Factor XI Inhibitors in Early Clinical Trials: A Meta-analysis

Therapeutic Potential of FXI Inhibitors: Hype or Hope?

Significant advancements have shaped the landscape of anticoagulant therapy in the past two decades, including the introduction of direct oral anticoagulants (DOACs), characterized by favorable safety and efficacy profiles and reduced drug-to-drug or food interaction resulting in excellent patient compliance. However, residual concerns still exist with standard-of-care anticoagulant therapy, including the inability to use DOACs in several clinical settings and the need to further reduce the risk of bleeding. Recent improvements in the understanding of the mechanisms behind thrombus formation have led to the awareness that the intrinsic pathway of the coagulation cascade may play an important role in pathological thrombosis, but not in hemostasis. This has represented the rationale for targeting this pathway with factor XI (FXI) inhibitors, with the aim of uncoupling hemostasis and thrombosis. Clinical evidence from patients with FXI deficiency further supports this concept. A number of compounds with different mechanisms of action have been developed to target FXI (i.e., asundexian, abelacimab, Ionis-FXIRx, milvexian, osocimab, and Xisomab 3G). To date, the majority of available trials have not gone beyond completion of phase 2 and results are conflictive making it difficult to appraise the clinical benefit of these compounds in the different clinical settings where they have been tested (i.e., atrial fibrillation, acute ischemic stroke, acute myocardial infarction, end-stage renal disease, total knee arthroplasty). Moreover, the largest phase 3 randomized trial designed to test the efficacy of asundexian over apixaban in patients with atrial fibrillation, the OCEANIC-AF, has been prematurely stopped as a result of the inferior efficacy of asundexian. In this review we discuss the pharmacological properties and available evidence generated thus far for factor XI inhibitors, providing a perspective on the current state of these drugs.

Advances in the medical treatment and diagnosis of intracranial hemorrhage associated with oral anticoagulation

INTRODUCTION

With the increasing prevalence of atrial fibrillation (AF), it entails expanding oral anticoagulants (OACs) use, carrying a higher risk of associated hemorrhagic events, including intracranial hemorrhage (ICH). Despite advances in OACs development with a better safety profile and reversal agent for these anticoagulants, there is still no consensus on the optimal management of patients with OACs-associated ICH.

AREAS COVERED

In this review, the authors have carried out an exhaustive search on the advances in recent years. The authors provide an update on the management of ICH in anticoagulated patients, as well as an update on the latest evidence on anticoagulation resumption, recent therapeutic strategies, and investigational drugs that could play a role in the future.

EXPERT OPINION

Following an ICH event in an anticoagulated patient, a comprehensive clinical evaluation is imperative. Anticoagulation should be promptly withdrawn and reversed. Once the patient is stabilized, a reintroduction of anticoagulation should be considered, typically within a timeframe of 4-8 weeks, if feasible. If re-anticoagulation is not possible, alternative options such as Left Atrial Appendage Occlusion are available.

Factor XI and coagulation. Factor XI inhibitors - antithrombotic perspectives

Factor XI is a zymogen with an important role in the coagulation cascade. It is activated by FXII, thrombin and or it can be autoactivated. It has a prothrombotic effect after being activated by thrombin, but also through its antifibrinolytic action, stabilizing the formed clot. Hereditary deficiency of FXI causes haemophilia C - a disease manifested by an usually provoked, small to moderate mucosal bleeding. People with severe FXI deficiency have a low risk of thrombotic events. Conversely, increased FXI values have been found to be associated with increased risk of venous thromboembolism and ischemic stroke. Lowering serum FXI levels has become a treatment target for the prevention of thrombotic events. New pharmacological agents - FXI inhibitors - have been investigated in phase II clinical trials, with promising results in terms of efficacy and safety in the prevention of thrombotic events. FXI inhibitors are emerging as new anticoagulant agents with broad indication prospects beyond direct oral anticoagulants and vitamin K antagonists.

