacotherapeutic options for oral anticoagulant treatment in atrial fibrillation patients aged 65 and older: factor XIa inhibitors and beyond

INTRODUCTION

Although much progress has been made using anticoagulation for stroke prevention in patients with non-valvular atrial fibrillation, bleeding is still a major concern.

AREAS COVERED

This article reviews current pharmacotherapeutic options in this setting. Particular emphasis is placed on the ability of the new molecules to minimize the bleeding risk in elderly patients. A systematic search of PubMed, Web of Science, and the Cochrane Library up to March 2023 was carried out.

EXPERT OPINION

Contact phase of coagulation is a possible new target for anticoagulant therapy. Indeed, congenital or acquired deficiency of contact phase factors is associated with reduced thrombotic burden and limited risk of spontaneous bleeding. These new drugs seem particularly suitable for stroke prevention in elderly patients with non-valvular atrial fibrillation in whom the hemorrhagic risk is high. Most of anti Factor XI (FXI) drugs are for parenteral use only. A group of small molecules are for oral use and therefore are candidates to substitute direct oral anticoagulants (DOACs) for stroke prevention in elderly patients with atrial fibrillation. Doubts remain on the possibility of impaired hemostasis. Indeed, a fine calibration of inhibition of contact phase factors is crucial for an effective and safe treatment.

Factor XII Concentrations and Risk of Intracerebral Haemorrhage. A Prospective Case-Referent Study

OBJECTIVES

In a previous pilot study, we found an association between high factor XII levels and risk of haemorrhagic stroke suggesting that factor XII is a risk marker for intracerebral haemorrhage (ICH). The aim of this study was to further investigate the association between factor XII and risk of ICH in a larger population.

MATERIALS AND METHODS

This study was conducted as a prospective nested case-referent study. All participants underwent a health examination and blood sampling for factor XII analysis at baseline. Cases were defined as participants who were diagnosed with a first-ever ICH between 1985 and 2000. Two referents were matched to each case.

RESULTS

We identified 70 individuals with first-ever ICH and 137 matched referents who had undergone a health examination and donated blood samples before the ICH event. The mean age was 54 years, and 33% were women. The median time-to-event was 3.5 years (range 0.04 to 10.2 years). Conditional logistic regression showed no association between factor XII and risk of ICH, (odds ratio 1.06 per SD; [95% confidence interval: 0.57-1.97] in a multivariable model).

CONCLUSIONS

A previous finding of an association between high concentration of factor XII and risk of ICH could not be replicated in this larger study.

Endovenous Thermal Ablation for a Varicose Vein Patient with Factor XII Deficiency: A Case Report

Factor XII (FXII) deficiency is a rare coagulation disorder, and its potential relationship with venous thrombosis was reported. Here we present a case of a 67-year-old woman with FXII deficiency who successfully underwent endovenous thermal ablation (ETA) for primary varicose vein due to the incompetent great saphenous vein (GSV). The FXII deficiency was revealed through preoperative examinations, and the patient underwent ETA as a day surgery. For prophylaxis of thrombosis, she received compression therapy alone. Her postoperative course was uneventful, without any kind of thrombosis. In the presence of FXII deficiency, ETA could be safely performed.

A novel homozygous missense mutation (Met527Ile) in a consanguineous marriage family with inherited factor XII deficiency

OBJECTIVE

To identify potential mutations of the FXII gene (F12) in a consanguineous marriage family with hereditary coagulation factor XII (FXII) deficiency, and it will improve the understanding of the pathogenesis involved in the disease.

CLINICAL PRESENTATION

The proband was a 58-year-old male who had chronic gastritis. He was found to have a significantly prolonged activated partial thromboplastin time (APTT) at 101.0s (reference range, 29.0-43.0 s) before stomachendoscopy.

TECHNIQUES

The coagulation factor XII activity (FXII:C) and FXII antigen (FXII:Ag) were measured by one-stage clotting assay and enzyme-linked immunosorbent assay, respectively. The F12 gene was amplified by polymerase chain reaction and sequenced. Mutation sites were further confirmed by reverse sequencing. The conservatism and possible impact of the amino acid substitution were analyzed by multiple bioinformatics tools, as well as 3D protein model analysis.

RESULTS

The proband had a prolonged APTT (101.0 s), whose FXII:C and FXII:Ag were obviously reduced, both at 1.0% (normal range, 72-113%). Gene sequencing revealed that he carried a homozygous missense mutation of Met527Ile. Family study showed that his mother, son and daughter carried a heterozygous Met527Ile. Bioinformatics and model analysis of the mutation indicated that Met527Ile may be detrimental and potentially alters the structure and the function of the protein.

CONCLUSION

The novel mutation Met527Ile could potentially account for the reduced activity of FXII in this family.