Factor XI as a new target for prevention of thromboembolism in cardiovascular disease: a meta-analysis of randomized controlled trials

Anticoagulant therapy is a mainstay in the management of patients with cardiovascular disease. The use of conventional anticoagulants carries potential side effects, mainly bleeding. Drugs targeting Factor XI (FXI) have been investigated in randomized controlled trials as a new option with more favorable outcomes. A comprehensive literature search was conducted to identify relevant studies comparing FXI inhibitors to placebo or standard therapy. The primary outcomes were incidence of all bleeding events, major bleeding, and thromboembolism. Secondary outcomes included incidence of all adverse events (AE), serious AE, and all-cause mortality. A total of 11 studies involving 10,536 patients were included. FXI inhibitors were associated with a trend toward reduction of bleeding events and incidence of thromboembolism compared to the control group (placebo/standard therapy). There was no statistically significant difference between both groups in terms of adverse events and all-cause mortality. When compared to enoxaparin, FXI inhibitors significantly reduced the risk of bleeding events (RR = 0.42, 95% CI: 0.23-0.76, P = 0.004) and thromboembolism (RR = 0.59, 95% CI: 0.44-0.77, P = 0.001). On the other hand, when compared to DOACs, FXI inhibitors were associated with a significant reduction in bleeding events but not thromboembolism. Whereas, compared to placebo, FXI inhibitors did not increase the risk of bleeding events, adverse events, or all-cause mortality (P > 0.05). FXI inhibitors could be a safer and more potent option for prevention of thromboembolism than conventional therapy.

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.

Pharmacological and clinical appraisal of factor XI inhibitor drugs

The evolution of anticoagulation therapy, from vitamin K antagonists to the advent of direct oral anticoagulants (DOACs) almost two decades ago, marks significant progress. Despite improved safety demonstrated in pivotal trials and post-marketing observations, persistent concerns exist, particularly regarding bleeding risk and the absence of therapeutic indications in specific subgroups or clinical contexts. Factor XI (FXI) has recently emerged as a pivotal contributor to intraluminal thrombus formation and growth, playing a limited role in sealing vessel wall injuries. Inhibiting FXI presents an opportunity to decouple thrombosis from haemostasis, addressing concerns related to bleeding events while safeguarding against thromboembolic events. Notably, FXI inhibition holds promise for patients with end-stage renal disease or cancer, where clear indications for DOACs are currently lacking. Various compounds have undergone design, testing, and progression to phase 2 clinical trials, demonstrating a generally favourable safety and tolerability profile. However, validation through large-scale phase 3 trials with sufficient power to assess both safety and efficacy outcomes is needed. This review comprehensively examines FXI inhibitors, delving into individual classes, exploring their pharmacological properties, evaluating the latest evidence from randomized trials, and offering insights into future perspectives.

Longer and better lives for patients with atrial fibrillation: the 9th AFNET/EHRA consensus conference

AIMS

Recent trial data demonstrate beneficial effects of active rhythm management in patients with atrial fibrillation (AF) and support the concept that a low arrhythmia burden is associated with a low risk of AF-related complications. The aim of this document is to summarize the key outcomes of the 9th AFNET/EHRA Consensus Conference of the Atrial Fibrillation NETwork (AFNET) and the European Heart Rhythm Association (EHRA).

METHODS AND RESULTS

Eighty-three international experts met in Münster for 2 days in September 2023. Key findings are as follows: (i) Active rhythm management should be part of the default initial treatment for all suitable patients with AF. (ii) Patients with device-detected AF have a low burden of AF and a low risk of stroke. Anticoagulation prevents some strokes and also increases major but non-lethal bleeding. (iii) More research is needed to improve stroke risk prediction in patients with AF, especially in those with a low AF burden. Biomolecules, genetics, and imaging can support this. (iv) The presence of AF should trigger systematic workup and comprehensive treatment of concomitant cardiovascular conditions. (v) Machine learning algorithms have been used to improve detection or likely development of AF. Cooperation between clinicians and data scientists is needed to leverage the potential of data science applications for patients with AF.

CONCLUSIONS

Patients with AF and a low arrhythmia burden have a lower risk of stroke and other cardiovascular events than those with a high arrhythmia burden. Combining active rhythm control, anticoagulation, rate control, and therapy of concomitant cardiovascular conditions can improve the lives of patients with AF.

Cutting-Edge Techniques and Drugs for the Treatment of Pulmonary Embolism: Current Knowledge and Future Perspectives

Pulmonary embolism (PE) is a potentially life-threatening condition requiring prompt diagnosis and treatment. Recent advances have led to the development of newer techniques and drugs aimed at improving PE management, reducing its associated morbidity and mortality and the complications related to anticoagulation. This review provides an overview of the current knowledge and future perspectives on PE treatment. Anticoagulation represents the first-line treatment of hemodynamically stable PE, direct oral anticoagulants being a safe and effective alternative to traditional anticoagulation: these drugs have a rapid onset of action, predictable pharmacokinetics, and low bleeding risk. Systemic fibrinolysis is suggested in patients with cardiac arrest, refractory hypotension, or shock due to PE. With this narrative review, we aim to assess the state of the art of newer techniques and drugs that could radically improve PE management in the near future: (i) mechanical thrombectomy and pulmonary embolectomy are promising techniques reserved to patients with massive PE and contraindications or failure to systemic thrombolysis; (ii) catheter-directed thrombolysis is a minimally invasive approach that can be suggested for the treatment of massive or submassive PE, but the lack of large, randomized controlled trials represents a limitation to widespread use; (iii) novel pharmacological approaches, by agents inhibiting thrombin-activatable fibrinolysis inhibitor, factor Xia, and the complement cascade, are currently under investigation to improve PE-related outcomes in specific settings.

Systematic review of clinical trials on antithrombotic therapy with factor XI inhibitors

INTRODUCTION AND OBJECTIVE

Data from phase 2 clinical trials suggest that factor XI inhibitors may exhibit a more favorable efficacy/safety profile compared to current antithrombotic therapies. The aim of this systematic review is to analyze the available evidence derived from these studies.

METHODS

A literature search in the PubMed, Cochrane Library, Scopus, EMBASE databases, and clinical trial registration platforms Clinical Trials and Cochrane Central Register of Controlled was conducted. In accordance with the PRISMA statement, results were reported.

RESULTS

A total of 18 completed or ongoing clinical trials addressing multiple scenarios, including atrial fibrillation, stroke, myocardial infarction, and venous thromboembolism, were identified. Evidence from 8 studies with available results was analyzed. Phase 2 studies with factor XI inhibitors, overall, demonstrated an acceptable efficacy and safety profile. The benefit-risk balance, in terms of reducing venous thromboembolism in patients undergoing total knee arthroplasty, was more favorable. For this scenario, factor XI inhibitors showed a 50% reduction in the overall rate of thrombotic complications and a 60% reduction in the rate of bleeding compared to enoxaparin. Modest results in studies involving patients with atrial fibrillation, stroke, and myocardial infarction were observed.

CONCLUSIONS

Factor XI inhibitors offer new prospects in antithrombotic treatment and prophylaxis. Ongoing phase 3 studies will help define the most suitable drugs and indications.

Between a rock and a hard place: resumption of oral anticoagulant therapy after intracranial hemorrhage

Intracranial hemorrhage (ICH) is the most feared and lethal complication of oral anticoagulant (OAC) therapy. Resumption of OAC after ICH has long posed a challenge for clinicians, complicated by the expanding range of anticoagulant agents available in modern clinical practice, including direct OACs and, more recently, factor XI and XII inhibitors. A review of the current literature found support for resuming OAC in the majority of patients after ICH based on pooled retrospective data showing that resumption is associated with a lower risk of mortality and thromboembolism without a significantly increased risk of recurrent hemorrhage. The optimal time to resume OAC is less clear; however, the available evidence suggests that the composite risk of both recurrent hemorrhage and thromboembolism is likely minimized, somewhere between 4 and 6 weeks, after ICH in most patients. Specific considerations to guide the optimal resumption time in the individual patient include ICH location, mechanism, and anticoagulant class. Patients with mechanical heart valves and intracerebral malignancy represent high-risk groups who require more nuanced decision making. Here, we appraise the literature with the aim of providing a practical guide for clinicians while also discussing priorities for future investigation.

Superficial Venous Thrombosis: A Comprehensive Review

Superficial venous thrombosis (SVT), an inflammatory-thrombotic process of a superficial vein, is a relatively common event that may have several different underlying causes. This phenomenon has been generally considered benign, and its prevalence has been historically underestimated; the estimated incidence ranges from about 0.3 to 1.5 event per 1000 person-years, while the prevalence is approximately 3 to 11%, with different reports depending on the population studied. However, such pathology is not free of complications; indeed, it could extend to the deep circulation and embolize to pulmonary circulation. For this reason, an ultrasound examination is recommended to evaluate the extension of SVT and to exclude the involvement of deep circulation. Also, SVT may be costly, especially in the case of recurrence. Therefore, accurate management is necessary to prevent sequelae and costs related to the disease. This review aims to analyse the epidemiology of SVT, its complications, optimal medical treatment, and open questions with future perspectives.

New Therapeutic Targets for the Prevention and Treatment of Venous Thromboembolism With a Focus on Factor XI Inhibitors

FXI (factor XI) and FXII (factor XII) have emerged as targets for new anticoagulants that have the potential to be both more efficacious and safer than the currently available direct oral anticoagulants for the prevention and treatment of venous thromboembolism. In this review, we discuss the role of FXI and FXII in the pathogenesis of venous thromboembolism, explain why FXI is a better target, and explain why FXI inhibitors have potential advantages over currently available anticoagulants. Finally, we describe the FXI inhibitors under development and discuss their potential to address unmet needs in venous thromboembolism management.

Persistently High Levels of Coagulation Factor XI as a Risk Factor for Venous Thrombosis

Coagulation factor XI (FXI) promotes fibrin formation and inhibits fibrinolysis. Elevated plasma FXI levels, limited to a single measurement, are associated with a higher thrombotic risk. Our case-control study aimed to identify the effect of persistently increased plasma FXI levels on the risk of deep vein thrombosis (DVT). All patients evaluated between January 2016 and January 2018 for a first episode of proximal DVT of the lower extremity were considered for enrolment. Plasma FXI levels were measured at least 1 month after the discontinuation of anticoagulant treatment (T1). The patients with increased plasma FXI levels (>90th percentile of controls) were tested again 3 months later (T2). Among the 200 enrolled patients (M/F 114/86, age range 26-87 years), 47 patients had increased plasma FXI levels at T1 and16 patients had persistently increased plasma FXI levels at T2. The adjusted odds ratio for DVT was 2.4 (95% CI, 1.3 to 5.5, p < 0.001) for patients with increased FXI levels at T1 and 5.2 (95% CI, 2.3 to 13.2, p < 0.001) for patients with persistently high FXI levels at T2. Elevated FXI levels constitute a risk factor for deep vein thrombosis, and this risk nearly doubled in patients with persistently increased plasma FXI levels. Larger prospective studies are needed to confirm our findings.

Bleeding in acute coronary syndrome: from definitions, incidence, and prognosis to prevention and management

INTRODUCTION

In patients with acute coronary syndrome (ACS), the ischemic benefit of antithrombotic treatment is counterbalanced by the risk of bleeding. The recognition that bleeding events have prognostic implications (i.e. mortality) similar to recurrent ischemic events led to the development of treatment regimens aimed at balancing both ischemic and bleeding risks.

AREAS COVERED

This review aims at describing definitions, incidence, and prognosis related to bleeding events in ACS patients as well as bleeding-avoidance strategies for their prevention and management of bleeding complications.

EXPERT OPINION

Management of ACS patients has witnessed remarkable progress after the shift in focusing on the trade-off between ischemia and bleeding. Efforts in standardizing bleeding definitions will allow for better defining the prognostic impact of different types of bleeding events and enable to identify the high-bleeding risk patient. Such efforts will allow to balance the trade-off between the thrombotic and bleeding risk of the individual patient translating into better downward diagnostic and therapeutic decision-making. Novel strategies aiming at maximizing the safety and efficacy of antithrombotic regimens as well as the development of novel antithrombotic drugs and reversal agents and technological advances will allow for optimization of bleeding-avoidance strategies and management of bleeding complications.